1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2013 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{} 1988-2013 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) 1988-2013 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}:
895 You can further control how @value{GDBN} starts up by using command-line
896 options. @value{GDBN} itself can remind you of the options available.
906 to display all available options and briefly describe their use
907 (@samp{@value{GDBP} -h} is a shorter equivalent).
909 All options and command line arguments you give are processed
910 in sequential order. The order makes a difference when the
911 @samp{-x} option is used.
915 * File Options:: Choosing files
916 * Mode Options:: Choosing modes
917 * Startup:: What @value{GDBN} does during startup
921 @subsection Choosing Files
923 When @value{GDBN} starts, it reads any arguments other than options as
924 specifying an executable file and core file (or process ID). This is
925 the same as if the arguments were specified by the @samp{-se} and
926 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
927 first argument that does not have an associated option flag as
928 equivalent to the @samp{-se} option followed by that argument; and the
929 second argument that does not have an associated option flag, if any, as
930 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
931 If the second argument begins with a decimal digit, @value{GDBN} will
932 first attempt to attach to it as a process, and if that fails, attempt
933 to open it as a corefile. If you have a corefile whose name begins with
934 a digit, you can prevent @value{GDBN} from treating it as a pid by
935 prefixing it with @file{./}, e.g.@: @file{./12345}.
937 If @value{GDBN} has not been configured to included core file support,
938 such as for most embedded targets, then it will complain about a second
939 argument and ignore it.
941 Many options have both long and short forms; both are shown in the
942 following list. @value{GDBN} also recognizes the long forms if you truncate
943 them, so long as enough of the option is present to be unambiguous.
944 (If you prefer, you can flag option arguments with @samp{--} rather
945 than @samp{-}, though we illustrate the more usual convention.)
947 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
948 @c way, both those who look for -foo and --foo in the index, will find
952 @item -symbols @var{file}
954 @cindex @code{--symbols}
956 Read symbol table from file @var{file}.
958 @item -exec @var{file}
960 @cindex @code{--exec}
962 Use file @var{file} as the executable file to execute when appropriate,
963 and for examining pure data in conjunction with a core dump.
967 Read symbol table from file @var{file} and use it as the executable
970 @item -core @var{file}
972 @cindex @code{--core}
974 Use file @var{file} as a core dump to examine.
976 @item -pid @var{number}
977 @itemx -p @var{number}
980 Connect to process ID @var{number}, as with the @code{attach} command.
982 @item -command @var{file}
984 @cindex @code{--command}
986 Execute commands from file @var{file}. The contents of this file is
987 evaluated exactly as the @code{source} command would.
988 @xref{Command Files,, Command files}.
990 @item -eval-command @var{command}
991 @itemx -ex @var{command}
992 @cindex @code{--eval-command}
994 Execute a single @value{GDBN} command.
996 This option may be used multiple times to call multiple commands. It may
997 also be interleaved with @samp{-command} as required.
1000 @value{GDBP} -ex 'target sim' -ex 'load' \
1001 -x setbreakpoints -ex 'run' a.out
1004 @item -init-command @var{file}
1005 @itemx -ix @var{file}
1006 @cindex @code{--init-command}
1008 Execute commands from file @var{file} before loading the inferior (but
1009 after loading gdbinit files).
1012 @item -init-eval-command @var{command}
1013 @itemx -iex @var{command}
1014 @cindex @code{--init-eval-command}
1016 Execute a single @value{GDBN} command before loading the inferior (but
1017 after loading gdbinit files).
1020 @item -directory @var{directory}
1021 @itemx -d @var{directory}
1022 @cindex @code{--directory}
1024 Add @var{directory} to the path to search for source and script files.
1028 @cindex @code{--readnow}
1030 Read each symbol file's entire symbol table immediately, rather than
1031 the default, which is to read it incrementally as it is needed.
1032 This makes startup slower, but makes future operations faster.
1037 @subsection Choosing Modes
1039 You can run @value{GDBN} in various alternative modes---for example, in
1040 batch mode or quiet mode.
1048 Do not execute commands found in any initialization file.
1049 There are three init files, loaded in the following order:
1052 @item @file{system.gdbinit}
1053 This is the system-wide init file.
1054 Its location is specified with the @code{--with-system-gdbinit}
1055 configure option (@pxref{System-wide configuration}).
1056 It is loaded first when @value{GDBN} starts, before command line options
1057 have been processed.
1058 @item @file{~/.gdbinit}
1059 This is the init file in your home directory.
1060 It is loaded next, after @file{system.gdbinit}, and before
1061 command options have been processed.
1062 @item @file{./.gdbinit}
1063 This is the init file in the current directory.
1064 It is loaded last, after command line options other than @code{-x} and
1065 @code{-ex} have been processed. Command line options @code{-x} and
1066 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1069 For further documentation on startup processing, @xref{Startup}.
1070 For documentation on how to write command files,
1071 @xref{Command Files,,Command Files}.
1076 Do not execute commands found in @file{~/.gdbinit}, the init file
1077 in your home directory.
1083 @cindex @code{--quiet}
1084 @cindex @code{--silent}
1086 ``Quiet''. Do not print the introductory and copyright messages. These
1087 messages are also suppressed in batch mode.
1090 @cindex @code{--batch}
1091 Run in batch mode. Exit with status @code{0} after processing all the
1092 command files specified with @samp{-x} (and all commands from
1093 initialization files, if not inhibited with @samp{-n}). Exit with
1094 nonzero status if an error occurs in executing the @value{GDBN} commands
1095 in the command files. Batch mode also disables pagination, sets unlimited
1096 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1097 off} were in effect (@pxref{Messages/Warnings}).
1099 Batch mode may be useful for running @value{GDBN} as a filter, for
1100 example to download and run a program on another computer; in order to
1101 make this more useful, the message
1104 Program exited normally.
1108 (which is ordinarily issued whenever a program running under
1109 @value{GDBN} control terminates) is not issued when running in batch
1113 @cindex @code{--batch-silent}
1114 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1115 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1116 unaffected). This is much quieter than @samp{-silent} and would be useless
1117 for an interactive session.
1119 This is particularly useful when using targets that give @samp{Loading section}
1120 messages, for example.
1122 Note that targets that give their output via @value{GDBN}, as opposed to
1123 writing directly to @code{stdout}, will also be made silent.
1125 @item -return-child-result
1126 @cindex @code{--return-child-result}
1127 The return code from @value{GDBN} will be the return code from the child
1128 process (the process being debugged), with the following exceptions:
1132 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1133 internal error. In this case the exit code is the same as it would have been
1134 without @samp{-return-child-result}.
1136 The user quits with an explicit value. E.g., @samp{quit 1}.
1138 The child process never runs, or is not allowed to terminate, in which case
1139 the exit code will be -1.
1142 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1143 when @value{GDBN} is being used as a remote program loader or simulator
1148 @cindex @code{--nowindows}
1150 ``No windows''. If @value{GDBN} comes with a graphical user interface
1151 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1152 interface. If no GUI is available, this option has no effect.
1156 @cindex @code{--windows}
1158 If @value{GDBN} includes a GUI, then this option requires it to be
1161 @item -cd @var{directory}
1163 Run @value{GDBN} using @var{directory} as its working directory,
1164 instead of the current directory.
1166 @item -data-directory @var{directory}
1167 @cindex @code{--data-directory}
1168 Run @value{GDBN} using @var{directory} as its data directory.
1169 The data directory is where @value{GDBN} searches for its
1170 auxiliary files. @xref{Data Files}.
1174 @cindex @code{--fullname}
1176 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1177 subprocess. It tells @value{GDBN} to output the full file name and line
1178 number in a standard, recognizable fashion each time a stack frame is
1179 displayed (which includes each time your program stops). This
1180 recognizable format looks like two @samp{\032} characters, followed by
1181 the file name, line number and character position separated by colons,
1182 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1183 @samp{\032} characters as a signal to display the source code for the
1186 @item -annotate @var{level}
1187 @cindex @code{--annotate}
1188 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1189 effect is identical to using @samp{set annotate @var{level}}
1190 (@pxref{Annotations}). The annotation @var{level} controls how much
1191 information @value{GDBN} prints together with its prompt, values of
1192 expressions, source lines, and other types of output. Level 0 is the
1193 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1194 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1195 that control @value{GDBN}, and level 2 has been deprecated.
1197 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1201 @cindex @code{--args}
1202 Change interpretation of command line so that arguments following the
1203 executable file are passed as command line arguments to the inferior.
1204 This option stops option processing.
1206 @item -baud @var{bps}
1208 @cindex @code{--baud}
1210 Set the line speed (baud rate or bits per second) of any serial
1211 interface used by @value{GDBN} for remote debugging.
1213 @item -l @var{timeout}
1215 Set the timeout (in seconds) of any communication used by @value{GDBN}
1216 for remote debugging.
1218 @item -tty @var{device}
1219 @itemx -t @var{device}
1220 @cindex @code{--tty}
1222 Run using @var{device} for your program's standard input and output.
1223 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1225 @c resolve the situation of these eventually
1227 @cindex @code{--tui}
1228 Activate the @dfn{Text User Interface} when starting. The Text User
1229 Interface manages several text windows on the terminal, showing
1230 source, assembly, registers and @value{GDBN} command outputs
1231 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1232 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1233 Using @value{GDBN} under @sc{gnu} Emacs}).
1236 @c @cindex @code{--xdb}
1237 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1238 @c For information, see the file @file{xdb_trans.html}, which is usually
1239 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1242 @item -interpreter @var{interp}
1243 @cindex @code{--interpreter}
1244 Use the interpreter @var{interp} for interface with the controlling
1245 program or device. This option is meant to be set by programs which
1246 communicate with @value{GDBN} using it as a back end.
1247 @xref{Interpreters, , Command Interpreters}.
1249 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1250 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1251 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1252 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1253 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1254 @sc{gdb/mi} interfaces are no longer supported.
1257 @cindex @code{--write}
1258 Open the executable and core files for both reading and writing. This
1259 is equivalent to the @samp{set write on} command inside @value{GDBN}
1263 @cindex @code{--statistics}
1264 This option causes @value{GDBN} to print statistics about time and
1265 memory usage after it completes each command and returns to the prompt.
1268 @cindex @code{--version}
1269 This option causes @value{GDBN} to print its version number and
1270 no-warranty blurb, and exit.
1272 @item -configuration
1273 @cindex @code{--configuration}
1274 This option causes @value{GDBN} to print details about its build-time
1275 configuration parameters, and then exit. These details can be
1276 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1281 @subsection What @value{GDBN} Does During Startup
1282 @cindex @value{GDBN} startup
1284 Here's the description of what @value{GDBN} does during session startup:
1288 Sets up the command interpreter as specified by the command line
1289 (@pxref{Mode Options, interpreter}).
1293 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1294 used when building @value{GDBN}; @pxref{System-wide configuration,
1295 ,System-wide configuration and settings}) and executes all the commands in
1298 @anchor{Home Directory Init File}
1300 Reads the init file (if any) in your home directory@footnote{On
1301 DOS/Windows systems, the home directory is the one pointed to by the
1302 @code{HOME} environment variable.} and executes all the commands in
1305 @anchor{Option -init-eval-command}
1307 Executes commands and command files specified by the @samp{-iex} and
1308 @samp{-ix} options in their specified order. Usually you should use the
1309 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1310 settings before @value{GDBN} init files get executed and before inferior
1314 Processes command line options and operands.
1316 @anchor{Init File in the Current Directory during Startup}
1318 Reads and executes the commands from init file (if any) in the current
1319 working directory as long as @samp{set auto-load local-gdbinit} is set to
1320 @samp{on} (@pxref{Init File in the Current Directory}).
1321 This is only done if the current directory is
1322 different from your home directory. Thus, you can have more than one
1323 init file, one generic in your home directory, and another, specific
1324 to the program you are debugging, in the directory where you invoke
1328 If the command line specified a program to debug, or a process to
1329 attach to, or a core file, @value{GDBN} loads any auto-loaded
1330 scripts provided for the program or for its loaded shared libraries.
1331 @xref{Auto-loading}.
1333 If you wish to disable the auto-loading during startup,
1334 you must do something like the following:
1337 $ gdb -iex "set auto-load python-scripts off" myprogram
1340 Option @samp{-ex} does not work because the auto-loading is then turned
1344 Executes commands and command files specified by the @samp{-ex} and
1345 @samp{-x} options in their specified order. @xref{Command Files}, for
1346 more details about @value{GDBN} command files.
1349 Reads the command history recorded in the @dfn{history file}.
1350 @xref{Command History}, for more details about the command history and the
1351 files where @value{GDBN} records it.
1354 Init files use the same syntax as @dfn{command files} (@pxref{Command
1355 Files}) and are processed by @value{GDBN} in the same way. The init
1356 file in your home directory can set options (such as @samp{set
1357 complaints}) that affect subsequent processing of command line options
1358 and operands. Init files are not executed if you use the @samp{-nx}
1359 option (@pxref{Mode Options, ,Choosing Modes}).
1361 To display the list of init files loaded by gdb at startup, you
1362 can use @kbd{gdb --help}.
1364 @cindex init file name
1365 @cindex @file{.gdbinit}
1366 @cindex @file{gdb.ini}
1367 The @value{GDBN} init files are normally called @file{.gdbinit}.
1368 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1369 the limitations of file names imposed by DOS filesystems. The Windows
1370 port of @value{GDBN} uses the standard name, but if it finds a
1371 @file{gdb.ini} file in your home directory, it warns you about that
1372 and suggests to rename the file to the standard name.
1376 @section Quitting @value{GDBN}
1377 @cindex exiting @value{GDBN}
1378 @cindex leaving @value{GDBN}
1381 @kindex quit @r{[}@var{expression}@r{]}
1382 @kindex q @r{(@code{quit})}
1383 @item quit @r{[}@var{expression}@r{]}
1385 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1386 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1387 do not supply @var{expression}, @value{GDBN} will terminate normally;
1388 otherwise it will terminate using the result of @var{expression} as the
1393 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1394 terminates the action of any @value{GDBN} command that is in progress and
1395 returns to @value{GDBN} command level. It is safe to type the interrupt
1396 character at any time because @value{GDBN} does not allow it to take effect
1397 until a time when it is safe.
1399 If you have been using @value{GDBN} to control an attached process or
1400 device, you can release it with the @code{detach} command
1401 (@pxref{Attach, ,Debugging an Already-running Process}).
1403 @node Shell Commands
1404 @section Shell Commands
1406 If you need to execute occasional shell commands during your
1407 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1408 just use the @code{shell} command.
1413 @cindex shell escape
1414 @item shell @var{command-string}
1415 @itemx !@var{command-string}
1416 Invoke a standard shell to execute @var{command-string}.
1417 Note that no space is needed between @code{!} and @var{command-string}.
1418 If it exists, the environment variable @code{SHELL} determines which
1419 shell to run. Otherwise @value{GDBN} uses the default shell
1420 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1423 The utility @code{make} is often needed in development environments.
1424 You do not have to use the @code{shell} command for this purpose in
1429 @cindex calling make
1430 @item make @var{make-args}
1431 Execute the @code{make} program with the specified
1432 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1435 @node Logging Output
1436 @section Logging Output
1437 @cindex logging @value{GDBN} output
1438 @cindex save @value{GDBN} output to a file
1440 You may want to save the output of @value{GDBN} commands to a file.
1441 There are several commands to control @value{GDBN}'s logging.
1445 @item set logging on
1447 @item set logging off
1449 @cindex logging file name
1450 @item set logging file @var{file}
1451 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1452 @item set logging overwrite [on|off]
1453 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1454 you want @code{set logging on} to overwrite the logfile instead.
1455 @item set logging redirect [on|off]
1456 By default, @value{GDBN} output will go to both the terminal and the logfile.
1457 Set @code{redirect} if you want output to go only to the log file.
1458 @kindex show logging
1460 Show the current values of the logging settings.
1464 @chapter @value{GDBN} Commands
1466 You can abbreviate a @value{GDBN} command to the first few letters of the command
1467 name, if that abbreviation is unambiguous; and you can repeat certain
1468 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1469 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1470 show you the alternatives available, if there is more than one possibility).
1473 * Command Syntax:: How to give commands to @value{GDBN}
1474 * Completion:: Command completion
1475 * Help:: How to ask @value{GDBN} for help
1478 @node Command Syntax
1479 @section Command Syntax
1481 A @value{GDBN} command is a single line of input. There is no limit on
1482 how long it can be. It starts with a command name, which is followed by
1483 arguments whose meaning depends on the command name. For example, the
1484 command @code{step} accepts an argument which is the number of times to
1485 step, as in @samp{step 5}. You can also use the @code{step} command
1486 with no arguments. Some commands do not allow any arguments.
1488 @cindex abbreviation
1489 @value{GDBN} command names may always be truncated if that abbreviation is
1490 unambiguous. Other possible command abbreviations are listed in the
1491 documentation for individual commands. In some cases, even ambiguous
1492 abbreviations are allowed; for example, @code{s} is specially defined as
1493 equivalent to @code{step} even though there are other commands whose
1494 names start with @code{s}. You can test abbreviations by using them as
1495 arguments to the @code{help} command.
1497 @cindex repeating commands
1498 @kindex RET @r{(repeat last command)}
1499 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1500 repeat the previous command. Certain commands (for example, @code{run})
1501 will not repeat this way; these are commands whose unintentional
1502 repetition might cause trouble and which you are unlikely to want to
1503 repeat. User-defined commands can disable this feature; see
1504 @ref{Define, dont-repeat}.
1506 The @code{list} and @code{x} commands, when you repeat them with
1507 @key{RET}, construct new arguments rather than repeating
1508 exactly as typed. This permits easy scanning of source or memory.
1510 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1511 output, in a way similar to the common utility @code{more}
1512 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1513 @key{RET} too many in this situation, @value{GDBN} disables command
1514 repetition after any command that generates this sort of display.
1516 @kindex # @r{(a comment)}
1518 Any text from a @kbd{#} to the end of the line is a comment; it does
1519 nothing. This is useful mainly in command files (@pxref{Command
1520 Files,,Command Files}).
1522 @cindex repeating command sequences
1523 @kindex Ctrl-o @r{(operate-and-get-next)}
1524 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1525 commands. This command accepts the current line, like @key{RET}, and
1526 then fetches the next line relative to the current line from the history
1530 @section Command Completion
1533 @cindex word completion
1534 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1535 only one possibility; it can also show you what the valid possibilities
1536 are for the next word in a command, at any time. This works for @value{GDBN}
1537 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1539 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1540 of a word. If there is only one possibility, @value{GDBN} fills in the
1541 word, and waits for you to finish the command (or press @key{RET} to
1542 enter it). For example, if you type
1544 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1545 @c complete accuracy in these examples; space introduced for clarity.
1546 @c If texinfo enhancements make it unnecessary, it would be nice to
1547 @c replace " @key" by "@key" in the following...
1549 (@value{GDBP}) info bre @key{TAB}
1553 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1554 the only @code{info} subcommand beginning with @samp{bre}:
1557 (@value{GDBP}) info breakpoints
1561 You can either press @key{RET} at this point, to run the @code{info
1562 breakpoints} command, or backspace and enter something else, if
1563 @samp{breakpoints} does not look like the command you expected. (If you
1564 were sure you wanted @code{info breakpoints} in the first place, you
1565 might as well just type @key{RET} immediately after @samp{info bre},
1566 to exploit command abbreviations rather than command completion).
1568 If there is more than one possibility for the next word when you press
1569 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1570 characters and try again, or just press @key{TAB} a second time;
1571 @value{GDBN} displays all the possible completions for that word. For
1572 example, you might want to set a breakpoint on a subroutine whose name
1573 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1574 just sounds the bell. Typing @key{TAB} again displays all the
1575 function names in your program that begin with those characters, for
1579 (@value{GDBP}) b make_ @key{TAB}
1580 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1581 make_a_section_from_file make_environ
1582 make_abs_section make_function_type
1583 make_blockvector make_pointer_type
1584 make_cleanup make_reference_type
1585 make_command make_symbol_completion_list
1586 (@value{GDBP}) b make_
1590 After displaying the available possibilities, @value{GDBN} copies your
1591 partial input (@samp{b make_} in the example) so you can finish the
1594 If you just want to see the list of alternatives in the first place, you
1595 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1596 means @kbd{@key{META} ?}. You can type this either by holding down a
1597 key designated as the @key{META} shift on your keyboard (if there is
1598 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1600 @cindex quotes in commands
1601 @cindex completion of quoted strings
1602 Sometimes the string you need, while logically a ``word'', may contain
1603 parentheses or other characters that @value{GDBN} normally excludes from
1604 its notion of a word. To permit word completion to work in this
1605 situation, you may enclose words in @code{'} (single quote marks) in
1606 @value{GDBN} commands.
1608 The most likely situation where you might need this is in typing the
1609 name of a C@t{++} function. This is because C@t{++} allows function
1610 overloading (multiple definitions of the same function, distinguished
1611 by argument type). For example, when you want to set a breakpoint you
1612 may need to distinguish whether you mean the version of @code{name}
1613 that takes an @code{int} parameter, @code{name(int)}, or the version
1614 that takes a @code{float} parameter, @code{name(float)}. To use the
1615 word-completion facilities in this situation, type a single quote
1616 @code{'} at the beginning of the function name. This alerts
1617 @value{GDBN} that it may need to consider more information than usual
1618 when you press @key{TAB} or @kbd{M-?} to request word completion:
1621 (@value{GDBP}) b 'bubble( @kbd{M-?}
1622 bubble(double,double) bubble(int,int)
1623 (@value{GDBP}) b 'bubble(
1626 In some cases, @value{GDBN} can tell that completing a name requires using
1627 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1628 completing as much as it can) if you do not type the quote in the first
1632 (@value{GDBP}) b bub @key{TAB}
1633 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1634 (@value{GDBP}) b 'bubble(
1638 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1639 you have not yet started typing the argument list when you ask for
1640 completion on an overloaded symbol.
1642 For more information about overloaded functions, see @ref{C Plus Plus
1643 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1644 overload-resolution off} to disable overload resolution;
1645 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1647 @cindex completion of structure field names
1648 @cindex structure field name completion
1649 @cindex completion of union field names
1650 @cindex union field name completion
1651 When completing in an expression which looks up a field in a
1652 structure, @value{GDBN} also tries@footnote{The completer can be
1653 confused by certain kinds of invalid expressions. Also, it only
1654 examines the static type of the expression, not the dynamic type.} to
1655 limit completions to the field names available in the type of the
1659 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1660 magic to_fputs to_rewind
1661 to_data to_isatty to_write
1662 to_delete to_put to_write_async_safe
1667 This is because the @code{gdb_stdout} is a variable of the type
1668 @code{struct ui_file} that is defined in @value{GDBN} sources as
1675 ui_file_flush_ftype *to_flush;
1676 ui_file_write_ftype *to_write;
1677 ui_file_write_async_safe_ftype *to_write_async_safe;
1678 ui_file_fputs_ftype *to_fputs;
1679 ui_file_read_ftype *to_read;
1680 ui_file_delete_ftype *to_delete;
1681 ui_file_isatty_ftype *to_isatty;
1682 ui_file_rewind_ftype *to_rewind;
1683 ui_file_put_ftype *to_put;
1690 @section Getting Help
1691 @cindex online documentation
1694 You can always ask @value{GDBN} itself for information on its commands,
1695 using the command @code{help}.
1698 @kindex h @r{(@code{help})}
1701 You can use @code{help} (abbreviated @code{h}) with no arguments to
1702 display a short list of named classes of commands:
1706 List of classes of commands:
1708 aliases -- Aliases of other commands
1709 breakpoints -- Making program stop at certain points
1710 data -- Examining data
1711 files -- Specifying and examining files
1712 internals -- Maintenance commands
1713 obscure -- Obscure features
1714 running -- Running the program
1715 stack -- Examining the stack
1716 status -- Status inquiries
1717 support -- Support facilities
1718 tracepoints -- Tracing of program execution without
1719 stopping the program
1720 user-defined -- User-defined commands
1722 Type "help" followed by a class name for a list of
1723 commands in that class.
1724 Type "help" followed by command name for full
1726 Command name abbreviations are allowed if unambiguous.
1729 @c the above line break eliminates huge line overfull...
1731 @item help @var{class}
1732 Using one of the general help classes as an argument, you can get a
1733 list of the individual commands in that class. For example, here is the
1734 help display for the class @code{status}:
1737 (@value{GDBP}) help status
1742 @c Line break in "show" line falsifies real output, but needed
1743 @c to fit in smallbook page size.
1744 info -- Generic command for showing things
1745 about the program being debugged
1746 show -- Generic command for showing things
1749 Type "help" followed by command name for full
1751 Command name abbreviations are allowed if unambiguous.
1755 @item help @var{command}
1756 With a command name as @code{help} argument, @value{GDBN} displays a
1757 short paragraph on how to use that command.
1760 @item apropos @var{args}
1761 The @code{apropos} command searches through all of the @value{GDBN}
1762 commands, and their documentation, for the regular expression specified in
1763 @var{args}. It prints out all matches found. For example:
1774 alias -- Define a new command that is an alias of an existing command
1775 aliases -- Aliases of other commands
1776 d -- Delete some breakpoints or auto-display expressions
1777 del -- Delete some breakpoints or auto-display expressions
1778 delete -- Delete some breakpoints or auto-display expressions
1783 @item complete @var{args}
1784 The @code{complete @var{args}} command lists all the possible completions
1785 for the beginning of a command. Use @var{args} to specify the beginning of the
1786 command you want completed. For example:
1792 @noindent results in:
1803 @noindent This is intended for use by @sc{gnu} Emacs.
1806 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1807 and @code{show} to inquire about the state of your program, or the state
1808 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1809 manual introduces each of them in the appropriate context. The listings
1810 under @code{info} and under @code{show} in the Command, Variable, and
1811 Function Index point to all the sub-commands. @xref{Command and Variable
1817 @kindex i @r{(@code{info})}
1819 This command (abbreviated @code{i}) is for describing the state of your
1820 program. For example, you can show the arguments passed to a function
1821 with @code{info args}, list the registers currently in use with @code{info
1822 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1823 You can get a complete list of the @code{info} sub-commands with
1824 @w{@code{help info}}.
1828 You can assign the result of an expression to an environment variable with
1829 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1830 @code{set prompt $}.
1834 In contrast to @code{info}, @code{show} is for describing the state of
1835 @value{GDBN} itself.
1836 You can change most of the things you can @code{show}, by using the
1837 related command @code{set}; for example, you can control what number
1838 system is used for displays with @code{set radix}, or simply inquire
1839 which is currently in use with @code{show radix}.
1842 To display all the settable parameters and their current
1843 values, you can use @code{show} with no arguments; you may also use
1844 @code{info set}. Both commands produce the same display.
1845 @c FIXME: "info set" violates the rule that "info" is for state of
1846 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1847 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1851 Here are several miscellaneous @code{show} subcommands, all of which are
1852 exceptional in lacking corresponding @code{set} commands:
1855 @kindex show version
1856 @cindex @value{GDBN} version number
1858 Show what version of @value{GDBN} is running. You should include this
1859 information in @value{GDBN} bug-reports. If multiple versions of
1860 @value{GDBN} are in use at your site, you may need to determine which
1861 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1862 commands are introduced, and old ones may wither away. Also, many
1863 system vendors ship variant versions of @value{GDBN}, and there are
1864 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1865 The version number is the same as the one announced when you start
1868 @kindex show copying
1869 @kindex info copying
1870 @cindex display @value{GDBN} copyright
1873 Display information about permission for copying @value{GDBN}.
1875 @kindex show warranty
1876 @kindex info warranty
1878 @itemx info warranty
1879 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1880 if your version of @value{GDBN} comes with one.
1882 @kindex show configuration
1883 @item show configuration
1884 Display detailed information about the way @value{GDBN} was configured
1885 when it was built. This displays the optional arguments passed to the
1886 @file{configure} script and also configuration parameters detected
1887 automatically by @command{configure}. When reporting a @value{GDBN}
1888 bug (@pxref{GDB Bugs}), it is important to include this information in
1894 @chapter Running Programs Under @value{GDBN}
1896 When you run a program under @value{GDBN}, you must first generate
1897 debugging information when you compile it.
1899 You may start @value{GDBN} with its arguments, if any, in an environment
1900 of your choice. If you are doing native debugging, you may redirect
1901 your program's input and output, debug an already running process, or
1902 kill a child process.
1905 * Compilation:: Compiling for debugging
1906 * Starting:: Starting your program
1907 * Arguments:: Your program's arguments
1908 * Environment:: Your program's environment
1910 * Working Directory:: Your program's working directory
1911 * Input/Output:: Your program's input and output
1912 * Attach:: Debugging an already-running process
1913 * Kill Process:: Killing the child process
1915 * Inferiors and Programs:: Debugging multiple inferiors and programs
1916 * Threads:: Debugging programs with multiple threads
1917 * Forks:: Debugging forks
1918 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1922 @section Compiling for Debugging
1924 In order to debug a program effectively, you need to generate
1925 debugging information when you compile it. This debugging information
1926 is stored in the object file; it describes the data type of each
1927 variable or function and the correspondence between source line numbers
1928 and addresses in the executable code.
1930 To request debugging information, specify the @samp{-g} option when you run
1933 Programs that are to be shipped to your customers are compiled with
1934 optimizations, using the @samp{-O} compiler option. However, some
1935 compilers are unable to handle the @samp{-g} and @samp{-O} options
1936 together. Using those compilers, you cannot generate optimized
1937 executables containing debugging information.
1939 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1940 without @samp{-O}, making it possible to debug optimized code. We
1941 recommend that you @emph{always} use @samp{-g} whenever you compile a
1942 program. You may think your program is correct, but there is no sense
1943 in pushing your luck. For more information, see @ref{Optimized Code}.
1945 Older versions of the @sc{gnu} C compiler permitted a variant option
1946 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1947 format; if your @sc{gnu} C compiler has this option, do not use it.
1949 @value{GDBN} knows about preprocessor macros and can show you their
1950 expansion (@pxref{Macros}). Most compilers do not include information
1951 about preprocessor macros in the debugging information if you specify
1952 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1953 the @sc{gnu} C compiler, provides macro information if you are using
1954 the DWARF debugging format, and specify the option @option{-g3}.
1956 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1957 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1958 information on @value{NGCC} options affecting debug information.
1960 You will have the best debugging experience if you use the latest
1961 version of the DWARF debugging format that your compiler supports.
1962 DWARF is currently the most expressive and best supported debugging
1963 format in @value{GDBN}.
1967 @section Starting your Program
1973 @kindex r @r{(@code{run})}
1976 Use the @code{run} command to start your program under @value{GDBN}.
1977 You must first specify the program name (except on VxWorks) with an
1978 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1979 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1980 (@pxref{Files, ,Commands to Specify Files}).
1984 If you are running your program in an execution environment that
1985 supports processes, @code{run} creates an inferior process and makes
1986 that process run your program. In some environments without processes,
1987 @code{run} jumps to the start of your program. Other targets,
1988 like @samp{remote}, are always running. If you get an error
1989 message like this one:
1992 The "remote" target does not support "run".
1993 Try "help target" or "continue".
1997 then use @code{continue} to run your program. You may need @code{load}
1998 first (@pxref{load}).
2000 The execution of a program is affected by certain information it
2001 receives from its superior. @value{GDBN} provides ways to specify this
2002 information, which you must do @emph{before} starting your program. (You
2003 can change it after starting your program, but such changes only affect
2004 your program the next time you start it.) This information may be
2005 divided into four categories:
2008 @item The @emph{arguments.}
2009 Specify the arguments to give your program as the arguments of the
2010 @code{run} command. If a shell is available on your target, the shell
2011 is used to pass the arguments, so that you may use normal conventions
2012 (such as wildcard expansion or variable substitution) in describing
2014 In Unix systems, you can control which shell is used with the
2015 @code{SHELL} environment variable. If you do not define @code{SHELL},
2016 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2017 use of any shell with the @code{set startup-with-shell} command (see
2020 @item The @emph{environment.}
2021 Your program normally inherits its environment from @value{GDBN}, but you can
2022 use the @value{GDBN} commands @code{set environment} and @code{unset
2023 environment} to change parts of the environment that affect
2024 your program. @xref{Environment, ,Your Program's Environment}.
2026 @item The @emph{working directory.}
2027 Your program inherits its working directory from @value{GDBN}. You can set
2028 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2029 @xref{Working Directory, ,Your Program's Working Directory}.
2031 @item The @emph{standard input and output.}
2032 Your program normally uses the same device for standard input and
2033 standard output as @value{GDBN} is using. You can redirect input and output
2034 in the @code{run} command line, or you can use the @code{tty} command to
2035 set a different device for your program.
2036 @xref{Input/Output, ,Your Program's Input and Output}.
2039 @emph{Warning:} While input and output redirection work, you cannot use
2040 pipes to pass the output of the program you are debugging to another
2041 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2045 When you issue the @code{run} command, your program begins to execute
2046 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2047 of how to arrange for your program to stop. Once your program has
2048 stopped, you may call functions in your program, using the @code{print}
2049 or @code{call} commands. @xref{Data, ,Examining Data}.
2051 If the modification time of your symbol file has changed since the last
2052 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2053 table, and reads it again. When it does this, @value{GDBN} tries to retain
2054 your current breakpoints.
2059 @cindex run to main procedure
2060 The name of the main procedure can vary from language to language.
2061 With C or C@t{++}, the main procedure name is always @code{main}, but
2062 other languages such as Ada do not require a specific name for their
2063 main procedure. The debugger provides a convenient way to start the
2064 execution of the program and to stop at the beginning of the main
2065 procedure, depending on the language used.
2067 The @samp{start} command does the equivalent of setting a temporary
2068 breakpoint at the beginning of the main procedure and then invoking
2069 the @samp{run} command.
2071 @cindex elaboration phase
2072 Some programs contain an @dfn{elaboration} phase where some startup code is
2073 executed before the main procedure is called. This depends on the
2074 languages used to write your program. In C@t{++}, for instance,
2075 constructors for static and global objects are executed before
2076 @code{main} is called. It is therefore possible that the debugger stops
2077 before reaching the main procedure. However, the temporary breakpoint
2078 will remain to halt execution.
2080 Specify the arguments to give to your program as arguments to the
2081 @samp{start} command. These arguments will be given verbatim to the
2082 underlying @samp{run} command. Note that the same arguments will be
2083 reused if no argument is provided during subsequent calls to
2084 @samp{start} or @samp{run}.
2086 It is sometimes necessary to debug the program during elaboration. In
2087 these cases, using the @code{start} command would stop the execution of
2088 your program too late, as the program would have already completed the
2089 elaboration phase. Under these circumstances, insert breakpoints in your
2090 elaboration code before running your program.
2092 @kindex set exec-wrapper
2093 @item set exec-wrapper @var{wrapper}
2094 @itemx show exec-wrapper
2095 @itemx unset exec-wrapper
2096 When @samp{exec-wrapper} is set, the specified wrapper is used to
2097 launch programs for debugging. @value{GDBN} starts your program
2098 with a shell command of the form @kbd{exec @var{wrapper}
2099 @var{program}}. Quoting is added to @var{program} and its
2100 arguments, but not to @var{wrapper}, so you should add quotes if
2101 appropriate for your shell. The wrapper runs until it executes
2102 your program, and then @value{GDBN} takes control.
2104 You can use any program that eventually calls @code{execve} with
2105 its arguments as a wrapper. Several standard Unix utilities do
2106 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2107 with @code{exec "$@@"} will also work.
2109 For example, you can use @code{env} to pass an environment variable to
2110 the debugged program, without setting the variable in your shell's
2114 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2118 This command is available when debugging locally on most targets, excluding
2119 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2121 @kindex set startup-with-shell
2122 @item set startup-with-shell
2123 @itemx set startup-with-shell on
2124 @itemx set startup-with-shell off
2125 @itemx show set startup-with-shell
2126 On Unix systems, by default, if a shell is available on your target,
2127 @value{GDBN}) uses it to start your program. Arguments of the
2128 @code{run} command are passed to the shell, which does variable
2129 substitution, expands wildcard characters and performs redirection of
2130 I/O. In some circumstances, it may be useful to disable such use of a
2131 shell, for example, when debugging the shell itself or diagnosing
2132 startup failures such as:
2136 Starting program: ./a.out
2137 During startup program terminated with signal SIGSEGV, Segmentation fault.
2141 which indicates the shell or the wrapper specified with
2142 @samp{exec-wrapper} crashed, not your program. Most often, this is
2143 caused by something odd in your shell's non-interactive mode
2144 initialization file---such as @file{.cshrc} for C-shell,
2145 $@file{.zshenv} for the Z shell, or the file specified in the
2146 @samp{BASH_ENV} environment variable for BASH.
2148 @kindex set disable-randomization
2149 @item set disable-randomization
2150 @itemx set disable-randomization on
2151 This option (enabled by default in @value{GDBN}) will turn off the native
2152 randomization of the virtual address space of the started program. This option
2153 is useful for multiple debugging sessions to make the execution better
2154 reproducible and memory addresses reusable across debugging sessions.
2156 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2157 On @sc{gnu}/Linux you can get the same behavior using
2160 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2163 @item set disable-randomization off
2164 Leave the behavior of the started executable unchanged. Some bugs rear their
2165 ugly heads only when the program is loaded at certain addresses. If your bug
2166 disappears when you run the program under @value{GDBN}, that might be because
2167 @value{GDBN} by default disables the address randomization on platforms, such
2168 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2169 disable-randomization off} to try to reproduce such elusive bugs.
2171 On targets where it is available, virtual address space randomization
2172 protects the programs against certain kinds of security attacks. In these
2173 cases the attacker needs to know the exact location of a concrete executable
2174 code. Randomizing its location makes it impossible to inject jumps misusing
2175 a code at its expected addresses.
2177 Prelinking shared libraries provides a startup performance advantage but it
2178 makes addresses in these libraries predictable for privileged processes by
2179 having just unprivileged access at the target system. Reading the shared
2180 library binary gives enough information for assembling the malicious code
2181 misusing it. Still even a prelinked shared library can get loaded at a new
2182 random address just requiring the regular relocation process during the
2183 startup. Shared libraries not already prelinked are always loaded at
2184 a randomly chosen address.
2186 Position independent executables (PIE) contain position independent code
2187 similar to the shared libraries and therefore such executables get loaded at
2188 a randomly chosen address upon startup. PIE executables always load even
2189 already prelinked shared libraries at a random address. You can build such
2190 executable using @command{gcc -fPIE -pie}.
2192 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2193 (as long as the randomization is enabled).
2195 @item show disable-randomization
2196 Show the current setting of the explicit disable of the native randomization of
2197 the virtual address space of the started program.
2202 @section Your Program's Arguments
2204 @cindex arguments (to your program)
2205 The arguments to your program can be specified by the arguments of the
2207 They are passed to a shell, which expands wildcard characters and
2208 performs redirection of I/O, and thence to your program. Your
2209 @code{SHELL} environment variable (if it exists) specifies what shell
2210 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2211 the default shell (@file{/bin/sh} on Unix).
2213 On non-Unix systems, the program is usually invoked directly by
2214 @value{GDBN}, which emulates I/O redirection via the appropriate system
2215 calls, and the wildcard characters are expanded by the startup code of
2216 the program, not by the shell.
2218 @code{run} with no arguments uses the same arguments used by the previous
2219 @code{run}, or those set by the @code{set args} command.
2224 Specify the arguments to be used the next time your program is run. If
2225 @code{set args} has no arguments, @code{run} executes your program
2226 with no arguments. Once you have run your program with arguments,
2227 using @code{set args} before the next @code{run} is the only way to run
2228 it again without arguments.
2232 Show the arguments to give your program when it is started.
2236 @section Your Program's Environment
2238 @cindex environment (of your program)
2239 The @dfn{environment} consists of a set of environment variables and
2240 their values. Environment variables conventionally record such things as
2241 your user name, your home directory, your terminal type, and your search
2242 path for programs to run. Usually you set up environment variables with
2243 the shell and they are inherited by all the other programs you run. When
2244 debugging, it can be useful to try running your program with a modified
2245 environment without having to start @value{GDBN} over again.
2249 @item path @var{directory}
2250 Add @var{directory} to the front of the @code{PATH} environment variable
2251 (the search path for executables) that will be passed to your program.
2252 The value of @code{PATH} used by @value{GDBN} does not change.
2253 You may specify several directory names, separated by whitespace or by a
2254 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2255 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2256 is moved to the front, so it is searched sooner.
2258 You can use the string @samp{$cwd} to refer to whatever is the current
2259 working directory at the time @value{GDBN} searches the path. If you
2260 use @samp{.} instead, it refers to the directory where you executed the
2261 @code{path} command. @value{GDBN} replaces @samp{.} in the
2262 @var{directory} argument (with the current path) before adding
2263 @var{directory} to the search path.
2264 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2265 @c document that, since repeating it would be a no-op.
2269 Display the list of search paths for executables (the @code{PATH}
2270 environment variable).
2272 @kindex show environment
2273 @item show environment @r{[}@var{varname}@r{]}
2274 Print the value of environment variable @var{varname} to be given to
2275 your program when it starts. If you do not supply @var{varname},
2276 print the names and values of all environment variables to be given to
2277 your program. You can abbreviate @code{environment} as @code{env}.
2279 @kindex set environment
2280 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2281 Set environment variable @var{varname} to @var{value}. The value
2282 changes for your program only, not for @value{GDBN} itself. @var{value} may
2283 be any string; the values of environment variables are just strings, and
2284 any interpretation is supplied by your program itself. The @var{value}
2285 parameter is optional; if it is eliminated, the variable is set to a
2287 @c "any string" here does not include leading, trailing
2288 @c blanks. Gnu asks: does anyone care?
2290 For example, this command:
2297 tells the debugged program, when subsequently run, that its user is named
2298 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2299 are not actually required.)
2301 @kindex unset environment
2302 @item unset environment @var{varname}
2303 Remove variable @var{varname} from the environment to be passed to your
2304 program. This is different from @samp{set env @var{varname} =};
2305 @code{unset environment} removes the variable from the environment,
2306 rather than assigning it an empty value.
2309 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2310 the shell indicated by your @code{SHELL} environment variable if it
2311 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2312 names a shell that runs an initialization file when started
2313 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2314 for the Z shell, or the file specified in the @samp{BASH_ENV}
2315 environment variable for BASH---any variables you set in that file
2316 affect your program. You may wish to move setting of environment
2317 variables to files that are only run when you sign on, such as
2318 @file{.login} or @file{.profile}.
2320 @node Working Directory
2321 @section Your Program's Working Directory
2323 @cindex working directory (of your program)
2324 Each time you start your program with @code{run}, it inherits its
2325 working directory from the current working directory of @value{GDBN}.
2326 The @value{GDBN} working directory is initially whatever it inherited
2327 from its parent process (typically the shell), but you can specify a new
2328 working directory in @value{GDBN} with the @code{cd} command.
2330 The @value{GDBN} working directory also serves as a default for the commands
2331 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2336 @cindex change working directory
2337 @item cd @r{[}@var{directory}@r{]}
2338 Set the @value{GDBN} working directory to @var{directory}. If not
2339 given, @var{directory} uses @file{'~'}.
2343 Print the @value{GDBN} working directory.
2346 It is generally impossible to find the current working directory of
2347 the process being debugged (since a program can change its directory
2348 during its run). If you work on a system where @value{GDBN} is
2349 configured with the @file{/proc} support, you can use the @code{info
2350 proc} command (@pxref{SVR4 Process Information}) to find out the
2351 current working directory of the debuggee.
2354 @section Your Program's Input and Output
2359 By default, the program you run under @value{GDBN} does input and output to
2360 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2361 to its own terminal modes to interact with you, but it records the terminal
2362 modes your program was using and switches back to them when you continue
2363 running your program.
2366 @kindex info terminal
2368 Displays information recorded by @value{GDBN} about the terminal modes your
2372 You can redirect your program's input and/or output using shell
2373 redirection with the @code{run} command. For example,
2380 starts your program, diverting its output to the file @file{outfile}.
2383 @cindex controlling terminal
2384 Another way to specify where your program should do input and output is
2385 with the @code{tty} command. This command accepts a file name as
2386 argument, and causes this file to be the default for future @code{run}
2387 commands. It also resets the controlling terminal for the child
2388 process, for future @code{run} commands. For example,
2395 directs that processes started with subsequent @code{run} commands
2396 default to do input and output on the terminal @file{/dev/ttyb} and have
2397 that as their controlling terminal.
2399 An explicit redirection in @code{run} overrides the @code{tty} command's
2400 effect on the input/output device, but not its effect on the controlling
2403 When you use the @code{tty} command or redirect input in the @code{run}
2404 command, only the input @emph{for your program} is affected. The input
2405 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2406 for @code{set inferior-tty}.
2408 @cindex inferior tty
2409 @cindex set inferior controlling terminal
2410 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2411 display the name of the terminal that will be used for future runs of your
2415 @item set inferior-tty /dev/ttyb
2416 @kindex set inferior-tty
2417 Set the tty for the program being debugged to /dev/ttyb.
2419 @item show inferior-tty
2420 @kindex show inferior-tty
2421 Show the current tty for the program being debugged.
2425 @section Debugging an Already-running Process
2430 @item attach @var{process-id}
2431 This command attaches to a running process---one that was started
2432 outside @value{GDBN}. (@code{info files} shows your active
2433 targets.) The command takes as argument a process ID. The usual way to
2434 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2435 or with the @samp{jobs -l} shell command.
2437 @code{attach} does not repeat if you press @key{RET} a second time after
2438 executing the command.
2441 To use @code{attach}, your program must be running in an environment
2442 which supports processes; for example, @code{attach} does not work for
2443 programs on bare-board targets that lack an operating system. You must
2444 also have permission to send the process a signal.
2446 When you use @code{attach}, the debugger finds the program running in
2447 the process first by looking in the current working directory, then (if
2448 the program is not found) by using the source file search path
2449 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2450 the @code{file} command to load the program. @xref{Files, ,Commands to
2453 The first thing @value{GDBN} does after arranging to debug the specified
2454 process is to stop it. You can examine and modify an attached process
2455 with all the @value{GDBN} commands that are ordinarily available when
2456 you start processes with @code{run}. You can insert breakpoints; you
2457 can step and continue; you can modify storage. If you would rather the
2458 process continue running, you may use the @code{continue} command after
2459 attaching @value{GDBN} to the process.
2464 When you have finished debugging the attached process, you can use the
2465 @code{detach} command to release it from @value{GDBN} control. Detaching
2466 the process continues its execution. After the @code{detach} command,
2467 that process and @value{GDBN} become completely independent once more, and you
2468 are ready to @code{attach} another process or start one with @code{run}.
2469 @code{detach} does not repeat if you press @key{RET} again after
2470 executing the command.
2473 If you exit @value{GDBN} while you have an attached process, you detach
2474 that process. If you use the @code{run} command, you kill that process.
2475 By default, @value{GDBN} asks for confirmation if you try to do either of these
2476 things; you can control whether or not you need to confirm by using the
2477 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2481 @section Killing the Child Process
2486 Kill the child process in which your program is running under @value{GDBN}.
2489 This command is useful if you wish to debug a core dump instead of a
2490 running process. @value{GDBN} ignores any core dump file while your program
2493 On some operating systems, a program cannot be executed outside @value{GDBN}
2494 while you have breakpoints set on it inside @value{GDBN}. You can use the
2495 @code{kill} command in this situation to permit running your program
2496 outside the debugger.
2498 The @code{kill} command is also useful if you wish to recompile and
2499 relink your program, since on many systems it is impossible to modify an
2500 executable file while it is running in a process. In this case, when you
2501 next type @code{run}, @value{GDBN} notices that the file has changed, and
2502 reads the symbol table again (while trying to preserve your current
2503 breakpoint settings).
2505 @node Inferiors and Programs
2506 @section Debugging Multiple Inferiors and Programs
2508 @value{GDBN} lets you run and debug multiple programs in a single
2509 session. In addition, @value{GDBN} on some systems may let you run
2510 several programs simultaneously (otherwise you have to exit from one
2511 before starting another). In the most general case, you can have
2512 multiple threads of execution in each of multiple processes, launched
2513 from multiple executables.
2516 @value{GDBN} represents the state of each program execution with an
2517 object called an @dfn{inferior}. An inferior typically corresponds to
2518 a process, but is more general and applies also to targets that do not
2519 have processes. Inferiors may be created before a process runs, and
2520 may be retained after a process exits. Inferiors have unique
2521 identifiers that are different from process ids. Usually each
2522 inferior will also have its own distinct address space, although some
2523 embedded targets may have several inferiors running in different parts
2524 of a single address space. Each inferior may in turn have multiple
2525 threads running in it.
2527 To find out what inferiors exist at any moment, use @w{@code{info
2531 @kindex info inferiors
2532 @item info inferiors
2533 Print a list of all inferiors currently being managed by @value{GDBN}.
2535 @value{GDBN} displays for each inferior (in this order):
2539 the inferior number assigned by @value{GDBN}
2542 the target system's inferior identifier
2545 the name of the executable the inferior is running.
2550 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2551 indicates the current inferior.
2555 @c end table here to get a little more width for example
2558 (@value{GDBP}) info inferiors
2559 Num Description Executable
2560 2 process 2307 hello
2561 * 1 process 3401 goodbye
2564 To switch focus between inferiors, use the @code{inferior} command:
2567 @kindex inferior @var{infno}
2568 @item inferior @var{infno}
2569 Make inferior number @var{infno} the current inferior. The argument
2570 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2571 in the first field of the @samp{info inferiors} display.
2575 You can get multiple executables into a debugging session via the
2576 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2577 systems @value{GDBN} can add inferiors to the debug session
2578 automatically by following calls to @code{fork} and @code{exec}. To
2579 remove inferiors from the debugging session use the
2580 @w{@code{remove-inferiors}} command.
2583 @kindex add-inferior
2584 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2585 Adds @var{n} inferiors to be run using @var{executable} as the
2586 executable. @var{n} defaults to 1. If no executable is specified,
2587 the inferiors begins empty, with no program. You can still assign or
2588 change the program assigned to the inferior at any time by using the
2589 @code{file} command with the executable name as its argument.
2591 @kindex clone-inferior
2592 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2593 Adds @var{n} inferiors ready to execute the same program as inferior
2594 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2595 number of the current inferior. This is a convenient command when you
2596 want to run another instance of the inferior you are debugging.
2599 (@value{GDBP}) info inferiors
2600 Num Description Executable
2601 * 1 process 29964 helloworld
2602 (@value{GDBP}) clone-inferior
2605 (@value{GDBP}) info inferiors
2606 Num Description Executable
2608 * 1 process 29964 helloworld
2611 You can now simply switch focus to inferior 2 and run it.
2613 @kindex remove-inferiors
2614 @item remove-inferiors @var{infno}@dots{}
2615 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2616 possible to remove an inferior that is running with this command. For
2617 those, use the @code{kill} or @code{detach} command first.
2621 To quit debugging one of the running inferiors that is not the current
2622 inferior, you can either detach from it by using the @w{@code{detach
2623 inferior}} command (allowing it to run independently), or kill it
2624 using the @w{@code{kill inferiors}} command:
2627 @kindex detach inferiors @var{infno}@dots{}
2628 @item detach inferior @var{infno}@dots{}
2629 Detach from the inferior or inferiors identified by @value{GDBN}
2630 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2631 still stays on the list of inferiors shown by @code{info inferiors},
2632 but its Description will show @samp{<null>}.
2634 @kindex kill inferiors @var{infno}@dots{}
2635 @item kill inferiors @var{infno}@dots{}
2636 Kill the inferior or inferiors identified by @value{GDBN} inferior
2637 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2638 stays on the list of inferiors shown by @code{info inferiors}, but its
2639 Description will show @samp{<null>}.
2642 After the successful completion of a command such as @code{detach},
2643 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2644 a normal process exit, the inferior is still valid and listed with
2645 @code{info inferiors}, ready to be restarted.
2648 To be notified when inferiors are started or exit under @value{GDBN}'s
2649 control use @w{@code{set print inferior-events}}:
2652 @kindex set print inferior-events
2653 @cindex print messages on inferior start and exit
2654 @item set print inferior-events
2655 @itemx set print inferior-events on
2656 @itemx set print inferior-events off
2657 The @code{set print inferior-events} command allows you to enable or
2658 disable printing of messages when @value{GDBN} notices that new
2659 inferiors have started or that inferiors have exited or have been
2660 detached. By default, these messages will not be printed.
2662 @kindex show print inferior-events
2663 @item show print inferior-events
2664 Show whether messages will be printed when @value{GDBN} detects that
2665 inferiors have started, exited or have been detached.
2668 Many commands will work the same with multiple programs as with a
2669 single program: e.g., @code{print myglobal} will simply display the
2670 value of @code{myglobal} in the current inferior.
2673 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2674 get more info about the relationship of inferiors, programs, address
2675 spaces in a debug session. You can do that with the @w{@code{maint
2676 info program-spaces}} command.
2679 @kindex maint info program-spaces
2680 @item maint info program-spaces
2681 Print a list of all program spaces currently being managed by
2684 @value{GDBN} displays for each program space (in this order):
2688 the program space number assigned by @value{GDBN}
2691 the name of the executable loaded into the program space, with e.g.,
2692 the @code{file} command.
2697 An asterisk @samp{*} preceding the @value{GDBN} program space number
2698 indicates the current program space.
2700 In addition, below each program space line, @value{GDBN} prints extra
2701 information that isn't suitable to display in tabular form. For
2702 example, the list of inferiors bound to the program space.
2705 (@value{GDBP}) maint info program-spaces
2708 Bound inferiors: ID 1 (process 21561)
2712 Here we can see that no inferior is running the program @code{hello},
2713 while @code{process 21561} is running the program @code{goodbye}. On
2714 some targets, it is possible that multiple inferiors are bound to the
2715 same program space. The most common example is that of debugging both
2716 the parent and child processes of a @code{vfork} call. For example,
2719 (@value{GDBP}) maint info program-spaces
2722 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2725 Here, both inferior 2 and inferior 1 are running in the same program
2726 space as a result of inferior 1 having executed a @code{vfork} call.
2730 @section Debugging Programs with Multiple Threads
2732 @cindex threads of execution
2733 @cindex multiple threads
2734 @cindex switching threads
2735 In some operating systems, such as HP-UX and Solaris, a single program
2736 may have more than one @dfn{thread} of execution. The precise semantics
2737 of threads differ from one operating system to another, but in general
2738 the threads of a single program are akin to multiple processes---except
2739 that they share one address space (that is, they can all examine and
2740 modify the same variables). On the other hand, each thread has its own
2741 registers and execution stack, and perhaps private memory.
2743 @value{GDBN} provides these facilities for debugging multi-thread
2747 @item automatic notification of new threads
2748 @item @samp{thread @var{threadno}}, a command to switch among threads
2749 @item @samp{info threads}, a command to inquire about existing threads
2750 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2751 a command to apply a command to a list of threads
2752 @item thread-specific breakpoints
2753 @item @samp{set print thread-events}, which controls printing of
2754 messages on thread start and exit.
2755 @item @samp{set libthread-db-search-path @var{path}}, which lets
2756 the user specify which @code{libthread_db} to use if the default choice
2757 isn't compatible with the program.
2761 @emph{Warning:} These facilities are not yet available on every
2762 @value{GDBN} configuration where the operating system supports threads.
2763 If your @value{GDBN} does not support threads, these commands have no
2764 effect. For example, a system without thread support shows no output
2765 from @samp{info threads}, and always rejects the @code{thread} command,
2769 (@value{GDBP}) info threads
2770 (@value{GDBP}) thread 1
2771 Thread ID 1 not known. Use the "info threads" command to
2772 see the IDs of currently known threads.
2774 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2775 @c doesn't support threads"?
2778 @cindex focus of debugging
2779 @cindex current thread
2780 The @value{GDBN} thread debugging facility allows you to observe all
2781 threads while your program runs---but whenever @value{GDBN} takes
2782 control, one thread in particular is always the focus of debugging.
2783 This thread is called the @dfn{current thread}. Debugging commands show
2784 program information from the perspective of the current thread.
2786 @cindex @code{New} @var{systag} message
2787 @cindex thread identifier (system)
2788 @c FIXME-implementors!! It would be more helpful if the [New...] message
2789 @c included GDB's numeric thread handle, so you could just go to that
2790 @c thread without first checking `info threads'.
2791 Whenever @value{GDBN} detects a new thread in your program, it displays
2792 the target system's identification for the thread with a message in the
2793 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2794 whose form varies depending on the particular system. For example, on
2795 @sc{gnu}/Linux, you might see
2798 [New Thread 0x41e02940 (LWP 25582)]
2802 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2803 the @var{systag} is simply something like @samp{process 368}, with no
2806 @c FIXME!! (1) Does the [New...] message appear even for the very first
2807 @c thread of a program, or does it only appear for the
2808 @c second---i.e.@: when it becomes obvious we have a multithread
2810 @c (2) *Is* there necessarily a first thread always? Or do some
2811 @c multithread systems permit starting a program with multiple
2812 @c threads ab initio?
2814 @cindex thread number
2815 @cindex thread identifier (GDB)
2816 For debugging purposes, @value{GDBN} associates its own thread
2817 number---always a single integer---with each thread in your program.
2820 @kindex info threads
2821 @item info threads @r{[}@var{id}@dots{}@r{]}
2822 Display a summary of all threads currently in your program. Optional
2823 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2824 means to print information only about the specified thread or threads.
2825 @value{GDBN} displays for each thread (in this order):
2829 the thread number assigned by @value{GDBN}
2832 the target system's thread identifier (@var{systag})
2835 the thread's name, if one is known. A thread can either be named by
2836 the user (see @code{thread name}, below), or, in some cases, by the
2840 the current stack frame summary for that thread
2844 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2845 indicates the current thread.
2849 @c end table here to get a little more width for example
2852 (@value{GDBP}) info threads
2854 3 process 35 thread 27 0x34e5 in sigpause ()
2855 2 process 35 thread 23 0x34e5 in sigpause ()
2856 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2860 On Solaris, you can display more information about user threads with a
2861 Solaris-specific command:
2864 @item maint info sol-threads
2865 @kindex maint info sol-threads
2866 @cindex thread info (Solaris)
2867 Display info on Solaris user threads.
2871 @kindex thread @var{threadno}
2872 @item thread @var{threadno}
2873 Make thread number @var{threadno} the current thread. The command
2874 argument @var{threadno} is the internal @value{GDBN} thread number, as
2875 shown in the first field of the @samp{info threads} display.
2876 @value{GDBN} responds by displaying the system identifier of the thread
2877 you selected, and its current stack frame summary:
2880 (@value{GDBP}) thread 2
2881 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2882 #0 some_function (ignore=0x0) at example.c:8
2883 8 printf ("hello\n");
2887 As with the @samp{[New @dots{}]} message, the form of the text after
2888 @samp{Switching to} depends on your system's conventions for identifying
2891 @vindex $_thread@r{, convenience variable}
2892 The debugger convenience variable @samp{$_thread} contains the number
2893 of the current thread. You may find this useful in writing breakpoint
2894 conditional expressions, command scripts, and so forth. See
2895 @xref{Convenience Vars,, Convenience Variables}, for general
2896 information on convenience variables.
2898 @kindex thread apply
2899 @cindex apply command to several threads
2900 @item thread apply [@var{threadno} | all] @var{command}
2901 The @code{thread apply} command allows you to apply the named
2902 @var{command} to one or more threads. Specify the numbers of the
2903 threads that you want affected with the command argument
2904 @var{threadno}. It can be a single thread number, one of the numbers
2905 shown in the first field of the @samp{info threads} display; or it
2906 could be a range of thread numbers, as in @code{2-4}. To apply a
2907 command to all threads, type @kbd{thread apply all @var{command}}.
2910 @cindex name a thread
2911 @item thread name [@var{name}]
2912 This command assigns a name to the current thread. If no argument is
2913 given, any existing user-specified name is removed. The thread name
2914 appears in the @samp{info threads} display.
2916 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2917 determine the name of the thread as given by the OS. On these
2918 systems, a name specified with @samp{thread name} will override the
2919 system-give name, and removing the user-specified name will cause
2920 @value{GDBN} to once again display the system-specified name.
2923 @cindex search for a thread
2924 @item thread find [@var{regexp}]
2925 Search for and display thread ids whose name or @var{systag}
2926 matches the supplied regular expression.
2928 As well as being the complement to the @samp{thread name} command,
2929 this command also allows you to identify a thread by its target
2930 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2934 (@value{GDBN}) thread find 26688
2935 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2936 (@value{GDBN}) info thread 4
2938 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2941 @kindex set print thread-events
2942 @cindex print messages on thread start and exit
2943 @item set print thread-events
2944 @itemx set print thread-events on
2945 @itemx set print thread-events off
2946 The @code{set print thread-events} command allows you to enable or
2947 disable printing of messages when @value{GDBN} notices that new threads have
2948 started or that threads have exited. By default, these messages will
2949 be printed if detection of these events is supported by the target.
2950 Note that these messages cannot be disabled on all targets.
2952 @kindex show print thread-events
2953 @item show print thread-events
2954 Show whether messages will be printed when @value{GDBN} detects that threads
2955 have started and exited.
2958 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2959 more information about how @value{GDBN} behaves when you stop and start
2960 programs with multiple threads.
2962 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2963 watchpoints in programs with multiple threads.
2965 @anchor{set libthread-db-search-path}
2967 @kindex set libthread-db-search-path
2968 @cindex search path for @code{libthread_db}
2969 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2970 If this variable is set, @var{path} is a colon-separated list of
2971 directories @value{GDBN} will use to search for @code{libthread_db}.
2972 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2973 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2974 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2977 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2978 @code{libthread_db} library to obtain information about threads in the
2979 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2980 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2981 specific thread debugging library loading is enabled
2982 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2984 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2985 refers to the default system directories that are
2986 normally searched for loading shared libraries. The @samp{$sdir} entry
2987 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2988 (@pxref{libthread_db.so.1 file}).
2990 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2991 refers to the directory from which @code{libpthread}
2992 was loaded in the inferior process.
2994 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2995 @value{GDBN} attempts to initialize it with the current inferior process.
2996 If this initialization fails (which could happen because of a version
2997 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2998 will unload @code{libthread_db}, and continue with the next directory.
2999 If none of @code{libthread_db} libraries initialize successfully,
3000 @value{GDBN} will issue a warning and thread debugging will be disabled.
3002 Setting @code{libthread-db-search-path} is currently implemented
3003 only on some platforms.
3005 @kindex show libthread-db-search-path
3006 @item show libthread-db-search-path
3007 Display current libthread_db search path.
3009 @kindex set debug libthread-db
3010 @kindex show debug libthread-db
3011 @cindex debugging @code{libthread_db}
3012 @item set debug libthread-db
3013 @itemx show debug libthread-db
3014 Turns on or off display of @code{libthread_db}-related events.
3015 Use @code{1} to enable, @code{0} to disable.
3019 @section Debugging Forks
3021 @cindex fork, debugging programs which call
3022 @cindex multiple processes
3023 @cindex processes, multiple
3024 On most systems, @value{GDBN} has no special support for debugging
3025 programs which create additional processes using the @code{fork}
3026 function. When a program forks, @value{GDBN} will continue to debug the
3027 parent process and the child process will run unimpeded. If you have
3028 set a breakpoint in any code which the child then executes, the child
3029 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3030 will cause it to terminate.
3032 However, if you want to debug the child process there is a workaround
3033 which isn't too painful. Put a call to @code{sleep} in the code which
3034 the child process executes after the fork. It may be useful to sleep
3035 only if a certain environment variable is set, or a certain file exists,
3036 so that the delay need not occur when you don't want to run @value{GDBN}
3037 on the child. While the child is sleeping, use the @code{ps} program to
3038 get its process ID. Then tell @value{GDBN} (a new invocation of
3039 @value{GDBN} if you are also debugging the parent process) to attach to
3040 the child process (@pxref{Attach}). From that point on you can debug
3041 the child process just like any other process which you attached to.
3043 On some systems, @value{GDBN} provides support for debugging programs that
3044 create additional processes using the @code{fork} or @code{vfork} functions.
3045 Currently, the only platforms with this feature are HP-UX (11.x and later
3046 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3048 By default, when a program forks, @value{GDBN} will continue to debug
3049 the parent process and the child process will run unimpeded.
3051 If you want to follow the child process instead of the parent process,
3052 use the command @w{@code{set follow-fork-mode}}.
3055 @kindex set follow-fork-mode
3056 @item set follow-fork-mode @var{mode}
3057 Set the debugger response to a program call of @code{fork} or
3058 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3059 process. The @var{mode} argument can be:
3063 The original process is debugged after a fork. The child process runs
3064 unimpeded. This is the default.
3067 The new process is debugged after a fork. The parent process runs
3072 @kindex show follow-fork-mode
3073 @item show follow-fork-mode
3074 Display the current debugger response to a @code{fork} or @code{vfork} call.
3077 @cindex debugging multiple processes
3078 On Linux, if you want to debug both the parent and child processes, use the
3079 command @w{@code{set detach-on-fork}}.
3082 @kindex set detach-on-fork
3083 @item set detach-on-fork @var{mode}
3084 Tells gdb whether to detach one of the processes after a fork, or
3085 retain debugger control over them both.
3089 The child process (or parent process, depending on the value of
3090 @code{follow-fork-mode}) will be detached and allowed to run
3091 independently. This is the default.
3094 Both processes will be held under the control of @value{GDBN}.
3095 One process (child or parent, depending on the value of
3096 @code{follow-fork-mode}) is debugged as usual, while the other
3101 @kindex show detach-on-fork
3102 @item show detach-on-fork
3103 Show whether detach-on-fork mode is on/off.
3106 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3107 will retain control of all forked processes (including nested forks).
3108 You can list the forked processes under the control of @value{GDBN} by
3109 using the @w{@code{info inferiors}} command, and switch from one fork
3110 to another by using the @code{inferior} command (@pxref{Inferiors and
3111 Programs, ,Debugging Multiple Inferiors and Programs}).
3113 To quit debugging one of the forked processes, you can either detach
3114 from it by using the @w{@code{detach inferiors}} command (allowing it
3115 to run independently), or kill it using the @w{@code{kill inferiors}}
3116 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3119 If you ask to debug a child process and a @code{vfork} is followed by an
3120 @code{exec}, @value{GDBN} executes the new target up to the first
3121 breakpoint in the new target. If you have a breakpoint set on
3122 @code{main} in your original program, the breakpoint will also be set on
3123 the child process's @code{main}.
3125 On some systems, when a child process is spawned by @code{vfork}, you
3126 cannot debug the child or parent until an @code{exec} call completes.
3128 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3129 call executes, the new target restarts. To restart the parent
3130 process, use the @code{file} command with the parent executable name
3131 as its argument. By default, after an @code{exec} call executes,
3132 @value{GDBN} discards the symbols of the previous executable image.
3133 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3137 @kindex set follow-exec-mode
3138 @item set follow-exec-mode @var{mode}
3140 Set debugger response to a program call of @code{exec}. An
3141 @code{exec} call replaces the program image of a process.
3143 @code{follow-exec-mode} can be:
3147 @value{GDBN} creates a new inferior and rebinds the process to this
3148 new inferior. The program the process was running before the
3149 @code{exec} call can be restarted afterwards by restarting the
3155 (@value{GDBP}) info inferiors
3157 Id Description Executable
3160 process 12020 is executing new program: prog2
3161 Program exited normally.
3162 (@value{GDBP}) info inferiors
3163 Id Description Executable
3169 @value{GDBN} keeps the process bound to the same inferior. The new
3170 executable image replaces the previous executable loaded in the
3171 inferior. Restarting the inferior after the @code{exec} call, with
3172 e.g., the @code{run} command, restarts the executable the process was
3173 running after the @code{exec} call. This is the default mode.
3178 (@value{GDBP}) info inferiors
3179 Id Description Executable
3182 process 12020 is executing new program: prog2
3183 Program exited normally.
3184 (@value{GDBP}) info inferiors
3185 Id Description Executable
3192 You can use the @code{catch} command to make @value{GDBN} stop whenever
3193 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3194 Catchpoints, ,Setting Catchpoints}.
3196 @node Checkpoint/Restart
3197 @section Setting a @emph{Bookmark} to Return to Later
3202 @cindex snapshot of a process
3203 @cindex rewind program state
3205 On certain operating systems@footnote{Currently, only
3206 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3207 program's state, called a @dfn{checkpoint}, and come back to it
3210 Returning to a checkpoint effectively undoes everything that has
3211 happened in the program since the @code{checkpoint} was saved. This
3212 includes changes in memory, registers, and even (within some limits)
3213 system state. Effectively, it is like going back in time to the
3214 moment when the checkpoint was saved.
3216 Thus, if you're stepping thru a program and you think you're
3217 getting close to the point where things go wrong, you can save
3218 a checkpoint. Then, if you accidentally go too far and miss
3219 the critical statement, instead of having to restart your program
3220 from the beginning, you can just go back to the checkpoint and
3221 start again from there.
3223 This can be especially useful if it takes a lot of time or
3224 steps to reach the point where you think the bug occurs.
3226 To use the @code{checkpoint}/@code{restart} method of debugging:
3231 Save a snapshot of the debugged program's current execution state.
3232 The @code{checkpoint} command takes no arguments, but each checkpoint
3233 is assigned a small integer id, similar to a breakpoint id.
3235 @kindex info checkpoints
3236 @item info checkpoints
3237 List the checkpoints that have been saved in the current debugging
3238 session. For each checkpoint, the following information will be
3245 @item Source line, or label
3248 @kindex restart @var{checkpoint-id}
3249 @item restart @var{checkpoint-id}
3250 Restore the program state that was saved as checkpoint number
3251 @var{checkpoint-id}. All program variables, registers, stack frames
3252 etc.@: will be returned to the values that they had when the checkpoint
3253 was saved. In essence, gdb will ``wind back the clock'' to the point
3254 in time when the checkpoint was saved.
3256 Note that breakpoints, @value{GDBN} variables, command history etc.
3257 are not affected by restoring a checkpoint. In general, a checkpoint
3258 only restores things that reside in the program being debugged, not in
3261 @kindex delete checkpoint @var{checkpoint-id}
3262 @item delete checkpoint @var{checkpoint-id}
3263 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3267 Returning to a previously saved checkpoint will restore the user state
3268 of the program being debugged, plus a significant subset of the system
3269 (OS) state, including file pointers. It won't ``un-write'' data from
3270 a file, but it will rewind the file pointer to the previous location,
3271 so that the previously written data can be overwritten. For files
3272 opened in read mode, the pointer will also be restored so that the
3273 previously read data can be read again.
3275 Of course, characters that have been sent to a printer (or other
3276 external device) cannot be ``snatched back'', and characters received
3277 from eg.@: a serial device can be removed from internal program buffers,
3278 but they cannot be ``pushed back'' into the serial pipeline, ready to
3279 be received again. Similarly, the actual contents of files that have
3280 been changed cannot be restored (at this time).
3282 However, within those constraints, you actually can ``rewind'' your
3283 program to a previously saved point in time, and begin debugging it
3284 again --- and you can change the course of events so as to debug a
3285 different execution path this time.
3287 @cindex checkpoints and process id
3288 Finally, there is one bit of internal program state that will be
3289 different when you return to a checkpoint --- the program's process
3290 id. Each checkpoint will have a unique process id (or @var{pid}),
3291 and each will be different from the program's original @var{pid}.
3292 If your program has saved a local copy of its process id, this could
3293 potentially pose a problem.
3295 @subsection A Non-obvious Benefit of Using Checkpoints
3297 On some systems such as @sc{gnu}/Linux, address space randomization
3298 is performed on new processes for security reasons. This makes it
3299 difficult or impossible to set a breakpoint, or watchpoint, on an
3300 absolute address if you have to restart the program, since the
3301 absolute location of a symbol will change from one execution to the
3304 A checkpoint, however, is an @emph{identical} copy of a process.
3305 Therefore if you create a checkpoint at (eg.@:) the start of main,
3306 and simply return to that checkpoint instead of restarting the
3307 process, you can avoid the effects of address randomization and
3308 your symbols will all stay in the same place.
3311 @chapter Stopping and Continuing
3313 The principal purposes of using a debugger are so that you can stop your
3314 program before it terminates; or so that, if your program runs into
3315 trouble, you can investigate and find out why.
3317 Inside @value{GDBN}, your program may stop for any of several reasons,
3318 such as a signal, a breakpoint, or reaching a new line after a
3319 @value{GDBN} command such as @code{step}. You may then examine and
3320 change variables, set new breakpoints or remove old ones, and then
3321 continue execution. Usually, the messages shown by @value{GDBN} provide
3322 ample explanation of the status of your program---but you can also
3323 explicitly request this information at any time.
3326 @kindex info program
3328 Display information about the status of your program: whether it is
3329 running or not, what process it is, and why it stopped.
3333 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3334 * Continuing and Stepping:: Resuming execution
3335 * Skipping Over Functions and Files::
3336 Skipping over functions and files
3338 * Thread Stops:: Stopping and starting multi-thread programs
3342 @section Breakpoints, Watchpoints, and Catchpoints
3345 A @dfn{breakpoint} makes your program stop whenever a certain point in
3346 the program is reached. For each breakpoint, you can add conditions to
3347 control in finer detail whether your program stops. You can set
3348 breakpoints with the @code{break} command and its variants (@pxref{Set
3349 Breaks, ,Setting Breakpoints}), to specify the place where your program
3350 should stop by line number, function name or exact address in the
3353 On some systems, you can set breakpoints in shared libraries before
3354 the executable is run. There is a minor limitation on HP-UX systems:
3355 you must wait until the executable is run in order to set breakpoints
3356 in shared library routines that are not called directly by the program
3357 (for example, routines that are arguments in a @code{pthread_create}
3361 @cindex data breakpoints
3362 @cindex memory tracing
3363 @cindex breakpoint on memory address
3364 @cindex breakpoint on variable modification
3365 A @dfn{watchpoint} is a special breakpoint that stops your program
3366 when the value of an expression changes. The expression may be a value
3367 of a variable, or it could involve values of one or more variables
3368 combined by operators, such as @samp{a + b}. This is sometimes called
3369 @dfn{data breakpoints}. You must use a different command to set
3370 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3371 from that, you can manage a watchpoint like any other breakpoint: you
3372 enable, disable, and delete both breakpoints and watchpoints using the
3375 You can arrange to have values from your program displayed automatically
3376 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3380 @cindex breakpoint on events
3381 A @dfn{catchpoint} is another special breakpoint that stops your program
3382 when a certain kind of event occurs, such as the throwing of a C@t{++}
3383 exception or the loading of a library. As with watchpoints, you use a
3384 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3385 Catchpoints}), but aside from that, you can manage a catchpoint like any
3386 other breakpoint. (To stop when your program receives a signal, use the
3387 @code{handle} command; see @ref{Signals, ,Signals}.)
3389 @cindex breakpoint numbers
3390 @cindex numbers for breakpoints
3391 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3392 catchpoint when you create it; these numbers are successive integers
3393 starting with one. In many of the commands for controlling various
3394 features of breakpoints you use the breakpoint number to say which
3395 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3396 @dfn{disabled}; if disabled, it has no effect on your program until you
3399 @cindex breakpoint ranges
3400 @cindex ranges of breakpoints
3401 Some @value{GDBN} commands accept a range of breakpoints on which to
3402 operate. A breakpoint range is either a single breakpoint number, like
3403 @samp{5}, or two such numbers, in increasing order, separated by a
3404 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3405 all breakpoints in that range are operated on.
3408 * Set Breaks:: Setting breakpoints
3409 * Set Watchpoints:: Setting watchpoints
3410 * Set Catchpoints:: Setting catchpoints
3411 * Delete Breaks:: Deleting breakpoints
3412 * Disabling:: Disabling breakpoints
3413 * Conditions:: Break conditions
3414 * Break Commands:: Breakpoint command lists
3415 * Dynamic Printf:: Dynamic printf
3416 * Save Breakpoints:: How to save breakpoints in a file
3417 * Static Probe Points:: Listing static probe points
3418 * Error in Breakpoints:: ``Cannot insert breakpoints''
3419 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3423 @subsection Setting Breakpoints
3425 @c FIXME LMB what does GDB do if no code on line of breakpt?
3426 @c consider in particular declaration with/without initialization.
3428 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3431 @kindex b @r{(@code{break})}
3432 @vindex $bpnum@r{, convenience variable}
3433 @cindex latest breakpoint
3434 Breakpoints are set with the @code{break} command (abbreviated
3435 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3436 number of the breakpoint you've set most recently; see @ref{Convenience
3437 Vars,, Convenience Variables}, for a discussion of what you can do with
3438 convenience variables.
3441 @item break @var{location}
3442 Set a breakpoint at the given @var{location}, which can specify a
3443 function name, a line number, or an address of an instruction.
3444 (@xref{Specify Location}, for a list of all the possible ways to
3445 specify a @var{location}.) The breakpoint will stop your program just
3446 before it executes any of the code in the specified @var{location}.
3448 When using source languages that permit overloading of symbols, such as
3449 C@t{++}, a function name may refer to more than one possible place to break.
3450 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3453 It is also possible to insert a breakpoint that will stop the program
3454 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3455 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3458 When called without any arguments, @code{break} sets a breakpoint at
3459 the next instruction to be executed in the selected stack frame
3460 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3461 innermost, this makes your program stop as soon as control
3462 returns to that frame. This is similar to the effect of a
3463 @code{finish} command in the frame inside the selected frame---except
3464 that @code{finish} does not leave an active breakpoint. If you use
3465 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3466 the next time it reaches the current location; this may be useful
3469 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3470 least one instruction has been executed. If it did not do this, you
3471 would be unable to proceed past a breakpoint without first disabling the
3472 breakpoint. This rule applies whether or not the breakpoint already
3473 existed when your program stopped.
3475 @item break @dots{} if @var{cond}
3476 Set a breakpoint with condition @var{cond}; evaluate the expression
3477 @var{cond} each time the breakpoint is reached, and stop only if the
3478 value is nonzero---that is, if @var{cond} evaluates as true.
3479 @samp{@dots{}} stands for one of the possible arguments described
3480 above (or no argument) specifying where to break. @xref{Conditions,
3481 ,Break Conditions}, for more information on breakpoint conditions.
3484 @item tbreak @var{args}
3485 Set a breakpoint enabled only for one stop. @var{args} are the
3486 same as for the @code{break} command, and the breakpoint is set in the same
3487 way, but the breakpoint is automatically deleted after the first time your
3488 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3491 @cindex hardware breakpoints
3492 @item hbreak @var{args}
3493 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3494 @code{break} command and the breakpoint is set in the same way, but the
3495 breakpoint requires hardware support and some target hardware may not
3496 have this support. The main purpose of this is EPROM/ROM code
3497 debugging, so you can set a breakpoint at an instruction without
3498 changing the instruction. This can be used with the new trap-generation
3499 provided by SPARClite DSU and most x86-based targets. These targets
3500 will generate traps when a program accesses some data or instruction
3501 address that is assigned to the debug registers. However the hardware
3502 breakpoint registers can take a limited number of breakpoints. For
3503 example, on the DSU, only two data breakpoints can be set at a time, and
3504 @value{GDBN} will reject this command if more than two are used. Delete
3505 or disable unused hardware breakpoints before setting new ones
3506 (@pxref{Disabling, ,Disabling Breakpoints}).
3507 @xref{Conditions, ,Break Conditions}.
3508 For remote targets, you can restrict the number of hardware
3509 breakpoints @value{GDBN} will use, see @ref{set remote
3510 hardware-breakpoint-limit}.
3513 @item thbreak @var{args}
3514 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3515 are the same as for the @code{hbreak} command and the breakpoint is set in
3516 the same way. However, like the @code{tbreak} command,
3517 the breakpoint is automatically deleted after the
3518 first time your program stops there. Also, like the @code{hbreak}
3519 command, the breakpoint requires hardware support and some target hardware
3520 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3521 See also @ref{Conditions, ,Break Conditions}.
3524 @cindex regular expression
3525 @cindex breakpoints at functions matching a regexp
3526 @cindex set breakpoints in many functions
3527 @item rbreak @var{regex}
3528 Set breakpoints on all functions matching the regular expression
3529 @var{regex}. This command sets an unconditional breakpoint on all
3530 matches, printing a list of all breakpoints it set. Once these
3531 breakpoints are set, they are treated just like the breakpoints set with
3532 the @code{break} command. You can delete them, disable them, or make
3533 them conditional the same way as any other breakpoint.
3535 The syntax of the regular expression is the standard one used with tools
3536 like @file{grep}. Note that this is different from the syntax used by
3537 shells, so for instance @code{foo*} matches all functions that include
3538 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3539 @code{.*} leading and trailing the regular expression you supply, so to
3540 match only functions that begin with @code{foo}, use @code{^foo}.
3542 @cindex non-member C@t{++} functions, set breakpoint in
3543 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3544 breakpoints on overloaded functions that are not members of any special
3547 @cindex set breakpoints on all functions
3548 The @code{rbreak} command can be used to set breakpoints in
3549 @strong{all} the functions in a program, like this:
3552 (@value{GDBP}) rbreak .
3555 @item rbreak @var{file}:@var{regex}
3556 If @code{rbreak} is called with a filename qualification, it limits
3557 the search for functions matching the given regular expression to the
3558 specified @var{file}. This can be used, for example, to set breakpoints on
3559 every function in a given file:
3562 (@value{GDBP}) rbreak file.c:.
3565 The colon separating the filename qualifier from the regex may
3566 optionally be surrounded by spaces.
3568 @kindex info breakpoints
3569 @cindex @code{$_} and @code{info breakpoints}
3570 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3571 @itemx info break @r{[}@var{n}@dots{}@r{]}
3572 Print a table of all breakpoints, watchpoints, and catchpoints set and
3573 not deleted. Optional argument @var{n} means print information only
3574 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3575 For each breakpoint, following columns are printed:
3578 @item Breakpoint Numbers
3580 Breakpoint, watchpoint, or catchpoint.
3582 Whether the breakpoint is marked to be disabled or deleted when hit.
3583 @item Enabled or Disabled
3584 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3585 that are not enabled.
3587 Where the breakpoint is in your program, as a memory address. For a
3588 pending breakpoint whose address is not yet known, this field will
3589 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3590 library that has the symbol or line referred by breakpoint is loaded.
3591 See below for details. A breakpoint with several locations will
3592 have @samp{<MULTIPLE>} in this field---see below for details.
3594 Where the breakpoint is in the source for your program, as a file and
3595 line number. For a pending breakpoint, the original string passed to
3596 the breakpoint command will be listed as it cannot be resolved until
3597 the appropriate shared library is loaded in the future.
3601 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3602 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3603 @value{GDBN} on the host's side. If it is ``target'', then the condition
3604 is evaluated by the target. The @code{info break} command shows
3605 the condition on the line following the affected breakpoint, together with
3606 its condition evaluation mode in between parentheses.
3608 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3609 allowed to have a condition specified for it. The condition is not parsed for
3610 validity until a shared library is loaded that allows the pending
3611 breakpoint to resolve to a valid location.
3614 @code{info break} with a breakpoint
3615 number @var{n} as argument lists only that breakpoint. The
3616 convenience variable @code{$_} and the default examining-address for
3617 the @code{x} command are set to the address of the last breakpoint
3618 listed (@pxref{Memory, ,Examining Memory}).
3621 @code{info break} displays a count of the number of times the breakpoint
3622 has been hit. This is especially useful in conjunction with the
3623 @code{ignore} command. You can ignore a large number of breakpoint
3624 hits, look at the breakpoint info to see how many times the breakpoint
3625 was hit, and then run again, ignoring one less than that number. This
3626 will get you quickly to the last hit of that breakpoint.
3629 For a breakpoints with an enable count (xref) greater than 1,
3630 @code{info break} also displays that count.
3634 @value{GDBN} allows you to set any number of breakpoints at the same place in
3635 your program. There is nothing silly or meaningless about this. When
3636 the breakpoints are conditional, this is even useful
3637 (@pxref{Conditions, ,Break Conditions}).
3639 @cindex multiple locations, breakpoints
3640 @cindex breakpoints, multiple locations
3641 It is possible that a breakpoint corresponds to several locations
3642 in your program. Examples of this situation are:
3646 Multiple functions in the program may have the same name.
3649 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3650 instances of the function body, used in different cases.
3653 For a C@t{++} template function, a given line in the function can
3654 correspond to any number of instantiations.
3657 For an inlined function, a given source line can correspond to
3658 several places where that function is inlined.
3661 In all those cases, @value{GDBN} will insert a breakpoint at all
3662 the relevant locations.
3664 A breakpoint with multiple locations is displayed in the breakpoint
3665 table using several rows---one header row, followed by one row for
3666 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3667 address column. The rows for individual locations contain the actual
3668 addresses for locations, and show the functions to which those
3669 locations belong. The number column for a location is of the form
3670 @var{breakpoint-number}.@var{location-number}.
3675 Num Type Disp Enb Address What
3676 1 breakpoint keep y <MULTIPLE>
3678 breakpoint already hit 1 time
3679 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3680 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3683 Each location can be individually enabled or disabled by passing
3684 @var{breakpoint-number}.@var{location-number} as argument to the
3685 @code{enable} and @code{disable} commands. Note that you cannot
3686 delete the individual locations from the list, you can only delete the
3687 entire list of locations that belong to their parent breakpoint (with
3688 the @kbd{delete @var{num}} command, where @var{num} is the number of
3689 the parent breakpoint, 1 in the above example). Disabling or enabling
3690 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3691 that belong to that breakpoint.
3693 @cindex pending breakpoints
3694 It's quite common to have a breakpoint inside a shared library.
3695 Shared libraries can be loaded and unloaded explicitly,
3696 and possibly repeatedly, as the program is executed. To support
3697 this use case, @value{GDBN} updates breakpoint locations whenever
3698 any shared library is loaded or unloaded. Typically, you would
3699 set a breakpoint in a shared library at the beginning of your
3700 debugging session, when the library is not loaded, and when the
3701 symbols from the library are not available. When you try to set
3702 breakpoint, @value{GDBN} will ask you if you want to set
3703 a so called @dfn{pending breakpoint}---breakpoint whose address
3704 is not yet resolved.
3706 After the program is run, whenever a new shared library is loaded,
3707 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3708 shared library contains the symbol or line referred to by some
3709 pending breakpoint, that breakpoint is resolved and becomes an
3710 ordinary breakpoint. When a library is unloaded, all breakpoints
3711 that refer to its symbols or source lines become pending again.
3713 This logic works for breakpoints with multiple locations, too. For
3714 example, if you have a breakpoint in a C@t{++} template function, and
3715 a newly loaded shared library has an instantiation of that template,
3716 a new location is added to the list of locations for the breakpoint.
3718 Except for having unresolved address, pending breakpoints do not
3719 differ from regular breakpoints. You can set conditions or commands,
3720 enable and disable them and perform other breakpoint operations.
3722 @value{GDBN} provides some additional commands for controlling what
3723 happens when the @samp{break} command cannot resolve breakpoint
3724 address specification to an address:
3726 @kindex set breakpoint pending
3727 @kindex show breakpoint pending
3729 @item set breakpoint pending auto
3730 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3731 location, it queries you whether a pending breakpoint should be created.
3733 @item set breakpoint pending on
3734 This indicates that an unrecognized breakpoint location should automatically
3735 result in a pending breakpoint being created.
3737 @item set breakpoint pending off
3738 This indicates that pending breakpoints are not to be created. Any
3739 unrecognized breakpoint location results in an error. This setting does
3740 not affect any pending breakpoints previously created.
3742 @item show breakpoint pending
3743 Show the current behavior setting for creating pending breakpoints.
3746 The settings above only affect the @code{break} command and its
3747 variants. Once breakpoint is set, it will be automatically updated
3748 as shared libraries are loaded and unloaded.
3750 @cindex automatic hardware breakpoints
3751 For some targets, @value{GDBN} can automatically decide if hardware or
3752 software breakpoints should be used, depending on whether the
3753 breakpoint address is read-only or read-write. This applies to
3754 breakpoints set with the @code{break} command as well as to internal
3755 breakpoints set by commands like @code{next} and @code{finish}. For
3756 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3759 You can control this automatic behaviour with the following commands::
3761 @kindex set breakpoint auto-hw
3762 @kindex show breakpoint auto-hw
3764 @item set breakpoint auto-hw on
3765 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3766 will try to use the target memory map to decide if software or hardware
3767 breakpoint must be used.
3769 @item set breakpoint auto-hw off
3770 This indicates @value{GDBN} should not automatically select breakpoint
3771 type. If the target provides a memory map, @value{GDBN} will warn when
3772 trying to set software breakpoint at a read-only address.
3775 @value{GDBN} normally implements breakpoints by replacing the program code
3776 at the breakpoint address with a special instruction, which, when
3777 executed, given control to the debugger. By default, the program
3778 code is so modified only when the program is resumed. As soon as
3779 the program stops, @value{GDBN} restores the original instructions. This
3780 behaviour guards against leaving breakpoints inserted in the
3781 target should gdb abrubptly disconnect. However, with slow remote
3782 targets, inserting and removing breakpoint can reduce the performance.
3783 This behavior can be controlled with the following commands::
3785 @kindex set breakpoint always-inserted
3786 @kindex show breakpoint always-inserted
3788 @item set breakpoint always-inserted off
3789 All breakpoints, including newly added by the user, are inserted in
3790 the target only when the target is resumed. All breakpoints are
3791 removed from the target when it stops.
3793 @item set breakpoint always-inserted on
3794 Causes all breakpoints to be inserted in the target at all times. If
3795 the user adds a new breakpoint, or changes an existing breakpoint, the
3796 breakpoints in the target are updated immediately. A breakpoint is
3797 removed from the target only when breakpoint itself is removed.
3799 @cindex non-stop mode, and @code{breakpoint always-inserted}
3800 @item set breakpoint always-inserted auto
3801 This is the default mode. If @value{GDBN} is controlling the inferior
3802 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3803 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3804 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3805 @code{breakpoint always-inserted} mode is off.
3808 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3809 when a breakpoint breaks. If the condition is true, then the process being
3810 debugged stops, otherwise the process is resumed.
3812 If the target supports evaluating conditions on its end, @value{GDBN} may
3813 download the breakpoint, together with its conditions, to it.
3815 This feature can be controlled via the following commands:
3817 @kindex set breakpoint condition-evaluation
3818 @kindex show breakpoint condition-evaluation
3820 @item set breakpoint condition-evaluation host
3821 This option commands @value{GDBN} to evaluate the breakpoint
3822 conditions on the host's side. Unconditional breakpoints are sent to
3823 the target which in turn receives the triggers and reports them back to GDB
3824 for condition evaluation. This is the standard evaluation mode.
3826 @item set breakpoint condition-evaluation target
3827 This option commands @value{GDBN} to download breakpoint conditions
3828 to the target at the moment of their insertion. The target
3829 is responsible for evaluating the conditional expression and reporting
3830 breakpoint stop events back to @value{GDBN} whenever the condition
3831 is true. Due to limitations of target-side evaluation, some conditions
3832 cannot be evaluated there, e.g., conditions that depend on local data
3833 that is only known to the host. Examples include
3834 conditional expressions involving convenience variables, complex types
3835 that cannot be handled by the agent expression parser and expressions
3836 that are too long to be sent over to the target, specially when the
3837 target is a remote system. In these cases, the conditions will be
3838 evaluated by @value{GDBN}.
3840 @item set breakpoint condition-evaluation auto
3841 This is the default mode. If the target supports evaluating breakpoint
3842 conditions on its end, @value{GDBN} will download breakpoint conditions to
3843 the target (limitations mentioned previously apply). If the target does
3844 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3845 to evaluating all these conditions on the host's side.
3849 @cindex negative breakpoint numbers
3850 @cindex internal @value{GDBN} breakpoints
3851 @value{GDBN} itself sometimes sets breakpoints in your program for
3852 special purposes, such as proper handling of @code{longjmp} (in C
3853 programs). These internal breakpoints are assigned negative numbers,
3854 starting with @code{-1}; @samp{info breakpoints} does not display them.
3855 You can see these breakpoints with the @value{GDBN} maintenance command
3856 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3859 @node Set Watchpoints
3860 @subsection Setting Watchpoints
3862 @cindex setting watchpoints
3863 You can use a watchpoint to stop execution whenever the value of an
3864 expression changes, without having to predict a particular place where
3865 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3866 The expression may be as simple as the value of a single variable, or
3867 as complex as many variables combined by operators. Examples include:
3871 A reference to the value of a single variable.
3874 An address cast to an appropriate data type. For example,
3875 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3876 address (assuming an @code{int} occupies 4 bytes).
3879 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3880 expression can use any operators valid in the program's native
3881 language (@pxref{Languages}).
3884 You can set a watchpoint on an expression even if the expression can
3885 not be evaluated yet. For instance, you can set a watchpoint on
3886 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3887 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3888 the expression produces a valid value. If the expression becomes
3889 valid in some other way than changing a variable (e.g.@: if the memory
3890 pointed to by @samp{*global_ptr} becomes readable as the result of a
3891 @code{malloc} call), @value{GDBN} may not stop until the next time
3892 the expression changes.
3894 @cindex software watchpoints
3895 @cindex hardware watchpoints
3896 Depending on your system, watchpoints may be implemented in software or
3897 hardware. @value{GDBN} does software watchpointing by single-stepping your
3898 program and testing the variable's value each time, which is hundreds of
3899 times slower than normal execution. (But this may still be worth it, to
3900 catch errors where you have no clue what part of your program is the
3903 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3904 x86-based targets, @value{GDBN} includes support for hardware
3905 watchpoints, which do not slow down the running of your program.
3909 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3910 Set a watchpoint for an expression. @value{GDBN} will break when the
3911 expression @var{expr} is written into by the program and its value
3912 changes. The simplest (and the most popular) use of this command is
3913 to watch the value of a single variable:
3916 (@value{GDBP}) watch foo
3919 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3920 argument, @value{GDBN} breaks only when the thread identified by
3921 @var{threadnum} changes the value of @var{expr}. If any other threads
3922 change the value of @var{expr}, @value{GDBN} will not break. Note
3923 that watchpoints restricted to a single thread in this way only work
3924 with Hardware Watchpoints.
3926 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3927 (see below). The @code{-location} argument tells @value{GDBN} to
3928 instead watch the memory referred to by @var{expr}. In this case,
3929 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3930 and watch the memory at that address. The type of the result is used
3931 to determine the size of the watched memory. If the expression's
3932 result does not have an address, then @value{GDBN} will print an
3935 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3936 of masked watchpoints, if the current architecture supports this
3937 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3938 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3939 to an address to watch. The mask specifies that some bits of an address
3940 (the bits which are reset in the mask) should be ignored when matching
3941 the address accessed by the inferior against the watchpoint address.
3942 Thus, a masked watchpoint watches many addresses simultaneously---those
3943 addresses whose unmasked bits are identical to the unmasked bits in the
3944 watchpoint address. The @code{mask} argument implies @code{-location}.
3948 (@value{GDBP}) watch foo mask 0xffff00ff
3949 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3953 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3954 Set a watchpoint that will break when the value of @var{expr} is read
3958 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3959 Set a watchpoint that will break when @var{expr} is either read from
3960 or written into by the program.
3962 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3963 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3964 This command prints a list of watchpoints, using the same format as
3965 @code{info break} (@pxref{Set Breaks}).
3968 If you watch for a change in a numerically entered address you need to
3969 dereference it, as the address itself is just a constant number which will
3970 never change. @value{GDBN} refuses to create a watchpoint that watches
3971 a never-changing value:
3974 (@value{GDBP}) watch 0x600850
3975 Cannot watch constant value 0x600850.
3976 (@value{GDBP}) watch *(int *) 0x600850
3977 Watchpoint 1: *(int *) 6293584
3980 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3981 watchpoints execute very quickly, and the debugger reports a change in
3982 value at the exact instruction where the change occurs. If @value{GDBN}
3983 cannot set a hardware watchpoint, it sets a software watchpoint, which
3984 executes more slowly and reports the change in value at the next
3985 @emph{statement}, not the instruction, after the change occurs.
3987 @cindex use only software watchpoints
3988 You can force @value{GDBN} to use only software watchpoints with the
3989 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3990 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3991 the underlying system supports them. (Note that hardware-assisted
3992 watchpoints that were set @emph{before} setting
3993 @code{can-use-hw-watchpoints} to zero will still use the hardware
3994 mechanism of watching expression values.)
3997 @item set can-use-hw-watchpoints
3998 @kindex set can-use-hw-watchpoints
3999 Set whether or not to use hardware watchpoints.
4001 @item show can-use-hw-watchpoints
4002 @kindex show can-use-hw-watchpoints
4003 Show the current mode of using hardware watchpoints.
4006 For remote targets, you can restrict the number of hardware
4007 watchpoints @value{GDBN} will use, see @ref{set remote
4008 hardware-breakpoint-limit}.
4010 When you issue the @code{watch} command, @value{GDBN} reports
4013 Hardware watchpoint @var{num}: @var{expr}
4017 if it was able to set a hardware watchpoint.
4019 Currently, the @code{awatch} and @code{rwatch} commands can only set
4020 hardware watchpoints, because accesses to data that don't change the
4021 value of the watched expression cannot be detected without examining
4022 every instruction as it is being executed, and @value{GDBN} does not do
4023 that currently. If @value{GDBN} finds that it is unable to set a
4024 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4025 will print a message like this:
4028 Expression cannot be implemented with read/access watchpoint.
4031 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4032 data type of the watched expression is wider than what a hardware
4033 watchpoint on the target machine can handle. For example, some systems
4034 can only watch regions that are up to 4 bytes wide; on such systems you
4035 cannot set hardware watchpoints for an expression that yields a
4036 double-precision floating-point number (which is typically 8 bytes
4037 wide). As a work-around, it might be possible to break the large region
4038 into a series of smaller ones and watch them with separate watchpoints.
4040 If you set too many hardware watchpoints, @value{GDBN} might be unable
4041 to insert all of them when you resume the execution of your program.
4042 Since the precise number of active watchpoints is unknown until such
4043 time as the program is about to be resumed, @value{GDBN} might not be
4044 able to warn you about this when you set the watchpoints, and the
4045 warning will be printed only when the program is resumed:
4048 Hardware watchpoint @var{num}: Could not insert watchpoint
4052 If this happens, delete or disable some of the watchpoints.
4054 Watching complex expressions that reference many variables can also
4055 exhaust the resources available for hardware-assisted watchpoints.
4056 That's because @value{GDBN} needs to watch every variable in the
4057 expression with separately allocated resources.
4059 If you call a function interactively using @code{print} or @code{call},
4060 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4061 kind of breakpoint or the call completes.
4063 @value{GDBN} automatically deletes watchpoints that watch local
4064 (automatic) variables, or expressions that involve such variables, when
4065 they go out of scope, that is, when the execution leaves the block in
4066 which these variables were defined. In particular, when the program
4067 being debugged terminates, @emph{all} local variables go out of scope,
4068 and so only watchpoints that watch global variables remain set. If you
4069 rerun the program, you will need to set all such watchpoints again. One
4070 way of doing that would be to set a code breakpoint at the entry to the
4071 @code{main} function and when it breaks, set all the watchpoints.
4073 @cindex watchpoints and threads
4074 @cindex threads and watchpoints
4075 In multi-threaded programs, watchpoints will detect changes to the
4076 watched expression from every thread.
4079 @emph{Warning:} In multi-threaded programs, software watchpoints
4080 have only limited usefulness. If @value{GDBN} creates a software
4081 watchpoint, it can only watch the value of an expression @emph{in a
4082 single thread}. If you are confident that the expression can only
4083 change due to the current thread's activity (and if you are also
4084 confident that no other thread can become current), then you can use
4085 software watchpoints as usual. However, @value{GDBN} may not notice
4086 when a non-current thread's activity changes the expression. (Hardware
4087 watchpoints, in contrast, watch an expression in all threads.)
4090 @xref{set remote hardware-watchpoint-limit}.
4092 @node Set Catchpoints
4093 @subsection Setting Catchpoints
4094 @cindex catchpoints, setting
4095 @cindex exception handlers
4096 @cindex event handling
4098 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4099 kinds of program events, such as C@t{++} exceptions or the loading of a
4100 shared library. Use the @code{catch} command to set a catchpoint.
4104 @item catch @var{event}
4105 Stop when @var{event} occurs. @var{event} can be any of the following:
4108 @item throw @r{[}@var{regexp}@r{]}
4109 @itemx rethrow @r{[}@var{regexp}@r{]}
4110 @itemx catch @r{[}@var{regexp}@r{]}
4111 @cindex stop on C@t{++} exceptions
4112 The throwing, re-throwing, or catching of a C@t{++} exception.
4114 If @var{regexp} is given, then only exceptions whose type matches the
4115 regular expression will be caught.
4117 @vindex $_exception@r{, convenience variable}
4118 The convenience variable @code{$_exception} is available at an
4119 exception-related catchpoint, on some systems. This holds the
4120 exception being thrown.
4122 There are currently some limitations to C@t{++} exception handling in
4127 The support for these commands is system-dependent. Currently, only
4128 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4132 The regular expression feature and the @code{$_exception} convenience
4133 variable rely on the presence of some SDT probes in @code{libstdc++}.
4134 If these probes are not present, then these features cannot be used.
4135 These probes were first available in the GCC 4.8 release, but whether
4136 or not they are available in your GCC also depends on how it was
4140 The @code{$_exception} convenience variable is only valid at the
4141 instruction at which an exception-related catchpoint is set.
4144 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4145 location in the system library which implements runtime exception
4146 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4147 (@pxref{Selection}) to get to your code.
4150 If you call a function interactively, @value{GDBN} normally returns
4151 control to you when the function has finished executing. If the call
4152 raises an exception, however, the call may bypass the mechanism that
4153 returns control to you and cause your program either to abort or to
4154 simply continue running until it hits a breakpoint, catches a signal
4155 that @value{GDBN} is listening for, or exits. This is the case even if
4156 you set a catchpoint for the exception; catchpoints on exceptions are
4157 disabled within interactive calls. @xref{Calling}, for information on
4158 controlling this with @code{set unwind-on-terminating-exception}.
4161 You cannot raise an exception interactively.
4164 You cannot install an exception handler interactively.
4168 @cindex Ada exception catching
4169 @cindex catch Ada exceptions
4170 An Ada exception being raised. If an exception name is specified
4171 at the end of the command (eg @code{catch exception Program_Error}),
4172 the debugger will stop only when this specific exception is raised.
4173 Otherwise, the debugger stops execution when any Ada exception is raised.
4175 When inserting an exception catchpoint on a user-defined exception whose
4176 name is identical to one of the exceptions defined by the language, the
4177 fully qualified name must be used as the exception name. Otherwise,
4178 @value{GDBN} will assume that it should stop on the pre-defined exception
4179 rather than the user-defined one. For instance, assuming an exception
4180 called @code{Constraint_Error} is defined in package @code{Pck}, then
4181 the command to use to catch such exceptions is @kbd{catch exception
4182 Pck.Constraint_Error}.
4184 @item exception unhandled
4185 An exception that was raised but is not handled by the program.
4188 A failed Ada assertion.
4191 @cindex break on fork/exec
4192 A call to @code{exec}. This is currently only available for HP-UX
4196 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4197 @cindex break on a system call.
4198 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4199 syscall is a mechanism for application programs to request a service
4200 from the operating system (OS) or one of the OS system services.
4201 @value{GDBN} can catch some or all of the syscalls issued by the
4202 debuggee, and show the related information for each syscall. If no
4203 argument is specified, calls to and returns from all system calls
4206 @var{name} can be any system call name that is valid for the
4207 underlying OS. Just what syscalls are valid depends on the OS. On
4208 GNU and Unix systems, you can find the full list of valid syscall
4209 names on @file{/usr/include/asm/unistd.h}.
4211 @c For MS-Windows, the syscall names and the corresponding numbers
4212 @c can be found, e.g., on this URL:
4213 @c http://www.metasploit.com/users/opcode/syscalls.html
4214 @c but we don't support Windows syscalls yet.
4216 Normally, @value{GDBN} knows in advance which syscalls are valid for
4217 each OS, so you can use the @value{GDBN} command-line completion
4218 facilities (@pxref{Completion,, command completion}) to list the
4221 You may also specify the system call numerically. A syscall's
4222 number is the value passed to the OS's syscall dispatcher to
4223 identify the requested service. When you specify the syscall by its
4224 name, @value{GDBN} uses its database of syscalls to convert the name
4225 into the corresponding numeric code, but using the number directly
4226 may be useful if @value{GDBN}'s database does not have the complete
4227 list of syscalls on your system (e.g., because @value{GDBN} lags
4228 behind the OS upgrades).
4230 The example below illustrates how this command works if you don't provide
4234 (@value{GDBP}) catch syscall
4235 Catchpoint 1 (syscall)
4237 Starting program: /tmp/catch-syscall
4239 Catchpoint 1 (call to syscall 'close'), \
4240 0xffffe424 in __kernel_vsyscall ()
4244 Catchpoint 1 (returned from syscall 'close'), \
4245 0xffffe424 in __kernel_vsyscall ()
4249 Here is an example of catching a system call by name:
4252 (@value{GDBP}) catch syscall chroot
4253 Catchpoint 1 (syscall 'chroot' [61])
4255 Starting program: /tmp/catch-syscall
4257 Catchpoint 1 (call to syscall 'chroot'), \
4258 0xffffe424 in __kernel_vsyscall ()
4262 Catchpoint 1 (returned from syscall 'chroot'), \
4263 0xffffe424 in __kernel_vsyscall ()
4267 An example of specifying a system call numerically. In the case
4268 below, the syscall number has a corresponding entry in the XML
4269 file, so @value{GDBN} finds its name and prints it:
4272 (@value{GDBP}) catch syscall 252
4273 Catchpoint 1 (syscall(s) 'exit_group')
4275 Starting program: /tmp/catch-syscall
4277 Catchpoint 1 (call to syscall 'exit_group'), \
4278 0xffffe424 in __kernel_vsyscall ()
4282 Program exited normally.
4286 However, there can be situations when there is no corresponding name
4287 in XML file for that syscall number. In this case, @value{GDBN} prints
4288 a warning message saying that it was not able to find the syscall name,
4289 but the catchpoint will be set anyway. See the example below:
4292 (@value{GDBP}) catch syscall 764
4293 warning: The number '764' does not represent a known syscall.
4294 Catchpoint 2 (syscall 764)
4298 If you configure @value{GDBN} using the @samp{--without-expat} option,
4299 it will not be able to display syscall names. Also, if your
4300 architecture does not have an XML file describing its system calls,
4301 you will not be able to see the syscall names. It is important to
4302 notice that these two features are used for accessing the syscall
4303 name database. In either case, you will see a warning like this:
4306 (@value{GDBP}) catch syscall
4307 warning: Could not open "syscalls/i386-linux.xml"
4308 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4309 GDB will not be able to display syscall names.
4310 Catchpoint 1 (syscall)
4314 Of course, the file name will change depending on your architecture and system.
4316 Still using the example above, you can also try to catch a syscall by its
4317 number. In this case, you would see something like:
4320 (@value{GDBP}) catch syscall 252
4321 Catchpoint 1 (syscall(s) 252)
4324 Again, in this case @value{GDBN} would not be able to display syscall's names.
4327 A call to @code{fork}. This is currently only available for HP-UX
4331 A call to @code{vfork}. This is currently only available for HP-UX
4334 @item load @r{[}regexp@r{]}
4335 @itemx unload @r{[}regexp@r{]}
4336 The loading or unloading of a shared library. If @var{regexp} is
4337 given, then the catchpoint will stop only if the regular expression
4338 matches one of the affected libraries.
4340 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4341 The delivery of a signal.
4343 With no arguments, this catchpoint will catch any signal that is not
4344 used internally by @value{GDBN}, specifically, all signals except
4345 @samp{SIGTRAP} and @samp{SIGINT}.
4347 With the argument @samp{all}, all signals, including those used by
4348 @value{GDBN}, will be caught. This argument cannot be used with other
4351 Otherwise, the arguments are a list of signal names as given to
4352 @code{handle} (@pxref{Signals}). Only signals specified in this list
4355 One reason that @code{catch signal} can be more useful than
4356 @code{handle} is that you can attach commands and conditions to the
4359 When a signal is caught by a catchpoint, the signal's @code{stop} and
4360 @code{print} settings, as specified by @code{handle}, are ignored.
4361 However, whether the signal is still delivered to the inferior depends
4362 on the @code{pass} setting; this can be changed in the catchpoint's
4367 @item tcatch @var{event}
4368 Set a catchpoint that is enabled only for one stop. The catchpoint is
4369 automatically deleted after the first time the event is caught.
4373 Use the @code{info break} command to list the current catchpoints.
4377 @subsection Deleting Breakpoints
4379 @cindex clearing breakpoints, watchpoints, catchpoints
4380 @cindex deleting breakpoints, watchpoints, catchpoints
4381 It is often necessary to eliminate a breakpoint, watchpoint, or
4382 catchpoint once it has done its job and you no longer want your program
4383 to stop there. This is called @dfn{deleting} the breakpoint. A
4384 breakpoint that has been deleted no longer exists; it is forgotten.
4386 With the @code{clear} command you can delete breakpoints according to
4387 where they are in your program. With the @code{delete} command you can
4388 delete individual breakpoints, watchpoints, or catchpoints by specifying
4389 their breakpoint numbers.
4391 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4392 automatically ignores breakpoints on the first instruction to be executed
4393 when you continue execution without changing the execution address.
4398 Delete any breakpoints at the next instruction to be executed in the
4399 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4400 the innermost frame is selected, this is a good way to delete a
4401 breakpoint where your program just stopped.
4403 @item clear @var{location}
4404 Delete any breakpoints set at the specified @var{location}.
4405 @xref{Specify Location}, for the various forms of @var{location}; the
4406 most useful ones are listed below:
4409 @item clear @var{function}
4410 @itemx clear @var{filename}:@var{function}
4411 Delete any breakpoints set at entry to the named @var{function}.
4413 @item clear @var{linenum}
4414 @itemx clear @var{filename}:@var{linenum}
4415 Delete any breakpoints set at or within the code of the specified
4416 @var{linenum} of the specified @var{filename}.
4419 @cindex delete breakpoints
4421 @kindex d @r{(@code{delete})}
4422 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4423 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4424 ranges specified as arguments. If no argument is specified, delete all
4425 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4426 confirm off}). You can abbreviate this command as @code{d}.
4430 @subsection Disabling Breakpoints
4432 @cindex enable/disable a breakpoint
4433 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4434 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4435 it had been deleted, but remembers the information on the breakpoint so
4436 that you can @dfn{enable} it again later.
4438 You disable and enable breakpoints, watchpoints, and catchpoints with
4439 the @code{enable} and @code{disable} commands, optionally specifying
4440 one or more breakpoint numbers as arguments. Use @code{info break} to
4441 print a list of all breakpoints, watchpoints, and catchpoints if you
4442 do not know which numbers to use.
4444 Disabling and enabling a breakpoint that has multiple locations
4445 affects all of its locations.
4447 A breakpoint, watchpoint, or catchpoint can have any of several
4448 different states of enablement:
4452 Enabled. The breakpoint stops your program. A breakpoint set
4453 with the @code{break} command starts out in this state.
4455 Disabled. The breakpoint has no effect on your program.
4457 Enabled once. The breakpoint stops your program, but then becomes
4460 Enabled for a count. The breakpoint stops your program for the next
4461 N times, then becomes disabled.
4463 Enabled for deletion. The breakpoint stops your program, but
4464 immediately after it does so it is deleted permanently. A breakpoint
4465 set with the @code{tbreak} command starts out in this state.
4468 You can use the following commands to enable or disable breakpoints,
4469 watchpoints, and catchpoints:
4473 @kindex dis @r{(@code{disable})}
4474 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4475 Disable the specified breakpoints---or all breakpoints, if none are
4476 listed. A disabled breakpoint has no effect but is not forgotten. All
4477 options such as ignore-counts, conditions and commands are remembered in
4478 case the breakpoint is enabled again later. You may abbreviate
4479 @code{disable} as @code{dis}.
4482 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4483 Enable the specified breakpoints (or all defined breakpoints). They
4484 become effective once again in stopping your program.
4486 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4487 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4488 of these breakpoints immediately after stopping your program.
4490 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4491 Enable the specified breakpoints temporarily. @value{GDBN} records
4492 @var{count} with each of the specified breakpoints, and decrements a
4493 breakpoint's count when it is hit. When any count reaches 0,
4494 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4495 count (@pxref{Conditions, ,Break Conditions}), that will be
4496 decremented to 0 before @var{count} is affected.
4498 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4499 Enable the specified breakpoints to work once, then die. @value{GDBN}
4500 deletes any of these breakpoints as soon as your program stops there.
4501 Breakpoints set by the @code{tbreak} command start out in this state.
4504 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4505 @c confusing: tbreak is also initially enabled.
4506 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4507 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4508 subsequently, they become disabled or enabled only when you use one of
4509 the commands above. (The command @code{until} can set and delete a
4510 breakpoint of its own, but it does not change the state of your other
4511 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4515 @subsection Break Conditions
4516 @cindex conditional breakpoints
4517 @cindex breakpoint conditions
4519 @c FIXME what is scope of break condition expr? Context where wanted?
4520 @c in particular for a watchpoint?
4521 The simplest sort of breakpoint breaks every time your program reaches a
4522 specified place. You can also specify a @dfn{condition} for a
4523 breakpoint. A condition is just a Boolean expression in your
4524 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4525 a condition evaluates the expression each time your program reaches it,
4526 and your program stops only if the condition is @emph{true}.
4528 This is the converse of using assertions for program validation; in that
4529 situation, you want to stop when the assertion is violated---that is,
4530 when the condition is false. In C, if you want to test an assertion expressed
4531 by the condition @var{assert}, you should set the condition
4532 @samp{! @var{assert}} on the appropriate breakpoint.
4534 Conditions are also accepted for watchpoints; you may not need them,
4535 since a watchpoint is inspecting the value of an expression anyhow---but
4536 it might be simpler, say, to just set a watchpoint on a variable name,
4537 and specify a condition that tests whether the new value is an interesting
4540 Break conditions can have side effects, and may even call functions in
4541 your program. This can be useful, for example, to activate functions
4542 that log program progress, or to use your own print functions to
4543 format special data structures. The effects are completely predictable
4544 unless there is another enabled breakpoint at the same address. (In
4545 that case, @value{GDBN} might see the other breakpoint first and stop your
4546 program without checking the condition of this one.) Note that
4547 breakpoint commands are usually more convenient and flexible than break
4549 purpose of performing side effects when a breakpoint is reached
4550 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4552 Breakpoint conditions can also be evaluated on the target's side if
4553 the target supports it. Instead of evaluating the conditions locally,
4554 @value{GDBN} encodes the expression into an agent expression
4555 (@pxref{Agent Expressions}) suitable for execution on the target,
4556 independently of @value{GDBN}. Global variables become raw memory
4557 locations, locals become stack accesses, and so forth.
4559 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4560 when its condition evaluates to true. This mechanism may provide faster
4561 response times depending on the performance characteristics of the target
4562 since it does not need to keep @value{GDBN} informed about
4563 every breakpoint trigger, even those with false conditions.
4565 Break conditions can be specified when a breakpoint is set, by using
4566 @samp{if} in the arguments to the @code{break} command. @xref{Set
4567 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4568 with the @code{condition} command.
4570 You can also use the @code{if} keyword with the @code{watch} command.
4571 The @code{catch} command does not recognize the @code{if} keyword;
4572 @code{condition} is the only way to impose a further condition on a
4577 @item condition @var{bnum} @var{expression}
4578 Specify @var{expression} as the break condition for breakpoint,
4579 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4580 breakpoint @var{bnum} stops your program only if the value of
4581 @var{expression} is true (nonzero, in C). When you use
4582 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4583 syntactic correctness, and to determine whether symbols in it have
4584 referents in the context of your breakpoint. If @var{expression} uses
4585 symbols not referenced in the context of the breakpoint, @value{GDBN}
4586 prints an error message:
4589 No symbol "foo" in current context.
4594 not actually evaluate @var{expression} at the time the @code{condition}
4595 command (or a command that sets a breakpoint with a condition, like
4596 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4598 @item condition @var{bnum}
4599 Remove the condition from breakpoint number @var{bnum}. It becomes
4600 an ordinary unconditional breakpoint.
4603 @cindex ignore count (of breakpoint)
4604 A special case of a breakpoint condition is to stop only when the
4605 breakpoint has been reached a certain number of times. This is so
4606 useful that there is a special way to do it, using the @dfn{ignore
4607 count} of the breakpoint. Every breakpoint has an ignore count, which
4608 is an integer. Most of the time, the ignore count is zero, and
4609 therefore has no effect. But if your program reaches a breakpoint whose
4610 ignore count is positive, then instead of stopping, it just decrements
4611 the ignore count by one and continues. As a result, if the ignore count
4612 value is @var{n}, the breakpoint does not stop the next @var{n} times
4613 your program reaches it.
4617 @item ignore @var{bnum} @var{count}
4618 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4619 The next @var{count} times the breakpoint is reached, your program's
4620 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4623 To make the breakpoint stop the next time it is reached, specify
4626 When you use @code{continue} to resume execution of your program from a
4627 breakpoint, you can specify an ignore count directly as an argument to
4628 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4629 Stepping,,Continuing and Stepping}.
4631 If a breakpoint has a positive ignore count and a condition, the
4632 condition is not checked. Once the ignore count reaches zero,
4633 @value{GDBN} resumes checking the condition.
4635 You could achieve the effect of the ignore count with a condition such
4636 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4637 is decremented each time. @xref{Convenience Vars, ,Convenience
4641 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4644 @node Break Commands
4645 @subsection Breakpoint Command Lists
4647 @cindex breakpoint commands
4648 You can give any breakpoint (or watchpoint or catchpoint) a series of
4649 commands to execute when your program stops due to that breakpoint. For
4650 example, you might want to print the values of certain expressions, or
4651 enable other breakpoints.
4655 @kindex end@r{ (breakpoint commands)}
4656 @item commands @r{[}@var{range}@dots{}@r{]}
4657 @itemx @dots{} @var{command-list} @dots{}
4659 Specify a list of commands for the given breakpoints. The commands
4660 themselves appear on the following lines. Type a line containing just
4661 @code{end} to terminate the commands.
4663 To remove all commands from a breakpoint, type @code{commands} and
4664 follow it immediately with @code{end}; that is, give no commands.
4666 With no argument, @code{commands} refers to the last breakpoint,
4667 watchpoint, or catchpoint set (not to the breakpoint most recently
4668 encountered). If the most recent breakpoints were set with a single
4669 command, then the @code{commands} will apply to all the breakpoints
4670 set by that command. This applies to breakpoints set by
4671 @code{rbreak}, and also applies when a single @code{break} command
4672 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4676 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4677 disabled within a @var{command-list}.
4679 You can use breakpoint commands to start your program up again. Simply
4680 use the @code{continue} command, or @code{step}, or any other command
4681 that resumes execution.
4683 Any other commands in the command list, after a command that resumes
4684 execution, are ignored. This is because any time you resume execution
4685 (even with a simple @code{next} or @code{step}), you may encounter
4686 another breakpoint---which could have its own command list, leading to
4687 ambiguities about which list to execute.
4690 If the first command you specify in a command list is @code{silent}, the
4691 usual message about stopping at a breakpoint is not printed. This may
4692 be desirable for breakpoints that are to print a specific message and
4693 then continue. If none of the remaining commands print anything, you
4694 see no sign that the breakpoint was reached. @code{silent} is
4695 meaningful only at the beginning of a breakpoint command list.
4697 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4698 print precisely controlled output, and are often useful in silent
4699 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4701 For example, here is how you could use breakpoint commands to print the
4702 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4708 printf "x is %d\n",x
4713 One application for breakpoint commands is to compensate for one bug so
4714 you can test for another. Put a breakpoint just after the erroneous line
4715 of code, give it a condition to detect the case in which something
4716 erroneous has been done, and give it commands to assign correct values
4717 to any variables that need them. End with the @code{continue} command
4718 so that your program does not stop, and start with the @code{silent}
4719 command so that no output is produced. Here is an example:
4730 @node Dynamic Printf
4731 @subsection Dynamic Printf
4733 @cindex dynamic printf
4735 The dynamic printf command @code{dprintf} combines a breakpoint with
4736 formatted printing of your program's data to give you the effect of
4737 inserting @code{printf} calls into your program on-the-fly, without
4738 having to recompile it.
4740 In its most basic form, the output goes to the GDB console. However,
4741 you can set the variable @code{dprintf-style} for alternate handling.
4742 For instance, you can ask to format the output by calling your
4743 program's @code{printf} function. This has the advantage that the
4744 characters go to the program's output device, so they can recorded in
4745 redirects to files and so forth.
4747 If you are doing remote debugging with a stub or agent, you can also
4748 ask to have the printf handled by the remote agent. In addition to
4749 ensuring that the output goes to the remote program's device along
4750 with any other output the program might produce, you can also ask that
4751 the dprintf remain active even after disconnecting from the remote
4752 target. Using the stub/agent is also more efficient, as it can do
4753 everything without needing to communicate with @value{GDBN}.
4757 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4758 Whenever execution reaches @var{location}, print the values of one or
4759 more @var{expressions} under the control of the string @var{template}.
4760 To print several values, separate them with commas.
4762 @item set dprintf-style @var{style}
4763 Set the dprintf output to be handled in one of several different
4764 styles enumerated below. A change of style affects all existing
4765 dynamic printfs immediately. (If you need individual control over the
4766 print commands, simply define normal breakpoints with
4767 explicitly-supplied command lists.)
4770 @kindex dprintf-style gdb
4771 Handle the output using the @value{GDBN} @code{printf} command.
4774 @kindex dprintf-style call
4775 Handle the output by calling a function in your program (normally
4779 @kindex dprintf-style agent
4780 Have the remote debugging agent (such as @code{gdbserver}) handle
4781 the output itself. This style is only available for agents that
4782 support running commands on the target.
4784 @item set dprintf-function @var{function}
4785 Set the function to call if the dprintf style is @code{call}. By
4786 default its value is @code{printf}. You may set it to any expression.
4787 that @value{GDBN} can evaluate to a function, as per the @code{call}
4790 @item set dprintf-channel @var{channel}
4791 Set a ``channel'' for dprintf. If set to a non-empty value,
4792 @value{GDBN} will evaluate it as an expression and pass the result as
4793 a first argument to the @code{dprintf-function}, in the manner of
4794 @code{fprintf} and similar functions. Otherwise, the dprintf format
4795 string will be the first argument, in the manner of @code{printf}.
4797 As an example, if you wanted @code{dprintf} output to go to a logfile
4798 that is a standard I/O stream assigned to the variable @code{mylog},
4799 you could do the following:
4802 (gdb) set dprintf-style call
4803 (gdb) set dprintf-function fprintf
4804 (gdb) set dprintf-channel mylog
4805 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4806 Dprintf 1 at 0x123456: file main.c, line 25.
4808 1 dprintf keep y 0x00123456 in main at main.c:25
4809 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4814 Note that the @code{info break} displays the dynamic printf commands
4815 as normal breakpoint commands; you can thus easily see the effect of
4816 the variable settings.
4818 @item set disconnected-dprintf on
4819 @itemx set disconnected-dprintf off
4820 @kindex set disconnected-dprintf
4821 Choose whether @code{dprintf} commands should continue to run if
4822 @value{GDBN} has disconnected from the target. This only applies
4823 if the @code{dprintf-style} is @code{agent}.
4825 @item show disconnected-dprintf off
4826 @kindex show disconnected-dprintf
4827 Show the current choice for disconnected @code{dprintf}.
4831 @value{GDBN} does not check the validity of function and channel,
4832 relying on you to supply values that are meaningful for the contexts
4833 in which they are being used. For instance, the function and channel
4834 may be the values of local variables, but if that is the case, then
4835 all enabled dynamic prints must be at locations within the scope of
4836 those locals. If evaluation fails, @value{GDBN} will report an error.
4838 @node Save Breakpoints
4839 @subsection How to save breakpoints to a file
4841 To save breakpoint definitions to a file use the @w{@code{save
4842 breakpoints}} command.
4845 @kindex save breakpoints
4846 @cindex save breakpoints to a file for future sessions
4847 @item save breakpoints [@var{filename}]
4848 This command saves all current breakpoint definitions together with
4849 their commands and ignore counts, into a file @file{@var{filename}}
4850 suitable for use in a later debugging session. This includes all
4851 types of breakpoints (breakpoints, watchpoints, catchpoints,
4852 tracepoints). To read the saved breakpoint definitions, use the
4853 @code{source} command (@pxref{Command Files}). Note that watchpoints
4854 with expressions involving local variables may fail to be recreated
4855 because it may not be possible to access the context where the
4856 watchpoint is valid anymore. Because the saved breakpoint definitions
4857 are simply a sequence of @value{GDBN} commands that recreate the
4858 breakpoints, you can edit the file in your favorite editing program,
4859 and remove the breakpoint definitions you're not interested in, or
4860 that can no longer be recreated.
4863 @node Static Probe Points
4864 @subsection Static Probe Points
4866 @cindex static probe point, SystemTap
4867 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4868 for Statically Defined Tracing, and the probes are designed to have a tiny
4869 runtime code and data footprint, and no dynamic relocations. They are
4870 usable from assembly, C and C@t{++} languages. See
4871 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4872 for a good reference on how the @acronym{SDT} probes are implemented.
4874 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4875 @acronym{SDT} probes are supported on ELF-compatible systems. See
4876 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4877 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4878 in your applications.
4880 @cindex semaphores on static probe points
4881 Some probes have an associated semaphore variable; for instance, this
4882 happens automatically if you defined your probe using a DTrace-style
4883 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4884 automatically enable it when you specify a breakpoint using the
4885 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4886 location by some other method (e.g., @code{break file:line}), then
4887 @value{GDBN} will not automatically set the semaphore.
4889 You can examine the available static static probes using @code{info
4890 probes}, with optional arguments:
4894 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4895 If given, @var{provider} is a regular expression used to match against provider
4896 names when selecting which probes to list. If omitted, probes by all
4897 probes from all providers are listed.
4899 If given, @var{name} is a regular expression to match against probe names
4900 when selecting which probes to list. If omitted, probe names are not
4901 considered when deciding whether to display them.
4903 If given, @var{objfile} is a regular expression used to select which
4904 object files (executable or shared libraries) to examine. If not
4905 given, all object files are considered.
4907 @item info probes all
4908 List the available static probes, from all types.
4911 @vindex $_probe_arg@r{, convenience variable}
4912 A probe may specify up to twelve arguments. These are available at the
4913 point at which the probe is defined---that is, when the current PC is
4914 at the probe's location. The arguments are available using the
4915 convenience variables (@pxref{Convenience Vars})
4916 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4917 an integer of the appropriate size; types are not preserved. The
4918 convenience variable @code{$_probe_argc} holds the number of arguments
4919 at the current probe point.
4921 These variables are always available, but attempts to access them at
4922 any location other than a probe point will cause @value{GDBN} to give
4926 @c @ifclear BARETARGET
4927 @node Error in Breakpoints
4928 @subsection ``Cannot insert breakpoints''
4930 If you request too many active hardware-assisted breakpoints and
4931 watchpoints, you will see this error message:
4933 @c FIXME: the precise wording of this message may change; the relevant
4934 @c source change is not committed yet (Sep 3, 1999).
4936 Stopped; cannot insert breakpoints.
4937 You may have requested too many hardware breakpoints and watchpoints.
4941 This message is printed when you attempt to resume the program, since
4942 only then @value{GDBN} knows exactly how many hardware breakpoints and
4943 watchpoints it needs to insert.
4945 When this message is printed, you need to disable or remove some of the
4946 hardware-assisted breakpoints and watchpoints, and then continue.
4948 @node Breakpoint-related Warnings
4949 @subsection ``Breakpoint address adjusted...''
4950 @cindex breakpoint address adjusted
4952 Some processor architectures place constraints on the addresses at
4953 which breakpoints may be placed. For architectures thus constrained,
4954 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4955 with the constraints dictated by the architecture.
4957 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4958 a VLIW architecture in which a number of RISC-like instructions may be
4959 bundled together for parallel execution. The FR-V architecture
4960 constrains the location of a breakpoint instruction within such a
4961 bundle to the instruction with the lowest address. @value{GDBN}
4962 honors this constraint by adjusting a breakpoint's address to the
4963 first in the bundle.
4965 It is not uncommon for optimized code to have bundles which contain
4966 instructions from different source statements, thus it may happen that
4967 a breakpoint's address will be adjusted from one source statement to
4968 another. Since this adjustment may significantly alter @value{GDBN}'s
4969 breakpoint related behavior from what the user expects, a warning is
4970 printed when the breakpoint is first set and also when the breakpoint
4973 A warning like the one below is printed when setting a breakpoint
4974 that's been subject to address adjustment:
4977 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4980 Such warnings are printed both for user settable and @value{GDBN}'s
4981 internal breakpoints. If you see one of these warnings, you should
4982 verify that a breakpoint set at the adjusted address will have the
4983 desired affect. If not, the breakpoint in question may be removed and
4984 other breakpoints may be set which will have the desired behavior.
4985 E.g., it may be sufficient to place the breakpoint at a later
4986 instruction. A conditional breakpoint may also be useful in some
4987 cases to prevent the breakpoint from triggering too often.
4989 @value{GDBN} will also issue a warning when stopping at one of these
4990 adjusted breakpoints:
4993 warning: Breakpoint 1 address previously adjusted from 0x00010414
4997 When this warning is encountered, it may be too late to take remedial
4998 action except in cases where the breakpoint is hit earlier or more
4999 frequently than expected.
5001 @node Continuing and Stepping
5002 @section Continuing and Stepping
5006 @cindex resuming execution
5007 @dfn{Continuing} means resuming program execution until your program
5008 completes normally. In contrast, @dfn{stepping} means executing just
5009 one more ``step'' of your program, where ``step'' may mean either one
5010 line of source code, or one machine instruction (depending on what
5011 particular command you use). Either when continuing or when stepping,
5012 your program may stop even sooner, due to a breakpoint or a signal. (If
5013 it stops due to a signal, you may want to use @code{handle}, or use
5014 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
5018 @kindex c @r{(@code{continue})}
5019 @kindex fg @r{(resume foreground execution)}
5020 @item continue @r{[}@var{ignore-count}@r{]}
5021 @itemx c @r{[}@var{ignore-count}@r{]}
5022 @itemx fg @r{[}@var{ignore-count}@r{]}
5023 Resume program execution, at the address where your program last stopped;
5024 any breakpoints set at that address are bypassed. The optional argument
5025 @var{ignore-count} allows you to specify a further number of times to
5026 ignore a breakpoint at this location; its effect is like that of
5027 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5029 The argument @var{ignore-count} is meaningful only when your program
5030 stopped due to a breakpoint. At other times, the argument to
5031 @code{continue} is ignored.
5033 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5034 debugged program is deemed to be the foreground program) are provided
5035 purely for convenience, and have exactly the same behavior as
5039 To resume execution at a different place, you can use @code{return}
5040 (@pxref{Returning, ,Returning from a Function}) to go back to the
5041 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5042 Different Address}) to go to an arbitrary location in your program.
5044 A typical technique for using stepping is to set a breakpoint
5045 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5046 beginning of the function or the section of your program where a problem
5047 is believed to lie, run your program until it stops at that breakpoint,
5048 and then step through the suspect area, examining the variables that are
5049 interesting, until you see the problem happen.
5053 @kindex s @r{(@code{step})}
5055 Continue running your program until control reaches a different source
5056 line, then stop it and return control to @value{GDBN}. This command is
5057 abbreviated @code{s}.
5060 @c "without debugging information" is imprecise; actually "without line
5061 @c numbers in the debugging information". (gcc -g1 has debugging info but
5062 @c not line numbers). But it seems complex to try to make that
5063 @c distinction here.
5064 @emph{Warning:} If you use the @code{step} command while control is
5065 within a function that was compiled without debugging information,
5066 execution proceeds until control reaches a function that does have
5067 debugging information. Likewise, it will not step into a function which
5068 is compiled without debugging information. To step through functions
5069 without debugging information, use the @code{stepi} command, described
5073 The @code{step} command only stops at the first instruction of a source
5074 line. This prevents the multiple stops that could otherwise occur in
5075 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5076 to stop if a function that has debugging information is called within
5077 the line. In other words, @code{step} @emph{steps inside} any functions
5078 called within the line.
5080 Also, the @code{step} command only enters a function if there is line
5081 number information for the function. Otherwise it acts like the
5082 @code{next} command. This avoids problems when using @code{cc -gl}
5083 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5084 was any debugging information about the routine.
5086 @item step @var{count}
5087 Continue running as in @code{step}, but do so @var{count} times. If a
5088 breakpoint is reached, or a signal not related to stepping occurs before
5089 @var{count} steps, stepping stops right away.
5092 @kindex n @r{(@code{next})}
5093 @item next @r{[}@var{count}@r{]}
5094 Continue to the next source line in the current (innermost) stack frame.
5095 This is similar to @code{step}, but function calls that appear within
5096 the line of code are executed without stopping. Execution stops when
5097 control reaches a different line of code at the original stack level
5098 that was executing when you gave the @code{next} command. This command
5099 is abbreviated @code{n}.
5101 An argument @var{count} is a repeat count, as for @code{step}.
5104 @c FIX ME!! Do we delete this, or is there a way it fits in with
5105 @c the following paragraph? --- Vctoria
5107 @c @code{next} within a function that lacks debugging information acts like
5108 @c @code{step}, but any function calls appearing within the code of the
5109 @c function are executed without stopping.
5111 The @code{next} command only stops at the first instruction of a
5112 source line. This prevents multiple stops that could otherwise occur in
5113 @code{switch} statements, @code{for} loops, etc.
5115 @kindex set step-mode
5117 @cindex functions without line info, and stepping
5118 @cindex stepping into functions with no line info
5119 @itemx set step-mode on
5120 The @code{set step-mode on} command causes the @code{step} command to
5121 stop at the first instruction of a function which contains no debug line
5122 information rather than stepping over it.
5124 This is useful in cases where you may be interested in inspecting the
5125 machine instructions of a function which has no symbolic info and do not
5126 want @value{GDBN} to automatically skip over this function.
5128 @item set step-mode off
5129 Causes the @code{step} command to step over any functions which contains no
5130 debug information. This is the default.
5132 @item show step-mode
5133 Show whether @value{GDBN} will stop in or step over functions without
5134 source line debug information.
5137 @kindex fin @r{(@code{finish})}
5139 Continue running until just after function in the selected stack frame
5140 returns. Print the returned value (if any). This command can be
5141 abbreviated as @code{fin}.
5143 Contrast this with the @code{return} command (@pxref{Returning,
5144 ,Returning from a Function}).
5147 @kindex u @r{(@code{until})}
5148 @cindex run until specified location
5151 Continue running until a source line past the current line, in the
5152 current stack frame, is reached. This command is used to avoid single
5153 stepping through a loop more than once. It is like the @code{next}
5154 command, except that when @code{until} encounters a jump, it
5155 automatically continues execution until the program counter is greater
5156 than the address of the jump.
5158 This means that when you reach the end of a loop after single stepping
5159 though it, @code{until} makes your program continue execution until it
5160 exits the loop. In contrast, a @code{next} command at the end of a loop
5161 simply steps back to the beginning of the loop, which forces you to step
5162 through the next iteration.
5164 @code{until} always stops your program if it attempts to exit the current
5167 @code{until} may produce somewhat counterintuitive results if the order
5168 of machine code does not match the order of the source lines. For
5169 example, in the following excerpt from a debugging session, the @code{f}
5170 (@code{frame}) command shows that execution is stopped at line
5171 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5175 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5177 (@value{GDBP}) until
5178 195 for ( ; argc > 0; NEXTARG) @{
5181 This happened because, for execution efficiency, the compiler had
5182 generated code for the loop closure test at the end, rather than the
5183 start, of the loop---even though the test in a C @code{for}-loop is
5184 written before the body of the loop. The @code{until} command appeared
5185 to step back to the beginning of the loop when it advanced to this
5186 expression; however, it has not really gone to an earlier
5187 statement---not in terms of the actual machine code.
5189 @code{until} with no argument works by means of single
5190 instruction stepping, and hence is slower than @code{until} with an
5193 @item until @var{location}
5194 @itemx u @var{location}
5195 Continue running your program until either the specified location is
5196 reached, or the current stack frame returns. @var{location} is any of
5197 the forms described in @ref{Specify Location}.
5198 This form of the command uses temporary breakpoints, and
5199 hence is quicker than @code{until} without an argument. The specified
5200 location is actually reached only if it is in the current frame. This
5201 implies that @code{until} can be used to skip over recursive function
5202 invocations. For instance in the code below, if the current location is
5203 line @code{96}, issuing @code{until 99} will execute the program up to
5204 line @code{99} in the same invocation of factorial, i.e., after the inner
5205 invocations have returned.
5208 94 int factorial (int value)
5210 96 if (value > 1) @{
5211 97 value *= factorial (value - 1);
5218 @kindex advance @var{location}
5219 @item advance @var{location}
5220 Continue running the program up to the given @var{location}. An argument is
5221 required, which should be of one of the forms described in
5222 @ref{Specify Location}.
5223 Execution will also stop upon exit from the current stack
5224 frame. This command is similar to @code{until}, but @code{advance} will
5225 not skip over recursive function calls, and the target location doesn't
5226 have to be in the same frame as the current one.
5230 @kindex si @r{(@code{stepi})}
5232 @itemx stepi @var{arg}
5234 Execute one machine instruction, then stop and return to the debugger.
5236 It is often useful to do @samp{display/i $pc} when stepping by machine
5237 instructions. This makes @value{GDBN} automatically display the next
5238 instruction to be executed, each time your program stops. @xref{Auto
5239 Display,, Automatic Display}.
5241 An argument is a repeat count, as in @code{step}.
5245 @kindex ni @r{(@code{nexti})}
5247 @itemx nexti @var{arg}
5249 Execute one machine instruction, but if it is a function call,
5250 proceed until the function returns.
5252 An argument is a repeat count, as in @code{next}.
5256 @anchor{range stepping}
5257 @cindex range stepping
5258 @cindex target-assisted range stepping
5259 By default, and if available, @value{GDBN} makes use of
5260 target-assisted @dfn{range stepping}. In other words, whenever you
5261 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5262 tells the target to step the corresponding range of instruction
5263 addresses instead of issuing multiple single-steps. This speeds up
5264 line stepping, particularly for remote targets. Ideally, there should
5265 be no reason you would want to turn range stepping off. However, it's
5266 possible that a bug in the debug info, a bug in the remote stub (for
5267 remote targets), or even a bug in @value{GDBN} could make line
5268 stepping behave incorrectly when target-assisted range stepping is
5269 enabled. You can use the following command to turn off range stepping
5273 @kindex set range-stepping
5274 @kindex show range-stepping
5275 @item set range-stepping
5276 @itemx show range-stepping
5277 Control whether range stepping is enabled.
5279 If @code{on}, and the target supports it, @value{GDBN} tells the
5280 target to step a range of addresses itself, instead of issuing
5281 multiple single-steps. If @code{off}, @value{GDBN} always issues
5282 single-steps, even if range stepping is supported by the target. The
5283 default is @code{on}.
5287 @node Skipping Over Functions and Files
5288 @section Skipping Over Functions and Files
5289 @cindex skipping over functions and files
5291 The program you are debugging may contain some functions which are
5292 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5293 skip a function or all functions in a file when stepping.
5295 For example, consider the following C function:
5306 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5307 are not interested in stepping through @code{boring}. If you run @code{step}
5308 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5309 step over both @code{foo} and @code{boring}!
5311 One solution is to @code{step} into @code{boring} and use the @code{finish}
5312 command to immediately exit it. But this can become tedious if @code{boring}
5313 is called from many places.
5315 A more flexible solution is to execute @kbd{skip boring}. This instructs
5316 @value{GDBN} never to step into @code{boring}. Now when you execute
5317 @code{step} at line 103, you'll step over @code{boring} and directly into
5320 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5321 example, @code{skip file boring.c}.
5324 @kindex skip function
5325 @item skip @r{[}@var{linespec}@r{]}
5326 @itemx skip function @r{[}@var{linespec}@r{]}
5327 After running this command, the function named by @var{linespec} or the
5328 function containing the line named by @var{linespec} will be skipped over when
5329 stepping. @xref{Specify Location}.
5331 If you do not specify @var{linespec}, the function you're currently debugging
5334 (If you have a function called @code{file} that you want to skip, use
5335 @kbd{skip function file}.)
5338 @item skip file @r{[}@var{filename}@r{]}
5339 After running this command, any function whose source lives in @var{filename}
5340 will be skipped over when stepping.
5342 If you do not specify @var{filename}, functions whose source lives in the file
5343 you're currently debugging will be skipped.
5346 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5347 These are the commands for managing your list of skips:
5351 @item info skip @r{[}@var{range}@r{]}
5352 Print details about the specified skip(s). If @var{range} is not specified,
5353 print a table with details about all functions and files marked for skipping.
5354 @code{info skip} prints the following information about each skip:
5358 A number identifying this skip.
5360 The type of this skip, either @samp{function} or @samp{file}.
5361 @item Enabled or Disabled
5362 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5364 For function skips, this column indicates the address in memory of the function
5365 being skipped. If you've set a function skip on a function which has not yet
5366 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5367 which has the function is loaded, @code{info skip} will show the function's
5370 For file skips, this field contains the filename being skipped. For functions
5371 skips, this field contains the function name and its line number in the file
5372 where it is defined.
5376 @item skip delete @r{[}@var{range}@r{]}
5377 Delete the specified skip(s). If @var{range} is not specified, delete all
5381 @item skip enable @r{[}@var{range}@r{]}
5382 Enable the specified skip(s). If @var{range} is not specified, enable all
5385 @kindex skip disable
5386 @item skip disable @r{[}@var{range}@r{]}
5387 Disable the specified skip(s). If @var{range} is not specified, disable all
5396 A signal is an asynchronous event that can happen in a program. The
5397 operating system defines the possible kinds of signals, and gives each
5398 kind a name and a number. For example, in Unix @code{SIGINT} is the
5399 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5400 @code{SIGSEGV} is the signal a program gets from referencing a place in
5401 memory far away from all the areas in use; @code{SIGALRM} occurs when
5402 the alarm clock timer goes off (which happens only if your program has
5403 requested an alarm).
5405 @cindex fatal signals
5406 Some signals, including @code{SIGALRM}, are a normal part of the
5407 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5408 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5409 program has not specified in advance some other way to handle the signal.
5410 @code{SIGINT} does not indicate an error in your program, but it is normally
5411 fatal so it can carry out the purpose of the interrupt: to kill the program.
5413 @value{GDBN} has the ability to detect any occurrence of a signal in your
5414 program. You can tell @value{GDBN} in advance what to do for each kind of
5417 @cindex handling signals
5418 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5419 @code{SIGALRM} be silently passed to your program
5420 (so as not to interfere with their role in the program's functioning)
5421 but to stop your program immediately whenever an error signal happens.
5422 You can change these settings with the @code{handle} command.
5425 @kindex info signals
5429 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5430 handle each one. You can use this to see the signal numbers of all
5431 the defined types of signals.
5433 @item info signals @var{sig}
5434 Similar, but print information only about the specified signal number.
5436 @code{info handle} is an alias for @code{info signals}.
5438 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5439 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5440 for details about this command.
5443 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5444 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5445 can be the number of a signal or its name (with or without the
5446 @samp{SIG} at the beginning); a list of signal numbers of the form
5447 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5448 known signals. Optional arguments @var{keywords}, described below,
5449 say what change to make.
5453 The keywords allowed by the @code{handle} command can be abbreviated.
5454 Their full names are:
5458 @value{GDBN} should not stop your program when this signal happens. It may
5459 still print a message telling you that the signal has come in.
5462 @value{GDBN} should stop your program when this signal happens. This implies
5463 the @code{print} keyword as well.
5466 @value{GDBN} should print a message when this signal happens.
5469 @value{GDBN} should not mention the occurrence of the signal at all. This
5470 implies the @code{nostop} keyword as well.
5474 @value{GDBN} should allow your program to see this signal; your program
5475 can handle the signal, or else it may terminate if the signal is fatal
5476 and not handled. @code{pass} and @code{noignore} are synonyms.
5480 @value{GDBN} should not allow your program to see this signal.
5481 @code{nopass} and @code{ignore} are synonyms.
5485 When a signal stops your program, the signal is not visible to the
5487 continue. Your program sees the signal then, if @code{pass} is in
5488 effect for the signal in question @emph{at that time}. In other words,
5489 after @value{GDBN} reports a signal, you can use the @code{handle}
5490 command with @code{pass} or @code{nopass} to control whether your
5491 program sees that signal when you continue.
5493 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5494 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5495 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5498 You can also use the @code{signal} command to prevent your program from
5499 seeing a signal, or cause it to see a signal it normally would not see,
5500 or to give it any signal at any time. For example, if your program stopped
5501 due to some sort of memory reference error, you might store correct
5502 values into the erroneous variables and continue, hoping to see more
5503 execution; but your program would probably terminate immediately as
5504 a result of the fatal signal once it saw the signal. To prevent this,
5505 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5508 @cindex extra signal information
5509 @anchor{extra signal information}
5511 On some targets, @value{GDBN} can inspect extra signal information
5512 associated with the intercepted signal, before it is actually
5513 delivered to the program being debugged. This information is exported
5514 by the convenience variable @code{$_siginfo}, and consists of data
5515 that is passed by the kernel to the signal handler at the time of the
5516 receipt of a signal. The data type of the information itself is
5517 target dependent. You can see the data type using the @code{ptype
5518 $_siginfo} command. On Unix systems, it typically corresponds to the
5519 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5522 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5523 referenced address that raised a segmentation fault.
5527 (@value{GDBP}) continue
5528 Program received signal SIGSEGV, Segmentation fault.
5529 0x0000000000400766 in main ()
5531 (@value{GDBP}) ptype $_siginfo
5538 struct @{...@} _kill;
5539 struct @{...@} _timer;
5541 struct @{...@} _sigchld;
5542 struct @{...@} _sigfault;
5543 struct @{...@} _sigpoll;
5546 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5550 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5551 $1 = (void *) 0x7ffff7ff7000
5555 Depending on target support, @code{$_siginfo} may also be writable.
5558 @section Stopping and Starting Multi-thread Programs
5560 @cindex stopped threads
5561 @cindex threads, stopped
5563 @cindex continuing threads
5564 @cindex threads, continuing
5566 @value{GDBN} supports debugging programs with multiple threads
5567 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5568 are two modes of controlling execution of your program within the
5569 debugger. In the default mode, referred to as @dfn{all-stop mode},
5570 when any thread in your program stops (for example, at a breakpoint
5571 or while being stepped), all other threads in the program are also stopped by
5572 @value{GDBN}. On some targets, @value{GDBN} also supports
5573 @dfn{non-stop mode}, in which other threads can continue to run freely while
5574 you examine the stopped thread in the debugger.
5577 * All-Stop Mode:: All threads stop when GDB takes control
5578 * Non-Stop Mode:: Other threads continue to execute
5579 * Background Execution:: Running your program asynchronously
5580 * Thread-Specific Breakpoints:: Controlling breakpoints
5581 * Interrupted System Calls:: GDB may interfere with system calls
5582 * Observer Mode:: GDB does not alter program behavior
5586 @subsection All-Stop Mode
5588 @cindex all-stop mode
5590 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5591 @emph{all} threads of execution stop, not just the current thread. This
5592 allows you to examine the overall state of the program, including
5593 switching between threads, without worrying that things may change
5596 Conversely, whenever you restart the program, @emph{all} threads start
5597 executing. @emph{This is true even when single-stepping} with commands
5598 like @code{step} or @code{next}.
5600 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5601 Since thread scheduling is up to your debugging target's operating
5602 system (not controlled by @value{GDBN}), other threads may
5603 execute more than one statement while the current thread completes a
5604 single step. Moreover, in general other threads stop in the middle of a
5605 statement, rather than at a clean statement boundary, when the program
5608 You might even find your program stopped in another thread after
5609 continuing or even single-stepping. This happens whenever some other
5610 thread runs into a breakpoint, a signal, or an exception before the
5611 first thread completes whatever you requested.
5613 @cindex automatic thread selection
5614 @cindex switching threads automatically
5615 @cindex threads, automatic switching
5616 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5617 signal, it automatically selects the thread where that breakpoint or
5618 signal happened. @value{GDBN} alerts you to the context switch with a
5619 message such as @samp{[Switching to Thread @var{n}]} to identify the
5622 On some OSes, you can modify @value{GDBN}'s default behavior by
5623 locking the OS scheduler to allow only a single thread to run.
5626 @item set scheduler-locking @var{mode}
5627 @cindex scheduler locking mode
5628 @cindex lock scheduler
5629 Set the scheduler locking mode. If it is @code{off}, then there is no
5630 locking and any thread may run at any time. If @code{on}, then only the
5631 current thread may run when the inferior is resumed. The @code{step}
5632 mode optimizes for single-stepping; it prevents other threads
5633 from preempting the current thread while you are stepping, so that
5634 the focus of debugging does not change unexpectedly.
5635 Other threads only rarely (or never) get a chance to run
5636 when you step. They are more likely to run when you @samp{next} over a
5637 function call, and they are completely free to run when you use commands
5638 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5639 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5640 the current thread away from the thread that you are debugging.
5642 @item show scheduler-locking
5643 Display the current scheduler locking mode.
5646 @cindex resume threads of multiple processes simultaneously
5647 By default, when you issue one of the execution commands such as
5648 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5649 threads of the current inferior to run. For example, if @value{GDBN}
5650 is attached to two inferiors, each with two threads, the
5651 @code{continue} command resumes only the two threads of the current
5652 inferior. This is useful, for example, when you debug a program that
5653 forks and you want to hold the parent stopped (so that, for instance,
5654 it doesn't run to exit), while you debug the child. In other
5655 situations, you may not be interested in inspecting the current state
5656 of any of the processes @value{GDBN} is attached to, and you may want
5657 to resume them all until some breakpoint is hit. In the latter case,
5658 you can instruct @value{GDBN} to allow all threads of all the
5659 inferiors to run with the @w{@code{set schedule-multiple}} command.
5662 @kindex set schedule-multiple
5663 @item set schedule-multiple
5664 Set the mode for allowing threads of multiple processes to be resumed
5665 when an execution command is issued. When @code{on}, all threads of
5666 all processes are allowed to run. When @code{off}, only the threads
5667 of the current process are resumed. The default is @code{off}. The
5668 @code{scheduler-locking} mode takes precedence when set to @code{on},
5669 or while you are stepping and set to @code{step}.
5671 @item show schedule-multiple
5672 Display the current mode for resuming the execution of threads of
5677 @subsection Non-Stop Mode
5679 @cindex non-stop mode
5681 @c This section is really only a place-holder, and needs to be expanded
5682 @c with more details.
5684 For some multi-threaded targets, @value{GDBN} supports an optional
5685 mode of operation in which you can examine stopped program threads in
5686 the debugger while other threads continue to execute freely. This
5687 minimizes intrusion when debugging live systems, such as programs
5688 where some threads have real-time constraints or must continue to
5689 respond to external events. This is referred to as @dfn{non-stop} mode.
5691 In non-stop mode, when a thread stops to report a debugging event,
5692 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5693 threads as well, in contrast to the all-stop mode behavior. Additionally,
5694 execution commands such as @code{continue} and @code{step} apply by default
5695 only to the current thread in non-stop mode, rather than all threads as
5696 in all-stop mode. This allows you to control threads explicitly in
5697 ways that are not possible in all-stop mode --- for example, stepping
5698 one thread while allowing others to run freely, stepping
5699 one thread while holding all others stopped, or stepping several threads
5700 independently and simultaneously.
5702 To enter non-stop mode, use this sequence of commands before you run
5703 or attach to your program:
5706 # Enable the async interface.
5709 # If using the CLI, pagination breaks non-stop.
5712 # Finally, turn it on!
5716 You can use these commands to manipulate the non-stop mode setting:
5719 @kindex set non-stop
5720 @item set non-stop on
5721 Enable selection of non-stop mode.
5722 @item set non-stop off
5723 Disable selection of non-stop mode.
5724 @kindex show non-stop
5726 Show the current non-stop enablement setting.
5729 Note these commands only reflect whether non-stop mode is enabled,
5730 not whether the currently-executing program is being run in non-stop mode.
5731 In particular, the @code{set non-stop} preference is only consulted when
5732 @value{GDBN} starts or connects to the target program, and it is generally
5733 not possible to switch modes once debugging has started. Furthermore,
5734 since not all targets support non-stop mode, even when you have enabled
5735 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5738 In non-stop mode, all execution commands apply only to the current thread
5739 by default. That is, @code{continue} only continues one thread.
5740 To continue all threads, issue @code{continue -a} or @code{c -a}.
5742 You can use @value{GDBN}'s background execution commands
5743 (@pxref{Background Execution}) to run some threads in the background
5744 while you continue to examine or step others from @value{GDBN}.
5745 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5746 always executed asynchronously in non-stop mode.
5748 Suspending execution is done with the @code{interrupt} command when
5749 running in the background, or @kbd{Ctrl-c} during foreground execution.
5750 In all-stop mode, this stops the whole process;
5751 but in non-stop mode the interrupt applies only to the current thread.
5752 To stop the whole program, use @code{interrupt -a}.
5754 Other execution commands do not currently support the @code{-a} option.
5756 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5757 that thread current, as it does in all-stop mode. This is because the
5758 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5759 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5760 changed to a different thread just as you entered a command to operate on the
5761 previously current thread.
5763 @node Background Execution
5764 @subsection Background Execution
5766 @cindex foreground execution
5767 @cindex background execution
5768 @cindex asynchronous execution
5769 @cindex execution, foreground, background and asynchronous
5771 @value{GDBN}'s execution commands have two variants: the normal
5772 foreground (synchronous) behavior, and a background
5773 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5774 the program to report that some thread has stopped before prompting for
5775 another command. In background execution, @value{GDBN} immediately gives
5776 a command prompt so that you can issue other commands while your program runs.
5778 You need to explicitly enable asynchronous mode before you can use
5779 background execution commands. You can use these commands to
5780 manipulate the asynchronous mode setting:
5783 @kindex set target-async
5784 @item set target-async on
5785 Enable asynchronous mode.
5786 @item set target-async off
5787 Disable asynchronous mode.
5788 @kindex show target-async
5789 @item show target-async
5790 Show the current target-async setting.
5793 If the target doesn't support async mode, @value{GDBN} issues an error
5794 message if you attempt to use the background execution commands.
5796 To specify background execution, add a @code{&} to the command. For example,
5797 the background form of the @code{continue} command is @code{continue&}, or
5798 just @code{c&}. The execution commands that accept background execution
5804 @xref{Starting, , Starting your Program}.
5808 @xref{Attach, , Debugging an Already-running Process}.
5812 @xref{Continuing and Stepping, step}.
5816 @xref{Continuing and Stepping, stepi}.
5820 @xref{Continuing and Stepping, next}.
5824 @xref{Continuing and Stepping, nexti}.
5828 @xref{Continuing and Stepping, continue}.
5832 @xref{Continuing and Stepping, finish}.
5836 @xref{Continuing and Stepping, until}.
5840 Background execution is especially useful in conjunction with non-stop
5841 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5842 However, you can also use these commands in the normal all-stop mode with
5843 the restriction that you cannot issue another execution command until the
5844 previous one finishes. Examples of commands that are valid in all-stop
5845 mode while the program is running include @code{help} and @code{info break}.
5847 You can interrupt your program while it is running in the background by
5848 using the @code{interrupt} command.
5855 Suspend execution of the running program. In all-stop mode,
5856 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5857 only the current thread. To stop the whole program in non-stop mode,
5858 use @code{interrupt -a}.
5861 @node Thread-Specific Breakpoints
5862 @subsection Thread-Specific Breakpoints
5864 When your program has multiple threads (@pxref{Threads,, Debugging
5865 Programs with Multiple Threads}), you can choose whether to set
5866 breakpoints on all threads, or on a particular thread.
5869 @cindex breakpoints and threads
5870 @cindex thread breakpoints
5871 @kindex break @dots{} thread @var{threadno}
5872 @item break @var{linespec} thread @var{threadno}
5873 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5874 @var{linespec} specifies source lines; there are several ways of
5875 writing them (@pxref{Specify Location}), but the effect is always to
5876 specify some source line.
5878 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5879 to specify that you only want @value{GDBN} to stop the program when a
5880 particular thread reaches this breakpoint. @var{threadno} is one of the
5881 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5882 column of the @samp{info threads} display.
5884 If you do not specify @samp{thread @var{threadno}} when you set a
5885 breakpoint, the breakpoint applies to @emph{all} threads of your
5888 You can use the @code{thread} qualifier on conditional breakpoints as
5889 well; in this case, place @samp{thread @var{threadno}} before or
5890 after the breakpoint condition, like this:
5893 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5898 Thread-specific breakpoints are automatically deleted when
5899 @value{GDBN} detects the corresponding thread is no longer in the
5900 thread list. For example:
5904 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
5907 There are several ways for a thread to disappear, such as a regular
5908 thread exit, but also when you detach from the process with the
5909 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
5910 Process}), or if @value{GDBN} loses the remote connection
5911 (@pxref{Remote Debugging}), etc. Note that with some targets,
5912 @value{GDBN} is only able to detect a thread has exited when the user
5913 explictly asks for the thread list with the @code{info threads}
5916 @node Interrupted System Calls
5917 @subsection Interrupted System Calls
5919 @cindex thread breakpoints and system calls
5920 @cindex system calls and thread breakpoints
5921 @cindex premature return from system calls
5922 There is an unfortunate side effect when using @value{GDBN} to debug
5923 multi-threaded programs. If one thread stops for a
5924 breakpoint, or for some other reason, and another thread is blocked in a
5925 system call, then the system call may return prematurely. This is a
5926 consequence of the interaction between multiple threads and the signals
5927 that @value{GDBN} uses to implement breakpoints and other events that
5930 To handle this problem, your program should check the return value of
5931 each system call and react appropriately. This is good programming
5934 For example, do not write code like this:
5940 The call to @code{sleep} will return early if a different thread stops
5941 at a breakpoint or for some other reason.
5943 Instead, write this:
5948 unslept = sleep (unslept);
5951 A system call is allowed to return early, so the system is still
5952 conforming to its specification. But @value{GDBN} does cause your
5953 multi-threaded program to behave differently than it would without
5956 Also, @value{GDBN} uses internal breakpoints in the thread library to
5957 monitor certain events such as thread creation and thread destruction.
5958 When such an event happens, a system call in another thread may return
5959 prematurely, even though your program does not appear to stop.
5962 @subsection Observer Mode
5964 If you want to build on non-stop mode and observe program behavior
5965 without any chance of disruption by @value{GDBN}, you can set
5966 variables to disable all of the debugger's attempts to modify state,
5967 whether by writing memory, inserting breakpoints, etc. These operate
5968 at a low level, intercepting operations from all commands.
5970 When all of these are set to @code{off}, then @value{GDBN} is said to
5971 be @dfn{observer mode}. As a convenience, the variable
5972 @code{observer} can be set to disable these, plus enable non-stop
5975 Note that @value{GDBN} will not prevent you from making nonsensical
5976 combinations of these settings. For instance, if you have enabled
5977 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5978 then breakpoints that work by writing trap instructions into the code
5979 stream will still not be able to be placed.
5984 @item set observer on
5985 @itemx set observer off
5986 When set to @code{on}, this disables all the permission variables
5987 below (except for @code{insert-fast-tracepoints}), plus enables
5988 non-stop debugging. Setting this to @code{off} switches back to
5989 normal debugging, though remaining in non-stop mode.
5992 Show whether observer mode is on or off.
5994 @kindex may-write-registers
5995 @item set may-write-registers on
5996 @itemx set may-write-registers off
5997 This controls whether @value{GDBN} will attempt to alter the values of
5998 registers, such as with assignment expressions in @code{print}, or the
5999 @code{jump} command. It defaults to @code{on}.
6001 @item show may-write-registers
6002 Show the current permission to write registers.
6004 @kindex may-write-memory
6005 @item set may-write-memory on
6006 @itemx set may-write-memory off
6007 This controls whether @value{GDBN} will attempt to alter the contents
6008 of memory, such as with assignment expressions in @code{print}. It
6009 defaults to @code{on}.
6011 @item show may-write-memory
6012 Show the current permission to write memory.
6014 @kindex may-insert-breakpoints
6015 @item set may-insert-breakpoints on
6016 @itemx set may-insert-breakpoints off
6017 This controls whether @value{GDBN} will attempt to insert breakpoints.
6018 This affects all breakpoints, including internal breakpoints defined
6019 by @value{GDBN}. It defaults to @code{on}.
6021 @item show may-insert-breakpoints
6022 Show the current permission to insert breakpoints.
6024 @kindex may-insert-tracepoints
6025 @item set may-insert-tracepoints on
6026 @itemx set may-insert-tracepoints off
6027 This controls whether @value{GDBN} will attempt to insert (regular)
6028 tracepoints at the beginning of a tracing experiment. It affects only
6029 non-fast tracepoints, fast tracepoints being under the control of
6030 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6032 @item show may-insert-tracepoints
6033 Show the current permission to insert tracepoints.
6035 @kindex may-insert-fast-tracepoints
6036 @item set may-insert-fast-tracepoints on
6037 @itemx set may-insert-fast-tracepoints off
6038 This controls whether @value{GDBN} will attempt to insert fast
6039 tracepoints at the beginning of a tracing experiment. It affects only
6040 fast tracepoints, regular (non-fast) tracepoints being under the
6041 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6043 @item show may-insert-fast-tracepoints
6044 Show the current permission to insert fast tracepoints.
6046 @kindex may-interrupt
6047 @item set may-interrupt on
6048 @itemx set may-interrupt off
6049 This controls whether @value{GDBN} will attempt to interrupt or stop
6050 program execution. When this variable is @code{off}, the
6051 @code{interrupt} command will have no effect, nor will
6052 @kbd{Ctrl-c}. It defaults to @code{on}.
6054 @item show may-interrupt
6055 Show the current permission to interrupt or stop the program.
6059 @node Reverse Execution
6060 @chapter Running programs backward
6061 @cindex reverse execution
6062 @cindex running programs backward
6064 When you are debugging a program, it is not unusual to realize that
6065 you have gone too far, and some event of interest has already happened.
6066 If the target environment supports it, @value{GDBN} can allow you to
6067 ``rewind'' the program by running it backward.
6069 A target environment that supports reverse execution should be able
6070 to ``undo'' the changes in machine state that have taken place as the
6071 program was executing normally. Variables, registers etc.@: should
6072 revert to their previous values. Obviously this requires a great
6073 deal of sophistication on the part of the target environment; not
6074 all target environments can support reverse execution.
6076 When a program is executed in reverse, the instructions that
6077 have most recently been executed are ``un-executed'', in reverse
6078 order. The program counter runs backward, following the previous
6079 thread of execution in reverse. As each instruction is ``un-executed'',
6080 the values of memory and/or registers that were changed by that
6081 instruction are reverted to their previous states. After executing
6082 a piece of source code in reverse, all side effects of that code
6083 should be ``undone'', and all variables should be returned to their
6084 prior values@footnote{
6085 Note that some side effects are easier to undo than others. For instance,
6086 memory and registers are relatively easy, but device I/O is hard. Some
6087 targets may be able undo things like device I/O, and some may not.
6089 The contract between @value{GDBN} and the reverse executing target
6090 requires only that the target do something reasonable when
6091 @value{GDBN} tells it to execute backwards, and then report the
6092 results back to @value{GDBN}. Whatever the target reports back to
6093 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6094 assumes that the memory and registers that the target reports are in a
6095 consistant state, but @value{GDBN} accepts whatever it is given.
6098 If you are debugging in a target environment that supports
6099 reverse execution, @value{GDBN} provides the following commands.
6102 @kindex reverse-continue
6103 @kindex rc @r{(@code{reverse-continue})}
6104 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6105 @itemx rc @r{[}@var{ignore-count}@r{]}
6106 Beginning at the point where your program last stopped, start executing
6107 in reverse. Reverse execution will stop for breakpoints and synchronous
6108 exceptions (signals), just like normal execution. Behavior of
6109 asynchronous signals depends on the target environment.
6111 @kindex reverse-step
6112 @kindex rs @r{(@code{step})}
6113 @item reverse-step @r{[}@var{count}@r{]}
6114 Run the program backward until control reaches the start of a
6115 different source line; then stop it, and return control to @value{GDBN}.
6117 Like the @code{step} command, @code{reverse-step} will only stop
6118 at the beginning of a source line. It ``un-executes'' the previously
6119 executed source line. If the previous source line included calls to
6120 debuggable functions, @code{reverse-step} will step (backward) into
6121 the called function, stopping at the beginning of the @emph{last}
6122 statement in the called function (typically a return statement).
6124 Also, as with the @code{step} command, if non-debuggable functions are
6125 called, @code{reverse-step} will run thru them backward without stopping.
6127 @kindex reverse-stepi
6128 @kindex rsi @r{(@code{reverse-stepi})}
6129 @item reverse-stepi @r{[}@var{count}@r{]}
6130 Reverse-execute one machine instruction. Note that the instruction
6131 to be reverse-executed is @emph{not} the one pointed to by the program
6132 counter, but the instruction executed prior to that one. For instance,
6133 if the last instruction was a jump, @code{reverse-stepi} will take you
6134 back from the destination of the jump to the jump instruction itself.
6136 @kindex reverse-next
6137 @kindex rn @r{(@code{reverse-next})}
6138 @item reverse-next @r{[}@var{count}@r{]}
6139 Run backward to the beginning of the previous line executed in
6140 the current (innermost) stack frame. If the line contains function
6141 calls, they will be ``un-executed'' without stopping. Starting from
6142 the first line of a function, @code{reverse-next} will take you back
6143 to the caller of that function, @emph{before} the function was called,
6144 just as the normal @code{next} command would take you from the last
6145 line of a function back to its return to its caller
6146 @footnote{Unless the code is too heavily optimized.}.
6148 @kindex reverse-nexti
6149 @kindex rni @r{(@code{reverse-nexti})}
6150 @item reverse-nexti @r{[}@var{count}@r{]}
6151 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6152 in reverse, except that called functions are ``un-executed'' atomically.
6153 That is, if the previously executed instruction was a return from
6154 another function, @code{reverse-nexti} will continue to execute
6155 in reverse until the call to that function (from the current stack
6158 @kindex reverse-finish
6159 @item reverse-finish
6160 Just as the @code{finish} command takes you to the point where the
6161 current function returns, @code{reverse-finish} takes you to the point
6162 where it was called. Instead of ending up at the end of the current
6163 function invocation, you end up at the beginning.
6165 @kindex set exec-direction
6166 @item set exec-direction
6167 Set the direction of target execution.
6168 @item set exec-direction reverse
6169 @cindex execute forward or backward in time
6170 @value{GDBN} will perform all execution commands in reverse, until the
6171 exec-direction mode is changed to ``forward''. Affected commands include
6172 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6173 command cannot be used in reverse mode.
6174 @item set exec-direction forward
6175 @value{GDBN} will perform all execution commands in the normal fashion.
6176 This is the default.
6180 @node Process Record and Replay
6181 @chapter Recording Inferior's Execution and Replaying It
6182 @cindex process record and replay
6183 @cindex recording inferior's execution and replaying it
6185 On some platforms, @value{GDBN} provides a special @dfn{process record
6186 and replay} target that can record a log of the process execution, and
6187 replay it later with both forward and reverse execution commands.
6190 When this target is in use, if the execution log includes the record
6191 for the next instruction, @value{GDBN} will debug in @dfn{replay
6192 mode}. In the replay mode, the inferior does not really execute code
6193 instructions. Instead, all the events that normally happen during
6194 code execution are taken from the execution log. While code is not
6195 really executed in replay mode, the values of registers (including the
6196 program counter register) and the memory of the inferior are still
6197 changed as they normally would. Their contents are taken from the
6201 If the record for the next instruction is not in the execution log,
6202 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6203 inferior executes normally, and @value{GDBN} records the execution log
6206 The process record and replay target supports reverse execution
6207 (@pxref{Reverse Execution}), even if the platform on which the
6208 inferior runs does not. However, the reverse execution is limited in
6209 this case by the range of the instructions recorded in the execution
6210 log. In other words, reverse execution on platforms that don't
6211 support it directly can only be done in the replay mode.
6213 When debugging in the reverse direction, @value{GDBN} will work in
6214 replay mode as long as the execution log includes the record for the
6215 previous instruction; otherwise, it will work in record mode, if the
6216 platform supports reverse execution, or stop if not.
6218 For architecture environments that support process record and replay,
6219 @value{GDBN} provides the following commands:
6222 @kindex target record
6223 @kindex target record-full
6224 @kindex target record-btrace
6227 @kindex record btrace
6231 @item record @var{method}
6232 This command starts the process record and replay target. The
6233 recording method can be specified as parameter. Without a parameter
6234 the command uses the @code{full} recording method. The following
6235 recording methods are available:
6239 Full record/replay recording using @value{GDBN}'s software record and
6240 replay implementation. This method allows replaying and reverse
6244 Hardware-supported instruction recording. This method does not allow
6245 replaying and reverse execution.
6247 This recording method may not be available on all processors.
6250 The process record and replay target can only debug a process that is
6251 already running. Therefore, you need first to start the process with
6252 the @kbd{run} or @kbd{start} commands, and then start the recording
6253 with the @kbd{record @var{method}} command.
6255 Both @code{record @var{method}} and @code{rec @var{method}} are
6256 aliases of @code{target record-@var{method}}.
6258 @cindex displaced stepping, and process record and replay
6259 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6260 will be automatically disabled when process record and replay target
6261 is started. That's because the process record and replay target
6262 doesn't support displaced stepping.
6264 @cindex non-stop mode, and process record and replay
6265 @cindex asynchronous execution, and process record and replay
6266 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6267 the asynchronous execution mode (@pxref{Background Execution}), not
6268 all recording methods are available. The @code{full} recording method
6269 does not support these two modes.
6274 Stop the process record and replay target. When process record and
6275 replay target stops, the entire execution log will be deleted and the
6276 inferior will either be terminated, or will remain in its final state.
6278 When you stop the process record and replay target in record mode (at
6279 the end of the execution log), the inferior will be stopped at the
6280 next instruction that would have been recorded. In other words, if
6281 you record for a while and then stop recording, the inferior process
6282 will be left in the same state as if the recording never happened.
6284 On the other hand, if the process record and replay target is stopped
6285 while in replay mode (that is, not at the end of the execution log,
6286 but at some earlier point), the inferior process will become ``live''
6287 at that earlier state, and it will then be possible to continue the
6288 usual ``live'' debugging of the process from that state.
6290 When the inferior process exits, or @value{GDBN} detaches from it,
6291 process record and replay target will automatically stop itself.
6295 Go to a specific location in the execution log. There are several
6296 ways to specify the location to go to:
6299 @item record goto begin
6300 @itemx record goto start
6301 Go to the beginning of the execution log.
6303 @item record goto end
6304 Go to the end of the execution log.
6306 @item record goto @var{n}
6307 Go to instruction number @var{n} in the execution log.
6311 @item record save @var{filename}
6312 Save the execution log to a file @file{@var{filename}}.
6313 Default filename is @file{gdb_record.@var{process_id}}, where
6314 @var{process_id} is the process ID of the inferior.
6316 This command may not be available for all recording methods.
6318 @kindex record restore
6319 @item record restore @var{filename}
6320 Restore the execution log from a file @file{@var{filename}}.
6321 File must have been created with @code{record save}.
6323 @kindex set record full
6324 @item set record full insn-number-max @var{limit}
6325 @itemx set record full insn-number-max unlimited
6326 Set the limit of instructions to be recorded for the @code{full}
6327 recording method. Default value is 200000.
6329 If @var{limit} is a positive number, then @value{GDBN} will start
6330 deleting instructions from the log once the number of the record
6331 instructions becomes greater than @var{limit}. For every new recorded
6332 instruction, @value{GDBN} will delete the earliest recorded
6333 instruction to keep the number of recorded instructions at the limit.
6334 (Since deleting recorded instructions loses information, @value{GDBN}
6335 lets you control what happens when the limit is reached, by means of
6336 the @code{stop-at-limit} option, described below.)
6338 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6339 delete recorded instructions from the execution log. The number of
6340 recorded instructions is limited only by the available memory.
6342 @kindex show record full
6343 @item show record full insn-number-max
6344 Show the limit of instructions to be recorded with the @code{full}
6347 @item set record full stop-at-limit
6348 Control the behavior of the @code{full} recording method when the
6349 number of recorded instructions reaches the limit. If ON (the
6350 default), @value{GDBN} will stop when the limit is reached for the
6351 first time and ask you whether you want to stop the inferior or
6352 continue running it and recording the execution log. If you decide
6353 to continue recording, each new recorded instruction will cause the
6354 oldest one to be deleted.
6356 If this option is OFF, @value{GDBN} will automatically delete the
6357 oldest record to make room for each new one, without asking.
6359 @item show record full stop-at-limit
6360 Show the current setting of @code{stop-at-limit}.
6362 @item set record full memory-query
6363 Control the behavior when @value{GDBN} is unable to record memory
6364 changes caused by an instruction for the @code{full} recording method.
6365 If ON, @value{GDBN} will query whether to stop the inferior in that
6368 If this option is OFF (the default), @value{GDBN} will automatically
6369 ignore the effect of such instructions on memory. Later, when
6370 @value{GDBN} replays this execution log, it will mark the log of this
6371 instruction as not accessible, and it will not affect the replay
6374 @item show record full memory-query
6375 Show the current setting of @code{memory-query}.
6379 Show various statistics about the recording depending on the recording
6384 For the @code{full} recording method, it shows the state of process
6385 record and its in-memory execution log buffer, including:
6389 Whether in record mode or replay mode.
6391 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6393 Highest recorded instruction number.
6395 Current instruction about to be replayed (if in replay mode).
6397 Number of instructions contained in the execution log.
6399 Maximum number of instructions that may be contained in the execution log.
6403 For the @code{btrace} recording method, it shows the number of
6404 instructions that have been recorded and the number of blocks of
6405 sequential control-flow that is formed by the recorded instructions.
6408 @kindex record delete
6411 When record target runs in replay mode (``in the past''), delete the
6412 subsequent execution log and begin to record a new execution log starting
6413 from the current address. This means you will abandon the previously
6414 recorded ``future'' and begin recording a new ``future''.
6416 @kindex record instruction-history
6417 @kindex rec instruction-history
6418 @item record instruction-history
6419 Disassembles instructions from the recorded execution log. By
6420 default, ten instructions are disassembled. This can be changed using
6421 the @code{set record instruction-history-size} command. Instructions
6422 are printed in execution order. There are several ways to specify
6423 what part of the execution log to disassemble:
6426 @item record instruction-history @var{insn}
6427 Disassembles ten instructions starting from instruction number
6430 @item record instruction-history @var{insn}, +/-@var{n}
6431 Disassembles @var{n} instructions around instruction number
6432 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6433 @var{n} instructions after instruction number @var{insn}. If
6434 @var{n} is preceded with @code{-}, disassembles @var{n}
6435 instructions before instruction number @var{insn}.
6437 @item record instruction-history
6438 Disassembles ten more instructions after the last disassembly.
6440 @item record instruction-history -
6441 Disassembles ten more instructions before the last disassembly.
6443 @item record instruction-history @var{begin} @var{end}
6444 Disassembles instructions beginning with instruction number
6445 @var{begin} until instruction number @var{end}. The instruction
6446 number @var{end} is not included.
6449 This command may not be available for all recording methods.
6452 @item set record instruction-history-size @var{size}
6453 @itemx set record instruction-history-size unlimited
6454 Define how many instructions to disassemble in the @code{record
6455 instruction-history} command. The default value is 10.
6456 A @var{size} of @code{unlimited} means unlimited instructions.
6459 @item show record instruction-history-size
6460 Show how many instructions to disassemble in the @code{record
6461 instruction-history} command.
6463 @kindex record function-call-history
6464 @kindex rec function-call-history
6465 @item record function-call-history
6466 Prints the execution history at function granularity. It prints one
6467 line for each sequence of instructions that belong to the same
6468 function giving the name of that function, the source lines
6469 for this instruction sequence (if the @code{/l} modifier is
6470 specified), and the instructions numbers that form the sequence (if
6471 the @code{/i} modifier is specified).
6474 (@value{GDBP}) @b{list 1, 10}
6485 (@value{GDBP}) @b{record function-call-history /l}
6491 By default, ten lines are printed. This can be changed using the
6492 @code{set record function-call-history-size} command. Functions are
6493 printed in execution order. There are several ways to specify what
6497 @item record function-call-history @var{func}
6498 Prints ten functions starting from function number @var{func}.
6500 @item record function-call-history @var{func}, +/-@var{n}
6501 Prints @var{n} functions around function number @var{func}. If
6502 @var{n} is preceded with @code{+}, prints @var{n} functions after
6503 function number @var{func}. If @var{n} is preceded with @code{-},
6504 prints @var{n} functions before function number @var{func}.
6506 @item record function-call-history
6507 Prints ten more functions after the last ten-line print.
6509 @item record function-call-history -
6510 Prints ten more functions before the last ten-line print.
6512 @item record function-call-history @var{begin} @var{end}
6513 Prints functions beginning with function number @var{begin} until
6514 function number @var{end}. The function number @var{end} is not
6518 This command may not be available for all recording methods.
6520 @item set record function-call-history-size @var{size}
6521 @itemx set record function-call-history-size unlimited
6522 Define how many lines to print in the
6523 @code{record function-call-history} command. The default value is 10.
6524 A size of @code{unlimited} means unlimited lines.
6526 @item show record function-call-history-size
6527 Show how many lines to print in the
6528 @code{record function-call-history} command.
6533 @chapter Examining the Stack
6535 When your program has stopped, the first thing you need to know is where it
6536 stopped and how it got there.
6539 Each time your program performs a function call, information about the call
6541 That information includes the location of the call in your program,
6542 the arguments of the call,
6543 and the local variables of the function being called.
6544 The information is saved in a block of data called a @dfn{stack frame}.
6545 The stack frames are allocated in a region of memory called the @dfn{call
6548 When your program stops, the @value{GDBN} commands for examining the
6549 stack allow you to see all of this information.
6551 @cindex selected frame
6552 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6553 @value{GDBN} commands refer implicitly to the selected frame. In
6554 particular, whenever you ask @value{GDBN} for the value of a variable in
6555 your program, the value is found in the selected frame. There are
6556 special @value{GDBN} commands to select whichever frame you are
6557 interested in. @xref{Selection, ,Selecting a Frame}.
6559 When your program stops, @value{GDBN} automatically selects the
6560 currently executing frame and describes it briefly, similar to the
6561 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6564 * Frames:: Stack frames
6565 * Backtrace:: Backtraces
6566 * Frame Filter Management:: Managing frame filters
6567 * Selection:: Selecting a frame
6568 * Frame Info:: Information on a frame
6573 @section Stack Frames
6575 @cindex frame, definition
6577 The call stack is divided up into contiguous pieces called @dfn{stack
6578 frames}, or @dfn{frames} for short; each frame is the data associated
6579 with one call to one function. The frame contains the arguments given
6580 to the function, the function's local variables, and the address at
6581 which the function is executing.
6583 @cindex initial frame
6584 @cindex outermost frame
6585 @cindex innermost frame
6586 When your program is started, the stack has only one frame, that of the
6587 function @code{main}. This is called the @dfn{initial} frame or the
6588 @dfn{outermost} frame. Each time a function is called, a new frame is
6589 made. Each time a function returns, the frame for that function invocation
6590 is eliminated. If a function is recursive, there can be many frames for
6591 the same function. The frame for the function in which execution is
6592 actually occurring is called the @dfn{innermost} frame. This is the most
6593 recently created of all the stack frames that still exist.
6595 @cindex frame pointer
6596 Inside your program, stack frames are identified by their addresses. A
6597 stack frame consists of many bytes, each of which has its own address; each
6598 kind of computer has a convention for choosing one byte whose
6599 address serves as the address of the frame. Usually this address is kept
6600 in a register called the @dfn{frame pointer register}
6601 (@pxref{Registers, $fp}) while execution is going on in that frame.
6603 @cindex frame number
6604 @value{GDBN} assigns numbers to all existing stack frames, starting with
6605 zero for the innermost frame, one for the frame that called it,
6606 and so on upward. These numbers do not really exist in your program;
6607 they are assigned by @value{GDBN} to give you a way of designating stack
6608 frames in @value{GDBN} commands.
6610 @c The -fomit-frame-pointer below perennially causes hbox overflow
6611 @c underflow problems.
6612 @cindex frameless execution
6613 Some compilers provide a way to compile functions so that they operate
6614 without stack frames. (For example, the @value{NGCC} option
6616 @samp{-fomit-frame-pointer}
6618 generates functions without a frame.)
6619 This is occasionally done with heavily used library functions to save
6620 the frame setup time. @value{GDBN} has limited facilities for dealing
6621 with these function invocations. If the innermost function invocation
6622 has no stack frame, @value{GDBN} nevertheless regards it as though
6623 it had a separate frame, which is numbered zero as usual, allowing
6624 correct tracing of the function call chain. However, @value{GDBN} has
6625 no provision for frameless functions elsewhere in the stack.
6628 @kindex frame@r{, command}
6629 @cindex current stack frame
6630 @item frame @var{args}
6631 The @code{frame} command allows you to move from one stack frame to another,
6632 and to print the stack frame you select. @var{args} may be either the
6633 address of the frame or the stack frame number. Without an argument,
6634 @code{frame} prints the current stack frame.
6636 @kindex select-frame
6637 @cindex selecting frame silently
6639 The @code{select-frame} command allows you to move from one stack frame
6640 to another without printing the frame. This is the silent version of
6648 @cindex call stack traces
6649 A backtrace is a summary of how your program got where it is. It shows one
6650 line per frame, for many frames, starting with the currently executing
6651 frame (frame zero), followed by its caller (frame one), and on up the
6654 @anchor{backtrace-command}
6657 @kindex bt @r{(@code{backtrace})}
6660 Print a backtrace of the entire stack: one line per frame for all
6661 frames in the stack.
6663 You can stop the backtrace at any time by typing the system interrupt
6664 character, normally @kbd{Ctrl-c}.
6666 @item backtrace @var{n}
6668 Similar, but print only the innermost @var{n} frames.
6670 @item backtrace -@var{n}
6672 Similar, but print only the outermost @var{n} frames.
6674 @item backtrace full
6676 @itemx bt full @var{n}
6677 @itemx bt full -@var{n}
6678 Print the values of the local variables also. @var{n} specifies the
6679 number of frames to print, as described above.
6681 @item backtrace no-filters
6682 @itemx bt no-filters
6683 @itemx bt no-filters @var{n}
6684 @itemx bt no-filters -@var{n}
6685 @itemx bt no-filters full
6686 @itemx bt no-filters full @var{n}
6687 @itemx bt no-filters full -@var{n}
6688 Do not run Python frame filters on this backtrace. @xref{Frame
6689 Filter API}, for more information. Additionally use @ref{disable
6690 frame-filter all} to turn off all frame filters. This is only
6691 relevant when @value{GDBN} has been configured with @code{Python}
6697 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6698 are additional aliases for @code{backtrace}.
6700 @cindex multiple threads, backtrace
6701 In a multi-threaded program, @value{GDBN} by default shows the
6702 backtrace only for the current thread. To display the backtrace for
6703 several or all of the threads, use the command @code{thread apply}
6704 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6705 apply all backtrace}, @value{GDBN} will display the backtrace for all
6706 the threads; this is handy when you debug a core dump of a
6707 multi-threaded program.
6709 Each line in the backtrace shows the frame number and the function name.
6710 The program counter value is also shown---unless you use @code{set
6711 print address off}. The backtrace also shows the source file name and
6712 line number, as well as the arguments to the function. The program
6713 counter value is omitted if it is at the beginning of the code for that
6716 Here is an example of a backtrace. It was made with the command
6717 @samp{bt 3}, so it shows the innermost three frames.
6721 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6723 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6724 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6726 (More stack frames follow...)
6731 The display for frame zero does not begin with a program counter
6732 value, indicating that your program has stopped at the beginning of the
6733 code for line @code{993} of @code{builtin.c}.
6736 The value of parameter @code{data} in frame 1 has been replaced by
6737 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6738 only if it is a scalar (integer, pointer, enumeration, etc). See command
6739 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6740 on how to configure the way function parameter values are printed.
6742 @cindex optimized out, in backtrace
6743 @cindex function call arguments, optimized out
6744 If your program was compiled with optimizations, some compilers will
6745 optimize away arguments passed to functions if those arguments are
6746 never used after the call. Such optimizations generate code that
6747 passes arguments through registers, but doesn't store those arguments
6748 in the stack frame. @value{GDBN} has no way of displaying such
6749 arguments in stack frames other than the innermost one. Here's what
6750 such a backtrace might look like:
6754 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6756 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6757 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6759 (More stack frames follow...)
6764 The values of arguments that were not saved in their stack frames are
6765 shown as @samp{<optimized out>}.
6767 If you need to display the values of such optimized-out arguments,
6768 either deduce that from other variables whose values depend on the one
6769 you are interested in, or recompile without optimizations.
6771 @cindex backtrace beyond @code{main} function
6772 @cindex program entry point
6773 @cindex startup code, and backtrace
6774 Most programs have a standard user entry point---a place where system
6775 libraries and startup code transition into user code. For C this is
6776 @code{main}@footnote{
6777 Note that embedded programs (the so-called ``free-standing''
6778 environment) are not required to have a @code{main} function as the
6779 entry point. They could even have multiple entry points.}.
6780 When @value{GDBN} finds the entry function in a backtrace
6781 it will terminate the backtrace, to avoid tracing into highly
6782 system-specific (and generally uninteresting) code.
6784 If you need to examine the startup code, or limit the number of levels
6785 in a backtrace, you can change this behavior:
6788 @item set backtrace past-main
6789 @itemx set backtrace past-main on
6790 @kindex set backtrace
6791 Backtraces will continue past the user entry point.
6793 @item set backtrace past-main off
6794 Backtraces will stop when they encounter the user entry point. This is the
6797 @item show backtrace past-main
6798 @kindex show backtrace
6799 Display the current user entry point backtrace policy.
6801 @item set backtrace past-entry
6802 @itemx set backtrace past-entry on
6803 Backtraces will continue past the internal entry point of an application.
6804 This entry point is encoded by the linker when the application is built,
6805 and is likely before the user entry point @code{main} (or equivalent) is called.
6807 @item set backtrace past-entry off
6808 Backtraces will stop when they encounter the internal entry point of an
6809 application. This is the default.
6811 @item show backtrace past-entry
6812 Display the current internal entry point backtrace policy.
6814 @item set backtrace limit @var{n}
6815 @itemx set backtrace limit 0
6816 @itemx set backtrace limit unlimited
6817 @cindex backtrace limit
6818 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6819 or zero means unlimited levels.
6821 @item show backtrace limit
6822 Display the current limit on backtrace levels.
6825 You can control how file names are displayed.
6828 @item set filename-display
6829 @itemx set filename-display relative
6830 @cindex filename-display
6831 Display file names relative to the compilation directory. This is the default.
6833 @item set filename-display basename
6834 Display only basename of a filename.
6836 @item set filename-display absolute
6837 Display an absolute filename.
6839 @item show filename-display
6840 Show the current way to display filenames.
6843 @node Frame Filter Management
6844 @section Management of Frame Filters.
6845 @cindex managing frame filters
6847 Frame filters are Python based utilities to manage and decorate the
6848 output of frames. @xref{Frame Filter API}, for further information.
6850 Managing frame filters is performed by several commands available
6851 within @value{GDBN}, detailed here.
6854 @kindex info frame-filter
6855 @item info frame-filter
6856 Print a list of installed frame filters from all dictionaries, showing
6857 their name, priority and enabled status.
6859 @kindex disable frame-filter
6860 @anchor{disable frame-filter all}
6861 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
6862 Disable a frame filter in the dictionary matching
6863 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6864 @var{filter-dictionary} may be @code{all}, @code{global},
6865 @code{progspace} or the name of the object file where the frame filter
6866 dictionary resides. When @code{all} is specified, all frame filters
6867 across all dictionaries are disabled. @var{filter-name} is the name
6868 of the frame filter and is used when @code{all} is not the option for
6869 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
6870 may be enabled again later.
6872 @kindex enable frame-filter
6873 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
6874 Enable a frame filter in the dictionary matching
6875 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6876 @var{filter-dictionary} may be @code{all}, @code{global},
6877 @code{progspace} or the name of the object file where the frame filter
6878 dictionary resides. When @code{all} is specified, all frame filters across
6879 all dictionaries are enabled. @var{filter-name} is the name of the frame
6880 filter and is used when @code{all} is not the option for
6881 @var{filter-dictionary}.
6886 (gdb) info frame-filter
6888 global frame-filters:
6889 Priority Enabled Name
6890 1000 No PrimaryFunctionFilter
6893 progspace /build/test frame-filters:
6894 Priority Enabled Name
6895 100 Yes ProgspaceFilter
6897 objfile /build/test frame-filters:
6898 Priority Enabled Name
6899 999 Yes BuildProgra Filter
6901 (gdb) disable frame-filter /build/test BuildProgramFilter
6902 (gdb) info frame-filter
6904 global frame-filters:
6905 Priority Enabled Name
6906 1000 No PrimaryFunctionFilter
6909 progspace /build/test frame-filters:
6910 Priority Enabled Name
6911 100 Yes ProgspaceFilter
6913 objfile /build/test frame-filters:
6914 Priority Enabled Name
6915 999 No BuildProgramFilter
6917 (gdb) enable frame-filter global PrimaryFunctionFilter
6918 (gdb) info frame-filter
6920 global frame-filters:
6921 Priority Enabled Name
6922 1000 Yes PrimaryFunctionFilter
6925 progspace /build/test frame-filters:
6926 Priority Enabled Name
6927 100 Yes ProgspaceFilter
6929 objfile /build/test frame-filters:
6930 Priority Enabled Name
6931 999 No BuildProgramFilter
6934 @kindex set frame-filter priority
6935 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
6936 Set the @var{priority} of a frame filter in the dictionary matching
6937 @var{filter-dictionary}, and the frame filter name matching
6938 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6939 @code{progspace} or the name of the object file where the frame filter
6940 dictionary resides. @var{priority} is an integer.
6942 @kindex show frame-filter priority
6943 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
6944 Show the @var{priority} of a frame filter in the dictionary matching
6945 @var{filter-dictionary}, and the frame filter name matching
6946 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6947 @code{progspace} or the name of the object file where the frame filter
6953 (gdb) info frame-filter
6955 global frame-filters:
6956 Priority Enabled Name
6957 1000 Yes PrimaryFunctionFilter
6960 progspace /build/test frame-filters:
6961 Priority Enabled Name
6962 100 Yes ProgspaceFilter
6964 objfile /build/test frame-filters:
6965 Priority Enabled Name
6966 999 No BuildProgramFilter
6968 (gdb) set frame-filter priority global Reverse 50
6969 (gdb) info frame-filter
6971 global frame-filters:
6972 Priority Enabled Name
6973 1000 Yes PrimaryFunctionFilter
6976 progspace /build/test frame-filters:
6977 Priority Enabled Name
6978 100 Yes ProgspaceFilter
6980 objfile /build/test frame-filters:
6981 Priority Enabled Name
6982 999 No BuildProgramFilter
6987 @section Selecting a Frame
6989 Most commands for examining the stack and other data in your program work on
6990 whichever stack frame is selected at the moment. Here are the commands for
6991 selecting a stack frame; all of them finish by printing a brief description
6992 of the stack frame just selected.
6995 @kindex frame@r{, selecting}
6996 @kindex f @r{(@code{frame})}
6999 Select frame number @var{n}. Recall that frame zero is the innermost
7000 (currently executing) frame, frame one is the frame that called the
7001 innermost one, and so on. The highest-numbered frame is the one for
7004 @item frame @var{addr}
7006 Select the frame at address @var{addr}. This is useful mainly if the
7007 chaining of stack frames has been damaged by a bug, making it
7008 impossible for @value{GDBN} to assign numbers properly to all frames. In
7009 addition, this can be useful when your program has multiple stacks and
7010 switches between them.
7012 On the SPARC architecture, @code{frame} needs two addresses to
7013 select an arbitrary frame: a frame pointer and a stack pointer.
7015 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7016 pointer and a program counter.
7018 On the 29k architecture, it needs three addresses: a register stack
7019 pointer, a program counter, and a memory stack pointer.
7023 Move @var{n} frames up the stack. For positive numbers @var{n}, this
7024 advances toward the outermost frame, to higher frame numbers, to frames
7025 that have existed longer. @var{n} defaults to one.
7028 @kindex do @r{(@code{down})}
7030 Move @var{n} frames down the stack. For positive numbers @var{n}, this
7031 advances toward the innermost frame, to lower frame numbers, to frames
7032 that were created more recently. @var{n} defaults to one. You may
7033 abbreviate @code{down} as @code{do}.
7036 All of these commands end by printing two lines of output describing the
7037 frame. The first line shows the frame number, the function name, the
7038 arguments, and the source file and line number of execution in that
7039 frame. The second line shows the text of that source line.
7047 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7049 10 read_input_file (argv[i]);
7053 After such a printout, the @code{list} command with no arguments
7054 prints ten lines centered on the point of execution in the frame.
7055 You can also edit the program at the point of execution with your favorite
7056 editing program by typing @code{edit}.
7057 @xref{List, ,Printing Source Lines},
7061 @kindex down-silently
7063 @item up-silently @var{n}
7064 @itemx down-silently @var{n}
7065 These two commands are variants of @code{up} and @code{down},
7066 respectively; they differ in that they do their work silently, without
7067 causing display of the new frame. They are intended primarily for use
7068 in @value{GDBN} command scripts, where the output might be unnecessary and
7073 @section Information About a Frame
7075 There are several other commands to print information about the selected
7081 When used without any argument, this command does not change which
7082 frame is selected, but prints a brief description of the currently
7083 selected stack frame. It can be abbreviated @code{f}. With an
7084 argument, this command is used to select a stack frame.
7085 @xref{Selection, ,Selecting a Frame}.
7088 @kindex info f @r{(@code{info frame})}
7091 This command prints a verbose description of the selected stack frame,
7096 the address of the frame
7098 the address of the next frame down (called by this frame)
7100 the address of the next frame up (caller of this frame)
7102 the language in which the source code corresponding to this frame is written
7104 the address of the frame's arguments
7106 the address of the frame's local variables
7108 the program counter saved in it (the address of execution in the caller frame)
7110 which registers were saved in the frame
7113 @noindent The verbose description is useful when
7114 something has gone wrong that has made the stack format fail to fit
7115 the usual conventions.
7117 @item info frame @var{addr}
7118 @itemx info f @var{addr}
7119 Print a verbose description of the frame at address @var{addr}, without
7120 selecting that frame. The selected frame remains unchanged by this
7121 command. This requires the same kind of address (more than one for some
7122 architectures) that you specify in the @code{frame} command.
7123 @xref{Selection, ,Selecting a Frame}.
7127 Print the arguments of the selected frame, each on a separate line.
7131 Print the local variables of the selected frame, each on a separate
7132 line. These are all variables (declared either static or automatic)
7133 accessible at the point of execution of the selected frame.
7139 @chapter Examining Source Files
7141 @value{GDBN} can print parts of your program's source, since the debugging
7142 information recorded in the program tells @value{GDBN} what source files were
7143 used to build it. When your program stops, @value{GDBN} spontaneously prints
7144 the line where it stopped. Likewise, when you select a stack frame
7145 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7146 execution in that frame has stopped. You can print other portions of
7147 source files by explicit command.
7149 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7150 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7151 @value{GDBN} under @sc{gnu} Emacs}.
7154 * List:: Printing source lines
7155 * Specify Location:: How to specify code locations
7156 * Edit:: Editing source files
7157 * Search:: Searching source files
7158 * Source Path:: Specifying source directories
7159 * Machine Code:: Source and machine code
7163 @section Printing Source Lines
7166 @kindex l @r{(@code{list})}
7167 To print lines from a source file, use the @code{list} command
7168 (abbreviated @code{l}). By default, ten lines are printed.
7169 There are several ways to specify what part of the file you want to
7170 print; see @ref{Specify Location}, for the full list.
7172 Here are the forms of the @code{list} command most commonly used:
7175 @item list @var{linenum}
7176 Print lines centered around line number @var{linenum} in the
7177 current source file.
7179 @item list @var{function}
7180 Print lines centered around the beginning of function
7184 Print more lines. If the last lines printed were printed with a
7185 @code{list} command, this prints lines following the last lines
7186 printed; however, if the last line printed was a solitary line printed
7187 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7188 Stack}), this prints lines centered around that line.
7191 Print lines just before the lines last printed.
7194 @cindex @code{list}, how many lines to display
7195 By default, @value{GDBN} prints ten source lines with any of these forms of
7196 the @code{list} command. You can change this using @code{set listsize}:
7199 @kindex set listsize
7200 @item set listsize @var{count}
7201 @itemx set listsize unlimited
7202 Make the @code{list} command display @var{count} source lines (unless
7203 the @code{list} argument explicitly specifies some other number).
7204 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7206 @kindex show listsize
7208 Display the number of lines that @code{list} prints.
7211 Repeating a @code{list} command with @key{RET} discards the argument,
7212 so it is equivalent to typing just @code{list}. This is more useful
7213 than listing the same lines again. An exception is made for an
7214 argument of @samp{-}; that argument is preserved in repetition so that
7215 each repetition moves up in the source file.
7217 In general, the @code{list} command expects you to supply zero, one or two
7218 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7219 of writing them (@pxref{Specify Location}), but the effect is always
7220 to specify some source line.
7222 Here is a complete description of the possible arguments for @code{list}:
7225 @item list @var{linespec}
7226 Print lines centered around the line specified by @var{linespec}.
7228 @item list @var{first},@var{last}
7229 Print lines from @var{first} to @var{last}. Both arguments are
7230 linespecs. When a @code{list} command has two linespecs, and the
7231 source file of the second linespec is omitted, this refers to
7232 the same source file as the first linespec.
7234 @item list ,@var{last}
7235 Print lines ending with @var{last}.
7237 @item list @var{first},
7238 Print lines starting with @var{first}.
7241 Print lines just after the lines last printed.
7244 Print lines just before the lines last printed.
7247 As described in the preceding table.
7250 @node Specify Location
7251 @section Specifying a Location
7252 @cindex specifying location
7255 Several @value{GDBN} commands accept arguments that specify a location
7256 of your program's code. Since @value{GDBN} is a source-level
7257 debugger, a location usually specifies some line in the source code;
7258 for that reason, locations are also known as @dfn{linespecs}.
7260 Here are all the different ways of specifying a code location that
7261 @value{GDBN} understands:
7265 Specifies the line number @var{linenum} of the current source file.
7268 @itemx +@var{offset}
7269 Specifies the line @var{offset} lines before or after the @dfn{current
7270 line}. For the @code{list} command, the current line is the last one
7271 printed; for the breakpoint commands, this is the line at which
7272 execution stopped in the currently selected @dfn{stack frame}
7273 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7274 used as the second of the two linespecs in a @code{list} command,
7275 this specifies the line @var{offset} lines up or down from the first
7278 @item @var{filename}:@var{linenum}
7279 Specifies the line @var{linenum} in the source file @var{filename}.
7280 If @var{filename} is a relative file name, then it will match any
7281 source file name with the same trailing components. For example, if
7282 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7283 name of @file{/build/trunk/gcc/expr.c}, but not
7284 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7286 @item @var{function}
7287 Specifies the line that begins the body of the function @var{function}.
7288 For example, in C, this is the line with the open brace.
7290 @item @var{function}:@var{label}
7291 Specifies the line where @var{label} appears in @var{function}.
7293 @item @var{filename}:@var{function}
7294 Specifies the line that begins the body of the function @var{function}
7295 in the file @var{filename}. You only need the file name with a
7296 function name to avoid ambiguity when there are identically named
7297 functions in different source files.
7300 Specifies the line at which the label named @var{label} appears.
7301 @value{GDBN} searches for the label in the function corresponding to
7302 the currently selected stack frame. If there is no current selected
7303 stack frame (for instance, if the inferior is not running), then
7304 @value{GDBN} will not search for a label.
7306 @item *@var{address}
7307 Specifies the program address @var{address}. For line-oriented
7308 commands, such as @code{list} and @code{edit}, this specifies a source
7309 line that contains @var{address}. For @code{break} and other
7310 breakpoint oriented commands, this can be used to set breakpoints in
7311 parts of your program which do not have debugging information or
7314 Here @var{address} may be any expression valid in the current working
7315 language (@pxref{Languages, working language}) that specifies a code
7316 address. In addition, as a convenience, @value{GDBN} extends the
7317 semantics of expressions used in locations to cover the situations
7318 that frequently happen during debugging. Here are the various forms
7322 @item @var{expression}
7323 Any expression valid in the current working language.
7325 @item @var{funcaddr}
7326 An address of a function or procedure derived from its name. In C,
7327 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7328 simply the function's name @var{function} (and actually a special case
7329 of a valid expression). In Pascal and Modula-2, this is
7330 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7331 (although the Pascal form also works).
7333 This form specifies the address of the function's first instruction,
7334 before the stack frame and arguments have been set up.
7336 @item '@var{filename}'::@var{funcaddr}
7337 Like @var{funcaddr} above, but also specifies the name of the source
7338 file explicitly. This is useful if the name of the function does not
7339 specify the function unambiguously, e.g., if there are several
7340 functions with identical names in different source files.
7343 @cindex breakpoint at static probe point
7344 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7345 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7346 applications to embed static probes. @xref{Static Probe Points}, for more
7347 information on finding and using static probes. This form of linespec
7348 specifies the location of such a static probe.
7350 If @var{objfile} is given, only probes coming from that shared library
7351 or executable matching @var{objfile} as a regular expression are considered.
7352 If @var{provider} is given, then only probes from that provider are considered.
7353 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7354 each one of those probes.
7360 @section Editing Source Files
7361 @cindex editing source files
7364 @kindex e @r{(@code{edit})}
7365 To edit the lines in a source file, use the @code{edit} command.
7366 The editing program of your choice
7367 is invoked with the current line set to
7368 the active line in the program.
7369 Alternatively, there are several ways to specify what part of the file you
7370 want to print if you want to see other parts of the program:
7373 @item edit @var{location}
7374 Edit the source file specified by @code{location}. Editing starts at
7375 that @var{location}, e.g., at the specified source line of the
7376 specified file. @xref{Specify Location}, for all the possible forms
7377 of the @var{location} argument; here are the forms of the @code{edit}
7378 command most commonly used:
7381 @item edit @var{number}
7382 Edit the current source file with @var{number} as the active line number.
7384 @item edit @var{function}
7385 Edit the file containing @var{function} at the beginning of its definition.
7390 @subsection Choosing your Editor
7391 You can customize @value{GDBN} to use any editor you want
7393 The only restriction is that your editor (say @code{ex}), recognizes the
7394 following command-line syntax:
7396 ex +@var{number} file
7398 The optional numeric value +@var{number} specifies the number of the line in
7399 the file where to start editing.}.
7400 By default, it is @file{@value{EDITOR}}, but you can change this
7401 by setting the environment variable @code{EDITOR} before using
7402 @value{GDBN}. For example, to configure @value{GDBN} to use the
7403 @code{vi} editor, you could use these commands with the @code{sh} shell:
7409 or in the @code{csh} shell,
7411 setenv EDITOR /usr/bin/vi
7416 @section Searching Source Files
7417 @cindex searching source files
7419 There are two commands for searching through the current source file for a
7424 @kindex forward-search
7425 @kindex fo @r{(@code{forward-search})}
7426 @item forward-search @var{regexp}
7427 @itemx search @var{regexp}
7428 The command @samp{forward-search @var{regexp}} checks each line,
7429 starting with the one following the last line listed, for a match for
7430 @var{regexp}. It lists the line that is found. You can use the
7431 synonym @samp{search @var{regexp}} or abbreviate the command name as
7434 @kindex reverse-search
7435 @item reverse-search @var{regexp}
7436 The command @samp{reverse-search @var{regexp}} checks each line, starting
7437 with the one before the last line listed and going backward, for a match
7438 for @var{regexp}. It lists the line that is found. You can abbreviate
7439 this command as @code{rev}.
7443 @section Specifying Source Directories
7446 @cindex directories for source files
7447 Executable programs sometimes do not record the directories of the source
7448 files from which they were compiled, just the names. Even when they do,
7449 the directories could be moved between the compilation and your debugging
7450 session. @value{GDBN} has a list of directories to search for source files;
7451 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7452 it tries all the directories in the list, in the order they are present
7453 in the list, until it finds a file with the desired name.
7455 For example, suppose an executable references the file
7456 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7457 @file{/mnt/cross}. The file is first looked up literally; if this
7458 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7459 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7460 message is printed. @value{GDBN} does not look up the parts of the
7461 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7462 Likewise, the subdirectories of the source path are not searched: if
7463 the source path is @file{/mnt/cross}, and the binary refers to
7464 @file{foo.c}, @value{GDBN} would not find it under
7465 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7467 Plain file names, relative file names with leading directories, file
7468 names containing dots, etc.@: are all treated as described above; for
7469 instance, if the source path is @file{/mnt/cross}, and the source file
7470 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7471 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7472 that---@file{/mnt/cross/foo.c}.
7474 Note that the executable search path is @emph{not} used to locate the
7477 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7478 any information it has cached about where source files are found and where
7479 each line is in the file.
7483 When you start @value{GDBN}, its source path includes only @samp{cdir}
7484 and @samp{cwd}, in that order.
7485 To add other directories, use the @code{directory} command.
7487 The search path is used to find both program source files and @value{GDBN}
7488 script files (read using the @samp{-command} option and @samp{source} command).
7490 In addition to the source path, @value{GDBN} provides a set of commands
7491 that manage a list of source path substitution rules. A @dfn{substitution
7492 rule} specifies how to rewrite source directories stored in the program's
7493 debug information in case the sources were moved to a different
7494 directory between compilation and debugging. A rule is made of
7495 two strings, the first specifying what needs to be rewritten in
7496 the path, and the second specifying how it should be rewritten.
7497 In @ref{set substitute-path}, we name these two parts @var{from} and
7498 @var{to} respectively. @value{GDBN} does a simple string replacement
7499 of @var{from} with @var{to} at the start of the directory part of the
7500 source file name, and uses that result instead of the original file
7501 name to look up the sources.
7503 Using the previous example, suppose the @file{foo-1.0} tree has been
7504 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7505 @value{GDBN} to replace @file{/usr/src} in all source path names with
7506 @file{/mnt/cross}. The first lookup will then be
7507 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7508 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7509 substitution rule, use the @code{set substitute-path} command
7510 (@pxref{set substitute-path}).
7512 To avoid unexpected substitution results, a rule is applied only if the
7513 @var{from} part of the directory name ends at a directory separator.
7514 For instance, a rule substituting @file{/usr/source} into
7515 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7516 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7517 is applied only at the beginning of the directory name, this rule will
7518 not be applied to @file{/root/usr/source/baz.c} either.
7520 In many cases, you can achieve the same result using the @code{directory}
7521 command. However, @code{set substitute-path} can be more efficient in
7522 the case where the sources are organized in a complex tree with multiple
7523 subdirectories. With the @code{directory} command, you need to add each
7524 subdirectory of your project. If you moved the entire tree while
7525 preserving its internal organization, then @code{set substitute-path}
7526 allows you to direct the debugger to all the sources with one single
7529 @code{set substitute-path} is also more than just a shortcut command.
7530 The source path is only used if the file at the original location no
7531 longer exists. On the other hand, @code{set substitute-path} modifies
7532 the debugger behavior to look at the rewritten location instead. So, if
7533 for any reason a source file that is not relevant to your executable is
7534 located at the original location, a substitution rule is the only
7535 method available to point @value{GDBN} at the new location.
7537 @cindex @samp{--with-relocated-sources}
7538 @cindex default source path substitution
7539 You can configure a default source path substitution rule by
7540 configuring @value{GDBN} with the
7541 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7542 should be the name of a directory under @value{GDBN}'s configured
7543 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7544 directory names in debug information under @var{dir} will be adjusted
7545 automatically if the installed @value{GDBN} is moved to a new
7546 location. This is useful if @value{GDBN}, libraries or executables
7547 with debug information and corresponding source code are being moved
7551 @item directory @var{dirname} @dots{}
7552 @item dir @var{dirname} @dots{}
7553 Add directory @var{dirname} to the front of the source path. Several
7554 directory names may be given to this command, separated by @samp{:}
7555 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7556 part of absolute file names) or
7557 whitespace. You may specify a directory that is already in the source
7558 path; this moves it forward, so @value{GDBN} searches it sooner.
7562 @vindex $cdir@r{, convenience variable}
7563 @vindex $cwd@r{, convenience variable}
7564 @cindex compilation directory
7565 @cindex current directory
7566 @cindex working directory
7567 @cindex directory, current
7568 @cindex directory, compilation
7569 You can use the string @samp{$cdir} to refer to the compilation
7570 directory (if one is recorded), and @samp{$cwd} to refer to the current
7571 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7572 tracks the current working directory as it changes during your @value{GDBN}
7573 session, while the latter is immediately expanded to the current
7574 directory at the time you add an entry to the source path.
7577 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7579 @c RET-repeat for @code{directory} is explicitly disabled, but since
7580 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7582 @item set directories @var{path-list}
7583 @kindex set directories
7584 Set the source path to @var{path-list}.
7585 @samp{$cdir:$cwd} are added if missing.
7587 @item show directories
7588 @kindex show directories
7589 Print the source path: show which directories it contains.
7591 @anchor{set substitute-path}
7592 @item set substitute-path @var{from} @var{to}
7593 @kindex set substitute-path
7594 Define a source path substitution rule, and add it at the end of the
7595 current list of existing substitution rules. If a rule with the same
7596 @var{from} was already defined, then the old rule is also deleted.
7598 For example, if the file @file{/foo/bar/baz.c} was moved to
7599 @file{/mnt/cross/baz.c}, then the command
7602 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7606 will tell @value{GDBN} to replace @samp{/usr/src} with
7607 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7608 @file{baz.c} even though it was moved.
7610 In the case when more than one substitution rule have been defined,
7611 the rules are evaluated one by one in the order where they have been
7612 defined. The first one matching, if any, is selected to perform
7615 For instance, if we had entered the following commands:
7618 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7619 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7623 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7624 @file{/mnt/include/defs.h} by using the first rule. However, it would
7625 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7626 @file{/mnt/src/lib/foo.c}.
7629 @item unset substitute-path [path]
7630 @kindex unset substitute-path
7631 If a path is specified, search the current list of substitution rules
7632 for a rule that would rewrite that path. Delete that rule if found.
7633 A warning is emitted by the debugger if no rule could be found.
7635 If no path is specified, then all substitution rules are deleted.
7637 @item show substitute-path [path]
7638 @kindex show substitute-path
7639 If a path is specified, then print the source path substitution rule
7640 which would rewrite that path, if any.
7642 If no path is specified, then print all existing source path substitution
7647 If your source path is cluttered with directories that are no longer of
7648 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7649 versions of source. You can correct the situation as follows:
7653 Use @code{directory} with no argument to reset the source path to its default value.
7656 Use @code{directory} with suitable arguments to reinstall the
7657 directories you want in the source path. You can add all the
7658 directories in one command.
7662 @section Source and Machine Code
7663 @cindex source line and its code address
7665 You can use the command @code{info line} to map source lines to program
7666 addresses (and vice versa), and the command @code{disassemble} to display
7667 a range of addresses as machine instructions. You can use the command
7668 @code{set disassemble-next-line} to set whether to disassemble next
7669 source line when execution stops. When run under @sc{gnu} Emacs
7670 mode, the @code{info line} command causes the arrow to point to the
7671 line specified. Also, @code{info line} prints addresses in symbolic form as
7676 @item info line @var{linespec}
7677 Print the starting and ending addresses of the compiled code for
7678 source line @var{linespec}. You can specify source lines in any of
7679 the ways documented in @ref{Specify Location}.
7682 For example, we can use @code{info line} to discover the location of
7683 the object code for the first line of function
7684 @code{m4_changequote}:
7686 @c FIXME: I think this example should also show the addresses in
7687 @c symbolic form, as they usually would be displayed.
7689 (@value{GDBP}) info line m4_changequote
7690 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7694 @cindex code address and its source line
7695 We can also inquire (using @code{*@var{addr}} as the form for
7696 @var{linespec}) what source line covers a particular address:
7698 (@value{GDBP}) info line *0x63ff
7699 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7702 @cindex @code{$_} and @code{info line}
7703 @cindex @code{x} command, default address
7704 @kindex x@r{(examine), and} info line
7705 After @code{info line}, the default address for the @code{x} command
7706 is changed to the starting address of the line, so that @samp{x/i} is
7707 sufficient to begin examining the machine code (@pxref{Memory,
7708 ,Examining Memory}). Also, this address is saved as the value of the
7709 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7714 @cindex assembly instructions
7715 @cindex instructions, assembly
7716 @cindex machine instructions
7717 @cindex listing machine instructions
7719 @itemx disassemble /m
7720 @itemx disassemble /r
7721 This specialized command dumps a range of memory as machine
7722 instructions. It can also print mixed source+disassembly by specifying
7723 the @code{/m} modifier and print the raw instructions in hex as well as
7724 in symbolic form by specifying the @code{/r}.
7725 The default memory range is the function surrounding the
7726 program counter of the selected frame. A single argument to this
7727 command is a program counter value; @value{GDBN} dumps the function
7728 surrounding this value. When two arguments are given, they should
7729 be separated by a comma, possibly surrounded by whitespace. The
7730 arguments specify a range of addresses to dump, in one of two forms:
7733 @item @var{start},@var{end}
7734 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7735 @item @var{start},+@var{length}
7736 the addresses from @var{start} (inclusive) to
7737 @code{@var{start}+@var{length}} (exclusive).
7741 When 2 arguments are specified, the name of the function is also
7742 printed (since there could be several functions in the given range).
7744 The argument(s) can be any expression yielding a numeric value, such as
7745 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7747 If the range of memory being disassembled contains current program counter,
7748 the instruction at that location is shown with a @code{=>} marker.
7751 The following example shows the disassembly of a range of addresses of
7752 HP PA-RISC 2.0 code:
7755 (@value{GDBP}) disas 0x32c4, 0x32e4
7756 Dump of assembler code from 0x32c4 to 0x32e4:
7757 0x32c4 <main+204>: addil 0,dp
7758 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7759 0x32cc <main+212>: ldil 0x3000,r31
7760 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7761 0x32d4 <main+220>: ldo 0(r31),rp
7762 0x32d8 <main+224>: addil -0x800,dp
7763 0x32dc <main+228>: ldo 0x588(r1),r26
7764 0x32e0 <main+232>: ldil 0x3000,r31
7765 End of assembler dump.
7768 Here is an example showing mixed source+assembly for Intel x86, when the
7769 program is stopped just after function prologue:
7772 (@value{GDBP}) disas /m main
7773 Dump of assembler code for function main:
7775 0x08048330 <+0>: push %ebp
7776 0x08048331 <+1>: mov %esp,%ebp
7777 0x08048333 <+3>: sub $0x8,%esp
7778 0x08048336 <+6>: and $0xfffffff0,%esp
7779 0x08048339 <+9>: sub $0x10,%esp
7781 6 printf ("Hello.\n");
7782 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7783 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7787 0x08048348 <+24>: mov $0x0,%eax
7788 0x0804834d <+29>: leave
7789 0x0804834e <+30>: ret
7791 End of assembler dump.
7794 Here is another example showing raw instructions in hex for AMD x86-64,
7797 (gdb) disas /r 0x400281,+10
7798 Dump of assembler code from 0x400281 to 0x40028b:
7799 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7800 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7801 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7802 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7803 End of assembler dump.
7806 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7807 So, for example, if you want to disassemble function @code{bar}
7808 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7809 and not @samp{disassemble foo.c:bar}.
7811 Some architectures have more than one commonly-used set of instruction
7812 mnemonics or other syntax.
7814 For programs that were dynamically linked and use shared libraries,
7815 instructions that call functions or branch to locations in the shared
7816 libraries might show a seemingly bogus location---it's actually a
7817 location of the relocation table. On some architectures, @value{GDBN}
7818 might be able to resolve these to actual function names.
7821 @kindex set disassembly-flavor
7822 @cindex Intel disassembly flavor
7823 @cindex AT&T disassembly flavor
7824 @item set disassembly-flavor @var{instruction-set}
7825 Select the instruction set to use when disassembling the
7826 program via the @code{disassemble} or @code{x/i} commands.
7828 Currently this command is only defined for the Intel x86 family. You
7829 can set @var{instruction-set} to either @code{intel} or @code{att}.
7830 The default is @code{att}, the AT&T flavor used by default by Unix
7831 assemblers for x86-based targets.
7833 @kindex show disassembly-flavor
7834 @item show disassembly-flavor
7835 Show the current setting of the disassembly flavor.
7839 @kindex set disassemble-next-line
7840 @kindex show disassemble-next-line
7841 @item set disassemble-next-line
7842 @itemx show disassemble-next-line
7843 Control whether or not @value{GDBN} will disassemble the next source
7844 line or instruction when execution stops. If ON, @value{GDBN} will
7845 display disassembly of the next source line when execution of the
7846 program being debugged stops. This is @emph{in addition} to
7847 displaying the source line itself, which @value{GDBN} always does if
7848 possible. If the next source line cannot be displayed for some reason
7849 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7850 info in the debug info), @value{GDBN} will display disassembly of the
7851 next @emph{instruction} instead of showing the next source line. If
7852 AUTO, @value{GDBN} will display disassembly of next instruction only
7853 if the source line cannot be displayed. This setting causes
7854 @value{GDBN} to display some feedback when you step through a function
7855 with no line info or whose source file is unavailable. The default is
7856 OFF, which means never display the disassembly of the next line or
7862 @chapter Examining Data
7864 @cindex printing data
7865 @cindex examining data
7868 The usual way to examine data in your program is with the @code{print}
7869 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7870 evaluates and prints the value of an expression of the language your
7871 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7872 Different Languages}). It may also print the expression using a
7873 Python-based pretty-printer (@pxref{Pretty Printing}).
7876 @item print @var{expr}
7877 @itemx print /@var{f} @var{expr}
7878 @var{expr} is an expression (in the source language). By default the
7879 value of @var{expr} is printed in a format appropriate to its data type;
7880 you can choose a different format by specifying @samp{/@var{f}}, where
7881 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7885 @itemx print /@var{f}
7886 @cindex reprint the last value
7887 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7888 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7889 conveniently inspect the same value in an alternative format.
7892 A more low-level way of examining data is with the @code{x} command.
7893 It examines data in memory at a specified address and prints it in a
7894 specified format. @xref{Memory, ,Examining Memory}.
7896 If you are interested in information about types, or about how the
7897 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7898 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7901 @cindex exploring hierarchical data structures
7903 Another way of examining values of expressions and type information is
7904 through the Python extension command @code{explore} (available only if
7905 the @value{GDBN} build is configured with @code{--with-python}). It
7906 offers an interactive way to start at the highest level (or, the most
7907 abstract level) of the data type of an expression (or, the data type
7908 itself) and explore all the way down to leaf scalar values/fields
7909 embedded in the higher level data types.
7912 @item explore @var{arg}
7913 @var{arg} is either an expression (in the source language), or a type
7914 visible in the current context of the program being debugged.
7917 The working of the @code{explore} command can be illustrated with an
7918 example. If a data type @code{struct ComplexStruct} is defined in your
7928 struct ComplexStruct
7930 struct SimpleStruct *ss_p;
7936 followed by variable declarations as
7939 struct SimpleStruct ss = @{ 10, 1.11 @};
7940 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7944 then, the value of the variable @code{cs} can be explored using the
7945 @code{explore} command as follows.
7949 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7950 the following fields:
7952 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7953 arr = <Enter 1 to explore this field of type `int [10]'>
7955 Enter the field number of choice:
7959 Since the fields of @code{cs} are not scalar values, you are being
7960 prompted to chose the field you want to explore. Let's say you choose
7961 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7962 pointer, you will be asked if it is pointing to a single value. From
7963 the declaration of @code{cs} above, it is indeed pointing to a single
7964 value, hence you enter @code{y}. If you enter @code{n}, then you will
7965 be asked if it were pointing to an array of values, in which case this
7966 field will be explored as if it were an array.
7969 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7970 Continue exploring it as a pointer to a single value [y/n]: y
7971 The value of `*(cs.ss_p)' is a struct/class of type `struct
7972 SimpleStruct' with the following fields:
7974 i = 10 .. (Value of type `int')
7975 d = 1.1100000000000001 .. (Value of type `double')
7977 Press enter to return to parent value:
7981 If the field @code{arr} of @code{cs} was chosen for exploration by
7982 entering @code{1} earlier, then since it is as array, you will be
7983 prompted to enter the index of the element in the array that you want
7987 `cs.arr' is an array of `int'.
7988 Enter the index of the element you want to explore in `cs.arr': 5
7990 `(cs.arr)[5]' is a scalar value of type `int'.
7994 Press enter to return to parent value:
7997 In general, at any stage of exploration, you can go deeper towards the
7998 leaf values by responding to the prompts appropriately, or hit the
7999 return key to return to the enclosing data structure (the @i{higher}
8000 level data structure).
8002 Similar to exploring values, you can use the @code{explore} command to
8003 explore types. Instead of specifying a value (which is typically a
8004 variable name or an expression valid in the current context of the
8005 program being debugged), you specify a type name. If you consider the
8006 same example as above, your can explore the type
8007 @code{struct ComplexStruct} by passing the argument
8008 @code{struct ComplexStruct} to the @code{explore} command.
8011 (gdb) explore struct ComplexStruct
8015 By responding to the prompts appropriately in the subsequent interactive
8016 session, you can explore the type @code{struct ComplexStruct} in a
8017 manner similar to how the value @code{cs} was explored in the above
8020 The @code{explore} command also has two sub-commands,
8021 @code{explore value} and @code{explore type}. The former sub-command is
8022 a way to explicitly specify that value exploration of the argument is
8023 being invoked, while the latter is a way to explicitly specify that type
8024 exploration of the argument is being invoked.
8027 @item explore value @var{expr}
8028 @cindex explore value
8029 This sub-command of @code{explore} explores the value of the
8030 expression @var{expr} (if @var{expr} is an expression valid in the
8031 current context of the program being debugged). The behavior of this
8032 command is identical to that of the behavior of the @code{explore}
8033 command being passed the argument @var{expr}.
8035 @item explore type @var{arg}
8036 @cindex explore type
8037 This sub-command of @code{explore} explores the type of @var{arg} (if
8038 @var{arg} is a type visible in the current context of program being
8039 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8040 is an expression valid in the current context of the program being
8041 debugged). If @var{arg} is a type, then the behavior of this command is
8042 identical to that of the @code{explore} command being passed the
8043 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8044 this command will be identical to that of the @code{explore} command
8045 being passed the type of @var{arg} as the argument.
8049 * Expressions:: Expressions
8050 * Ambiguous Expressions:: Ambiguous Expressions
8051 * Variables:: Program variables
8052 * Arrays:: Artificial arrays
8053 * Output Formats:: Output formats
8054 * Memory:: Examining memory
8055 * Auto Display:: Automatic display
8056 * Print Settings:: Print settings
8057 * Pretty Printing:: Python pretty printing
8058 * Value History:: Value history
8059 * Convenience Vars:: Convenience variables
8060 * Convenience Funs:: Convenience functions
8061 * Registers:: Registers
8062 * Floating Point Hardware:: Floating point hardware
8063 * Vector Unit:: Vector Unit
8064 * OS Information:: Auxiliary data provided by operating system
8065 * Memory Region Attributes:: Memory region attributes
8066 * Dump/Restore Files:: Copy between memory and a file
8067 * Core File Generation:: Cause a program dump its core
8068 * Character Sets:: Debugging programs that use a different
8069 character set than GDB does
8070 * Caching Target Data:: Data caching for targets
8071 * Searching Memory:: Searching memory for a sequence of bytes
8075 @section Expressions
8078 @code{print} and many other @value{GDBN} commands accept an expression and
8079 compute its value. Any kind of constant, variable or operator defined
8080 by the programming language you are using is valid in an expression in
8081 @value{GDBN}. This includes conditional expressions, function calls,
8082 casts, and string constants. It also includes preprocessor macros, if
8083 you compiled your program to include this information; see
8086 @cindex arrays in expressions
8087 @value{GDBN} supports array constants in expressions input by
8088 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8089 you can use the command @code{print @{1, 2, 3@}} to create an array
8090 of three integers. If you pass an array to a function or assign it
8091 to a program variable, @value{GDBN} copies the array to memory that
8092 is @code{malloc}ed in the target program.
8094 Because C is so widespread, most of the expressions shown in examples in
8095 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8096 Languages}, for information on how to use expressions in other
8099 In this section, we discuss operators that you can use in @value{GDBN}
8100 expressions regardless of your programming language.
8102 @cindex casts, in expressions
8103 Casts are supported in all languages, not just in C, because it is so
8104 useful to cast a number into a pointer in order to examine a structure
8105 at that address in memory.
8106 @c FIXME: casts supported---Mod2 true?
8108 @value{GDBN} supports these operators, in addition to those common
8109 to programming languages:
8113 @samp{@@} is a binary operator for treating parts of memory as arrays.
8114 @xref{Arrays, ,Artificial Arrays}, for more information.
8117 @samp{::} allows you to specify a variable in terms of the file or
8118 function where it is defined. @xref{Variables, ,Program Variables}.
8120 @cindex @{@var{type}@}
8121 @cindex type casting memory
8122 @cindex memory, viewing as typed object
8123 @cindex casts, to view memory
8124 @item @{@var{type}@} @var{addr}
8125 Refers to an object of type @var{type} stored at address @var{addr} in
8126 memory. @var{addr} may be any expression whose value is an integer or
8127 pointer (but parentheses are required around binary operators, just as in
8128 a cast). This construct is allowed regardless of what kind of data is
8129 normally supposed to reside at @var{addr}.
8132 @node Ambiguous Expressions
8133 @section Ambiguous Expressions
8134 @cindex ambiguous expressions
8136 Expressions can sometimes contain some ambiguous elements. For instance,
8137 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8138 a single function name to be defined several times, for application in
8139 different contexts. This is called @dfn{overloading}. Another example
8140 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8141 templates and is typically instantiated several times, resulting in
8142 the same function name being defined in different contexts.
8144 In some cases and depending on the language, it is possible to adjust
8145 the expression to remove the ambiguity. For instance in C@t{++}, you
8146 can specify the signature of the function you want to break on, as in
8147 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8148 qualified name of your function often makes the expression unambiguous
8151 When an ambiguity that needs to be resolved is detected, the debugger
8152 has the capability to display a menu of numbered choices for each
8153 possibility, and then waits for the selection with the prompt @samp{>}.
8154 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8155 aborts the current command. If the command in which the expression was
8156 used allows more than one choice to be selected, the next option in the
8157 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8160 For example, the following session excerpt shows an attempt to set a
8161 breakpoint at the overloaded symbol @code{String::after}.
8162 We choose three particular definitions of that function name:
8164 @c FIXME! This is likely to change to show arg type lists, at least
8167 (@value{GDBP}) b String::after
8170 [2] file:String.cc; line number:867
8171 [3] file:String.cc; line number:860
8172 [4] file:String.cc; line number:875
8173 [5] file:String.cc; line number:853
8174 [6] file:String.cc; line number:846
8175 [7] file:String.cc; line number:735
8177 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8178 Breakpoint 2 at 0xb344: file String.cc, line 875.
8179 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8180 Multiple breakpoints were set.
8181 Use the "delete" command to delete unwanted
8188 @kindex set multiple-symbols
8189 @item set multiple-symbols @var{mode}
8190 @cindex multiple-symbols menu
8192 This option allows you to adjust the debugger behavior when an expression
8195 By default, @var{mode} is set to @code{all}. If the command with which
8196 the expression is used allows more than one choice, then @value{GDBN}
8197 automatically selects all possible choices. For instance, inserting
8198 a breakpoint on a function using an ambiguous name results in a breakpoint
8199 inserted on each possible match. However, if a unique choice must be made,
8200 then @value{GDBN} uses the menu to help you disambiguate the expression.
8201 For instance, printing the address of an overloaded function will result
8202 in the use of the menu.
8204 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8205 when an ambiguity is detected.
8207 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8208 an error due to the ambiguity and the command is aborted.
8210 @kindex show multiple-symbols
8211 @item show multiple-symbols
8212 Show the current value of the @code{multiple-symbols} setting.
8216 @section Program Variables
8218 The most common kind of expression to use is the name of a variable
8221 Variables in expressions are understood in the selected stack frame
8222 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8226 global (or file-static)
8233 visible according to the scope rules of the
8234 programming language from the point of execution in that frame
8237 @noindent This means that in the function
8252 you can examine and use the variable @code{a} whenever your program is
8253 executing within the function @code{foo}, but you can only use or
8254 examine the variable @code{b} while your program is executing inside
8255 the block where @code{b} is declared.
8257 @cindex variable name conflict
8258 There is an exception: you can refer to a variable or function whose
8259 scope is a single source file even if the current execution point is not
8260 in this file. But it is possible to have more than one such variable or
8261 function with the same name (in different source files). If that
8262 happens, referring to that name has unpredictable effects. If you wish,
8263 you can specify a static variable in a particular function or file by
8264 using the colon-colon (@code{::}) notation:
8266 @cindex colon-colon, context for variables/functions
8268 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8269 @cindex @code{::}, context for variables/functions
8272 @var{file}::@var{variable}
8273 @var{function}::@var{variable}
8277 Here @var{file} or @var{function} is the name of the context for the
8278 static @var{variable}. In the case of file names, you can use quotes to
8279 make sure @value{GDBN} parses the file name as a single word---for example,
8280 to print a global value of @code{x} defined in @file{f2.c}:
8283 (@value{GDBP}) p 'f2.c'::x
8286 The @code{::} notation is normally used for referring to
8287 static variables, since you typically disambiguate uses of local variables
8288 in functions by selecting the appropriate frame and using the
8289 simple name of the variable. However, you may also use this notation
8290 to refer to local variables in frames enclosing the selected frame:
8299 process (a); /* Stop here */
8310 For example, if there is a breakpoint at the commented line,
8311 here is what you might see
8312 when the program stops after executing the call @code{bar(0)}:
8317 (@value{GDBP}) p bar::a
8320 #2 0x080483d0 in foo (a=5) at foobar.c:12
8323 (@value{GDBP}) p bar::a
8327 @cindex C@t{++} scope resolution
8328 These uses of @samp{::} are very rarely in conflict with the very
8329 similar use of the same notation in C@t{++}. When they are in
8330 conflict, the C@t{++} meaning takes precedence; however, this can be
8331 overridden by quoting the file or function name with single quotes.
8333 For example, suppose the program is stopped in a method of a class
8334 that has a field named @code{includefile}, and there is also an
8335 include file named @file{includefile} that defines a variable,
8339 (@value{GDBP}) p includefile
8341 (@value{GDBP}) p includefile::some_global
8342 A syntax error in expression, near `'.
8343 (@value{GDBP}) p 'includefile'::some_global
8347 @cindex wrong values
8348 @cindex variable values, wrong
8349 @cindex function entry/exit, wrong values of variables
8350 @cindex optimized code, wrong values of variables
8352 @emph{Warning:} Occasionally, a local variable may appear to have the
8353 wrong value at certain points in a function---just after entry to a new
8354 scope, and just before exit.
8356 You may see this problem when you are stepping by machine instructions.
8357 This is because, on most machines, it takes more than one instruction to
8358 set up a stack frame (including local variable definitions); if you are
8359 stepping by machine instructions, variables may appear to have the wrong
8360 values until the stack frame is completely built. On exit, it usually
8361 also takes more than one machine instruction to destroy a stack frame;
8362 after you begin stepping through that group of instructions, local
8363 variable definitions may be gone.
8365 This may also happen when the compiler does significant optimizations.
8366 To be sure of always seeing accurate values, turn off all optimization
8369 @cindex ``No symbol "foo" in current context''
8370 Another possible effect of compiler optimizations is to optimize
8371 unused variables out of existence, or assign variables to registers (as
8372 opposed to memory addresses). Depending on the support for such cases
8373 offered by the debug info format used by the compiler, @value{GDBN}
8374 might not be able to display values for such local variables. If that
8375 happens, @value{GDBN} will print a message like this:
8378 No symbol "foo" in current context.
8381 To solve such problems, either recompile without optimizations, or use a
8382 different debug info format, if the compiler supports several such
8383 formats. @xref{Compilation}, for more information on choosing compiler
8384 options. @xref{C, ,C and C@t{++}}, for more information about debug
8385 info formats that are best suited to C@t{++} programs.
8387 If you ask to print an object whose contents are unknown to
8388 @value{GDBN}, e.g., because its data type is not completely specified
8389 by the debug information, @value{GDBN} will say @samp{<incomplete
8390 type>}. @xref{Symbols, incomplete type}, for more about this.
8392 If you append @kbd{@@entry} string to a function parameter name you get its
8393 value at the time the function got called. If the value is not available an
8394 error message is printed. Entry values are available only with some compilers.
8395 Entry values are normally also printed at the function parameter list according
8396 to @ref{set print entry-values}.
8399 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8405 (gdb) print i@@entry
8409 Strings are identified as arrays of @code{char} values without specified
8410 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8411 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8412 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8413 defines literal string type @code{"char"} as @code{char} without a sign.
8418 signed char var1[] = "A";
8421 You get during debugging
8426 $2 = @{65 'A', 0 '\0'@}
8430 @section Artificial Arrays
8432 @cindex artificial array
8434 @kindex @@@r{, referencing memory as an array}
8435 It is often useful to print out several successive objects of the
8436 same type in memory; a section of an array, or an array of
8437 dynamically determined size for which only a pointer exists in the
8440 You can do this by referring to a contiguous span of memory as an
8441 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8442 operand of @samp{@@} should be the first element of the desired array
8443 and be an individual object. The right operand should be the desired length
8444 of the array. The result is an array value whose elements are all of
8445 the type of the left argument. The first element is actually the left
8446 argument; the second element comes from bytes of memory immediately
8447 following those that hold the first element, and so on. Here is an
8448 example. If a program says
8451 int *array = (int *) malloc (len * sizeof (int));
8455 you can print the contents of @code{array} with
8461 The left operand of @samp{@@} must reside in memory. Array values made
8462 with @samp{@@} in this way behave just like other arrays in terms of
8463 subscripting, and are coerced to pointers when used in expressions.
8464 Artificial arrays most often appear in expressions via the value history
8465 (@pxref{Value History, ,Value History}), after printing one out.
8467 Another way to create an artificial array is to use a cast.
8468 This re-interprets a value as if it were an array.
8469 The value need not be in memory:
8471 (@value{GDBP}) p/x (short[2])0x12345678
8472 $1 = @{0x1234, 0x5678@}
8475 As a convenience, if you leave the array length out (as in
8476 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8477 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8479 (@value{GDBP}) p/x (short[])0x12345678
8480 $2 = @{0x1234, 0x5678@}
8483 Sometimes the artificial array mechanism is not quite enough; in
8484 moderately complex data structures, the elements of interest may not
8485 actually be adjacent---for example, if you are interested in the values
8486 of pointers in an array. One useful work-around in this situation is
8487 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8488 Variables}) as a counter in an expression that prints the first
8489 interesting value, and then repeat that expression via @key{RET}. For
8490 instance, suppose you have an array @code{dtab} of pointers to
8491 structures, and you are interested in the values of a field @code{fv}
8492 in each structure. Here is an example of what you might type:
8502 @node Output Formats
8503 @section Output Formats
8505 @cindex formatted output
8506 @cindex output formats
8507 By default, @value{GDBN} prints a value according to its data type. Sometimes
8508 this is not what you want. For example, you might want to print a number
8509 in hex, or a pointer in decimal. Or you might want to view data in memory
8510 at a certain address as a character string or as an instruction. To do
8511 these things, specify an @dfn{output format} when you print a value.
8513 The simplest use of output formats is to say how to print a value
8514 already computed. This is done by starting the arguments of the
8515 @code{print} command with a slash and a format letter. The format
8516 letters supported are:
8520 Regard the bits of the value as an integer, and print the integer in
8524 Print as integer in signed decimal.
8527 Print as integer in unsigned decimal.
8530 Print as integer in octal.
8533 Print as integer in binary. The letter @samp{t} stands for ``two''.
8534 @footnote{@samp{b} cannot be used because these format letters are also
8535 used with the @code{x} command, where @samp{b} stands for ``byte'';
8536 see @ref{Memory,,Examining Memory}.}
8539 @cindex unknown address, locating
8540 @cindex locate address
8541 Print as an address, both absolute in hexadecimal and as an offset from
8542 the nearest preceding symbol. You can use this format used to discover
8543 where (in what function) an unknown address is located:
8546 (@value{GDBP}) p/a 0x54320
8547 $3 = 0x54320 <_initialize_vx+396>
8551 The command @code{info symbol 0x54320} yields similar results.
8552 @xref{Symbols, info symbol}.
8555 Regard as an integer and print it as a character constant. This
8556 prints both the numerical value and its character representation. The
8557 character representation is replaced with the octal escape @samp{\nnn}
8558 for characters outside the 7-bit @sc{ascii} range.
8560 Without this format, @value{GDBN} displays @code{char},
8561 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8562 constants. Single-byte members of vectors are displayed as integer
8566 Regard the bits of the value as a floating point number and print
8567 using typical floating point syntax.
8570 @cindex printing strings
8571 @cindex printing byte arrays
8572 Regard as a string, if possible. With this format, pointers to single-byte
8573 data are displayed as null-terminated strings and arrays of single-byte data
8574 are displayed as fixed-length strings. Other values are displayed in their
8577 Without this format, @value{GDBN} displays pointers to and arrays of
8578 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8579 strings. Single-byte members of a vector are displayed as an integer
8583 Like @samp{x} formatting, the value is treated as an integer and
8584 printed as hexadecimal, but leading zeros are printed to pad the value
8585 to the size of the integer type.
8588 @cindex raw printing
8589 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8590 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8591 Printing}). This typically results in a higher-level display of the
8592 value's contents. The @samp{r} format bypasses any Python
8593 pretty-printer which might exist.
8596 For example, to print the program counter in hex (@pxref{Registers}), type
8603 Note that no space is required before the slash; this is because command
8604 names in @value{GDBN} cannot contain a slash.
8606 To reprint the last value in the value history with a different format,
8607 you can use the @code{print} command with just a format and no
8608 expression. For example, @samp{p/x} reprints the last value in hex.
8611 @section Examining Memory
8613 You can use the command @code{x} (for ``examine'') to examine memory in
8614 any of several formats, independently of your program's data types.
8616 @cindex examining memory
8618 @kindex x @r{(examine memory)}
8619 @item x/@var{nfu} @var{addr}
8622 Use the @code{x} command to examine memory.
8625 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8626 much memory to display and how to format it; @var{addr} is an
8627 expression giving the address where you want to start displaying memory.
8628 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8629 Several commands set convenient defaults for @var{addr}.
8632 @item @var{n}, the repeat count
8633 The repeat count is a decimal integer; the default is 1. It specifies
8634 how much memory (counting by units @var{u}) to display.
8635 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8638 @item @var{f}, the display format
8639 The display format is one of the formats used by @code{print}
8640 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8641 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8642 The default is @samp{x} (hexadecimal) initially. The default changes
8643 each time you use either @code{x} or @code{print}.
8645 @item @var{u}, the unit size
8646 The unit size is any of
8652 Halfwords (two bytes).
8654 Words (four bytes). This is the initial default.
8656 Giant words (eight bytes).
8659 Each time you specify a unit size with @code{x}, that size becomes the
8660 default unit the next time you use @code{x}. For the @samp{i} format,
8661 the unit size is ignored and is normally not written. For the @samp{s} format,
8662 the unit size defaults to @samp{b}, unless it is explicitly given.
8663 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8664 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8665 Note that the results depend on the programming language of the
8666 current compilation unit. If the language is C, the @samp{s}
8667 modifier will use the UTF-16 encoding while @samp{w} will use
8668 UTF-32. The encoding is set by the programming language and cannot
8671 @item @var{addr}, starting display address
8672 @var{addr} is the address where you want @value{GDBN} to begin displaying
8673 memory. The expression need not have a pointer value (though it may);
8674 it is always interpreted as an integer address of a byte of memory.
8675 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8676 @var{addr} is usually just after the last address examined---but several
8677 other commands also set the default address: @code{info breakpoints} (to
8678 the address of the last breakpoint listed), @code{info line} (to the
8679 starting address of a line), and @code{print} (if you use it to display
8680 a value from memory).
8683 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8684 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8685 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8686 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8687 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8689 Since the letters indicating unit sizes are all distinct from the
8690 letters specifying output formats, you do not have to remember whether
8691 unit size or format comes first; either order works. The output
8692 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8693 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8695 Even though the unit size @var{u} is ignored for the formats @samp{s}
8696 and @samp{i}, you might still want to use a count @var{n}; for example,
8697 @samp{3i} specifies that you want to see three machine instructions,
8698 including any operands. For convenience, especially when used with
8699 the @code{display} command, the @samp{i} format also prints branch delay
8700 slot instructions, if any, beyond the count specified, which immediately
8701 follow the last instruction that is within the count. The command
8702 @code{disassemble} gives an alternative way of inspecting machine
8703 instructions; see @ref{Machine Code,,Source and Machine Code}.
8705 All the defaults for the arguments to @code{x} are designed to make it
8706 easy to continue scanning memory with minimal specifications each time
8707 you use @code{x}. For example, after you have inspected three machine
8708 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8709 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8710 the repeat count @var{n} is used again; the other arguments default as
8711 for successive uses of @code{x}.
8713 When examining machine instructions, the instruction at current program
8714 counter is shown with a @code{=>} marker. For example:
8717 (@value{GDBP}) x/5i $pc-6
8718 0x804837f <main+11>: mov %esp,%ebp
8719 0x8048381 <main+13>: push %ecx
8720 0x8048382 <main+14>: sub $0x4,%esp
8721 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8722 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8725 @cindex @code{$_}, @code{$__}, and value history
8726 The addresses and contents printed by the @code{x} command are not saved
8727 in the value history because there is often too much of them and they
8728 would get in the way. Instead, @value{GDBN} makes these values available for
8729 subsequent use in expressions as values of the convenience variables
8730 @code{$_} and @code{$__}. After an @code{x} command, the last address
8731 examined is available for use in expressions in the convenience variable
8732 @code{$_}. The contents of that address, as examined, are available in
8733 the convenience variable @code{$__}.
8735 If the @code{x} command has a repeat count, the address and contents saved
8736 are from the last memory unit printed; this is not the same as the last
8737 address printed if several units were printed on the last line of output.
8739 @cindex remote memory comparison
8740 @cindex verify remote memory image
8741 When you are debugging a program running on a remote target machine
8742 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8743 remote machine's memory against the executable file you downloaded to
8744 the target. The @code{compare-sections} command is provided for such
8748 @kindex compare-sections
8749 @item compare-sections @r{[}@var{section-name}@r{]}
8750 Compare the data of a loadable section @var{section-name} in the
8751 executable file of the program being debugged with the same section in
8752 the remote machine's memory, and report any mismatches. With no
8753 arguments, compares all loadable sections. This command's
8754 availability depends on the target's support for the @code{"qCRC"}
8759 @section Automatic Display
8760 @cindex automatic display
8761 @cindex display of expressions
8763 If you find that you want to print the value of an expression frequently
8764 (to see how it changes), you might want to add it to the @dfn{automatic
8765 display list} so that @value{GDBN} prints its value each time your program stops.
8766 Each expression added to the list is given a number to identify it;
8767 to remove an expression from the list, you specify that number.
8768 The automatic display looks like this:
8772 3: bar[5] = (struct hack *) 0x3804
8776 This display shows item numbers, expressions and their current values. As with
8777 displays you request manually using @code{x} or @code{print}, you can
8778 specify the output format you prefer; in fact, @code{display} decides
8779 whether to use @code{print} or @code{x} depending your format
8780 specification---it uses @code{x} if you specify either the @samp{i}
8781 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8785 @item display @var{expr}
8786 Add the expression @var{expr} to the list of expressions to display
8787 each time your program stops. @xref{Expressions, ,Expressions}.
8789 @code{display} does not repeat if you press @key{RET} again after using it.
8791 @item display/@var{fmt} @var{expr}
8792 For @var{fmt} specifying only a display format and not a size or
8793 count, add the expression @var{expr} to the auto-display list but
8794 arrange to display it each time in the specified format @var{fmt}.
8795 @xref{Output Formats,,Output Formats}.
8797 @item display/@var{fmt} @var{addr}
8798 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8799 number of units, add the expression @var{addr} as a memory address to
8800 be examined each time your program stops. Examining means in effect
8801 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8804 For example, @samp{display/i $pc} can be helpful, to see the machine
8805 instruction about to be executed each time execution stops (@samp{$pc}
8806 is a common name for the program counter; @pxref{Registers, ,Registers}).
8809 @kindex delete display
8811 @item undisplay @var{dnums}@dots{}
8812 @itemx delete display @var{dnums}@dots{}
8813 Remove items from the list of expressions to display. Specify the
8814 numbers of the displays that you want affected with the command
8815 argument @var{dnums}. It can be a single display number, one of the
8816 numbers shown in the first field of the @samp{info display} display;
8817 or it could be a range of display numbers, as in @code{2-4}.
8819 @code{undisplay} does not repeat if you press @key{RET} after using it.
8820 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8822 @kindex disable display
8823 @item disable display @var{dnums}@dots{}
8824 Disable the display of item numbers @var{dnums}. A disabled display
8825 item is not printed automatically, but is not forgotten. It may be
8826 enabled again later. Specify the numbers of the displays that you
8827 want affected with the command argument @var{dnums}. It can be a
8828 single display number, one of the numbers shown in the first field of
8829 the @samp{info display} display; or it could be a range of display
8830 numbers, as in @code{2-4}.
8832 @kindex enable display
8833 @item enable display @var{dnums}@dots{}
8834 Enable display of item numbers @var{dnums}. It becomes effective once
8835 again in auto display of its expression, until you specify otherwise.
8836 Specify the numbers of the displays that you want affected with the
8837 command argument @var{dnums}. It can be a single display number, one
8838 of the numbers shown in the first field of the @samp{info display}
8839 display; or it could be a range of display numbers, as in @code{2-4}.
8842 Display the current values of the expressions on the list, just as is
8843 done when your program stops.
8845 @kindex info display
8847 Print the list of expressions previously set up to display
8848 automatically, each one with its item number, but without showing the
8849 values. This includes disabled expressions, which are marked as such.
8850 It also includes expressions which would not be displayed right now
8851 because they refer to automatic variables not currently available.
8854 @cindex display disabled out of scope
8855 If a display expression refers to local variables, then it does not make
8856 sense outside the lexical context for which it was set up. Such an
8857 expression is disabled when execution enters a context where one of its
8858 variables is not defined. For example, if you give the command
8859 @code{display last_char} while inside a function with an argument
8860 @code{last_char}, @value{GDBN} displays this argument while your program
8861 continues to stop inside that function. When it stops elsewhere---where
8862 there is no variable @code{last_char}---the display is disabled
8863 automatically. The next time your program stops where @code{last_char}
8864 is meaningful, you can enable the display expression once again.
8866 @node Print Settings
8867 @section Print Settings
8869 @cindex format options
8870 @cindex print settings
8871 @value{GDBN} provides the following ways to control how arrays, structures,
8872 and symbols are printed.
8875 These settings are useful for debugging programs in any language:
8879 @item set print address
8880 @itemx set print address on
8881 @cindex print/don't print memory addresses
8882 @value{GDBN} prints memory addresses showing the location of stack
8883 traces, structure values, pointer values, breakpoints, and so forth,
8884 even when it also displays the contents of those addresses. The default
8885 is @code{on}. For example, this is what a stack frame display looks like with
8886 @code{set print address on}:
8891 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8893 530 if (lquote != def_lquote)
8897 @item set print address off
8898 Do not print addresses when displaying their contents. For example,
8899 this is the same stack frame displayed with @code{set print address off}:
8903 (@value{GDBP}) set print addr off
8905 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8906 530 if (lquote != def_lquote)
8910 You can use @samp{set print address off} to eliminate all machine
8911 dependent displays from the @value{GDBN} interface. For example, with
8912 @code{print address off}, you should get the same text for backtraces on
8913 all machines---whether or not they involve pointer arguments.
8916 @item show print address
8917 Show whether or not addresses are to be printed.
8920 When @value{GDBN} prints a symbolic address, it normally prints the
8921 closest earlier symbol plus an offset. If that symbol does not uniquely
8922 identify the address (for example, it is a name whose scope is a single
8923 source file), you may need to clarify. One way to do this is with
8924 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8925 you can set @value{GDBN} to print the source file and line number when
8926 it prints a symbolic address:
8929 @item set print symbol-filename on
8930 @cindex source file and line of a symbol
8931 @cindex symbol, source file and line
8932 Tell @value{GDBN} to print the source file name and line number of a
8933 symbol in the symbolic form of an address.
8935 @item set print symbol-filename off
8936 Do not print source file name and line number of a symbol. This is the
8939 @item show print symbol-filename
8940 Show whether or not @value{GDBN} will print the source file name and
8941 line number of a symbol in the symbolic form of an address.
8944 Another situation where it is helpful to show symbol filenames and line
8945 numbers is when disassembling code; @value{GDBN} shows you the line
8946 number and source file that corresponds to each instruction.
8948 Also, you may wish to see the symbolic form only if the address being
8949 printed is reasonably close to the closest earlier symbol:
8952 @item set print max-symbolic-offset @var{max-offset}
8953 @itemx set print max-symbolic-offset unlimited
8954 @cindex maximum value for offset of closest symbol
8955 Tell @value{GDBN} to only display the symbolic form of an address if the
8956 offset between the closest earlier symbol and the address is less than
8957 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8958 to always print the symbolic form of an address if any symbol precedes
8959 it. Zero is equivalent to @code{unlimited}.
8961 @item show print max-symbolic-offset
8962 Ask how large the maximum offset is that @value{GDBN} prints in a
8966 @cindex wild pointer, interpreting
8967 @cindex pointer, finding referent
8968 If you have a pointer and you are not sure where it points, try
8969 @samp{set print symbol-filename on}. Then you can determine the name
8970 and source file location of the variable where it points, using
8971 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8972 For example, here @value{GDBN} shows that a variable @code{ptt} points
8973 at another variable @code{t}, defined in @file{hi2.c}:
8976 (@value{GDBP}) set print symbol-filename on
8977 (@value{GDBP}) p/a ptt
8978 $4 = 0xe008 <t in hi2.c>
8982 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8983 does not show the symbol name and filename of the referent, even with
8984 the appropriate @code{set print} options turned on.
8987 You can also enable @samp{/a}-like formatting all the time using
8988 @samp{set print symbol on}:
8991 @item set print symbol on
8992 Tell @value{GDBN} to print the symbol corresponding to an address, if
8995 @item set print symbol off
8996 Tell @value{GDBN} not to print the symbol corresponding to an
8997 address. In this mode, @value{GDBN} will still print the symbol
8998 corresponding to pointers to functions. This is the default.
9000 @item show print symbol
9001 Show whether @value{GDBN} will display the symbol corresponding to an
9005 Other settings control how different kinds of objects are printed:
9008 @item set print array
9009 @itemx set print array on
9010 @cindex pretty print arrays
9011 Pretty print arrays. This format is more convenient to read,
9012 but uses more space. The default is off.
9014 @item set print array off
9015 Return to compressed format for arrays.
9017 @item show print array
9018 Show whether compressed or pretty format is selected for displaying
9021 @cindex print array indexes
9022 @item set print array-indexes
9023 @itemx set print array-indexes on
9024 Print the index of each element when displaying arrays. May be more
9025 convenient to locate a given element in the array or quickly find the
9026 index of a given element in that printed array. The default is off.
9028 @item set print array-indexes off
9029 Stop printing element indexes when displaying arrays.
9031 @item show print array-indexes
9032 Show whether the index of each element is printed when displaying
9035 @item set print elements @var{number-of-elements}
9036 @itemx set print elements unlimited
9037 @cindex number of array elements to print
9038 @cindex limit on number of printed array elements
9039 Set a limit on how many elements of an array @value{GDBN} will print.
9040 If @value{GDBN} is printing a large array, it stops printing after it has
9041 printed the number of elements set by the @code{set print elements} command.
9042 This limit also applies to the display of strings.
9043 When @value{GDBN} starts, this limit is set to 200.
9044 Setting @var{number-of-elements} to @code{unlimited} or zero means
9045 that the number of elements to print is unlimited.
9047 @item show print elements
9048 Display the number of elements of a large array that @value{GDBN} will print.
9049 If the number is 0, then the printing is unlimited.
9051 @item set print frame-arguments @var{value}
9052 @kindex set print frame-arguments
9053 @cindex printing frame argument values
9054 @cindex print all frame argument values
9055 @cindex print frame argument values for scalars only
9056 @cindex do not print frame argument values
9057 This command allows to control how the values of arguments are printed
9058 when the debugger prints a frame (@pxref{Frames}). The possible
9063 The values of all arguments are printed.
9066 Print the value of an argument only if it is a scalar. The value of more
9067 complex arguments such as arrays, structures, unions, etc, is replaced
9068 by @code{@dots{}}. This is the default. Here is an example where
9069 only scalar arguments are shown:
9072 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9077 None of the argument values are printed. Instead, the value of each argument
9078 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9081 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9086 By default, only scalar arguments are printed. This command can be used
9087 to configure the debugger to print the value of all arguments, regardless
9088 of their type. However, it is often advantageous to not print the value
9089 of more complex parameters. For instance, it reduces the amount of
9090 information printed in each frame, making the backtrace more readable.
9091 Also, it improves performance when displaying Ada frames, because
9092 the computation of large arguments can sometimes be CPU-intensive,
9093 especially in large applications. Setting @code{print frame-arguments}
9094 to @code{scalars} (the default) or @code{none} avoids this computation,
9095 thus speeding up the display of each Ada frame.
9097 @item show print frame-arguments
9098 Show how the value of arguments should be displayed when printing a frame.
9100 @item set print raw frame-arguments on
9101 Print frame arguments in raw, non pretty-printed, form.
9103 @item set print raw frame-arguments off
9104 Print frame arguments in pretty-printed form, if there is a pretty-printer
9105 for the value (@pxref{Pretty Printing}),
9106 otherwise print the value in raw form.
9107 This is the default.
9109 @item show print raw frame-arguments
9110 Show whether to print frame arguments in raw form.
9112 @anchor{set print entry-values}
9113 @item set print entry-values @var{value}
9114 @kindex set print entry-values
9115 Set printing of frame argument values at function entry. In some cases
9116 @value{GDBN} can determine the value of function argument which was passed by
9117 the function caller, even if the value was modified inside the called function
9118 and therefore is different. With optimized code, the current value could be
9119 unavailable, but the entry value may still be known.
9121 The default value is @code{default} (see below for its description). Older
9122 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9123 this feature will behave in the @code{default} setting the same way as with the
9126 This functionality is currently supported only by DWARF 2 debugging format and
9127 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9128 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9131 The @var{value} parameter can be one of the following:
9135 Print only actual parameter values, never print values from function entry
9139 #0 different (val=6)
9140 #0 lost (val=<optimized out>)
9142 #0 invalid (val=<optimized out>)
9146 Print only parameter values from function entry point. The actual parameter
9147 values are never printed.
9149 #0 equal (val@@entry=5)
9150 #0 different (val@@entry=5)
9151 #0 lost (val@@entry=5)
9152 #0 born (val@@entry=<optimized out>)
9153 #0 invalid (val@@entry=<optimized out>)
9157 Print only parameter values from function entry point. If value from function
9158 entry point is not known while the actual value is known, print the actual
9159 value for such parameter.
9161 #0 equal (val@@entry=5)
9162 #0 different (val@@entry=5)
9163 #0 lost (val@@entry=5)
9165 #0 invalid (val@@entry=<optimized out>)
9169 Print actual parameter values. If actual parameter value is not known while
9170 value from function entry point is known, print the entry point value for such
9174 #0 different (val=6)
9175 #0 lost (val@@entry=5)
9177 #0 invalid (val=<optimized out>)
9181 Always print both the actual parameter value and its value from function entry
9182 point, even if values of one or both are not available due to compiler
9185 #0 equal (val=5, val@@entry=5)
9186 #0 different (val=6, val@@entry=5)
9187 #0 lost (val=<optimized out>, val@@entry=5)
9188 #0 born (val=10, val@@entry=<optimized out>)
9189 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9193 Print the actual parameter value if it is known and also its value from
9194 function entry point if it is known. If neither is known, print for the actual
9195 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9196 values are known and identical, print the shortened
9197 @code{param=param@@entry=VALUE} notation.
9199 #0 equal (val=val@@entry=5)
9200 #0 different (val=6, val@@entry=5)
9201 #0 lost (val@@entry=5)
9203 #0 invalid (val=<optimized out>)
9207 Always print the actual parameter value. Print also its value from function
9208 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9209 if both values are known and identical, print the shortened
9210 @code{param=param@@entry=VALUE} notation.
9212 #0 equal (val=val@@entry=5)
9213 #0 different (val=6, val@@entry=5)
9214 #0 lost (val=<optimized out>, val@@entry=5)
9216 #0 invalid (val=<optimized out>)
9220 For analysis messages on possible failures of frame argument values at function
9221 entry resolution see @ref{set debug entry-values}.
9223 @item show print entry-values
9224 Show the method being used for printing of frame argument values at function
9227 @item set print repeats @var{number-of-repeats}
9228 @itemx set print repeats unlimited
9229 @cindex repeated array elements
9230 Set the threshold for suppressing display of repeated array
9231 elements. When the number of consecutive identical elements of an
9232 array exceeds the threshold, @value{GDBN} prints the string
9233 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9234 identical repetitions, instead of displaying the identical elements
9235 themselves. Setting the threshold to @code{unlimited} or zero will
9236 cause all elements to be individually printed. The default threshold
9239 @item show print repeats
9240 Display the current threshold for printing repeated identical
9243 @item set print null-stop
9244 @cindex @sc{null} elements in arrays
9245 Cause @value{GDBN} to stop printing the characters of an array when the first
9246 @sc{null} is encountered. This is useful when large arrays actually
9247 contain only short strings.
9250 @item show print null-stop
9251 Show whether @value{GDBN} stops printing an array on the first
9252 @sc{null} character.
9254 @item set print pretty on
9255 @cindex print structures in indented form
9256 @cindex indentation in structure display
9257 Cause @value{GDBN} to print structures in an indented format with one member
9258 per line, like this:
9273 @item set print pretty off
9274 Cause @value{GDBN} to print structures in a compact format, like this:
9278 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9279 meat = 0x54 "Pork"@}
9284 This is the default format.
9286 @item show print pretty
9287 Show which format @value{GDBN} is using to print structures.
9289 @item set print sevenbit-strings on
9290 @cindex eight-bit characters in strings
9291 @cindex octal escapes in strings
9292 Print using only seven-bit characters; if this option is set,
9293 @value{GDBN} displays any eight-bit characters (in strings or
9294 character values) using the notation @code{\}@var{nnn}. This setting is
9295 best if you are working in English (@sc{ascii}) and you use the
9296 high-order bit of characters as a marker or ``meta'' bit.
9298 @item set print sevenbit-strings off
9299 Print full eight-bit characters. This allows the use of more
9300 international character sets, and is the default.
9302 @item show print sevenbit-strings
9303 Show whether or not @value{GDBN} is printing only seven-bit characters.
9305 @item set print union on
9306 @cindex unions in structures, printing
9307 Tell @value{GDBN} to print unions which are contained in structures
9308 and other unions. This is the default setting.
9310 @item set print union off
9311 Tell @value{GDBN} not to print unions which are contained in
9312 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9315 @item show print union
9316 Ask @value{GDBN} whether or not it will print unions which are contained in
9317 structures and other unions.
9319 For example, given the declarations
9322 typedef enum @{Tree, Bug@} Species;
9323 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9324 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9335 struct thing foo = @{Tree, @{Acorn@}@};
9339 with @code{set print union on} in effect @samp{p foo} would print
9342 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9346 and with @code{set print union off} in effect it would print
9349 $1 = @{it = Tree, form = @{...@}@}
9353 @code{set print union} affects programs written in C-like languages
9359 These settings are of interest when debugging C@t{++} programs:
9362 @cindex demangling C@t{++} names
9363 @item set print demangle
9364 @itemx set print demangle on
9365 Print C@t{++} names in their source form rather than in the encoded
9366 (``mangled'') form passed to the assembler and linker for type-safe
9367 linkage. The default is on.
9369 @item show print demangle
9370 Show whether C@t{++} names are printed in mangled or demangled form.
9372 @item set print asm-demangle
9373 @itemx set print asm-demangle on
9374 Print C@t{++} names in their source form rather than their mangled form, even
9375 in assembler code printouts such as instruction disassemblies.
9378 @item show print asm-demangle
9379 Show whether C@t{++} names in assembly listings are printed in mangled
9382 @cindex C@t{++} symbol decoding style
9383 @cindex symbol decoding style, C@t{++}
9384 @kindex set demangle-style
9385 @item set demangle-style @var{style}
9386 Choose among several encoding schemes used by different compilers to
9387 represent C@t{++} names. The choices for @var{style} are currently:
9391 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9392 This is the default.
9395 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9398 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9401 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9404 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9405 @strong{Warning:} this setting alone is not sufficient to allow
9406 debugging @code{cfront}-generated executables. @value{GDBN} would
9407 require further enhancement to permit that.
9410 If you omit @var{style}, you will see a list of possible formats.
9412 @item show demangle-style
9413 Display the encoding style currently in use for decoding C@t{++} symbols.
9415 @item set print object
9416 @itemx set print object on
9417 @cindex derived type of an object, printing
9418 @cindex display derived types
9419 When displaying a pointer to an object, identify the @emph{actual}
9420 (derived) type of the object rather than the @emph{declared} type, using
9421 the virtual function table. Note that the virtual function table is
9422 required---this feature can only work for objects that have run-time
9423 type identification; a single virtual method in the object's declared
9424 type is sufficient. Note that this setting is also taken into account when
9425 working with variable objects via MI (@pxref{GDB/MI}).
9427 @item set print object off
9428 Display only the declared type of objects, without reference to the
9429 virtual function table. This is the default setting.
9431 @item show print object
9432 Show whether actual, or declared, object types are displayed.
9434 @item set print static-members
9435 @itemx set print static-members on
9436 @cindex static members of C@t{++} objects
9437 Print static members when displaying a C@t{++} object. The default is on.
9439 @item set print static-members off
9440 Do not print static members when displaying a C@t{++} object.
9442 @item show print static-members
9443 Show whether C@t{++} static members are printed or not.
9445 @item set print pascal_static-members
9446 @itemx set print pascal_static-members on
9447 @cindex static members of Pascal objects
9448 @cindex Pascal objects, static members display
9449 Print static members when displaying a Pascal object. The default is on.
9451 @item set print pascal_static-members off
9452 Do not print static members when displaying a Pascal object.
9454 @item show print pascal_static-members
9455 Show whether Pascal static members are printed or not.
9457 @c These don't work with HP ANSI C++ yet.
9458 @item set print vtbl
9459 @itemx set print vtbl on
9460 @cindex pretty print C@t{++} virtual function tables
9461 @cindex virtual functions (C@t{++}) display
9462 @cindex VTBL display
9463 Pretty print C@t{++} virtual function tables. The default is off.
9464 (The @code{vtbl} commands do not work on programs compiled with the HP
9465 ANSI C@t{++} compiler (@code{aCC}).)
9467 @item set print vtbl off
9468 Do not pretty print C@t{++} virtual function tables.
9470 @item show print vtbl
9471 Show whether C@t{++} virtual function tables are pretty printed, or not.
9474 @node Pretty Printing
9475 @section Pretty Printing
9477 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9478 Python code. It greatly simplifies the display of complex objects. This
9479 mechanism works for both MI and the CLI.
9482 * Pretty-Printer Introduction:: Introduction to pretty-printers
9483 * Pretty-Printer Example:: An example pretty-printer
9484 * Pretty-Printer Commands:: Pretty-printer commands
9487 @node Pretty-Printer Introduction
9488 @subsection Pretty-Printer Introduction
9490 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9491 registered for the value. If there is then @value{GDBN} invokes the
9492 pretty-printer to print the value. Otherwise the value is printed normally.
9494 Pretty-printers are normally named. This makes them easy to manage.
9495 The @samp{info pretty-printer} command will list all the installed
9496 pretty-printers with their names.
9497 If a pretty-printer can handle multiple data types, then its
9498 @dfn{subprinters} are the printers for the individual data types.
9499 Each such subprinter has its own name.
9500 The format of the name is @var{printer-name};@var{subprinter-name}.
9502 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9503 Typically they are automatically loaded and registered when the corresponding
9504 debug information is loaded, thus making them available without having to
9505 do anything special.
9507 There are three places where a pretty-printer can be registered.
9511 Pretty-printers registered globally are available when debugging
9515 Pretty-printers registered with a program space are available only
9516 when debugging that program.
9517 @xref{Progspaces In Python}, for more details on program spaces in Python.
9520 Pretty-printers registered with an objfile are loaded and unloaded
9521 with the corresponding objfile (e.g., shared library).
9522 @xref{Objfiles In Python}, for more details on objfiles in Python.
9525 @xref{Selecting Pretty-Printers}, for further information on how
9526 pretty-printers are selected,
9528 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9531 @node Pretty-Printer Example
9532 @subsection Pretty-Printer Example
9534 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9537 (@value{GDBP}) print s
9539 static npos = 4294967295,
9541 <std::allocator<char>> = @{
9542 <__gnu_cxx::new_allocator<char>> = @{
9543 <No data fields>@}, <No data fields>
9545 members of std::basic_string<char, std::char_traits<char>,
9546 std::allocator<char> >::_Alloc_hider:
9547 _M_p = 0x804a014 "abcd"
9552 With a pretty-printer for @code{std::string} only the contents are printed:
9555 (@value{GDBP}) print s
9559 @node Pretty-Printer Commands
9560 @subsection Pretty-Printer Commands
9561 @cindex pretty-printer commands
9564 @kindex info pretty-printer
9565 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9566 Print the list of installed pretty-printers.
9567 This includes disabled pretty-printers, which are marked as such.
9569 @var{object-regexp} is a regular expression matching the objects
9570 whose pretty-printers to list.
9571 Objects can be @code{global}, the program space's file
9572 (@pxref{Progspaces In Python}),
9573 and the object files within that program space (@pxref{Objfiles In Python}).
9574 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9575 looks up a printer from these three objects.
9577 @var{name-regexp} is a regular expression matching the name of the printers
9580 @kindex disable pretty-printer
9581 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9582 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9583 A disabled pretty-printer is not forgotten, it may be enabled again later.
9585 @kindex enable pretty-printer
9586 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9587 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9592 Suppose we have three pretty-printers installed: one from library1.so
9593 named @code{foo} that prints objects of type @code{foo}, and
9594 another from library2.so named @code{bar} that prints two types of objects,
9595 @code{bar1} and @code{bar2}.
9598 (gdb) info pretty-printer
9605 (gdb) info pretty-printer library2
9610 (gdb) disable pretty-printer library1
9612 2 of 3 printers enabled
9613 (gdb) info pretty-printer
9620 (gdb) disable pretty-printer library2 bar:bar1
9622 1 of 3 printers enabled
9623 (gdb) info pretty-printer library2
9630 (gdb) disable pretty-printer library2 bar
9632 0 of 3 printers enabled
9633 (gdb) info pretty-printer library2
9642 Note that for @code{bar} the entire printer can be disabled,
9643 as can each individual subprinter.
9646 @section Value History
9648 @cindex value history
9649 @cindex history of values printed by @value{GDBN}
9650 Values printed by the @code{print} command are saved in the @value{GDBN}
9651 @dfn{value history}. This allows you to refer to them in other expressions.
9652 Values are kept until the symbol table is re-read or discarded
9653 (for example with the @code{file} or @code{symbol-file} commands).
9654 When the symbol table changes, the value history is discarded,
9655 since the values may contain pointers back to the types defined in the
9660 @cindex history number
9661 The values printed are given @dfn{history numbers} by which you can
9662 refer to them. These are successive integers starting with one.
9663 @code{print} shows you the history number assigned to a value by
9664 printing @samp{$@var{num} = } before the value; here @var{num} is the
9667 To refer to any previous value, use @samp{$} followed by the value's
9668 history number. The way @code{print} labels its output is designed to
9669 remind you of this. Just @code{$} refers to the most recent value in
9670 the history, and @code{$$} refers to the value before that.
9671 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9672 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9673 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9675 For example, suppose you have just printed a pointer to a structure and
9676 want to see the contents of the structure. It suffices to type
9682 If you have a chain of structures where the component @code{next} points
9683 to the next one, you can print the contents of the next one with this:
9690 You can print successive links in the chain by repeating this
9691 command---which you can do by just typing @key{RET}.
9693 Note that the history records values, not expressions. If the value of
9694 @code{x} is 4 and you type these commands:
9702 then the value recorded in the value history by the @code{print} command
9703 remains 4 even though the value of @code{x} has changed.
9708 Print the last ten values in the value history, with their item numbers.
9709 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9710 values} does not change the history.
9712 @item show values @var{n}
9713 Print ten history values centered on history item number @var{n}.
9716 Print ten history values just after the values last printed. If no more
9717 values are available, @code{show values +} produces no display.
9720 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9721 same effect as @samp{show values +}.
9723 @node Convenience Vars
9724 @section Convenience Variables
9726 @cindex convenience variables
9727 @cindex user-defined variables
9728 @value{GDBN} provides @dfn{convenience variables} that you can use within
9729 @value{GDBN} to hold on to a value and refer to it later. These variables
9730 exist entirely within @value{GDBN}; they are not part of your program, and
9731 setting a convenience variable has no direct effect on further execution
9732 of your program. That is why you can use them freely.
9734 Convenience variables are prefixed with @samp{$}. Any name preceded by
9735 @samp{$} can be used for a convenience variable, unless it is one of
9736 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9737 (Value history references, in contrast, are @emph{numbers} preceded
9738 by @samp{$}. @xref{Value History, ,Value History}.)
9740 You can save a value in a convenience variable with an assignment
9741 expression, just as you would set a variable in your program.
9745 set $foo = *object_ptr
9749 would save in @code{$foo} the value contained in the object pointed to by
9752 Using a convenience variable for the first time creates it, but its
9753 value is @code{void} until you assign a new value. You can alter the
9754 value with another assignment at any time.
9756 Convenience variables have no fixed types. You can assign a convenience
9757 variable any type of value, including structures and arrays, even if
9758 that variable already has a value of a different type. The convenience
9759 variable, when used as an expression, has the type of its current value.
9762 @kindex show convenience
9763 @cindex show all user variables and functions
9764 @item show convenience
9765 Print a list of convenience variables used so far, and their values,
9766 as well as a list of the convenience functions.
9767 Abbreviated @code{show conv}.
9769 @kindex init-if-undefined
9770 @cindex convenience variables, initializing
9771 @item init-if-undefined $@var{variable} = @var{expression}
9772 Set a convenience variable if it has not already been set. This is useful
9773 for user-defined commands that keep some state. It is similar, in concept,
9774 to using local static variables with initializers in C (except that
9775 convenience variables are global). It can also be used to allow users to
9776 override default values used in a command script.
9778 If the variable is already defined then the expression is not evaluated so
9779 any side-effects do not occur.
9782 One of the ways to use a convenience variable is as a counter to be
9783 incremented or a pointer to be advanced. For example, to print
9784 a field from successive elements of an array of structures:
9788 print bar[$i++]->contents
9792 Repeat that command by typing @key{RET}.
9794 Some convenience variables are created automatically by @value{GDBN} and given
9795 values likely to be useful.
9798 @vindex $_@r{, convenience variable}
9800 The variable @code{$_} is automatically set by the @code{x} command to
9801 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9802 commands which provide a default address for @code{x} to examine also
9803 set @code{$_} to that address; these commands include @code{info line}
9804 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9805 except when set by the @code{x} command, in which case it is a pointer
9806 to the type of @code{$__}.
9808 @vindex $__@r{, convenience variable}
9810 The variable @code{$__} is automatically set by the @code{x} command
9811 to the value found in the last address examined. Its type is chosen
9812 to match the format in which the data was printed.
9815 @vindex $_exitcode@r{, convenience variable}
9816 When the program being debugged terminates normally, @value{GDBN}
9817 automatically sets this variable to the exit code of the program, and
9818 resets @code{$_exitsignal} to @code{void}.
9821 @vindex $_exitsignal@r{, convenience variable}
9822 When the program being debugged dies due to an uncaught signal,
9823 @value{GDBN} automatically sets this variable to that signal's number,
9824 and resets @code{$_exitcode} to @code{void}.
9826 To distinguish between whether the program being debugged has exited
9827 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
9828 @code{$_exitsignal} is not @code{void}), the convenience function
9829 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
9830 Functions}). For example, considering the following source code:
9836 main (int argc, char *argv[])
9843 A valid way of telling whether the program being debugged has exited
9844 or signalled would be:
9847 (@value{GDBP}) define has_exited_or_signalled
9848 Type commands for definition of ``has_exited_or_signalled''.
9849 End with a line saying just ``end''.
9850 >if $_isvoid ($_exitsignal)
9851 >echo The program has exited\n
9853 >echo The program has signalled\n
9859 Program terminated with signal SIGALRM, Alarm clock.
9860 The program no longer exists.
9861 (@value{GDBP}) has_exited_or_signalled
9862 The program has signalled
9865 As can be seen, @value{GDBN} correctly informs that the program being
9866 debugged has signalled, since it calls @code{raise} and raises a
9867 @code{SIGALRM} signal. If the program being debugged had not called
9868 @code{raise}, then @value{GDBN} would report a normal exit:
9871 (@value{GDBP}) has_exited_or_signalled
9872 The program has exited
9876 The variable @code{$_exception} is set to the exception object being
9877 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
9880 @itemx $_probe_arg0@dots{}$_probe_arg11
9881 Arguments to a static probe. @xref{Static Probe Points}.
9884 @vindex $_sdata@r{, inspect, convenience variable}
9885 The variable @code{$_sdata} contains extra collected static tracepoint
9886 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9887 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9888 if extra static tracepoint data has not been collected.
9891 @vindex $_siginfo@r{, convenience variable}
9892 The variable @code{$_siginfo} contains extra signal information
9893 (@pxref{extra signal information}). Note that @code{$_siginfo}
9894 could be empty, if the application has not yet received any signals.
9895 For example, it will be empty before you execute the @code{run} command.
9898 @vindex $_tlb@r{, convenience variable}
9899 The variable @code{$_tlb} is automatically set when debugging
9900 applications running on MS-Windows in native mode or connected to
9901 gdbserver that supports the @code{qGetTIBAddr} request.
9902 @xref{General Query Packets}.
9903 This variable contains the address of the thread information block.
9907 On HP-UX systems, if you refer to a function or variable name that
9908 begins with a dollar sign, @value{GDBN} searches for a user or system
9909 name first, before it searches for a convenience variable.
9911 @node Convenience Funs
9912 @section Convenience Functions
9914 @cindex convenience functions
9915 @value{GDBN} also supplies some @dfn{convenience functions}. These
9916 have a syntax similar to convenience variables. A convenience
9917 function can be used in an expression just like an ordinary function;
9918 however, a convenience function is implemented internally to
9921 These functions do not require @value{GDBN} to be configured with
9922 @code{Python} support, which means that they are always available.
9926 @item $_isvoid (@var{expr})
9927 @findex $_isvoid@r{, convenience function}
9928 Return one if the expression @var{expr} is @code{void}. Otherwise it
9931 A @code{void} expression is an expression where the type of the result
9932 is @code{void}. For example, you can examine a convenience variable
9933 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
9937 (@value{GDBP}) print $_exitcode
9939 (@value{GDBP}) print $_isvoid ($_exitcode)
9942 Starting program: ./a.out
9943 [Inferior 1 (process 29572) exited normally]
9944 (@value{GDBP}) print $_exitcode
9946 (@value{GDBP}) print $_isvoid ($_exitcode)
9950 In the example above, we used @code{$_isvoid} to check whether
9951 @code{$_exitcode} is @code{void} before and after the execution of the
9952 program being debugged. Before the execution there is no exit code to
9953 be examined, therefore @code{$_exitcode} is @code{void}. After the
9954 execution the program being debugged returned zero, therefore
9955 @code{$_exitcode} is zero, which means that it is not @code{void}
9958 The @code{void} expression can also be a call of a function from the
9959 program being debugged. For example, given the following function:
9968 The result of calling it inside @value{GDBN} is @code{void}:
9971 (@value{GDBP}) print foo ()
9973 (@value{GDBP}) print $_isvoid (foo ())
9975 (@value{GDBP}) set $v = foo ()
9976 (@value{GDBP}) print $v
9978 (@value{GDBP}) print $_isvoid ($v)
9984 These functions require @value{GDBN} to be configured with
9985 @code{Python} support.
9989 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9990 @findex $_memeq@r{, convenience function}
9991 Returns one if the @var{length} bytes at the addresses given by
9992 @var{buf1} and @var{buf2} are equal.
9993 Otherwise it returns zero.
9995 @item $_regex(@var{str}, @var{regex})
9996 @findex $_regex@r{, convenience function}
9997 Returns one if the string @var{str} matches the regular expression
9998 @var{regex}. Otherwise it returns zero.
9999 The syntax of the regular expression is that specified by @code{Python}'s
10000 regular expression support.
10002 @item $_streq(@var{str1}, @var{str2})
10003 @findex $_streq@r{, convenience function}
10004 Returns one if the strings @var{str1} and @var{str2} are equal.
10005 Otherwise it returns zero.
10007 @item $_strlen(@var{str})
10008 @findex $_strlen@r{, convenience function}
10009 Returns the length of string @var{str}.
10013 @value{GDBN} provides the ability to list and get help on
10014 convenience functions.
10017 @item help function
10018 @kindex help function
10019 @cindex show all convenience functions
10020 Print a list of all convenience functions.
10027 You can refer to machine register contents, in expressions, as variables
10028 with names starting with @samp{$}. The names of registers are different
10029 for each machine; use @code{info registers} to see the names used on
10033 @kindex info registers
10034 @item info registers
10035 Print the names and values of all registers except floating-point
10036 and vector registers (in the selected stack frame).
10038 @kindex info all-registers
10039 @cindex floating point registers
10040 @item info all-registers
10041 Print the names and values of all registers, including floating-point
10042 and vector registers (in the selected stack frame).
10044 @item info registers @var{regname} @dots{}
10045 Print the @dfn{relativized} value of each specified register @var{regname}.
10046 As discussed in detail below, register values are normally relative to
10047 the selected stack frame. @var{regname} may be any register name valid on
10048 the machine you are using, with or without the initial @samp{$}.
10051 @cindex stack pointer register
10052 @cindex program counter register
10053 @cindex process status register
10054 @cindex frame pointer register
10055 @cindex standard registers
10056 @value{GDBN} has four ``standard'' register names that are available (in
10057 expressions) on most machines---whenever they do not conflict with an
10058 architecture's canonical mnemonics for registers. The register names
10059 @code{$pc} and @code{$sp} are used for the program counter register and
10060 the stack pointer. @code{$fp} is used for a register that contains a
10061 pointer to the current stack frame, and @code{$ps} is used for a
10062 register that contains the processor status. For example,
10063 you could print the program counter in hex with
10070 or print the instruction to be executed next with
10077 or add four to the stack pointer@footnote{This is a way of removing
10078 one word from the stack, on machines where stacks grow downward in
10079 memory (most machines, nowadays). This assumes that the innermost
10080 stack frame is selected; setting @code{$sp} is not allowed when other
10081 stack frames are selected. To pop entire frames off the stack,
10082 regardless of machine architecture, use @code{return};
10083 see @ref{Returning, ,Returning from a Function}.} with
10089 Whenever possible, these four standard register names are available on
10090 your machine even though the machine has different canonical mnemonics,
10091 so long as there is no conflict. The @code{info registers} command
10092 shows the canonical names. For example, on the SPARC, @code{info
10093 registers} displays the processor status register as @code{$psr} but you
10094 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10095 is an alias for the @sc{eflags} register.
10097 @value{GDBN} always considers the contents of an ordinary register as an
10098 integer when the register is examined in this way. Some machines have
10099 special registers which can hold nothing but floating point; these
10100 registers are considered to have floating point values. There is no way
10101 to refer to the contents of an ordinary register as floating point value
10102 (although you can @emph{print} it as a floating point value with
10103 @samp{print/f $@var{regname}}).
10105 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10106 means that the data format in which the register contents are saved by
10107 the operating system is not the same one that your program normally
10108 sees. For example, the registers of the 68881 floating point
10109 coprocessor are always saved in ``extended'' (raw) format, but all C
10110 programs expect to work with ``double'' (virtual) format. In such
10111 cases, @value{GDBN} normally works with the virtual format only (the format
10112 that makes sense for your program), but the @code{info registers} command
10113 prints the data in both formats.
10115 @cindex SSE registers (x86)
10116 @cindex MMX registers (x86)
10117 Some machines have special registers whose contents can be interpreted
10118 in several different ways. For example, modern x86-based machines
10119 have SSE and MMX registers that can hold several values packed
10120 together in several different formats. @value{GDBN} refers to such
10121 registers in @code{struct} notation:
10124 (@value{GDBP}) print $xmm1
10126 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10127 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10128 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10129 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10130 v4_int32 = @{0, 20657912, 11, 13@},
10131 v2_int64 = @{88725056443645952, 55834574859@},
10132 uint128 = 0x0000000d0000000b013b36f800000000
10137 To set values of such registers, you need to tell @value{GDBN} which
10138 view of the register you wish to change, as if you were assigning
10139 value to a @code{struct} member:
10142 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10145 Normally, register values are relative to the selected stack frame
10146 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10147 value that the register would contain if all stack frames farther in
10148 were exited and their saved registers restored. In order to see the
10149 true contents of hardware registers, you must select the innermost
10150 frame (with @samp{frame 0}).
10152 @cindex caller-saved registers
10153 @cindex call-clobbered registers
10154 @cindex volatile registers
10155 @cindex <not saved> values
10156 Usually ABIs reserve some registers as not needed to be saved by the
10157 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10158 registers). It may therefore not be possible for @value{GDBN} to know
10159 the value a register had before the call (in other words, in the outer
10160 frame), if the register value has since been changed by the callee.
10161 @value{GDBN} tries to deduce where the inner frame saved
10162 (``callee-saved'') registers, from the debug info, unwind info, or the
10163 machine code generated by your compiler. If some register is not
10164 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10165 its own knowledge of the ABI, or because the debug/unwind info
10166 explicitly says the register's value is undefined), @value{GDBN}
10167 displays @w{@samp{<not saved>}} as the register's value. With targets
10168 that @value{GDBN} has no knowledge of the register saving convention,
10169 if a register was not saved by the callee, then its value and location
10170 in the outer frame are assumed to be the same of the inner frame.
10171 This is usually harmless, because if the register is call-clobbered,
10172 the caller either does not care what is in the register after the
10173 call, or has code to restore the value that it does care about. Note,
10174 however, that if you change such a register in the outer frame, you
10175 may also be affecting the inner frame. Also, the more ``outer'' the
10176 frame is you're looking at, the more likely a call-clobbered
10177 register's value is to be wrong, in the sense that it doesn't actually
10178 represent the value the register had just before the call.
10180 @node Floating Point Hardware
10181 @section Floating Point Hardware
10182 @cindex floating point
10184 Depending on the configuration, @value{GDBN} may be able to give
10185 you more information about the status of the floating point hardware.
10190 Display hardware-dependent information about the floating
10191 point unit. The exact contents and layout vary depending on the
10192 floating point chip. Currently, @samp{info float} is supported on
10193 the ARM and x86 machines.
10197 @section Vector Unit
10198 @cindex vector unit
10200 Depending on the configuration, @value{GDBN} may be able to give you
10201 more information about the status of the vector unit.
10204 @kindex info vector
10206 Display information about the vector unit. The exact contents and
10207 layout vary depending on the hardware.
10210 @node OS Information
10211 @section Operating System Auxiliary Information
10212 @cindex OS information
10214 @value{GDBN} provides interfaces to useful OS facilities that can help
10215 you debug your program.
10217 @cindex auxiliary vector
10218 @cindex vector, auxiliary
10219 Some operating systems supply an @dfn{auxiliary vector} to programs at
10220 startup. This is akin to the arguments and environment that you
10221 specify for a program, but contains a system-dependent variety of
10222 binary values that tell system libraries important details about the
10223 hardware, operating system, and process. Each value's purpose is
10224 identified by an integer tag; the meanings are well-known but system-specific.
10225 Depending on the configuration and operating system facilities,
10226 @value{GDBN} may be able to show you this information. For remote
10227 targets, this functionality may further depend on the remote stub's
10228 support of the @samp{qXfer:auxv:read} packet, see
10229 @ref{qXfer auxiliary vector read}.
10234 Display the auxiliary vector of the inferior, which can be either a
10235 live process or a core dump file. @value{GDBN} prints each tag value
10236 numerically, and also shows names and text descriptions for recognized
10237 tags. Some values in the vector are numbers, some bit masks, and some
10238 pointers to strings or other data. @value{GDBN} displays each value in the
10239 most appropriate form for a recognized tag, and in hexadecimal for
10240 an unrecognized tag.
10243 On some targets, @value{GDBN} can access operating system-specific
10244 information and show it to you. The types of information available
10245 will differ depending on the type of operating system running on the
10246 target. The mechanism used to fetch the data is described in
10247 @ref{Operating System Information}. For remote targets, this
10248 functionality depends on the remote stub's support of the
10249 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10253 @item info os @var{infotype}
10255 Display OS information of the requested type.
10257 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10259 @anchor{linux info os infotypes}
10261 @kindex info os processes
10263 Display the list of processes on the target. For each process,
10264 @value{GDBN} prints the process identifier, the name of the user, the
10265 command corresponding to the process, and the list of processor cores
10266 that the process is currently running on. (To understand what these
10267 properties mean, for this and the following info types, please consult
10268 the general @sc{gnu}/Linux documentation.)
10270 @kindex info os procgroups
10272 Display the list of process groups on the target. For each process,
10273 @value{GDBN} prints the identifier of the process group that it belongs
10274 to, the command corresponding to the process group leader, the process
10275 identifier, and the command line of the process. The list is sorted
10276 first by the process group identifier, then by the process identifier,
10277 so that processes belonging to the same process group are grouped together
10278 and the process group leader is listed first.
10280 @kindex info os threads
10282 Display the list of threads running on the target. For each thread,
10283 @value{GDBN} prints the identifier of the process that the thread
10284 belongs to, the command of the process, the thread identifier, and the
10285 processor core that it is currently running on. The main thread of a
10286 process is not listed.
10288 @kindex info os files
10290 Display the list of open file descriptors on the target. For each
10291 file descriptor, @value{GDBN} prints the identifier of the process
10292 owning the descriptor, the command of the owning process, the value
10293 of the descriptor, and the target of the descriptor.
10295 @kindex info os sockets
10297 Display the list of Internet-domain sockets on the target. For each
10298 socket, @value{GDBN} prints the address and port of the local and
10299 remote endpoints, the current state of the connection, the creator of
10300 the socket, the IP address family of the socket, and the type of the
10303 @kindex info os shm
10305 Display the list of all System V shared-memory regions on the target.
10306 For each shared-memory region, @value{GDBN} prints the region key,
10307 the shared-memory identifier, the access permissions, the size of the
10308 region, the process that created the region, the process that last
10309 attached to or detached from the region, the current number of live
10310 attaches to the region, and the times at which the region was last
10311 attached to, detach from, and changed.
10313 @kindex info os semaphores
10315 Display the list of all System V semaphore sets on the target. For each
10316 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10317 set identifier, the access permissions, the number of semaphores in the
10318 set, the user and group of the owner and creator of the semaphore set,
10319 and the times at which the semaphore set was operated upon and changed.
10321 @kindex info os msg
10323 Display the list of all System V message queues on the target. For each
10324 message queue, @value{GDBN} prints the message queue key, the message
10325 queue identifier, the access permissions, the current number of bytes
10326 on the queue, the current number of messages on the queue, the processes
10327 that last sent and received a message on the queue, the user and group
10328 of the owner and creator of the message queue, the times at which a
10329 message was last sent and received on the queue, and the time at which
10330 the message queue was last changed.
10332 @kindex info os modules
10334 Display the list of all loaded kernel modules on the target. For each
10335 module, @value{GDBN} prints the module name, the size of the module in
10336 bytes, the number of times the module is used, the dependencies of the
10337 module, the status of the module, and the address of the loaded module
10342 If @var{infotype} is omitted, then list the possible values for
10343 @var{infotype} and the kind of OS information available for each
10344 @var{infotype}. If the target does not return a list of possible
10345 types, this command will report an error.
10348 @node Memory Region Attributes
10349 @section Memory Region Attributes
10350 @cindex memory region attributes
10352 @dfn{Memory region attributes} allow you to describe special handling
10353 required by regions of your target's memory. @value{GDBN} uses
10354 attributes to determine whether to allow certain types of memory
10355 accesses; whether to use specific width accesses; and whether to cache
10356 target memory. By default the description of memory regions is
10357 fetched from the target (if the current target supports this), but the
10358 user can override the fetched regions.
10360 Defined memory regions can be individually enabled and disabled. When a
10361 memory region is disabled, @value{GDBN} uses the default attributes when
10362 accessing memory in that region. Similarly, if no memory regions have
10363 been defined, @value{GDBN} uses the default attributes when accessing
10366 When a memory region is defined, it is given a number to identify it;
10367 to enable, disable, or remove a memory region, you specify that number.
10371 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10372 Define a memory region bounded by @var{lower} and @var{upper} with
10373 attributes @var{attributes}@dots{}, and add it to the list of regions
10374 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10375 case: it is treated as the target's maximum memory address.
10376 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10379 Discard any user changes to the memory regions and use target-supplied
10380 regions, if available, or no regions if the target does not support.
10383 @item delete mem @var{nums}@dots{}
10384 Remove memory regions @var{nums}@dots{} from the list of regions
10385 monitored by @value{GDBN}.
10387 @kindex disable mem
10388 @item disable mem @var{nums}@dots{}
10389 Disable monitoring of memory regions @var{nums}@dots{}.
10390 A disabled memory region is not forgotten.
10391 It may be enabled again later.
10394 @item enable mem @var{nums}@dots{}
10395 Enable monitoring of memory regions @var{nums}@dots{}.
10399 Print a table of all defined memory regions, with the following columns
10403 @item Memory Region Number
10404 @item Enabled or Disabled.
10405 Enabled memory regions are marked with @samp{y}.
10406 Disabled memory regions are marked with @samp{n}.
10409 The address defining the inclusive lower bound of the memory region.
10412 The address defining the exclusive upper bound of the memory region.
10415 The list of attributes set for this memory region.
10420 @subsection Attributes
10422 @subsubsection Memory Access Mode
10423 The access mode attributes set whether @value{GDBN} may make read or
10424 write accesses to a memory region.
10426 While these attributes prevent @value{GDBN} from performing invalid
10427 memory accesses, they do nothing to prevent the target system, I/O DMA,
10428 etc.@: from accessing memory.
10432 Memory is read only.
10434 Memory is write only.
10436 Memory is read/write. This is the default.
10439 @subsubsection Memory Access Size
10440 The access size attribute tells @value{GDBN} to use specific sized
10441 accesses in the memory region. Often memory mapped device registers
10442 require specific sized accesses. If no access size attribute is
10443 specified, @value{GDBN} may use accesses of any size.
10447 Use 8 bit memory accesses.
10449 Use 16 bit memory accesses.
10451 Use 32 bit memory accesses.
10453 Use 64 bit memory accesses.
10456 @c @subsubsection Hardware/Software Breakpoints
10457 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10458 @c will use hardware or software breakpoints for the internal breakpoints
10459 @c used by the step, next, finish, until, etc. commands.
10463 @c Always use hardware breakpoints
10464 @c @item swbreak (default)
10467 @subsubsection Data Cache
10468 The data cache attributes set whether @value{GDBN} will cache target
10469 memory. While this generally improves performance by reducing debug
10470 protocol overhead, it can lead to incorrect results because @value{GDBN}
10471 does not know about volatile variables or memory mapped device
10476 Enable @value{GDBN} to cache target memory.
10478 Disable @value{GDBN} from caching target memory. This is the default.
10481 @subsection Memory Access Checking
10482 @value{GDBN} can be instructed to refuse accesses to memory that is
10483 not explicitly described. This can be useful if accessing such
10484 regions has undesired effects for a specific target, or to provide
10485 better error checking. The following commands control this behaviour.
10488 @kindex set mem inaccessible-by-default
10489 @item set mem inaccessible-by-default [on|off]
10490 If @code{on} is specified, make @value{GDBN} treat memory not
10491 explicitly described by the memory ranges as non-existent and refuse accesses
10492 to such memory. The checks are only performed if there's at least one
10493 memory range defined. If @code{off} is specified, make @value{GDBN}
10494 treat the memory not explicitly described by the memory ranges as RAM.
10495 The default value is @code{on}.
10496 @kindex show mem inaccessible-by-default
10497 @item show mem inaccessible-by-default
10498 Show the current handling of accesses to unknown memory.
10502 @c @subsubsection Memory Write Verification
10503 @c The memory write verification attributes set whether @value{GDBN}
10504 @c will re-reads data after each write to verify the write was successful.
10508 @c @item noverify (default)
10511 @node Dump/Restore Files
10512 @section Copy Between Memory and a File
10513 @cindex dump/restore files
10514 @cindex append data to a file
10515 @cindex dump data to a file
10516 @cindex restore data from a file
10518 You can use the commands @code{dump}, @code{append}, and
10519 @code{restore} to copy data between target memory and a file. The
10520 @code{dump} and @code{append} commands write data to a file, and the
10521 @code{restore} command reads data from a file back into the inferior's
10522 memory. Files may be in binary, Motorola S-record, Intel hex, or
10523 Tektronix Hex format; however, @value{GDBN} can only append to binary
10529 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10530 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10531 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10532 or the value of @var{expr}, to @var{filename} in the given format.
10534 The @var{format} parameter may be any one of:
10541 Motorola S-record format.
10543 Tektronix Hex format.
10546 @value{GDBN} uses the same definitions of these formats as the
10547 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10548 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10552 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10553 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10554 Append the contents of memory from @var{start_addr} to @var{end_addr},
10555 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10556 (@value{GDBN} can only append data to files in raw binary form.)
10559 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10560 Restore the contents of file @var{filename} into memory. The
10561 @code{restore} command can automatically recognize any known @sc{bfd}
10562 file format, except for raw binary. To restore a raw binary file you
10563 must specify the optional keyword @code{binary} after the filename.
10565 If @var{bias} is non-zero, its value will be added to the addresses
10566 contained in the file. Binary files always start at address zero, so
10567 they will be restored at address @var{bias}. Other bfd files have
10568 a built-in location; they will be restored at offset @var{bias}
10569 from that location.
10571 If @var{start} and/or @var{end} are non-zero, then only data between
10572 file offset @var{start} and file offset @var{end} will be restored.
10573 These offsets are relative to the addresses in the file, before
10574 the @var{bias} argument is applied.
10578 @node Core File Generation
10579 @section How to Produce a Core File from Your Program
10580 @cindex dump core from inferior
10582 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10583 image of a running process and its process status (register values
10584 etc.). Its primary use is post-mortem debugging of a program that
10585 crashed while it ran outside a debugger. A program that crashes
10586 automatically produces a core file, unless this feature is disabled by
10587 the user. @xref{Files}, for information on invoking @value{GDBN} in
10588 the post-mortem debugging mode.
10590 Occasionally, you may wish to produce a core file of the program you
10591 are debugging in order to preserve a snapshot of its state.
10592 @value{GDBN} has a special command for that.
10596 @kindex generate-core-file
10597 @item generate-core-file [@var{file}]
10598 @itemx gcore [@var{file}]
10599 Produce a core dump of the inferior process. The optional argument
10600 @var{file} specifies the file name where to put the core dump. If not
10601 specified, the file name defaults to @file{core.@var{pid}}, where
10602 @var{pid} is the inferior process ID.
10604 Note that this command is implemented only for some systems (as of
10605 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10608 @node Character Sets
10609 @section Character Sets
10610 @cindex character sets
10612 @cindex translating between character sets
10613 @cindex host character set
10614 @cindex target character set
10616 If the program you are debugging uses a different character set to
10617 represent characters and strings than the one @value{GDBN} uses itself,
10618 @value{GDBN} can automatically translate between the character sets for
10619 you. The character set @value{GDBN} uses we call the @dfn{host
10620 character set}; the one the inferior program uses we call the
10621 @dfn{target character set}.
10623 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10624 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10625 remote protocol (@pxref{Remote Debugging}) to debug a program
10626 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10627 then the host character set is Latin-1, and the target character set is
10628 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10629 target-charset EBCDIC-US}, then @value{GDBN} translates between
10630 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10631 character and string literals in expressions.
10633 @value{GDBN} has no way to automatically recognize which character set
10634 the inferior program uses; you must tell it, using the @code{set
10635 target-charset} command, described below.
10637 Here are the commands for controlling @value{GDBN}'s character set
10641 @item set target-charset @var{charset}
10642 @kindex set target-charset
10643 Set the current target character set to @var{charset}. To display the
10644 list of supported target character sets, type
10645 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10647 @item set host-charset @var{charset}
10648 @kindex set host-charset
10649 Set the current host character set to @var{charset}.
10651 By default, @value{GDBN} uses a host character set appropriate to the
10652 system it is running on; you can override that default using the
10653 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10654 automatically determine the appropriate host character set. In this
10655 case, @value{GDBN} uses @samp{UTF-8}.
10657 @value{GDBN} can only use certain character sets as its host character
10658 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10659 @value{GDBN} will list the host character sets it supports.
10661 @item set charset @var{charset}
10662 @kindex set charset
10663 Set the current host and target character sets to @var{charset}. As
10664 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10665 @value{GDBN} will list the names of the character sets that can be used
10666 for both host and target.
10669 @kindex show charset
10670 Show the names of the current host and target character sets.
10672 @item show host-charset
10673 @kindex show host-charset
10674 Show the name of the current host character set.
10676 @item show target-charset
10677 @kindex show target-charset
10678 Show the name of the current target character set.
10680 @item set target-wide-charset @var{charset}
10681 @kindex set target-wide-charset
10682 Set the current target's wide character set to @var{charset}. This is
10683 the character set used by the target's @code{wchar_t} type. To
10684 display the list of supported wide character sets, type
10685 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10687 @item show target-wide-charset
10688 @kindex show target-wide-charset
10689 Show the name of the current target's wide character set.
10692 Here is an example of @value{GDBN}'s character set support in action.
10693 Assume that the following source code has been placed in the file
10694 @file{charset-test.c}:
10700 = @{72, 101, 108, 108, 111, 44, 32, 119,
10701 111, 114, 108, 100, 33, 10, 0@};
10702 char ibm1047_hello[]
10703 = @{200, 133, 147, 147, 150, 107, 64, 166,
10704 150, 153, 147, 132, 90, 37, 0@};
10708 printf ("Hello, world!\n");
10712 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10713 containing the string @samp{Hello, world!} followed by a newline,
10714 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10716 We compile the program, and invoke the debugger on it:
10719 $ gcc -g charset-test.c -o charset-test
10720 $ gdb -nw charset-test
10721 GNU gdb 2001-12-19-cvs
10722 Copyright 2001 Free Software Foundation, Inc.
10727 We can use the @code{show charset} command to see what character sets
10728 @value{GDBN} is currently using to interpret and display characters and
10732 (@value{GDBP}) show charset
10733 The current host and target character set is `ISO-8859-1'.
10737 For the sake of printing this manual, let's use @sc{ascii} as our
10738 initial character set:
10740 (@value{GDBP}) set charset ASCII
10741 (@value{GDBP}) show charset
10742 The current host and target character set is `ASCII'.
10746 Let's assume that @sc{ascii} is indeed the correct character set for our
10747 host system --- in other words, let's assume that if @value{GDBN} prints
10748 characters using the @sc{ascii} character set, our terminal will display
10749 them properly. Since our current target character set is also
10750 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10753 (@value{GDBP}) print ascii_hello
10754 $1 = 0x401698 "Hello, world!\n"
10755 (@value{GDBP}) print ascii_hello[0]
10760 @value{GDBN} uses the target character set for character and string
10761 literals you use in expressions:
10764 (@value{GDBP}) print '+'
10769 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10772 @value{GDBN} relies on the user to tell it which character set the
10773 target program uses. If we print @code{ibm1047_hello} while our target
10774 character set is still @sc{ascii}, we get jibberish:
10777 (@value{GDBP}) print ibm1047_hello
10778 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10779 (@value{GDBP}) print ibm1047_hello[0]
10784 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10785 @value{GDBN} tells us the character sets it supports:
10788 (@value{GDBP}) set target-charset
10789 ASCII EBCDIC-US IBM1047 ISO-8859-1
10790 (@value{GDBP}) set target-charset
10793 We can select @sc{ibm1047} as our target character set, and examine the
10794 program's strings again. Now the @sc{ascii} string is wrong, but
10795 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10796 target character set, @sc{ibm1047}, to the host character set,
10797 @sc{ascii}, and they display correctly:
10800 (@value{GDBP}) set target-charset IBM1047
10801 (@value{GDBP}) show charset
10802 The current host character set is `ASCII'.
10803 The current target character set is `IBM1047'.
10804 (@value{GDBP}) print ascii_hello
10805 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10806 (@value{GDBP}) print ascii_hello[0]
10808 (@value{GDBP}) print ibm1047_hello
10809 $8 = 0x4016a8 "Hello, world!\n"
10810 (@value{GDBP}) print ibm1047_hello[0]
10815 As above, @value{GDBN} uses the target character set for character and
10816 string literals you use in expressions:
10819 (@value{GDBP}) print '+'
10824 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10827 @node Caching Target Data
10828 @section Caching Data of Targets
10829 @cindex caching data of targets
10831 @value{GDBN} caches data exchanged between the debugger and a target.
10832 Each cache is associated with the address space of the inferior.
10833 @xref{Inferiors and Programs}, about inferior and address space.
10834 Such caching generally improves performance in remote debugging
10835 (@pxref{Remote Debugging}), because it reduces the overhead of the
10836 remote protocol by bundling memory reads and writes into large chunks.
10837 Unfortunately, simply caching everything would lead to incorrect results,
10838 since @value{GDBN} does not necessarily know anything about volatile
10839 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
10840 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
10842 Therefore, by default, @value{GDBN} only caches data
10843 known to be on the stack@footnote{In non-stop mode, it is moderately
10844 rare for a running thread to modify the stack of a stopped thread
10845 in a way that would interfere with a backtrace, and caching of
10846 stack reads provides a significant speed up of remote backtraces.} or
10847 in the code segment.
10848 Other regions of memory can be explicitly marked as
10849 cacheable; @pxref{Memory Region Attributes}.
10852 @kindex set remotecache
10853 @item set remotecache on
10854 @itemx set remotecache off
10855 This option no longer does anything; it exists for compatibility
10858 @kindex show remotecache
10859 @item show remotecache
10860 Show the current state of the obsolete remotecache flag.
10862 @kindex set stack-cache
10863 @item set stack-cache on
10864 @itemx set stack-cache off
10865 Enable or disable caching of stack accesses. When @code{on}, use
10866 caching. By default, this option is @code{on}.
10868 @kindex show stack-cache
10869 @item show stack-cache
10870 Show the current state of data caching for memory accesses.
10872 @kindex set code-cache
10873 @item set code-cache on
10874 @itemx set code-cache off
10875 Enable or disable caching of code segment accesses. When @code{on},
10876 use caching. By default, this option is @code{on}. This improves
10877 performance of disassembly in remote debugging.
10879 @kindex show code-cache
10880 @item show code-cache
10881 Show the current state of target memory cache for code segment
10884 @kindex info dcache
10885 @item info dcache @r{[}line@r{]}
10886 Print the information about the performance of data cache of the
10887 current inferior's address space. The information displayed
10888 includes the dcache width and depth, and for each cache line, its
10889 number, address, and how many times it was referenced. This
10890 command is useful for debugging the data cache operation.
10892 If a line number is specified, the contents of that line will be
10895 @item set dcache size @var{size}
10896 @cindex dcache size
10897 @kindex set dcache size
10898 Set maximum number of entries in dcache (dcache depth above).
10900 @item set dcache line-size @var{line-size}
10901 @cindex dcache line-size
10902 @kindex set dcache line-size
10903 Set number of bytes each dcache entry caches (dcache width above).
10904 Must be a power of 2.
10906 @item show dcache size
10907 @kindex show dcache size
10908 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
10910 @item show dcache line-size
10911 @kindex show dcache line-size
10912 Show default size of dcache lines.
10916 @node Searching Memory
10917 @section Search Memory
10918 @cindex searching memory
10920 Memory can be searched for a particular sequence of bytes with the
10921 @code{find} command.
10925 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10926 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10927 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10928 etc. The search begins at address @var{start_addr} and continues for either
10929 @var{len} bytes or through to @var{end_addr} inclusive.
10932 @var{s} and @var{n} are optional parameters.
10933 They may be specified in either order, apart or together.
10936 @item @var{s}, search query size
10937 The size of each search query value.
10943 halfwords (two bytes)
10947 giant words (eight bytes)
10950 All values are interpreted in the current language.
10951 This means, for example, that if the current source language is C/C@t{++}
10952 then searching for the string ``hello'' includes the trailing '\0'.
10954 If the value size is not specified, it is taken from the
10955 value's type in the current language.
10956 This is useful when one wants to specify the search
10957 pattern as a mixture of types.
10958 Note that this means, for example, that in the case of C-like languages
10959 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10960 which is typically four bytes.
10962 @item @var{n}, maximum number of finds
10963 The maximum number of matches to print. The default is to print all finds.
10966 You can use strings as search values. Quote them with double-quotes
10968 The string value is copied into the search pattern byte by byte,
10969 regardless of the endianness of the target and the size specification.
10971 The address of each match found is printed as well as a count of the
10972 number of matches found.
10974 The address of the last value found is stored in convenience variable
10976 A count of the number of matches is stored in @samp{$numfound}.
10978 For example, if stopped at the @code{printf} in this function:
10984 static char hello[] = "hello-hello";
10985 static struct @{ char c; short s; int i; @}
10986 __attribute__ ((packed)) mixed
10987 = @{ 'c', 0x1234, 0x87654321 @};
10988 printf ("%s\n", hello);
10993 you get during debugging:
10996 (gdb) find &hello[0], +sizeof(hello), "hello"
10997 0x804956d <hello.1620+6>
10999 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11000 0x8049567 <hello.1620>
11001 0x804956d <hello.1620+6>
11003 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11004 0x8049567 <hello.1620>
11006 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11007 0x8049560 <mixed.1625>
11009 (gdb) print $numfound
11012 $2 = (void *) 0x8049560
11015 @node Optimized Code
11016 @chapter Debugging Optimized Code
11017 @cindex optimized code, debugging
11018 @cindex debugging optimized code
11020 Almost all compilers support optimization. With optimization
11021 disabled, the compiler generates assembly code that corresponds
11022 directly to your source code, in a simplistic way. As the compiler
11023 applies more powerful optimizations, the generated assembly code
11024 diverges from your original source code. With help from debugging
11025 information generated by the compiler, @value{GDBN} can map from
11026 the running program back to constructs from your original source.
11028 @value{GDBN} is more accurate with optimization disabled. If you
11029 can recompile without optimization, it is easier to follow the
11030 progress of your program during debugging. But, there are many cases
11031 where you may need to debug an optimized version.
11033 When you debug a program compiled with @samp{-g -O}, remember that the
11034 optimizer has rearranged your code; the debugger shows you what is
11035 really there. Do not be too surprised when the execution path does not
11036 exactly match your source file! An extreme example: if you define a
11037 variable, but never use it, @value{GDBN} never sees that
11038 variable---because the compiler optimizes it out of existence.
11040 Some things do not work as well with @samp{-g -O} as with just
11041 @samp{-g}, particularly on machines with instruction scheduling. If in
11042 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11043 please report it to us as a bug (including a test case!).
11044 @xref{Variables}, for more information about debugging optimized code.
11047 * Inline Functions:: How @value{GDBN} presents inlining
11048 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11051 @node Inline Functions
11052 @section Inline Functions
11053 @cindex inline functions, debugging
11055 @dfn{Inlining} is an optimization that inserts a copy of the function
11056 body directly at each call site, instead of jumping to a shared
11057 routine. @value{GDBN} displays inlined functions just like
11058 non-inlined functions. They appear in backtraces. You can view their
11059 arguments and local variables, step into them with @code{step}, skip
11060 them with @code{next}, and escape from them with @code{finish}.
11061 You can check whether a function was inlined by using the
11062 @code{info frame} command.
11064 For @value{GDBN} to support inlined functions, the compiler must
11065 record information about inlining in the debug information ---
11066 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11067 other compilers do also. @value{GDBN} only supports inlined functions
11068 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11069 do not emit two required attributes (@samp{DW_AT_call_file} and
11070 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11071 function calls with earlier versions of @value{NGCC}. It instead
11072 displays the arguments and local variables of inlined functions as
11073 local variables in the caller.
11075 The body of an inlined function is directly included at its call site;
11076 unlike a non-inlined function, there are no instructions devoted to
11077 the call. @value{GDBN} still pretends that the call site and the
11078 start of the inlined function are different instructions. Stepping to
11079 the call site shows the call site, and then stepping again shows
11080 the first line of the inlined function, even though no additional
11081 instructions are executed.
11083 This makes source-level debugging much clearer; you can see both the
11084 context of the call and then the effect of the call. Only stepping by
11085 a single instruction using @code{stepi} or @code{nexti} does not do
11086 this; single instruction steps always show the inlined body.
11088 There are some ways that @value{GDBN} does not pretend that inlined
11089 function calls are the same as normal calls:
11093 Setting breakpoints at the call site of an inlined function may not
11094 work, because the call site does not contain any code. @value{GDBN}
11095 may incorrectly move the breakpoint to the next line of the enclosing
11096 function, after the call. This limitation will be removed in a future
11097 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11098 or inside the inlined function instead.
11101 @value{GDBN} cannot locate the return value of inlined calls after
11102 using the @code{finish} command. This is a limitation of compiler-generated
11103 debugging information; after @code{finish}, you can step to the next line
11104 and print a variable where your program stored the return value.
11108 @node Tail Call Frames
11109 @section Tail Call Frames
11110 @cindex tail call frames, debugging
11112 Function @code{B} can call function @code{C} in its very last statement. In
11113 unoptimized compilation the call of @code{C} is immediately followed by return
11114 instruction at the end of @code{B} code. Optimizing compiler may replace the
11115 call and return in function @code{B} into one jump to function @code{C}
11116 instead. Such use of a jump instruction is called @dfn{tail call}.
11118 During execution of function @code{C}, there will be no indication in the
11119 function call stack frames that it was tail-called from @code{B}. If function
11120 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11121 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11122 some cases @value{GDBN} can determine that @code{C} was tail-called from
11123 @code{B}, and it will then create fictitious call frame for that, with the
11124 return address set up as if @code{B} called @code{C} normally.
11126 This functionality is currently supported only by DWARF 2 debugging format and
11127 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11128 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11131 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11132 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11136 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11138 Stack level 1, frame at 0x7fffffffda30:
11139 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11140 tail call frame, caller of frame at 0x7fffffffda30
11141 source language c++.
11142 Arglist at unknown address.
11143 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11146 The detection of all the possible code path executions can find them ambiguous.
11147 There is no execution history stored (possible @ref{Reverse Execution} is never
11148 used for this purpose) and the last known caller could have reached the known
11149 callee by multiple different jump sequences. In such case @value{GDBN} still
11150 tries to show at least all the unambiguous top tail callers and all the
11151 unambiguous bottom tail calees, if any.
11154 @anchor{set debug entry-values}
11155 @item set debug entry-values
11156 @kindex set debug entry-values
11157 When set to on, enables printing of analysis messages for both frame argument
11158 values at function entry and tail calls. It will show all the possible valid
11159 tail calls code paths it has considered. It will also print the intersection
11160 of them with the final unambiguous (possibly partial or even empty) code path
11163 @item show debug entry-values
11164 @kindex show debug entry-values
11165 Show the current state of analysis messages printing for both frame argument
11166 values at function entry and tail calls.
11169 The analysis messages for tail calls can for example show why the virtual tail
11170 call frame for function @code{c} has not been recognized (due to the indirect
11171 reference by variable @code{x}):
11174 static void __attribute__((noinline, noclone)) c (void);
11175 void (*x) (void) = c;
11176 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11177 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11178 int main (void) @{ x (); return 0; @}
11180 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11181 DW_TAG_GNU_call_site 0x40039a in main
11183 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11186 #1 0x000000000040039a in main () at t.c:5
11189 Another possibility is an ambiguous virtual tail call frames resolution:
11193 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11194 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11195 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11196 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11197 static void __attribute__((noinline, noclone)) b (void)
11198 @{ if (i) c (); else e (); @}
11199 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11200 int main (void) @{ a (); return 0; @}
11202 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11203 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11204 tailcall: reduced: 0x4004d2(a) |
11207 #1 0x00000000004004d2 in a () at t.c:8
11208 #2 0x0000000000400395 in main () at t.c:9
11211 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11212 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11214 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11215 @ifset HAVE_MAKEINFO_CLICK
11216 @set ARROW @click{}
11217 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11218 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11220 @ifclear HAVE_MAKEINFO_CLICK
11222 @set CALLSEQ1B @value{CALLSEQ1A}
11223 @set CALLSEQ2B @value{CALLSEQ2A}
11226 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11227 The code can have possible execution paths @value{CALLSEQ1B} or
11228 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11230 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11231 has found. It then finds another possible calling sequcen - that one is
11232 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11233 printed as the @code{reduced:} calling sequence. That one could have many
11234 futher @code{compare:} and @code{reduced:} statements as long as there remain
11235 any non-ambiguous sequence entries.
11237 For the frame of function @code{b} in both cases there are different possible
11238 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11239 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11240 therefore this one is displayed to the user while the ambiguous frames are
11243 There can be also reasons why printing of frame argument values at function
11248 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11249 static void __attribute__((noinline, noclone)) a (int i);
11250 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11251 static void __attribute__((noinline, noclone)) a (int i)
11252 @{ if (i) b (i - 1); else c (0); @}
11253 int main (void) @{ a (5); return 0; @}
11256 #0 c (i=i@@entry=0) at t.c:2
11257 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11258 function "a" at 0x400420 can call itself via tail calls
11259 i=<optimized out>) at t.c:6
11260 #2 0x000000000040036e in main () at t.c:7
11263 @value{GDBN} cannot find out from the inferior state if and how many times did
11264 function @code{a} call itself (via function @code{b}) as these calls would be
11265 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11266 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11267 prints @code{<optimized out>} instead.
11270 @chapter C Preprocessor Macros
11272 Some languages, such as C and C@t{++}, provide a way to define and invoke
11273 ``preprocessor macros'' which expand into strings of tokens.
11274 @value{GDBN} can evaluate expressions containing macro invocations, show
11275 the result of macro expansion, and show a macro's definition, including
11276 where it was defined.
11278 You may need to compile your program specially to provide @value{GDBN}
11279 with information about preprocessor macros. Most compilers do not
11280 include macros in their debugging information, even when you compile
11281 with the @option{-g} flag. @xref{Compilation}.
11283 A program may define a macro at one point, remove that definition later,
11284 and then provide a different definition after that. Thus, at different
11285 points in the program, a macro may have different definitions, or have
11286 no definition at all. If there is a current stack frame, @value{GDBN}
11287 uses the macros in scope at that frame's source code line. Otherwise,
11288 @value{GDBN} uses the macros in scope at the current listing location;
11291 Whenever @value{GDBN} evaluates an expression, it always expands any
11292 macro invocations present in the expression. @value{GDBN} also provides
11293 the following commands for working with macros explicitly.
11297 @kindex macro expand
11298 @cindex macro expansion, showing the results of preprocessor
11299 @cindex preprocessor macro expansion, showing the results of
11300 @cindex expanding preprocessor macros
11301 @item macro expand @var{expression}
11302 @itemx macro exp @var{expression}
11303 Show the results of expanding all preprocessor macro invocations in
11304 @var{expression}. Since @value{GDBN} simply expands macros, but does
11305 not parse the result, @var{expression} need not be a valid expression;
11306 it can be any string of tokens.
11309 @item macro expand-once @var{expression}
11310 @itemx macro exp1 @var{expression}
11311 @cindex expand macro once
11312 @i{(This command is not yet implemented.)} Show the results of
11313 expanding those preprocessor macro invocations that appear explicitly in
11314 @var{expression}. Macro invocations appearing in that expansion are
11315 left unchanged. This command allows you to see the effect of a
11316 particular macro more clearly, without being confused by further
11317 expansions. Since @value{GDBN} simply expands macros, but does not
11318 parse the result, @var{expression} need not be a valid expression; it
11319 can be any string of tokens.
11322 @cindex macro definition, showing
11323 @cindex definition of a macro, showing
11324 @cindex macros, from debug info
11325 @item info macro [-a|-all] [--] @var{macro}
11326 Show the current definition or all definitions of the named @var{macro},
11327 and describe the source location or compiler command-line where that
11328 definition was established. The optional double dash is to signify the end of
11329 argument processing and the beginning of @var{macro} for non C-like macros where
11330 the macro may begin with a hyphen.
11332 @kindex info macros
11333 @item info macros @var{linespec}
11334 Show all macro definitions that are in effect at the location specified
11335 by @var{linespec}, and describe the source location or compiler
11336 command-line where those definitions were established.
11338 @kindex macro define
11339 @cindex user-defined macros
11340 @cindex defining macros interactively
11341 @cindex macros, user-defined
11342 @item macro define @var{macro} @var{replacement-list}
11343 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11344 Introduce a definition for a preprocessor macro named @var{macro},
11345 invocations of which are replaced by the tokens given in
11346 @var{replacement-list}. The first form of this command defines an
11347 ``object-like'' macro, which takes no arguments; the second form
11348 defines a ``function-like'' macro, which takes the arguments given in
11351 A definition introduced by this command is in scope in every
11352 expression evaluated in @value{GDBN}, until it is removed with the
11353 @code{macro undef} command, described below. The definition overrides
11354 all definitions for @var{macro} present in the program being debugged,
11355 as well as any previous user-supplied definition.
11357 @kindex macro undef
11358 @item macro undef @var{macro}
11359 Remove any user-supplied definition for the macro named @var{macro}.
11360 This command only affects definitions provided with the @code{macro
11361 define} command, described above; it cannot remove definitions present
11362 in the program being debugged.
11366 List all the macros defined using the @code{macro define} command.
11369 @cindex macros, example of debugging with
11370 Here is a transcript showing the above commands in action. First, we
11371 show our source files:
11376 #include "sample.h"
11379 #define ADD(x) (M + x)
11384 printf ("Hello, world!\n");
11386 printf ("We're so creative.\n");
11388 printf ("Goodbye, world!\n");
11395 Now, we compile the program using the @sc{gnu} C compiler,
11396 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11397 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11398 and @option{-gdwarf-4}; we recommend always choosing the most recent
11399 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11400 includes information about preprocessor macros in the debugging
11404 $ gcc -gdwarf-2 -g3 sample.c -o sample
11408 Now, we start @value{GDBN} on our sample program:
11412 GNU gdb 2002-05-06-cvs
11413 Copyright 2002 Free Software Foundation, Inc.
11414 GDB is free software, @dots{}
11418 We can expand macros and examine their definitions, even when the
11419 program is not running. @value{GDBN} uses the current listing position
11420 to decide which macro definitions are in scope:
11423 (@value{GDBP}) list main
11426 5 #define ADD(x) (M + x)
11431 10 printf ("Hello, world!\n");
11433 12 printf ("We're so creative.\n");
11434 (@value{GDBP}) info macro ADD
11435 Defined at /home/jimb/gdb/macros/play/sample.c:5
11436 #define ADD(x) (M + x)
11437 (@value{GDBP}) info macro Q
11438 Defined at /home/jimb/gdb/macros/play/sample.h:1
11439 included at /home/jimb/gdb/macros/play/sample.c:2
11441 (@value{GDBP}) macro expand ADD(1)
11442 expands to: (42 + 1)
11443 (@value{GDBP}) macro expand-once ADD(1)
11444 expands to: once (M + 1)
11448 In the example above, note that @code{macro expand-once} expands only
11449 the macro invocation explicit in the original text --- the invocation of
11450 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11451 which was introduced by @code{ADD}.
11453 Once the program is running, @value{GDBN} uses the macro definitions in
11454 force at the source line of the current stack frame:
11457 (@value{GDBP}) break main
11458 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11460 Starting program: /home/jimb/gdb/macros/play/sample
11462 Breakpoint 1, main () at sample.c:10
11463 10 printf ("Hello, world!\n");
11467 At line 10, the definition of the macro @code{N} at line 9 is in force:
11470 (@value{GDBP}) info macro N
11471 Defined at /home/jimb/gdb/macros/play/sample.c:9
11473 (@value{GDBP}) macro expand N Q M
11474 expands to: 28 < 42
11475 (@value{GDBP}) print N Q M
11480 As we step over directives that remove @code{N}'s definition, and then
11481 give it a new definition, @value{GDBN} finds the definition (or lack
11482 thereof) in force at each point:
11485 (@value{GDBP}) next
11487 12 printf ("We're so creative.\n");
11488 (@value{GDBP}) info macro N
11489 The symbol `N' has no definition as a C/C++ preprocessor macro
11490 at /home/jimb/gdb/macros/play/sample.c:12
11491 (@value{GDBP}) next
11493 14 printf ("Goodbye, world!\n");
11494 (@value{GDBP}) info macro N
11495 Defined at /home/jimb/gdb/macros/play/sample.c:13
11497 (@value{GDBP}) macro expand N Q M
11498 expands to: 1729 < 42
11499 (@value{GDBP}) print N Q M
11504 In addition to source files, macros can be defined on the compilation command
11505 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11506 such a way, @value{GDBN} displays the location of their definition as line zero
11507 of the source file submitted to the compiler.
11510 (@value{GDBP}) info macro __STDC__
11511 Defined at /home/jimb/gdb/macros/play/sample.c:0
11518 @chapter Tracepoints
11519 @c This chapter is based on the documentation written by Michael
11520 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11522 @cindex tracepoints
11523 In some applications, it is not feasible for the debugger to interrupt
11524 the program's execution long enough for the developer to learn
11525 anything helpful about its behavior. If the program's correctness
11526 depends on its real-time behavior, delays introduced by a debugger
11527 might cause the program to change its behavior drastically, or perhaps
11528 fail, even when the code itself is correct. It is useful to be able
11529 to observe the program's behavior without interrupting it.
11531 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11532 specify locations in the program, called @dfn{tracepoints}, and
11533 arbitrary expressions to evaluate when those tracepoints are reached.
11534 Later, using the @code{tfind} command, you can examine the values
11535 those expressions had when the program hit the tracepoints. The
11536 expressions may also denote objects in memory---structures or arrays,
11537 for example---whose values @value{GDBN} should record; while visiting
11538 a particular tracepoint, you may inspect those objects as if they were
11539 in memory at that moment. However, because @value{GDBN} records these
11540 values without interacting with you, it can do so quickly and
11541 unobtrusively, hopefully not disturbing the program's behavior.
11543 The tracepoint facility is currently available only for remote
11544 targets. @xref{Targets}. In addition, your remote target must know
11545 how to collect trace data. This functionality is implemented in the
11546 remote stub; however, none of the stubs distributed with @value{GDBN}
11547 support tracepoints as of this writing. The format of the remote
11548 packets used to implement tracepoints are described in @ref{Tracepoint
11551 It is also possible to get trace data from a file, in a manner reminiscent
11552 of corefiles; you specify the filename, and use @code{tfind} to search
11553 through the file. @xref{Trace Files}, for more details.
11555 This chapter describes the tracepoint commands and features.
11558 * Set Tracepoints::
11559 * Analyze Collected Data::
11560 * Tracepoint Variables::
11564 @node Set Tracepoints
11565 @section Commands to Set Tracepoints
11567 Before running such a @dfn{trace experiment}, an arbitrary number of
11568 tracepoints can be set. A tracepoint is actually a special type of
11569 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11570 standard breakpoint commands. For instance, as with breakpoints,
11571 tracepoint numbers are successive integers starting from one, and many
11572 of the commands associated with tracepoints take the tracepoint number
11573 as their argument, to identify which tracepoint to work on.
11575 For each tracepoint, you can specify, in advance, some arbitrary set
11576 of data that you want the target to collect in the trace buffer when
11577 it hits that tracepoint. The collected data can include registers,
11578 local variables, or global data. Later, you can use @value{GDBN}
11579 commands to examine the values these data had at the time the
11580 tracepoint was hit.
11582 Tracepoints do not support every breakpoint feature. Ignore counts on
11583 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11584 commands when they are hit. Tracepoints may not be thread-specific
11587 @cindex fast tracepoints
11588 Some targets may support @dfn{fast tracepoints}, which are inserted in
11589 a different way (such as with a jump instead of a trap), that is
11590 faster but possibly restricted in where they may be installed.
11592 @cindex static tracepoints
11593 @cindex markers, static tracepoints
11594 @cindex probing markers, static tracepoints
11595 Regular and fast tracepoints are dynamic tracing facilities, meaning
11596 that they can be used to insert tracepoints at (almost) any location
11597 in the target. Some targets may also support controlling @dfn{static
11598 tracepoints} from @value{GDBN}. With static tracing, a set of
11599 instrumentation points, also known as @dfn{markers}, are embedded in
11600 the target program, and can be activated or deactivated by name or
11601 address. These are usually placed at locations which facilitate
11602 investigating what the target is actually doing. @value{GDBN}'s
11603 support for static tracing includes being able to list instrumentation
11604 points, and attach them with @value{GDBN} defined high level
11605 tracepoints that expose the whole range of convenience of
11606 @value{GDBN}'s tracepoints support. Namely, support for collecting
11607 registers values and values of global or local (to the instrumentation
11608 point) variables; tracepoint conditions and trace state variables.
11609 The act of installing a @value{GDBN} static tracepoint on an
11610 instrumentation point, or marker, is referred to as @dfn{probing} a
11611 static tracepoint marker.
11613 @code{gdbserver} supports tracepoints on some target systems.
11614 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11616 This section describes commands to set tracepoints and associated
11617 conditions and actions.
11620 * Create and Delete Tracepoints::
11621 * Enable and Disable Tracepoints::
11622 * Tracepoint Passcounts::
11623 * Tracepoint Conditions::
11624 * Trace State Variables::
11625 * Tracepoint Actions::
11626 * Listing Tracepoints::
11627 * Listing Static Tracepoint Markers::
11628 * Starting and Stopping Trace Experiments::
11629 * Tracepoint Restrictions::
11632 @node Create and Delete Tracepoints
11633 @subsection Create and Delete Tracepoints
11636 @cindex set tracepoint
11638 @item trace @var{location}
11639 The @code{trace} command is very similar to the @code{break} command.
11640 Its argument @var{location} can be a source line, a function name, or
11641 an address in the target program. @xref{Specify Location}. The
11642 @code{trace} command defines a tracepoint, which is a point in the
11643 target program where the debugger will briefly stop, collect some
11644 data, and then allow the program to continue. Setting a tracepoint or
11645 changing its actions takes effect immediately if the remote stub
11646 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11648 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11649 these changes don't take effect until the next @code{tstart}
11650 command, and once a trace experiment is running, further changes will
11651 not have any effect until the next trace experiment starts. In addition,
11652 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11653 address is not yet resolved. (This is similar to pending breakpoints.)
11654 Pending tracepoints are not downloaded to the target and not installed
11655 until they are resolved. The resolution of pending tracepoints requires
11656 @value{GDBN} support---when debugging with the remote target, and
11657 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11658 tracing}), pending tracepoints can not be resolved (and downloaded to
11659 the remote stub) while @value{GDBN} is disconnected.
11661 Here are some examples of using the @code{trace} command:
11664 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11666 (@value{GDBP}) @b{trace +2} // 2 lines forward
11668 (@value{GDBP}) @b{trace my_function} // first source line of function
11670 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11672 (@value{GDBP}) @b{trace *0x2117c4} // an address
11676 You can abbreviate @code{trace} as @code{tr}.
11678 @item trace @var{location} if @var{cond}
11679 Set a tracepoint with condition @var{cond}; evaluate the expression
11680 @var{cond} each time the tracepoint is reached, and collect data only
11681 if the value is nonzero---that is, if @var{cond} evaluates as true.
11682 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11683 information on tracepoint conditions.
11685 @item ftrace @var{location} [ if @var{cond} ]
11686 @cindex set fast tracepoint
11687 @cindex fast tracepoints, setting
11689 The @code{ftrace} command sets a fast tracepoint. For targets that
11690 support them, fast tracepoints will use a more efficient but possibly
11691 less general technique to trigger data collection, such as a jump
11692 instruction instead of a trap, or some sort of hardware support. It
11693 may not be possible to create a fast tracepoint at the desired
11694 location, in which case the command will exit with an explanatory
11697 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11700 On 32-bit x86-architecture systems, fast tracepoints normally need to
11701 be placed at an instruction that is 5 bytes or longer, but can be
11702 placed at 4-byte instructions if the low 64K of memory of the target
11703 program is available to install trampolines. Some Unix-type systems,
11704 such as @sc{gnu}/Linux, exclude low addresses from the program's
11705 address space; but for instance with the Linux kernel it is possible
11706 to let @value{GDBN} use this area by doing a @command{sysctl} command
11707 to set the @code{mmap_min_addr} kernel parameter, as in
11710 sudo sysctl -w vm.mmap_min_addr=32768
11714 which sets the low address to 32K, which leaves plenty of room for
11715 trampolines. The minimum address should be set to a page boundary.
11717 @item strace @var{location} [ if @var{cond} ]
11718 @cindex set static tracepoint
11719 @cindex static tracepoints, setting
11720 @cindex probe static tracepoint marker
11722 The @code{strace} command sets a static tracepoint. For targets that
11723 support it, setting a static tracepoint probes a static
11724 instrumentation point, or marker, found at @var{location}. It may not
11725 be possible to set a static tracepoint at the desired location, in
11726 which case the command will exit with an explanatory message.
11728 @value{GDBN} handles arguments to @code{strace} exactly as for
11729 @code{trace}, with the addition that the user can also specify
11730 @code{-m @var{marker}} as @var{location}. This probes the marker
11731 identified by the @var{marker} string identifier. This identifier
11732 depends on the static tracepoint backend library your program is
11733 using. You can find all the marker identifiers in the @samp{ID} field
11734 of the @code{info static-tracepoint-markers} command output.
11735 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11736 Markers}. For example, in the following small program using the UST
11742 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11747 the marker id is composed of joining the first two arguments to the
11748 @code{trace_mark} call with a slash, which translates to:
11751 (@value{GDBP}) info static-tracepoint-markers
11752 Cnt Enb ID Address What
11753 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11759 so you may probe the marker above with:
11762 (@value{GDBP}) strace -m ust/bar33
11765 Static tracepoints accept an extra collect action --- @code{collect
11766 $_sdata}. This collects arbitrary user data passed in the probe point
11767 call to the tracing library. In the UST example above, you'll see
11768 that the third argument to @code{trace_mark} is a printf-like format
11769 string. The user data is then the result of running that formating
11770 string against the following arguments. Note that @code{info
11771 static-tracepoint-markers} command output lists that format string in
11772 the @samp{Data:} field.
11774 You can inspect this data when analyzing the trace buffer, by printing
11775 the $_sdata variable like any other variable available to
11776 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11779 @cindex last tracepoint number
11780 @cindex recent tracepoint number
11781 @cindex tracepoint number
11782 The convenience variable @code{$tpnum} records the tracepoint number
11783 of the most recently set tracepoint.
11785 @kindex delete tracepoint
11786 @cindex tracepoint deletion
11787 @item delete tracepoint @r{[}@var{num}@r{]}
11788 Permanently delete one or more tracepoints. With no argument, the
11789 default is to delete all tracepoints. Note that the regular
11790 @code{delete} command can remove tracepoints also.
11795 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11797 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11801 You can abbreviate this command as @code{del tr}.
11804 @node Enable and Disable Tracepoints
11805 @subsection Enable and Disable Tracepoints
11807 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11810 @kindex disable tracepoint
11811 @item disable tracepoint @r{[}@var{num}@r{]}
11812 Disable tracepoint @var{num}, or all tracepoints if no argument
11813 @var{num} is given. A disabled tracepoint will have no effect during
11814 a trace experiment, but it is not forgotten. You can re-enable
11815 a disabled tracepoint using the @code{enable tracepoint} command.
11816 If the command is issued during a trace experiment and the debug target
11817 has support for disabling tracepoints during a trace experiment, then the
11818 change will be effective immediately. Otherwise, it will be applied to the
11819 next trace experiment.
11821 @kindex enable tracepoint
11822 @item enable tracepoint @r{[}@var{num}@r{]}
11823 Enable tracepoint @var{num}, or all tracepoints. If this command is
11824 issued during a trace experiment and the debug target supports enabling
11825 tracepoints during a trace experiment, then the enabled tracepoints will
11826 become effective immediately. Otherwise, they will become effective the
11827 next time a trace experiment is run.
11830 @node Tracepoint Passcounts
11831 @subsection Tracepoint Passcounts
11835 @cindex tracepoint pass count
11836 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11837 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11838 automatically stop a trace experiment. If a tracepoint's passcount is
11839 @var{n}, then the trace experiment will be automatically stopped on
11840 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11841 @var{num} is not specified, the @code{passcount} command sets the
11842 passcount of the most recently defined tracepoint. If no passcount is
11843 given, the trace experiment will run until stopped explicitly by the
11849 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11850 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11852 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11853 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11854 (@value{GDBP}) @b{trace foo}
11855 (@value{GDBP}) @b{pass 3}
11856 (@value{GDBP}) @b{trace bar}
11857 (@value{GDBP}) @b{pass 2}
11858 (@value{GDBP}) @b{trace baz}
11859 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11860 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11861 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11862 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11866 @node Tracepoint Conditions
11867 @subsection Tracepoint Conditions
11868 @cindex conditional tracepoints
11869 @cindex tracepoint conditions
11871 The simplest sort of tracepoint collects data every time your program
11872 reaches a specified place. You can also specify a @dfn{condition} for
11873 a tracepoint. A condition is just a Boolean expression in your
11874 programming language (@pxref{Expressions, ,Expressions}). A
11875 tracepoint with a condition evaluates the expression each time your
11876 program reaches it, and data collection happens only if the condition
11879 Tracepoint conditions can be specified when a tracepoint is set, by
11880 using @samp{if} in the arguments to the @code{trace} command.
11881 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11882 also be set or changed at any time with the @code{condition} command,
11883 just as with breakpoints.
11885 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11886 the conditional expression itself. Instead, @value{GDBN} encodes the
11887 expression into an agent expression (@pxref{Agent Expressions})
11888 suitable for execution on the target, independently of @value{GDBN}.
11889 Global variables become raw memory locations, locals become stack
11890 accesses, and so forth.
11892 For instance, suppose you have a function that is usually called
11893 frequently, but should not be called after an error has occurred. You
11894 could use the following tracepoint command to collect data about calls
11895 of that function that happen while the error code is propagating
11896 through the program; an unconditional tracepoint could end up
11897 collecting thousands of useless trace frames that you would have to
11901 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11904 @node Trace State Variables
11905 @subsection Trace State Variables
11906 @cindex trace state variables
11908 A @dfn{trace state variable} is a special type of variable that is
11909 created and managed by target-side code. The syntax is the same as
11910 that for GDB's convenience variables (a string prefixed with ``$''),
11911 but they are stored on the target. They must be created explicitly,
11912 using a @code{tvariable} command. They are always 64-bit signed
11915 Trace state variables are remembered by @value{GDBN}, and downloaded
11916 to the target along with tracepoint information when the trace
11917 experiment starts. There are no intrinsic limits on the number of
11918 trace state variables, beyond memory limitations of the target.
11920 @cindex convenience variables, and trace state variables
11921 Although trace state variables are managed by the target, you can use
11922 them in print commands and expressions as if they were convenience
11923 variables; @value{GDBN} will get the current value from the target
11924 while the trace experiment is running. Trace state variables share
11925 the same namespace as other ``$'' variables, which means that you
11926 cannot have trace state variables with names like @code{$23} or
11927 @code{$pc}, nor can you have a trace state variable and a convenience
11928 variable with the same name.
11932 @item tvariable $@var{name} [ = @var{expression} ]
11934 The @code{tvariable} command creates a new trace state variable named
11935 @code{$@var{name}}, and optionally gives it an initial value of
11936 @var{expression}. @var{expression} is evaluated when this command is
11937 entered; the result will be converted to an integer if possible,
11938 otherwise @value{GDBN} will report an error. A subsequent
11939 @code{tvariable} command specifying the same name does not create a
11940 variable, but instead assigns the supplied initial value to the
11941 existing variable of that name, overwriting any previous initial
11942 value. The default initial value is 0.
11944 @item info tvariables
11945 @kindex info tvariables
11946 List all the trace state variables along with their initial values.
11947 Their current values may also be displayed, if the trace experiment is
11950 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11951 @kindex delete tvariable
11952 Delete the given trace state variables, or all of them if no arguments
11957 @node Tracepoint Actions
11958 @subsection Tracepoint Action Lists
11962 @cindex tracepoint actions
11963 @item actions @r{[}@var{num}@r{]}
11964 This command will prompt for a list of actions to be taken when the
11965 tracepoint is hit. If the tracepoint number @var{num} is not
11966 specified, this command sets the actions for the one that was most
11967 recently defined (so that you can define a tracepoint and then say
11968 @code{actions} without bothering about its number). You specify the
11969 actions themselves on the following lines, one action at a time, and
11970 terminate the actions list with a line containing just @code{end}. So
11971 far, the only defined actions are @code{collect}, @code{teval}, and
11972 @code{while-stepping}.
11974 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11975 Commands, ,Breakpoint Command Lists}), except that only the defined
11976 actions are allowed; any other @value{GDBN} command is rejected.
11978 @cindex remove actions from a tracepoint
11979 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11980 and follow it immediately with @samp{end}.
11983 (@value{GDBP}) @b{collect @var{data}} // collect some data
11985 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11987 (@value{GDBP}) @b{end} // signals the end of actions.
11990 In the following example, the action list begins with @code{collect}
11991 commands indicating the things to be collected when the tracepoint is
11992 hit. Then, in order to single-step and collect additional data
11993 following the tracepoint, a @code{while-stepping} command is used,
11994 followed by the list of things to be collected after each step in a
11995 sequence of single steps. The @code{while-stepping} command is
11996 terminated by its own separate @code{end} command. Lastly, the action
11997 list is terminated by an @code{end} command.
12000 (@value{GDBP}) @b{trace foo}
12001 (@value{GDBP}) @b{actions}
12002 Enter actions for tracepoint 1, one per line:
12005 > while-stepping 12
12006 > collect $pc, arr[i]
12011 @kindex collect @r{(tracepoints)}
12012 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12013 Collect values of the given expressions when the tracepoint is hit.
12014 This command accepts a comma-separated list of any valid expressions.
12015 In addition to global, static, or local variables, the following
12016 special arguments are supported:
12020 Collect all registers.
12023 Collect all function arguments.
12026 Collect all local variables.
12029 Collect the return address. This is helpful if you want to see more
12033 Collects the number of arguments from the static probe at which the
12034 tracepoint is located.
12035 @xref{Static Probe Points}.
12037 @item $_probe_arg@var{n}
12038 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12039 from the static probe at which the tracepoint is located.
12040 @xref{Static Probe Points}.
12043 @vindex $_sdata@r{, collect}
12044 Collect static tracepoint marker specific data. Only available for
12045 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12046 Lists}. On the UST static tracepoints library backend, an
12047 instrumentation point resembles a @code{printf} function call. The
12048 tracing library is able to collect user specified data formatted to a
12049 character string using the format provided by the programmer that
12050 instrumented the program. Other backends have similar mechanisms.
12051 Here's an example of a UST marker call:
12054 const char master_name[] = "$your_name";
12055 trace_mark(channel1, marker1, "hello %s", master_name)
12058 In this case, collecting @code{$_sdata} collects the string
12059 @samp{hello $yourname}. When analyzing the trace buffer, you can
12060 inspect @samp{$_sdata} like any other variable available to
12064 You can give several consecutive @code{collect} commands, each one
12065 with a single argument, or one @code{collect} command with several
12066 arguments separated by commas; the effect is the same.
12068 The optional @var{mods} changes the usual handling of the arguments.
12069 @code{s} requests that pointers to chars be handled as strings, in
12070 particular collecting the contents of the memory being pointed at, up
12071 to the first zero. The upper bound is by default the value of the
12072 @code{print elements} variable; if @code{s} is followed by a decimal
12073 number, that is the upper bound instead. So for instance
12074 @samp{collect/s25 mystr} collects as many as 25 characters at
12077 The command @code{info scope} (@pxref{Symbols, info scope}) is
12078 particularly useful for figuring out what data to collect.
12080 @kindex teval @r{(tracepoints)}
12081 @item teval @var{expr1}, @var{expr2}, @dots{}
12082 Evaluate the given expressions when the tracepoint is hit. This
12083 command accepts a comma-separated list of expressions. The results
12084 are discarded, so this is mainly useful for assigning values to trace
12085 state variables (@pxref{Trace State Variables}) without adding those
12086 values to the trace buffer, as would be the case if the @code{collect}
12089 @kindex while-stepping @r{(tracepoints)}
12090 @item while-stepping @var{n}
12091 Perform @var{n} single-step instruction traces after the tracepoint,
12092 collecting new data after each step. The @code{while-stepping}
12093 command is followed by the list of what to collect while stepping
12094 (followed by its own @code{end} command):
12097 > while-stepping 12
12098 > collect $regs, myglobal
12104 Note that @code{$pc} is not automatically collected by
12105 @code{while-stepping}; you need to explicitly collect that register if
12106 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12109 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12110 @kindex set default-collect
12111 @cindex default collection action
12112 This variable is a list of expressions to collect at each tracepoint
12113 hit. It is effectively an additional @code{collect} action prepended
12114 to every tracepoint action list. The expressions are parsed
12115 individually for each tracepoint, so for instance a variable named
12116 @code{xyz} may be interpreted as a global for one tracepoint, and a
12117 local for another, as appropriate to the tracepoint's location.
12119 @item show default-collect
12120 @kindex show default-collect
12121 Show the list of expressions that are collected by default at each
12126 @node Listing Tracepoints
12127 @subsection Listing Tracepoints
12130 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12131 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12132 @cindex information about tracepoints
12133 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12134 Display information about the tracepoint @var{num}. If you don't
12135 specify a tracepoint number, displays information about all the
12136 tracepoints defined so far. The format is similar to that used for
12137 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12138 command, simply restricting itself to tracepoints.
12140 A tracepoint's listing may include additional information specific to
12145 its passcount as given by the @code{passcount @var{n}} command
12148 the state about installed on target of each location
12152 (@value{GDBP}) @b{info trace}
12153 Num Type Disp Enb Address What
12154 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12156 collect globfoo, $regs
12161 2 tracepoint keep y <MULTIPLE>
12163 2.1 y 0x0804859c in func4 at change-loc.h:35
12164 installed on target
12165 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12166 installed on target
12167 2.3 y <PENDING> set_tracepoint
12168 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12169 not installed on target
12174 This command can be abbreviated @code{info tp}.
12177 @node Listing Static Tracepoint Markers
12178 @subsection Listing Static Tracepoint Markers
12181 @kindex info static-tracepoint-markers
12182 @cindex information about static tracepoint markers
12183 @item info static-tracepoint-markers
12184 Display information about all static tracepoint markers defined in the
12187 For each marker, the following columns are printed:
12191 An incrementing counter, output to help readability. This is not a
12194 The marker ID, as reported by the target.
12195 @item Enabled or Disabled
12196 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12197 that are not enabled.
12199 Where the marker is in your program, as a memory address.
12201 Where the marker is in the source for your program, as a file and line
12202 number. If the debug information included in the program does not
12203 allow @value{GDBN} to locate the source of the marker, this column
12204 will be left blank.
12208 In addition, the following information may be printed for each marker:
12212 User data passed to the tracing library by the marker call. In the
12213 UST backend, this is the format string passed as argument to the
12215 @item Static tracepoints probing the marker
12216 The list of static tracepoints attached to the marker.
12220 (@value{GDBP}) info static-tracepoint-markers
12221 Cnt ID Enb Address What
12222 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12223 Data: number1 %d number2 %d
12224 Probed by static tracepoints: #2
12225 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12231 @node Starting and Stopping Trace Experiments
12232 @subsection Starting and Stopping Trace Experiments
12235 @kindex tstart [ @var{notes} ]
12236 @cindex start a new trace experiment
12237 @cindex collected data discarded
12239 This command starts the trace experiment, and begins collecting data.
12240 It has the side effect of discarding all the data collected in the
12241 trace buffer during the previous trace experiment. If any arguments
12242 are supplied, they are taken as a note and stored with the trace
12243 experiment's state. The notes may be arbitrary text, and are
12244 especially useful with disconnected tracing in a multi-user context;
12245 the notes can explain what the trace is doing, supply user contact
12246 information, and so forth.
12248 @kindex tstop [ @var{notes} ]
12249 @cindex stop a running trace experiment
12251 This command stops the trace experiment. If any arguments are
12252 supplied, they are recorded with the experiment as a note. This is
12253 useful if you are stopping a trace started by someone else, for
12254 instance if the trace is interfering with the system's behavior and
12255 needs to be stopped quickly.
12257 @strong{Note}: a trace experiment and data collection may stop
12258 automatically if any tracepoint's passcount is reached
12259 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12262 @cindex status of trace data collection
12263 @cindex trace experiment, status of
12265 This command displays the status of the current trace data
12269 Here is an example of the commands we described so far:
12272 (@value{GDBP}) @b{trace gdb_c_test}
12273 (@value{GDBP}) @b{actions}
12274 Enter actions for tracepoint #1, one per line.
12275 > collect $regs,$locals,$args
12276 > while-stepping 11
12280 (@value{GDBP}) @b{tstart}
12281 [time passes @dots{}]
12282 (@value{GDBP}) @b{tstop}
12285 @anchor{disconnected tracing}
12286 @cindex disconnected tracing
12287 You can choose to continue running the trace experiment even if
12288 @value{GDBN} disconnects from the target, voluntarily or
12289 involuntarily. For commands such as @code{detach}, the debugger will
12290 ask what you want to do with the trace. But for unexpected
12291 terminations (@value{GDBN} crash, network outage), it would be
12292 unfortunate to lose hard-won trace data, so the variable
12293 @code{disconnected-tracing} lets you decide whether the trace should
12294 continue running without @value{GDBN}.
12297 @item set disconnected-tracing on
12298 @itemx set disconnected-tracing off
12299 @kindex set disconnected-tracing
12300 Choose whether a tracing run should continue to run if @value{GDBN}
12301 has disconnected from the target. Note that @code{detach} or
12302 @code{quit} will ask you directly what to do about a running trace no
12303 matter what this variable's setting, so the variable is mainly useful
12304 for handling unexpected situations, such as loss of the network.
12306 @item show disconnected-tracing
12307 @kindex show disconnected-tracing
12308 Show the current choice for disconnected tracing.
12312 When you reconnect to the target, the trace experiment may or may not
12313 still be running; it might have filled the trace buffer in the
12314 meantime, or stopped for one of the other reasons. If it is running,
12315 it will continue after reconnection.
12317 Upon reconnection, the target will upload information about the
12318 tracepoints in effect. @value{GDBN} will then compare that
12319 information to the set of tracepoints currently defined, and attempt
12320 to match them up, allowing for the possibility that the numbers may
12321 have changed due to creation and deletion in the meantime. If one of
12322 the target's tracepoints does not match any in @value{GDBN}, the
12323 debugger will create a new tracepoint, so that you have a number with
12324 which to specify that tracepoint. This matching-up process is
12325 necessarily heuristic, and it may result in useless tracepoints being
12326 created; you may simply delete them if they are of no use.
12328 @cindex circular trace buffer
12329 If your target agent supports a @dfn{circular trace buffer}, then you
12330 can run a trace experiment indefinitely without filling the trace
12331 buffer; when space runs out, the agent deletes already-collected trace
12332 frames, oldest first, until there is enough room to continue
12333 collecting. This is especially useful if your tracepoints are being
12334 hit too often, and your trace gets terminated prematurely because the
12335 buffer is full. To ask for a circular trace buffer, simply set
12336 @samp{circular-trace-buffer} to on. You can set this at any time,
12337 including during tracing; if the agent can do it, it will change
12338 buffer handling on the fly, otherwise it will not take effect until
12342 @item set circular-trace-buffer on
12343 @itemx set circular-trace-buffer off
12344 @kindex set circular-trace-buffer
12345 Choose whether a tracing run should use a linear or circular buffer
12346 for trace data. A linear buffer will not lose any trace data, but may
12347 fill up prematurely, while a circular buffer will discard old trace
12348 data, but it will have always room for the latest tracepoint hits.
12350 @item show circular-trace-buffer
12351 @kindex show circular-trace-buffer
12352 Show the current choice for the trace buffer. Note that this may not
12353 match the agent's current buffer handling, nor is it guaranteed to
12354 match the setting that might have been in effect during a past run,
12355 for instance if you are looking at frames from a trace file.
12360 @item set trace-buffer-size @var{n}
12361 @itemx set trace-buffer-size unlimited
12362 @kindex set trace-buffer-size
12363 Request that the target use a trace buffer of @var{n} bytes. Not all
12364 targets will honor the request; they may have a compiled-in size for
12365 the trace buffer, or some other limitation. Set to a value of
12366 @code{unlimited} or @code{-1} to let the target use whatever size it
12367 likes. This is also the default.
12369 @item show trace-buffer-size
12370 @kindex show trace-buffer-size
12371 Show the current requested size for the trace buffer. Note that this
12372 will only match the actual size if the target supports size-setting,
12373 and was able to handle the requested size. For instance, if the
12374 target can only change buffer size between runs, this variable will
12375 not reflect the change until the next run starts. Use @code{tstatus}
12376 to get a report of the actual buffer size.
12380 @item set trace-user @var{text}
12381 @kindex set trace-user
12383 @item show trace-user
12384 @kindex show trace-user
12386 @item set trace-notes @var{text}
12387 @kindex set trace-notes
12388 Set the trace run's notes.
12390 @item show trace-notes
12391 @kindex show trace-notes
12392 Show the trace run's notes.
12394 @item set trace-stop-notes @var{text}
12395 @kindex set trace-stop-notes
12396 Set the trace run's stop notes. The handling of the note is as for
12397 @code{tstop} arguments; the set command is convenient way to fix a
12398 stop note that is mistaken or incomplete.
12400 @item show trace-stop-notes
12401 @kindex show trace-stop-notes
12402 Show the trace run's stop notes.
12406 @node Tracepoint Restrictions
12407 @subsection Tracepoint Restrictions
12409 @cindex tracepoint restrictions
12410 There are a number of restrictions on the use of tracepoints. As
12411 described above, tracepoint data gathering occurs on the target
12412 without interaction from @value{GDBN}. Thus the full capabilities of
12413 the debugger are not available during data gathering, and then at data
12414 examination time, you will be limited by only having what was
12415 collected. The following items describe some common problems, but it
12416 is not exhaustive, and you may run into additional difficulties not
12422 Tracepoint expressions are intended to gather objects (lvalues). Thus
12423 the full flexibility of GDB's expression evaluator is not available.
12424 You cannot call functions, cast objects to aggregate types, access
12425 convenience variables or modify values (except by assignment to trace
12426 state variables). Some language features may implicitly call
12427 functions (for instance Objective-C fields with accessors), and therefore
12428 cannot be collected either.
12431 Collection of local variables, either individually or in bulk with
12432 @code{$locals} or @code{$args}, during @code{while-stepping} may
12433 behave erratically. The stepping action may enter a new scope (for
12434 instance by stepping into a function), or the location of the variable
12435 may change (for instance it is loaded into a register). The
12436 tracepoint data recorded uses the location information for the
12437 variables that is correct for the tracepoint location. When the
12438 tracepoint is created, it is not possible, in general, to determine
12439 where the steps of a @code{while-stepping} sequence will advance the
12440 program---particularly if a conditional branch is stepped.
12443 Collection of an incompletely-initialized or partially-destroyed object
12444 may result in something that @value{GDBN} cannot display, or displays
12445 in a misleading way.
12448 When @value{GDBN} displays a pointer to character it automatically
12449 dereferences the pointer to also display characters of the string
12450 being pointed to. However, collecting the pointer during tracing does
12451 not automatically collect the string. You need to explicitly
12452 dereference the pointer and provide size information if you want to
12453 collect not only the pointer, but the memory pointed to. For example,
12454 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12458 It is not possible to collect a complete stack backtrace at a
12459 tracepoint. Instead, you may collect the registers and a few hundred
12460 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12461 (adjust to use the name of the actual stack pointer register on your
12462 target architecture, and the amount of stack you wish to capture).
12463 Then the @code{backtrace} command will show a partial backtrace when
12464 using a trace frame. The number of stack frames that can be examined
12465 depends on the sizes of the frames in the collected stack. Note that
12466 if you ask for a block so large that it goes past the bottom of the
12467 stack, the target agent may report an error trying to read from an
12471 If you do not collect registers at a tracepoint, @value{GDBN} can
12472 infer that the value of @code{$pc} must be the same as the address of
12473 the tracepoint and use that when you are looking at a trace frame
12474 for that tracepoint. However, this cannot work if the tracepoint has
12475 multiple locations (for instance if it was set in a function that was
12476 inlined), or if it has a @code{while-stepping} loop. In those cases
12477 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12482 @node Analyze Collected Data
12483 @section Using the Collected Data
12485 After the tracepoint experiment ends, you use @value{GDBN} commands
12486 for examining the trace data. The basic idea is that each tracepoint
12487 collects a trace @dfn{snapshot} every time it is hit and another
12488 snapshot every time it single-steps. All these snapshots are
12489 consecutively numbered from zero and go into a buffer, and you can
12490 examine them later. The way you examine them is to @dfn{focus} on a
12491 specific trace snapshot. When the remote stub is focused on a trace
12492 snapshot, it will respond to all @value{GDBN} requests for memory and
12493 registers by reading from the buffer which belongs to that snapshot,
12494 rather than from @emph{real} memory or registers of the program being
12495 debugged. This means that @strong{all} @value{GDBN} commands
12496 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12497 behave as if we were currently debugging the program state as it was
12498 when the tracepoint occurred. Any requests for data that are not in
12499 the buffer will fail.
12502 * tfind:: How to select a trace snapshot
12503 * tdump:: How to display all data for a snapshot
12504 * save tracepoints:: How to save tracepoints for a future run
12508 @subsection @code{tfind @var{n}}
12511 @cindex select trace snapshot
12512 @cindex find trace snapshot
12513 The basic command for selecting a trace snapshot from the buffer is
12514 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12515 counting from zero. If no argument @var{n} is given, the next
12516 snapshot is selected.
12518 Here are the various forms of using the @code{tfind} command.
12522 Find the first snapshot in the buffer. This is a synonym for
12523 @code{tfind 0} (since 0 is the number of the first snapshot).
12526 Stop debugging trace snapshots, resume @emph{live} debugging.
12529 Same as @samp{tfind none}.
12532 No argument means find the next trace snapshot.
12535 Find the previous trace snapshot before the current one. This permits
12536 retracing earlier steps.
12538 @item tfind tracepoint @var{num}
12539 Find the next snapshot associated with tracepoint @var{num}. Search
12540 proceeds forward from the last examined trace snapshot. If no
12541 argument @var{num} is given, it means find the next snapshot collected
12542 for the same tracepoint as the current snapshot.
12544 @item tfind pc @var{addr}
12545 Find the next snapshot associated with the value @var{addr} of the
12546 program counter. Search proceeds forward from the last examined trace
12547 snapshot. If no argument @var{addr} is given, it means find the next
12548 snapshot with the same value of PC as the current snapshot.
12550 @item tfind outside @var{addr1}, @var{addr2}
12551 Find the next snapshot whose PC is outside the given range of
12552 addresses (exclusive).
12554 @item tfind range @var{addr1}, @var{addr2}
12555 Find the next snapshot whose PC is between @var{addr1} and
12556 @var{addr2} (inclusive).
12558 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12559 Find the next snapshot associated with the source line @var{n}. If
12560 the optional argument @var{file} is given, refer to line @var{n} in
12561 that source file. Search proceeds forward from the last examined
12562 trace snapshot. If no argument @var{n} is given, it means find the
12563 next line other than the one currently being examined; thus saying
12564 @code{tfind line} repeatedly can appear to have the same effect as
12565 stepping from line to line in a @emph{live} debugging session.
12568 The default arguments for the @code{tfind} commands are specifically
12569 designed to make it easy to scan through the trace buffer. For
12570 instance, @code{tfind} with no argument selects the next trace
12571 snapshot, and @code{tfind -} with no argument selects the previous
12572 trace snapshot. So, by giving one @code{tfind} command, and then
12573 simply hitting @key{RET} repeatedly you can examine all the trace
12574 snapshots in order. Or, by saying @code{tfind -} and then hitting
12575 @key{RET} repeatedly you can examine the snapshots in reverse order.
12576 The @code{tfind line} command with no argument selects the snapshot
12577 for the next source line executed. The @code{tfind pc} command with
12578 no argument selects the next snapshot with the same program counter
12579 (PC) as the current frame. The @code{tfind tracepoint} command with
12580 no argument selects the next trace snapshot collected by the same
12581 tracepoint as the current one.
12583 In addition to letting you scan through the trace buffer manually,
12584 these commands make it easy to construct @value{GDBN} scripts that
12585 scan through the trace buffer and print out whatever collected data
12586 you are interested in. Thus, if we want to examine the PC, FP, and SP
12587 registers from each trace frame in the buffer, we can say this:
12590 (@value{GDBP}) @b{tfind start}
12591 (@value{GDBP}) @b{while ($trace_frame != -1)}
12592 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12593 $trace_frame, $pc, $sp, $fp
12597 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12598 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12599 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12600 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12601 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12602 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12603 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12604 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12605 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12606 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12607 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12610 Or, if we want to examine the variable @code{X} at each source line in
12614 (@value{GDBP}) @b{tfind start}
12615 (@value{GDBP}) @b{while ($trace_frame != -1)}
12616 > printf "Frame %d, X == %d\n", $trace_frame, X
12626 @subsection @code{tdump}
12628 @cindex dump all data collected at tracepoint
12629 @cindex tracepoint data, display
12631 This command takes no arguments. It prints all the data collected at
12632 the current trace snapshot.
12635 (@value{GDBP}) @b{trace 444}
12636 (@value{GDBP}) @b{actions}
12637 Enter actions for tracepoint #2, one per line:
12638 > collect $regs, $locals, $args, gdb_long_test
12641 (@value{GDBP}) @b{tstart}
12643 (@value{GDBP}) @b{tfind line 444}
12644 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12646 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12648 (@value{GDBP}) @b{tdump}
12649 Data collected at tracepoint 2, trace frame 1:
12650 d0 0xc4aa0085 -995491707
12654 d4 0x71aea3d 119204413
12657 d7 0x380035 3670069
12658 a0 0x19e24a 1696330
12659 a1 0x3000668 50333288
12661 a3 0x322000 3284992
12662 a4 0x3000698 50333336
12663 a5 0x1ad3cc 1758156
12664 fp 0x30bf3c 0x30bf3c
12665 sp 0x30bf34 0x30bf34
12667 pc 0x20b2c8 0x20b2c8
12671 p = 0x20e5b4 "gdb-test"
12678 gdb_long_test = 17 '\021'
12683 @code{tdump} works by scanning the tracepoint's current collection
12684 actions and printing the value of each expression listed. So
12685 @code{tdump} can fail, if after a run, you change the tracepoint's
12686 actions to mention variables that were not collected during the run.
12688 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12689 uses the collected value of @code{$pc} to distinguish between trace
12690 frames that were collected at the tracepoint hit, and frames that were
12691 collected while stepping. This allows it to correctly choose whether
12692 to display the basic list of collections, or the collections from the
12693 body of the while-stepping loop. However, if @code{$pc} was not collected,
12694 then @code{tdump} will always attempt to dump using the basic collection
12695 list, and may fail if a while-stepping frame does not include all the
12696 same data that is collected at the tracepoint hit.
12697 @c This is getting pretty arcane, example would be good.
12699 @node save tracepoints
12700 @subsection @code{save tracepoints @var{filename}}
12701 @kindex save tracepoints
12702 @kindex save-tracepoints
12703 @cindex save tracepoints for future sessions
12705 This command saves all current tracepoint definitions together with
12706 their actions and passcounts, into a file @file{@var{filename}}
12707 suitable for use in a later debugging session. To read the saved
12708 tracepoint definitions, use the @code{source} command (@pxref{Command
12709 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12710 alias for @w{@code{save tracepoints}}
12712 @node Tracepoint Variables
12713 @section Convenience Variables for Tracepoints
12714 @cindex tracepoint variables
12715 @cindex convenience variables for tracepoints
12718 @vindex $trace_frame
12719 @item (int) $trace_frame
12720 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12721 snapshot is selected.
12723 @vindex $tracepoint
12724 @item (int) $tracepoint
12725 The tracepoint for the current trace snapshot.
12727 @vindex $trace_line
12728 @item (int) $trace_line
12729 The line number for the current trace snapshot.
12731 @vindex $trace_file
12732 @item (char []) $trace_file
12733 The source file for the current trace snapshot.
12735 @vindex $trace_func
12736 @item (char []) $trace_func
12737 The name of the function containing @code{$tracepoint}.
12740 Note: @code{$trace_file} is not suitable for use in @code{printf},
12741 use @code{output} instead.
12743 Here's a simple example of using these convenience variables for
12744 stepping through all the trace snapshots and printing some of their
12745 data. Note that these are not the same as trace state variables,
12746 which are managed by the target.
12749 (@value{GDBP}) @b{tfind start}
12751 (@value{GDBP}) @b{while $trace_frame != -1}
12752 > output $trace_file
12753 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12759 @section Using Trace Files
12760 @cindex trace files
12762 In some situations, the target running a trace experiment may no
12763 longer be available; perhaps it crashed, or the hardware was needed
12764 for a different activity. To handle these cases, you can arrange to
12765 dump the trace data into a file, and later use that file as a source
12766 of trace data, via the @code{target tfile} command.
12771 @item tsave [ -r ] @var{filename}
12772 @itemx tsave [-ctf] @var{dirname}
12773 Save the trace data to @var{filename}. By default, this command
12774 assumes that @var{filename} refers to the host filesystem, so if
12775 necessary @value{GDBN} will copy raw trace data up from the target and
12776 then save it. If the target supports it, you can also supply the
12777 optional argument @code{-r} (``remote'') to direct the target to save
12778 the data directly into @var{filename} in its own filesystem, which may be
12779 more efficient if the trace buffer is very large. (Note, however, that
12780 @code{target tfile} can only read from files accessible to the host.)
12781 By default, this command will save trace frame in tfile format.
12782 You can supply the optional argument @code{-ctf} to save date in CTF
12783 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12784 that can be shared by multiple debugging and tracing tools. Please go to
12785 @indicateurl{http://www.efficios.com/ctf} to get more information.
12787 @kindex target tfile
12791 @item target tfile @var{filename}
12792 @itemx target ctf @var{dirname}
12793 Use the file named @var{filename} or directory named @var{dirname} as
12794 a source of trace data. Commands that examine data work as they do with
12795 a live target, but it is not possible to run any new trace experiments.
12796 @code{tstatus} will report the state of the trace run at the moment
12797 the data was saved, as well as the current trace frame you are examining.
12798 @var{filename} or @var{dirname} must be on a filesystem accessible to
12802 (@value{GDBP}) target ctf ctf.ctf
12803 (@value{GDBP}) tfind
12804 Found trace frame 0, tracepoint 2
12805 39 ++a; /* set tracepoint 1 here */
12806 (@value{GDBP}) tdump
12807 Data collected at tracepoint 2, trace frame 0:
12811 c = @{"123", "456", "789", "123", "456", "789"@}
12812 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12820 @chapter Debugging Programs That Use Overlays
12823 If your program is too large to fit completely in your target system's
12824 memory, you can sometimes use @dfn{overlays} to work around this
12825 problem. @value{GDBN} provides some support for debugging programs that
12829 * How Overlays Work:: A general explanation of overlays.
12830 * Overlay Commands:: Managing overlays in @value{GDBN}.
12831 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12832 mapped by asking the inferior.
12833 * Overlay Sample Program:: A sample program using overlays.
12836 @node How Overlays Work
12837 @section How Overlays Work
12838 @cindex mapped overlays
12839 @cindex unmapped overlays
12840 @cindex load address, overlay's
12841 @cindex mapped address
12842 @cindex overlay area
12844 Suppose you have a computer whose instruction address space is only 64
12845 kilobytes long, but which has much more memory which can be accessed by
12846 other means: special instructions, segment registers, or memory
12847 management hardware, for example. Suppose further that you want to
12848 adapt a program which is larger than 64 kilobytes to run on this system.
12850 One solution is to identify modules of your program which are relatively
12851 independent, and need not call each other directly; call these modules
12852 @dfn{overlays}. Separate the overlays from the main program, and place
12853 their machine code in the larger memory. Place your main program in
12854 instruction memory, but leave at least enough space there to hold the
12855 largest overlay as well.
12857 Now, to call a function located in an overlay, you must first copy that
12858 overlay's machine code from the large memory into the space set aside
12859 for it in the instruction memory, and then jump to its entry point
12862 @c NB: In the below the mapped area's size is greater or equal to the
12863 @c size of all overlays. This is intentional to remind the developer
12864 @c that overlays don't necessarily need to be the same size.
12868 Data Instruction Larger
12869 Address Space Address Space Address Space
12870 +-----------+ +-----------+ +-----------+
12872 +-----------+ +-----------+ +-----------+<-- overlay 1
12873 | program | | main | .----| overlay 1 | load address
12874 | variables | | program | | +-----------+
12875 | and heap | | | | | |
12876 +-----------+ | | | +-----------+<-- overlay 2
12877 | | +-----------+ | | | load address
12878 +-----------+ | | | .-| overlay 2 |
12880 mapped --->+-----------+ | | +-----------+
12881 address | | | | | |
12882 | overlay | <-' | | |
12883 | area | <---' +-----------+<-- overlay 3
12884 | | <---. | | load address
12885 +-----------+ `--| overlay 3 |
12892 @anchor{A code overlay}A code overlay
12896 The diagram (@pxref{A code overlay}) shows a system with separate data
12897 and instruction address spaces. To map an overlay, the program copies
12898 its code from the larger address space to the instruction address space.
12899 Since the overlays shown here all use the same mapped address, only one
12900 may be mapped at a time. For a system with a single address space for
12901 data and instructions, the diagram would be similar, except that the
12902 program variables and heap would share an address space with the main
12903 program and the overlay area.
12905 An overlay loaded into instruction memory and ready for use is called a
12906 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12907 instruction memory. An overlay not present (or only partially present)
12908 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12909 is its address in the larger memory. The mapped address is also called
12910 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12911 called the @dfn{load memory address}, or @dfn{LMA}.
12913 Unfortunately, overlays are not a completely transparent way to adapt a
12914 program to limited instruction memory. They introduce a new set of
12915 global constraints you must keep in mind as you design your program:
12920 Before calling or returning to a function in an overlay, your program
12921 must make sure that overlay is actually mapped. Otherwise, the call or
12922 return will transfer control to the right address, but in the wrong
12923 overlay, and your program will probably crash.
12926 If the process of mapping an overlay is expensive on your system, you
12927 will need to choose your overlays carefully to minimize their effect on
12928 your program's performance.
12931 The executable file you load onto your system must contain each
12932 overlay's instructions, appearing at the overlay's load address, not its
12933 mapped address. However, each overlay's instructions must be relocated
12934 and its symbols defined as if the overlay were at its mapped address.
12935 You can use GNU linker scripts to specify different load and relocation
12936 addresses for pieces of your program; see @ref{Overlay Description,,,
12937 ld.info, Using ld: the GNU linker}.
12940 The procedure for loading executable files onto your system must be able
12941 to load their contents into the larger address space as well as the
12942 instruction and data spaces.
12946 The overlay system described above is rather simple, and could be
12947 improved in many ways:
12952 If your system has suitable bank switch registers or memory management
12953 hardware, you could use those facilities to make an overlay's load area
12954 contents simply appear at their mapped address in instruction space.
12955 This would probably be faster than copying the overlay to its mapped
12956 area in the usual way.
12959 If your overlays are small enough, you could set aside more than one
12960 overlay area, and have more than one overlay mapped at a time.
12963 You can use overlays to manage data, as well as instructions. In
12964 general, data overlays are even less transparent to your design than
12965 code overlays: whereas code overlays only require care when you call or
12966 return to functions, data overlays require care every time you access
12967 the data. Also, if you change the contents of a data overlay, you
12968 must copy its contents back out to its load address before you can copy a
12969 different data overlay into the same mapped area.
12974 @node Overlay Commands
12975 @section Overlay Commands
12977 To use @value{GDBN}'s overlay support, each overlay in your program must
12978 correspond to a separate section of the executable file. The section's
12979 virtual memory address and load memory address must be the overlay's
12980 mapped and load addresses. Identifying overlays with sections allows
12981 @value{GDBN} to determine the appropriate address of a function or
12982 variable, depending on whether the overlay is mapped or not.
12984 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12985 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12990 Disable @value{GDBN}'s overlay support. When overlay support is
12991 disabled, @value{GDBN} assumes that all functions and variables are
12992 always present at their mapped addresses. By default, @value{GDBN}'s
12993 overlay support is disabled.
12995 @item overlay manual
12996 @cindex manual overlay debugging
12997 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12998 relies on you to tell it which overlays are mapped, and which are not,
12999 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13000 commands described below.
13002 @item overlay map-overlay @var{overlay}
13003 @itemx overlay map @var{overlay}
13004 @cindex map an overlay
13005 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13006 be the name of the object file section containing the overlay. When an
13007 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13008 functions and variables at their mapped addresses. @value{GDBN} assumes
13009 that any other overlays whose mapped ranges overlap that of
13010 @var{overlay} are now unmapped.
13012 @item overlay unmap-overlay @var{overlay}
13013 @itemx overlay unmap @var{overlay}
13014 @cindex unmap an overlay
13015 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13016 must be the name of the object file section containing the overlay.
13017 When an overlay is unmapped, @value{GDBN} assumes it can find the
13018 overlay's functions and variables at their load addresses.
13021 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13022 consults a data structure the overlay manager maintains in the inferior
13023 to see which overlays are mapped. For details, see @ref{Automatic
13024 Overlay Debugging}.
13026 @item overlay load-target
13027 @itemx overlay load
13028 @cindex reloading the overlay table
13029 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13030 re-reads the table @value{GDBN} automatically each time the inferior
13031 stops, so this command should only be necessary if you have changed the
13032 overlay mapping yourself using @value{GDBN}. This command is only
13033 useful when using automatic overlay debugging.
13035 @item overlay list-overlays
13036 @itemx overlay list
13037 @cindex listing mapped overlays
13038 Display a list of the overlays currently mapped, along with their mapped
13039 addresses, load addresses, and sizes.
13043 Normally, when @value{GDBN} prints a code address, it includes the name
13044 of the function the address falls in:
13047 (@value{GDBP}) print main
13048 $3 = @{int ()@} 0x11a0 <main>
13051 When overlay debugging is enabled, @value{GDBN} recognizes code in
13052 unmapped overlays, and prints the names of unmapped functions with
13053 asterisks around them. For example, if @code{foo} is a function in an
13054 unmapped overlay, @value{GDBN} prints it this way:
13057 (@value{GDBP}) overlay list
13058 No sections are mapped.
13059 (@value{GDBP}) print foo
13060 $5 = @{int (int)@} 0x100000 <*foo*>
13063 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13067 (@value{GDBP}) overlay list
13068 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13069 mapped at 0x1016 - 0x104a
13070 (@value{GDBP}) print foo
13071 $6 = @{int (int)@} 0x1016 <foo>
13074 When overlay debugging is enabled, @value{GDBN} can find the correct
13075 address for functions and variables in an overlay, whether or not the
13076 overlay is mapped. This allows most @value{GDBN} commands, like
13077 @code{break} and @code{disassemble}, to work normally, even on unmapped
13078 code. However, @value{GDBN}'s breakpoint support has some limitations:
13082 @cindex breakpoints in overlays
13083 @cindex overlays, setting breakpoints in
13084 You can set breakpoints in functions in unmapped overlays, as long as
13085 @value{GDBN} can write to the overlay at its load address.
13087 @value{GDBN} can not set hardware or simulator-based breakpoints in
13088 unmapped overlays. However, if you set a breakpoint at the end of your
13089 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13090 you are using manual overlay management), @value{GDBN} will re-set its
13091 breakpoints properly.
13095 @node Automatic Overlay Debugging
13096 @section Automatic Overlay Debugging
13097 @cindex automatic overlay debugging
13099 @value{GDBN} can automatically track which overlays are mapped and which
13100 are not, given some simple co-operation from the overlay manager in the
13101 inferior. If you enable automatic overlay debugging with the
13102 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13103 looks in the inferior's memory for certain variables describing the
13104 current state of the overlays.
13106 Here are the variables your overlay manager must define to support
13107 @value{GDBN}'s automatic overlay debugging:
13111 @item @code{_ovly_table}:
13112 This variable must be an array of the following structures:
13117 /* The overlay's mapped address. */
13120 /* The size of the overlay, in bytes. */
13121 unsigned long size;
13123 /* The overlay's load address. */
13126 /* Non-zero if the overlay is currently mapped;
13128 unsigned long mapped;
13132 @item @code{_novlys}:
13133 This variable must be a four-byte signed integer, holding the total
13134 number of elements in @code{_ovly_table}.
13138 To decide whether a particular overlay is mapped or not, @value{GDBN}
13139 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13140 @code{lma} members equal the VMA and LMA of the overlay's section in the
13141 executable file. When @value{GDBN} finds a matching entry, it consults
13142 the entry's @code{mapped} member to determine whether the overlay is
13145 In addition, your overlay manager may define a function called
13146 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13147 will silently set a breakpoint there. If the overlay manager then
13148 calls this function whenever it has changed the overlay table, this
13149 will enable @value{GDBN} to accurately keep track of which overlays
13150 are in program memory, and update any breakpoints that may be set
13151 in overlays. This will allow breakpoints to work even if the
13152 overlays are kept in ROM or other non-writable memory while they
13153 are not being executed.
13155 @node Overlay Sample Program
13156 @section Overlay Sample Program
13157 @cindex overlay example program
13159 When linking a program which uses overlays, you must place the overlays
13160 at their load addresses, while relocating them to run at their mapped
13161 addresses. To do this, you must write a linker script (@pxref{Overlay
13162 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13163 since linker scripts are specific to a particular host system, target
13164 architecture, and target memory layout, this manual cannot provide
13165 portable sample code demonstrating @value{GDBN}'s overlay support.
13167 However, the @value{GDBN} source distribution does contain an overlaid
13168 program, with linker scripts for a few systems, as part of its test
13169 suite. The program consists of the following files from
13170 @file{gdb/testsuite/gdb.base}:
13174 The main program file.
13176 A simple overlay manager, used by @file{overlays.c}.
13181 Overlay modules, loaded and used by @file{overlays.c}.
13184 Linker scripts for linking the test program on the @code{d10v-elf}
13185 and @code{m32r-elf} targets.
13188 You can build the test program using the @code{d10v-elf} GCC
13189 cross-compiler like this:
13192 $ d10v-elf-gcc -g -c overlays.c
13193 $ d10v-elf-gcc -g -c ovlymgr.c
13194 $ d10v-elf-gcc -g -c foo.c
13195 $ d10v-elf-gcc -g -c bar.c
13196 $ d10v-elf-gcc -g -c baz.c
13197 $ d10v-elf-gcc -g -c grbx.c
13198 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13199 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13202 The build process is identical for any other architecture, except that
13203 you must substitute the appropriate compiler and linker script for the
13204 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13208 @chapter Using @value{GDBN} with Different Languages
13211 Although programming languages generally have common aspects, they are
13212 rarely expressed in the same manner. For instance, in ANSI C,
13213 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13214 Modula-2, it is accomplished by @code{p^}. Values can also be
13215 represented (and displayed) differently. Hex numbers in C appear as
13216 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13218 @cindex working language
13219 Language-specific information is built into @value{GDBN} for some languages,
13220 allowing you to express operations like the above in your program's
13221 native language, and allowing @value{GDBN} to output values in a manner
13222 consistent with the syntax of your program's native language. The
13223 language you use to build expressions is called the @dfn{working
13227 * Setting:: Switching between source languages
13228 * Show:: Displaying the language
13229 * Checks:: Type and range checks
13230 * Supported Languages:: Supported languages
13231 * Unsupported Languages:: Unsupported languages
13235 @section Switching Between Source Languages
13237 There are two ways to control the working language---either have @value{GDBN}
13238 set it automatically, or select it manually yourself. You can use the
13239 @code{set language} command for either purpose. On startup, @value{GDBN}
13240 defaults to setting the language automatically. The working language is
13241 used to determine how expressions you type are interpreted, how values
13244 In addition to the working language, every source file that
13245 @value{GDBN} knows about has its own working language. For some object
13246 file formats, the compiler might indicate which language a particular
13247 source file is in. However, most of the time @value{GDBN} infers the
13248 language from the name of the file. The language of a source file
13249 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13250 show each frame appropriately for its own language. There is no way to
13251 set the language of a source file from within @value{GDBN}, but you can
13252 set the language associated with a filename extension. @xref{Show, ,
13253 Displaying the Language}.
13255 This is most commonly a problem when you use a program, such
13256 as @code{cfront} or @code{f2c}, that generates C but is written in
13257 another language. In that case, make the
13258 program use @code{#line} directives in its C output; that way
13259 @value{GDBN} will know the correct language of the source code of the original
13260 program, and will display that source code, not the generated C code.
13263 * Filenames:: Filename extensions and languages.
13264 * Manually:: Setting the working language manually
13265 * Automatically:: Having @value{GDBN} infer the source language
13269 @subsection List of Filename Extensions and Languages
13271 If a source file name ends in one of the following extensions, then
13272 @value{GDBN} infers that its language is the one indicated.
13290 C@t{++} source file
13296 Objective-C source file
13300 Fortran source file
13303 Modula-2 source file
13307 Assembler source file. This actually behaves almost like C, but
13308 @value{GDBN} does not skip over function prologues when stepping.
13311 In addition, you may set the language associated with a filename
13312 extension. @xref{Show, , Displaying the Language}.
13315 @subsection Setting the Working Language
13317 If you allow @value{GDBN} to set the language automatically,
13318 expressions are interpreted the same way in your debugging session and
13321 @kindex set language
13322 If you wish, you may set the language manually. To do this, issue the
13323 command @samp{set language @var{lang}}, where @var{lang} is the name of
13324 a language, such as
13325 @code{c} or @code{modula-2}.
13326 For a list of the supported languages, type @samp{set language}.
13328 Setting the language manually prevents @value{GDBN} from updating the working
13329 language automatically. This can lead to confusion if you try
13330 to debug a program when the working language is not the same as the
13331 source language, when an expression is acceptable to both
13332 languages---but means different things. For instance, if the current
13333 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13341 might not have the effect you intended. In C, this means to add
13342 @code{b} and @code{c} and place the result in @code{a}. The result
13343 printed would be the value of @code{a}. In Modula-2, this means to compare
13344 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13346 @node Automatically
13347 @subsection Having @value{GDBN} Infer the Source Language
13349 To have @value{GDBN} set the working language automatically, use
13350 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13351 then infers the working language. That is, when your program stops in a
13352 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13353 working language to the language recorded for the function in that
13354 frame. If the language for a frame is unknown (that is, if the function
13355 or block corresponding to the frame was defined in a source file that
13356 does not have a recognized extension), the current working language is
13357 not changed, and @value{GDBN} issues a warning.
13359 This may not seem necessary for most programs, which are written
13360 entirely in one source language. However, program modules and libraries
13361 written in one source language can be used by a main program written in
13362 a different source language. Using @samp{set language auto} in this
13363 case frees you from having to set the working language manually.
13366 @section Displaying the Language
13368 The following commands help you find out which language is the
13369 working language, and also what language source files were written in.
13372 @item show language
13373 @anchor{show language}
13374 @kindex show language
13375 Display the current working language. This is the
13376 language you can use with commands such as @code{print} to
13377 build and compute expressions that may involve variables in your program.
13380 @kindex info frame@r{, show the source language}
13381 Display the source language for this frame. This language becomes the
13382 working language if you use an identifier from this frame.
13383 @xref{Frame Info, ,Information about a Frame}, to identify the other
13384 information listed here.
13387 @kindex info source@r{, show the source language}
13388 Display the source language of this source file.
13389 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13390 information listed here.
13393 In unusual circumstances, you may have source files with extensions
13394 not in the standard list. You can then set the extension associated
13395 with a language explicitly:
13398 @item set extension-language @var{ext} @var{language}
13399 @kindex set extension-language
13400 Tell @value{GDBN} that source files with extension @var{ext} are to be
13401 assumed as written in the source language @var{language}.
13403 @item info extensions
13404 @kindex info extensions
13405 List all the filename extensions and the associated languages.
13409 @section Type and Range Checking
13411 Some languages are designed to guard you against making seemingly common
13412 errors through a series of compile- and run-time checks. These include
13413 checking the type of arguments to functions and operators and making
13414 sure mathematical overflows are caught at run time. Checks such as
13415 these help to ensure a program's correctness once it has been compiled
13416 by eliminating type mismatches and providing active checks for range
13417 errors when your program is running.
13419 By default @value{GDBN} checks for these errors according to the
13420 rules of the current source language. Although @value{GDBN} does not check
13421 the statements in your program, it can check expressions entered directly
13422 into @value{GDBN} for evaluation via the @code{print} command, for example.
13425 * Type Checking:: An overview of type checking
13426 * Range Checking:: An overview of range checking
13429 @cindex type checking
13430 @cindex checks, type
13431 @node Type Checking
13432 @subsection An Overview of Type Checking
13434 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13435 arguments to operators and functions have to be of the correct type,
13436 otherwise an error occurs. These checks prevent type mismatch
13437 errors from ever causing any run-time problems. For example,
13440 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13442 (@value{GDBP}) print obj.my_method (0)
13445 (@value{GDBP}) print obj.my_method (0x1234)
13446 Cannot resolve method klass::my_method to any overloaded instance
13449 The second example fails because in C@t{++} the integer constant
13450 @samp{0x1234} is not type-compatible with the pointer parameter type.
13452 For the expressions you use in @value{GDBN} commands, you can tell
13453 @value{GDBN} to not enforce strict type checking or
13454 to treat any mismatches as errors and abandon the expression;
13455 When type checking is disabled, @value{GDBN} successfully evaluates
13456 expressions like the second example above.
13458 Even if type checking is off, there may be other reasons
13459 related to type that prevent @value{GDBN} from evaluating an expression.
13460 For instance, @value{GDBN} does not know how to add an @code{int} and
13461 a @code{struct foo}. These particular type errors have nothing to do
13462 with the language in use and usually arise from expressions which make
13463 little sense to evaluate anyway.
13465 @value{GDBN} provides some additional commands for controlling type checking:
13467 @kindex set check type
13468 @kindex show check type
13470 @item set check type on
13471 @itemx set check type off
13472 Set strict type checking on or off. If any type mismatches occur in
13473 evaluating an expression while type checking is on, @value{GDBN} prints a
13474 message and aborts evaluation of the expression.
13476 @item show check type
13477 Show the current setting of type checking and whether @value{GDBN}
13478 is enforcing strict type checking rules.
13481 @cindex range checking
13482 @cindex checks, range
13483 @node Range Checking
13484 @subsection An Overview of Range Checking
13486 In some languages (such as Modula-2), it is an error to exceed the
13487 bounds of a type; this is enforced with run-time checks. Such range
13488 checking is meant to ensure program correctness by making sure
13489 computations do not overflow, or indices on an array element access do
13490 not exceed the bounds of the array.
13492 For expressions you use in @value{GDBN} commands, you can tell
13493 @value{GDBN} to treat range errors in one of three ways: ignore them,
13494 always treat them as errors and abandon the expression, or issue
13495 warnings but evaluate the expression anyway.
13497 A range error can result from numerical overflow, from exceeding an
13498 array index bound, or when you type a constant that is not a member
13499 of any type. Some languages, however, do not treat overflows as an
13500 error. In many implementations of C, mathematical overflow causes the
13501 result to ``wrap around'' to lower values---for example, if @var{m} is
13502 the largest integer value, and @var{s} is the smallest, then
13505 @var{m} + 1 @result{} @var{s}
13508 This, too, is specific to individual languages, and in some cases
13509 specific to individual compilers or machines. @xref{Supported Languages, ,
13510 Supported Languages}, for further details on specific languages.
13512 @value{GDBN} provides some additional commands for controlling the range checker:
13514 @kindex set check range
13515 @kindex show check range
13517 @item set check range auto
13518 Set range checking on or off based on the current working language.
13519 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13522 @item set check range on
13523 @itemx set check range off
13524 Set range checking on or off, overriding the default setting for the
13525 current working language. A warning is issued if the setting does not
13526 match the language default. If a range error occurs and range checking is on,
13527 then a message is printed and evaluation of the expression is aborted.
13529 @item set check range warn
13530 Output messages when the @value{GDBN} range checker detects a range error,
13531 but attempt to evaluate the expression anyway. Evaluating the
13532 expression may still be impossible for other reasons, such as accessing
13533 memory that the process does not own (a typical example from many Unix
13537 Show the current setting of the range checker, and whether or not it is
13538 being set automatically by @value{GDBN}.
13541 @node Supported Languages
13542 @section Supported Languages
13544 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13545 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13546 @c This is false ...
13547 Some @value{GDBN} features may be used in expressions regardless of the
13548 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13549 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13550 ,Expressions}) can be used with the constructs of any supported
13553 The following sections detail to what degree each source language is
13554 supported by @value{GDBN}. These sections are not meant to be language
13555 tutorials or references, but serve only as a reference guide to what the
13556 @value{GDBN} expression parser accepts, and what input and output
13557 formats should look like for different languages. There are many good
13558 books written on each of these languages; please look to these for a
13559 language reference or tutorial.
13562 * C:: C and C@t{++}
13565 * Objective-C:: Objective-C
13566 * OpenCL C:: OpenCL C
13567 * Fortran:: Fortran
13569 * Modula-2:: Modula-2
13574 @subsection C and C@t{++}
13576 @cindex C and C@t{++}
13577 @cindex expressions in C or C@t{++}
13579 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13580 to both languages. Whenever this is the case, we discuss those languages
13584 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13585 @cindex @sc{gnu} C@t{++}
13586 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13587 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13588 effectively, you must compile your C@t{++} programs with a supported
13589 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13590 compiler (@code{aCC}).
13593 * C Operators:: C and C@t{++} operators
13594 * C Constants:: C and C@t{++} constants
13595 * C Plus Plus Expressions:: C@t{++} expressions
13596 * C Defaults:: Default settings for C and C@t{++}
13597 * C Checks:: C and C@t{++} type and range checks
13598 * Debugging C:: @value{GDBN} and C
13599 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13600 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13604 @subsubsection C and C@t{++} Operators
13606 @cindex C and C@t{++} operators
13608 Operators must be defined on values of specific types. For instance,
13609 @code{+} is defined on numbers, but not on structures. Operators are
13610 often defined on groups of types.
13612 For the purposes of C and C@t{++}, the following definitions hold:
13617 @emph{Integral types} include @code{int} with any of its storage-class
13618 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13621 @emph{Floating-point types} include @code{float}, @code{double}, and
13622 @code{long double} (if supported by the target platform).
13625 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13628 @emph{Scalar types} include all of the above.
13633 The following operators are supported. They are listed here
13634 in order of increasing precedence:
13638 The comma or sequencing operator. Expressions in a comma-separated list
13639 are evaluated from left to right, with the result of the entire
13640 expression being the last expression evaluated.
13643 Assignment. The value of an assignment expression is the value
13644 assigned. Defined on scalar types.
13647 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13648 and translated to @w{@code{@var{a} = @var{a op b}}}.
13649 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13650 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13651 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13654 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13655 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13659 Logical @sc{or}. Defined on integral types.
13662 Logical @sc{and}. Defined on integral types.
13665 Bitwise @sc{or}. Defined on integral types.
13668 Bitwise exclusive-@sc{or}. Defined on integral types.
13671 Bitwise @sc{and}. Defined on integral types.
13674 Equality and inequality. Defined on scalar types. The value of these
13675 expressions is 0 for false and non-zero for true.
13677 @item <@r{, }>@r{, }<=@r{, }>=
13678 Less than, greater than, less than or equal, greater than or equal.
13679 Defined on scalar types. The value of these expressions is 0 for false
13680 and non-zero for true.
13683 left shift, and right shift. Defined on integral types.
13686 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13689 Addition and subtraction. Defined on integral types, floating-point types and
13692 @item *@r{, }/@r{, }%
13693 Multiplication, division, and modulus. Multiplication and division are
13694 defined on integral and floating-point types. Modulus is defined on
13698 Increment and decrement. When appearing before a variable, the
13699 operation is performed before the variable is used in an expression;
13700 when appearing after it, the variable's value is used before the
13701 operation takes place.
13704 Pointer dereferencing. Defined on pointer types. Same precedence as
13708 Address operator. Defined on variables. Same precedence as @code{++}.
13710 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13711 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13712 to examine the address
13713 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13717 Negative. Defined on integral and floating-point types. Same
13718 precedence as @code{++}.
13721 Logical negation. Defined on integral types. Same precedence as
13725 Bitwise complement operator. Defined on integral types. Same precedence as
13730 Structure member, and pointer-to-structure member. For convenience,
13731 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13732 pointer based on the stored type information.
13733 Defined on @code{struct} and @code{union} data.
13736 Dereferences of pointers to members.
13739 Array indexing. @code{@var{a}[@var{i}]} is defined as
13740 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13743 Function parameter list. Same precedence as @code{->}.
13746 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13747 and @code{class} types.
13750 Doubled colons also represent the @value{GDBN} scope operator
13751 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13755 If an operator is redefined in the user code, @value{GDBN} usually
13756 attempts to invoke the redefined version instead of using the operator's
13757 predefined meaning.
13760 @subsubsection C and C@t{++} Constants
13762 @cindex C and C@t{++} constants
13764 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13769 Integer constants are a sequence of digits. Octal constants are
13770 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13771 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13772 @samp{l}, specifying that the constant should be treated as a
13776 Floating point constants are a sequence of digits, followed by a decimal
13777 point, followed by a sequence of digits, and optionally followed by an
13778 exponent. An exponent is of the form:
13779 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13780 sequence of digits. The @samp{+} is optional for positive exponents.
13781 A floating-point constant may also end with a letter @samp{f} or
13782 @samp{F}, specifying that the constant should be treated as being of
13783 the @code{float} (as opposed to the default @code{double}) type; or with
13784 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13788 Enumerated constants consist of enumerated identifiers, or their
13789 integral equivalents.
13792 Character constants are a single character surrounded by single quotes
13793 (@code{'}), or a number---the ordinal value of the corresponding character
13794 (usually its @sc{ascii} value). Within quotes, the single character may
13795 be represented by a letter or by @dfn{escape sequences}, which are of
13796 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13797 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13798 @samp{@var{x}} is a predefined special character---for example,
13799 @samp{\n} for newline.
13801 Wide character constants can be written by prefixing a character
13802 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13803 form of @samp{x}. The target wide character set is used when
13804 computing the value of this constant (@pxref{Character Sets}).
13807 String constants are a sequence of character constants surrounded by
13808 double quotes (@code{"}). Any valid character constant (as described
13809 above) may appear. Double quotes within the string must be preceded by
13810 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13813 Wide string constants can be written by prefixing a string constant
13814 with @samp{L}, as in C. The target wide character set is used when
13815 computing the value of this constant (@pxref{Character Sets}).
13818 Pointer constants are an integral value. You can also write pointers
13819 to constants using the C operator @samp{&}.
13822 Array constants are comma-separated lists surrounded by braces @samp{@{}
13823 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13824 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13825 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13828 @node C Plus Plus Expressions
13829 @subsubsection C@t{++} Expressions
13831 @cindex expressions in C@t{++}
13832 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13834 @cindex debugging C@t{++} programs
13835 @cindex C@t{++} compilers
13836 @cindex debug formats and C@t{++}
13837 @cindex @value{NGCC} and C@t{++}
13839 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13840 the proper compiler and the proper debug format. Currently,
13841 @value{GDBN} works best when debugging C@t{++} code that is compiled
13842 with the most recent version of @value{NGCC} possible. The DWARF
13843 debugging format is preferred; @value{NGCC} defaults to this on most
13844 popular platforms. Other compilers and/or debug formats are likely to
13845 work badly or not at all when using @value{GDBN} to debug C@t{++}
13846 code. @xref{Compilation}.
13851 @cindex member functions
13853 Member function calls are allowed; you can use expressions like
13856 count = aml->GetOriginal(x, y)
13859 @vindex this@r{, inside C@t{++} member functions}
13860 @cindex namespace in C@t{++}
13862 While a member function is active (in the selected stack frame), your
13863 expressions have the same namespace available as the member function;
13864 that is, @value{GDBN} allows implicit references to the class instance
13865 pointer @code{this} following the same rules as C@t{++}. @code{using}
13866 declarations in the current scope are also respected by @value{GDBN}.
13868 @cindex call overloaded functions
13869 @cindex overloaded functions, calling
13870 @cindex type conversions in C@t{++}
13872 You can call overloaded functions; @value{GDBN} resolves the function
13873 call to the right definition, with some restrictions. @value{GDBN} does not
13874 perform overload resolution involving user-defined type conversions,
13875 calls to constructors, or instantiations of templates that do not exist
13876 in the program. It also cannot handle ellipsis argument lists or
13879 It does perform integral conversions and promotions, floating-point
13880 promotions, arithmetic conversions, pointer conversions, conversions of
13881 class objects to base classes, and standard conversions such as those of
13882 functions or arrays to pointers; it requires an exact match on the
13883 number of function arguments.
13885 Overload resolution is always performed, unless you have specified
13886 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13887 ,@value{GDBN} Features for C@t{++}}.
13889 You must specify @code{set overload-resolution off} in order to use an
13890 explicit function signature to call an overloaded function, as in
13892 p 'foo(char,int)'('x', 13)
13895 The @value{GDBN} command-completion facility can simplify this;
13896 see @ref{Completion, ,Command Completion}.
13898 @cindex reference declarations
13900 @value{GDBN} understands variables declared as C@t{++} references; you can use
13901 them in expressions just as you do in C@t{++} source---they are automatically
13904 In the parameter list shown when @value{GDBN} displays a frame, the values of
13905 reference variables are not displayed (unlike other variables); this
13906 avoids clutter, since references are often used for large structures.
13907 The @emph{address} of a reference variable is always shown, unless
13908 you have specified @samp{set print address off}.
13911 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13912 expressions can use it just as expressions in your program do. Since
13913 one scope may be defined in another, you can use @code{::} repeatedly if
13914 necessary, for example in an expression like
13915 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13916 resolving name scope by reference to source files, in both C and C@t{++}
13917 debugging (@pxref{Variables, ,Program Variables}).
13920 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13925 @subsubsection C and C@t{++} Defaults
13927 @cindex C and C@t{++} defaults
13929 If you allow @value{GDBN} to set range checking automatically, it
13930 defaults to @code{off} whenever the working language changes to
13931 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13932 selects the working language.
13934 If you allow @value{GDBN} to set the language automatically, it
13935 recognizes source files whose names end with @file{.c}, @file{.C}, or
13936 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13937 these files, it sets the working language to C or C@t{++}.
13938 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13939 for further details.
13942 @subsubsection C and C@t{++} Type and Range Checks
13944 @cindex C and C@t{++} checks
13946 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13947 checking is used. However, if you turn type checking off, @value{GDBN}
13948 will allow certain non-standard conversions, such as promoting integer
13949 constants to pointers.
13951 Range checking, if turned on, is done on mathematical operations. Array
13952 indices are not checked, since they are often used to index a pointer
13953 that is not itself an array.
13956 @subsubsection @value{GDBN} and C
13958 The @code{set print union} and @code{show print union} commands apply to
13959 the @code{union} type. When set to @samp{on}, any @code{union} that is
13960 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13961 appears as @samp{@{...@}}.
13963 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13964 with pointers and a memory allocation function. @xref{Expressions,
13967 @node Debugging C Plus Plus
13968 @subsubsection @value{GDBN} Features for C@t{++}
13970 @cindex commands for C@t{++}
13972 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13973 designed specifically for use with C@t{++}. Here is a summary:
13976 @cindex break in overloaded functions
13977 @item @r{breakpoint menus}
13978 When you want a breakpoint in a function whose name is overloaded,
13979 @value{GDBN} has the capability to display a menu of possible breakpoint
13980 locations to help you specify which function definition you want.
13981 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13983 @cindex overloading in C@t{++}
13984 @item rbreak @var{regex}
13985 Setting breakpoints using regular expressions is helpful for setting
13986 breakpoints on overloaded functions that are not members of any special
13988 @xref{Set Breaks, ,Setting Breakpoints}.
13990 @cindex C@t{++} exception handling
13992 @itemx catch rethrow
13994 Debug C@t{++} exception handling using these commands. @xref{Set
13995 Catchpoints, , Setting Catchpoints}.
13997 @cindex inheritance
13998 @item ptype @var{typename}
13999 Print inheritance relationships as well as other information for type
14001 @xref{Symbols, ,Examining the Symbol Table}.
14003 @item info vtbl @var{expression}.
14004 The @code{info vtbl} command can be used to display the virtual
14005 method tables of the object computed by @var{expression}. This shows
14006 one entry per virtual table; there may be multiple virtual tables when
14007 multiple inheritance is in use.
14009 @cindex C@t{++} symbol display
14010 @item set print demangle
14011 @itemx show print demangle
14012 @itemx set print asm-demangle
14013 @itemx show print asm-demangle
14014 Control whether C@t{++} symbols display in their source form, both when
14015 displaying code as C@t{++} source and when displaying disassemblies.
14016 @xref{Print Settings, ,Print Settings}.
14018 @item set print object
14019 @itemx show print object
14020 Choose whether to print derived (actual) or declared types of objects.
14021 @xref{Print Settings, ,Print Settings}.
14023 @item set print vtbl
14024 @itemx show print vtbl
14025 Control the format for printing virtual function tables.
14026 @xref{Print Settings, ,Print Settings}.
14027 (The @code{vtbl} commands do not work on programs compiled with the HP
14028 ANSI C@t{++} compiler (@code{aCC}).)
14030 @kindex set overload-resolution
14031 @cindex overloaded functions, overload resolution
14032 @item set overload-resolution on
14033 Enable overload resolution for C@t{++} expression evaluation. The default
14034 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14035 and searches for a function whose signature matches the argument types,
14036 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14037 Expressions, ,C@t{++} Expressions}, for details).
14038 If it cannot find a match, it emits a message.
14040 @item set overload-resolution off
14041 Disable overload resolution for C@t{++} expression evaluation. For
14042 overloaded functions that are not class member functions, @value{GDBN}
14043 chooses the first function of the specified name that it finds in the
14044 symbol table, whether or not its arguments are of the correct type. For
14045 overloaded functions that are class member functions, @value{GDBN}
14046 searches for a function whose signature @emph{exactly} matches the
14049 @kindex show overload-resolution
14050 @item show overload-resolution
14051 Show the current setting of overload resolution.
14053 @item @r{Overloaded symbol names}
14054 You can specify a particular definition of an overloaded symbol, using
14055 the same notation that is used to declare such symbols in C@t{++}: type
14056 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14057 also use the @value{GDBN} command-line word completion facilities to list the
14058 available choices, or to finish the type list for you.
14059 @xref{Completion,, Command Completion}, for details on how to do this.
14062 @node Decimal Floating Point
14063 @subsubsection Decimal Floating Point format
14064 @cindex decimal floating point format
14066 @value{GDBN} can examine, set and perform computations with numbers in
14067 decimal floating point format, which in the C language correspond to the
14068 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14069 specified by the extension to support decimal floating-point arithmetic.
14071 There are two encodings in use, depending on the architecture: BID (Binary
14072 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14073 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14076 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14077 to manipulate decimal floating point numbers, it is not possible to convert
14078 (using a cast, for example) integers wider than 32-bit to decimal float.
14080 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14081 point computations, error checking in decimal float operations ignores
14082 underflow, overflow and divide by zero exceptions.
14084 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14085 to inspect @code{_Decimal128} values stored in floating point registers.
14086 See @ref{PowerPC,,PowerPC} for more details.
14092 @value{GDBN} can be used to debug programs written in D and compiled with
14093 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14094 specific feature --- dynamic arrays.
14099 @cindex Go (programming language)
14100 @value{GDBN} can be used to debug programs written in Go and compiled with
14101 @file{gccgo} or @file{6g} compilers.
14103 Here is a summary of the Go-specific features and restrictions:
14106 @cindex current Go package
14107 @item The current Go package
14108 The name of the current package does not need to be specified when
14109 specifying global variables and functions.
14111 For example, given the program:
14115 var myglob = "Shall we?"
14121 When stopped inside @code{main} either of these work:
14125 (gdb) p main.myglob
14128 @cindex builtin Go types
14129 @item Builtin Go types
14130 The @code{string} type is recognized by @value{GDBN} and is printed
14133 @cindex builtin Go functions
14134 @item Builtin Go functions
14135 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14136 function and handles it internally.
14138 @cindex restrictions on Go expressions
14139 @item Restrictions on Go expressions
14140 All Go operators are supported except @code{&^}.
14141 The Go @code{_} ``blank identifier'' is not supported.
14142 Automatic dereferencing of pointers is not supported.
14146 @subsection Objective-C
14148 @cindex Objective-C
14149 This section provides information about some commands and command
14150 options that are useful for debugging Objective-C code. See also
14151 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14152 few more commands specific to Objective-C support.
14155 * Method Names in Commands::
14156 * The Print Command with Objective-C::
14159 @node Method Names in Commands
14160 @subsubsection Method Names in Commands
14162 The following commands have been extended to accept Objective-C method
14163 names as line specifications:
14165 @kindex clear@r{, and Objective-C}
14166 @kindex break@r{, and Objective-C}
14167 @kindex info line@r{, and Objective-C}
14168 @kindex jump@r{, and Objective-C}
14169 @kindex list@r{, and Objective-C}
14173 @item @code{info line}
14178 A fully qualified Objective-C method name is specified as
14181 -[@var{Class} @var{methodName}]
14184 where the minus sign is used to indicate an instance method and a
14185 plus sign (not shown) is used to indicate a class method. The class
14186 name @var{Class} and method name @var{methodName} are enclosed in
14187 brackets, similar to the way messages are specified in Objective-C
14188 source code. For example, to set a breakpoint at the @code{create}
14189 instance method of class @code{Fruit} in the program currently being
14193 break -[Fruit create]
14196 To list ten program lines around the @code{initialize} class method,
14200 list +[NSText initialize]
14203 In the current version of @value{GDBN}, the plus or minus sign is
14204 required. In future versions of @value{GDBN}, the plus or minus
14205 sign will be optional, but you can use it to narrow the search. It
14206 is also possible to specify just a method name:
14212 You must specify the complete method name, including any colons. If
14213 your program's source files contain more than one @code{create} method,
14214 you'll be presented with a numbered list of classes that implement that
14215 method. Indicate your choice by number, or type @samp{0} to exit if
14218 As another example, to clear a breakpoint established at the
14219 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14222 clear -[NSWindow makeKeyAndOrderFront:]
14225 @node The Print Command with Objective-C
14226 @subsubsection The Print Command With Objective-C
14227 @cindex Objective-C, print objects
14228 @kindex print-object
14229 @kindex po @r{(@code{print-object})}
14231 The print command has also been extended to accept methods. For example:
14234 print -[@var{object} hash]
14237 @cindex print an Objective-C object description
14238 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14240 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14241 and print the result. Also, an additional command has been added,
14242 @code{print-object} or @code{po} for short, which is meant to print
14243 the description of an object. However, this command may only work
14244 with certain Objective-C libraries that have a particular hook
14245 function, @code{_NSPrintForDebugger}, defined.
14248 @subsection OpenCL C
14251 This section provides information about @value{GDBN}s OpenCL C support.
14254 * OpenCL C Datatypes::
14255 * OpenCL C Expressions::
14256 * OpenCL C Operators::
14259 @node OpenCL C Datatypes
14260 @subsubsection OpenCL C Datatypes
14262 @cindex OpenCL C Datatypes
14263 @value{GDBN} supports the builtin scalar and vector datatypes specified
14264 by OpenCL 1.1. In addition the half- and double-precision floating point
14265 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14266 extensions are also known to @value{GDBN}.
14268 @node OpenCL C Expressions
14269 @subsubsection OpenCL C Expressions
14271 @cindex OpenCL C Expressions
14272 @value{GDBN} supports accesses to vector components including the access as
14273 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14274 supported by @value{GDBN} can be used as well.
14276 @node OpenCL C Operators
14277 @subsubsection OpenCL C Operators
14279 @cindex OpenCL C Operators
14280 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14284 @subsection Fortran
14285 @cindex Fortran-specific support in @value{GDBN}
14287 @value{GDBN} can be used to debug programs written in Fortran, but it
14288 currently supports only the features of Fortran 77 language.
14290 @cindex trailing underscore, in Fortran symbols
14291 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14292 among them) append an underscore to the names of variables and
14293 functions. When you debug programs compiled by those compilers, you
14294 will need to refer to variables and functions with a trailing
14298 * Fortran Operators:: Fortran operators and expressions
14299 * Fortran Defaults:: Default settings for Fortran
14300 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14303 @node Fortran Operators
14304 @subsubsection Fortran Operators and Expressions
14306 @cindex Fortran operators and expressions
14308 Operators must be defined on values of specific types. For instance,
14309 @code{+} is defined on numbers, but not on characters or other non-
14310 arithmetic types. Operators are often defined on groups of types.
14314 The exponentiation operator. It raises the first operand to the power
14318 The range operator. Normally used in the form of array(low:high) to
14319 represent a section of array.
14322 The access component operator. Normally used to access elements in derived
14323 types. Also suitable for unions. As unions aren't part of regular Fortran,
14324 this can only happen when accessing a register that uses a gdbarch-defined
14328 @node Fortran Defaults
14329 @subsubsection Fortran Defaults
14331 @cindex Fortran Defaults
14333 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14334 default uses case-insensitive matches for Fortran symbols. You can
14335 change that with the @samp{set case-insensitive} command, see
14336 @ref{Symbols}, for the details.
14338 @node Special Fortran Commands
14339 @subsubsection Special Fortran Commands
14341 @cindex Special Fortran commands
14343 @value{GDBN} has some commands to support Fortran-specific features,
14344 such as displaying common blocks.
14347 @cindex @code{COMMON} blocks, Fortran
14348 @kindex info common
14349 @item info common @r{[}@var{common-name}@r{]}
14350 This command prints the values contained in the Fortran @code{COMMON}
14351 block whose name is @var{common-name}. With no argument, the names of
14352 all @code{COMMON} blocks visible at the current program location are
14359 @cindex Pascal support in @value{GDBN}, limitations
14360 Debugging Pascal programs which use sets, subranges, file variables, or
14361 nested functions does not currently work. @value{GDBN} does not support
14362 entering expressions, printing values, or similar features using Pascal
14365 The Pascal-specific command @code{set print pascal_static-members}
14366 controls whether static members of Pascal objects are displayed.
14367 @xref{Print Settings, pascal_static-members}.
14370 @subsection Modula-2
14372 @cindex Modula-2, @value{GDBN} support
14374 The extensions made to @value{GDBN} to support Modula-2 only support
14375 output from the @sc{gnu} Modula-2 compiler (which is currently being
14376 developed). Other Modula-2 compilers are not currently supported, and
14377 attempting to debug executables produced by them is most likely
14378 to give an error as @value{GDBN} reads in the executable's symbol
14381 @cindex expressions in Modula-2
14383 * M2 Operators:: Built-in operators
14384 * Built-In Func/Proc:: Built-in functions and procedures
14385 * M2 Constants:: Modula-2 constants
14386 * M2 Types:: Modula-2 types
14387 * M2 Defaults:: Default settings for Modula-2
14388 * Deviations:: Deviations from standard Modula-2
14389 * M2 Checks:: Modula-2 type and range checks
14390 * M2 Scope:: The scope operators @code{::} and @code{.}
14391 * GDB/M2:: @value{GDBN} and Modula-2
14395 @subsubsection Operators
14396 @cindex Modula-2 operators
14398 Operators must be defined on values of specific types. For instance,
14399 @code{+} is defined on numbers, but not on structures. Operators are
14400 often defined on groups of types. For the purposes of Modula-2, the
14401 following definitions hold:
14406 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14410 @emph{Character types} consist of @code{CHAR} and its subranges.
14413 @emph{Floating-point types} consist of @code{REAL}.
14416 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14420 @emph{Scalar types} consist of all of the above.
14423 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14426 @emph{Boolean types} consist of @code{BOOLEAN}.
14430 The following operators are supported, and appear in order of
14431 increasing precedence:
14435 Function argument or array index separator.
14438 Assignment. The value of @var{var} @code{:=} @var{value} is
14442 Less than, greater than on integral, floating-point, or enumerated
14446 Less than or equal to, greater than or equal to
14447 on integral, floating-point and enumerated types, or set inclusion on
14448 set types. Same precedence as @code{<}.
14450 @item =@r{, }<>@r{, }#
14451 Equality and two ways of expressing inequality, valid on scalar types.
14452 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14453 available for inequality, since @code{#} conflicts with the script
14457 Set membership. Defined on set types and the types of their members.
14458 Same precedence as @code{<}.
14461 Boolean disjunction. Defined on boolean types.
14464 Boolean conjunction. Defined on boolean types.
14467 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14470 Addition and subtraction on integral and floating-point types, or union
14471 and difference on set types.
14474 Multiplication on integral and floating-point types, or set intersection
14478 Division on floating-point types, or symmetric set difference on set
14479 types. Same precedence as @code{*}.
14482 Integer division and remainder. Defined on integral types. Same
14483 precedence as @code{*}.
14486 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14489 Pointer dereferencing. Defined on pointer types.
14492 Boolean negation. Defined on boolean types. Same precedence as
14496 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14497 precedence as @code{^}.
14500 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14503 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14507 @value{GDBN} and Modula-2 scope operators.
14511 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14512 treats the use of the operator @code{IN}, or the use of operators
14513 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14514 @code{<=}, and @code{>=} on sets as an error.
14518 @node Built-In Func/Proc
14519 @subsubsection Built-in Functions and Procedures
14520 @cindex Modula-2 built-ins
14522 Modula-2 also makes available several built-in procedures and functions.
14523 In describing these, the following metavariables are used:
14528 represents an @code{ARRAY} variable.
14531 represents a @code{CHAR} constant or variable.
14534 represents a variable or constant of integral type.
14537 represents an identifier that belongs to a set. Generally used in the
14538 same function with the metavariable @var{s}. The type of @var{s} should
14539 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14542 represents a variable or constant of integral or floating-point type.
14545 represents a variable or constant of floating-point type.
14551 represents a variable.
14554 represents a variable or constant of one of many types. See the
14555 explanation of the function for details.
14558 All Modula-2 built-in procedures also return a result, described below.
14562 Returns the absolute value of @var{n}.
14565 If @var{c} is a lower case letter, it returns its upper case
14566 equivalent, otherwise it returns its argument.
14569 Returns the character whose ordinal value is @var{i}.
14572 Decrements the value in the variable @var{v} by one. Returns the new value.
14574 @item DEC(@var{v},@var{i})
14575 Decrements the value in the variable @var{v} by @var{i}. Returns the
14578 @item EXCL(@var{m},@var{s})
14579 Removes the element @var{m} from the set @var{s}. Returns the new
14582 @item FLOAT(@var{i})
14583 Returns the floating point equivalent of the integer @var{i}.
14585 @item HIGH(@var{a})
14586 Returns the index of the last member of @var{a}.
14589 Increments the value in the variable @var{v} by one. Returns the new value.
14591 @item INC(@var{v},@var{i})
14592 Increments the value in the variable @var{v} by @var{i}. Returns the
14595 @item INCL(@var{m},@var{s})
14596 Adds the element @var{m} to the set @var{s} if it is not already
14597 there. Returns the new set.
14600 Returns the maximum value of the type @var{t}.
14603 Returns the minimum value of the type @var{t}.
14606 Returns boolean TRUE if @var{i} is an odd number.
14609 Returns the ordinal value of its argument. For example, the ordinal
14610 value of a character is its @sc{ascii} value (on machines supporting the
14611 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14612 integral, character and enumerated types.
14614 @item SIZE(@var{x})
14615 Returns the size of its argument. @var{x} can be a variable or a type.
14617 @item TRUNC(@var{r})
14618 Returns the integral part of @var{r}.
14620 @item TSIZE(@var{x})
14621 Returns the size of its argument. @var{x} can be a variable or a type.
14623 @item VAL(@var{t},@var{i})
14624 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14628 @emph{Warning:} Sets and their operations are not yet supported, so
14629 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14633 @cindex Modula-2 constants
14635 @subsubsection Constants
14637 @value{GDBN} allows you to express the constants of Modula-2 in the following
14643 Integer constants are simply a sequence of digits. When used in an
14644 expression, a constant is interpreted to be type-compatible with the
14645 rest of the expression. Hexadecimal integers are specified by a
14646 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14649 Floating point constants appear as a sequence of digits, followed by a
14650 decimal point and another sequence of digits. An optional exponent can
14651 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14652 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14653 digits of the floating point constant must be valid decimal (base 10)
14657 Character constants consist of a single character enclosed by a pair of
14658 like quotes, either single (@code{'}) or double (@code{"}). They may
14659 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14660 followed by a @samp{C}.
14663 String constants consist of a sequence of characters enclosed by a
14664 pair of like quotes, either single (@code{'}) or double (@code{"}).
14665 Escape sequences in the style of C are also allowed. @xref{C
14666 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14670 Enumerated constants consist of an enumerated identifier.
14673 Boolean constants consist of the identifiers @code{TRUE} and
14677 Pointer constants consist of integral values only.
14680 Set constants are not yet supported.
14684 @subsubsection Modula-2 Types
14685 @cindex Modula-2 types
14687 Currently @value{GDBN} can print the following data types in Modula-2
14688 syntax: array types, record types, set types, pointer types, procedure
14689 types, enumerated types, subrange types and base types. You can also
14690 print the contents of variables declared using these type.
14691 This section gives a number of simple source code examples together with
14692 sample @value{GDBN} sessions.
14694 The first example contains the following section of code:
14703 and you can request @value{GDBN} to interrogate the type and value of
14704 @code{r} and @code{s}.
14707 (@value{GDBP}) print s
14709 (@value{GDBP}) ptype s
14711 (@value{GDBP}) print r
14713 (@value{GDBP}) ptype r
14718 Likewise if your source code declares @code{s} as:
14722 s: SET ['A'..'Z'] ;
14726 then you may query the type of @code{s} by:
14729 (@value{GDBP}) ptype s
14730 type = SET ['A'..'Z']
14734 Note that at present you cannot interactively manipulate set
14735 expressions using the debugger.
14737 The following example shows how you might declare an array in Modula-2
14738 and how you can interact with @value{GDBN} to print its type and contents:
14742 s: ARRAY [-10..10] OF CHAR ;
14746 (@value{GDBP}) ptype s
14747 ARRAY [-10..10] OF CHAR
14750 Note that the array handling is not yet complete and although the type
14751 is printed correctly, expression handling still assumes that all
14752 arrays have a lower bound of zero and not @code{-10} as in the example
14755 Here are some more type related Modula-2 examples:
14759 colour = (blue, red, yellow, green) ;
14760 t = [blue..yellow] ;
14768 The @value{GDBN} interaction shows how you can query the data type
14769 and value of a variable.
14772 (@value{GDBP}) print s
14774 (@value{GDBP}) ptype t
14775 type = [blue..yellow]
14779 In this example a Modula-2 array is declared and its contents
14780 displayed. Observe that the contents are written in the same way as
14781 their @code{C} counterparts.
14785 s: ARRAY [1..5] OF CARDINAL ;
14791 (@value{GDBP}) print s
14792 $1 = @{1, 0, 0, 0, 0@}
14793 (@value{GDBP}) ptype s
14794 type = ARRAY [1..5] OF CARDINAL
14797 The Modula-2 language interface to @value{GDBN} also understands
14798 pointer types as shown in this example:
14802 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14809 and you can request that @value{GDBN} describes the type of @code{s}.
14812 (@value{GDBP}) ptype s
14813 type = POINTER TO ARRAY [1..5] OF CARDINAL
14816 @value{GDBN} handles compound types as we can see in this example.
14817 Here we combine array types, record types, pointer types and subrange
14828 myarray = ARRAY myrange OF CARDINAL ;
14829 myrange = [-2..2] ;
14831 s: POINTER TO ARRAY myrange OF foo ;
14835 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14839 (@value{GDBP}) ptype s
14840 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14843 f3 : ARRAY [-2..2] OF CARDINAL;
14848 @subsubsection Modula-2 Defaults
14849 @cindex Modula-2 defaults
14851 If type and range checking are set automatically by @value{GDBN}, they
14852 both default to @code{on} whenever the working language changes to
14853 Modula-2. This happens regardless of whether you or @value{GDBN}
14854 selected the working language.
14856 If you allow @value{GDBN} to set the language automatically, then entering
14857 code compiled from a file whose name ends with @file{.mod} sets the
14858 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14859 Infer the Source Language}, for further details.
14862 @subsubsection Deviations from Standard Modula-2
14863 @cindex Modula-2, deviations from
14865 A few changes have been made to make Modula-2 programs easier to debug.
14866 This is done primarily via loosening its type strictness:
14870 Unlike in standard Modula-2, pointer constants can be formed by
14871 integers. This allows you to modify pointer variables during
14872 debugging. (In standard Modula-2, the actual address contained in a
14873 pointer variable is hidden from you; it can only be modified
14874 through direct assignment to another pointer variable or expression that
14875 returned a pointer.)
14878 C escape sequences can be used in strings and characters to represent
14879 non-printable characters. @value{GDBN} prints out strings with these
14880 escape sequences embedded. Single non-printable characters are
14881 printed using the @samp{CHR(@var{nnn})} format.
14884 The assignment operator (@code{:=}) returns the value of its right-hand
14888 All built-in procedures both modify @emph{and} return their argument.
14892 @subsubsection Modula-2 Type and Range Checks
14893 @cindex Modula-2 checks
14896 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14899 @c FIXME remove warning when type/range checks added
14901 @value{GDBN} considers two Modula-2 variables type equivalent if:
14905 They are of types that have been declared equivalent via a @code{TYPE
14906 @var{t1} = @var{t2}} statement
14909 They have been declared on the same line. (Note: This is true of the
14910 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14913 As long as type checking is enabled, any attempt to combine variables
14914 whose types are not equivalent is an error.
14916 Range checking is done on all mathematical operations, assignment, array
14917 index bounds, and all built-in functions and procedures.
14920 @subsubsection The Scope Operators @code{::} and @code{.}
14922 @cindex @code{.}, Modula-2 scope operator
14923 @cindex colon, doubled as scope operator
14925 @vindex colon-colon@r{, in Modula-2}
14926 @c Info cannot handle :: but TeX can.
14929 @vindex ::@r{, in Modula-2}
14932 There are a few subtle differences between the Modula-2 scope operator
14933 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14938 @var{module} . @var{id}
14939 @var{scope} :: @var{id}
14943 where @var{scope} is the name of a module or a procedure,
14944 @var{module} the name of a module, and @var{id} is any declared
14945 identifier within your program, except another module.
14947 Using the @code{::} operator makes @value{GDBN} search the scope
14948 specified by @var{scope} for the identifier @var{id}. If it is not
14949 found in the specified scope, then @value{GDBN} searches all scopes
14950 enclosing the one specified by @var{scope}.
14952 Using the @code{.} operator makes @value{GDBN} search the current scope for
14953 the identifier specified by @var{id} that was imported from the
14954 definition module specified by @var{module}. With this operator, it is
14955 an error if the identifier @var{id} was not imported from definition
14956 module @var{module}, or if @var{id} is not an identifier in
14960 @subsubsection @value{GDBN} and Modula-2
14962 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14963 Five subcommands of @code{set print} and @code{show print} apply
14964 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14965 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14966 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14967 analogue in Modula-2.
14969 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14970 with any language, is not useful with Modula-2. Its
14971 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14972 created in Modula-2 as they can in C or C@t{++}. However, because an
14973 address can be specified by an integral constant, the construct
14974 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14976 @cindex @code{#} in Modula-2
14977 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14978 interpreted as the beginning of a comment. Use @code{<>} instead.
14984 The extensions made to @value{GDBN} for Ada only support
14985 output from the @sc{gnu} Ada (GNAT) compiler.
14986 Other Ada compilers are not currently supported, and
14987 attempting to debug executables produced by them is most likely
14991 @cindex expressions in Ada
14993 * Ada Mode Intro:: General remarks on the Ada syntax
14994 and semantics supported by Ada mode
14996 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14997 * Additions to Ada:: Extensions of the Ada expression syntax.
14998 * Stopping Before Main Program:: Debugging the program during elaboration.
14999 * Ada Exceptions:: Ada Exceptions
15000 * Ada Tasks:: Listing and setting breakpoints in tasks.
15001 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15002 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15004 * Ada Glitches:: Known peculiarities of Ada mode.
15007 @node Ada Mode Intro
15008 @subsubsection Introduction
15009 @cindex Ada mode, general
15011 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15012 syntax, with some extensions.
15013 The philosophy behind the design of this subset is
15017 That @value{GDBN} should provide basic literals and access to operations for
15018 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15019 leaving more sophisticated computations to subprograms written into the
15020 program (which therefore may be called from @value{GDBN}).
15023 That type safety and strict adherence to Ada language restrictions
15024 are not particularly important to the @value{GDBN} user.
15027 That brevity is important to the @value{GDBN} user.
15030 Thus, for brevity, the debugger acts as if all names declared in
15031 user-written packages are directly visible, even if they are not visible
15032 according to Ada rules, thus making it unnecessary to fully qualify most
15033 names with their packages, regardless of context. Where this causes
15034 ambiguity, @value{GDBN} asks the user's intent.
15036 The debugger will start in Ada mode if it detects an Ada main program.
15037 As for other languages, it will enter Ada mode when stopped in a program that
15038 was translated from an Ada source file.
15040 While in Ada mode, you may use `@t{--}' for comments. This is useful
15041 mostly for documenting command files. The standard @value{GDBN} comment
15042 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15043 middle (to allow based literals).
15045 The debugger supports limited overloading. Given a subprogram call in which
15046 the function symbol has multiple definitions, it will use the number of
15047 actual parameters and some information about their types to attempt to narrow
15048 the set of definitions. It also makes very limited use of context, preferring
15049 procedures to functions in the context of the @code{call} command, and
15050 functions to procedures elsewhere.
15052 @node Omissions from Ada
15053 @subsubsection Omissions from Ada
15054 @cindex Ada, omissions from
15056 Here are the notable omissions from the subset:
15060 Only a subset of the attributes are supported:
15064 @t{'First}, @t{'Last}, and @t{'Length}
15065 on array objects (not on types and subtypes).
15068 @t{'Min} and @t{'Max}.
15071 @t{'Pos} and @t{'Val}.
15077 @t{'Range} on array objects (not subtypes), but only as the right
15078 operand of the membership (@code{in}) operator.
15081 @t{'Access}, @t{'Unchecked_Access}, and
15082 @t{'Unrestricted_Access} (a GNAT extension).
15090 @code{Characters.Latin_1} are not available and
15091 concatenation is not implemented. Thus, escape characters in strings are
15092 not currently available.
15095 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15096 equality of representations. They will generally work correctly
15097 for strings and arrays whose elements have integer or enumeration types.
15098 They may not work correctly for arrays whose element
15099 types have user-defined equality, for arrays of real values
15100 (in particular, IEEE-conformant floating point, because of negative
15101 zeroes and NaNs), and for arrays whose elements contain unused bits with
15102 indeterminate values.
15105 The other component-by-component array operations (@code{and}, @code{or},
15106 @code{xor}, @code{not}, and relational tests other than equality)
15107 are not implemented.
15110 @cindex array aggregates (Ada)
15111 @cindex record aggregates (Ada)
15112 @cindex aggregates (Ada)
15113 There is limited support for array and record aggregates. They are
15114 permitted only on the right sides of assignments, as in these examples:
15117 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15118 (@value{GDBP}) set An_Array := (1, others => 0)
15119 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15120 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15121 (@value{GDBP}) set A_Record := (1, "Peter", True);
15122 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15126 discriminant's value by assigning an aggregate has an
15127 undefined effect if that discriminant is used within the record.
15128 However, you can first modify discriminants by directly assigning to
15129 them (which normally would not be allowed in Ada), and then performing an
15130 aggregate assignment. For example, given a variable @code{A_Rec}
15131 declared to have a type such as:
15134 type Rec (Len : Small_Integer := 0) is record
15136 Vals : IntArray (1 .. Len);
15140 you can assign a value with a different size of @code{Vals} with two
15144 (@value{GDBP}) set A_Rec.Len := 4
15145 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15148 As this example also illustrates, @value{GDBN} is very loose about the usual
15149 rules concerning aggregates. You may leave out some of the
15150 components of an array or record aggregate (such as the @code{Len}
15151 component in the assignment to @code{A_Rec} above); they will retain their
15152 original values upon assignment. You may freely use dynamic values as
15153 indices in component associations. You may even use overlapping or
15154 redundant component associations, although which component values are
15155 assigned in such cases is not defined.
15158 Calls to dispatching subprograms are not implemented.
15161 The overloading algorithm is much more limited (i.e., less selective)
15162 than that of real Ada. It makes only limited use of the context in
15163 which a subexpression appears to resolve its meaning, and it is much
15164 looser in its rules for allowing type matches. As a result, some
15165 function calls will be ambiguous, and the user will be asked to choose
15166 the proper resolution.
15169 The @code{new} operator is not implemented.
15172 Entry calls are not implemented.
15175 Aside from printing, arithmetic operations on the native VAX floating-point
15176 formats are not supported.
15179 It is not possible to slice a packed array.
15182 The names @code{True} and @code{False}, when not part of a qualified name,
15183 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15185 Should your program
15186 redefine these names in a package or procedure (at best a dubious practice),
15187 you will have to use fully qualified names to access their new definitions.
15190 @node Additions to Ada
15191 @subsubsection Additions to Ada
15192 @cindex Ada, deviations from
15194 As it does for other languages, @value{GDBN} makes certain generic
15195 extensions to Ada (@pxref{Expressions}):
15199 If the expression @var{E} is a variable residing in memory (typically
15200 a local variable or array element) and @var{N} is a positive integer,
15201 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15202 @var{N}-1 adjacent variables following it in memory as an array. In
15203 Ada, this operator is generally not necessary, since its prime use is
15204 in displaying parts of an array, and slicing will usually do this in
15205 Ada. However, there are occasional uses when debugging programs in
15206 which certain debugging information has been optimized away.
15209 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15210 appears in function or file @var{B}.'' When @var{B} is a file name,
15211 you must typically surround it in single quotes.
15214 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15215 @var{type} that appears at address @var{addr}.''
15218 A name starting with @samp{$} is a convenience variable
15219 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15222 In addition, @value{GDBN} provides a few other shortcuts and outright
15223 additions specific to Ada:
15227 The assignment statement is allowed as an expression, returning
15228 its right-hand operand as its value. Thus, you may enter
15231 (@value{GDBP}) set x := y + 3
15232 (@value{GDBP}) print A(tmp := y + 1)
15236 The semicolon is allowed as an ``operator,'' returning as its value
15237 the value of its right-hand operand.
15238 This allows, for example,
15239 complex conditional breaks:
15242 (@value{GDBP}) break f
15243 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15247 Rather than use catenation and symbolic character names to introduce special
15248 characters into strings, one may instead use a special bracket notation,
15249 which is also used to print strings. A sequence of characters of the form
15250 @samp{["@var{XX}"]} within a string or character literal denotes the
15251 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15252 sequence of characters @samp{["""]} also denotes a single quotation mark
15253 in strings. For example,
15255 "One line.["0a"]Next line.["0a"]"
15258 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15262 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15263 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15267 (@value{GDBP}) print 'max(x, y)
15271 When printing arrays, @value{GDBN} uses positional notation when the
15272 array has a lower bound of 1, and uses a modified named notation otherwise.
15273 For example, a one-dimensional array of three integers with a lower bound
15274 of 3 might print as
15281 That is, in contrast to valid Ada, only the first component has a @code{=>}
15285 You may abbreviate attributes in expressions with any unique,
15286 multi-character subsequence of
15287 their names (an exact match gets preference).
15288 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15289 in place of @t{a'length}.
15292 @cindex quoting Ada internal identifiers
15293 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15294 to lower case. The GNAT compiler uses upper-case characters for
15295 some of its internal identifiers, which are normally of no interest to users.
15296 For the rare occasions when you actually have to look at them,
15297 enclose them in angle brackets to avoid the lower-case mapping.
15300 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15304 Printing an object of class-wide type or dereferencing an
15305 access-to-class-wide value will display all the components of the object's
15306 specific type (as indicated by its run-time tag). Likewise, component
15307 selection on such a value will operate on the specific type of the
15312 @node Stopping Before Main Program
15313 @subsubsection Stopping at the Very Beginning
15315 @cindex breakpointing Ada elaboration code
15316 It is sometimes necessary to debug the program during elaboration, and
15317 before reaching the main procedure.
15318 As defined in the Ada Reference
15319 Manual, the elaboration code is invoked from a procedure called
15320 @code{adainit}. To run your program up to the beginning of
15321 elaboration, simply use the following two commands:
15322 @code{tbreak adainit} and @code{run}.
15324 @node Ada Exceptions
15325 @subsubsection Ada Exceptions
15327 A command is provided to list all Ada exceptions:
15330 @kindex info exceptions
15331 @item info exceptions
15332 @itemx info exceptions @var{regexp}
15333 The @code{info exceptions} command allows you to list all Ada exceptions
15334 defined within the program being debugged, as well as their addresses.
15335 With a regular expression, @var{regexp}, as argument, only those exceptions
15336 whose names match @var{regexp} are listed.
15339 Below is a small example, showing how the command can be used, first
15340 without argument, and next with a regular expression passed as an
15344 (@value{GDBP}) info exceptions
15345 All defined Ada exceptions:
15346 constraint_error: 0x613da0
15347 program_error: 0x613d20
15348 storage_error: 0x613ce0
15349 tasking_error: 0x613ca0
15350 const.aint_global_e: 0x613b00
15351 (@value{GDBP}) info exceptions const.aint
15352 All Ada exceptions matching regular expression "const.aint":
15353 constraint_error: 0x613da0
15354 const.aint_global_e: 0x613b00
15357 It is also possible to ask @value{GDBN} to stop your program's execution
15358 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15361 @subsubsection Extensions for Ada Tasks
15362 @cindex Ada, tasking
15364 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15365 @value{GDBN} provides the following task-related commands:
15370 This command shows a list of current Ada tasks, as in the following example:
15377 (@value{GDBP}) info tasks
15378 ID TID P-ID Pri State Name
15379 1 8088000 0 15 Child Activation Wait main_task
15380 2 80a4000 1 15 Accept Statement b
15381 3 809a800 1 15 Child Activation Wait a
15382 * 4 80ae800 3 15 Runnable c
15387 In this listing, the asterisk before the last task indicates it to be the
15388 task currently being inspected.
15392 Represents @value{GDBN}'s internal task number.
15398 The parent's task ID (@value{GDBN}'s internal task number).
15401 The base priority of the task.
15404 Current state of the task.
15408 The task has been created but has not been activated. It cannot be
15412 The task is not blocked for any reason known to Ada. (It may be waiting
15413 for a mutex, though.) It is conceptually "executing" in normal mode.
15416 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15417 that were waiting on terminate alternatives have been awakened and have
15418 terminated themselves.
15420 @item Child Activation Wait
15421 The task is waiting for created tasks to complete activation.
15423 @item Accept Statement
15424 The task is waiting on an accept or selective wait statement.
15426 @item Waiting on entry call
15427 The task is waiting on an entry call.
15429 @item Async Select Wait
15430 The task is waiting to start the abortable part of an asynchronous
15434 The task is waiting on a select statement with only a delay
15437 @item Child Termination Wait
15438 The task is sleeping having completed a master within itself, and is
15439 waiting for the tasks dependent on that master to become terminated or
15440 waiting on a terminate Phase.
15442 @item Wait Child in Term Alt
15443 The task is sleeping waiting for tasks on terminate alternatives to
15444 finish terminating.
15446 @item Accepting RV with @var{taskno}
15447 The task is accepting a rendez-vous with the task @var{taskno}.
15451 Name of the task in the program.
15455 @kindex info task @var{taskno}
15456 @item info task @var{taskno}
15457 This command shows detailled informations on the specified task, as in
15458 the following example:
15463 (@value{GDBP}) info tasks
15464 ID TID P-ID Pri State Name
15465 1 8077880 0 15 Child Activation Wait main_task
15466 * 2 807c468 1 15 Runnable task_1
15467 (@value{GDBP}) info task 2
15468 Ada Task: 0x807c468
15471 Parent: 1 (main_task)
15477 @kindex task@r{ (Ada)}
15478 @cindex current Ada task ID
15479 This command prints the ID of the current task.
15485 (@value{GDBP}) info tasks
15486 ID TID P-ID Pri State Name
15487 1 8077870 0 15 Child Activation Wait main_task
15488 * 2 807c458 1 15 Runnable t
15489 (@value{GDBP}) task
15490 [Current task is 2]
15493 @item task @var{taskno}
15494 @cindex Ada task switching
15495 This command is like the @code{thread @var{threadno}}
15496 command (@pxref{Threads}). It switches the context of debugging
15497 from the current task to the given task.
15503 (@value{GDBP}) info tasks
15504 ID TID P-ID Pri State Name
15505 1 8077870 0 15 Child Activation Wait main_task
15506 * 2 807c458 1 15 Runnable t
15507 (@value{GDBP}) task 1
15508 [Switching to task 1]
15509 #0 0x8067726 in pthread_cond_wait ()
15511 #0 0x8067726 in pthread_cond_wait ()
15512 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15513 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15514 #3 0x806153e in system.tasking.stages.activate_tasks ()
15515 #4 0x804aacc in un () at un.adb:5
15518 @item break @var{linespec} task @var{taskno}
15519 @itemx break @var{linespec} task @var{taskno} if @dots{}
15520 @cindex breakpoints and tasks, in Ada
15521 @cindex task breakpoints, in Ada
15522 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15523 These commands are like the @code{break @dots{} thread @dots{}}
15524 command (@pxref{Thread Stops}).
15525 @var{linespec} specifies source lines, as described
15526 in @ref{Specify Location}.
15528 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15529 to specify that you only want @value{GDBN} to stop the program when a
15530 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15531 numeric task identifiers assigned by @value{GDBN}, shown in the first
15532 column of the @samp{info tasks} display.
15534 If you do not specify @samp{task @var{taskno}} when you set a
15535 breakpoint, the breakpoint applies to @emph{all} tasks of your
15538 You can use the @code{task} qualifier on conditional breakpoints as
15539 well; in this case, place @samp{task @var{taskno}} before the
15540 breakpoint condition (before the @code{if}).
15548 (@value{GDBP}) info tasks
15549 ID TID P-ID Pri State Name
15550 1 140022020 0 15 Child Activation Wait main_task
15551 2 140045060 1 15 Accept/Select Wait t2
15552 3 140044840 1 15 Runnable t1
15553 * 4 140056040 1 15 Runnable t3
15554 (@value{GDBP}) b 15 task 2
15555 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15556 (@value{GDBP}) cont
15561 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15563 (@value{GDBP}) info tasks
15564 ID TID P-ID Pri State Name
15565 1 140022020 0 15 Child Activation Wait main_task
15566 * 2 140045060 1 15 Runnable t2
15567 3 140044840 1 15 Runnable t1
15568 4 140056040 1 15 Delay Sleep t3
15572 @node Ada Tasks and Core Files
15573 @subsubsection Tasking Support when Debugging Core Files
15574 @cindex Ada tasking and core file debugging
15576 When inspecting a core file, as opposed to debugging a live program,
15577 tasking support may be limited or even unavailable, depending on
15578 the platform being used.
15579 For instance, on x86-linux, the list of tasks is available, but task
15580 switching is not supported. On Tru64, however, task switching will work
15583 On certain platforms, including Tru64, the debugger needs to perform some
15584 memory writes in order to provide Ada tasking support. When inspecting
15585 a core file, this means that the core file must be opened with read-write
15586 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15587 Under these circumstances, you should make a backup copy of the core
15588 file before inspecting it with @value{GDBN}.
15590 @node Ravenscar Profile
15591 @subsubsection Tasking Support when using the Ravenscar Profile
15592 @cindex Ravenscar Profile
15594 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15595 specifically designed for systems with safety-critical real-time
15599 @kindex set ravenscar task-switching on
15600 @cindex task switching with program using Ravenscar Profile
15601 @item set ravenscar task-switching on
15602 Allows task switching when debugging a program that uses the Ravenscar
15603 Profile. This is the default.
15605 @kindex set ravenscar task-switching off
15606 @item set ravenscar task-switching off
15607 Turn off task switching when debugging a program that uses the Ravenscar
15608 Profile. This is mostly intended to disable the code that adds support
15609 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15610 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15611 To be effective, this command should be run before the program is started.
15613 @kindex show ravenscar task-switching
15614 @item show ravenscar task-switching
15615 Show whether it is possible to switch from task to task in a program
15616 using the Ravenscar Profile.
15621 @subsubsection Known Peculiarities of Ada Mode
15622 @cindex Ada, problems
15624 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15625 we know of several problems with and limitations of Ada mode in
15627 some of which will be fixed with planned future releases of the debugger
15628 and the GNU Ada compiler.
15632 Static constants that the compiler chooses not to materialize as objects in
15633 storage are invisible to the debugger.
15636 Named parameter associations in function argument lists are ignored (the
15637 argument lists are treated as positional).
15640 Many useful library packages are currently invisible to the debugger.
15643 Fixed-point arithmetic, conversions, input, and output is carried out using
15644 floating-point arithmetic, and may give results that only approximate those on
15648 The GNAT compiler never generates the prefix @code{Standard} for any of
15649 the standard symbols defined by the Ada language. @value{GDBN} knows about
15650 this: it will strip the prefix from names when you use it, and will never
15651 look for a name you have so qualified among local symbols, nor match against
15652 symbols in other packages or subprograms. If you have
15653 defined entities anywhere in your program other than parameters and
15654 local variables whose simple names match names in @code{Standard},
15655 GNAT's lack of qualification here can cause confusion. When this happens,
15656 you can usually resolve the confusion
15657 by qualifying the problematic names with package
15658 @code{Standard} explicitly.
15661 Older versions of the compiler sometimes generate erroneous debugging
15662 information, resulting in the debugger incorrectly printing the value
15663 of affected entities. In some cases, the debugger is able to work
15664 around an issue automatically. In other cases, the debugger is able
15665 to work around the issue, but the work-around has to be specifically
15668 @kindex set ada trust-PAD-over-XVS
15669 @kindex show ada trust-PAD-over-XVS
15672 @item set ada trust-PAD-over-XVS on
15673 Configure GDB to strictly follow the GNAT encoding when computing the
15674 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15675 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15676 a complete description of the encoding used by the GNAT compiler).
15677 This is the default.
15679 @item set ada trust-PAD-over-XVS off
15680 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15681 sometimes prints the wrong value for certain entities, changing @code{ada
15682 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15683 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15684 @code{off}, but this incurs a slight performance penalty, so it is
15685 recommended to leave this setting to @code{on} unless necessary.
15689 @node Unsupported Languages
15690 @section Unsupported Languages
15692 @cindex unsupported languages
15693 @cindex minimal language
15694 In addition to the other fully-supported programming languages,
15695 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15696 It does not represent a real programming language, but provides a set
15697 of capabilities close to what the C or assembly languages provide.
15698 This should allow most simple operations to be performed while debugging
15699 an application that uses a language currently not supported by @value{GDBN}.
15701 If the language is set to @code{auto}, @value{GDBN} will automatically
15702 select this language if the current frame corresponds to an unsupported
15706 @chapter Examining the Symbol Table
15708 The commands described in this chapter allow you to inquire about the
15709 symbols (names of variables, functions and types) defined in your
15710 program. This information is inherent in the text of your program and
15711 does not change as your program executes. @value{GDBN} finds it in your
15712 program's symbol table, in the file indicated when you started @value{GDBN}
15713 (@pxref{File Options, ,Choosing Files}), or by one of the
15714 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15716 @cindex symbol names
15717 @cindex names of symbols
15718 @cindex quoting names
15719 Occasionally, you may need to refer to symbols that contain unusual
15720 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15721 most frequent case is in referring to static variables in other
15722 source files (@pxref{Variables,,Program Variables}). File names
15723 are recorded in object files as debugging symbols, but @value{GDBN} would
15724 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15725 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15726 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15733 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15736 @cindex case-insensitive symbol names
15737 @cindex case sensitivity in symbol names
15738 @kindex set case-sensitive
15739 @item set case-sensitive on
15740 @itemx set case-sensitive off
15741 @itemx set case-sensitive auto
15742 Normally, when @value{GDBN} looks up symbols, it matches their names
15743 with case sensitivity determined by the current source language.
15744 Occasionally, you may wish to control that. The command @code{set
15745 case-sensitive} lets you do that by specifying @code{on} for
15746 case-sensitive matches or @code{off} for case-insensitive ones. If
15747 you specify @code{auto}, case sensitivity is reset to the default
15748 suitable for the source language. The default is case-sensitive
15749 matches for all languages except for Fortran, for which the default is
15750 case-insensitive matches.
15752 @kindex show case-sensitive
15753 @item show case-sensitive
15754 This command shows the current setting of case sensitivity for symbols
15757 @kindex set print type methods
15758 @item set print type methods
15759 @itemx set print type methods on
15760 @itemx set print type methods off
15761 Normally, when @value{GDBN} prints a class, it displays any methods
15762 declared in that class. You can control this behavior either by
15763 passing the appropriate flag to @code{ptype}, or using @command{set
15764 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15765 display the methods; this is the default. Specifying @code{off} will
15766 cause @value{GDBN} to omit the methods.
15768 @kindex show print type methods
15769 @item show print type methods
15770 This command shows the current setting of method display when printing
15773 @kindex set print type typedefs
15774 @item set print type typedefs
15775 @itemx set print type typedefs on
15776 @itemx set print type typedefs off
15778 Normally, when @value{GDBN} prints a class, it displays any typedefs
15779 defined in that class. You can control this behavior either by
15780 passing the appropriate flag to @code{ptype}, or using @command{set
15781 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15782 display the typedef definitions; this is the default. Specifying
15783 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15784 Note that this controls whether the typedef definition itself is
15785 printed, not whether typedef names are substituted when printing other
15788 @kindex show print type typedefs
15789 @item show print type typedefs
15790 This command shows the current setting of typedef display when
15793 @kindex info address
15794 @cindex address of a symbol
15795 @item info address @var{symbol}
15796 Describe where the data for @var{symbol} is stored. For a register
15797 variable, this says which register it is kept in. For a non-register
15798 local variable, this prints the stack-frame offset at which the variable
15801 Note the contrast with @samp{print &@var{symbol}}, which does not work
15802 at all for a register variable, and for a stack local variable prints
15803 the exact address of the current instantiation of the variable.
15805 @kindex info symbol
15806 @cindex symbol from address
15807 @cindex closest symbol and offset for an address
15808 @item info symbol @var{addr}
15809 Print the name of a symbol which is stored at the address @var{addr}.
15810 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15811 nearest symbol and an offset from it:
15814 (@value{GDBP}) info symbol 0x54320
15815 _initialize_vx + 396 in section .text
15819 This is the opposite of the @code{info address} command. You can use
15820 it to find out the name of a variable or a function given its address.
15822 For dynamically linked executables, the name of executable or shared
15823 library containing the symbol is also printed:
15826 (@value{GDBP}) info symbol 0x400225
15827 _start + 5 in section .text of /tmp/a.out
15828 (@value{GDBP}) info symbol 0x2aaaac2811cf
15829 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15833 @item whatis[/@var{flags}] [@var{arg}]
15834 Print the data type of @var{arg}, which can be either an expression
15835 or a name of a data type. With no argument, print the data type of
15836 @code{$}, the last value in the value history.
15838 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15839 is not actually evaluated, and any side-effecting operations (such as
15840 assignments or function calls) inside it do not take place.
15842 If @var{arg} is a variable or an expression, @code{whatis} prints its
15843 literal type as it is used in the source code. If the type was
15844 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15845 the data type underlying the @code{typedef}. If the type of the
15846 variable or the expression is a compound data type, such as
15847 @code{struct} or @code{class}, @code{whatis} never prints their
15848 fields or methods. It just prints the @code{struct}/@code{class}
15849 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15850 such a compound data type, use @code{ptype}.
15852 If @var{arg} is a type name that was defined using @code{typedef},
15853 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15854 Unrolling means that @code{whatis} will show the underlying type used
15855 in the @code{typedef} declaration of @var{arg}. However, if that
15856 underlying type is also a @code{typedef}, @code{whatis} will not
15859 For C code, the type names may also have the form @samp{class
15860 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15861 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15863 @var{flags} can be used to modify how the type is displayed.
15864 Available flags are:
15868 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15869 parameters and typedefs defined in a class when printing the class'
15870 members. The @code{/r} flag disables this.
15873 Do not print methods defined in the class.
15876 Print methods defined in the class. This is the default, but the flag
15877 exists in case you change the default with @command{set print type methods}.
15880 Do not print typedefs defined in the class. Note that this controls
15881 whether the typedef definition itself is printed, not whether typedef
15882 names are substituted when printing other types.
15885 Print typedefs defined in the class. This is the default, but the flag
15886 exists in case you change the default with @command{set print type typedefs}.
15890 @item ptype[/@var{flags}] [@var{arg}]
15891 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15892 detailed description of the type, instead of just the name of the type.
15893 @xref{Expressions, ,Expressions}.
15895 Contrary to @code{whatis}, @code{ptype} always unrolls any
15896 @code{typedef}s in its argument declaration, whether the argument is
15897 a variable, expression, or a data type. This means that @code{ptype}
15898 of a variable or an expression will not print literally its type as
15899 present in the source code---use @code{whatis} for that. @code{typedef}s at
15900 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15901 fields, methods and inner @code{class typedef}s of @code{struct}s,
15902 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15904 For example, for this variable declaration:
15907 typedef double real_t;
15908 struct complex @{ real_t real; double imag; @};
15909 typedef struct complex complex_t;
15911 real_t *real_pointer_var;
15915 the two commands give this output:
15919 (@value{GDBP}) whatis var
15921 (@value{GDBP}) ptype var
15922 type = struct complex @{
15926 (@value{GDBP}) whatis complex_t
15927 type = struct complex
15928 (@value{GDBP}) whatis struct complex
15929 type = struct complex
15930 (@value{GDBP}) ptype struct complex
15931 type = struct complex @{
15935 (@value{GDBP}) whatis real_pointer_var
15937 (@value{GDBP}) ptype real_pointer_var
15943 As with @code{whatis}, using @code{ptype} without an argument refers to
15944 the type of @code{$}, the last value in the value history.
15946 @cindex incomplete type
15947 Sometimes, programs use opaque data types or incomplete specifications
15948 of complex data structure. If the debug information included in the
15949 program does not allow @value{GDBN} to display a full declaration of
15950 the data type, it will say @samp{<incomplete type>}. For example,
15951 given these declarations:
15955 struct foo *fooptr;
15959 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15962 (@value{GDBP}) ptype foo
15963 $1 = <incomplete type>
15967 ``Incomplete type'' is C terminology for data types that are not
15968 completely specified.
15971 @item info types @var{regexp}
15973 Print a brief description of all types whose names match the regular
15974 expression @var{regexp} (or all types in your program, if you supply
15975 no argument). Each complete typename is matched as though it were a
15976 complete line; thus, @samp{i type value} gives information on all
15977 types in your program whose names include the string @code{value}, but
15978 @samp{i type ^value$} gives information only on types whose complete
15979 name is @code{value}.
15981 This command differs from @code{ptype} in two ways: first, like
15982 @code{whatis}, it does not print a detailed description; second, it
15983 lists all source files where a type is defined.
15985 @kindex info type-printers
15986 @item info type-printers
15987 Versions of @value{GDBN} that ship with Python scripting enabled may
15988 have ``type printers'' available. When using @command{ptype} or
15989 @command{whatis}, these printers are consulted when the name of a type
15990 is needed. @xref{Type Printing API}, for more information on writing
15993 @code{info type-printers} displays all the available type printers.
15995 @kindex enable type-printer
15996 @kindex disable type-printer
15997 @item enable type-printer @var{name}@dots{}
15998 @item disable type-printer @var{name}@dots{}
15999 These commands can be used to enable or disable type printers.
16002 @cindex local variables
16003 @item info scope @var{location}
16004 List all the variables local to a particular scope. This command
16005 accepts a @var{location} argument---a function name, a source line, or
16006 an address preceded by a @samp{*}, and prints all the variables local
16007 to the scope defined by that location. (@xref{Specify Location}, for
16008 details about supported forms of @var{location}.) For example:
16011 (@value{GDBP}) @b{info scope command_line_handler}
16012 Scope for command_line_handler:
16013 Symbol rl is an argument at stack/frame offset 8, length 4.
16014 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16015 Symbol linelength is in static storage at address 0x150a1c, length 4.
16016 Symbol p is a local variable in register $esi, length 4.
16017 Symbol p1 is a local variable in register $ebx, length 4.
16018 Symbol nline is a local variable in register $edx, length 4.
16019 Symbol repeat is a local variable at frame offset -8, length 4.
16023 This command is especially useful for determining what data to collect
16024 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16027 @kindex info source
16029 Show information about the current source file---that is, the source file for
16030 the function containing the current point of execution:
16033 the name of the source file, and the directory containing it,
16035 the directory it was compiled in,
16037 its length, in lines,
16039 which programming language it is written in,
16041 whether the executable includes debugging information for that file, and
16042 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16044 whether the debugging information includes information about
16045 preprocessor macros.
16049 @kindex info sources
16051 Print the names of all source files in your program for which there is
16052 debugging information, organized into two lists: files whose symbols
16053 have already been read, and files whose symbols will be read when needed.
16055 @kindex info functions
16056 @item info functions
16057 Print the names and data types of all defined functions.
16059 @item info functions @var{regexp}
16060 Print the names and data types of all defined functions
16061 whose names contain a match for regular expression @var{regexp}.
16062 Thus, @samp{info fun step} finds all functions whose names
16063 include @code{step}; @samp{info fun ^step} finds those whose names
16064 start with @code{step}. If a function name contains characters
16065 that conflict with the regular expression language (e.g.@:
16066 @samp{operator*()}), they may be quoted with a backslash.
16068 @kindex info variables
16069 @item info variables
16070 Print the names and data types of all variables that are defined
16071 outside of functions (i.e.@: excluding local variables).
16073 @item info variables @var{regexp}
16074 Print the names and data types of all variables (except for local
16075 variables) whose names contain a match for regular expression
16078 @kindex info classes
16079 @cindex Objective-C, classes and selectors
16081 @itemx info classes @var{regexp}
16082 Display all Objective-C classes in your program, or
16083 (with the @var{regexp} argument) all those matching a particular regular
16086 @kindex info selectors
16087 @item info selectors
16088 @itemx info selectors @var{regexp}
16089 Display all Objective-C selectors in your program, or
16090 (with the @var{regexp} argument) all those matching a particular regular
16094 This was never implemented.
16095 @kindex info methods
16097 @itemx info methods @var{regexp}
16098 The @code{info methods} command permits the user to examine all defined
16099 methods within C@t{++} program, or (with the @var{regexp} argument) a
16100 specific set of methods found in the various C@t{++} classes. Many
16101 C@t{++} classes provide a large number of methods. Thus, the output
16102 from the @code{ptype} command can be overwhelming and hard to use. The
16103 @code{info-methods} command filters the methods, printing only those
16104 which match the regular-expression @var{regexp}.
16107 @cindex opaque data types
16108 @kindex set opaque-type-resolution
16109 @item set opaque-type-resolution on
16110 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16111 declared as a pointer to a @code{struct}, @code{class}, or
16112 @code{union}---for example, @code{struct MyType *}---that is used in one
16113 source file although the full declaration of @code{struct MyType} is in
16114 another source file. The default is on.
16116 A change in the setting of this subcommand will not take effect until
16117 the next time symbols for a file are loaded.
16119 @item set opaque-type-resolution off
16120 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16121 is printed as follows:
16123 @{<no data fields>@}
16126 @kindex show opaque-type-resolution
16127 @item show opaque-type-resolution
16128 Show whether opaque types are resolved or not.
16130 @kindex maint print symbols
16131 @cindex symbol dump
16132 @kindex maint print psymbols
16133 @cindex partial symbol dump
16134 @kindex maint print msymbols
16135 @cindex minimal symbol dump
16136 @item maint print symbols @var{filename}
16137 @itemx maint print psymbols @var{filename}
16138 @itemx maint print msymbols @var{filename}
16139 Write a dump of debugging symbol data into the file @var{filename}.
16140 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16141 symbols with debugging data are included. If you use @samp{maint print
16142 symbols}, @value{GDBN} includes all the symbols for which it has already
16143 collected full details: that is, @var{filename} reflects symbols for
16144 only those files whose symbols @value{GDBN} has read. You can use the
16145 command @code{info sources} to find out which files these are. If you
16146 use @samp{maint print psymbols} instead, the dump shows information about
16147 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16148 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16149 @samp{maint print msymbols} dumps just the minimal symbol information
16150 required for each object file from which @value{GDBN} has read some symbols.
16151 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16152 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16154 @kindex maint info symtabs
16155 @kindex maint info psymtabs
16156 @cindex listing @value{GDBN}'s internal symbol tables
16157 @cindex symbol tables, listing @value{GDBN}'s internal
16158 @cindex full symbol tables, listing @value{GDBN}'s internal
16159 @cindex partial symbol tables, listing @value{GDBN}'s internal
16160 @item maint info symtabs @r{[} @var{regexp} @r{]}
16161 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16163 List the @code{struct symtab} or @code{struct partial_symtab}
16164 structures whose names match @var{regexp}. If @var{regexp} is not
16165 given, list them all. The output includes expressions which you can
16166 copy into a @value{GDBN} debugging this one to examine a particular
16167 structure in more detail. For example:
16170 (@value{GDBP}) maint info psymtabs dwarf2read
16171 @{ objfile /home/gnu/build/gdb/gdb
16172 ((struct objfile *) 0x82e69d0)
16173 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16174 ((struct partial_symtab *) 0x8474b10)
16177 text addresses 0x814d3c8 -- 0x8158074
16178 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16179 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16180 dependencies (none)
16183 (@value{GDBP}) maint info symtabs
16187 We see that there is one partial symbol table whose filename contains
16188 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16189 and we see that @value{GDBN} has not read in any symtabs yet at all.
16190 If we set a breakpoint on a function, that will cause @value{GDBN} to
16191 read the symtab for the compilation unit containing that function:
16194 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16195 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16197 (@value{GDBP}) maint info symtabs
16198 @{ objfile /home/gnu/build/gdb/gdb
16199 ((struct objfile *) 0x82e69d0)
16200 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16201 ((struct symtab *) 0x86c1f38)
16204 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16205 linetable ((struct linetable *) 0x8370fa0)
16206 debugformat DWARF 2
16215 @chapter Altering Execution
16217 Once you think you have found an error in your program, you might want to
16218 find out for certain whether correcting the apparent error would lead to
16219 correct results in the rest of the run. You can find the answer by
16220 experiment, using the @value{GDBN} features for altering execution of the
16223 For example, you can store new values into variables or memory
16224 locations, give your program a signal, restart it at a different
16225 address, or even return prematurely from a function.
16228 * Assignment:: Assignment to variables
16229 * Jumping:: Continuing at a different address
16230 * Signaling:: Giving your program a signal
16231 * Returning:: Returning from a function
16232 * Calling:: Calling your program's functions
16233 * Patching:: Patching your program
16237 @section Assignment to Variables
16240 @cindex setting variables
16241 To alter the value of a variable, evaluate an assignment expression.
16242 @xref{Expressions, ,Expressions}. For example,
16249 stores the value 4 into the variable @code{x}, and then prints the
16250 value of the assignment expression (which is 4).
16251 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16252 information on operators in supported languages.
16254 @kindex set variable
16255 @cindex variables, setting
16256 If you are not interested in seeing the value of the assignment, use the
16257 @code{set} command instead of the @code{print} command. @code{set} is
16258 really the same as @code{print} except that the expression's value is
16259 not printed and is not put in the value history (@pxref{Value History,
16260 ,Value History}). The expression is evaluated only for its effects.
16262 If the beginning of the argument string of the @code{set} command
16263 appears identical to a @code{set} subcommand, use the @code{set
16264 variable} command instead of just @code{set}. This command is identical
16265 to @code{set} except for its lack of subcommands. For example, if your
16266 program has a variable @code{width}, you get an error if you try to set
16267 a new value with just @samp{set width=13}, because @value{GDBN} has the
16268 command @code{set width}:
16271 (@value{GDBP}) whatis width
16273 (@value{GDBP}) p width
16275 (@value{GDBP}) set width=47
16276 Invalid syntax in expression.
16280 The invalid expression, of course, is @samp{=47}. In
16281 order to actually set the program's variable @code{width}, use
16284 (@value{GDBP}) set var width=47
16287 Because the @code{set} command has many subcommands that can conflict
16288 with the names of program variables, it is a good idea to use the
16289 @code{set variable} command instead of just @code{set}. For example, if
16290 your program has a variable @code{g}, you run into problems if you try
16291 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16292 the command @code{set gnutarget}, abbreviated @code{set g}:
16296 (@value{GDBP}) whatis g
16300 (@value{GDBP}) set g=4
16304 The program being debugged has been started already.
16305 Start it from the beginning? (y or n) y
16306 Starting program: /home/smith/cc_progs/a.out
16307 "/home/smith/cc_progs/a.out": can't open to read symbols:
16308 Invalid bfd target.
16309 (@value{GDBP}) show g
16310 The current BFD target is "=4".
16315 The program variable @code{g} did not change, and you silently set the
16316 @code{gnutarget} to an invalid value. In order to set the variable
16320 (@value{GDBP}) set var g=4
16323 @value{GDBN} allows more implicit conversions in assignments than C; you can
16324 freely store an integer value into a pointer variable or vice versa,
16325 and you can convert any structure to any other structure that is the
16326 same length or shorter.
16327 @comment FIXME: how do structs align/pad in these conversions?
16328 @comment /doc@cygnus.com 18dec1990
16330 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16331 construct to generate a value of specified type at a specified address
16332 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16333 to memory location @code{0x83040} as an integer (which implies a certain size
16334 and representation in memory), and
16337 set @{int@}0x83040 = 4
16341 stores the value 4 into that memory location.
16344 @section Continuing at a Different Address
16346 Ordinarily, when you continue your program, you do so at the place where
16347 it stopped, with the @code{continue} command. You can instead continue at
16348 an address of your own choosing, with the following commands:
16352 @kindex j @r{(@code{jump})}
16353 @item jump @var{linespec}
16354 @itemx j @var{linespec}
16355 @itemx jump @var{location}
16356 @itemx j @var{location}
16357 Resume execution at line @var{linespec} or at address given by
16358 @var{location}. Execution stops again immediately if there is a
16359 breakpoint there. @xref{Specify Location}, for a description of the
16360 different forms of @var{linespec} and @var{location}. It is common
16361 practice to use the @code{tbreak} command in conjunction with
16362 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16364 The @code{jump} command does not change the current stack frame, or
16365 the stack pointer, or the contents of any memory location or any
16366 register other than the program counter. If line @var{linespec} is in
16367 a different function from the one currently executing, the results may
16368 be bizarre if the two functions expect different patterns of arguments or
16369 of local variables. For this reason, the @code{jump} command requests
16370 confirmation if the specified line is not in the function currently
16371 executing. However, even bizarre results are predictable if you are
16372 well acquainted with the machine-language code of your program.
16375 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16376 On many systems, you can get much the same effect as the @code{jump}
16377 command by storing a new value into the register @code{$pc}. The
16378 difference is that this does not start your program running; it only
16379 changes the address of where it @emph{will} run when you continue. For
16387 makes the next @code{continue} command or stepping command execute at
16388 address @code{0x485}, rather than at the address where your program stopped.
16389 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16391 The most common occasion to use the @code{jump} command is to back
16392 up---perhaps with more breakpoints set---over a portion of a program
16393 that has already executed, in order to examine its execution in more
16398 @section Giving your Program a Signal
16399 @cindex deliver a signal to a program
16403 @item signal @var{signal}
16404 Resume execution where your program stopped, but immediately give it the
16405 signal @var{signal}. @var{signal} can be the name or the number of a
16406 signal. For example, on many systems @code{signal 2} and @code{signal
16407 SIGINT} are both ways of sending an interrupt signal.
16409 Alternatively, if @var{signal} is zero, continue execution without
16410 giving a signal. This is useful when your program stopped on account of
16411 a signal and would ordinarily see the signal when resumed with the
16412 @code{continue} command; @samp{signal 0} causes it to resume without a
16415 @code{signal} does not repeat when you press @key{RET} a second time
16416 after executing the command.
16420 Invoking the @code{signal} command is not the same as invoking the
16421 @code{kill} utility from the shell. Sending a signal with @code{kill}
16422 causes @value{GDBN} to decide what to do with the signal depending on
16423 the signal handling tables (@pxref{Signals}). The @code{signal} command
16424 passes the signal directly to your program.
16428 @section Returning from a Function
16431 @cindex returning from a function
16434 @itemx return @var{expression}
16435 You can cancel execution of a function call with the @code{return}
16436 command. If you give an
16437 @var{expression} argument, its value is used as the function's return
16441 When you use @code{return}, @value{GDBN} discards the selected stack frame
16442 (and all frames within it). You can think of this as making the
16443 discarded frame return prematurely. If you wish to specify a value to
16444 be returned, give that value as the argument to @code{return}.
16446 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16447 Frame}), and any other frames inside of it, leaving its caller as the
16448 innermost remaining frame. That frame becomes selected. The
16449 specified value is stored in the registers used for returning values
16452 The @code{return} command does not resume execution; it leaves the
16453 program stopped in the state that would exist if the function had just
16454 returned. In contrast, the @code{finish} command (@pxref{Continuing
16455 and Stepping, ,Continuing and Stepping}) resumes execution until the
16456 selected stack frame returns naturally.
16458 @value{GDBN} needs to know how the @var{expression} argument should be set for
16459 the inferior. The concrete registers assignment depends on the OS ABI and the
16460 type being returned by the selected stack frame. For example it is common for
16461 OS ABI to return floating point values in FPU registers while integer values in
16462 CPU registers. Still some ABIs return even floating point values in CPU
16463 registers. Larger integer widths (such as @code{long long int}) also have
16464 specific placement rules. @value{GDBN} already knows the OS ABI from its
16465 current target so it needs to find out also the type being returned to make the
16466 assignment into the right register(s).
16468 Normally, the selected stack frame has debug info. @value{GDBN} will always
16469 use the debug info instead of the implicit type of @var{expression} when the
16470 debug info is available. For example, if you type @kbd{return -1}, and the
16471 function in the current stack frame is declared to return a @code{long long
16472 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16473 into a @code{long long int}:
16476 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16478 (@value{GDBP}) return -1
16479 Make func return now? (y or n) y
16480 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16481 43 printf ("result=%lld\n", func ());
16485 However, if the selected stack frame does not have a debug info, e.g., if the
16486 function was compiled without debug info, @value{GDBN} has to find out the type
16487 to return from user. Specifying a different type by mistake may set the value
16488 in different inferior registers than the caller code expects. For example,
16489 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16490 of a @code{long long int} result for a debug info less function (on 32-bit
16491 architectures). Therefore the user is required to specify the return type by
16492 an appropriate cast explicitly:
16495 Breakpoint 2, 0x0040050b in func ()
16496 (@value{GDBP}) return -1
16497 Return value type not available for selected stack frame.
16498 Please use an explicit cast of the value to return.
16499 (@value{GDBP}) return (long long int) -1
16500 Make selected stack frame return now? (y or n) y
16501 #0 0x00400526 in main ()
16506 @section Calling Program Functions
16509 @cindex calling functions
16510 @cindex inferior functions, calling
16511 @item print @var{expr}
16512 Evaluate the expression @var{expr} and display the resulting value.
16513 @var{expr} may include calls to functions in the program being
16517 @item call @var{expr}
16518 Evaluate the expression @var{expr} without displaying @code{void}
16521 You can use this variant of the @code{print} command if you want to
16522 execute a function from your program that does not return anything
16523 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16524 with @code{void} returned values that @value{GDBN} will otherwise
16525 print. If the result is not void, it is printed and saved in the
16529 It is possible for the function you call via the @code{print} or
16530 @code{call} command to generate a signal (e.g., if there's a bug in
16531 the function, or if you passed it incorrect arguments). What happens
16532 in that case is controlled by the @code{set unwindonsignal} command.
16534 Similarly, with a C@t{++} program it is possible for the function you
16535 call via the @code{print} or @code{call} command to generate an
16536 exception that is not handled due to the constraints of the dummy
16537 frame. In this case, any exception that is raised in the frame, but has
16538 an out-of-frame exception handler will not be found. GDB builds a
16539 dummy-frame for the inferior function call, and the unwinder cannot
16540 seek for exception handlers outside of this dummy-frame. What happens
16541 in that case is controlled by the
16542 @code{set unwind-on-terminating-exception} command.
16545 @item set unwindonsignal
16546 @kindex set unwindonsignal
16547 @cindex unwind stack in called functions
16548 @cindex call dummy stack unwinding
16549 Set unwinding of the stack if a signal is received while in a function
16550 that @value{GDBN} called in the program being debugged. If set to on,
16551 @value{GDBN} unwinds the stack it created for the call and restores
16552 the context to what it was before the call. If set to off (the
16553 default), @value{GDBN} stops in the frame where the signal was
16556 @item show unwindonsignal
16557 @kindex show unwindonsignal
16558 Show the current setting of stack unwinding in the functions called by
16561 @item set unwind-on-terminating-exception
16562 @kindex set unwind-on-terminating-exception
16563 @cindex unwind stack in called functions with unhandled exceptions
16564 @cindex call dummy stack unwinding on unhandled exception.
16565 Set unwinding of the stack if a C@t{++} exception is raised, but left
16566 unhandled while in a function that @value{GDBN} called in the program being
16567 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16568 it created for the call and restores the context to what it was before
16569 the call. If set to off, @value{GDBN} the exception is delivered to
16570 the default C@t{++} exception handler and the inferior terminated.
16572 @item show unwind-on-terminating-exception
16573 @kindex show unwind-on-terminating-exception
16574 Show the current setting of stack unwinding in the functions called by
16579 @cindex weak alias functions
16580 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16581 for another function. In such case, @value{GDBN} might not pick up
16582 the type information, including the types of the function arguments,
16583 which causes @value{GDBN} to call the inferior function incorrectly.
16584 As a result, the called function will function erroneously and may
16585 even crash. A solution to that is to use the name of the aliased
16589 @section Patching Programs
16591 @cindex patching binaries
16592 @cindex writing into executables
16593 @cindex writing into corefiles
16595 By default, @value{GDBN} opens the file containing your program's
16596 executable code (or the corefile) read-only. This prevents accidental
16597 alterations to machine code; but it also prevents you from intentionally
16598 patching your program's binary.
16600 If you'd like to be able to patch the binary, you can specify that
16601 explicitly with the @code{set write} command. For example, you might
16602 want to turn on internal debugging flags, or even to make emergency
16608 @itemx set write off
16609 If you specify @samp{set write on}, @value{GDBN} opens executable and
16610 core files for both reading and writing; if you specify @kbd{set write
16611 off} (the default), @value{GDBN} opens them read-only.
16613 If you have already loaded a file, you must load it again (using the
16614 @code{exec-file} or @code{core-file} command) after changing @code{set
16615 write}, for your new setting to take effect.
16619 Display whether executable files and core files are opened for writing
16620 as well as reading.
16624 @chapter @value{GDBN} Files
16626 @value{GDBN} needs to know the file name of the program to be debugged,
16627 both in order to read its symbol table and in order to start your
16628 program. To debug a core dump of a previous run, you must also tell
16629 @value{GDBN} the name of the core dump file.
16632 * Files:: Commands to specify files
16633 * Separate Debug Files:: Debugging information in separate files
16634 * MiniDebugInfo:: Debugging information in a special section
16635 * Index Files:: Index files speed up GDB
16636 * Symbol Errors:: Errors reading symbol files
16637 * Data Files:: GDB data files
16641 @section Commands to Specify Files
16643 @cindex symbol table
16644 @cindex core dump file
16646 You may want to specify executable and core dump file names. The usual
16647 way to do this is at start-up time, using the arguments to
16648 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16649 Out of @value{GDBN}}).
16651 Occasionally it is necessary to change to a different file during a
16652 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16653 specify a file you want to use. Or you are debugging a remote target
16654 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16655 Program}). In these situations the @value{GDBN} commands to specify
16656 new files are useful.
16659 @cindex executable file
16661 @item file @var{filename}
16662 Use @var{filename} as the program to be debugged. It is read for its
16663 symbols and for the contents of pure memory. It is also the program
16664 executed when you use the @code{run} command. If you do not specify a
16665 directory and the file is not found in the @value{GDBN} working directory,
16666 @value{GDBN} uses the environment variable @code{PATH} as a list of
16667 directories to search, just as the shell does when looking for a program
16668 to run. You can change the value of this variable, for both @value{GDBN}
16669 and your program, using the @code{path} command.
16671 @cindex unlinked object files
16672 @cindex patching object files
16673 You can load unlinked object @file{.o} files into @value{GDBN} using
16674 the @code{file} command. You will not be able to ``run'' an object
16675 file, but you can disassemble functions and inspect variables. Also,
16676 if the underlying BFD functionality supports it, you could use
16677 @kbd{gdb -write} to patch object files using this technique. Note
16678 that @value{GDBN} can neither interpret nor modify relocations in this
16679 case, so branches and some initialized variables will appear to go to
16680 the wrong place. But this feature is still handy from time to time.
16683 @code{file} with no argument makes @value{GDBN} discard any information it
16684 has on both executable file and the symbol table.
16687 @item exec-file @r{[} @var{filename} @r{]}
16688 Specify that the program to be run (but not the symbol table) is found
16689 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16690 if necessary to locate your program. Omitting @var{filename} means to
16691 discard information on the executable file.
16693 @kindex symbol-file
16694 @item symbol-file @r{[} @var{filename} @r{]}
16695 Read symbol table information from file @var{filename}. @code{PATH} is
16696 searched when necessary. Use the @code{file} command to get both symbol
16697 table and program to run from the same file.
16699 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16700 program's symbol table.
16702 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16703 some breakpoints and auto-display expressions. This is because they may
16704 contain pointers to the internal data recording symbols and data types,
16705 which are part of the old symbol table data being discarded inside
16708 @code{symbol-file} does not repeat if you press @key{RET} again after
16711 When @value{GDBN} is configured for a particular environment, it
16712 understands debugging information in whatever format is the standard
16713 generated for that environment; you may use either a @sc{gnu} compiler, or
16714 other compilers that adhere to the local conventions.
16715 Best results are usually obtained from @sc{gnu} compilers; for example,
16716 using @code{@value{NGCC}} you can generate debugging information for
16719 For most kinds of object files, with the exception of old SVR3 systems
16720 using COFF, the @code{symbol-file} command does not normally read the
16721 symbol table in full right away. Instead, it scans the symbol table
16722 quickly to find which source files and which symbols are present. The
16723 details are read later, one source file at a time, as they are needed.
16725 The purpose of this two-stage reading strategy is to make @value{GDBN}
16726 start up faster. For the most part, it is invisible except for
16727 occasional pauses while the symbol table details for a particular source
16728 file are being read. (The @code{set verbose} command can turn these
16729 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16730 Warnings and Messages}.)
16732 We have not implemented the two-stage strategy for COFF yet. When the
16733 symbol table is stored in COFF format, @code{symbol-file} reads the
16734 symbol table data in full right away. Note that ``stabs-in-COFF''
16735 still does the two-stage strategy, since the debug info is actually
16739 @cindex reading symbols immediately
16740 @cindex symbols, reading immediately
16741 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16742 @itemx file @r{[} -readnow @r{]} @var{filename}
16743 You can override the @value{GDBN} two-stage strategy for reading symbol
16744 tables by using the @samp{-readnow} option with any of the commands that
16745 load symbol table information, if you want to be sure @value{GDBN} has the
16746 entire symbol table available.
16748 @c FIXME: for now no mention of directories, since this seems to be in
16749 @c flux. 13mar1992 status is that in theory GDB would look either in
16750 @c current dir or in same dir as myprog; but issues like competing
16751 @c GDB's, or clutter in system dirs, mean that in practice right now
16752 @c only current dir is used. FFish says maybe a special GDB hierarchy
16753 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16757 @item core-file @r{[}@var{filename}@r{]}
16759 Specify the whereabouts of a core dump file to be used as the ``contents
16760 of memory''. Traditionally, core files contain only some parts of the
16761 address space of the process that generated them; @value{GDBN} can access the
16762 executable file itself for other parts.
16764 @code{core-file} with no argument specifies that no core file is
16767 Note that the core file is ignored when your program is actually running
16768 under @value{GDBN}. So, if you have been running your program and you
16769 wish to debug a core file instead, you must kill the subprocess in which
16770 the program is running. To do this, use the @code{kill} command
16771 (@pxref{Kill Process, ,Killing the Child Process}).
16773 @kindex add-symbol-file
16774 @cindex dynamic linking
16775 @item add-symbol-file @var{filename} @var{address}
16776 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16777 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16778 The @code{add-symbol-file} command reads additional symbol table
16779 information from the file @var{filename}. You would use this command
16780 when @var{filename} has been dynamically loaded (by some other means)
16781 into the program that is running. @var{address} should be the memory
16782 address at which the file has been loaded; @value{GDBN} cannot figure
16783 this out for itself. You can additionally specify an arbitrary number
16784 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16785 section name and base address for that section. You can specify any
16786 @var{address} as an expression.
16788 The symbol table of the file @var{filename} is added to the symbol table
16789 originally read with the @code{symbol-file} command. You can use the
16790 @code{add-symbol-file} command any number of times; the new symbol data
16791 thus read is kept in addition to the old.
16793 Changes can be reverted using the command @code{remove-symbol-file}.
16795 @cindex relocatable object files, reading symbols from
16796 @cindex object files, relocatable, reading symbols from
16797 @cindex reading symbols from relocatable object files
16798 @cindex symbols, reading from relocatable object files
16799 @cindex @file{.o} files, reading symbols from
16800 Although @var{filename} is typically a shared library file, an
16801 executable file, or some other object file which has been fully
16802 relocated for loading into a process, you can also load symbolic
16803 information from relocatable @file{.o} files, as long as:
16807 the file's symbolic information refers only to linker symbols defined in
16808 that file, not to symbols defined by other object files,
16810 every section the file's symbolic information refers to has actually
16811 been loaded into the inferior, as it appears in the file, and
16813 you can determine the address at which every section was loaded, and
16814 provide these to the @code{add-symbol-file} command.
16818 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16819 relocatable files into an already running program; such systems
16820 typically make the requirements above easy to meet. However, it's
16821 important to recognize that many native systems use complex link
16822 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16823 assembly, for example) that make the requirements difficult to meet. In
16824 general, one cannot assume that using @code{add-symbol-file} to read a
16825 relocatable object file's symbolic information will have the same effect
16826 as linking the relocatable object file into the program in the normal
16829 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16831 @kindex remove-symbol-file
16832 @item remove-symbol-file @var{filename}
16833 @item remove-symbol-file -a @var{address}
16834 Remove a symbol file added via the @code{add-symbol-file} command. The
16835 file to remove can be identified by its @var{filename} or by an @var{address}
16836 that lies within the boundaries of this symbol file in memory. Example:
16839 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
16840 add symbol table from file "/home/user/gdb/mylib.so" at
16841 .text_addr = 0x7ffff7ff9480
16843 Reading symbols from /home/user/gdb/mylib.so...done.
16844 (gdb) remove-symbol-file -a 0x7ffff7ff9480
16845 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
16850 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
16852 @kindex add-symbol-file-from-memory
16853 @cindex @code{syscall DSO}
16854 @cindex load symbols from memory
16855 @item add-symbol-file-from-memory @var{address}
16856 Load symbols from the given @var{address} in a dynamically loaded
16857 object file whose image is mapped directly into the inferior's memory.
16858 For example, the Linux kernel maps a @code{syscall DSO} into each
16859 process's address space; this DSO provides kernel-specific code for
16860 some system calls. The argument can be any expression whose
16861 evaluation yields the address of the file's shared object file header.
16862 For this command to work, you must have used @code{symbol-file} or
16863 @code{exec-file} commands in advance.
16865 @kindex add-shared-symbol-files
16867 @item add-shared-symbol-files @var{library-file}
16868 @itemx assf @var{library-file}
16869 The @code{add-shared-symbol-files} command can currently be used only
16870 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16871 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16872 @value{GDBN} automatically looks for shared libraries, however if
16873 @value{GDBN} does not find yours, you can invoke
16874 @code{add-shared-symbol-files}. It takes one argument: the shared
16875 library's file name. @code{assf} is a shorthand alias for
16876 @code{add-shared-symbol-files}.
16879 @item section @var{section} @var{addr}
16880 The @code{section} command changes the base address of the named
16881 @var{section} of the exec file to @var{addr}. This can be used if the
16882 exec file does not contain section addresses, (such as in the
16883 @code{a.out} format), or when the addresses specified in the file
16884 itself are wrong. Each section must be changed separately. The
16885 @code{info files} command, described below, lists all the sections and
16889 @kindex info target
16892 @code{info files} and @code{info target} are synonymous; both print the
16893 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16894 including the names of the executable and core dump files currently in
16895 use by @value{GDBN}, and the files from which symbols were loaded. The
16896 command @code{help target} lists all possible targets rather than
16899 @kindex maint info sections
16900 @item maint info sections
16901 Another command that can give you extra information about program sections
16902 is @code{maint info sections}. In addition to the section information
16903 displayed by @code{info files}, this command displays the flags and file
16904 offset of each section in the executable and core dump files. In addition,
16905 @code{maint info sections} provides the following command options (which
16906 may be arbitrarily combined):
16910 Display sections for all loaded object files, including shared libraries.
16911 @item @var{sections}
16912 Display info only for named @var{sections}.
16913 @item @var{section-flags}
16914 Display info only for sections for which @var{section-flags} are true.
16915 The section flags that @value{GDBN} currently knows about are:
16918 Section will have space allocated in the process when loaded.
16919 Set for all sections except those containing debug information.
16921 Section will be loaded from the file into the child process memory.
16922 Set for pre-initialized code and data, clear for @code{.bss} sections.
16924 Section needs to be relocated before loading.
16926 Section cannot be modified by the child process.
16928 Section contains executable code only.
16930 Section contains data only (no executable code).
16932 Section will reside in ROM.
16934 Section contains data for constructor/destructor lists.
16936 Section is not empty.
16938 An instruction to the linker to not output the section.
16939 @item COFF_SHARED_LIBRARY
16940 A notification to the linker that the section contains
16941 COFF shared library information.
16943 Section contains common symbols.
16946 @kindex set trust-readonly-sections
16947 @cindex read-only sections
16948 @item set trust-readonly-sections on
16949 Tell @value{GDBN} that readonly sections in your object file
16950 really are read-only (i.e.@: that their contents will not change).
16951 In that case, @value{GDBN} can fetch values from these sections
16952 out of the object file, rather than from the target program.
16953 For some targets (notably embedded ones), this can be a significant
16954 enhancement to debugging performance.
16956 The default is off.
16958 @item set trust-readonly-sections off
16959 Tell @value{GDBN} not to trust readonly sections. This means that
16960 the contents of the section might change while the program is running,
16961 and must therefore be fetched from the target when needed.
16963 @item show trust-readonly-sections
16964 Show the current setting of trusting readonly sections.
16967 All file-specifying commands allow both absolute and relative file names
16968 as arguments. @value{GDBN} always converts the file name to an absolute file
16969 name and remembers it that way.
16971 @cindex shared libraries
16972 @anchor{Shared Libraries}
16973 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16974 and IBM RS/6000 AIX shared libraries.
16976 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16977 shared libraries. @xref{Expat}.
16979 @value{GDBN} automatically loads symbol definitions from shared libraries
16980 when you use the @code{run} command, or when you examine a core file.
16981 (Before you issue the @code{run} command, @value{GDBN} does not understand
16982 references to a function in a shared library, however---unless you are
16983 debugging a core file).
16985 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16986 automatically loads the symbols at the time of the @code{shl_load} call.
16988 @c FIXME: some @value{GDBN} release may permit some refs to undef
16989 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16990 @c FIXME...lib; check this from time to time when updating manual
16992 There are times, however, when you may wish to not automatically load
16993 symbol definitions from shared libraries, such as when they are
16994 particularly large or there are many of them.
16996 To control the automatic loading of shared library symbols, use the
17000 @kindex set auto-solib-add
17001 @item set auto-solib-add @var{mode}
17002 If @var{mode} is @code{on}, symbols from all shared object libraries
17003 will be loaded automatically when the inferior begins execution, you
17004 attach to an independently started inferior, or when the dynamic linker
17005 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17006 is @code{off}, symbols must be loaded manually, using the
17007 @code{sharedlibrary} command. The default value is @code{on}.
17009 @cindex memory used for symbol tables
17010 If your program uses lots of shared libraries with debug info that
17011 takes large amounts of memory, you can decrease the @value{GDBN}
17012 memory footprint by preventing it from automatically loading the
17013 symbols from shared libraries. To that end, type @kbd{set
17014 auto-solib-add off} before running the inferior, then load each
17015 library whose debug symbols you do need with @kbd{sharedlibrary
17016 @var{regexp}}, where @var{regexp} is a regular expression that matches
17017 the libraries whose symbols you want to be loaded.
17019 @kindex show auto-solib-add
17020 @item show auto-solib-add
17021 Display the current autoloading mode.
17024 @cindex load shared library
17025 To explicitly load shared library symbols, use the @code{sharedlibrary}
17029 @kindex info sharedlibrary
17031 @item info share @var{regex}
17032 @itemx info sharedlibrary @var{regex}
17033 Print the names of the shared libraries which are currently loaded
17034 that match @var{regex}. If @var{regex} is omitted then print
17035 all shared libraries that are loaded.
17037 @kindex sharedlibrary
17039 @item sharedlibrary @var{regex}
17040 @itemx share @var{regex}
17041 Load shared object library symbols for files matching a
17042 Unix regular expression.
17043 As with files loaded automatically, it only loads shared libraries
17044 required by your program for a core file or after typing @code{run}. If
17045 @var{regex} is omitted all shared libraries required by your program are
17048 @item nosharedlibrary
17049 @kindex nosharedlibrary
17050 @cindex unload symbols from shared libraries
17051 Unload all shared object library symbols. This discards all symbols
17052 that have been loaded from all shared libraries. Symbols from shared
17053 libraries that were loaded by explicit user requests are not
17057 Sometimes you may wish that @value{GDBN} stops and gives you control
17058 when any of shared library events happen. The best way to do this is
17059 to use @code{catch load} and @code{catch unload} (@pxref{Set
17062 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17063 command for this. This command exists for historical reasons. It is
17064 less useful than setting a catchpoint, because it does not allow for
17065 conditions or commands as a catchpoint does.
17068 @item set stop-on-solib-events
17069 @kindex set stop-on-solib-events
17070 This command controls whether @value{GDBN} should give you control
17071 when the dynamic linker notifies it about some shared library event.
17072 The most common event of interest is loading or unloading of a new
17075 @item show stop-on-solib-events
17076 @kindex show stop-on-solib-events
17077 Show whether @value{GDBN} stops and gives you control when shared
17078 library events happen.
17081 Shared libraries are also supported in many cross or remote debugging
17082 configurations. @value{GDBN} needs to have access to the target's libraries;
17083 this can be accomplished either by providing copies of the libraries
17084 on the host system, or by asking @value{GDBN} to automatically retrieve the
17085 libraries from the target. If copies of the target libraries are
17086 provided, they need to be the same as the target libraries, although the
17087 copies on the target can be stripped as long as the copies on the host are
17090 @cindex where to look for shared libraries
17091 For remote debugging, you need to tell @value{GDBN} where the target
17092 libraries are, so that it can load the correct copies---otherwise, it
17093 may try to load the host's libraries. @value{GDBN} has two variables
17094 to specify the search directories for target libraries.
17097 @cindex prefix for shared library file names
17098 @cindex system root, alternate
17099 @kindex set solib-absolute-prefix
17100 @kindex set sysroot
17101 @item set sysroot @var{path}
17102 Use @var{path} as the system root for the program being debugged. Any
17103 absolute shared library paths will be prefixed with @var{path}; many
17104 runtime loaders store the absolute paths to the shared library in the
17105 target program's memory. If you use @code{set sysroot} to find shared
17106 libraries, they need to be laid out in the same way that they are on
17107 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17110 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17111 retrieve the target libraries from the remote system. This is only
17112 supported when using a remote target that supports the @code{remote get}
17113 command (@pxref{File Transfer,,Sending files to a remote system}).
17114 The part of @var{path} following the initial @file{remote:}
17115 (if present) is used as system root prefix on the remote file system.
17116 @footnote{If you want to specify a local system root using a directory
17117 that happens to be named @file{remote:}, you need to use some equivalent
17118 variant of the name like @file{./remote:}.}
17120 For targets with an MS-DOS based filesystem, such as MS-Windows and
17121 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17122 absolute file name with @var{path}. But first, on Unix hosts,
17123 @value{GDBN} converts all backslash directory separators into forward
17124 slashes, because the backslash is not a directory separator on Unix:
17127 c:\foo\bar.dll @result{} c:/foo/bar.dll
17130 Then, @value{GDBN} attempts prefixing the target file name with
17131 @var{path}, and looks for the resulting file name in the host file
17135 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17138 If that does not find the shared library, @value{GDBN} tries removing
17139 the @samp{:} character from the drive spec, both for convenience, and,
17140 for the case of the host file system not supporting file names with
17144 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17147 This makes it possible to have a system root that mirrors a target
17148 with more than one drive. E.g., you may want to setup your local
17149 copies of the target system shared libraries like so (note @samp{c} vs
17153 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17154 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17155 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17159 and point the system root at @file{/path/to/sysroot}, so that
17160 @value{GDBN} can find the correct copies of both
17161 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17163 If that still does not find the shared library, @value{GDBN} tries
17164 removing the whole drive spec from the target file name:
17167 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17170 This last lookup makes it possible to not care about the drive name,
17171 if you don't want or need to.
17173 The @code{set solib-absolute-prefix} command is an alias for @code{set
17176 @cindex default system root
17177 @cindex @samp{--with-sysroot}
17178 You can set the default system root by using the configure-time
17179 @samp{--with-sysroot} option. If the system root is inside
17180 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17181 @samp{--exec-prefix}), then the default system root will be updated
17182 automatically if the installed @value{GDBN} is moved to a new
17185 @kindex show sysroot
17187 Display the current shared library prefix.
17189 @kindex set solib-search-path
17190 @item set solib-search-path @var{path}
17191 If this variable is set, @var{path} is a colon-separated list of
17192 directories to search for shared libraries. @samp{solib-search-path}
17193 is used after @samp{sysroot} fails to locate the library, or if the
17194 path to the library is relative instead of absolute. If you want to
17195 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17196 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17197 finding your host's libraries. @samp{sysroot} is preferred; setting
17198 it to a nonexistent directory may interfere with automatic loading
17199 of shared library symbols.
17201 @kindex show solib-search-path
17202 @item show solib-search-path
17203 Display the current shared library search path.
17205 @cindex DOS file-name semantics of file names.
17206 @kindex set target-file-system-kind (unix|dos-based|auto)
17207 @kindex show target-file-system-kind
17208 @item set target-file-system-kind @var{kind}
17209 Set assumed file system kind for target reported file names.
17211 Shared library file names as reported by the target system may not
17212 make sense as is on the system @value{GDBN} is running on. For
17213 example, when remote debugging a target that has MS-DOS based file
17214 system semantics, from a Unix host, the target may be reporting to
17215 @value{GDBN} a list of loaded shared libraries with file names such as
17216 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17217 drive letters, so the @samp{c:\} prefix is not normally understood as
17218 indicating an absolute file name, and neither is the backslash
17219 normally considered a directory separator character. In that case,
17220 the native file system would interpret this whole absolute file name
17221 as a relative file name with no directory components. This would make
17222 it impossible to point @value{GDBN} at a copy of the remote target's
17223 shared libraries on the host using @code{set sysroot}, and impractical
17224 with @code{set solib-search-path}. Setting
17225 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17226 to interpret such file names similarly to how the target would, and to
17227 map them to file names valid on @value{GDBN}'s native file system
17228 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17229 to one of the supported file system kinds. In that case, @value{GDBN}
17230 tries to determine the appropriate file system variant based on the
17231 current target's operating system (@pxref{ABI, ,Configuring the
17232 Current ABI}). The supported file system settings are:
17236 Instruct @value{GDBN} to assume the target file system is of Unix
17237 kind. Only file names starting the forward slash (@samp{/}) character
17238 are considered absolute, and the directory separator character is also
17242 Instruct @value{GDBN} to assume the target file system is DOS based.
17243 File names starting with either a forward slash, or a drive letter
17244 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17245 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17246 considered directory separators.
17249 Instruct @value{GDBN} to use the file system kind associated with the
17250 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17251 This is the default.
17255 @cindex file name canonicalization
17256 @cindex base name differences
17257 When processing file names provided by the user, @value{GDBN}
17258 frequently needs to compare them to the file names recorded in the
17259 program's debug info. Normally, @value{GDBN} compares just the
17260 @dfn{base names} of the files as strings, which is reasonably fast
17261 even for very large programs. (The base name of a file is the last
17262 portion of its name, after stripping all the leading directories.)
17263 This shortcut in comparison is based upon the assumption that files
17264 cannot have more than one base name. This is usually true, but
17265 references to files that use symlinks or similar filesystem
17266 facilities violate that assumption. If your program records files
17267 using such facilities, or if you provide file names to @value{GDBN}
17268 using symlinks etc., you can set @code{basenames-may-differ} to
17269 @code{true} to instruct @value{GDBN} to completely canonicalize each
17270 pair of file names it needs to compare. This will make file-name
17271 comparisons accurate, but at a price of a significant slowdown.
17274 @item set basenames-may-differ
17275 @kindex set basenames-may-differ
17276 Set whether a source file may have multiple base names.
17278 @item show basenames-may-differ
17279 @kindex show basenames-may-differ
17280 Show whether a source file may have multiple base names.
17283 @node Separate Debug Files
17284 @section Debugging Information in Separate Files
17285 @cindex separate debugging information files
17286 @cindex debugging information in separate files
17287 @cindex @file{.debug} subdirectories
17288 @cindex debugging information directory, global
17289 @cindex global debugging information directories
17290 @cindex build ID, and separate debugging files
17291 @cindex @file{.build-id} directory
17293 @value{GDBN} allows you to put a program's debugging information in a
17294 file separate from the executable itself, in a way that allows
17295 @value{GDBN} to find and load the debugging information automatically.
17296 Since debugging information can be very large---sometimes larger
17297 than the executable code itself---some systems distribute debugging
17298 information for their executables in separate files, which users can
17299 install only when they need to debug a problem.
17301 @value{GDBN} supports two ways of specifying the separate debug info
17306 The executable contains a @dfn{debug link} that specifies the name of
17307 the separate debug info file. The separate debug file's name is
17308 usually @file{@var{executable}.debug}, where @var{executable} is the
17309 name of the corresponding executable file without leading directories
17310 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17311 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17312 checksum for the debug file, which @value{GDBN} uses to validate that
17313 the executable and the debug file came from the same build.
17316 The executable contains a @dfn{build ID}, a unique bit string that is
17317 also present in the corresponding debug info file. (This is supported
17318 only on some operating systems, notably those which use the ELF format
17319 for binary files and the @sc{gnu} Binutils.) For more details about
17320 this feature, see the description of the @option{--build-id}
17321 command-line option in @ref{Options, , Command Line Options, ld.info,
17322 The GNU Linker}. The debug info file's name is not specified
17323 explicitly by the build ID, but can be computed from the build ID, see
17327 Depending on the way the debug info file is specified, @value{GDBN}
17328 uses two different methods of looking for the debug file:
17332 For the ``debug link'' method, @value{GDBN} looks up the named file in
17333 the directory of the executable file, then in a subdirectory of that
17334 directory named @file{.debug}, and finally under each one of the global debug
17335 directories, in a subdirectory whose name is identical to the leading
17336 directories of the executable's absolute file name.
17339 For the ``build ID'' method, @value{GDBN} looks in the
17340 @file{.build-id} subdirectory of each one of the global debug directories for
17341 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17342 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17343 are the rest of the bit string. (Real build ID strings are 32 or more
17344 hex characters, not 10.)
17347 So, for example, suppose you ask @value{GDBN} to debug
17348 @file{/usr/bin/ls}, which has a debug link that specifies the
17349 file @file{ls.debug}, and a build ID whose value in hex is
17350 @code{abcdef1234}. If the list of the global debug directories includes
17351 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17352 debug information files, in the indicated order:
17356 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17358 @file{/usr/bin/ls.debug}
17360 @file{/usr/bin/.debug/ls.debug}
17362 @file{/usr/lib/debug/usr/bin/ls.debug}.
17365 @anchor{debug-file-directory}
17366 Global debugging info directories default to what is set by @value{GDBN}
17367 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17368 you can also set the global debugging info directories, and view the list
17369 @value{GDBN} is currently using.
17373 @kindex set debug-file-directory
17374 @item set debug-file-directory @var{directories}
17375 Set the directories which @value{GDBN} searches for separate debugging
17376 information files to @var{directory}. Multiple path components can be set
17377 concatenating them by a path separator.
17379 @kindex show debug-file-directory
17380 @item show debug-file-directory
17381 Show the directories @value{GDBN} searches for separate debugging
17386 @cindex @code{.gnu_debuglink} sections
17387 @cindex debug link sections
17388 A debug link is a special section of the executable file named
17389 @code{.gnu_debuglink}. The section must contain:
17393 A filename, with any leading directory components removed, followed by
17396 zero to three bytes of padding, as needed to reach the next four-byte
17397 boundary within the section, and
17399 a four-byte CRC checksum, stored in the same endianness used for the
17400 executable file itself. The checksum is computed on the debugging
17401 information file's full contents by the function given below, passing
17402 zero as the @var{crc} argument.
17405 Any executable file format can carry a debug link, as long as it can
17406 contain a section named @code{.gnu_debuglink} with the contents
17409 @cindex @code{.note.gnu.build-id} sections
17410 @cindex build ID sections
17411 The build ID is a special section in the executable file (and in other
17412 ELF binary files that @value{GDBN} may consider). This section is
17413 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17414 It contains unique identification for the built files---the ID remains
17415 the same across multiple builds of the same build tree. The default
17416 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17417 content for the build ID string. The same section with an identical
17418 value is present in the original built binary with symbols, in its
17419 stripped variant, and in the separate debugging information file.
17421 The debugging information file itself should be an ordinary
17422 executable, containing a full set of linker symbols, sections, and
17423 debugging information. The sections of the debugging information file
17424 should have the same names, addresses, and sizes as the original file,
17425 but they need not contain any data---much like a @code{.bss} section
17426 in an ordinary executable.
17428 The @sc{gnu} binary utilities (Binutils) package includes the
17429 @samp{objcopy} utility that can produce
17430 the separated executable / debugging information file pairs using the
17431 following commands:
17434 @kbd{objcopy --only-keep-debug foo foo.debug}
17439 These commands remove the debugging
17440 information from the executable file @file{foo} and place it in the file
17441 @file{foo.debug}. You can use the first, second or both methods to link the
17446 The debug link method needs the following additional command to also leave
17447 behind a debug link in @file{foo}:
17450 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17453 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17454 a version of the @code{strip} command such that the command @kbd{strip foo -f
17455 foo.debug} has the same functionality as the two @code{objcopy} commands and
17456 the @code{ln -s} command above, together.
17459 Build ID gets embedded into the main executable using @code{ld --build-id} or
17460 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17461 compatibility fixes for debug files separation are present in @sc{gnu} binary
17462 utilities (Binutils) package since version 2.18.
17467 @cindex CRC algorithm definition
17468 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
17469 IEEE 802.3 using the polynomial:
17471 @c TexInfo requires naked braces for multi-digit exponents for Tex
17472 @c output, but this causes HTML output to barf. HTML has to be set using
17473 @c raw commands. So we end up having to specify this equation in 2
17478 <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>
17479 + <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
17485 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
17486 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
17490 The function is computed byte at a time, taking the least
17491 significant bit of each byte first. The initial pattern
17492 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
17493 the final result is inverted to ensure trailing zeros also affect the
17496 @emph{Note:} This is the same CRC polynomial as used in handling the
17497 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
17498 , @value{GDBN} Remote Serial Protocol}). However in the
17499 case of the Remote Serial Protocol, the CRC is computed @emph{most}
17500 significant bit first, and the result is not inverted, so trailing
17501 zeros have no effect on the CRC value.
17503 To complete the description, we show below the code of the function
17504 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
17505 initially supplied @code{crc} argument means that an initial call to
17506 this function passing in zero will start computing the CRC using
17509 @kindex gnu_debuglink_crc32
17512 gnu_debuglink_crc32 (unsigned long crc,
17513 unsigned char *buf, size_t len)
17515 static const unsigned long crc32_table[256] =
17517 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17518 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17519 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17520 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17521 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17522 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17523 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17524 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17525 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17526 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17527 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17528 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17529 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17530 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17531 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17532 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17533 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17534 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17535 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17536 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17537 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17538 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17539 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17540 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17541 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17542 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17543 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17544 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17545 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17546 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17547 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17548 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17549 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17550 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17551 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17552 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17553 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17554 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17555 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17556 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17557 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17558 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17559 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17560 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17561 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17562 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17563 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17564 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17565 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17566 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17567 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17570 unsigned char *end;
17572 crc = ~crc & 0xffffffff;
17573 for (end = buf + len; buf < end; ++buf)
17574 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17575 return ~crc & 0xffffffff;
17580 This computation does not apply to the ``build ID'' method.
17582 @node MiniDebugInfo
17583 @section Debugging information in a special section
17584 @cindex separate debug sections
17585 @cindex @samp{.gnu_debugdata} section
17587 Some systems ship pre-built executables and libraries that have a
17588 special @samp{.gnu_debugdata} section. This feature is called
17589 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17590 is used to supply extra symbols for backtraces.
17592 The intent of this section is to provide extra minimal debugging
17593 information for use in simple backtraces. It is not intended to be a
17594 replacement for full separate debugging information (@pxref{Separate
17595 Debug Files}). The example below shows the intended use; however,
17596 @value{GDBN} does not currently put restrictions on what sort of
17597 debugging information might be included in the section.
17599 @value{GDBN} has support for this extension. If the section exists,
17600 then it is used provided that no other source of debugging information
17601 can be found, and that @value{GDBN} was configured with LZMA support.
17603 This section can be easily created using @command{objcopy} and other
17604 standard utilities:
17607 # Extract the dynamic symbols from the main binary, there is no need
17608 # to also have these in the normal symbol table.
17609 nm -D @var{binary} --format=posix --defined-only \
17610 | awk '@{ print $1 @}' | sort > dynsyms
17612 # Extract all the text (i.e. function) symbols from the debuginfo.
17613 # (Note that we actually also accept "D" symbols, for the benefit
17614 # of platforms like PowerPC64 that use function descriptors.)
17615 nm @var{binary} --format=posix --defined-only \
17616 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
17619 # Keep all the function symbols not already in the dynamic symbol
17621 comm -13 dynsyms funcsyms > keep_symbols
17623 # Separate full debug info into debug binary.
17624 objcopy --only-keep-debug @var{binary} debug
17626 # Copy the full debuginfo, keeping only a minimal set of symbols and
17627 # removing some unnecessary sections.
17628 objcopy -S --remove-section .gdb_index --remove-section .comment \
17629 --keep-symbols=keep_symbols debug mini_debuginfo
17631 # Drop the full debug info from the original binary.
17632 strip --strip-all -R .comment @var{binary}
17634 # Inject the compressed data into the .gnu_debugdata section of the
17637 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17641 @section Index Files Speed Up @value{GDBN}
17642 @cindex index files
17643 @cindex @samp{.gdb_index} section
17645 When @value{GDBN} finds a symbol file, it scans the symbols in the
17646 file in order to construct an internal symbol table. This lets most
17647 @value{GDBN} operations work quickly---at the cost of a delay early
17648 on. For large programs, this delay can be quite lengthy, so
17649 @value{GDBN} provides a way to build an index, which speeds up
17652 The index is stored as a section in the symbol file. @value{GDBN} can
17653 write the index to a file, then you can put it into the symbol file
17654 using @command{objcopy}.
17656 To create an index file, use the @code{save gdb-index} command:
17659 @item save gdb-index @var{directory}
17660 @kindex save gdb-index
17661 Create an index file for each symbol file currently known by
17662 @value{GDBN}. Each file is named after its corresponding symbol file,
17663 with @samp{.gdb-index} appended, and is written into the given
17667 Once you have created an index file you can merge it into your symbol
17668 file, here named @file{symfile}, using @command{objcopy}:
17671 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17672 --set-section-flags .gdb_index=readonly symfile symfile
17675 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17676 sections that have been deprecated. Usually they are deprecated because
17677 they are missing a new feature or have performance issues.
17678 To tell @value{GDBN} to use a deprecated index section anyway
17679 specify @code{set use-deprecated-index-sections on}.
17680 The default is @code{off}.
17681 This can speed up startup, but may result in some functionality being lost.
17682 @xref{Index Section Format}.
17684 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17685 must be done before gdb reads the file. The following will not work:
17688 $ gdb -ex "set use-deprecated-index-sections on" <program>
17691 Instead you must do, for example,
17694 $ gdb -iex "set use-deprecated-index-sections on" <program>
17697 There are currently some limitation on indices. They only work when
17698 for DWARF debugging information, not stabs. And, they do not
17699 currently work for programs using Ada.
17701 @node Symbol Errors
17702 @section Errors Reading Symbol Files
17704 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17705 such as symbol types it does not recognize, or known bugs in compiler
17706 output. By default, @value{GDBN} does not notify you of such problems, since
17707 they are relatively common and primarily of interest to people
17708 debugging compilers. If you are interested in seeing information
17709 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17710 only one message about each such type of problem, no matter how many
17711 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17712 to see how many times the problems occur, with the @code{set
17713 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17716 The messages currently printed, and their meanings, include:
17719 @item inner block not inside outer block in @var{symbol}
17721 The symbol information shows where symbol scopes begin and end
17722 (such as at the start of a function or a block of statements). This
17723 error indicates that an inner scope block is not fully contained
17724 in its outer scope blocks.
17726 @value{GDBN} circumvents the problem by treating the inner block as if it had
17727 the same scope as the outer block. In the error message, @var{symbol}
17728 may be shown as ``@code{(don't know)}'' if the outer block is not a
17731 @item block at @var{address} out of order
17733 The symbol information for symbol scope blocks should occur in
17734 order of increasing addresses. This error indicates that it does not
17737 @value{GDBN} does not circumvent this problem, and has trouble
17738 locating symbols in the source file whose symbols it is reading. (You
17739 can often determine what source file is affected by specifying
17740 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17743 @item bad block start address patched
17745 The symbol information for a symbol scope block has a start address
17746 smaller than the address of the preceding source line. This is known
17747 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17749 @value{GDBN} circumvents the problem by treating the symbol scope block as
17750 starting on the previous source line.
17752 @item bad string table offset in symbol @var{n}
17755 Symbol number @var{n} contains a pointer into the string table which is
17756 larger than the size of the string table.
17758 @value{GDBN} circumvents the problem by considering the symbol to have the
17759 name @code{foo}, which may cause other problems if many symbols end up
17762 @item unknown symbol type @code{0x@var{nn}}
17764 The symbol information contains new data types that @value{GDBN} does
17765 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17766 uncomprehended information, in hexadecimal.
17768 @value{GDBN} circumvents the error by ignoring this symbol information.
17769 This usually allows you to debug your program, though certain symbols
17770 are not accessible. If you encounter such a problem and feel like
17771 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17772 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17773 and examine @code{*bufp} to see the symbol.
17775 @item stub type has NULL name
17777 @value{GDBN} could not find the full definition for a struct or class.
17779 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17780 The symbol information for a C@t{++} member function is missing some
17781 information that recent versions of the compiler should have output for
17784 @item info mismatch between compiler and debugger
17786 @value{GDBN} could not parse a type specification output by the compiler.
17791 @section GDB Data Files
17793 @cindex prefix for data files
17794 @value{GDBN} will sometimes read an auxiliary data file. These files
17795 are kept in a directory known as the @dfn{data directory}.
17797 You can set the data directory's name, and view the name @value{GDBN}
17798 is currently using.
17801 @kindex set data-directory
17802 @item set data-directory @var{directory}
17803 Set the directory which @value{GDBN} searches for auxiliary data files
17804 to @var{directory}.
17806 @kindex show data-directory
17807 @item show data-directory
17808 Show the directory @value{GDBN} searches for auxiliary data files.
17811 @cindex default data directory
17812 @cindex @samp{--with-gdb-datadir}
17813 You can set the default data directory by using the configure-time
17814 @samp{--with-gdb-datadir} option. If the data directory is inside
17815 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17816 @samp{--exec-prefix}), then the default data directory will be updated
17817 automatically if the installed @value{GDBN} is moved to a new
17820 The data directory may also be specified with the
17821 @code{--data-directory} command line option.
17822 @xref{Mode Options}.
17825 @chapter Specifying a Debugging Target
17827 @cindex debugging target
17828 A @dfn{target} is the execution environment occupied by your program.
17830 Often, @value{GDBN} runs in the same host environment as your program;
17831 in that case, the debugging target is specified as a side effect when
17832 you use the @code{file} or @code{core} commands. When you need more
17833 flexibility---for example, running @value{GDBN} on a physically separate
17834 host, or controlling a standalone system over a serial port or a
17835 realtime system over a TCP/IP connection---you can use the @code{target}
17836 command to specify one of the target types configured for @value{GDBN}
17837 (@pxref{Target Commands, ,Commands for Managing Targets}).
17839 @cindex target architecture
17840 It is possible to build @value{GDBN} for several different @dfn{target
17841 architectures}. When @value{GDBN} is built like that, you can choose
17842 one of the available architectures with the @kbd{set architecture}
17846 @kindex set architecture
17847 @kindex show architecture
17848 @item set architecture @var{arch}
17849 This command sets the current target architecture to @var{arch}. The
17850 value of @var{arch} can be @code{"auto"}, in addition to one of the
17851 supported architectures.
17853 @item show architecture
17854 Show the current target architecture.
17856 @item set processor
17858 @kindex set processor
17859 @kindex show processor
17860 These are alias commands for, respectively, @code{set architecture}
17861 and @code{show architecture}.
17865 * Active Targets:: Active targets
17866 * Target Commands:: Commands for managing targets
17867 * Byte Order:: Choosing target byte order
17870 @node Active Targets
17871 @section Active Targets
17873 @cindex stacking targets
17874 @cindex active targets
17875 @cindex multiple targets
17877 There are multiple classes of targets such as: processes, executable files or
17878 recording sessions. Core files belong to the process class, making core file
17879 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17880 on multiple active targets, one in each class. This allows you to (for
17881 example) start a process and inspect its activity, while still having access to
17882 the executable file after the process finishes. Or if you start process
17883 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17884 presented a virtual layer of the recording target, while the process target
17885 remains stopped at the chronologically last point of the process execution.
17887 Use the @code{core-file} and @code{exec-file} commands to select a new core
17888 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17889 specify as a target a process that is already running, use the @code{attach}
17890 command (@pxref{Attach, ,Debugging an Already-running Process}).
17892 @node Target Commands
17893 @section Commands for Managing Targets
17896 @item target @var{type} @var{parameters}
17897 Connects the @value{GDBN} host environment to a target machine or
17898 process. A target is typically a protocol for talking to debugging
17899 facilities. You use the argument @var{type} to specify the type or
17900 protocol of the target machine.
17902 Further @var{parameters} are interpreted by the target protocol, but
17903 typically include things like device names or host names to connect
17904 with, process numbers, and baud rates.
17906 The @code{target} command does not repeat if you press @key{RET} again
17907 after executing the command.
17909 @kindex help target
17911 Displays the names of all targets available. To display targets
17912 currently selected, use either @code{info target} or @code{info files}
17913 (@pxref{Files, ,Commands to Specify Files}).
17915 @item help target @var{name}
17916 Describe a particular target, including any parameters necessary to
17919 @kindex set gnutarget
17920 @item set gnutarget @var{args}
17921 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17922 knows whether it is reading an @dfn{executable},
17923 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17924 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17925 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17928 @emph{Warning:} To specify a file format with @code{set gnutarget},
17929 you must know the actual BFD name.
17933 @xref{Files, , Commands to Specify Files}.
17935 @kindex show gnutarget
17936 @item show gnutarget
17937 Use the @code{show gnutarget} command to display what file format
17938 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17939 @value{GDBN} will determine the file format for each file automatically,
17940 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17943 @cindex common targets
17944 Here are some common targets (available, or not, depending on the GDB
17949 @item target exec @var{program}
17950 @cindex executable file target
17951 An executable file. @samp{target exec @var{program}} is the same as
17952 @samp{exec-file @var{program}}.
17954 @item target core @var{filename}
17955 @cindex core dump file target
17956 A core dump file. @samp{target core @var{filename}} is the same as
17957 @samp{core-file @var{filename}}.
17959 @item target remote @var{medium}
17960 @cindex remote target
17961 A remote system connected to @value{GDBN} via a serial line or network
17962 connection. This command tells @value{GDBN} to use its own remote
17963 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17965 For example, if you have a board connected to @file{/dev/ttya} on the
17966 machine running @value{GDBN}, you could say:
17969 target remote /dev/ttya
17972 @code{target remote} supports the @code{load} command. This is only
17973 useful if you have some other way of getting the stub to the target
17974 system, and you can put it somewhere in memory where it won't get
17975 clobbered by the download.
17977 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17978 @cindex built-in simulator target
17979 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17987 works; however, you cannot assume that a specific memory map, device
17988 drivers, or even basic I/O is available, although some simulators do
17989 provide these. For info about any processor-specific simulator details,
17990 see the appropriate section in @ref{Embedded Processors, ,Embedded
17995 Different targets are available on different configurations of @value{GDBN};
17996 your configuration may have more or fewer targets.
17998 Many remote targets require you to download the executable's code once
17999 you've successfully established a connection. You may wish to control
18000 various aspects of this process.
18005 @kindex set hash@r{, for remote monitors}
18006 @cindex hash mark while downloading
18007 This command controls whether a hash mark @samp{#} is displayed while
18008 downloading a file to the remote monitor. If on, a hash mark is
18009 displayed after each S-record is successfully downloaded to the
18013 @kindex show hash@r{, for remote monitors}
18014 Show the current status of displaying the hash mark.
18016 @item set debug monitor
18017 @kindex set debug monitor
18018 @cindex display remote monitor communications
18019 Enable or disable display of communications messages between
18020 @value{GDBN} and the remote monitor.
18022 @item show debug monitor
18023 @kindex show debug monitor
18024 Show the current status of displaying communications between
18025 @value{GDBN} and the remote monitor.
18030 @kindex load @var{filename}
18031 @item load @var{filename}
18033 Depending on what remote debugging facilities are configured into
18034 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18035 is meant to make @var{filename} (an executable) available for debugging
18036 on the remote system---by downloading, or dynamic linking, for example.
18037 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18038 the @code{add-symbol-file} command.
18040 If your @value{GDBN} does not have a @code{load} command, attempting to
18041 execute it gets the error message ``@code{You can't do that when your
18042 target is @dots{}}''
18044 The file is loaded at whatever address is specified in the executable.
18045 For some object file formats, you can specify the load address when you
18046 link the program; for other formats, like a.out, the object file format
18047 specifies a fixed address.
18048 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18050 Depending on the remote side capabilities, @value{GDBN} may be able to
18051 load programs into flash memory.
18053 @code{load} does not repeat if you press @key{RET} again after using it.
18057 @section Choosing Target Byte Order
18059 @cindex choosing target byte order
18060 @cindex target byte order
18062 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18063 offer the ability to run either big-endian or little-endian byte
18064 orders. Usually the executable or symbol will include a bit to
18065 designate the endian-ness, and you will not need to worry about
18066 which to use. However, you may still find it useful to adjust
18067 @value{GDBN}'s idea of processor endian-ness manually.
18071 @item set endian big
18072 Instruct @value{GDBN} to assume the target is big-endian.
18074 @item set endian little
18075 Instruct @value{GDBN} to assume the target is little-endian.
18077 @item set endian auto
18078 Instruct @value{GDBN} to use the byte order associated with the
18082 Display @value{GDBN}'s current idea of the target byte order.
18086 Note that these commands merely adjust interpretation of symbolic
18087 data on the host, and that they have absolutely no effect on the
18091 @node Remote Debugging
18092 @chapter Debugging Remote Programs
18093 @cindex remote debugging
18095 If you are trying to debug a program running on a machine that cannot run
18096 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18097 For example, you might use remote debugging on an operating system kernel,
18098 or on a small system which does not have a general purpose operating system
18099 powerful enough to run a full-featured debugger.
18101 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18102 to make this work with particular debugging targets. In addition,
18103 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18104 but not specific to any particular target system) which you can use if you
18105 write the remote stubs---the code that runs on the remote system to
18106 communicate with @value{GDBN}.
18108 Other remote targets may be available in your
18109 configuration of @value{GDBN}; use @code{help target} to list them.
18112 * Connecting:: Connecting to a remote target
18113 * File Transfer:: Sending files to a remote system
18114 * Server:: Using the gdbserver program
18115 * Remote Configuration:: Remote configuration
18116 * Remote Stub:: Implementing a remote stub
18120 @section Connecting to a Remote Target
18122 On the @value{GDBN} host machine, you will need an unstripped copy of
18123 your program, since @value{GDBN} needs symbol and debugging information.
18124 Start up @value{GDBN} as usual, using the name of the local copy of your
18125 program as the first argument.
18127 @cindex @code{target remote}
18128 @value{GDBN} can communicate with the target over a serial line, or
18129 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18130 each case, @value{GDBN} uses the same protocol for debugging your
18131 program; only the medium carrying the debugging packets varies. The
18132 @code{target remote} command establishes a connection to the target.
18133 Its arguments indicate which medium to use:
18137 @item target remote @var{serial-device}
18138 @cindex serial line, @code{target remote}
18139 Use @var{serial-device} to communicate with the target. For example,
18140 to use a serial line connected to the device named @file{/dev/ttyb}:
18143 target remote /dev/ttyb
18146 If you're using a serial line, you may want to give @value{GDBN} the
18147 @samp{--baud} option, or use the @code{set serial baud} command
18148 (@pxref{Remote Configuration, set serial baud}) before the
18149 @code{target} command.
18151 @item target remote @code{@var{host}:@var{port}}
18152 @itemx target remote @code{tcp:@var{host}:@var{port}}
18153 @cindex @acronym{TCP} port, @code{target remote}
18154 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18155 The @var{host} may be either a host name or a numeric @acronym{IP}
18156 address; @var{port} must be a decimal number. The @var{host} could be
18157 the target machine itself, if it is directly connected to the net, or
18158 it might be a terminal server which in turn has a serial line to the
18161 For example, to connect to port 2828 on a terminal server named
18165 target remote manyfarms:2828
18168 If your remote target is actually running on the same machine as your
18169 debugger session (e.g.@: a simulator for your target running on the
18170 same host), you can omit the hostname. For example, to connect to
18171 port 1234 on your local machine:
18174 target remote :1234
18178 Note that the colon is still required here.
18180 @item target remote @code{udp:@var{host}:@var{port}}
18181 @cindex @acronym{UDP} port, @code{target remote}
18182 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18183 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18186 target remote udp:manyfarms:2828
18189 When using a @acronym{UDP} connection for remote debugging, you should
18190 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18191 can silently drop packets on busy or unreliable networks, which will
18192 cause havoc with your debugging session.
18194 @item target remote | @var{command}
18195 @cindex pipe, @code{target remote} to
18196 Run @var{command} in the background and communicate with it using a
18197 pipe. The @var{command} is a shell command, to be parsed and expanded
18198 by the system's command shell, @code{/bin/sh}; it should expect remote
18199 protocol packets on its standard input, and send replies on its
18200 standard output. You could use this to run a stand-alone simulator
18201 that speaks the remote debugging protocol, to make net connections
18202 using programs like @code{ssh}, or for other similar tricks.
18204 If @var{command} closes its standard output (perhaps by exiting),
18205 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18206 program has already exited, this will have no effect.)
18210 Once the connection has been established, you can use all the usual
18211 commands to examine and change data. The remote program is already
18212 running; you can use @kbd{step} and @kbd{continue}, and you do not
18213 need to use @kbd{run}.
18215 @cindex interrupting remote programs
18216 @cindex remote programs, interrupting
18217 Whenever @value{GDBN} is waiting for the remote program, if you type the
18218 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18219 program. This may or may not succeed, depending in part on the hardware
18220 and the serial drivers the remote system uses. If you type the
18221 interrupt character once again, @value{GDBN} displays this prompt:
18224 Interrupted while waiting for the program.
18225 Give up (and stop debugging it)? (y or n)
18228 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18229 (If you decide you want to try again later, you can use @samp{target
18230 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18231 goes back to waiting.
18234 @kindex detach (remote)
18236 When you have finished debugging the remote program, you can use the
18237 @code{detach} command to release it from @value{GDBN} control.
18238 Detaching from the target normally resumes its execution, but the results
18239 will depend on your particular remote stub. After the @code{detach}
18240 command, @value{GDBN} is free to connect to another target.
18244 The @code{disconnect} command behaves like @code{detach}, except that
18245 the target is generally not resumed. It will wait for @value{GDBN}
18246 (this instance or another one) to connect and continue debugging. After
18247 the @code{disconnect} command, @value{GDBN} is again free to connect to
18250 @cindex send command to remote monitor
18251 @cindex extend @value{GDBN} for remote targets
18252 @cindex add new commands for external monitor
18254 @item monitor @var{cmd}
18255 This command allows you to send arbitrary commands directly to the
18256 remote monitor. Since @value{GDBN} doesn't care about the commands it
18257 sends like this, this command is the way to extend @value{GDBN}---you
18258 can add new commands that only the external monitor will understand
18262 @node File Transfer
18263 @section Sending files to a remote system
18264 @cindex remote target, file transfer
18265 @cindex file transfer
18266 @cindex sending files to remote systems
18268 Some remote targets offer the ability to transfer files over the same
18269 connection used to communicate with @value{GDBN}. This is convenient
18270 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18271 running @code{gdbserver} over a network interface. For other targets,
18272 e.g.@: embedded devices with only a single serial port, this may be
18273 the only way to upload or download files.
18275 Not all remote targets support these commands.
18279 @item remote put @var{hostfile} @var{targetfile}
18280 Copy file @var{hostfile} from the host system (the machine running
18281 @value{GDBN}) to @var{targetfile} on the target system.
18284 @item remote get @var{targetfile} @var{hostfile}
18285 Copy file @var{targetfile} from the target system to @var{hostfile}
18286 on the host system.
18288 @kindex remote delete
18289 @item remote delete @var{targetfile}
18290 Delete @var{targetfile} from the target system.
18295 @section Using the @code{gdbserver} Program
18298 @cindex remote connection without stubs
18299 @code{gdbserver} is a control program for Unix-like systems, which
18300 allows you to connect your program with a remote @value{GDBN} via
18301 @code{target remote}---but without linking in the usual debugging stub.
18303 @code{gdbserver} is not a complete replacement for the debugging stubs,
18304 because it requires essentially the same operating-system facilities
18305 that @value{GDBN} itself does. In fact, a system that can run
18306 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18307 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18308 because it is a much smaller program than @value{GDBN} itself. It is
18309 also easier to port than all of @value{GDBN}, so you may be able to get
18310 started more quickly on a new system by using @code{gdbserver}.
18311 Finally, if you develop code for real-time systems, you may find that
18312 the tradeoffs involved in real-time operation make it more convenient to
18313 do as much development work as possible on another system, for example
18314 by cross-compiling. You can use @code{gdbserver} to make a similar
18315 choice for debugging.
18317 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18318 or a TCP connection, using the standard @value{GDBN} remote serial
18322 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18323 Do not run @code{gdbserver} connected to any public network; a
18324 @value{GDBN} connection to @code{gdbserver} provides access to the
18325 target system with the same privileges as the user running
18329 @subsection Running @code{gdbserver}
18330 @cindex arguments, to @code{gdbserver}
18331 @cindex @code{gdbserver}, command-line arguments
18333 Run @code{gdbserver} on the target system. You need a copy of the
18334 program you want to debug, including any libraries it requires.
18335 @code{gdbserver} does not need your program's symbol table, so you can
18336 strip the program if necessary to save space. @value{GDBN} on the host
18337 system does all the symbol handling.
18339 To use the server, you must tell it how to communicate with @value{GDBN};
18340 the name of your program; and the arguments for your program. The usual
18344 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18347 @var{comm} is either a device name (to use a serial line), or a TCP
18348 hostname and portnumber, or @code{-} or @code{stdio} to use
18349 stdin/stdout of @code{gdbserver}.
18350 For example, to debug Emacs with the argument
18351 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18355 target> gdbserver /dev/com1 emacs foo.txt
18358 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18361 To use a TCP connection instead of a serial line:
18364 target> gdbserver host:2345 emacs foo.txt
18367 The only difference from the previous example is the first argument,
18368 specifying that you are communicating with the host @value{GDBN} via
18369 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18370 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18371 (Currently, the @samp{host} part is ignored.) You can choose any number
18372 you want for the port number as long as it does not conflict with any
18373 TCP ports already in use on the target system (for example, @code{23} is
18374 reserved for @code{telnet}).@footnote{If you choose a port number that
18375 conflicts with another service, @code{gdbserver} prints an error message
18376 and exits.} You must use the same port number with the host @value{GDBN}
18377 @code{target remote} command.
18379 The @code{stdio} connection is useful when starting @code{gdbserver}
18383 (gdb) target remote | ssh -T hostname gdbserver - hello
18386 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18387 and we don't want escape-character handling. Ssh does this by default when
18388 a command is provided, the flag is provided to make it explicit.
18389 You could elide it if you want to.
18391 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18392 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18393 display through a pipe connected to gdbserver.
18394 Both @code{stdout} and @code{stderr} use the same pipe.
18396 @subsubsection Attaching to a Running Program
18397 @cindex attach to a program, @code{gdbserver}
18398 @cindex @option{--attach}, @code{gdbserver} option
18400 On some targets, @code{gdbserver} can also attach to running programs.
18401 This is accomplished via the @code{--attach} argument. The syntax is:
18404 target> gdbserver --attach @var{comm} @var{pid}
18407 @var{pid} is the process ID of a currently running process. It isn't necessary
18408 to point @code{gdbserver} at a binary for the running process.
18411 You can debug processes by name instead of process ID if your target has the
18412 @code{pidof} utility:
18415 target> gdbserver --attach @var{comm} `pidof @var{program}`
18418 In case more than one copy of @var{program} is running, or @var{program}
18419 has multiple threads, most versions of @code{pidof} support the
18420 @code{-s} option to only return the first process ID.
18422 @subsubsection Multi-Process Mode for @code{gdbserver}
18423 @cindex @code{gdbserver}, multiple processes
18424 @cindex multiple processes with @code{gdbserver}
18426 When you connect to @code{gdbserver} using @code{target remote},
18427 @code{gdbserver} debugs the specified program only once. When the
18428 program exits, or you detach from it, @value{GDBN} closes the connection
18429 and @code{gdbserver} exits.
18431 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18432 enters multi-process mode. When the debugged program exits, or you
18433 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18434 though no program is running. The @code{run} and @code{attach}
18435 commands instruct @code{gdbserver} to run or attach to a new program.
18436 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18437 remote exec-file}) to select the program to run. Command line
18438 arguments are supported, except for wildcard expansion and I/O
18439 redirection (@pxref{Arguments}).
18441 @cindex @option{--multi}, @code{gdbserver} option
18442 To start @code{gdbserver} without supplying an initial command to run
18443 or process ID to attach, use the @option{--multi} command line option.
18444 Then you can connect using @kbd{target extended-remote} and start
18445 the program you want to debug.
18447 In multi-process mode @code{gdbserver} does not automatically exit unless you
18448 use the option @option{--once}. You can terminate it by using
18449 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18450 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18451 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18452 @option{--multi} option to @code{gdbserver} has no influence on that.
18454 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18456 This section applies only when @code{gdbserver} is run to listen on a TCP port.
18458 @code{gdbserver} normally terminates after all of its debugged processes have
18459 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
18460 extended-remote}, @code{gdbserver} stays running even with no processes left.
18461 @value{GDBN} normally terminates the spawned debugged process on its exit,
18462 which normally also terminates @code{gdbserver} in the @kbd{target remote}
18463 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
18464 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
18465 stays running even in the @kbd{target remote} mode.
18467 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
18468 Such reconnecting is useful for features like @ref{disconnected tracing}. For
18469 completeness, at most one @value{GDBN} can be connected at a time.
18471 @cindex @option{--once}, @code{gdbserver} option
18472 By default, @code{gdbserver} keeps the listening TCP port open, so that
18473 subsequent connections are possible. However, if you start @code{gdbserver}
18474 with the @option{--once} option, it will stop listening for any further
18475 connection attempts after connecting to the first @value{GDBN} session. This
18476 means no further connections to @code{gdbserver} will be possible after the
18477 first one. It also means @code{gdbserver} will terminate after the first
18478 connection with remote @value{GDBN} has closed, even for unexpectedly closed
18479 connections and even in the @kbd{target extended-remote} mode. The
18480 @option{--once} option allows reusing the same port number for connecting to
18481 multiple instances of @code{gdbserver} running on the same host, since each
18482 instance closes its port after the first connection.
18484 @subsubsection Other Command-Line Arguments for @code{gdbserver}
18486 @cindex @option{--debug}, @code{gdbserver} option
18487 The @option{--debug} option tells @code{gdbserver} to display extra
18488 status information about the debugging process.
18489 @cindex @option{--remote-debug}, @code{gdbserver} option
18490 The @option{--remote-debug} option tells @code{gdbserver} to display
18491 remote protocol debug output. These options are intended for
18492 @code{gdbserver} development and for bug reports to the developers.
18494 @cindex @option{--wrapper}, @code{gdbserver} option
18495 The @option{--wrapper} option specifies a wrapper to launch programs
18496 for debugging. The option should be followed by the name of the
18497 wrapper, then any command-line arguments to pass to the wrapper, then
18498 @kbd{--} indicating the end of the wrapper arguments.
18500 @code{gdbserver} runs the specified wrapper program with a combined
18501 command line including the wrapper arguments, then the name of the
18502 program to debug, then any arguments to the program. The wrapper
18503 runs until it executes your program, and then @value{GDBN} gains control.
18505 You can use any program that eventually calls @code{execve} with
18506 its arguments as a wrapper. Several standard Unix utilities do
18507 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18508 with @code{exec "$@@"} will also work.
18510 For example, you can use @code{env} to pass an environment variable to
18511 the debugged program, without setting the variable in @code{gdbserver}'s
18515 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18518 @subsection Connecting to @code{gdbserver}
18520 Run @value{GDBN} on the host system.
18522 First make sure you have the necessary symbol files. Load symbols for
18523 your application using the @code{file} command before you connect. Use
18524 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18525 was compiled with the correct sysroot using @code{--with-sysroot}).
18527 The symbol file and target libraries must exactly match the executable
18528 and libraries on the target, with one exception: the files on the host
18529 system should not be stripped, even if the files on the target system
18530 are. Mismatched or missing files will lead to confusing results
18531 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18532 files may also prevent @code{gdbserver} from debugging multi-threaded
18535 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18536 For TCP connections, you must start up @code{gdbserver} prior to using
18537 the @code{target remote} command. Otherwise you may get an error whose
18538 text depends on the host system, but which usually looks something like
18539 @samp{Connection refused}. Don't use the @code{load}
18540 command in @value{GDBN} when using @code{gdbserver}, since the program is
18541 already on the target.
18543 @subsection Monitor Commands for @code{gdbserver}
18544 @cindex monitor commands, for @code{gdbserver}
18545 @anchor{Monitor Commands for gdbserver}
18547 During a @value{GDBN} session using @code{gdbserver}, you can use the
18548 @code{monitor} command to send special requests to @code{gdbserver}.
18549 Here are the available commands.
18553 List the available monitor commands.
18555 @item monitor set debug 0
18556 @itemx monitor set debug 1
18557 Disable or enable general debugging messages.
18559 @item monitor set remote-debug 0
18560 @itemx monitor set remote-debug 1
18561 Disable or enable specific debugging messages associated with the remote
18562 protocol (@pxref{Remote Protocol}).
18564 @item monitor set libthread-db-search-path [PATH]
18565 @cindex gdbserver, search path for @code{libthread_db}
18566 When this command is issued, @var{path} is a colon-separated list of
18567 directories to search for @code{libthread_db} (@pxref{Threads,,set
18568 libthread-db-search-path}). If you omit @var{path},
18569 @samp{libthread-db-search-path} will be reset to its default value.
18571 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18572 not supported in @code{gdbserver}.
18575 Tell gdbserver to exit immediately. This command should be followed by
18576 @code{disconnect} to close the debugging session. @code{gdbserver} will
18577 detach from any attached processes and kill any processes it created.
18578 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18579 of a multi-process mode debug session.
18583 @subsection Tracepoints support in @code{gdbserver}
18584 @cindex tracepoints support in @code{gdbserver}
18586 On some targets, @code{gdbserver} supports tracepoints, fast
18587 tracepoints and static tracepoints.
18589 For fast or static tracepoints to work, a special library called the
18590 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18591 This library is built and distributed as an integral part of
18592 @code{gdbserver}. In addition, support for static tracepoints
18593 requires building the in-process agent library with static tracepoints
18594 support. At present, the UST (LTTng Userspace Tracer,
18595 @url{http://lttng.org/ust}) tracing engine is supported. This support
18596 is automatically available if UST development headers are found in the
18597 standard include path when @code{gdbserver} is built, or if
18598 @code{gdbserver} was explicitly configured using @option{--with-ust}
18599 to point at such headers. You can explicitly disable the support
18600 using @option{--with-ust=no}.
18602 There are several ways to load the in-process agent in your program:
18605 @item Specifying it as dependency at link time
18607 You can link your program dynamically with the in-process agent
18608 library. On most systems, this is accomplished by adding
18609 @code{-linproctrace} to the link command.
18611 @item Using the system's preloading mechanisms
18613 You can force loading the in-process agent at startup time by using
18614 your system's support for preloading shared libraries. Many Unixes
18615 support the concept of preloading user defined libraries. In most
18616 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18617 in the environment. See also the description of @code{gdbserver}'s
18618 @option{--wrapper} command line option.
18620 @item Using @value{GDBN} to force loading the agent at run time
18622 On some systems, you can force the inferior to load a shared library,
18623 by calling a dynamic loader function in the inferior that takes care
18624 of dynamically looking up and loading a shared library. On most Unix
18625 systems, the function is @code{dlopen}. You'll use the @code{call}
18626 command for that. For example:
18629 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18632 Note that on most Unix systems, for the @code{dlopen} function to be
18633 available, the program needs to be linked with @code{-ldl}.
18636 On systems that have a userspace dynamic loader, like most Unix
18637 systems, when you connect to @code{gdbserver} using @code{target
18638 remote}, you'll find that the program is stopped at the dynamic
18639 loader's entry point, and no shared library has been loaded in the
18640 program's address space yet, including the in-process agent. In that
18641 case, before being able to use any of the fast or static tracepoints
18642 features, you need to let the loader run and load the shared
18643 libraries. The simplest way to do that is to run the program to the
18644 main procedure. E.g., if debugging a C or C@t{++} program, start
18645 @code{gdbserver} like so:
18648 $ gdbserver :9999 myprogram
18651 Start GDB and connect to @code{gdbserver} like so, and run to main:
18655 (@value{GDBP}) target remote myhost:9999
18656 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18657 (@value{GDBP}) b main
18658 (@value{GDBP}) continue
18661 The in-process tracing agent library should now be loaded into the
18662 process; you can confirm it with the @code{info sharedlibrary}
18663 command, which will list @file{libinproctrace.so} as loaded in the
18664 process. You are now ready to install fast tracepoints, list static
18665 tracepoint markers, probe static tracepoints markers, and start
18668 @node Remote Configuration
18669 @section Remote Configuration
18672 @kindex show remote
18673 This section documents the configuration options available when
18674 debugging remote programs. For the options related to the File I/O
18675 extensions of the remote protocol, see @ref{system,
18676 system-call-allowed}.
18679 @item set remoteaddresssize @var{bits}
18680 @cindex address size for remote targets
18681 @cindex bits in remote address
18682 Set the maximum size of address in a memory packet to the specified
18683 number of bits. @value{GDBN} will mask off the address bits above
18684 that number, when it passes addresses to the remote target. The
18685 default value is the number of bits in the target's address.
18687 @item show remoteaddresssize
18688 Show the current value of remote address size in bits.
18690 @item set serial baud @var{n}
18691 @cindex baud rate for remote targets
18692 Set the baud rate for the remote serial I/O to @var{n} baud. The
18693 value is used to set the speed of the serial port used for debugging
18696 @item show serial baud
18697 Show the current speed of the remote connection.
18699 @item set remotebreak
18700 @cindex interrupt remote programs
18701 @cindex BREAK signal instead of Ctrl-C
18702 @anchor{set remotebreak}
18703 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18704 when you type @kbd{Ctrl-c} to interrupt the program running
18705 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18706 character instead. The default is off, since most remote systems
18707 expect to see @samp{Ctrl-C} as the interrupt signal.
18709 @item show remotebreak
18710 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18711 interrupt the remote program.
18713 @item set remoteflow on
18714 @itemx set remoteflow off
18715 @kindex set remoteflow
18716 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18717 on the serial port used to communicate to the remote target.
18719 @item show remoteflow
18720 @kindex show remoteflow
18721 Show the current setting of hardware flow control.
18723 @item set remotelogbase @var{base}
18724 Set the base (a.k.a.@: radix) of logging serial protocol
18725 communications to @var{base}. Supported values of @var{base} are:
18726 @code{ascii}, @code{octal}, and @code{hex}. The default is
18729 @item show remotelogbase
18730 Show the current setting of the radix for logging remote serial
18733 @item set remotelogfile @var{file}
18734 @cindex record serial communications on file
18735 Record remote serial communications on the named @var{file}. The
18736 default is not to record at all.
18738 @item show remotelogfile.
18739 Show the current setting of the file name on which to record the
18740 serial communications.
18742 @item set remotetimeout @var{num}
18743 @cindex timeout for serial communications
18744 @cindex remote timeout
18745 Set the timeout limit to wait for the remote target to respond to
18746 @var{num} seconds. The default is 2 seconds.
18748 @item show remotetimeout
18749 Show the current number of seconds to wait for the remote target
18752 @cindex limit hardware breakpoints and watchpoints
18753 @cindex remote target, limit break- and watchpoints
18754 @anchor{set remote hardware-watchpoint-limit}
18755 @anchor{set remote hardware-breakpoint-limit}
18756 @item set remote hardware-watchpoint-limit @var{limit}
18757 @itemx set remote hardware-breakpoint-limit @var{limit}
18758 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18759 watchpoints. A limit of -1, the default, is treated as unlimited.
18761 @cindex limit hardware watchpoints length
18762 @cindex remote target, limit watchpoints length
18763 @anchor{set remote hardware-watchpoint-length-limit}
18764 @item set remote hardware-watchpoint-length-limit @var{limit}
18765 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18766 a remote hardware watchpoint. A limit of -1, the default, is treated
18769 @item show remote hardware-watchpoint-length-limit
18770 Show the current limit (in bytes) of the maximum length of
18771 a remote hardware watchpoint.
18773 @item set remote exec-file @var{filename}
18774 @itemx show remote exec-file
18775 @anchor{set remote exec-file}
18776 @cindex executable file, for remote target
18777 Select the file used for @code{run} with @code{target
18778 extended-remote}. This should be set to a filename valid on the
18779 target system. If it is not set, the target will use a default
18780 filename (e.g.@: the last program run).
18782 @item set remote interrupt-sequence
18783 @cindex interrupt remote programs
18784 @cindex select Ctrl-C, BREAK or BREAK-g
18785 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18786 @samp{BREAK-g} as the
18787 sequence to the remote target in order to interrupt the execution.
18788 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18789 is high level of serial line for some certain time.
18790 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18791 It is @code{BREAK} signal followed by character @code{g}.
18793 @item show interrupt-sequence
18794 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18795 is sent by @value{GDBN} to interrupt the remote program.
18796 @code{BREAK-g} is BREAK signal followed by @code{g} and
18797 also known as Magic SysRq g.
18799 @item set remote interrupt-on-connect
18800 @cindex send interrupt-sequence on start
18801 Specify whether interrupt-sequence is sent to remote target when
18802 @value{GDBN} connects to it. This is mostly needed when you debug
18803 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18804 which is known as Magic SysRq g in order to connect @value{GDBN}.
18806 @item show interrupt-on-connect
18807 Show whether interrupt-sequence is sent
18808 to remote target when @value{GDBN} connects to it.
18812 @item set tcp auto-retry on
18813 @cindex auto-retry, for remote TCP target
18814 Enable auto-retry for remote TCP connections. This is useful if the remote
18815 debugging agent is launched in parallel with @value{GDBN}; there is a race
18816 condition because the agent may not become ready to accept the connection
18817 before @value{GDBN} attempts to connect. When auto-retry is
18818 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18819 to establish the connection using the timeout specified by
18820 @code{set tcp connect-timeout}.
18822 @item set tcp auto-retry off
18823 Do not auto-retry failed TCP connections.
18825 @item show tcp auto-retry
18826 Show the current auto-retry setting.
18828 @item set tcp connect-timeout @var{seconds}
18829 @itemx set tcp connect-timeout unlimited
18830 @cindex connection timeout, for remote TCP target
18831 @cindex timeout, for remote target connection
18832 Set the timeout for establishing a TCP connection to the remote target to
18833 @var{seconds}. The timeout affects both polling to retry failed connections
18834 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18835 that are merely slow to complete, and represents an approximate cumulative
18836 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18837 @value{GDBN} will keep attempting to establish a connection forever,
18838 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18840 @item show tcp connect-timeout
18841 Show the current connection timeout setting.
18844 @cindex remote packets, enabling and disabling
18845 The @value{GDBN} remote protocol autodetects the packets supported by
18846 your debugging stub. If you need to override the autodetection, you
18847 can use these commands to enable or disable individual packets. Each
18848 packet can be set to @samp{on} (the remote target supports this
18849 packet), @samp{off} (the remote target does not support this packet),
18850 or @samp{auto} (detect remote target support for this packet). They
18851 all default to @samp{auto}. For more information about each packet,
18852 see @ref{Remote Protocol}.
18854 During normal use, you should not have to use any of these commands.
18855 If you do, that may be a bug in your remote debugging stub, or a bug
18856 in @value{GDBN}. You may want to report the problem to the
18857 @value{GDBN} developers.
18859 For each packet @var{name}, the command to enable or disable the
18860 packet is @code{set remote @var{name}-packet}. The available settings
18863 @multitable @columnfractions 0.28 0.32 0.25
18866 @tab Related Features
18868 @item @code{fetch-register}
18870 @tab @code{info registers}
18872 @item @code{set-register}
18876 @item @code{binary-download}
18878 @tab @code{load}, @code{set}
18880 @item @code{read-aux-vector}
18881 @tab @code{qXfer:auxv:read}
18882 @tab @code{info auxv}
18884 @item @code{symbol-lookup}
18885 @tab @code{qSymbol}
18886 @tab Detecting multiple threads
18888 @item @code{attach}
18889 @tab @code{vAttach}
18892 @item @code{verbose-resume}
18894 @tab Stepping or resuming multiple threads
18900 @item @code{software-breakpoint}
18904 @item @code{hardware-breakpoint}
18908 @item @code{write-watchpoint}
18912 @item @code{read-watchpoint}
18916 @item @code{access-watchpoint}
18920 @item @code{target-features}
18921 @tab @code{qXfer:features:read}
18922 @tab @code{set architecture}
18924 @item @code{library-info}
18925 @tab @code{qXfer:libraries:read}
18926 @tab @code{info sharedlibrary}
18928 @item @code{memory-map}
18929 @tab @code{qXfer:memory-map:read}
18930 @tab @code{info mem}
18932 @item @code{read-sdata-object}
18933 @tab @code{qXfer:sdata:read}
18934 @tab @code{print $_sdata}
18936 @item @code{read-spu-object}
18937 @tab @code{qXfer:spu:read}
18938 @tab @code{info spu}
18940 @item @code{write-spu-object}
18941 @tab @code{qXfer:spu:write}
18942 @tab @code{info spu}
18944 @item @code{read-siginfo-object}
18945 @tab @code{qXfer:siginfo:read}
18946 @tab @code{print $_siginfo}
18948 @item @code{write-siginfo-object}
18949 @tab @code{qXfer:siginfo:write}
18950 @tab @code{set $_siginfo}
18952 @item @code{threads}
18953 @tab @code{qXfer:threads:read}
18954 @tab @code{info threads}
18956 @item @code{get-thread-local-@*storage-address}
18957 @tab @code{qGetTLSAddr}
18958 @tab Displaying @code{__thread} variables
18960 @item @code{get-thread-information-block-address}
18961 @tab @code{qGetTIBAddr}
18962 @tab Display MS-Windows Thread Information Block.
18964 @item @code{search-memory}
18965 @tab @code{qSearch:memory}
18968 @item @code{supported-packets}
18969 @tab @code{qSupported}
18970 @tab Remote communications parameters
18972 @item @code{pass-signals}
18973 @tab @code{QPassSignals}
18974 @tab @code{handle @var{signal}}
18976 @item @code{program-signals}
18977 @tab @code{QProgramSignals}
18978 @tab @code{handle @var{signal}}
18980 @item @code{hostio-close-packet}
18981 @tab @code{vFile:close}
18982 @tab @code{remote get}, @code{remote put}
18984 @item @code{hostio-open-packet}
18985 @tab @code{vFile:open}
18986 @tab @code{remote get}, @code{remote put}
18988 @item @code{hostio-pread-packet}
18989 @tab @code{vFile:pread}
18990 @tab @code{remote get}, @code{remote put}
18992 @item @code{hostio-pwrite-packet}
18993 @tab @code{vFile:pwrite}
18994 @tab @code{remote get}, @code{remote put}
18996 @item @code{hostio-unlink-packet}
18997 @tab @code{vFile:unlink}
18998 @tab @code{remote delete}
19000 @item @code{hostio-readlink-packet}
19001 @tab @code{vFile:readlink}
19004 @item @code{noack-packet}
19005 @tab @code{QStartNoAckMode}
19006 @tab Packet acknowledgment
19008 @item @code{osdata}
19009 @tab @code{qXfer:osdata:read}
19010 @tab @code{info os}
19012 @item @code{query-attached}
19013 @tab @code{qAttached}
19014 @tab Querying remote process attach state.
19016 @item @code{trace-buffer-size}
19017 @tab @code{QTBuffer:size}
19018 @tab @code{set trace-buffer-size}
19020 @item @code{trace-status}
19021 @tab @code{qTStatus}
19022 @tab @code{tstatus}
19024 @item @code{traceframe-info}
19025 @tab @code{qXfer:traceframe-info:read}
19026 @tab Traceframe info
19028 @item @code{install-in-trace}
19029 @tab @code{InstallInTrace}
19030 @tab Install tracepoint in tracing
19032 @item @code{disable-randomization}
19033 @tab @code{QDisableRandomization}
19034 @tab @code{set disable-randomization}
19036 @item @code{conditional-breakpoints-packet}
19037 @tab @code{Z0 and Z1}
19038 @tab @code{Support for target-side breakpoint condition evaluation}
19042 @section Implementing a Remote Stub
19044 @cindex debugging stub, example
19045 @cindex remote stub, example
19046 @cindex stub example, remote debugging
19047 The stub files provided with @value{GDBN} implement the target side of the
19048 communication protocol, and the @value{GDBN} side is implemented in the
19049 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19050 these subroutines to communicate, and ignore the details. (If you're
19051 implementing your own stub file, you can still ignore the details: start
19052 with one of the existing stub files. @file{sparc-stub.c} is the best
19053 organized, and therefore the easiest to read.)
19055 @cindex remote serial debugging, overview
19056 To debug a program running on another machine (the debugging
19057 @dfn{target} machine), you must first arrange for all the usual
19058 prerequisites for the program to run by itself. For example, for a C
19063 A startup routine to set up the C runtime environment; these usually
19064 have a name like @file{crt0}. The startup routine may be supplied by
19065 your hardware supplier, or you may have to write your own.
19068 A C subroutine library to support your program's
19069 subroutine calls, notably managing input and output.
19072 A way of getting your program to the other machine---for example, a
19073 download program. These are often supplied by the hardware
19074 manufacturer, but you may have to write your own from hardware
19078 The next step is to arrange for your program to use a serial port to
19079 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19080 machine). In general terms, the scheme looks like this:
19084 @value{GDBN} already understands how to use this protocol; when everything
19085 else is set up, you can simply use the @samp{target remote} command
19086 (@pxref{Targets,,Specifying a Debugging Target}).
19088 @item On the target,
19089 you must link with your program a few special-purpose subroutines that
19090 implement the @value{GDBN} remote serial protocol. The file containing these
19091 subroutines is called a @dfn{debugging stub}.
19093 On certain remote targets, you can use an auxiliary program
19094 @code{gdbserver} instead of linking a stub into your program.
19095 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19098 The debugging stub is specific to the architecture of the remote
19099 machine; for example, use @file{sparc-stub.c} to debug programs on
19102 @cindex remote serial stub list
19103 These working remote stubs are distributed with @value{GDBN}:
19108 @cindex @file{i386-stub.c}
19111 For Intel 386 and compatible architectures.
19114 @cindex @file{m68k-stub.c}
19115 @cindex Motorola 680x0
19117 For Motorola 680x0 architectures.
19120 @cindex @file{sh-stub.c}
19123 For Renesas SH architectures.
19126 @cindex @file{sparc-stub.c}
19128 For @sc{sparc} architectures.
19130 @item sparcl-stub.c
19131 @cindex @file{sparcl-stub.c}
19134 For Fujitsu @sc{sparclite} architectures.
19138 The @file{README} file in the @value{GDBN} distribution may list other
19139 recently added stubs.
19142 * Stub Contents:: What the stub can do for you
19143 * Bootstrapping:: What you must do for the stub
19144 * Debug Session:: Putting it all together
19147 @node Stub Contents
19148 @subsection What the Stub Can Do for You
19150 @cindex remote serial stub
19151 The debugging stub for your architecture supplies these three
19155 @item set_debug_traps
19156 @findex set_debug_traps
19157 @cindex remote serial stub, initialization
19158 This routine arranges for @code{handle_exception} to run when your
19159 program stops. You must call this subroutine explicitly in your
19160 program's startup code.
19162 @item handle_exception
19163 @findex handle_exception
19164 @cindex remote serial stub, main routine
19165 This is the central workhorse, but your program never calls it
19166 explicitly---the setup code arranges for @code{handle_exception} to
19167 run when a trap is triggered.
19169 @code{handle_exception} takes control when your program stops during
19170 execution (for example, on a breakpoint), and mediates communications
19171 with @value{GDBN} on the host machine. This is where the communications
19172 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19173 representative on the target machine. It begins by sending summary
19174 information on the state of your program, then continues to execute,
19175 retrieving and transmitting any information @value{GDBN} needs, until you
19176 execute a @value{GDBN} command that makes your program resume; at that point,
19177 @code{handle_exception} returns control to your own code on the target
19181 @cindex @code{breakpoint} subroutine, remote
19182 Use this auxiliary subroutine to make your program contain a
19183 breakpoint. Depending on the particular situation, this may be the only
19184 way for @value{GDBN} to get control. For instance, if your target
19185 machine has some sort of interrupt button, you won't need to call this;
19186 pressing the interrupt button transfers control to
19187 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19188 simply receiving characters on the serial port may also trigger a trap;
19189 again, in that situation, you don't need to call @code{breakpoint} from
19190 your own program---simply running @samp{target remote} from the host
19191 @value{GDBN} session gets control.
19193 Call @code{breakpoint} if none of these is true, or if you simply want
19194 to make certain your program stops at a predetermined point for the
19195 start of your debugging session.
19198 @node Bootstrapping
19199 @subsection What You Must Do for the Stub
19201 @cindex remote stub, support routines
19202 The debugging stubs that come with @value{GDBN} are set up for a particular
19203 chip architecture, but they have no information about the rest of your
19204 debugging target machine.
19206 First of all you need to tell the stub how to communicate with the
19210 @item int getDebugChar()
19211 @findex getDebugChar
19212 Write this subroutine to read a single character from the serial port.
19213 It may be identical to @code{getchar} for your target system; a
19214 different name is used to allow you to distinguish the two if you wish.
19216 @item void putDebugChar(int)
19217 @findex putDebugChar
19218 Write this subroutine to write a single character to the serial port.
19219 It may be identical to @code{putchar} for your target system; a
19220 different name is used to allow you to distinguish the two if you wish.
19223 @cindex control C, and remote debugging
19224 @cindex interrupting remote targets
19225 If you want @value{GDBN} to be able to stop your program while it is
19226 running, you need to use an interrupt-driven serial driver, and arrange
19227 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19228 character). That is the character which @value{GDBN} uses to tell the
19229 remote system to stop.
19231 Getting the debugging target to return the proper status to @value{GDBN}
19232 probably requires changes to the standard stub; one quick and dirty way
19233 is to just execute a breakpoint instruction (the ``dirty'' part is that
19234 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19236 Other routines you need to supply are:
19239 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19240 @findex exceptionHandler
19241 Write this function to install @var{exception_address} in the exception
19242 handling tables. You need to do this because the stub does not have any
19243 way of knowing what the exception handling tables on your target system
19244 are like (for example, the processor's table might be in @sc{rom},
19245 containing entries which point to a table in @sc{ram}).
19246 @var{exception_number} is the exception number which should be changed;
19247 its meaning is architecture-dependent (for example, different numbers
19248 might represent divide by zero, misaligned access, etc). When this
19249 exception occurs, control should be transferred directly to
19250 @var{exception_address}, and the processor state (stack, registers,
19251 and so on) should be just as it is when a processor exception occurs. So if
19252 you want to use a jump instruction to reach @var{exception_address}, it
19253 should be a simple jump, not a jump to subroutine.
19255 For the 386, @var{exception_address} should be installed as an interrupt
19256 gate so that interrupts are masked while the handler runs. The gate
19257 should be at privilege level 0 (the most privileged level). The
19258 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19259 help from @code{exceptionHandler}.
19261 @item void flush_i_cache()
19262 @findex flush_i_cache
19263 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19264 instruction cache, if any, on your target machine. If there is no
19265 instruction cache, this subroutine may be a no-op.
19267 On target machines that have instruction caches, @value{GDBN} requires this
19268 function to make certain that the state of your program is stable.
19272 You must also make sure this library routine is available:
19275 @item void *memset(void *, int, int)
19277 This is the standard library function @code{memset} that sets an area of
19278 memory to a known value. If you have one of the free versions of
19279 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19280 either obtain it from your hardware manufacturer, or write your own.
19283 If you do not use the GNU C compiler, you may need other standard
19284 library subroutines as well; this varies from one stub to another,
19285 but in general the stubs are likely to use any of the common library
19286 subroutines which @code{@value{NGCC}} generates as inline code.
19289 @node Debug Session
19290 @subsection Putting it All Together
19292 @cindex remote serial debugging summary
19293 In summary, when your program is ready to debug, you must follow these
19298 Make sure you have defined the supporting low-level routines
19299 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19301 @code{getDebugChar}, @code{putDebugChar},
19302 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19306 Insert these lines in your program's startup code, before the main
19307 procedure is called:
19314 On some machines, when a breakpoint trap is raised, the hardware
19315 automatically makes the PC point to the instruction after the
19316 breakpoint. If your machine doesn't do that, you may need to adjust
19317 @code{handle_exception} to arrange for it to return to the instruction
19318 after the breakpoint on this first invocation, so that your program
19319 doesn't keep hitting the initial breakpoint instead of making
19323 For the 680x0 stub only, you need to provide a variable called
19324 @code{exceptionHook}. Normally you just use:
19327 void (*exceptionHook)() = 0;
19331 but if before calling @code{set_debug_traps}, you set it to point to a
19332 function in your program, that function is called when
19333 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19334 error). The function indicated by @code{exceptionHook} is called with
19335 one parameter: an @code{int} which is the exception number.
19338 Compile and link together: your program, the @value{GDBN} debugging stub for
19339 your target architecture, and the supporting subroutines.
19342 Make sure you have a serial connection between your target machine and
19343 the @value{GDBN} host, and identify the serial port on the host.
19346 @c The "remote" target now provides a `load' command, so we should
19347 @c document that. FIXME.
19348 Download your program to your target machine (or get it there by
19349 whatever means the manufacturer provides), and start it.
19352 Start @value{GDBN} on the host, and connect to the target
19353 (@pxref{Connecting,,Connecting to a Remote Target}).
19357 @node Configurations
19358 @chapter Configuration-Specific Information
19360 While nearly all @value{GDBN} commands are available for all native and
19361 cross versions of the debugger, there are some exceptions. This chapter
19362 describes things that are only available in certain configurations.
19364 There are three major categories of configurations: native
19365 configurations, where the host and target are the same, embedded
19366 operating system configurations, which are usually the same for several
19367 different processor architectures, and bare embedded processors, which
19368 are quite different from each other.
19373 * Embedded Processors::
19380 This section describes details specific to particular native
19385 * BSD libkvm Interface:: Debugging BSD kernel memory images
19386 * SVR4 Process Information:: SVR4 process information
19387 * DJGPP Native:: Features specific to the DJGPP port
19388 * Cygwin Native:: Features specific to the Cygwin port
19389 * Hurd Native:: Features specific to @sc{gnu} Hurd
19390 * Darwin:: Features specific to Darwin
19396 On HP-UX systems, if you refer to a function or variable name that
19397 begins with a dollar sign, @value{GDBN} searches for a user or system
19398 name first, before it searches for a convenience variable.
19401 @node BSD libkvm Interface
19402 @subsection BSD libkvm Interface
19405 @cindex kernel memory image
19406 @cindex kernel crash dump
19408 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19409 interface that provides a uniform interface for accessing kernel virtual
19410 memory images, including live systems and crash dumps. @value{GDBN}
19411 uses this interface to allow you to debug live kernels and kernel crash
19412 dumps on many native BSD configurations. This is implemented as a
19413 special @code{kvm} debugging target. For debugging a live system, load
19414 the currently running kernel into @value{GDBN} and connect to the
19418 (@value{GDBP}) @b{target kvm}
19421 For debugging crash dumps, provide the file name of the crash dump as an
19425 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
19428 Once connected to the @code{kvm} target, the following commands are
19434 Set current context from the @dfn{Process Control Block} (PCB) address.
19437 Set current context from proc address. This command isn't available on
19438 modern FreeBSD systems.
19441 @node SVR4 Process Information
19442 @subsection SVR4 Process Information
19444 @cindex examine process image
19445 @cindex process info via @file{/proc}
19447 Many versions of SVR4 and compatible systems provide a facility called
19448 @samp{/proc} that can be used to examine the image of a running
19449 process using file-system subroutines.
19451 If @value{GDBN} is configured for an operating system with this
19452 facility, the command @code{info proc} is available to report
19453 information about the process running your program, or about any
19454 process running on your system. This includes, as of this writing,
19455 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
19456 not HP-UX, for example.
19458 This command may also work on core files that were created on a system
19459 that has the @samp{/proc} facility.
19465 @itemx info proc @var{process-id}
19466 Summarize available information about any running process. If a
19467 process ID is specified by @var{process-id}, display information about
19468 that process; otherwise display information about the program being
19469 debugged. The summary includes the debugged process ID, the command
19470 line used to invoke it, its current working directory, and its
19471 executable file's absolute file name.
19473 On some systems, @var{process-id} can be of the form
19474 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
19475 within a process. If the optional @var{pid} part is missing, it means
19476 a thread from the process being debugged (the leading @samp{/} still
19477 needs to be present, or else @value{GDBN} will interpret the number as
19478 a process ID rather than a thread ID).
19480 @item info proc cmdline
19481 @cindex info proc cmdline
19482 Show the original command line of the process. This command is
19483 specific to @sc{gnu}/Linux.
19485 @item info proc cwd
19486 @cindex info proc cwd
19487 Show the current working directory of the process. This command is
19488 specific to @sc{gnu}/Linux.
19490 @item info proc exe
19491 @cindex info proc exe
19492 Show the name of executable of the process. This command is specific
19495 @item info proc mappings
19496 @cindex memory address space mappings
19497 Report the memory address space ranges accessible in the program, with
19498 information on whether the process has read, write, or execute access
19499 rights to each range. On @sc{gnu}/Linux systems, each memory range
19500 includes the object file which is mapped to that range, instead of the
19501 memory access rights to that range.
19503 @item info proc stat
19504 @itemx info proc status
19505 @cindex process detailed status information
19506 These subcommands are specific to @sc{gnu}/Linux systems. They show
19507 the process-related information, including the user ID and group ID;
19508 how many threads are there in the process; its virtual memory usage;
19509 the signals that are pending, blocked, and ignored; its TTY; its
19510 consumption of system and user time; its stack size; its @samp{nice}
19511 value; etc. For more information, see the @samp{proc} man page
19512 (type @kbd{man 5 proc} from your shell prompt).
19514 @item info proc all
19515 Show all the information about the process described under all of the
19516 above @code{info proc} subcommands.
19519 @comment These sub-options of 'info proc' were not included when
19520 @comment procfs.c was re-written. Keep their descriptions around
19521 @comment against the day when someone finds the time to put them back in.
19522 @kindex info proc times
19523 @item info proc times
19524 Starting time, user CPU time, and system CPU time for your program and
19527 @kindex info proc id
19529 Report on the process IDs related to your program: its own process ID,
19530 the ID of its parent, the process group ID, and the session ID.
19533 @item set procfs-trace
19534 @kindex set procfs-trace
19535 @cindex @code{procfs} API calls
19536 This command enables and disables tracing of @code{procfs} API calls.
19538 @item show procfs-trace
19539 @kindex show procfs-trace
19540 Show the current state of @code{procfs} API call tracing.
19542 @item set procfs-file @var{file}
19543 @kindex set procfs-file
19544 Tell @value{GDBN} to write @code{procfs} API trace to the named
19545 @var{file}. @value{GDBN} appends the trace info to the previous
19546 contents of the file. The default is to display the trace on the
19549 @item show procfs-file
19550 @kindex show procfs-file
19551 Show the file to which @code{procfs} API trace is written.
19553 @item proc-trace-entry
19554 @itemx proc-trace-exit
19555 @itemx proc-untrace-entry
19556 @itemx proc-untrace-exit
19557 @kindex proc-trace-entry
19558 @kindex proc-trace-exit
19559 @kindex proc-untrace-entry
19560 @kindex proc-untrace-exit
19561 These commands enable and disable tracing of entries into and exits
19562 from the @code{syscall} interface.
19565 @kindex info pidlist
19566 @cindex process list, QNX Neutrino
19567 For QNX Neutrino only, this command displays the list of all the
19568 processes and all the threads within each process.
19571 @kindex info meminfo
19572 @cindex mapinfo list, QNX Neutrino
19573 For QNX Neutrino only, this command displays the list of all mapinfos.
19577 @subsection Features for Debugging @sc{djgpp} Programs
19578 @cindex @sc{djgpp} debugging
19579 @cindex native @sc{djgpp} debugging
19580 @cindex MS-DOS-specific commands
19583 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19584 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19585 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19586 top of real-mode DOS systems and their emulations.
19588 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19589 defines a few commands specific to the @sc{djgpp} port. This
19590 subsection describes those commands.
19595 This is a prefix of @sc{djgpp}-specific commands which print
19596 information about the target system and important OS structures.
19599 @cindex MS-DOS system info
19600 @cindex free memory information (MS-DOS)
19601 @item info dos sysinfo
19602 This command displays assorted information about the underlying
19603 platform: the CPU type and features, the OS version and flavor, the
19604 DPMI version, and the available conventional and DPMI memory.
19609 @cindex segment descriptor tables
19610 @cindex descriptor tables display
19612 @itemx info dos ldt
19613 @itemx info dos idt
19614 These 3 commands display entries from, respectively, Global, Local,
19615 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19616 tables are data structures which store a descriptor for each segment
19617 that is currently in use. The segment's selector is an index into a
19618 descriptor table; the table entry for that index holds the
19619 descriptor's base address and limit, and its attributes and access
19622 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19623 segment (used for both data and the stack), and a DOS segment (which
19624 allows access to DOS/BIOS data structures and absolute addresses in
19625 conventional memory). However, the DPMI host will usually define
19626 additional segments in order to support the DPMI environment.
19628 @cindex garbled pointers
19629 These commands allow to display entries from the descriptor tables.
19630 Without an argument, all entries from the specified table are
19631 displayed. An argument, which should be an integer expression, means
19632 display a single entry whose index is given by the argument. For
19633 example, here's a convenient way to display information about the
19634 debugged program's data segment:
19637 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19638 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19642 This comes in handy when you want to see whether a pointer is outside
19643 the data segment's limit (i.e.@: @dfn{garbled}).
19645 @cindex page tables display (MS-DOS)
19647 @itemx info dos pte
19648 These two commands display entries from, respectively, the Page
19649 Directory and the Page Tables. Page Directories and Page Tables are
19650 data structures which control how virtual memory addresses are mapped
19651 into physical addresses. A Page Table includes an entry for every
19652 page of memory that is mapped into the program's address space; there
19653 may be several Page Tables, each one holding up to 4096 entries. A
19654 Page Directory has up to 4096 entries, one each for every Page Table
19655 that is currently in use.
19657 Without an argument, @kbd{info dos pde} displays the entire Page
19658 Directory, and @kbd{info dos pte} displays all the entries in all of
19659 the Page Tables. An argument, an integer expression, given to the
19660 @kbd{info dos pde} command means display only that entry from the Page
19661 Directory table. An argument given to the @kbd{info dos pte} command
19662 means display entries from a single Page Table, the one pointed to by
19663 the specified entry in the Page Directory.
19665 @cindex direct memory access (DMA) on MS-DOS
19666 These commands are useful when your program uses @dfn{DMA} (Direct
19667 Memory Access), which needs physical addresses to program the DMA
19670 These commands are supported only with some DPMI servers.
19672 @cindex physical address from linear address
19673 @item info dos address-pte @var{addr}
19674 This command displays the Page Table entry for a specified linear
19675 address. The argument @var{addr} is a linear address which should
19676 already have the appropriate segment's base address added to it,
19677 because this command accepts addresses which may belong to @emph{any}
19678 segment. For example, here's how to display the Page Table entry for
19679 the page where a variable @code{i} is stored:
19682 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19683 @exdent @code{Page Table entry for address 0x11a00d30:}
19684 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19688 This says that @code{i} is stored at offset @code{0xd30} from the page
19689 whose physical base address is @code{0x02698000}, and shows all the
19690 attributes of that page.
19692 Note that you must cast the addresses of variables to a @code{char *},
19693 since otherwise the value of @code{__djgpp_base_address}, the base
19694 address of all variables and functions in a @sc{djgpp} program, will
19695 be added using the rules of C pointer arithmetics: if @code{i} is
19696 declared an @code{int}, @value{GDBN} will add 4 times the value of
19697 @code{__djgpp_base_address} to the address of @code{i}.
19699 Here's another example, it displays the Page Table entry for the
19703 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19704 @exdent @code{Page Table entry for address 0x29110:}
19705 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19709 (The @code{+ 3} offset is because the transfer buffer's address is the
19710 3rd member of the @code{_go32_info_block} structure.) The output
19711 clearly shows that this DPMI server maps the addresses in conventional
19712 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19713 linear (@code{0x29110}) addresses are identical.
19715 This command is supported only with some DPMI servers.
19718 @cindex DOS serial data link, remote debugging
19719 In addition to native debugging, the DJGPP port supports remote
19720 debugging via a serial data link. The following commands are specific
19721 to remote serial debugging in the DJGPP port of @value{GDBN}.
19724 @kindex set com1base
19725 @kindex set com1irq
19726 @kindex set com2base
19727 @kindex set com2irq
19728 @kindex set com3base
19729 @kindex set com3irq
19730 @kindex set com4base
19731 @kindex set com4irq
19732 @item set com1base @var{addr}
19733 This command sets the base I/O port address of the @file{COM1} serial
19736 @item set com1irq @var{irq}
19737 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19738 for the @file{COM1} serial port.
19740 There are similar commands @samp{set com2base}, @samp{set com3irq},
19741 etc.@: for setting the port address and the @code{IRQ} lines for the
19744 @kindex show com1base
19745 @kindex show com1irq
19746 @kindex show com2base
19747 @kindex show com2irq
19748 @kindex show com3base
19749 @kindex show com3irq
19750 @kindex show com4base
19751 @kindex show com4irq
19752 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19753 display the current settings of the base address and the @code{IRQ}
19754 lines used by the COM ports.
19757 @kindex info serial
19758 @cindex DOS serial port status
19759 This command prints the status of the 4 DOS serial ports. For each
19760 port, it prints whether it's active or not, its I/O base address and
19761 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19762 counts of various errors encountered so far.
19766 @node Cygwin Native
19767 @subsection Features for Debugging MS Windows PE Executables
19768 @cindex MS Windows debugging
19769 @cindex native Cygwin debugging
19770 @cindex Cygwin-specific commands
19772 @value{GDBN} supports native debugging of MS Windows programs, including
19773 DLLs with and without symbolic debugging information.
19775 @cindex Ctrl-BREAK, MS-Windows
19776 @cindex interrupt debuggee on MS-Windows
19777 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19778 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19779 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19780 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19781 sequence, which can be used to interrupt the debuggee even if it
19784 There are various additional Cygwin-specific commands, described in
19785 this section. Working with DLLs that have no debugging symbols is
19786 described in @ref{Non-debug DLL Symbols}.
19791 This is a prefix of MS Windows-specific commands which print
19792 information about the target system and important OS structures.
19794 @item info w32 selector
19795 This command displays information returned by
19796 the Win32 API @code{GetThreadSelectorEntry} function.
19797 It takes an optional argument that is evaluated to
19798 a long value to give the information about this given selector.
19799 Without argument, this command displays information
19800 about the six segment registers.
19802 @item info w32 thread-information-block
19803 This command displays thread specific information stored in the
19804 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19805 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19809 This is a Cygwin-specific alias of @code{info shared}.
19811 @kindex dll-symbols
19813 This command loads symbols from a dll similarly to
19814 add-sym command but without the need to specify a base address.
19816 @kindex set cygwin-exceptions
19817 @cindex debugging the Cygwin DLL
19818 @cindex Cygwin DLL, debugging
19819 @item set cygwin-exceptions @var{mode}
19820 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19821 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19822 @value{GDBN} will delay recognition of exceptions, and may ignore some
19823 exceptions which seem to be caused by internal Cygwin DLL
19824 ``bookkeeping''. This option is meant primarily for debugging the
19825 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19826 @value{GDBN} users with false @code{SIGSEGV} signals.
19828 @kindex show cygwin-exceptions
19829 @item show cygwin-exceptions
19830 Displays whether @value{GDBN} will break on exceptions that happen
19831 inside the Cygwin DLL itself.
19833 @kindex set new-console
19834 @item set new-console @var{mode}
19835 If @var{mode} is @code{on} the debuggee will
19836 be started in a new console on next start.
19837 If @var{mode} is @code{off}, the debuggee will
19838 be started in the same console as the debugger.
19840 @kindex show new-console
19841 @item show new-console
19842 Displays whether a new console is used
19843 when the debuggee is started.
19845 @kindex set new-group
19846 @item set new-group @var{mode}
19847 This boolean value controls whether the debuggee should
19848 start a new group or stay in the same group as the debugger.
19849 This affects the way the Windows OS handles
19852 @kindex show new-group
19853 @item show new-group
19854 Displays current value of new-group boolean.
19856 @kindex set debugevents
19857 @item set debugevents
19858 This boolean value adds debug output concerning kernel events related
19859 to the debuggee seen by the debugger. This includes events that
19860 signal thread and process creation and exit, DLL loading and
19861 unloading, console interrupts, and debugging messages produced by the
19862 Windows @code{OutputDebugString} API call.
19864 @kindex set debugexec
19865 @item set debugexec
19866 This boolean value adds debug output concerning execute events
19867 (such as resume thread) seen by the debugger.
19869 @kindex set debugexceptions
19870 @item set debugexceptions
19871 This boolean value adds debug output concerning exceptions in the
19872 debuggee seen by the debugger.
19874 @kindex set debugmemory
19875 @item set debugmemory
19876 This boolean value adds debug output concerning debuggee memory reads
19877 and writes by the debugger.
19881 This boolean values specifies whether the debuggee is called
19882 via a shell or directly (default value is on).
19886 Displays if the debuggee will be started with a shell.
19891 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19894 @node Non-debug DLL Symbols
19895 @subsubsection Support for DLLs without Debugging Symbols
19896 @cindex DLLs with no debugging symbols
19897 @cindex Minimal symbols and DLLs
19899 Very often on windows, some of the DLLs that your program relies on do
19900 not include symbolic debugging information (for example,
19901 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19902 symbols in a DLL, it relies on the minimal amount of symbolic
19903 information contained in the DLL's export table. This section
19904 describes working with such symbols, known internally to @value{GDBN} as
19905 ``minimal symbols''.
19907 Note that before the debugged program has started execution, no DLLs
19908 will have been loaded. The easiest way around this problem is simply to
19909 start the program --- either by setting a breakpoint or letting the
19910 program run once to completion. It is also possible to force
19911 @value{GDBN} to load a particular DLL before starting the executable ---
19912 see the shared library information in @ref{Files}, or the
19913 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19914 explicitly loading symbols from a DLL with no debugging information will
19915 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19916 which may adversely affect symbol lookup performance.
19918 @subsubsection DLL Name Prefixes
19920 In keeping with the naming conventions used by the Microsoft debugging
19921 tools, DLL export symbols are made available with a prefix based on the
19922 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19923 also entered into the symbol table, so @code{CreateFileA} is often
19924 sufficient. In some cases there will be name clashes within a program
19925 (particularly if the executable itself includes full debugging symbols)
19926 necessitating the use of the fully qualified name when referring to the
19927 contents of the DLL. Use single-quotes around the name to avoid the
19928 exclamation mark (``!'') being interpreted as a language operator.
19930 Note that the internal name of the DLL may be all upper-case, even
19931 though the file name of the DLL is lower-case, or vice-versa. Since
19932 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19933 some confusion. If in doubt, try the @code{info functions} and
19934 @code{info variables} commands or even @code{maint print msymbols}
19935 (@pxref{Symbols}). Here's an example:
19938 (@value{GDBP}) info function CreateFileA
19939 All functions matching regular expression "CreateFileA":
19941 Non-debugging symbols:
19942 0x77e885f4 CreateFileA
19943 0x77e885f4 KERNEL32!CreateFileA
19947 (@value{GDBP}) info function !
19948 All functions matching regular expression "!":
19950 Non-debugging symbols:
19951 0x6100114c cygwin1!__assert
19952 0x61004034 cygwin1!_dll_crt0@@0
19953 0x61004240 cygwin1!dll_crt0(per_process *)
19957 @subsubsection Working with Minimal Symbols
19959 Symbols extracted from a DLL's export table do not contain very much
19960 type information. All that @value{GDBN} can do is guess whether a symbol
19961 refers to a function or variable depending on the linker section that
19962 contains the symbol. Also note that the actual contents of the memory
19963 contained in a DLL are not available unless the program is running. This
19964 means that you cannot examine the contents of a variable or disassemble
19965 a function within a DLL without a running program.
19967 Variables are generally treated as pointers and dereferenced
19968 automatically. For this reason, it is often necessary to prefix a
19969 variable name with the address-of operator (``&'') and provide explicit
19970 type information in the command. Here's an example of the type of
19974 (@value{GDBP}) print 'cygwin1!__argv'
19979 (@value{GDBP}) x 'cygwin1!__argv'
19980 0x10021610: "\230y\""
19983 And two possible solutions:
19986 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19987 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19991 (@value{GDBP}) x/2x &'cygwin1!__argv'
19992 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19993 (@value{GDBP}) x/x 0x10021608
19994 0x10021608: 0x0022fd98
19995 (@value{GDBP}) x/s 0x0022fd98
19996 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19999 Setting a break point within a DLL is possible even before the program
20000 starts execution. However, under these circumstances, @value{GDBN} can't
20001 examine the initial instructions of the function in order to skip the
20002 function's frame set-up code. You can work around this by using ``*&''
20003 to set the breakpoint at a raw memory address:
20006 (@value{GDBP}) break *&'python22!PyOS_Readline'
20007 Breakpoint 1 at 0x1e04eff0
20010 The author of these extensions is not entirely convinced that setting a
20011 break point within a shared DLL like @file{kernel32.dll} is completely
20015 @subsection Commands Specific to @sc{gnu} Hurd Systems
20016 @cindex @sc{gnu} Hurd debugging
20018 This subsection describes @value{GDBN} commands specific to the
20019 @sc{gnu} Hurd native debugging.
20024 @kindex set signals@r{, Hurd command}
20025 @kindex set sigs@r{, Hurd command}
20026 This command toggles the state of inferior signal interception by
20027 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20028 affected by this command. @code{sigs} is a shorthand alias for
20033 @kindex show signals@r{, Hurd command}
20034 @kindex show sigs@r{, Hurd command}
20035 Show the current state of intercepting inferior's signals.
20037 @item set signal-thread
20038 @itemx set sigthread
20039 @kindex set signal-thread
20040 @kindex set sigthread
20041 This command tells @value{GDBN} which thread is the @code{libc} signal
20042 thread. That thread is run when a signal is delivered to a running
20043 process. @code{set sigthread} is the shorthand alias of @code{set
20046 @item show signal-thread
20047 @itemx show sigthread
20048 @kindex show signal-thread
20049 @kindex show sigthread
20050 These two commands show which thread will run when the inferior is
20051 delivered a signal.
20054 @kindex set stopped@r{, Hurd command}
20055 This commands tells @value{GDBN} that the inferior process is stopped,
20056 as with the @code{SIGSTOP} signal. The stopped process can be
20057 continued by delivering a signal to it.
20060 @kindex show stopped@r{, Hurd command}
20061 This command shows whether @value{GDBN} thinks the debuggee is
20064 @item set exceptions
20065 @kindex set exceptions@r{, Hurd command}
20066 Use this command to turn off trapping of exceptions in the inferior.
20067 When exception trapping is off, neither breakpoints nor
20068 single-stepping will work. To restore the default, set exception
20071 @item show exceptions
20072 @kindex show exceptions@r{, Hurd command}
20073 Show the current state of trapping exceptions in the inferior.
20075 @item set task pause
20076 @kindex set task@r{, Hurd commands}
20077 @cindex task attributes (@sc{gnu} Hurd)
20078 @cindex pause current task (@sc{gnu} Hurd)
20079 This command toggles task suspension when @value{GDBN} has control.
20080 Setting it to on takes effect immediately, and the task is suspended
20081 whenever @value{GDBN} gets control. Setting it to off will take
20082 effect the next time the inferior is continued. If this option is set
20083 to off, you can use @code{set thread default pause on} or @code{set
20084 thread pause on} (see below) to pause individual threads.
20086 @item show task pause
20087 @kindex show task@r{, Hurd commands}
20088 Show the current state of task suspension.
20090 @item set task detach-suspend-count
20091 @cindex task suspend count
20092 @cindex detach from task, @sc{gnu} Hurd
20093 This command sets the suspend count the task will be left with when
20094 @value{GDBN} detaches from it.
20096 @item show task detach-suspend-count
20097 Show the suspend count the task will be left with when detaching.
20099 @item set task exception-port
20100 @itemx set task excp
20101 @cindex task exception port, @sc{gnu} Hurd
20102 This command sets the task exception port to which @value{GDBN} will
20103 forward exceptions. The argument should be the value of the @dfn{send
20104 rights} of the task. @code{set task excp} is a shorthand alias.
20106 @item set noninvasive
20107 @cindex noninvasive task options
20108 This command switches @value{GDBN} to a mode that is the least
20109 invasive as far as interfering with the inferior is concerned. This
20110 is the same as using @code{set task pause}, @code{set exceptions}, and
20111 @code{set signals} to values opposite to the defaults.
20113 @item info send-rights
20114 @itemx info receive-rights
20115 @itemx info port-rights
20116 @itemx info port-sets
20117 @itemx info dead-names
20120 @cindex send rights, @sc{gnu} Hurd
20121 @cindex receive rights, @sc{gnu} Hurd
20122 @cindex port rights, @sc{gnu} Hurd
20123 @cindex port sets, @sc{gnu} Hurd
20124 @cindex dead names, @sc{gnu} Hurd
20125 These commands display information about, respectively, send rights,
20126 receive rights, port rights, port sets, and dead names of a task.
20127 There are also shorthand aliases: @code{info ports} for @code{info
20128 port-rights} and @code{info psets} for @code{info port-sets}.
20130 @item set thread pause
20131 @kindex set thread@r{, Hurd command}
20132 @cindex thread properties, @sc{gnu} Hurd
20133 @cindex pause current thread (@sc{gnu} Hurd)
20134 This command toggles current thread suspension when @value{GDBN} has
20135 control. Setting it to on takes effect immediately, and the current
20136 thread is suspended whenever @value{GDBN} gets control. Setting it to
20137 off will take effect the next time the inferior is continued.
20138 Normally, this command has no effect, since when @value{GDBN} has
20139 control, the whole task is suspended. However, if you used @code{set
20140 task pause off} (see above), this command comes in handy to suspend
20141 only the current thread.
20143 @item show thread pause
20144 @kindex show thread@r{, Hurd command}
20145 This command shows the state of current thread suspension.
20147 @item set thread run
20148 This command sets whether the current thread is allowed to run.
20150 @item show thread run
20151 Show whether the current thread is allowed to run.
20153 @item set thread detach-suspend-count
20154 @cindex thread suspend count, @sc{gnu} Hurd
20155 @cindex detach from thread, @sc{gnu} Hurd
20156 This command sets the suspend count @value{GDBN} will leave on a
20157 thread when detaching. This number is relative to the suspend count
20158 found by @value{GDBN} when it notices the thread; use @code{set thread
20159 takeover-suspend-count} to force it to an absolute value.
20161 @item show thread detach-suspend-count
20162 Show the suspend count @value{GDBN} will leave on the thread when
20165 @item set thread exception-port
20166 @itemx set thread excp
20167 Set the thread exception port to which to forward exceptions. This
20168 overrides the port set by @code{set task exception-port} (see above).
20169 @code{set thread excp} is the shorthand alias.
20171 @item set thread takeover-suspend-count
20172 Normally, @value{GDBN}'s thread suspend counts are relative to the
20173 value @value{GDBN} finds when it notices each thread. This command
20174 changes the suspend counts to be absolute instead.
20176 @item set thread default
20177 @itemx show thread default
20178 @cindex thread default settings, @sc{gnu} Hurd
20179 Each of the above @code{set thread} commands has a @code{set thread
20180 default} counterpart (e.g., @code{set thread default pause}, @code{set
20181 thread default exception-port}, etc.). The @code{thread default}
20182 variety of commands sets the default thread properties for all
20183 threads; you can then change the properties of individual threads with
20184 the non-default commands.
20191 @value{GDBN} provides the following commands specific to the Darwin target:
20194 @item set debug darwin @var{num}
20195 @kindex set debug darwin
20196 When set to a non zero value, enables debugging messages specific to
20197 the Darwin support. Higher values produce more verbose output.
20199 @item show debug darwin
20200 @kindex show debug darwin
20201 Show the current state of Darwin messages.
20203 @item set debug mach-o @var{num}
20204 @kindex set debug mach-o
20205 When set to a non zero value, enables debugging messages while
20206 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20207 file format used on Darwin for object and executable files.) Higher
20208 values produce more verbose output. This is a command to diagnose
20209 problems internal to @value{GDBN} and should not be needed in normal
20212 @item show debug mach-o
20213 @kindex show debug mach-o
20214 Show the current state of Mach-O file messages.
20216 @item set mach-exceptions on
20217 @itemx set mach-exceptions off
20218 @kindex set mach-exceptions
20219 On Darwin, faults are first reported as a Mach exception and are then
20220 mapped to a Posix signal. Use this command to turn on trapping of
20221 Mach exceptions in the inferior. This might be sometimes useful to
20222 better understand the cause of a fault. The default is off.
20224 @item show mach-exceptions
20225 @kindex show mach-exceptions
20226 Show the current state of exceptions trapping.
20231 @section Embedded Operating Systems
20233 This section describes configurations involving the debugging of
20234 embedded operating systems that are available for several different
20238 * VxWorks:: Using @value{GDBN} with VxWorks
20241 @value{GDBN} includes the ability to debug programs running on
20242 various real-time operating systems.
20245 @subsection Using @value{GDBN} with VxWorks
20251 @kindex target vxworks
20252 @item target vxworks @var{machinename}
20253 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
20254 is the target system's machine name or IP address.
20258 On VxWorks, @code{load} links @var{filename} dynamically on the
20259 current target system as well as adding its symbols in @value{GDBN}.
20261 @value{GDBN} enables developers to spawn and debug tasks running on networked
20262 VxWorks targets from a Unix host. Already-running tasks spawned from
20263 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
20264 both the Unix host and on the VxWorks target. The program
20265 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
20266 installed with the name @code{vxgdb}, to distinguish it from a
20267 @value{GDBN} for debugging programs on the host itself.)
20270 @item VxWorks-timeout @var{args}
20271 @kindex vxworks-timeout
20272 All VxWorks-based targets now support the option @code{vxworks-timeout}.
20273 This option is set by the user, and @var{args} represents the number of
20274 seconds @value{GDBN} waits for responses to rpc's. You might use this if
20275 your VxWorks target is a slow software simulator or is on the far side
20276 of a thin network line.
20279 The following information on connecting to VxWorks was current when
20280 this manual was produced; newer releases of VxWorks may use revised
20283 @findex INCLUDE_RDB
20284 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
20285 to include the remote debugging interface routines in the VxWorks
20286 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
20287 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
20288 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
20289 source debugging task @code{tRdbTask} when VxWorks is booted. For more
20290 information on configuring and remaking VxWorks, see the manufacturer's
20292 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
20294 Once you have included @file{rdb.a} in your VxWorks system image and set
20295 your Unix execution search path to find @value{GDBN}, you are ready to
20296 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
20297 @code{vxgdb}, depending on your installation).
20299 @value{GDBN} comes up showing the prompt:
20306 * VxWorks Connection:: Connecting to VxWorks
20307 * VxWorks Download:: VxWorks download
20308 * VxWorks Attach:: Running tasks
20311 @node VxWorks Connection
20312 @subsubsection Connecting to VxWorks
20314 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
20315 network. To connect to a target whose host name is ``@code{tt}'', type:
20318 (vxgdb) target vxworks tt
20322 @value{GDBN} displays messages like these:
20325 Attaching remote machine across net...
20330 @value{GDBN} then attempts to read the symbol tables of any object modules
20331 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
20332 these files by searching the directories listed in the command search
20333 path (@pxref{Environment, ,Your Program's Environment}); if it fails
20334 to find an object file, it displays a message such as:
20337 prog.o: No such file or directory.
20340 When this happens, add the appropriate directory to the search path with
20341 the @value{GDBN} command @code{path}, and execute the @code{target}
20344 @node VxWorks Download
20345 @subsubsection VxWorks Download
20347 @cindex download to VxWorks
20348 If you have connected to the VxWorks target and you want to debug an
20349 object that has not yet been loaded, you can use the @value{GDBN}
20350 @code{load} command to download a file from Unix to VxWorks
20351 incrementally. The object file given as an argument to the @code{load}
20352 command is actually opened twice: first by the VxWorks target in order
20353 to download the code, then by @value{GDBN} in order to read the symbol
20354 table. This can lead to problems if the current working directories on
20355 the two systems differ. If both systems have NFS mounted the same
20356 filesystems, you can avoid these problems by using absolute paths.
20357 Otherwise, it is simplest to set the working directory on both systems
20358 to the directory in which the object file resides, and then to reference
20359 the file by its name, without any path. For instance, a program
20360 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
20361 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
20362 program, type this on VxWorks:
20365 -> cd "@var{vxpath}/vw/demo/rdb"
20369 Then, in @value{GDBN}, type:
20372 (vxgdb) cd @var{hostpath}/vw/demo/rdb
20373 (vxgdb) load prog.o
20376 @value{GDBN} displays a response similar to this:
20379 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
20382 You can also use the @code{load} command to reload an object module
20383 after editing and recompiling the corresponding source file. Note that
20384 this makes @value{GDBN} delete all currently-defined breakpoints,
20385 auto-displays, and convenience variables, and to clear the value
20386 history. (This is necessary in order to preserve the integrity of
20387 debugger's data structures that reference the target system's symbol
20390 @node VxWorks Attach
20391 @subsubsection Running Tasks
20393 @cindex running VxWorks tasks
20394 You can also attach to an existing task using the @code{attach} command as
20398 (vxgdb) attach @var{task}
20402 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
20403 or suspended when you attach to it. Running tasks are suspended at
20404 the time of attachment.
20406 @node Embedded Processors
20407 @section Embedded Processors
20409 This section goes into details specific to particular embedded
20412 @cindex send command to simulator
20413 Whenever a specific embedded processor has a simulator, @value{GDBN}
20414 allows to send an arbitrary command to the simulator.
20417 @item sim @var{command}
20418 @kindex sim@r{, a command}
20419 Send an arbitrary @var{command} string to the simulator. Consult the
20420 documentation for the specific simulator in use for information about
20421 acceptable commands.
20427 * M32R/D:: Renesas M32R/D
20428 * M68K:: Motorola M68K
20429 * MicroBlaze:: Xilinx MicroBlaze
20430 * MIPS Embedded:: MIPS Embedded
20431 * PowerPC Embedded:: PowerPC Embedded
20432 * PA:: HP PA Embedded
20433 * Sparclet:: Tsqware Sparclet
20434 * Sparclite:: Fujitsu Sparclite
20435 * Z8000:: Zilog Z8000
20438 * Super-H:: Renesas Super-H
20447 @item target rdi @var{dev}
20448 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20449 use this target to communicate with both boards running the Angel
20450 monitor, or with the EmbeddedICE JTAG debug device.
20453 @item target rdp @var{dev}
20458 @value{GDBN} provides the following ARM-specific commands:
20461 @item set arm disassembler
20463 This commands selects from a list of disassembly styles. The
20464 @code{"std"} style is the standard style.
20466 @item show arm disassembler
20468 Show the current disassembly style.
20470 @item set arm apcs32
20471 @cindex ARM 32-bit mode
20472 This command toggles ARM operation mode between 32-bit and 26-bit.
20474 @item show arm apcs32
20475 Display the current usage of the ARM 32-bit mode.
20477 @item set arm fpu @var{fputype}
20478 This command sets the ARM floating-point unit (FPU) type. The
20479 argument @var{fputype} can be one of these:
20483 Determine the FPU type by querying the OS ABI.
20485 Software FPU, with mixed-endian doubles on little-endian ARM
20488 GCC-compiled FPA co-processor.
20490 Software FPU with pure-endian doubles.
20496 Show the current type of the FPU.
20499 This command forces @value{GDBN} to use the specified ABI.
20502 Show the currently used ABI.
20504 @item set arm fallback-mode (arm|thumb|auto)
20505 @value{GDBN} uses the symbol table, when available, to determine
20506 whether instructions are ARM or Thumb. This command controls
20507 @value{GDBN}'s default behavior when the symbol table is not
20508 available. The default is @samp{auto}, which causes @value{GDBN} to
20509 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20512 @item show arm fallback-mode
20513 Show the current fallback instruction mode.
20515 @item set arm force-mode (arm|thumb|auto)
20516 This command overrides use of the symbol table to determine whether
20517 instructions are ARM or Thumb. The default is @samp{auto}, which
20518 causes @value{GDBN} to use the symbol table and then the setting
20519 of @samp{set arm fallback-mode}.
20521 @item show arm force-mode
20522 Show the current forced instruction mode.
20524 @item set debug arm
20525 Toggle whether to display ARM-specific debugging messages from the ARM
20526 target support subsystem.
20528 @item show debug arm
20529 Show whether ARM-specific debugging messages are enabled.
20532 The following commands are available when an ARM target is debugged
20533 using the RDI interface:
20536 @item rdilogfile @r{[}@var{file}@r{]}
20538 @cindex ADP (Angel Debugger Protocol) logging
20539 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20540 With an argument, sets the log file to the specified @var{file}. With
20541 no argument, show the current log file name. The default log file is
20544 @item rdilogenable @r{[}@var{arg}@r{]}
20545 @kindex rdilogenable
20546 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20547 enables logging, with an argument 0 or @code{"no"} disables it. With
20548 no arguments displays the current setting. When logging is enabled,
20549 ADP packets exchanged between @value{GDBN} and the RDI target device
20550 are logged to a file.
20552 @item set rdiromatzero
20553 @kindex set rdiromatzero
20554 @cindex ROM at zero address, RDI
20555 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20556 vector catching is disabled, so that zero address can be used. If off
20557 (the default), vector catching is enabled. For this command to take
20558 effect, it needs to be invoked prior to the @code{target rdi} command.
20560 @item show rdiromatzero
20561 @kindex show rdiromatzero
20562 Show the current setting of ROM at zero address.
20564 @item set rdiheartbeat
20565 @kindex set rdiheartbeat
20566 @cindex RDI heartbeat
20567 Enable or disable RDI heartbeat packets. It is not recommended to
20568 turn on this option, since it confuses ARM and EPI JTAG interface, as
20569 well as the Angel monitor.
20571 @item show rdiheartbeat
20572 @kindex show rdiheartbeat
20573 Show the setting of RDI heartbeat packets.
20577 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20578 The @value{GDBN} ARM simulator accepts the following optional arguments.
20581 @item --swi-support=@var{type}
20582 Tell the simulator which SWI interfaces to support.
20583 @var{type} may be a comma separated list of the following values.
20584 The default value is @code{all}.
20597 @subsection Renesas M32R/D and M32R/SDI
20600 @kindex target m32r
20601 @item target m32r @var{dev}
20602 Renesas M32R/D ROM monitor.
20604 @kindex target m32rsdi
20605 @item target m32rsdi @var{dev}
20606 Renesas M32R SDI server, connected via parallel port to the board.
20609 The following @value{GDBN} commands are specific to the M32R monitor:
20612 @item set download-path @var{path}
20613 @kindex set download-path
20614 @cindex find downloadable @sc{srec} files (M32R)
20615 Set the default path for finding downloadable @sc{srec} files.
20617 @item show download-path
20618 @kindex show download-path
20619 Show the default path for downloadable @sc{srec} files.
20621 @item set board-address @var{addr}
20622 @kindex set board-address
20623 @cindex M32-EVA target board address
20624 Set the IP address for the M32R-EVA target board.
20626 @item show board-address
20627 @kindex show board-address
20628 Show the current IP address of the target board.
20630 @item set server-address @var{addr}
20631 @kindex set server-address
20632 @cindex download server address (M32R)
20633 Set the IP address for the download server, which is the @value{GDBN}'s
20636 @item show server-address
20637 @kindex show server-address
20638 Display the IP address of the download server.
20640 @item upload @r{[}@var{file}@r{]}
20641 @kindex upload@r{, M32R}
20642 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20643 upload capability. If no @var{file} argument is given, the current
20644 executable file is uploaded.
20646 @item tload @r{[}@var{file}@r{]}
20647 @kindex tload@r{, M32R}
20648 Test the @code{upload} command.
20651 The following commands are available for M32R/SDI:
20656 @cindex reset SDI connection, M32R
20657 This command resets the SDI connection.
20661 This command shows the SDI connection status.
20664 @kindex debug_chaos
20665 @cindex M32R/Chaos debugging
20666 Instructs the remote that M32R/Chaos debugging is to be used.
20668 @item use_debug_dma
20669 @kindex use_debug_dma
20670 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20673 @kindex use_mon_code
20674 Instructs the remote to use the MON_CODE method of accessing memory.
20677 @kindex use_ib_break
20678 Instructs the remote to set breakpoints by IB break.
20680 @item use_dbt_break
20681 @kindex use_dbt_break
20682 Instructs the remote to set breakpoints by DBT.
20688 The Motorola m68k configuration includes ColdFire support, and a
20689 target command for the following ROM monitor.
20693 @kindex target dbug
20694 @item target dbug @var{dev}
20695 dBUG ROM monitor for Motorola ColdFire.
20700 @subsection MicroBlaze
20701 @cindex Xilinx MicroBlaze
20702 @cindex XMD, Xilinx Microprocessor Debugger
20704 The MicroBlaze is a soft-core processor supported on various Xilinx
20705 FPGAs, such as Spartan or Virtex series. Boards with these processors
20706 usually have JTAG ports which connect to a host system running the Xilinx
20707 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20708 This host system is used to download the configuration bitstream to
20709 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20710 communicates with the target board using the JTAG interface and
20711 presents a @code{gdbserver} interface to the board. By default
20712 @code{xmd} uses port @code{1234}. (While it is possible to change
20713 this default port, it requires the use of undocumented @code{xmd}
20714 commands. Contact Xilinx support if you need to do this.)
20716 Use these GDB commands to connect to the MicroBlaze target processor.
20719 @item target remote :1234
20720 Use this command to connect to the target if you are running @value{GDBN}
20721 on the same system as @code{xmd}.
20723 @item target remote @var{xmd-host}:1234
20724 Use this command to connect to the target if it is connected to @code{xmd}
20725 running on a different system named @var{xmd-host}.
20728 Use this command to download a program to the MicroBlaze target.
20730 @item set debug microblaze @var{n}
20731 Enable MicroBlaze-specific debugging messages if non-zero.
20733 @item show debug microblaze @var{n}
20734 Show MicroBlaze-specific debugging level.
20737 @node MIPS Embedded
20738 @subsection @acronym{MIPS} Embedded
20740 @cindex @acronym{MIPS} boards
20741 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20742 @acronym{MIPS} board attached to a serial line. This is available when
20743 you configure @value{GDBN} with @samp{--target=mips-elf}.
20746 Use these @value{GDBN} commands to specify the connection to your target board:
20749 @item target mips @var{port}
20750 @kindex target mips @var{port}
20751 To run a program on the board, start up @code{@value{GDBP}} with the
20752 name of your program as the argument. To connect to the board, use the
20753 command @samp{target mips @var{port}}, where @var{port} is the name of
20754 the serial port connected to the board. If the program has not already
20755 been downloaded to the board, you may use the @code{load} command to
20756 download it. You can then use all the usual @value{GDBN} commands.
20758 For example, this sequence connects to the target board through a serial
20759 port, and loads and runs a program called @var{prog} through the
20763 host$ @value{GDBP} @var{prog}
20764 @value{GDBN} is free software and @dots{}
20765 (@value{GDBP}) target mips /dev/ttyb
20766 (@value{GDBP}) load @var{prog}
20770 @item target mips @var{hostname}:@var{portnumber}
20771 On some @value{GDBN} host configurations, you can specify a TCP
20772 connection (for instance, to a serial line managed by a terminal
20773 concentrator) instead of a serial port, using the syntax
20774 @samp{@var{hostname}:@var{portnumber}}.
20776 @item target pmon @var{port}
20777 @kindex target pmon @var{port}
20780 @item target ddb @var{port}
20781 @kindex target ddb @var{port}
20782 NEC's DDB variant of PMON for Vr4300.
20784 @item target lsi @var{port}
20785 @kindex target lsi @var{port}
20786 LSI variant of PMON.
20788 @kindex target r3900
20789 @item target r3900 @var{dev}
20790 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20792 @kindex target array
20793 @item target array @var{dev}
20794 Array Tech LSI33K RAID controller board.
20800 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20803 @item set mipsfpu double
20804 @itemx set mipsfpu single
20805 @itemx set mipsfpu none
20806 @itemx set mipsfpu auto
20807 @itemx show mipsfpu
20808 @kindex set mipsfpu
20809 @kindex show mipsfpu
20810 @cindex @acronym{MIPS} remote floating point
20811 @cindex floating point, @acronym{MIPS} remote
20812 If your target board does not support the @acronym{MIPS} floating point
20813 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20814 need this, you may wish to put the command in your @value{GDBN} init
20815 file). This tells @value{GDBN} how to find the return value of
20816 functions which return floating point values. It also allows
20817 @value{GDBN} to avoid saving the floating point registers when calling
20818 functions on the board. If you are using a floating point coprocessor
20819 with only single precision floating point support, as on the @sc{r4650}
20820 processor, use the command @samp{set mipsfpu single}. The default
20821 double precision floating point coprocessor may be selected using
20822 @samp{set mipsfpu double}.
20824 In previous versions the only choices were double precision or no
20825 floating point, so @samp{set mipsfpu on} will select double precision
20826 and @samp{set mipsfpu off} will select no floating point.
20828 As usual, you can inquire about the @code{mipsfpu} variable with
20829 @samp{show mipsfpu}.
20831 @item set timeout @var{seconds}
20832 @itemx set retransmit-timeout @var{seconds}
20833 @itemx show timeout
20834 @itemx show retransmit-timeout
20835 @cindex @code{timeout}, @acronym{MIPS} protocol
20836 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20837 @kindex set timeout
20838 @kindex show timeout
20839 @kindex set retransmit-timeout
20840 @kindex show retransmit-timeout
20841 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20842 remote protocol, with the @code{set timeout @var{seconds}} command. The
20843 default is 5 seconds. Similarly, you can control the timeout used while
20844 waiting for an acknowledgment of a packet with the @code{set
20845 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20846 You can inspect both values with @code{show timeout} and @code{show
20847 retransmit-timeout}. (These commands are @emph{only} available when
20848 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20850 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20851 is waiting for your program to stop. In that case, @value{GDBN} waits
20852 forever because it has no way of knowing how long the program is going
20853 to run before stopping.
20855 @item set syn-garbage-limit @var{num}
20856 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20857 @cindex synchronize with remote @acronym{MIPS} target
20858 Limit the maximum number of characters @value{GDBN} should ignore when
20859 it tries to synchronize with the remote target. The default is 10
20860 characters. Setting the limit to -1 means there's no limit.
20862 @item show syn-garbage-limit
20863 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20864 Show the current limit on the number of characters to ignore when
20865 trying to synchronize with the remote system.
20867 @item set monitor-prompt @var{prompt}
20868 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20869 @cindex remote monitor prompt
20870 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20871 remote monitor. The default depends on the target:
20881 @item show monitor-prompt
20882 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20883 Show the current strings @value{GDBN} expects as the prompt from the
20886 @item set monitor-warnings
20887 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20888 Enable or disable monitor warnings about hardware breakpoints. This
20889 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20890 display warning messages whose codes are returned by the @code{lsi}
20891 PMON monitor for breakpoint commands.
20893 @item show monitor-warnings
20894 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20895 Show the current setting of printing monitor warnings.
20897 @item pmon @var{command}
20898 @kindex pmon@r{, @acronym{MIPS} remote}
20899 @cindex send PMON command
20900 This command allows sending an arbitrary @var{command} string to the
20901 monitor. The monitor must be in debug mode for this to work.
20904 @node PowerPC Embedded
20905 @subsection PowerPC Embedded
20907 @cindex DVC register
20908 @value{GDBN} supports using the DVC (Data Value Compare) register to
20909 implement in hardware simple hardware watchpoint conditions of the form:
20912 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20913 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20916 The DVC register will be automatically used when @value{GDBN} detects
20917 such pattern in a condition expression, and the created watchpoint uses one
20918 debug register (either the @code{exact-watchpoints} option is on and the
20919 variable is scalar, or the variable has a length of one byte). This feature
20920 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20923 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20924 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20925 in which case watchpoints using only one debug register are created when
20926 watching variables of scalar types.
20928 You can create an artificial array to watch an arbitrary memory
20929 region using one of the following commands (@pxref{Expressions}):
20932 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20933 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20936 PowerPC embedded processors support masked watchpoints. See the discussion
20937 about the @code{mask} argument in @ref{Set Watchpoints}.
20939 @cindex ranged breakpoint
20940 PowerPC embedded processors support hardware accelerated
20941 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20942 the inferior whenever it executes an instruction at any address within
20943 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20944 use the @code{break-range} command.
20946 @value{GDBN} provides the following PowerPC-specific commands:
20949 @kindex break-range
20950 @item break-range @var{start-location}, @var{end-location}
20951 Set a breakpoint for an address range.
20952 @var{start-location} and @var{end-location} can specify a function name,
20953 a line number, an offset of lines from the current line or from the start
20954 location, or an address of an instruction (see @ref{Specify Location},
20955 for a list of all the possible ways to specify a @var{location}.)
20956 The breakpoint will stop execution of the inferior whenever it
20957 executes an instruction at any address within the specified range,
20958 (including @var{start-location} and @var{end-location}.)
20960 @kindex set powerpc
20961 @item set powerpc soft-float
20962 @itemx show powerpc soft-float
20963 Force @value{GDBN} to use (or not use) a software floating point calling
20964 convention. By default, @value{GDBN} selects the calling convention based
20965 on the selected architecture and the provided executable file.
20967 @item set powerpc vector-abi
20968 @itemx show powerpc vector-abi
20969 Force @value{GDBN} to use the specified calling convention for vector
20970 arguments and return values. The valid options are @samp{auto};
20971 @samp{generic}, to avoid vector registers even if they are present;
20972 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20973 registers. By default, @value{GDBN} selects the calling convention
20974 based on the selected architecture and the provided executable file.
20976 @item set powerpc exact-watchpoints
20977 @itemx show powerpc exact-watchpoints
20978 Allow @value{GDBN} to use only one debug register when watching a variable
20979 of scalar type, thus assuming that the variable is accessed through the
20980 address of its first byte.
20982 @kindex target dink32
20983 @item target dink32 @var{dev}
20984 DINK32 ROM monitor.
20986 @kindex target ppcbug
20987 @item target ppcbug @var{dev}
20988 @kindex target ppcbug1
20989 @item target ppcbug1 @var{dev}
20990 PPCBUG ROM monitor for PowerPC.
20993 @item target sds @var{dev}
20994 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20997 @cindex SDS protocol
20998 The following commands specific to the SDS protocol are supported
21002 @item set sdstimeout @var{nsec}
21003 @kindex set sdstimeout
21004 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21005 default is 2 seconds.
21007 @item show sdstimeout
21008 @kindex show sdstimeout
21009 Show the current value of the SDS timeout.
21011 @item sds @var{command}
21012 @kindex sds@r{, a command}
21013 Send the specified @var{command} string to the SDS monitor.
21018 @subsection HP PA Embedded
21022 @kindex target op50n
21023 @item target op50n @var{dev}
21024 OP50N monitor, running on an OKI HPPA board.
21026 @kindex target w89k
21027 @item target w89k @var{dev}
21028 W89K monitor, running on a Winbond HPPA board.
21033 @subsection Tsqware Sparclet
21037 @value{GDBN} enables developers to debug tasks running on
21038 Sparclet targets from a Unix host.
21039 @value{GDBN} uses code that runs on
21040 both the Unix host and on the Sparclet target. The program
21041 @code{@value{GDBP}} is installed and executed on the Unix host.
21044 @item remotetimeout @var{args}
21045 @kindex remotetimeout
21046 @value{GDBN} supports the option @code{remotetimeout}.
21047 This option is set by the user, and @var{args} represents the number of
21048 seconds @value{GDBN} waits for responses.
21051 @cindex compiling, on Sparclet
21052 When compiling for debugging, include the options @samp{-g} to get debug
21053 information and @samp{-Ttext} to relocate the program to where you wish to
21054 load it on the target. You may also want to add the options @samp{-n} or
21055 @samp{-N} in order to reduce the size of the sections. Example:
21058 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21061 You can use @code{objdump} to verify that the addresses are what you intended:
21064 sparclet-aout-objdump --headers --syms prog
21067 @cindex running, on Sparclet
21069 your Unix execution search path to find @value{GDBN}, you are ready to
21070 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21071 (or @code{sparclet-aout-gdb}, depending on your installation).
21073 @value{GDBN} comes up showing the prompt:
21080 * Sparclet File:: Setting the file to debug
21081 * Sparclet Connection:: Connecting to Sparclet
21082 * Sparclet Download:: Sparclet download
21083 * Sparclet Execution:: Running and debugging
21086 @node Sparclet File
21087 @subsubsection Setting File to Debug
21089 The @value{GDBN} command @code{file} lets you choose with program to debug.
21092 (gdbslet) file prog
21096 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21097 @value{GDBN} locates
21098 the file by searching the directories listed in the command search
21100 If the file was compiled with debug information (option @samp{-g}), source
21101 files will be searched as well.
21102 @value{GDBN} locates
21103 the source files by searching the directories listed in the directory search
21104 path (@pxref{Environment, ,Your Program's Environment}).
21106 to find a file, it displays a message such as:
21109 prog: No such file or directory.
21112 When this happens, add the appropriate directories to the search paths with
21113 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21114 @code{target} command again.
21116 @node Sparclet Connection
21117 @subsubsection Connecting to Sparclet
21119 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21120 To connect to a target on serial port ``@code{ttya}'', type:
21123 (gdbslet) target sparclet /dev/ttya
21124 Remote target sparclet connected to /dev/ttya
21125 main () at ../prog.c:3
21129 @value{GDBN} displays messages like these:
21135 @node Sparclet Download
21136 @subsubsection Sparclet Download
21138 @cindex download to Sparclet
21139 Once connected to the Sparclet target,
21140 you can use the @value{GDBN}
21141 @code{load} command to download the file from the host to the target.
21142 The file name and load offset should be given as arguments to the @code{load}
21144 Since the file format is aout, the program must be loaded to the starting
21145 address. You can use @code{objdump} to find out what this value is. The load
21146 offset is an offset which is added to the VMA (virtual memory address)
21147 of each of the file's sections.
21148 For instance, if the program
21149 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21150 and bss at 0x12010170, in @value{GDBN}, type:
21153 (gdbslet) load prog 0x12010000
21154 Loading section .text, size 0xdb0 vma 0x12010000
21157 If the code is loaded at a different address then what the program was linked
21158 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21159 to tell @value{GDBN} where to map the symbol table.
21161 @node Sparclet Execution
21162 @subsubsection Running and Debugging
21164 @cindex running and debugging Sparclet programs
21165 You can now begin debugging the task using @value{GDBN}'s execution control
21166 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21167 manual for the list of commands.
21171 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21173 Starting program: prog
21174 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21175 3 char *symarg = 0;
21177 4 char *execarg = "hello!";
21182 @subsection Fujitsu Sparclite
21186 @kindex target sparclite
21187 @item target sparclite @var{dev}
21188 Fujitsu sparclite boards, used only for the purpose of loading.
21189 You must use an additional command to debug the program.
21190 For example: target remote @var{dev} using @value{GDBN} standard
21196 @subsection Zilog Z8000
21199 @cindex simulator, Z8000
21200 @cindex Zilog Z8000 simulator
21202 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21205 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21206 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21207 segmented variant). The simulator recognizes which architecture is
21208 appropriate by inspecting the object code.
21211 @item target sim @var{args}
21213 @kindex target sim@r{, with Z8000}
21214 Debug programs on a simulated CPU. If the simulator supports setup
21215 options, specify them via @var{args}.
21219 After specifying this target, you can debug programs for the simulated
21220 CPU in the same style as programs for your host computer; use the
21221 @code{file} command to load a new program image, the @code{run} command
21222 to run your program, and so on.
21224 As well as making available all the usual machine registers
21225 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21226 additional items of information as specially named registers:
21231 Counts clock-ticks in the simulator.
21234 Counts instructions run in the simulator.
21237 Execution time in 60ths of a second.
21241 You can refer to these values in @value{GDBN} expressions with the usual
21242 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21243 conditional breakpoint that suspends only after at least 5000
21244 simulated clock ticks.
21247 @subsection Atmel AVR
21250 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21251 following AVR-specific commands:
21254 @item info io_registers
21255 @kindex info io_registers@r{, AVR}
21256 @cindex I/O registers (Atmel AVR)
21257 This command displays information about the AVR I/O registers. For
21258 each register, @value{GDBN} prints its number and value.
21265 When configured for debugging CRIS, @value{GDBN} provides the
21266 following CRIS-specific commands:
21269 @item set cris-version @var{ver}
21270 @cindex CRIS version
21271 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21272 The CRIS version affects register names and sizes. This command is useful in
21273 case autodetection of the CRIS version fails.
21275 @item show cris-version
21276 Show the current CRIS version.
21278 @item set cris-dwarf2-cfi
21279 @cindex DWARF-2 CFI and CRIS
21280 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21281 Change to @samp{off} when using @code{gcc-cris} whose version is below
21284 @item show cris-dwarf2-cfi
21285 Show the current state of using DWARF-2 CFI.
21287 @item set cris-mode @var{mode}
21289 Set the current CRIS mode to @var{mode}. It should only be changed when
21290 debugging in guru mode, in which case it should be set to
21291 @samp{guru} (the default is @samp{normal}).
21293 @item show cris-mode
21294 Show the current CRIS mode.
21298 @subsection Renesas Super-H
21301 For the Renesas Super-H processor, @value{GDBN} provides these
21305 @item set sh calling-convention @var{convention}
21306 @kindex set sh calling-convention
21307 Set the calling-convention used when calling functions from @value{GDBN}.
21308 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21309 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21310 convention. If the DWARF-2 information of the called function specifies
21311 that the function follows the Renesas calling convention, the function
21312 is called using the Renesas calling convention. If the calling convention
21313 is set to @samp{renesas}, the Renesas calling convention is always used,
21314 regardless of the DWARF-2 information. This can be used to override the
21315 default of @samp{gcc} if debug information is missing, or the compiler
21316 does not emit the DWARF-2 calling convention entry for a function.
21318 @item show sh calling-convention
21319 @kindex show sh calling-convention
21320 Show the current calling convention setting.
21325 @node Architectures
21326 @section Architectures
21328 This section describes characteristics of architectures that affect
21329 all uses of @value{GDBN} with the architecture, both native and cross.
21336 * HPPA:: HP PA architecture
21337 * SPU:: Cell Broadband Engine SPU architecture
21343 @subsection AArch64
21344 @cindex AArch64 support
21346 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21347 following special commands:
21350 @item set debug aarch64
21351 @kindex set debug aarch64
21352 This command determines whether AArch64 architecture-specific debugging
21353 messages are to be displayed.
21355 @item show debug aarch64
21356 Show whether AArch64 debugging messages are displayed.
21361 @subsection x86 Architecture-specific Issues
21364 @item set struct-convention @var{mode}
21365 @kindex set struct-convention
21366 @cindex struct return convention
21367 @cindex struct/union returned in registers
21368 Set the convention used by the inferior to return @code{struct}s and
21369 @code{union}s from functions to @var{mode}. Possible values of
21370 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21371 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21372 are returned on the stack, while @code{"reg"} means that a
21373 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21374 be returned in a register.
21376 @item show struct-convention
21377 @kindex show struct-convention
21378 Show the current setting of the convention to return @code{struct}s
21381 @cindex Intel(R) Memory Protection Extensions (MPX).
21382 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
21384 @item bnd0raw..bnd3raw and bnd0@dots{}bnd3 registers display.
21385 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
21386 @footnote{The register named with capital letters represent the architecture
21387 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
21388 which are the lower bound and upper bound. Bounds are effective addresses or
21389 memory locations. The upper bounds are architecturally represented in 1's
21390 complement form. A bound having lower bound = 0, and upper bound = 0
21391 (1's complement of all bits set) will allow access to the entire address space.
21393 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
21394 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
21395 display the upper bound performing the complement of one operation on the
21396 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
21397 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
21398 can also be noted that the upper bounds are inclusive.
21400 As an example, assume that the register BND0 holds bounds for a pointer having
21401 access allowed for the range between 0x32 and 0x71. The values present on
21402 bnd0raw and bnd registers are presented as follows:
21405 bnd0raw = @{0x32, 0xffffffff8e@}
21406 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
21409 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any change
21410 on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its counterpart. When the
21411 bnd0@dots{}bnd3 registers are displayed via Python, the display includes the memory size,
21412 in bits, accessible to the pointer.
21418 See the following section.
21421 @subsection @acronym{MIPS}
21423 @cindex stack on Alpha
21424 @cindex stack on @acronym{MIPS}
21425 @cindex Alpha stack
21426 @cindex @acronym{MIPS} stack
21427 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21428 sometimes requires @value{GDBN} to search backward in the object code to
21429 find the beginning of a function.
21431 @cindex response time, @acronym{MIPS} debugging
21432 To improve response time (especially for embedded applications, where
21433 @value{GDBN} may be restricted to a slow serial line for this search)
21434 you may want to limit the size of this search, using one of these
21438 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21439 @item set heuristic-fence-post @var{limit}
21440 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21441 search for the beginning of a function. A value of @var{0} (the
21442 default) means there is no limit. However, except for @var{0}, the
21443 larger the limit the more bytes @code{heuristic-fence-post} must search
21444 and therefore the longer it takes to run. You should only need to use
21445 this command when debugging a stripped executable.
21447 @item show heuristic-fence-post
21448 Display the current limit.
21452 These commands are available @emph{only} when @value{GDBN} is configured
21453 for debugging programs on Alpha or @acronym{MIPS} processors.
21455 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21459 @item set mips abi @var{arg}
21460 @kindex set mips abi
21461 @cindex set ABI for @acronym{MIPS}
21462 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21463 values of @var{arg} are:
21467 The default ABI associated with the current binary (this is the
21477 @item show mips abi
21478 @kindex show mips abi
21479 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21481 @item set mips compression @var{arg}
21482 @kindex set mips compression
21483 @cindex code compression, @acronym{MIPS}
21484 Tell @value{GDBN} which @acronym{MIPS} compressed
21485 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21486 inferior. @value{GDBN} uses this for code disassembly and other
21487 internal interpretation purposes. This setting is only referred to
21488 when no executable has been associated with the debugging session or
21489 the executable does not provide information about the encoding it uses.
21490 Otherwise this setting is automatically updated from information
21491 provided by the executable.
21493 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21494 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21495 executables containing @acronym{MIPS16} code frequently are not
21496 identified as such.
21498 This setting is ``sticky''; that is, it retains its value across
21499 debugging sessions until reset either explicitly with this command or
21500 implicitly from an executable.
21502 The compiler and/or assembler typically add symbol table annotations to
21503 identify functions compiled for the @acronym{MIPS16} or
21504 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21505 are present, @value{GDBN} uses them in preference to the global
21506 compressed @acronym{ISA} encoding setting.
21508 @item show mips compression
21509 @kindex show mips compression
21510 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21511 @value{GDBN} to debug the inferior.
21514 @itemx show mipsfpu
21515 @xref{MIPS Embedded, set mipsfpu}.
21517 @item set mips mask-address @var{arg}
21518 @kindex set mips mask-address
21519 @cindex @acronym{MIPS} addresses, masking
21520 This command determines whether the most-significant 32 bits of 64-bit
21521 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21522 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21523 setting, which lets @value{GDBN} determine the correct value.
21525 @item show mips mask-address
21526 @kindex show mips mask-address
21527 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21530 @item set remote-mips64-transfers-32bit-regs
21531 @kindex set remote-mips64-transfers-32bit-regs
21532 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21533 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21534 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21535 and 64 bits for other registers, set this option to @samp{on}.
21537 @item show remote-mips64-transfers-32bit-regs
21538 @kindex show remote-mips64-transfers-32bit-regs
21539 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21541 @item set debug mips
21542 @kindex set debug mips
21543 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21544 target code in @value{GDBN}.
21546 @item show debug mips
21547 @kindex show debug mips
21548 Show the current setting of @acronym{MIPS} debugging messages.
21554 @cindex HPPA support
21556 When @value{GDBN} is debugging the HP PA architecture, it provides the
21557 following special commands:
21560 @item set debug hppa
21561 @kindex set debug hppa
21562 This command determines whether HPPA architecture-specific debugging
21563 messages are to be displayed.
21565 @item show debug hppa
21566 Show whether HPPA debugging messages are displayed.
21568 @item maint print unwind @var{address}
21569 @kindex maint print unwind@r{, HPPA}
21570 This command displays the contents of the unwind table entry at the
21571 given @var{address}.
21577 @subsection Cell Broadband Engine SPU architecture
21578 @cindex Cell Broadband Engine
21581 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21582 it provides the following special commands:
21585 @item info spu event
21587 Display SPU event facility status. Shows current event mask
21588 and pending event status.
21590 @item info spu signal
21591 Display SPU signal notification facility status. Shows pending
21592 signal-control word and signal notification mode of both signal
21593 notification channels.
21595 @item info spu mailbox
21596 Display SPU mailbox facility status. Shows all pending entries,
21597 in order of processing, in each of the SPU Write Outbound,
21598 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21601 Display MFC DMA status. Shows all pending commands in the MFC
21602 DMA queue. For each entry, opcode, tag, class IDs, effective
21603 and local store addresses and transfer size are shown.
21605 @item info spu proxydma
21606 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21607 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21608 and local store addresses and transfer size are shown.
21612 When @value{GDBN} is debugging a combined PowerPC/SPU application
21613 on the Cell Broadband Engine, it provides in addition the following
21617 @item set spu stop-on-load @var{arg}
21619 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21620 will give control to the user when a new SPE thread enters its @code{main}
21621 function. The default is @code{off}.
21623 @item show spu stop-on-load
21625 Show whether to stop for new SPE threads.
21627 @item set spu auto-flush-cache @var{arg}
21628 Set whether to automatically flush the software-managed cache. When set to
21629 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21630 cache to be flushed whenever SPE execution stops. This provides a consistent
21631 view of PowerPC memory that is accessed via the cache. If an application
21632 does not use the software-managed cache, this option has no effect.
21634 @item show spu auto-flush-cache
21635 Show whether to automatically flush the software-managed cache.
21640 @subsection PowerPC
21641 @cindex PowerPC architecture
21643 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21644 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21645 numbers stored in the floating point registers. These values must be stored
21646 in two consecutive registers, always starting at an even register like
21647 @code{f0} or @code{f2}.
21649 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21650 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21651 @code{f2} and @code{f3} for @code{$dl1} and so on.
21653 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21654 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21657 @subsection Nios II
21658 @cindex Nios II architecture
21660 When @value{GDBN} is debugging the Nios II architecture,
21661 it provides the following special commands:
21665 @item set debug nios2
21666 @kindex set debug nios2
21667 This command turns on and off debugging messages for the Nios II
21668 target code in @value{GDBN}.
21670 @item show debug nios2
21671 @kindex show debug nios2
21672 Show the current setting of Nios II debugging messages.
21675 @node Controlling GDB
21676 @chapter Controlling @value{GDBN}
21678 You can alter the way @value{GDBN} interacts with you by using the
21679 @code{set} command. For commands controlling how @value{GDBN} displays
21680 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21685 * Editing:: Command editing
21686 * Command History:: Command history
21687 * Screen Size:: Screen size
21688 * Numbers:: Numbers
21689 * ABI:: Configuring the current ABI
21690 * Auto-loading:: Automatically loading associated files
21691 * Messages/Warnings:: Optional warnings and messages
21692 * Debugging Output:: Optional messages about internal happenings
21693 * Other Misc Settings:: Other Miscellaneous Settings
21701 @value{GDBN} indicates its readiness to read a command by printing a string
21702 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21703 can change the prompt string with the @code{set prompt} command. For
21704 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21705 the prompt in one of the @value{GDBN} sessions so that you can always tell
21706 which one you are talking to.
21708 @emph{Note:} @code{set prompt} does not add a space for you after the
21709 prompt you set. This allows you to set a prompt which ends in a space
21710 or a prompt that does not.
21714 @item set prompt @var{newprompt}
21715 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21717 @kindex show prompt
21719 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21722 Versions of @value{GDBN} that ship with Python scripting enabled have
21723 prompt extensions. The commands for interacting with these extensions
21727 @kindex set extended-prompt
21728 @item set extended-prompt @var{prompt}
21729 Set an extended prompt that allows for substitutions.
21730 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21731 substitution. Any escape sequences specified as part of the prompt
21732 string are replaced with the corresponding strings each time the prompt
21738 set extended-prompt Current working directory: \w (gdb)
21741 Note that when an extended-prompt is set, it takes control of the
21742 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21744 @kindex show extended-prompt
21745 @item show extended-prompt
21746 Prints the extended prompt. Any escape sequences specified as part of
21747 the prompt string with @code{set extended-prompt}, are replaced with the
21748 corresponding strings each time the prompt is displayed.
21752 @section Command Editing
21754 @cindex command line editing
21756 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21757 @sc{gnu} library provides consistent behavior for programs which provide a
21758 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21759 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21760 substitution, and a storage and recall of command history across
21761 debugging sessions.
21763 You may control the behavior of command line editing in @value{GDBN} with the
21764 command @code{set}.
21767 @kindex set editing
21770 @itemx set editing on
21771 Enable command line editing (enabled by default).
21773 @item set editing off
21774 Disable command line editing.
21776 @kindex show editing
21778 Show whether command line editing is enabled.
21781 @ifset SYSTEM_READLINE
21782 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21784 @ifclear SYSTEM_READLINE
21785 @xref{Command Line Editing},
21787 for more details about the Readline
21788 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21789 encouraged to read that chapter.
21791 @node Command History
21792 @section Command History
21793 @cindex command history
21795 @value{GDBN} can keep track of the commands you type during your
21796 debugging sessions, so that you can be certain of precisely what
21797 happened. Use these commands to manage the @value{GDBN} command
21800 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21801 package, to provide the history facility.
21802 @ifset SYSTEM_READLINE
21803 @xref{Using History Interactively, , , history, GNU History Library},
21805 @ifclear SYSTEM_READLINE
21806 @xref{Using History Interactively},
21808 for the detailed description of the History library.
21810 To issue a command to @value{GDBN} without affecting certain aspects of
21811 the state which is seen by users, prefix it with @samp{server }
21812 (@pxref{Server Prefix}). This
21813 means that this command will not affect the command history, nor will it
21814 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21815 pressed on a line by itself.
21817 @cindex @code{server}, command prefix
21818 The server prefix does not affect the recording of values into the value
21819 history; to print a value without recording it into the value history,
21820 use the @code{output} command instead of the @code{print} command.
21822 Here is the description of @value{GDBN} commands related to command
21826 @cindex history substitution
21827 @cindex history file
21828 @kindex set history filename
21829 @cindex @env{GDBHISTFILE}, environment variable
21830 @item set history filename @var{fname}
21831 Set the name of the @value{GDBN} command history file to @var{fname}.
21832 This is the file where @value{GDBN} reads an initial command history
21833 list, and where it writes the command history from this session when it
21834 exits. You can access this list through history expansion or through
21835 the history command editing characters listed below. This file defaults
21836 to the value of the environment variable @code{GDBHISTFILE}, or to
21837 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21840 @cindex save command history
21841 @kindex set history save
21842 @item set history save
21843 @itemx set history save on
21844 Record command history in a file, whose name may be specified with the
21845 @code{set history filename} command. By default, this option is disabled.
21847 @item set history save off
21848 Stop recording command history in a file.
21850 @cindex history size
21851 @kindex set history size
21852 @cindex @env{HISTSIZE}, environment variable
21853 @item set history size @var{size}
21854 @itemx set history size unlimited
21855 Set the number of commands which @value{GDBN} keeps in its history list.
21856 This defaults to the value of the environment variable
21857 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21858 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21859 history list is unlimited.
21862 History expansion assigns special meaning to the character @kbd{!}.
21863 @ifset SYSTEM_READLINE
21864 @xref{Event Designators, , , history, GNU History Library},
21866 @ifclear SYSTEM_READLINE
21867 @xref{Event Designators},
21871 @cindex history expansion, turn on/off
21872 Since @kbd{!} is also the logical not operator in C, history expansion
21873 is off by default. If you decide to enable history expansion with the
21874 @code{set history expansion on} command, you may sometimes need to
21875 follow @kbd{!} (when it is used as logical not, in an expression) with
21876 a space or a tab to prevent it from being expanded. The readline
21877 history facilities do not attempt substitution on the strings
21878 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21880 The commands to control history expansion are:
21883 @item set history expansion on
21884 @itemx set history expansion
21885 @kindex set history expansion
21886 Enable history expansion. History expansion is off by default.
21888 @item set history expansion off
21889 Disable history expansion.
21892 @kindex show history
21894 @itemx show history filename
21895 @itemx show history save
21896 @itemx show history size
21897 @itemx show history expansion
21898 These commands display the state of the @value{GDBN} history parameters.
21899 @code{show history} by itself displays all four states.
21904 @kindex show commands
21905 @cindex show last commands
21906 @cindex display command history
21907 @item show commands
21908 Display the last ten commands in the command history.
21910 @item show commands @var{n}
21911 Print ten commands centered on command number @var{n}.
21913 @item show commands +
21914 Print ten commands just after the commands last printed.
21918 @section Screen Size
21919 @cindex size of screen
21920 @cindex pauses in output
21922 Certain commands to @value{GDBN} may produce large amounts of
21923 information output to the screen. To help you read all of it,
21924 @value{GDBN} pauses and asks you for input at the end of each page of
21925 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21926 to discard the remaining output. Also, the screen width setting
21927 determines when to wrap lines of output. Depending on what is being
21928 printed, @value{GDBN} tries to break the line at a readable place,
21929 rather than simply letting it overflow onto the following line.
21931 Normally @value{GDBN} knows the size of the screen from the terminal
21932 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21933 together with the value of the @code{TERM} environment variable and the
21934 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21935 you can override it with the @code{set height} and @code{set
21942 @kindex show height
21943 @item set height @var{lpp}
21944 @itemx set height unlimited
21946 @itemx set width @var{cpl}
21947 @itemx set width unlimited
21949 These @code{set} commands specify a screen height of @var{lpp} lines and
21950 a screen width of @var{cpl} characters. The associated @code{show}
21951 commands display the current settings.
21953 If you specify a height of either @code{unlimited} or zero lines,
21954 @value{GDBN} does not pause during output no matter how long the
21955 output is. This is useful if output is to a file or to an editor
21958 Likewise, you can specify @samp{set width unlimited} or @samp{set
21959 width 0} to prevent @value{GDBN} from wrapping its output.
21961 @item set pagination on
21962 @itemx set pagination off
21963 @kindex set pagination
21964 Turn the output pagination on or off; the default is on. Turning
21965 pagination off is the alternative to @code{set height unlimited}. Note that
21966 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21967 Options, -batch}) also automatically disables pagination.
21969 @item show pagination
21970 @kindex show pagination
21971 Show the current pagination mode.
21976 @cindex number representation
21977 @cindex entering numbers
21979 You can always enter numbers in octal, decimal, or hexadecimal in
21980 @value{GDBN} by the usual conventions: octal numbers begin with
21981 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21982 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21983 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21984 10; likewise, the default display for numbers---when no particular
21985 format is specified---is base 10. You can change the default base for
21986 both input and output with the commands described below.
21989 @kindex set input-radix
21990 @item set input-radix @var{base}
21991 Set the default base for numeric input. Supported choices
21992 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21993 specified either unambiguously or using the current input radix; for
21997 set input-radix 012
21998 set input-radix 10.
21999 set input-radix 0xa
22003 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22004 leaves the input radix unchanged, no matter what it was, since
22005 @samp{10}, being without any leading or trailing signs of its base, is
22006 interpreted in the current radix. Thus, if the current radix is 16,
22007 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22010 @kindex set output-radix
22011 @item set output-radix @var{base}
22012 Set the default base for numeric display. Supported choices
22013 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
22014 specified either unambiguously or using the current input radix.
22016 @kindex show input-radix
22017 @item show input-radix
22018 Display the current default base for numeric input.
22020 @kindex show output-radix
22021 @item show output-radix
22022 Display the current default base for numeric display.
22024 @item set radix @r{[}@var{base}@r{]}
22028 These commands set and show the default base for both input and output
22029 of numbers. @code{set radix} sets the radix of input and output to
22030 the same base; without an argument, it resets the radix back to its
22031 default value of 10.
22036 @section Configuring the Current ABI
22038 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22039 application automatically. However, sometimes you need to override its
22040 conclusions. Use these commands to manage @value{GDBN}'s view of the
22046 @cindex Newlib OS ABI and its influence on the longjmp handling
22048 One @value{GDBN} configuration can debug binaries for multiple operating
22049 system targets, either via remote debugging or native emulation.
22050 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22051 but you can override its conclusion using the @code{set osabi} command.
22052 One example where this is useful is in debugging of binaries which use
22053 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22054 not have the same identifying marks that the standard C library for your
22057 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22058 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22059 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22060 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22064 Show the OS ABI currently in use.
22067 With no argument, show the list of registered available OS ABI's.
22069 @item set osabi @var{abi}
22070 Set the current OS ABI to @var{abi}.
22073 @cindex float promotion
22075 Generally, the way that an argument of type @code{float} is passed to a
22076 function depends on whether the function is prototyped. For a prototyped
22077 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22078 according to the architecture's convention for @code{float}. For unprototyped
22079 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22080 @code{double} and then passed.
22082 Unfortunately, some forms of debug information do not reliably indicate whether
22083 a function is prototyped. If @value{GDBN} calls a function that is not marked
22084 as prototyped, it consults @kbd{set coerce-float-to-double}.
22087 @kindex set coerce-float-to-double
22088 @item set coerce-float-to-double
22089 @itemx set coerce-float-to-double on
22090 Arguments of type @code{float} will be promoted to @code{double} when passed
22091 to an unprototyped function. This is the default setting.
22093 @item set coerce-float-to-double off
22094 Arguments of type @code{float} will be passed directly to unprototyped
22097 @kindex show coerce-float-to-double
22098 @item show coerce-float-to-double
22099 Show the current setting of promoting @code{float} to @code{double}.
22103 @kindex show cp-abi
22104 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22105 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22106 used to build your application. @value{GDBN} only fully supports
22107 programs with a single C@t{++} ABI; if your program contains code using
22108 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22109 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22110 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22111 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22112 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22113 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22118 Show the C@t{++} ABI currently in use.
22121 With no argument, show the list of supported C@t{++} ABI's.
22123 @item set cp-abi @var{abi}
22124 @itemx set cp-abi auto
22125 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22129 @section Automatically loading associated files
22130 @cindex auto-loading
22132 @value{GDBN} sometimes reads files with commands and settings automatically,
22133 without being explicitly told so by the user. We call this feature
22134 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22135 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22136 results or introduce security risks (e.g., if the file comes from untrusted
22139 Note that loading of these associated files (including the local @file{.gdbinit}
22140 file) requires accordingly configured @code{auto-load safe-path}
22141 (@pxref{Auto-loading safe path}).
22143 For these reasons, @value{GDBN} includes commands and options to let you
22144 control when to auto-load files and which files should be auto-loaded.
22147 @anchor{set auto-load off}
22148 @kindex set auto-load off
22149 @item set auto-load off
22150 Globally disable loading of all auto-loaded files.
22151 You may want to use this command with the @samp{-iex} option
22152 (@pxref{Option -init-eval-command}) such as:
22154 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22157 Be aware that system init file (@pxref{System-wide configuration})
22158 and init files from your home directory (@pxref{Home Directory Init File})
22159 still get read (as they come from generally trusted directories).
22160 To prevent @value{GDBN} from auto-loading even those init files, use the
22161 @option{-nx} option (@pxref{Mode Options}), in addition to
22162 @code{set auto-load no}.
22164 @anchor{show auto-load}
22165 @kindex show auto-load
22166 @item show auto-load
22167 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22171 (gdb) show auto-load
22172 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22173 libthread-db: Auto-loading of inferior specific libthread_db is on.
22174 local-gdbinit: Auto-loading of .gdbinit script from current directory
22176 python-scripts: Auto-loading of Python scripts is on.
22177 safe-path: List of directories from which it is safe to auto-load files
22178 is $debugdir:$datadir/auto-load.
22179 scripts-directory: List of directories from which to load auto-loaded scripts
22180 is $debugdir:$datadir/auto-load.
22183 @anchor{info auto-load}
22184 @kindex info auto-load
22185 @item info auto-load
22186 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22190 (gdb) info auto-load
22193 Yes /home/user/gdb/gdb-gdb.gdb
22194 libthread-db: No auto-loaded libthread-db.
22195 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22199 Yes /home/user/gdb/gdb-gdb.py
22203 These are various kinds of files @value{GDBN} can automatically load:
22207 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
22209 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
22211 @xref{dotdebug_gdb_scripts section},
22212 controlled by @ref{set auto-load python-scripts}.
22214 @xref{Init File in the Current Directory},
22215 controlled by @ref{set auto-load local-gdbinit}.
22217 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
22220 These are @value{GDBN} control commands for the auto-loading:
22222 @multitable @columnfractions .5 .5
22223 @item @xref{set auto-load off}.
22224 @tab Disable auto-loading globally.
22225 @item @xref{show auto-load}.
22226 @tab Show setting of all kinds of files.
22227 @item @xref{info auto-load}.
22228 @tab Show state of all kinds of files.
22229 @item @xref{set auto-load gdb-scripts}.
22230 @tab Control for @value{GDBN} command scripts.
22231 @item @xref{show auto-load gdb-scripts}.
22232 @tab Show setting of @value{GDBN} command scripts.
22233 @item @xref{info auto-load gdb-scripts}.
22234 @tab Show state of @value{GDBN} command scripts.
22235 @item @xref{set auto-load python-scripts}.
22236 @tab Control for @value{GDBN} Python scripts.
22237 @item @xref{show auto-load python-scripts}.
22238 @tab Show setting of @value{GDBN} Python scripts.
22239 @item @xref{info auto-load python-scripts}.
22240 @tab Show state of @value{GDBN} Python scripts.
22241 @item @xref{set auto-load scripts-directory}.
22242 @tab Control for @value{GDBN} auto-loaded scripts location.
22243 @item @xref{show auto-load scripts-directory}.
22244 @tab Show @value{GDBN} auto-loaded scripts location.
22245 @item @xref{set auto-load local-gdbinit}.
22246 @tab Control for init file in the current directory.
22247 @item @xref{show auto-load local-gdbinit}.
22248 @tab Show setting of init file in the current directory.
22249 @item @xref{info auto-load local-gdbinit}.
22250 @tab Show state of init file in the current directory.
22251 @item @xref{set auto-load libthread-db}.
22252 @tab Control for thread debugging library.
22253 @item @xref{show auto-load libthread-db}.
22254 @tab Show setting of thread debugging library.
22255 @item @xref{info auto-load libthread-db}.
22256 @tab Show state of thread debugging library.
22257 @item @xref{set auto-load safe-path}.
22258 @tab Control directories trusted for automatic loading.
22259 @item @xref{show auto-load safe-path}.
22260 @tab Show directories trusted for automatic loading.
22261 @item @xref{add-auto-load-safe-path}.
22262 @tab Add directory trusted for automatic loading.
22266 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22267 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22268 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
22269 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22270 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22271 @xref{Python Auto-loading}.
22274 @node Init File in the Current Directory
22275 @subsection Automatically loading init file in the current directory
22276 @cindex auto-loading init file in the current directory
22278 By default, @value{GDBN} reads and executes the canned sequences of commands
22279 from init file (if any) in the current working directory,
22280 see @ref{Init File in the Current Directory during Startup}.
22282 Note that loading of this local @file{.gdbinit} file also requires accordingly
22283 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22286 @anchor{set auto-load local-gdbinit}
22287 @kindex set auto-load local-gdbinit
22288 @item set auto-load local-gdbinit [on|off]
22289 Enable or disable the auto-loading of canned sequences of commands
22290 (@pxref{Sequences}) found in init file in the current directory.
22292 @anchor{show auto-load local-gdbinit}
22293 @kindex show auto-load local-gdbinit
22294 @item show auto-load local-gdbinit
22295 Show whether auto-loading of canned sequences of commands from init file in the
22296 current directory is enabled or disabled.
22298 @anchor{info auto-load local-gdbinit}
22299 @kindex info auto-load local-gdbinit
22300 @item info auto-load local-gdbinit
22301 Print whether canned sequences of commands from init file in the
22302 current directory have been auto-loaded.
22305 @node libthread_db.so.1 file
22306 @subsection Automatically loading thread debugging library
22307 @cindex auto-loading libthread_db.so.1
22309 This feature is currently present only on @sc{gnu}/Linux native hosts.
22311 @value{GDBN} reads in some cases thread debugging library from places specific
22312 to the inferior (@pxref{set libthread-db-search-path}).
22314 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22315 without checking this @samp{set auto-load libthread-db} switch as system
22316 libraries have to be trusted in general. In all other cases of
22317 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22318 auto-load libthread-db} is enabled before trying to open such thread debugging
22321 Note that loading of this debugging library also requires accordingly configured
22322 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22325 @anchor{set auto-load libthread-db}
22326 @kindex set auto-load libthread-db
22327 @item set auto-load libthread-db [on|off]
22328 Enable or disable the auto-loading of inferior specific thread debugging library.
22330 @anchor{show auto-load libthread-db}
22331 @kindex show auto-load libthread-db
22332 @item show auto-load libthread-db
22333 Show whether auto-loading of inferior specific thread debugging library is
22334 enabled or disabled.
22336 @anchor{info auto-load libthread-db}
22337 @kindex info auto-load libthread-db
22338 @item info auto-load libthread-db
22339 Print the list of all loaded inferior specific thread debugging libraries and
22340 for each such library print list of inferior @var{pid}s using it.
22343 @node objfile-gdb.gdb file
22344 @subsection The @file{@var{objfile}-gdb.gdb} file
22345 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
22347 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
22348 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
22349 auto-load gdb-scripts} is set to @samp{on}.
22351 Note that loading of this script file also requires accordingly configured
22352 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22354 For more background refer to the similar Python scripts auto-loading
22355 description (@pxref{objfile-gdb.py file}).
22358 @anchor{set auto-load gdb-scripts}
22359 @kindex set auto-load gdb-scripts
22360 @item set auto-load gdb-scripts [on|off]
22361 Enable or disable the auto-loading of canned sequences of commands scripts.
22363 @anchor{show auto-load gdb-scripts}
22364 @kindex show auto-load gdb-scripts
22365 @item show auto-load gdb-scripts
22366 Show whether auto-loading of canned sequences of commands scripts is enabled or
22369 @anchor{info auto-load gdb-scripts}
22370 @kindex info auto-load gdb-scripts
22371 @cindex print list of auto-loaded canned sequences of commands scripts
22372 @item info auto-load gdb-scripts [@var{regexp}]
22373 Print the list of all canned sequences of commands scripts that @value{GDBN}
22377 If @var{regexp} is supplied only canned sequences of commands scripts with
22378 matching names are printed.
22380 @node Auto-loading safe path
22381 @subsection Security restriction for auto-loading
22382 @cindex auto-loading safe-path
22384 As the files of inferior can come from untrusted source (such as submitted by
22385 an application user) @value{GDBN} does not always load any files automatically.
22386 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22387 directories trusted for loading files not explicitly requested by user.
22388 Each directory can also be a shell wildcard pattern.
22390 If the path is not set properly you will see a warning and the file will not
22395 Reading symbols from /home/user/gdb/gdb...done.
22396 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22397 declined by your `auto-load safe-path' set
22398 to "$debugdir:$datadir/auto-load".
22399 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22400 declined by your `auto-load safe-path' set
22401 to "$debugdir:$datadir/auto-load".
22405 To instruct @value{GDBN} to go ahead and use the init files anyway,
22406 invoke @value{GDBN} like this:
22409 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22412 The list of trusted directories is controlled by the following commands:
22415 @anchor{set auto-load safe-path}
22416 @kindex set auto-load safe-path
22417 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22418 Set the list of directories (and their subdirectories) trusted for automatic
22419 loading and execution of scripts. You can also enter a specific trusted file.
22420 Each directory can also be a shell wildcard pattern; wildcards do not match
22421 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22422 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22423 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22424 its default value as specified during @value{GDBN} compilation.
22426 The list of directories uses path separator (@samp{:} on GNU and Unix
22427 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22428 to the @env{PATH} environment variable.
22430 @anchor{show auto-load safe-path}
22431 @kindex show auto-load safe-path
22432 @item show auto-load safe-path
22433 Show the list of directories trusted for automatic loading and execution of
22436 @anchor{add-auto-load-safe-path}
22437 @kindex add-auto-load-safe-path
22438 @item add-auto-load-safe-path
22439 Add an entry (or list of entries) the list of directories trusted for automatic
22440 loading and execution of scripts. Multiple entries may be delimited by the
22441 host platform path separator in use.
22444 This variable defaults to what @code{--with-auto-load-dir} has been configured
22445 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22446 substitution applies the same as for @ref{set auto-load scripts-directory}.
22447 The default @code{set auto-load safe-path} value can be also overriden by
22448 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22450 Setting this variable to @file{/} disables this security protection,
22451 corresponding @value{GDBN} configuration option is
22452 @option{--without-auto-load-safe-path}.
22453 This variable is supposed to be set to the system directories writable by the
22454 system superuser only. Users can add their source directories in init files in
22455 their home directories (@pxref{Home Directory Init File}). See also deprecated
22456 init file in the current directory
22457 (@pxref{Init File in the Current Directory during Startup}).
22459 To force @value{GDBN} to load the files it declined to load in the previous
22460 example, you could use one of the following ways:
22463 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22464 Specify this trusted directory (or a file) as additional component of the list.
22465 You have to specify also any existing directories displayed by
22466 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22468 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22469 Specify this directory as in the previous case but just for a single
22470 @value{GDBN} session.
22472 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22473 Disable auto-loading safety for a single @value{GDBN} session.
22474 This assumes all the files you debug during this @value{GDBN} session will come
22475 from trusted sources.
22477 @item @kbd{./configure --without-auto-load-safe-path}
22478 During compilation of @value{GDBN} you may disable any auto-loading safety.
22479 This assumes all the files you will ever debug with this @value{GDBN} come from
22483 On the other hand you can also explicitly forbid automatic files loading which
22484 also suppresses any such warning messages:
22487 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22488 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22490 @item @file{~/.gdbinit}: @samp{set auto-load no}
22491 Disable auto-loading globally for the user
22492 (@pxref{Home Directory Init File}). While it is improbable, you could also
22493 use system init file instead (@pxref{System-wide configuration}).
22496 This setting applies to the file names as entered by user. If no entry matches
22497 @value{GDBN} tries as a last resort to also resolve all the file names into
22498 their canonical form (typically resolving symbolic links) and compare the
22499 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22500 own before starting the comparison so a canonical form of directories is
22501 recommended to be entered.
22503 @node Auto-loading verbose mode
22504 @subsection Displaying files tried for auto-load
22505 @cindex auto-loading verbose mode
22507 For better visibility of all the file locations where you can place scripts to
22508 be auto-loaded with inferior --- or to protect yourself against accidental
22509 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22510 all the files attempted to be loaded. Both existing and non-existing files may
22513 For example the list of directories from which it is safe to auto-load files
22514 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22515 may not be too obvious while setting it up.
22518 (gdb) set debug auto-load on
22519 (gdb) file ~/src/t/true
22520 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22521 for objfile "/tmp/true".
22522 auto-load: Updating directories of "/usr:/opt".
22523 auto-load: Using directory "/usr".
22524 auto-load: Using directory "/opt".
22525 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22526 by your `auto-load safe-path' set to "/usr:/opt".
22530 @anchor{set debug auto-load}
22531 @kindex set debug auto-load
22532 @item set debug auto-load [on|off]
22533 Set whether to print the filenames attempted to be auto-loaded.
22535 @anchor{show debug auto-load}
22536 @kindex show debug auto-load
22537 @item show debug auto-load
22538 Show whether printing of the filenames attempted to be auto-loaded is turned
22542 @node Messages/Warnings
22543 @section Optional Warnings and Messages
22545 @cindex verbose operation
22546 @cindex optional warnings
22547 By default, @value{GDBN} is silent about its inner workings. If you are
22548 running on a slow machine, you may want to use the @code{set verbose}
22549 command. This makes @value{GDBN} tell you when it does a lengthy
22550 internal operation, so you will not think it has crashed.
22552 Currently, the messages controlled by @code{set verbose} are those
22553 which announce that the symbol table for a source file is being read;
22554 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22557 @kindex set verbose
22558 @item set verbose on
22559 Enables @value{GDBN} output of certain informational messages.
22561 @item set verbose off
22562 Disables @value{GDBN} output of certain informational messages.
22564 @kindex show verbose
22566 Displays whether @code{set verbose} is on or off.
22569 By default, if @value{GDBN} encounters bugs in the symbol table of an
22570 object file, it is silent; but if you are debugging a compiler, you may
22571 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22576 @kindex set complaints
22577 @item set complaints @var{limit}
22578 Permits @value{GDBN} to output @var{limit} complaints about each type of
22579 unusual symbols before becoming silent about the problem. Set
22580 @var{limit} to zero to suppress all complaints; set it to a large number
22581 to prevent complaints from being suppressed.
22583 @kindex show complaints
22584 @item show complaints
22585 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22589 @anchor{confirmation requests}
22590 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22591 lot of stupid questions to confirm certain commands. For example, if
22592 you try to run a program which is already running:
22596 The program being debugged has been started already.
22597 Start it from the beginning? (y or n)
22600 If you are willing to unflinchingly face the consequences of your own
22601 commands, you can disable this ``feature'':
22605 @kindex set confirm
22607 @cindex confirmation
22608 @cindex stupid questions
22609 @item set confirm off
22610 Disables confirmation requests. Note that running @value{GDBN} with
22611 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22612 automatically disables confirmation requests.
22614 @item set confirm on
22615 Enables confirmation requests (the default).
22617 @kindex show confirm
22619 Displays state of confirmation requests.
22623 @cindex command tracing
22624 If you need to debug user-defined commands or sourced files you may find it
22625 useful to enable @dfn{command tracing}. In this mode each command will be
22626 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22627 quantity denoting the call depth of each command.
22630 @kindex set trace-commands
22631 @cindex command scripts, debugging
22632 @item set trace-commands on
22633 Enable command tracing.
22634 @item set trace-commands off
22635 Disable command tracing.
22636 @item show trace-commands
22637 Display the current state of command tracing.
22640 @node Debugging Output
22641 @section Optional Messages about Internal Happenings
22642 @cindex optional debugging messages
22644 @value{GDBN} has commands that enable optional debugging messages from
22645 various @value{GDBN} subsystems; normally these commands are of
22646 interest to @value{GDBN} maintainers, or when reporting a bug. This
22647 section documents those commands.
22650 @kindex set exec-done-display
22651 @item set exec-done-display
22652 Turns on or off the notification of asynchronous commands'
22653 completion. When on, @value{GDBN} will print a message when an
22654 asynchronous command finishes its execution. The default is off.
22655 @kindex show exec-done-display
22656 @item show exec-done-display
22657 Displays the current setting of asynchronous command completion
22660 @cindex ARM AArch64
22661 @item set debug aarch64
22662 Turns on or off display of debugging messages related to ARM AArch64.
22663 The default is off.
22665 @item show debug aarch64
22666 Displays the current state of displaying debugging messages related to
22668 @cindex gdbarch debugging info
22669 @cindex architecture debugging info
22670 @item set debug arch
22671 Turns on or off display of gdbarch debugging info. The default is off
22672 @item show debug arch
22673 Displays the current state of displaying gdbarch debugging info.
22674 @item set debug aix-solib
22675 @cindex AIX shared library debugging
22676 Control display of debugging messages from the AIX shared library
22677 support module. The default is off.
22678 @item show debug aix-thread
22679 Show the current state of displaying AIX shared library debugging messages.
22680 @item set debug aix-thread
22681 @cindex AIX threads
22682 Display debugging messages about inner workings of the AIX thread
22684 @item show debug aix-thread
22685 Show the current state of AIX thread debugging info display.
22686 @item set debug check-physname
22688 Check the results of the ``physname'' computation. When reading DWARF
22689 debugging information for C@t{++}, @value{GDBN} attempts to compute
22690 each entity's name. @value{GDBN} can do this computation in two
22691 different ways, depending on exactly what information is present.
22692 When enabled, this setting causes @value{GDBN} to compute the names
22693 both ways and display any discrepancies.
22694 @item show debug check-physname
22695 Show the current state of ``physname'' checking.
22696 @item set debug coff-pe-read
22697 @cindex COFF/PE exported symbols
22698 Control display of debugging messages related to reading of COFF/PE
22699 exported symbols. The default is off.
22700 @item show debug coff-pe-read
22701 Displays the current state of displaying debugging messages related to
22702 reading of COFF/PE exported symbols.
22703 @item set debug dwarf2-die
22704 @cindex DWARF2 DIEs
22705 Dump DWARF2 DIEs after they are read in.
22706 The value is the number of nesting levels to print.
22707 A value of zero turns off the display.
22708 @item show debug dwarf2-die
22709 Show the current state of DWARF2 DIE debugging.
22710 @item set debug dwarf2-read
22711 @cindex DWARF2 Reading
22712 Turns on or off display of debugging messages related to reading
22713 DWARF debug info. The default is 0 (off).
22714 A value of 1 provides basic information.
22715 A value greater than 1 provides more verbose information.
22716 @item show debug dwarf2-read
22717 Show the current state of DWARF2 reader debugging.
22718 @item set debug displaced
22719 @cindex displaced stepping debugging info
22720 Turns on or off display of @value{GDBN} debugging info for the
22721 displaced stepping support. The default is off.
22722 @item show debug displaced
22723 Displays the current state of displaying @value{GDBN} debugging info
22724 related to displaced stepping.
22725 @item set debug event
22726 @cindex event debugging info
22727 Turns on or off display of @value{GDBN} event debugging info. The
22729 @item show debug event
22730 Displays the current state of displaying @value{GDBN} event debugging
22732 @item set debug expression
22733 @cindex expression debugging info
22734 Turns on or off display of debugging info about @value{GDBN}
22735 expression parsing. The default is off.
22736 @item show debug expression
22737 Displays the current state of displaying debugging info about
22738 @value{GDBN} expression parsing.
22739 @item set debug frame
22740 @cindex frame debugging info
22741 Turns on or off display of @value{GDBN} frame debugging info. The
22743 @item show debug frame
22744 Displays the current state of displaying @value{GDBN} frame debugging
22746 @item set debug gnu-nat
22747 @cindex @sc{gnu}/Hurd debug messages
22748 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22749 @item show debug gnu-nat
22750 Show the current state of @sc{gnu}/Hurd debugging messages.
22751 @item set debug infrun
22752 @cindex inferior debugging info
22753 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22754 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22755 for implementing operations such as single-stepping the inferior.
22756 @item show debug infrun
22757 Displays the current state of @value{GDBN} inferior debugging.
22758 @item set debug jit
22759 @cindex just-in-time compilation, debugging messages
22760 Turns on or off debugging messages from JIT debug support.
22761 @item show debug jit
22762 Displays the current state of @value{GDBN} JIT debugging.
22763 @item set debug lin-lwp
22764 @cindex @sc{gnu}/Linux LWP debug messages
22765 @cindex Linux lightweight processes
22766 Turns on or off debugging messages from the Linux LWP debug support.
22767 @item show debug lin-lwp
22768 Show the current state of Linux LWP debugging messages.
22769 @item set debug mach-o
22770 @cindex Mach-O symbols processing
22771 Control display of debugging messages related to Mach-O symbols
22772 processing. The default is off.
22773 @item show debug mach-o
22774 Displays the current state of displaying debugging messages related to
22775 reading of COFF/PE exported symbols.
22776 @item set debug notification
22777 @cindex remote async notification debugging info
22778 Turns on or off debugging messages about remote async notification.
22779 The default is off.
22780 @item show debug notification
22781 Displays the current state of remote async notification debugging messages.
22782 @item set debug observer
22783 @cindex observer debugging info
22784 Turns on or off display of @value{GDBN} observer debugging. This
22785 includes info such as the notification of observable events.
22786 @item show debug observer
22787 Displays the current state of observer debugging.
22788 @item set debug overload
22789 @cindex C@t{++} overload debugging info
22790 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22791 info. This includes info such as ranking of functions, etc. The default
22793 @item show debug overload
22794 Displays the current state of displaying @value{GDBN} C@t{++} overload
22796 @cindex expression parser, debugging info
22797 @cindex debug expression parser
22798 @item set debug parser
22799 Turns on or off the display of expression parser debugging output.
22800 Internally, this sets the @code{yydebug} variable in the expression
22801 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22802 details. The default is off.
22803 @item show debug parser
22804 Show the current state of expression parser debugging.
22805 @cindex packets, reporting on stdout
22806 @cindex serial connections, debugging
22807 @cindex debug remote protocol
22808 @cindex remote protocol debugging
22809 @cindex display remote packets
22810 @item set debug remote
22811 Turns on or off display of reports on all packets sent back and forth across
22812 the serial line to the remote machine. The info is printed on the
22813 @value{GDBN} standard output stream. The default is off.
22814 @item show debug remote
22815 Displays the state of display of remote packets.
22816 @item set debug serial
22817 Turns on or off display of @value{GDBN} serial debugging info. The
22819 @item show debug serial
22820 Displays the current state of displaying @value{GDBN} serial debugging
22822 @item set debug solib-frv
22823 @cindex FR-V shared-library debugging
22824 Turns on or off debugging messages for FR-V shared-library code.
22825 @item show debug solib-frv
22826 Display the current state of FR-V shared-library code debugging
22828 @item set debug symfile
22829 @cindex symbol file functions
22830 Turns on or off display of debugging messages related to symbol file functions.
22831 The default is off. @xref{Files}.
22832 @item show debug symfile
22833 Show the current state of symbol file debugging messages.
22834 @item set debug symtab-create
22835 @cindex symbol table creation
22836 Turns on or off display of debugging messages related to symbol table creation.
22837 The default is 0 (off).
22838 A value of 1 provides basic information.
22839 A value greater than 1 provides more verbose information.
22840 @item show debug symtab-create
22841 Show the current state of symbol table creation debugging.
22842 @item set debug target
22843 @cindex target debugging info
22844 Turns on or off display of @value{GDBN} target debugging info. This info
22845 includes what is going on at the target level of GDB, as it happens. The
22846 default is 0. Set it to 1 to track events, and to 2 to also track the
22847 value of large memory transfers. Changes to this flag do not take effect
22848 until the next time you connect to a target or use the @code{run} command.
22849 @item show debug target
22850 Displays the current state of displaying @value{GDBN} target debugging
22852 @item set debug timestamp
22853 @cindex timestampping debugging info
22854 Turns on or off display of timestamps with @value{GDBN} debugging info.
22855 When enabled, seconds and microseconds are displayed before each debugging
22857 @item show debug timestamp
22858 Displays the current state of displaying timestamps with @value{GDBN}
22860 @item set debugvarobj
22861 @cindex variable object debugging info
22862 Turns on or off display of @value{GDBN} variable object debugging
22863 info. The default is off.
22864 @item show debugvarobj
22865 Displays the current state of displaying @value{GDBN} variable object
22867 @item set debug xml
22868 @cindex XML parser debugging
22869 Turns on or off debugging messages for built-in XML parsers.
22870 @item show debug xml
22871 Displays the current state of XML debugging messages.
22874 @node Other Misc Settings
22875 @section Other Miscellaneous Settings
22876 @cindex miscellaneous settings
22879 @kindex set interactive-mode
22880 @item set interactive-mode
22881 If @code{on}, forces @value{GDBN} to assume that GDB was started
22882 in a terminal. In practice, this means that @value{GDBN} should wait
22883 for the user to answer queries generated by commands entered at
22884 the command prompt. If @code{off}, forces @value{GDBN} to operate
22885 in the opposite mode, and it uses the default answers to all queries.
22886 If @code{auto} (the default), @value{GDBN} tries to determine whether
22887 its standard input is a terminal, and works in interactive-mode if it
22888 is, non-interactively otherwise.
22890 In the vast majority of cases, the debugger should be able to guess
22891 correctly which mode should be used. But this setting can be useful
22892 in certain specific cases, such as running a MinGW @value{GDBN}
22893 inside a cygwin window.
22895 @kindex show interactive-mode
22896 @item show interactive-mode
22897 Displays whether the debugger is operating in interactive mode or not.
22900 @node Extending GDB
22901 @chapter Extending @value{GDBN}
22902 @cindex extending GDB
22904 @value{GDBN} provides three mechanisms for extension. The first is based
22905 on composition of @value{GDBN} commands, the second is based on the
22906 Python scripting language, and the third is for defining new aliases of
22909 To facilitate the use of the first two extensions, @value{GDBN} is capable
22910 of evaluating the contents of a file. When doing so, @value{GDBN}
22911 can recognize which scripting language is being used by looking at
22912 the filename extension. Files with an unrecognized filename extension
22913 are always treated as a @value{GDBN} Command Files.
22914 @xref{Command Files,, Command files}.
22916 You can control how @value{GDBN} evaluates these files with the following
22920 @kindex set script-extension
22921 @kindex show script-extension
22922 @item set script-extension off
22923 All scripts are always evaluated as @value{GDBN} Command Files.
22925 @item set script-extension soft
22926 The debugger determines the scripting language based on filename
22927 extension. If this scripting language is supported, @value{GDBN}
22928 evaluates the script using that language. Otherwise, it evaluates
22929 the file as a @value{GDBN} Command File.
22931 @item set script-extension strict
22932 The debugger determines the scripting language based on filename
22933 extension, and evaluates the script using that language. If the
22934 language is not supported, then the evaluation fails.
22936 @item show script-extension
22937 Display the current value of the @code{script-extension} option.
22942 * Sequences:: Canned Sequences of Commands
22943 * Python:: Scripting @value{GDBN} using Python
22944 * Aliases:: Creating new spellings of existing commands
22948 @section Canned Sequences of Commands
22950 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22951 Command Lists}), @value{GDBN} provides two ways to store sequences of
22952 commands for execution as a unit: user-defined commands and command
22956 * Define:: How to define your own commands
22957 * Hooks:: Hooks for user-defined commands
22958 * Command Files:: How to write scripts of commands to be stored in a file
22959 * Output:: Commands for controlled output
22963 @subsection User-defined Commands
22965 @cindex user-defined command
22966 @cindex arguments, to user-defined commands
22967 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22968 which you assign a new name as a command. This is done with the
22969 @code{define} command. User commands may accept up to 10 arguments
22970 separated by whitespace. Arguments are accessed within the user command
22971 via @code{$arg0@dots{}$arg9}. A trivial example:
22975 print $arg0 + $arg1 + $arg2
22980 To execute the command use:
22987 This defines the command @code{adder}, which prints the sum of
22988 its three arguments. Note the arguments are text substitutions, so they may
22989 reference variables, use complex expressions, or even perform inferior
22992 @cindex argument count in user-defined commands
22993 @cindex how many arguments (user-defined commands)
22994 In addition, @code{$argc} may be used to find out how many arguments have
22995 been passed. This expands to a number in the range 0@dots{}10.
23000 print $arg0 + $arg1
23003 print $arg0 + $arg1 + $arg2
23011 @item define @var{commandname}
23012 Define a command named @var{commandname}. If there is already a command
23013 by that name, you are asked to confirm that you want to redefine it.
23014 @var{commandname} may be a bare command name consisting of letters,
23015 numbers, dashes, and underscores. It may also start with any predefined
23016 prefix command. For example, @samp{define target my-target} creates
23017 a user-defined @samp{target my-target} command.
23019 The definition of the command is made up of other @value{GDBN} command lines,
23020 which are given following the @code{define} command. The end of these
23021 commands is marked by a line containing @code{end}.
23024 @kindex end@r{ (user-defined commands)}
23025 @item document @var{commandname}
23026 Document the user-defined command @var{commandname}, so that it can be
23027 accessed by @code{help}. The command @var{commandname} must already be
23028 defined. This command reads lines of documentation just as @code{define}
23029 reads the lines of the command definition, ending with @code{end}.
23030 After the @code{document} command is finished, @code{help} on command
23031 @var{commandname} displays the documentation you have written.
23033 You may use the @code{document} command again to change the
23034 documentation of a command. Redefining the command with @code{define}
23035 does not change the documentation.
23037 @kindex dont-repeat
23038 @cindex don't repeat command
23040 Used inside a user-defined command, this tells @value{GDBN} that this
23041 command should not be repeated when the user hits @key{RET}
23042 (@pxref{Command Syntax, repeat last command}).
23044 @kindex help user-defined
23045 @item help user-defined
23046 List all user-defined commands and all python commands defined in class
23047 COMAND_USER. The first line of the documentation or docstring is
23052 @itemx show user @var{commandname}
23053 Display the @value{GDBN} commands used to define @var{commandname} (but
23054 not its documentation). If no @var{commandname} is given, display the
23055 definitions for all user-defined commands.
23056 This does not work for user-defined python commands.
23058 @cindex infinite recursion in user-defined commands
23059 @kindex show max-user-call-depth
23060 @kindex set max-user-call-depth
23061 @item show max-user-call-depth
23062 @itemx set max-user-call-depth
23063 The value of @code{max-user-call-depth} controls how many recursion
23064 levels are allowed in user-defined commands before @value{GDBN} suspects an
23065 infinite recursion and aborts the command.
23066 This does not apply to user-defined python commands.
23069 In addition to the above commands, user-defined commands frequently
23070 use control flow commands, described in @ref{Command Files}.
23072 When user-defined commands are executed, the
23073 commands of the definition are not printed. An error in any command
23074 stops execution of the user-defined command.
23076 If used interactively, commands that would ask for confirmation proceed
23077 without asking when used inside a user-defined command. Many @value{GDBN}
23078 commands that normally print messages to say what they are doing omit the
23079 messages when used in a user-defined command.
23082 @subsection User-defined Command Hooks
23083 @cindex command hooks
23084 @cindex hooks, for commands
23085 @cindex hooks, pre-command
23088 You may define @dfn{hooks}, which are a special kind of user-defined
23089 command. Whenever you run the command @samp{foo}, if the user-defined
23090 command @samp{hook-foo} exists, it is executed (with no arguments)
23091 before that command.
23093 @cindex hooks, post-command
23095 A hook may also be defined which is run after the command you executed.
23096 Whenever you run the command @samp{foo}, if the user-defined command
23097 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23098 that command. Post-execution hooks may exist simultaneously with
23099 pre-execution hooks, for the same command.
23101 It is valid for a hook to call the command which it hooks. If this
23102 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23104 @c It would be nice if hookpost could be passed a parameter indicating
23105 @c if the command it hooks executed properly or not. FIXME!
23107 @kindex stop@r{, a pseudo-command}
23108 In addition, a pseudo-command, @samp{stop} exists. Defining
23109 (@samp{hook-stop}) makes the associated commands execute every time
23110 execution stops in your program: before breakpoint commands are run,
23111 displays are printed, or the stack frame is printed.
23113 For example, to ignore @code{SIGALRM} signals while
23114 single-stepping, but treat them normally during normal execution,
23119 handle SIGALRM nopass
23123 handle SIGALRM pass
23126 define hook-continue
23127 handle SIGALRM pass
23131 As a further example, to hook at the beginning and end of the @code{echo}
23132 command, and to add extra text to the beginning and end of the message,
23140 define hookpost-echo
23144 (@value{GDBP}) echo Hello World
23145 <<<---Hello World--->>>
23150 You can define a hook for any single-word command in @value{GDBN}, but
23151 not for command aliases; you should define a hook for the basic command
23152 name, e.g.@: @code{backtrace} rather than @code{bt}.
23153 @c FIXME! So how does Joe User discover whether a command is an alias
23155 You can hook a multi-word command by adding @code{hook-} or
23156 @code{hookpost-} to the last word of the command, e.g.@:
23157 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23159 If an error occurs during the execution of your hook, execution of
23160 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23161 (before the command that you actually typed had a chance to run).
23163 If you try to define a hook which does not match any known command, you
23164 get a warning from the @code{define} command.
23166 @node Command Files
23167 @subsection Command Files
23169 @cindex command files
23170 @cindex scripting commands
23171 A command file for @value{GDBN} is a text file made of lines that are
23172 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23173 also be included. An empty line in a command file does nothing; it
23174 does not mean to repeat the last command, as it would from the
23177 You can request the execution of a command file with the @code{source}
23178 command. Note that the @code{source} command is also used to evaluate
23179 scripts that are not Command Files. The exact behavior can be configured
23180 using the @code{script-extension} setting.
23181 @xref{Extending GDB,, Extending GDB}.
23185 @cindex execute commands from a file
23186 @item source [-s] [-v] @var{filename}
23187 Execute the command file @var{filename}.
23190 The lines in a command file are generally executed sequentially,
23191 unless the order of execution is changed by one of the
23192 @emph{flow-control commands} described below. The commands are not
23193 printed as they are executed. An error in any command terminates
23194 execution of the command file and control is returned to the console.
23196 @value{GDBN} first searches for @var{filename} in the current directory.
23197 If the file is not found there, and @var{filename} does not specify a
23198 directory, then @value{GDBN} also looks for the file on the source search path
23199 (specified with the @samp{directory} command);
23200 except that @file{$cdir} is not searched because the compilation directory
23201 is not relevant to scripts.
23203 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23204 on the search path even if @var{filename} specifies a directory.
23205 The search is done by appending @var{filename} to each element of the
23206 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23207 and the search path contains @file{/home/user} then @value{GDBN} will
23208 look for the script @file{/home/user/mylib/myscript}.
23209 The search is also done if @var{filename} is an absolute path.
23210 For example, if @var{filename} is @file{/tmp/myscript} and
23211 the search path contains @file{/home/user} then @value{GDBN} will
23212 look for the script @file{/home/user/tmp/myscript}.
23213 For DOS-like systems, if @var{filename} contains a drive specification,
23214 it is stripped before concatenation. For example, if @var{filename} is
23215 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23216 will look for the script @file{c:/tmp/myscript}.
23218 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23219 each command as it is executed. The option must be given before
23220 @var{filename}, and is interpreted as part of the filename anywhere else.
23222 Commands that would ask for confirmation if used interactively proceed
23223 without asking when used in a command file. Many @value{GDBN} commands that
23224 normally print messages to say what they are doing omit the messages
23225 when called from command files.
23227 @value{GDBN} also accepts command input from standard input. In this
23228 mode, normal output goes to standard output and error output goes to
23229 standard error. Errors in a command file supplied on standard input do
23230 not terminate execution of the command file---execution continues with
23234 gdb < cmds > log 2>&1
23237 (The syntax above will vary depending on the shell used.) This example
23238 will execute commands from the file @file{cmds}. All output and errors
23239 would be directed to @file{log}.
23241 Since commands stored on command files tend to be more general than
23242 commands typed interactively, they frequently need to deal with
23243 complicated situations, such as different or unexpected values of
23244 variables and symbols, changes in how the program being debugged is
23245 built, etc. @value{GDBN} provides a set of flow-control commands to
23246 deal with these complexities. Using these commands, you can write
23247 complex scripts that loop over data structures, execute commands
23248 conditionally, etc.
23255 This command allows to include in your script conditionally executed
23256 commands. The @code{if} command takes a single argument, which is an
23257 expression to evaluate. It is followed by a series of commands that
23258 are executed only if the expression is true (its value is nonzero).
23259 There can then optionally be an @code{else} line, followed by a series
23260 of commands that are only executed if the expression was false. The
23261 end of the list is marked by a line containing @code{end}.
23265 This command allows to write loops. Its syntax is similar to
23266 @code{if}: the command takes a single argument, which is an expression
23267 to evaluate, and must be followed by the commands to execute, one per
23268 line, terminated by an @code{end}. These commands are called the
23269 @dfn{body} of the loop. The commands in the body of @code{while} are
23270 executed repeatedly as long as the expression evaluates to true.
23274 This command exits the @code{while} loop in whose body it is included.
23275 Execution of the script continues after that @code{while}s @code{end}
23278 @kindex loop_continue
23279 @item loop_continue
23280 This command skips the execution of the rest of the body of commands
23281 in the @code{while} loop in whose body it is included. Execution
23282 branches to the beginning of the @code{while} loop, where it evaluates
23283 the controlling expression.
23285 @kindex end@r{ (if/else/while commands)}
23287 Terminate the block of commands that are the body of @code{if},
23288 @code{else}, or @code{while} flow-control commands.
23293 @subsection Commands for Controlled Output
23295 During the execution of a command file or a user-defined command, normal
23296 @value{GDBN} output is suppressed; the only output that appears is what is
23297 explicitly printed by the commands in the definition. This section
23298 describes three commands useful for generating exactly the output you
23303 @item echo @var{text}
23304 @c I do not consider backslash-space a standard C escape sequence
23305 @c because it is not in ANSI.
23306 Print @var{text}. Nonprinting characters can be included in
23307 @var{text} using C escape sequences, such as @samp{\n} to print a
23308 newline. @strong{No newline is printed unless you specify one.}
23309 In addition to the standard C escape sequences, a backslash followed
23310 by a space stands for a space. This is useful for displaying a
23311 string with spaces at the beginning or the end, since leading and
23312 trailing spaces are otherwise trimmed from all arguments.
23313 To print @samp{@w{ }and foo =@w{ }}, use the command
23314 @samp{echo \@w{ }and foo = \@w{ }}.
23316 A backslash at the end of @var{text} can be used, as in C, to continue
23317 the command onto subsequent lines. For example,
23320 echo This is some text\n\
23321 which is continued\n\
23322 onto several lines.\n
23325 produces the same output as
23328 echo This is some text\n
23329 echo which is continued\n
23330 echo onto several lines.\n
23334 @item output @var{expression}
23335 Print the value of @var{expression} and nothing but that value: no
23336 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23337 value history either. @xref{Expressions, ,Expressions}, for more information
23340 @item output/@var{fmt} @var{expression}
23341 Print the value of @var{expression} in format @var{fmt}. You can use
23342 the same formats as for @code{print}. @xref{Output Formats,,Output
23343 Formats}, for more information.
23346 @item printf @var{template}, @var{expressions}@dots{}
23347 Print the values of one or more @var{expressions} under the control of
23348 the string @var{template}. To print several values, make
23349 @var{expressions} be a comma-separated list of individual expressions,
23350 which may be either numbers or pointers. Their values are printed as
23351 specified by @var{template}, exactly as a C program would do by
23352 executing the code below:
23355 printf (@var{template}, @var{expressions}@dots{});
23358 As in @code{C} @code{printf}, ordinary characters in @var{template}
23359 are printed verbatim, while @dfn{conversion specification} introduced
23360 by the @samp{%} character cause subsequent @var{expressions} to be
23361 evaluated, their values converted and formatted according to type and
23362 style information encoded in the conversion specifications, and then
23365 For example, you can print two values in hex like this:
23368 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23371 @code{printf} supports all the standard @code{C} conversion
23372 specifications, including the flags and modifiers between the @samp{%}
23373 character and the conversion letter, with the following exceptions:
23377 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23380 The modifier @samp{*} is not supported for specifying precision or
23384 The @samp{'} flag (for separation of digits into groups according to
23385 @code{LC_NUMERIC'}) is not supported.
23388 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23392 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23395 The conversion letters @samp{a} and @samp{A} are not supported.
23399 Note that the @samp{ll} type modifier is supported only if the
23400 underlying @code{C} implementation used to build @value{GDBN} supports
23401 the @code{long long int} type, and the @samp{L} type modifier is
23402 supported only if @code{long double} type is available.
23404 As in @code{C}, @code{printf} supports simple backslash-escape
23405 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23406 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23407 single character. Octal and hexadecimal escape sequences are not
23410 Additionally, @code{printf} supports conversion specifications for DFP
23411 (@dfn{Decimal Floating Point}) types using the following length modifiers
23412 together with a floating point specifier.
23417 @samp{H} for printing @code{Decimal32} types.
23420 @samp{D} for printing @code{Decimal64} types.
23423 @samp{DD} for printing @code{Decimal128} types.
23426 If the underlying @code{C} implementation used to build @value{GDBN} has
23427 support for the three length modifiers for DFP types, other modifiers
23428 such as width and precision will also be available for @value{GDBN} to use.
23430 In case there is no such @code{C} support, no additional modifiers will be
23431 available and the value will be printed in the standard way.
23433 Here's an example of printing DFP types using the above conversion letters:
23435 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23439 @item eval @var{template}, @var{expressions}@dots{}
23440 Convert the values of one or more @var{expressions} under the control of
23441 the string @var{template} to a command line, and call it.
23446 @section Scripting @value{GDBN} using Python
23447 @cindex python scripting
23448 @cindex scripting with python
23450 You can script @value{GDBN} using the @uref{http://www.python.org/,
23451 Python programming language}. This feature is available only if
23452 @value{GDBN} was configured using @option{--with-python}.
23454 @cindex python directory
23455 Python scripts used by @value{GDBN} should be installed in
23456 @file{@var{data-directory}/python}, where @var{data-directory} is
23457 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
23458 This directory, known as the @dfn{python directory},
23459 is automatically added to the Python Search Path in order to allow
23460 the Python interpreter to locate all scripts installed at this location.
23462 Additionally, @value{GDBN} commands and convenience functions which
23463 are written in Python and are located in the
23464 @file{@var{data-directory}/python/gdb/command} or
23465 @file{@var{data-directory}/python/gdb/function} directories are
23466 automatically imported when @value{GDBN} starts.
23469 * Python Commands:: Accessing Python from @value{GDBN}.
23470 * Python API:: Accessing @value{GDBN} from Python.
23471 * Python Auto-loading:: Automatically loading Python code.
23472 * Python modules:: Python modules provided by @value{GDBN}.
23475 @node Python Commands
23476 @subsection Python Commands
23477 @cindex python commands
23478 @cindex commands to access python
23480 @value{GDBN} provides two commands for accessing the Python interpreter,
23481 and one related setting:
23484 @kindex python-interactive
23486 @item python-interactive @r{[}@var{command}@r{]}
23487 @itemx pi @r{[}@var{command}@r{]}
23488 Without an argument, the @code{python-interactive} command can be used
23489 to start an interactive Python prompt. To return to @value{GDBN},
23490 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
23492 Alternatively, a single-line Python command can be given as an
23493 argument and evaluated. If the command is an expression, the result
23494 will be printed; otherwise, nothing will be printed. For example:
23497 (@value{GDBP}) python-interactive 2 + 3
23503 @item python @r{[}@var{command}@r{]}
23504 @itemx py @r{[}@var{command}@r{]}
23505 The @code{python} command can be used to evaluate Python code.
23507 If given an argument, the @code{python} command will evaluate the
23508 argument as a Python command. For example:
23511 (@value{GDBP}) python print 23
23515 If you do not provide an argument to @code{python}, it will act as a
23516 multi-line command, like @code{define}. In this case, the Python
23517 script is made up of subsequent command lines, given after the
23518 @code{python} command. This command list is terminated using a line
23519 containing @code{end}. For example:
23522 (@value{GDBP}) python
23524 End with a line saying just "end".
23530 @kindex set python print-stack
23531 @item set python print-stack
23532 By default, @value{GDBN} will print only the message component of a
23533 Python exception when an error occurs in a Python script. This can be
23534 controlled using @code{set python print-stack}: if @code{full}, then
23535 full Python stack printing is enabled; if @code{none}, then Python stack
23536 and message printing is disabled; if @code{message}, the default, only
23537 the message component of the error is printed.
23540 It is also possible to execute a Python script from the @value{GDBN}
23544 @item source @file{script-name}
23545 The script name must end with @samp{.py} and @value{GDBN} must be configured
23546 to recognize the script language based on filename extension using
23547 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
23549 @item python execfile ("script-name")
23550 This method is based on the @code{execfile} Python built-in function,
23551 and thus is always available.
23555 @subsection Python API
23557 @cindex programming in python
23559 You can get quick online help for @value{GDBN}'s Python API by issuing
23560 the command @w{@kbd{python help (gdb)}}.
23562 Functions and methods which have two or more optional arguments allow
23563 them to be specified using keyword syntax. This allows passing some
23564 optional arguments while skipping others. Example:
23565 @w{@code{gdb.some_function ('foo', bar = 1, baz = 2)}}.
23568 * Basic Python:: Basic Python Functions.
23569 * Exception Handling:: How Python exceptions are translated.
23570 * Values From Inferior:: Python representation of values.
23571 * Types In Python:: Python representation of types.
23572 * Pretty Printing API:: Pretty-printing values.
23573 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
23574 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
23575 * Type Printing API:: Pretty-printing types.
23576 * Frame Filter API:: Filtering Frames.
23577 * Frame Decorator API:: Decorating Frames.
23578 * Writing a Frame Filter:: Writing a Frame Filter.
23579 * Inferiors In Python:: Python representation of inferiors (processes)
23580 * Events In Python:: Listening for events from @value{GDBN}.
23581 * Threads In Python:: Accessing inferior threads from Python.
23582 * Commands In Python:: Implementing new commands in Python.
23583 * Parameters In Python:: Adding new @value{GDBN} parameters.
23584 * Functions In Python:: Writing new convenience functions.
23585 * Progspaces In Python:: Program spaces.
23586 * Objfiles In Python:: Object files.
23587 * Frames In Python:: Accessing inferior stack frames from Python.
23588 * Blocks In Python:: Accessing blocks from Python.
23589 * Symbols In Python:: Python representation of symbols.
23590 * Symbol Tables In Python:: Python representation of symbol tables.
23591 * Line Tables In Python:: Python representation of line tables.
23592 * Breakpoints In Python:: Manipulating breakpoints using Python.
23593 * Finish Breakpoints in Python:: Setting Breakpoints on function return
23595 * Lazy Strings In Python:: Python representation of lazy strings.
23596 * Architectures In Python:: Python representation of architectures.
23600 @subsubsection Basic Python
23602 @cindex python stdout
23603 @cindex python pagination
23604 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
23605 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
23606 A Python program which outputs to one of these streams may have its
23607 output interrupted by the user (@pxref{Screen Size}). In this
23608 situation, a Python @code{KeyboardInterrupt} exception is thrown.
23610 Some care must be taken when writing Python code to run in
23611 @value{GDBN}. Two things worth noting in particular:
23615 @value{GDBN} install handlers for @code{SIGCHLD} and @code{SIGINT}.
23616 Python code must not override these, or even change the options using
23617 @code{sigaction}. If your program changes the handling of these
23618 signals, @value{GDBN} will most likely stop working correctly. Note
23619 that it is unfortunately common for GUI toolkits to install a
23620 @code{SIGCHLD} handler.
23623 @value{GDBN} takes care to mark its internal file descriptors as
23624 close-on-exec. However, this cannot be done in a thread-safe way on
23625 all platforms. Your Python programs should be aware of this and
23626 should both create new file descriptors with the close-on-exec flag
23627 set and arrange to close unneeded file descriptors before starting a
23631 @cindex python functions
23632 @cindex python module
23634 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23635 methods and classes added by @value{GDBN} are placed in this module.
23636 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23637 use in all scripts evaluated by the @code{python} command.
23639 @findex gdb.PYTHONDIR
23640 @defvar gdb.PYTHONDIR
23641 A string containing the python directory (@pxref{Python}).
23644 @findex gdb.execute
23645 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23646 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23647 If a GDB exception happens while @var{command} runs, it is
23648 translated as described in @ref{Exception Handling,,Exception Handling}.
23650 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23651 command as having originated from the user invoking it interactively.
23652 It must be a boolean value. If omitted, it defaults to @code{False}.
23654 By default, any output produced by @var{command} is sent to
23655 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23656 @code{True}, then output will be collected by @code{gdb.execute} and
23657 returned as a string. The default is @code{False}, in which case the
23658 return value is @code{None}. If @var{to_string} is @code{True}, the
23659 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23660 and height, and its pagination will be disabled; @pxref{Screen Size}.
23663 @findex gdb.breakpoints
23664 @defun gdb.breakpoints ()
23665 Return a sequence holding all of @value{GDBN}'s breakpoints.
23666 @xref{Breakpoints In Python}, for more information.
23669 @findex gdb.parameter
23670 @defun gdb.parameter (parameter)
23671 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23672 string naming the parameter to look up; @var{parameter} may contain
23673 spaces if the parameter has a multi-part name. For example,
23674 @samp{print object} is a valid parameter name.
23676 If the named parameter does not exist, this function throws a
23677 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23678 parameter's value is converted to a Python value of the appropriate
23679 type, and returned.
23682 @findex gdb.history
23683 @defun gdb.history (number)
23684 Return a value from @value{GDBN}'s value history (@pxref{Value
23685 History}). @var{number} indicates which history element to return.
23686 If @var{number} is negative, then @value{GDBN} will take its absolute value
23687 and count backward from the last element (i.e., the most recent element) to
23688 find the value to return. If @var{number} is zero, then @value{GDBN} will
23689 return the most recent element. If the element specified by @var{number}
23690 doesn't exist in the value history, a @code{gdb.error} exception will be
23693 If no exception is raised, the return value is always an instance of
23694 @code{gdb.Value} (@pxref{Values From Inferior}).
23697 @findex gdb.parse_and_eval
23698 @defun gdb.parse_and_eval (expression)
23699 Parse @var{expression} as an expression in the current language,
23700 evaluate it, and return the result as a @code{gdb.Value}.
23701 @var{expression} must be a string.
23703 This function can be useful when implementing a new command
23704 (@pxref{Commands In Python}), as it provides a way to parse the
23705 command's argument as an expression. It is also useful simply to
23706 compute values, for example, it is the only way to get the value of a
23707 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23710 @findex gdb.find_pc_line
23711 @defun gdb.find_pc_line (pc)
23712 Return the @code{gdb.Symtab_and_line} object corresponding to the
23713 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23714 value of @var{pc} is passed as an argument, then the @code{symtab} and
23715 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23716 will be @code{None} and 0 respectively.
23719 @findex gdb.post_event
23720 @defun gdb.post_event (event)
23721 Put @var{event}, a callable object taking no arguments, into
23722 @value{GDBN}'s internal event queue. This callable will be invoked at
23723 some later point, during @value{GDBN}'s event processing. Events
23724 posted using @code{post_event} will be run in the order in which they
23725 were posted; however, there is no way to know when they will be
23726 processed relative to other events inside @value{GDBN}.
23728 @value{GDBN} is not thread-safe. If your Python program uses multiple
23729 threads, you must be careful to only call @value{GDBN}-specific
23730 functions in the main @value{GDBN} thread. @code{post_event} ensures
23734 (@value{GDBP}) python
23738 > def __init__(self, message):
23739 > self.message = message;
23740 > def __call__(self):
23741 > gdb.write(self.message)
23743 >class MyThread1 (threading.Thread):
23745 > gdb.post_event(Writer("Hello "))
23747 >class MyThread2 (threading.Thread):
23749 > gdb.post_event(Writer("World\n"))
23751 >MyThread1().start()
23752 >MyThread2().start()
23754 (@value{GDBP}) Hello World
23759 @defun gdb.write (string @r{[}, stream{]})
23760 Print a string to @value{GDBN}'s paginated output stream. The
23761 optional @var{stream} determines the stream to print to. The default
23762 stream is @value{GDBN}'s standard output stream. Possible stream
23769 @value{GDBN}'s standard output stream.
23774 @value{GDBN}'s standard error stream.
23779 @value{GDBN}'s log stream (@pxref{Logging Output}).
23782 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23783 call this function and will automatically direct the output to the
23788 @defun gdb.flush ()
23789 Flush the buffer of a @value{GDBN} paginated stream so that the
23790 contents are displayed immediately. @value{GDBN} will flush the
23791 contents of a stream automatically when it encounters a newline in the
23792 buffer. The optional @var{stream} determines the stream to flush. The
23793 default stream is @value{GDBN}'s standard output stream. Possible
23800 @value{GDBN}'s standard output stream.
23805 @value{GDBN}'s standard error stream.
23810 @value{GDBN}'s log stream (@pxref{Logging Output}).
23814 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23815 call this function for the relevant stream.
23818 @findex gdb.target_charset
23819 @defun gdb.target_charset ()
23820 Return the name of the current target character set (@pxref{Character
23821 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23822 that @samp{auto} is never returned.
23825 @findex gdb.target_wide_charset
23826 @defun gdb.target_wide_charset ()
23827 Return the name of the current target wide character set
23828 (@pxref{Character Sets}). This differs from
23829 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23833 @findex gdb.solib_name
23834 @defun gdb.solib_name (address)
23835 Return the name of the shared library holding the given @var{address}
23836 as a string, or @code{None}.
23839 @findex gdb.decode_line
23840 @defun gdb.decode_line @r{[}expression@r{]}
23841 Return locations of the line specified by @var{expression}, or of the
23842 current line if no argument was given. This function returns a Python
23843 tuple containing two elements. The first element contains a string
23844 holding any unparsed section of @var{expression} (or @code{None} if
23845 the expression has been fully parsed). The second element contains
23846 either @code{None} or another tuple that contains all the locations
23847 that match the expression represented as @code{gdb.Symtab_and_line}
23848 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23849 provided, it is decoded the way that @value{GDBN}'s inbuilt
23850 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23853 @defun gdb.prompt_hook (current_prompt)
23854 @anchor{prompt_hook}
23856 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23857 assigned to this operation before a prompt is displayed by
23860 The parameter @code{current_prompt} contains the current @value{GDBN}
23861 prompt. This method must return a Python string, or @code{None}. If
23862 a string is returned, the @value{GDBN} prompt will be set to that
23863 string. If @code{None} is returned, @value{GDBN} will continue to use
23864 the current prompt.
23866 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23867 such as those used by readline for command input, and annotation
23868 related prompts are prohibited from being changed.
23871 @node Exception Handling
23872 @subsubsection Exception Handling
23873 @cindex python exceptions
23874 @cindex exceptions, python
23876 When executing the @code{python} command, Python exceptions
23877 uncaught within the Python code are translated to calls to
23878 @value{GDBN} error-reporting mechanism. If the command that called
23879 @code{python} does not handle the error, @value{GDBN} will
23880 terminate it and print an error message containing the Python
23881 exception name, the associated value, and the Python call stack
23882 backtrace at the point where the exception was raised. Example:
23885 (@value{GDBP}) python print foo
23886 Traceback (most recent call last):
23887 File "<string>", line 1, in <module>
23888 NameError: name 'foo' is not defined
23891 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23892 Python code are converted to Python exceptions. The type of the
23893 Python exception depends on the error.
23897 This is the base class for most exceptions generated by @value{GDBN}.
23898 It is derived from @code{RuntimeError}, for compatibility with earlier
23899 versions of @value{GDBN}.
23901 If an error occurring in @value{GDBN} does not fit into some more
23902 specific category, then the generated exception will have this type.
23904 @item gdb.MemoryError
23905 This is a subclass of @code{gdb.error} which is thrown when an
23906 operation tried to access invalid memory in the inferior.
23908 @item KeyboardInterrupt
23909 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23910 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23913 In all cases, your exception handler will see the @value{GDBN} error
23914 message as its value and the Python call stack backtrace at the Python
23915 statement closest to where the @value{GDBN} error occured as the
23918 @findex gdb.GdbError
23919 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23920 it is useful to be able to throw an exception that doesn't cause a
23921 traceback to be printed. For example, the user may have invoked the
23922 command incorrectly. Use the @code{gdb.GdbError} exception
23923 to handle this case. Example:
23927 >class HelloWorld (gdb.Command):
23928 > """Greet the whole world."""
23929 > def __init__ (self):
23930 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23931 > def invoke (self, args, from_tty):
23932 > argv = gdb.string_to_argv (args)
23933 > if len (argv) != 0:
23934 > raise gdb.GdbError ("hello-world takes no arguments")
23935 > print "Hello, World!"
23938 (gdb) hello-world 42
23939 hello-world takes no arguments
23942 @node Values From Inferior
23943 @subsubsection Values From Inferior
23944 @cindex values from inferior, with Python
23945 @cindex python, working with values from inferior
23947 @cindex @code{gdb.Value}
23948 @value{GDBN} provides values it obtains from the inferior program in
23949 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23950 for its internal bookkeeping of the inferior's values, and for
23951 fetching values when necessary.
23953 Inferior values that are simple scalars can be used directly in
23954 Python expressions that are valid for the value's data type. Here's
23955 an example for an integer or floating-point value @code{some_val}:
23962 As result of this, @code{bar} will also be a @code{gdb.Value} object
23963 whose values are of the same type as those of @code{some_val}.
23965 Inferior values that are structures or instances of some class can
23966 be accessed using the Python @dfn{dictionary syntax}. For example, if
23967 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23968 can access its @code{foo} element with:
23971 bar = some_val['foo']
23974 Again, @code{bar} will also be a @code{gdb.Value} object.
23976 A @code{gdb.Value} that represents a function can be executed via
23977 inferior function call. Any arguments provided to the call must match
23978 the function's prototype, and must be provided in the order specified
23981 For example, @code{some_val} is a @code{gdb.Value} instance
23982 representing a function that takes two integers as arguments. To
23983 execute this function, call it like so:
23986 result = some_val (10,20)
23989 Any values returned from a function call will be stored as a
23992 The following attributes are provided:
23994 @defvar Value.address
23995 If this object is addressable, this read-only attribute holds a
23996 @code{gdb.Value} object representing the address. Otherwise,
23997 this attribute holds @code{None}.
24000 @cindex optimized out value in Python
24001 @defvar Value.is_optimized_out
24002 This read-only boolean attribute is true if the compiler optimized out
24003 this value, thus it is not available for fetching from the inferior.
24007 The type of this @code{gdb.Value}. The value of this attribute is a
24008 @code{gdb.Type} object (@pxref{Types In Python}).
24011 @defvar Value.dynamic_type
24012 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
24013 type information (@acronym{RTTI}) to determine the dynamic type of the
24014 value. If this value is of class type, it will return the class in
24015 which the value is embedded, if any. If this value is of pointer or
24016 reference to a class type, it will compute the dynamic type of the
24017 referenced object, and return a pointer or reference to that type,
24018 respectively. In all other cases, it will return the value's static
24021 Note that this feature will only work when debugging a C@t{++} program
24022 that includes @acronym{RTTI} for the object in question. Otherwise,
24023 it will just return the static type of the value as in @kbd{ptype foo}
24024 (@pxref{Symbols, ptype}).
24027 @defvar Value.is_lazy
24028 The value of this read-only boolean attribute is @code{True} if this
24029 @code{gdb.Value} has not yet been fetched from the inferior.
24030 @value{GDBN} does not fetch values until necessary, for efficiency.
24034 myval = gdb.parse_and_eval ('somevar')
24037 The value of @code{somevar} is not fetched at this time. It will be
24038 fetched when the value is needed, or when the @code{fetch_lazy}
24042 The following methods are provided:
24044 @defun Value.__init__ (@var{val})
24045 Many Python values can be converted directly to a @code{gdb.Value} via
24046 this object initializer. Specifically:
24049 @item Python boolean
24050 A Python boolean is converted to the boolean type from the current
24053 @item Python integer
24054 A Python integer is converted to the C @code{long} type for the
24055 current architecture.
24058 A Python long is converted to the C @code{long long} type for the
24059 current architecture.
24062 A Python float is converted to the C @code{double} type for the
24063 current architecture.
24065 @item Python string
24066 A Python string is converted to a target string, using the current
24069 @item @code{gdb.Value}
24070 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
24072 @item @code{gdb.LazyString}
24073 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
24074 Python}), then the lazy string's @code{value} method is called, and
24075 its result is used.
24079 @defun Value.cast (type)
24080 Return a new instance of @code{gdb.Value} that is the result of
24081 casting this instance to the type described by @var{type}, which must
24082 be a @code{gdb.Type} object. If the cast cannot be performed for some
24083 reason, this method throws an exception.
24086 @defun Value.dereference ()
24087 For pointer data types, this method returns a new @code{gdb.Value} object
24088 whose contents is the object pointed to by the pointer. For example, if
24089 @code{foo} is a C pointer to an @code{int}, declared in your C program as
24096 then you can use the corresponding @code{gdb.Value} to access what
24097 @code{foo} points to like this:
24100 bar = foo.dereference ()
24103 The result @code{bar} will be a @code{gdb.Value} object holding the
24104 value pointed to by @code{foo}.
24106 A similar function @code{Value.referenced_value} exists which also
24107 returns @code{gdb.Value} objects corresonding to the values pointed to
24108 by pointer values (and additionally, values referenced by reference
24109 values). However, the behavior of @code{Value.dereference}
24110 differs from @code{Value.referenced_value} by the fact that the
24111 behavior of @code{Value.dereference} is identical to applying the C
24112 unary operator @code{*} on a given value. For example, consider a
24113 reference to a pointer @code{ptrref}, declared in your C@t{++} program
24117 typedef int *intptr;
24121 intptr &ptrref = ptr;
24124 Though @code{ptrref} is a reference value, one can apply the method
24125 @code{Value.dereference} to the @code{gdb.Value} object corresponding
24126 to it and obtain a @code{gdb.Value} which is identical to that
24127 corresponding to @code{val}. However, if you apply the method
24128 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
24129 object identical to that corresponding to @code{ptr}.
24132 py_ptrref = gdb.parse_and_eval ("ptrref")
24133 py_val = py_ptrref.dereference ()
24134 py_ptr = py_ptrref.referenced_value ()
24137 The @code{gdb.Value} object @code{py_val} is identical to that
24138 corresponding to @code{val}, and @code{py_ptr} is identical to that
24139 corresponding to @code{ptr}. In general, @code{Value.dereference} can
24140 be applied whenever the C unary operator @code{*} can be applied
24141 to the corresponding C value. For those cases where applying both
24142 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
24143 the results obtained need not be identical (as we have seen in the above
24144 example). The results are however identical when applied on
24145 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
24146 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
24149 @defun Value.referenced_value ()
24150 For pointer or reference data types, this method returns a new
24151 @code{gdb.Value} object corresponding to the value referenced by the
24152 pointer/reference value. For pointer data types,
24153 @code{Value.dereference} and @code{Value.referenced_value} produce
24154 identical results. The difference between these methods is that
24155 @code{Value.dereference} cannot get the values referenced by reference
24156 values. For example, consider a reference to an @code{int}, declared
24157 in your C@t{++} program as
24165 then applying @code{Value.dereference} to the @code{gdb.Value} object
24166 corresponding to @code{ref} will result in an error, while applying
24167 @code{Value.referenced_value} will result in a @code{gdb.Value} object
24168 identical to that corresponding to @code{val}.
24171 py_ref = gdb.parse_and_eval ("ref")
24172 er_ref = py_ref.dereference () # Results in error
24173 py_val = py_ref.referenced_value () # Returns the referenced value
24176 The @code{gdb.Value} object @code{py_val} is identical to that
24177 corresponding to @code{val}.
24180 @defun Value.dynamic_cast (type)
24181 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
24182 operator were used. Consult a C@t{++} reference for details.
24185 @defun Value.reinterpret_cast (type)
24186 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
24187 operator were used. Consult a C@t{++} reference for details.
24190 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
24191 If this @code{gdb.Value} represents a string, then this method
24192 converts the contents to a Python string. Otherwise, this method will
24193 throw an exception.
24195 Strings are recognized in a language-specific way; whether a given
24196 @code{gdb.Value} represents a string is determined by the current
24199 For C-like languages, a value is a string if it is a pointer to or an
24200 array of characters or ints. The string is assumed to be terminated
24201 by a zero of the appropriate width. However if the optional length
24202 argument is given, the string will be converted to that given length,
24203 ignoring any embedded zeros that the string may contain.
24205 If the optional @var{encoding} argument is given, it must be a string
24206 naming the encoding of the string in the @code{gdb.Value}, such as
24207 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
24208 the same encodings as the corresponding argument to Python's
24209 @code{string.decode} method, and the Python codec machinery will be used
24210 to convert the string. If @var{encoding} is not given, or if
24211 @var{encoding} is the empty string, then either the @code{target-charset}
24212 (@pxref{Character Sets}) will be used, or a language-specific encoding
24213 will be used, if the current language is able to supply one.
24215 The optional @var{errors} argument is the same as the corresponding
24216 argument to Python's @code{string.decode} method.
24218 If the optional @var{length} argument is given, the string will be
24219 fetched and converted to the given length.
24222 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
24223 If this @code{gdb.Value} represents a string, then this method
24224 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
24225 In Python}). Otherwise, this method will throw an exception.
24227 If the optional @var{encoding} argument is given, it must be a string
24228 naming the encoding of the @code{gdb.LazyString}. Some examples are:
24229 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
24230 @var{encoding} argument is an encoding that @value{GDBN} does
24231 recognize, @value{GDBN} will raise an error.
24233 When a lazy string is printed, the @value{GDBN} encoding machinery is
24234 used to convert the string during printing. If the optional
24235 @var{encoding} argument is not provided, or is an empty string,
24236 @value{GDBN} will automatically select the encoding most suitable for
24237 the string type. For further information on encoding in @value{GDBN}
24238 please see @ref{Character Sets}.
24240 If the optional @var{length} argument is given, the string will be
24241 fetched and encoded to the length of characters specified. If
24242 the @var{length} argument is not provided, the string will be fetched
24243 and encoded until a null of appropriate width is found.
24246 @defun Value.fetch_lazy ()
24247 If the @code{gdb.Value} object is currently a lazy value
24248 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
24249 fetched from the inferior. Any errors that occur in the process
24250 will produce a Python exception.
24252 If the @code{gdb.Value} object is not a lazy value, this method
24255 This method does not return a value.
24259 @node Types In Python
24260 @subsubsection Types In Python
24261 @cindex types in Python
24262 @cindex Python, working with types
24265 @value{GDBN} represents types from the inferior using the class
24268 The following type-related functions are available in the @code{gdb}
24271 @findex gdb.lookup_type
24272 @defun gdb.lookup_type (name @r{[}, block@r{]})
24273 This function looks up a type by name. @var{name} is the name of the
24274 type to look up. It must be a string.
24276 If @var{block} is given, then @var{name} is looked up in that scope.
24277 Otherwise, it is searched for globally.
24279 Ordinarily, this function will return an instance of @code{gdb.Type}.
24280 If the named type cannot be found, it will throw an exception.
24283 If the type is a structure or class type, or an enum type, the fields
24284 of that type can be accessed using the Python @dfn{dictionary syntax}.
24285 For example, if @code{some_type} is a @code{gdb.Type} instance holding
24286 a structure type, you can access its @code{foo} field with:
24289 bar = some_type['foo']
24292 @code{bar} will be a @code{gdb.Field} object; see below under the
24293 description of the @code{Type.fields} method for a description of the
24294 @code{gdb.Field} class.
24296 An instance of @code{Type} has the following attributes:
24299 The type code for this type. The type code will be one of the
24300 @code{TYPE_CODE_} constants defined below.
24303 @defvar Type.sizeof
24304 The size of this type, in target @code{char} units. Usually, a
24305 target's @code{char} type will be an 8-bit byte. However, on some
24306 unusual platforms, this type may have a different size.
24310 The tag name for this type. The tag name is the name after
24311 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
24312 languages have this concept. If this type has no tag name, then
24313 @code{None} is returned.
24316 The following methods are provided:
24318 @defun Type.fields ()
24319 For structure and union types, this method returns the fields. Range
24320 types have two fields, the minimum and maximum values. Enum types
24321 have one field per enum constant. Function and method types have one
24322 field per parameter. The base types of C@t{++} classes are also
24323 represented as fields. If the type has no fields, or does not fit
24324 into one of these categories, an empty sequence will be returned.
24326 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
24329 This attribute is not available for @code{static} fields (as in
24330 C@t{++} or Java). For non-@code{static} fields, the value is the bit
24331 position of the field. For @code{enum} fields, the value is the
24332 enumeration member's integer representation.
24335 The name of the field, or @code{None} for anonymous fields.
24338 This is @code{True} if the field is artificial, usually meaning that
24339 it was provided by the compiler and not the user. This attribute is
24340 always provided, and is @code{False} if the field is not artificial.
24342 @item is_base_class
24343 This is @code{True} if the field represents a base class of a C@t{++}
24344 structure. This attribute is always provided, and is @code{False}
24345 if the field is not a base class of the type that is the argument of
24346 @code{fields}, or if that type was not a C@t{++} class.
24349 If the field is packed, or is a bitfield, then this will have a
24350 non-zero value, which is the size of the field in bits. Otherwise,
24351 this will be zero; in this case the field's size is given by its type.
24354 The type of the field. This is usually an instance of @code{Type},
24355 but it can be @code{None} in some situations.
24359 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
24360 Return a new @code{gdb.Type} object which represents an array of this
24361 type. If one argument is given, it is the inclusive upper bound of
24362 the array; in this case the lower bound is zero. If two arguments are
24363 given, the first argument is the lower bound of the array, and the
24364 second argument is the upper bound of the array. An array's length
24365 must not be negative, but the bounds can be.
24368 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
24369 Return a new @code{gdb.Type} object which represents a vector of this
24370 type. If one argument is given, it is the inclusive upper bound of
24371 the vector; in this case the lower bound is zero. If two arguments are
24372 given, the first argument is the lower bound of the vector, and the
24373 second argument is the upper bound of the vector. A vector's length
24374 must not be negative, but the bounds can be.
24376 The difference between an @code{array} and a @code{vector} is that
24377 arrays behave like in C: when used in expressions they decay to a pointer
24378 to the first element whereas vectors are treated as first class values.
24381 @defun Type.const ()
24382 Return a new @code{gdb.Type} object which represents a
24383 @code{const}-qualified variant of this type.
24386 @defun Type.volatile ()
24387 Return a new @code{gdb.Type} object which represents a
24388 @code{volatile}-qualified variant of this type.
24391 @defun Type.unqualified ()
24392 Return a new @code{gdb.Type} object which represents an unqualified
24393 variant of this type. That is, the result is neither @code{const} nor
24397 @defun Type.range ()
24398 Return a Python @code{Tuple} object that contains two elements: the
24399 low bound of the argument type and the high bound of that type. If
24400 the type does not have a range, @value{GDBN} will raise a
24401 @code{gdb.error} exception (@pxref{Exception Handling}).
24404 @defun Type.reference ()
24405 Return a new @code{gdb.Type} object which represents a reference to this
24409 @defun Type.pointer ()
24410 Return a new @code{gdb.Type} object which represents a pointer to this
24414 @defun Type.strip_typedefs ()
24415 Return a new @code{gdb.Type} that represents the real type,
24416 after removing all layers of typedefs.
24419 @defun Type.target ()
24420 Return a new @code{gdb.Type} object which represents the target type
24423 For a pointer type, the target type is the type of the pointed-to
24424 object. For an array type (meaning C-like arrays), the target type is
24425 the type of the elements of the array. For a function or method type,
24426 the target type is the type of the return value. For a complex type,
24427 the target type is the type of the elements. For a typedef, the
24428 target type is the aliased type.
24430 If the type does not have a target, this method will throw an
24434 @defun Type.template_argument (n @r{[}, block@r{]})
24435 If this @code{gdb.Type} is an instantiation of a template, this will
24436 return a new @code{gdb.Type} which represents the type of the
24437 @var{n}th template argument.
24439 If this @code{gdb.Type} is not a template type, this will throw an
24440 exception. Ordinarily, only C@t{++} code will have template types.
24442 If @var{block} is given, then @var{name} is looked up in that scope.
24443 Otherwise, it is searched for globally.
24447 Each type has a code, which indicates what category this type falls
24448 into. The available type categories are represented by constants
24449 defined in the @code{gdb} module:
24452 @findex TYPE_CODE_PTR
24453 @findex gdb.TYPE_CODE_PTR
24454 @item gdb.TYPE_CODE_PTR
24455 The type is a pointer.
24457 @findex TYPE_CODE_ARRAY
24458 @findex gdb.TYPE_CODE_ARRAY
24459 @item gdb.TYPE_CODE_ARRAY
24460 The type is an array.
24462 @findex TYPE_CODE_STRUCT
24463 @findex gdb.TYPE_CODE_STRUCT
24464 @item gdb.TYPE_CODE_STRUCT
24465 The type is a structure.
24467 @findex TYPE_CODE_UNION
24468 @findex gdb.TYPE_CODE_UNION
24469 @item gdb.TYPE_CODE_UNION
24470 The type is a union.
24472 @findex TYPE_CODE_ENUM
24473 @findex gdb.TYPE_CODE_ENUM
24474 @item gdb.TYPE_CODE_ENUM
24475 The type is an enum.
24477 @findex TYPE_CODE_FLAGS
24478 @findex gdb.TYPE_CODE_FLAGS
24479 @item gdb.TYPE_CODE_FLAGS
24480 A bit flags type, used for things such as status registers.
24482 @findex TYPE_CODE_FUNC
24483 @findex gdb.TYPE_CODE_FUNC
24484 @item gdb.TYPE_CODE_FUNC
24485 The type is a function.
24487 @findex TYPE_CODE_INT
24488 @findex gdb.TYPE_CODE_INT
24489 @item gdb.TYPE_CODE_INT
24490 The type is an integer type.
24492 @findex TYPE_CODE_FLT
24493 @findex gdb.TYPE_CODE_FLT
24494 @item gdb.TYPE_CODE_FLT
24495 A floating point type.
24497 @findex TYPE_CODE_VOID
24498 @findex gdb.TYPE_CODE_VOID
24499 @item gdb.TYPE_CODE_VOID
24500 The special type @code{void}.
24502 @findex TYPE_CODE_SET
24503 @findex gdb.TYPE_CODE_SET
24504 @item gdb.TYPE_CODE_SET
24507 @findex TYPE_CODE_RANGE
24508 @findex gdb.TYPE_CODE_RANGE
24509 @item gdb.TYPE_CODE_RANGE
24510 A range type, that is, an integer type with bounds.
24512 @findex TYPE_CODE_STRING
24513 @findex gdb.TYPE_CODE_STRING
24514 @item gdb.TYPE_CODE_STRING
24515 A string type. Note that this is only used for certain languages with
24516 language-defined string types; C strings are not represented this way.
24518 @findex TYPE_CODE_BITSTRING
24519 @findex gdb.TYPE_CODE_BITSTRING
24520 @item gdb.TYPE_CODE_BITSTRING
24521 A string of bits. It is deprecated.
24523 @findex TYPE_CODE_ERROR
24524 @findex gdb.TYPE_CODE_ERROR
24525 @item gdb.TYPE_CODE_ERROR
24526 An unknown or erroneous type.
24528 @findex TYPE_CODE_METHOD
24529 @findex gdb.TYPE_CODE_METHOD
24530 @item gdb.TYPE_CODE_METHOD
24531 A method type, as found in C@t{++} or Java.
24533 @findex TYPE_CODE_METHODPTR
24534 @findex gdb.TYPE_CODE_METHODPTR
24535 @item gdb.TYPE_CODE_METHODPTR
24536 A pointer-to-member-function.
24538 @findex TYPE_CODE_MEMBERPTR
24539 @findex gdb.TYPE_CODE_MEMBERPTR
24540 @item gdb.TYPE_CODE_MEMBERPTR
24541 A pointer-to-member.
24543 @findex TYPE_CODE_REF
24544 @findex gdb.TYPE_CODE_REF
24545 @item gdb.TYPE_CODE_REF
24548 @findex TYPE_CODE_CHAR
24549 @findex gdb.TYPE_CODE_CHAR
24550 @item gdb.TYPE_CODE_CHAR
24553 @findex TYPE_CODE_BOOL
24554 @findex gdb.TYPE_CODE_BOOL
24555 @item gdb.TYPE_CODE_BOOL
24558 @findex TYPE_CODE_COMPLEX
24559 @findex gdb.TYPE_CODE_COMPLEX
24560 @item gdb.TYPE_CODE_COMPLEX
24561 A complex float type.
24563 @findex TYPE_CODE_TYPEDEF
24564 @findex gdb.TYPE_CODE_TYPEDEF
24565 @item gdb.TYPE_CODE_TYPEDEF
24566 A typedef to some other type.
24568 @findex TYPE_CODE_NAMESPACE
24569 @findex gdb.TYPE_CODE_NAMESPACE
24570 @item gdb.TYPE_CODE_NAMESPACE
24571 A C@t{++} namespace.
24573 @findex TYPE_CODE_DECFLOAT
24574 @findex gdb.TYPE_CODE_DECFLOAT
24575 @item gdb.TYPE_CODE_DECFLOAT
24576 A decimal floating point type.
24578 @findex TYPE_CODE_INTERNAL_FUNCTION
24579 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
24580 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
24581 A function internal to @value{GDBN}. This is the type used to represent
24582 convenience functions.
24585 Further support for types is provided in the @code{gdb.types}
24586 Python module (@pxref{gdb.types}).
24588 @node Pretty Printing API
24589 @subsubsection Pretty Printing API
24591 An example output is provided (@pxref{Pretty Printing}).
24593 A pretty-printer is just an object that holds a value and implements a
24594 specific interface, defined here.
24596 @defun pretty_printer.children (self)
24597 @value{GDBN} will call this method on a pretty-printer to compute the
24598 children of the pretty-printer's value.
24600 This method must return an object conforming to the Python iterator
24601 protocol. Each item returned by the iterator must be a tuple holding
24602 two elements. The first element is the ``name'' of the child; the
24603 second element is the child's value. The value can be any Python
24604 object which is convertible to a @value{GDBN} value.
24606 This method is optional. If it does not exist, @value{GDBN} will act
24607 as though the value has no children.
24610 @defun pretty_printer.display_hint (self)
24611 The CLI may call this method and use its result to change the
24612 formatting of a value. The result will also be supplied to an MI
24613 consumer as a @samp{displayhint} attribute of the variable being
24616 This method is optional. If it does exist, this method must return a
24619 Some display hints are predefined by @value{GDBN}:
24623 Indicate that the object being printed is ``array-like''. The CLI
24624 uses this to respect parameters such as @code{set print elements} and
24625 @code{set print array}.
24628 Indicate that the object being printed is ``map-like'', and that the
24629 children of this value can be assumed to alternate between keys and
24633 Indicate that the object being printed is ``string-like''. If the
24634 printer's @code{to_string} method returns a Python string of some
24635 kind, then @value{GDBN} will call its internal language-specific
24636 string-printing function to format the string. For the CLI this means
24637 adding quotation marks, possibly escaping some characters, respecting
24638 @code{set print elements}, and the like.
24642 @defun pretty_printer.to_string (self)
24643 @value{GDBN} will call this method to display the string
24644 representation of the value passed to the object's constructor.
24646 When printing from the CLI, if the @code{to_string} method exists,
24647 then @value{GDBN} will prepend its result to the values returned by
24648 @code{children}. Exactly how this formatting is done is dependent on
24649 the display hint, and may change as more hints are added. Also,
24650 depending on the print settings (@pxref{Print Settings}), the CLI may
24651 print just the result of @code{to_string} in a stack trace, omitting
24652 the result of @code{children}.
24654 If this method returns a string, it is printed verbatim.
24656 Otherwise, if this method returns an instance of @code{gdb.Value},
24657 then @value{GDBN} prints this value. This may result in a call to
24658 another pretty-printer.
24660 If instead the method returns a Python value which is convertible to a
24661 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24662 the resulting value. Again, this may result in a call to another
24663 pretty-printer. Python scalars (integers, floats, and booleans) and
24664 strings are convertible to @code{gdb.Value}; other types are not.
24666 Finally, if this method returns @code{None} then no further operations
24667 are peformed in this method and nothing is printed.
24669 If the result is not one of these types, an exception is raised.
24672 @value{GDBN} provides a function which can be used to look up the
24673 default pretty-printer for a @code{gdb.Value}:
24675 @findex gdb.default_visualizer
24676 @defun gdb.default_visualizer (value)
24677 This function takes a @code{gdb.Value} object as an argument. If a
24678 pretty-printer for this value exists, then it is returned. If no such
24679 printer exists, then this returns @code{None}.
24682 @node Selecting Pretty-Printers
24683 @subsubsection Selecting Pretty-Printers
24685 The Python list @code{gdb.pretty_printers} contains an array of
24686 functions or callable objects that have been registered via addition
24687 as a pretty-printer. Printers in this list are called @code{global}
24688 printers, they're available when debugging all inferiors.
24689 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24690 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24693 Each function on these lists is passed a single @code{gdb.Value}
24694 argument and should return a pretty-printer object conforming to the
24695 interface definition above (@pxref{Pretty Printing API}). If a function
24696 cannot create a pretty-printer for the value, it should return
24699 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24700 @code{gdb.Objfile} in the current program space and iteratively calls
24701 each enabled lookup routine in the list for that @code{gdb.Objfile}
24702 until it receives a pretty-printer object.
24703 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24704 searches the pretty-printer list of the current program space,
24705 calling each enabled function until an object is returned.
24706 After these lists have been exhausted, it tries the global
24707 @code{gdb.pretty_printers} list, again calling each enabled function until an
24708 object is returned.
24710 The order in which the objfiles are searched is not specified. For a
24711 given list, functions are always invoked from the head of the list,
24712 and iterated over sequentially until the end of the list, or a printer
24713 object is returned.
24715 For various reasons a pretty-printer may not work.
24716 For example, the underlying data structure may have changed and
24717 the pretty-printer is out of date.
24719 The consequences of a broken pretty-printer are severe enough that
24720 @value{GDBN} provides support for enabling and disabling individual
24721 printers. For example, if @code{print frame-arguments} is on,
24722 a backtrace can become highly illegible if any argument is printed
24723 with a broken printer.
24725 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24726 attribute to the registered function or callable object. If this attribute
24727 is present and its value is @code{False}, the printer is disabled, otherwise
24728 the printer is enabled.
24730 @node Writing a Pretty-Printer
24731 @subsubsection Writing a Pretty-Printer
24732 @cindex writing a pretty-printer
24734 A pretty-printer consists of two parts: a lookup function to detect
24735 if the type is supported, and the printer itself.
24737 Here is an example showing how a @code{std::string} printer might be
24738 written. @xref{Pretty Printing API}, for details on the API this class
24742 class StdStringPrinter(object):
24743 "Print a std::string"
24745 def __init__(self, val):
24748 def to_string(self):
24749 return self.val['_M_dataplus']['_M_p']
24751 def display_hint(self):
24755 And here is an example showing how a lookup function for the printer
24756 example above might be written.
24759 def str_lookup_function(val):
24760 lookup_tag = val.type.tag
24761 if lookup_tag == None:
24763 regex = re.compile("^std::basic_string<char,.*>$")
24764 if regex.match(lookup_tag):
24765 return StdStringPrinter(val)
24769 The example lookup function extracts the value's type, and attempts to
24770 match it to a type that it can pretty-print. If it is a type the
24771 printer can pretty-print, it will return a printer object. If not, it
24772 returns @code{None}.
24774 We recommend that you put your core pretty-printers into a Python
24775 package. If your pretty-printers are for use with a library, we
24776 further recommend embedding a version number into the package name.
24777 This practice will enable @value{GDBN} to load multiple versions of
24778 your pretty-printers at the same time, because they will have
24781 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24782 can be evaluated multiple times without changing its meaning. An
24783 ideal auto-load file will consist solely of @code{import}s of your
24784 printer modules, followed by a call to a register pretty-printers with
24785 the current objfile.
24787 Taken as a whole, this approach will scale nicely to multiple
24788 inferiors, each potentially using a different library version.
24789 Embedding a version number in the Python package name will ensure that
24790 @value{GDBN} is able to load both sets of printers simultaneously.
24791 Then, because the search for pretty-printers is done by objfile, and
24792 because your auto-loaded code took care to register your library's
24793 printers with a specific objfile, @value{GDBN} will find the correct
24794 printers for the specific version of the library used by each
24797 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24798 this code might appear in @code{gdb.libstdcxx.v6}:
24801 def register_printers(objfile):
24802 objfile.pretty_printers.append(str_lookup_function)
24806 And then the corresponding contents of the auto-load file would be:
24809 import gdb.libstdcxx.v6
24810 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24813 The previous example illustrates a basic pretty-printer.
24814 There are a few things that can be improved on.
24815 The printer doesn't have a name, making it hard to identify in a
24816 list of installed printers. The lookup function has a name, but
24817 lookup functions can have arbitrary, even identical, names.
24819 Second, the printer only handles one type, whereas a library typically has
24820 several types. One could install a lookup function for each desired type
24821 in the library, but one could also have a single lookup function recognize
24822 several types. The latter is the conventional way this is handled.
24823 If a pretty-printer can handle multiple data types, then its
24824 @dfn{subprinters} are the printers for the individual data types.
24826 The @code{gdb.printing} module provides a formal way of solving these
24827 problems (@pxref{gdb.printing}).
24828 Here is another example that handles multiple types.
24830 These are the types we are going to pretty-print:
24833 struct foo @{ int a, b; @};
24834 struct bar @{ struct foo x, y; @};
24837 Here are the printers:
24841 """Print a foo object."""
24843 def __init__(self, val):
24846 def to_string(self):
24847 return ("a=<" + str(self.val["a"]) +
24848 "> b=<" + str(self.val["b"]) + ">")
24851 """Print a bar object."""
24853 def __init__(self, val):
24856 def to_string(self):
24857 return ("x=<" + str(self.val["x"]) +
24858 "> y=<" + str(self.val["y"]) + ">")
24861 This example doesn't need a lookup function, that is handled by the
24862 @code{gdb.printing} module. Instead a function is provided to build up
24863 the object that handles the lookup.
24866 import gdb.printing
24868 def build_pretty_printer():
24869 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24871 pp.add_printer('foo', '^foo$', fooPrinter)
24872 pp.add_printer('bar', '^bar$', barPrinter)
24876 And here is the autoload support:
24879 import gdb.printing
24881 gdb.printing.register_pretty_printer(
24882 gdb.current_objfile(),
24883 my_library.build_pretty_printer())
24886 Finally, when this printer is loaded into @value{GDBN}, here is the
24887 corresponding output of @samp{info pretty-printer}:
24890 (gdb) info pretty-printer
24897 @node Type Printing API
24898 @subsubsection Type Printing API
24899 @cindex type printing API for Python
24901 @value{GDBN} provides a way for Python code to customize type display.
24902 This is mainly useful for substituting canonical typedef names for
24905 @cindex type printer
24906 A @dfn{type printer} is just a Python object conforming to a certain
24907 protocol. A simple base class implementing the protocol is provided;
24908 see @ref{gdb.types}. A type printer must supply at least:
24910 @defivar type_printer enabled
24911 A boolean which is True if the printer is enabled, and False
24912 otherwise. This is manipulated by the @code{enable type-printer}
24913 and @code{disable type-printer} commands.
24916 @defivar type_printer name
24917 The name of the type printer. This must be a string. This is used by
24918 the @code{enable type-printer} and @code{disable type-printer}
24922 @defmethod type_printer instantiate (self)
24923 This is called by @value{GDBN} at the start of type-printing. It is
24924 only called if the type printer is enabled. This method must return a
24925 new object that supplies a @code{recognize} method, as described below.
24929 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24930 will compute a list of type recognizers. This is done by iterating
24931 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24932 followed by the per-progspace type printers (@pxref{Progspaces In
24933 Python}), and finally the global type printers.
24935 @value{GDBN} will call the @code{instantiate} method of each enabled
24936 type printer. If this method returns @code{None}, then the result is
24937 ignored; otherwise, it is appended to the list of recognizers.
24939 Then, when @value{GDBN} is going to display a type name, it iterates
24940 over the list of recognizers. For each one, it calls the recognition
24941 function, stopping if the function returns a non-@code{None} value.
24942 The recognition function is defined as:
24944 @defmethod type_recognizer recognize (self, type)
24945 If @var{type} is not recognized, return @code{None}. Otherwise,
24946 return a string which is to be printed as the name of @var{type}.
24947 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24951 @value{GDBN} uses this two-pass approach so that type printers can
24952 efficiently cache information without holding on to it too long. For
24953 example, it can be convenient to look up type information in a type
24954 printer and hold it for a recognizer's lifetime; if a single pass were
24955 done then type printers would have to make use of the event system in
24956 order to avoid holding information that could become stale as the
24959 @node Frame Filter API
24960 @subsubsection Filtering Frames.
24961 @cindex frame filters api
24963 Frame filters are Python objects that manipulate the visibility of a
24964 frame or frames when a backtrace (@pxref{Backtrace}) is printed by
24967 Only commands that print a backtrace, or, in the case of @sc{gdb/mi}
24968 commands (@pxref{GDB/MI}), those that return a collection of frames
24969 are affected. The commands that work with frame filters are:
24971 @code{backtrace} (@pxref{backtrace-command,, The backtrace command}),
24972 @code{-stack-list-frames}
24973 (@pxref{-stack-list-frames,, The -stack-list-frames command}),
24974 @code{-stack-list-variables} (@pxref{-stack-list-variables,, The
24975 -stack-list-variables command}), @code{-stack-list-arguments}
24976 @pxref{-stack-list-arguments,, The -stack-list-arguments command}) and
24977 @code{-stack-list-locals} (@pxref{-stack-list-locals,, The
24978 -stack-list-locals command}).
24980 A frame filter works by taking an iterator as an argument, applying
24981 actions to the contents of that iterator, and returning another
24982 iterator (or, possibly, the same iterator it was provided in the case
24983 where the filter does not perform any operations). Typically, frame
24984 filters utilize tools such as the Python's @code{itertools} module to
24985 work with and create new iterators from the source iterator.
24986 Regardless of how a filter chooses to apply actions, it must not alter
24987 the underlying @value{GDBN} frame or frames, or attempt to alter the
24988 call-stack within @value{GDBN}. This preserves data integrity within
24989 @value{GDBN}. Frame filters are executed on a priority basis and care
24990 should be taken that some frame filters may have been executed before,
24991 and that some frame filters will be executed after.
24993 An important consideration when designing frame filters, and well
24994 worth reflecting upon, is that frame filters should avoid unwinding
24995 the call stack if possible. Some stacks can run very deep, into the
24996 tens of thousands in some cases. To search every frame when a frame
24997 filter executes may be too expensive at that step. The frame filter
24998 cannot know how many frames it has to iterate over, and it may have to
24999 iterate through them all. This ends up duplicating effort as
25000 @value{GDBN} performs this iteration when it prints the frames. If
25001 the filter can defer unwinding frames until frame decorators are
25002 executed, after the last filter has executed, it should. @xref{Frame
25003 Decorator API}, for more information on decorators. Also, there are
25004 examples for both frame decorators and filters in later chapters.
25005 @xref{Writing a Frame Filter}, for more information.
25007 The Python dictionary @code{gdb.frame_filters} contains key/object
25008 pairings that comprise a frame filter. Frame filters in this
25009 dictionary are called @code{global} frame filters, and they are
25010 available when debugging all inferiors. These frame filters must
25011 register with the dictionary directly. In addition to the
25012 @code{global} dictionary, there are other dictionaries that are loaded
25013 with different inferiors via auto-loading (@pxref{Python
25014 Auto-loading}). The two other areas where frame filter dictionaries
25015 can be found are: @code{gdb.Progspace} which contains a
25016 @code{frame_filters} dictionary attribute, and each @code{gdb.Objfile}
25017 object which also contains a @code{frame_filters} dictionary
25020 When a command is executed from @value{GDBN} that is compatible with
25021 frame filters, @value{GDBN} combines the @code{global},
25022 @code{gdb.Progspace} and all @code{gdb.Objfile} dictionaries currently
25023 loaded. All of the @code{gdb.Objfile} dictionaries are combined, as
25024 several frames, and thus several object files, might be in use.
25025 @value{GDBN} then prunes any frame filter whose @code{enabled}
25026 attribute is @code{False}. This pruned list is then sorted according
25027 to the @code{priority} attribute in each filter.
25029 Once the dictionaries are combined, pruned and sorted, @value{GDBN}
25030 creates an iterator which wraps each frame in the call stack in a
25031 @code{FrameDecorator} object, and calls each filter in order. The
25032 output from the previous filter will always be the input to the next
25035 Frame filters have a mandatory interface which each frame filter must
25036 implement, defined here:
25038 @defun FrameFilter.filter (iterator)
25039 @value{GDBN} will call this method on a frame filter when it has
25040 reached the order in the priority list for that filter.
25042 For example, if there are four frame filters:
25053 The order that the frame filters will be called is:
25056 Filter3 -> Filter2 -> Filter1 -> Filter4
25059 Note that the output from @code{Filter3} is passed to the input of
25060 @code{Filter2}, and so on.
25062 This @code{filter} method is passed a Python iterator. This iterator
25063 contains a sequence of frame decorators that wrap each
25064 @code{gdb.Frame}, or a frame decorator that wraps another frame
25065 decorator. The first filter that is executed in the sequence of frame
25066 filters will receive an iterator entirely comprised of default
25067 @code{FrameDecorator} objects. However, after each frame filter is
25068 executed, the previous frame filter may have wrapped some or all of
25069 the frame decorators with their own frame decorator. As frame
25070 decorators must also conform to a mandatory interface, these
25071 decorators can be assumed to act in a uniform manner (@pxref{Frame
25074 This method must return an object conforming to the Python iterator
25075 protocol. Each item in the iterator must be an object conforming to
25076 the frame decorator interface. If a frame filter does not wish to
25077 perform any operations on this iterator, it should return that
25078 iterator untouched.
25080 This method is not optional. If it does not exist, @value{GDBN} will
25081 raise and print an error.
25084 @defvar FrameFilter.name
25085 The @code{name} attribute must be Python string which contains the
25086 name of the filter displayed by @value{GDBN} (@pxref{Frame Filter
25087 Management}). This attribute may contain any combination of letters
25088 or numbers. Care should be taken to ensure that it is unique. This
25089 attribute is mandatory.
25092 @defvar FrameFilter.enabled
25093 The @code{enabled} attribute must be Python boolean. This attribute
25094 indicates to @value{GDBN} whether the frame filter is enabled, and
25095 should be considered when frame filters are executed. If
25096 @code{enabled} is @code{True}, then the frame filter will be executed
25097 when any of the backtrace commands detailed earlier in this chapter
25098 are executed. If @code{enabled} is @code{False}, then the frame
25099 filter will not be executed. This attribute is mandatory.
25102 @defvar FrameFilter.priority
25103 The @code{priority} attribute must be Python integer. This attribute
25104 controls the order of execution in relation to other frame filters.
25105 There are no imposed limits on the range of @code{priority} other than
25106 it must be a valid integer. The higher the @code{priority} attribute,
25107 the sooner the frame filter will be executed in relation to other
25108 frame filters. Although @code{priority} can be negative, it is
25109 recommended practice to assume zero is the lowest priority that a
25110 frame filter can be assigned. Frame filters that have the same
25111 priority are executed in unsorted order in that priority slot. This
25112 attribute is mandatory.
25115 @node Frame Decorator API
25116 @subsubsection Decorating Frames.
25117 @cindex frame decorator api
25119 Frame decorators are sister objects to frame filters (@pxref{Frame
25120 Filter API}). Frame decorators are applied by a frame filter and can
25121 only be used in conjunction with frame filters.
25123 The purpose of a frame decorator is to customize the printed content
25124 of each @code{gdb.Frame} in commands where frame filters are executed.
25125 This concept is called decorating a frame. Frame decorators decorate
25126 a @code{gdb.Frame} with Python code contained within each API call.
25127 This separates the actual data contained in a @code{gdb.Frame} from
25128 the decorated data produced by a frame decorator. This abstraction is
25129 necessary to maintain integrity of the data contained in each
25132 Frame decorators have a mandatory interface, defined below.
25134 @value{GDBN} already contains a frame decorator called
25135 @code{FrameDecorator}. This contains substantial amounts of
25136 boilerplate code to decorate the content of a @code{gdb.Frame}. It is
25137 recommended that other frame decorators inherit and extend this
25138 object, and only to override the methods needed.
25140 @defun FrameDecorator.elided (self)
25142 The @code{elided} method groups frames together in a hierarchical
25143 system. An example would be an interpreter, where multiple low-level
25144 frames make up a single call in the interpreted language. In this
25145 example, the frame filter would elide the low-level frames and present
25146 a single high-level frame, representing the call in the interpreted
25147 language, to the user.
25149 The @code{elided} function must return an iterable and this iterable
25150 must contain the frames that are being elided wrapped in a suitable
25151 frame decorator. If no frames are being elided this function may
25152 return an empty iterable, or @code{None}. Elided frames are indented
25153 from normal frames in a @code{CLI} backtrace, or in the case of
25154 @code{GDB/MI}, are placed in the @code{children} field of the eliding
25157 It is the frame filter's task to also filter out the elided frames from
25158 the source iterator. This will avoid printing the frame twice.
25161 @defun FrameDecorator.function (self)
25163 This method returns the name of the function in the frame that is to
25166 This method must return a Python string describing the function, or
25169 If this function returns @code{None}, @value{GDBN} will not print any
25170 data for this field.
25173 @defun FrameDecorator.address (self)
25175 This method returns the address of the frame that is to be printed.
25177 This method must return a Python numeric integer type of sufficient
25178 size to describe the address of the frame, or @code{None}.
25180 If this function returns a @code{None}, @value{GDBN} will not print
25181 any data for this field.
25184 @defun FrameDecorator.filename (self)
25186 This method returns the filename and path associated with this frame.
25188 This method must return a Python string containing the filename and
25189 the path to the object file backing the frame, or @code{None}.
25191 If this function returns a @code{None}, @value{GDBN} will not print
25192 any data for this field.
25195 @defun FrameDecorator.line (self):
25197 This method returns the line number associated with the current
25198 position within the function addressed by this frame.
25200 This method must return a Python integer type, or @code{None}.
25202 If this function returns a @code{None}, @value{GDBN} will not print
25203 any data for this field.
25206 @defun FrameDecorator.frame_args (self)
25207 @anchor{frame_args}
25209 This method must return an iterable, or @code{None}. Returning an
25210 empty iterable, or @code{None} means frame arguments will not be
25211 printed for this frame. This iterable must contain objects that
25212 implement two methods, described here.
25214 This object must implement a @code{argument} method which takes a
25215 single @code{self} parameter and must return a @code{gdb.Symbol}
25216 (@pxref{Symbols In Python}), or a Python string. The object must also
25217 implement a @code{value} method which takes a single @code{self}
25218 parameter and must return a @code{gdb.Value} (@pxref{Values From
25219 Inferior}), a Python value, or @code{None}. If the @code{value}
25220 method returns @code{None}, and the @code{argument} method returns a
25221 @code{gdb.Symbol}, @value{GDBN} will look-up and print the value of
25222 the @code{gdb.Symbol} automatically.
25227 class SymValueWrapper():
25229 def __init__(self, symbol, value):
25239 class SomeFrameDecorator()
25242 def frame_args(self):
25245 block = self.inferior_frame.block()
25249 # Iterate over all symbols in a block. Only add
25250 # symbols that are arguments.
25252 if not sym.is_argument:
25254 args.append(SymValueWrapper(sym,None))
25256 # Add example synthetic argument.
25257 args.append(SymValueWrapper(``foo'', 42))
25263 @defun FrameDecorator.frame_locals (self)
25265 This method must return an iterable or @code{None}. Returning an
25266 empty iterable, or @code{None} means frame local arguments will not be
25267 printed for this frame.
25269 The object interface, the description of the various strategies for
25270 reading frame locals, and the example are largely similar to those
25271 described in the @code{frame_args} function, (@pxref{frame_args,,The
25272 frame filter frame_args function}). Below is a modified example:
25275 class SomeFrameDecorator()
25278 def frame_locals(self):
25281 block = self.inferior_frame.block()
25285 # Iterate over all symbols in a block. Add all
25286 # symbols, except arguments.
25288 if sym.is_argument:
25290 vars.append(SymValueWrapper(sym,None))
25292 # Add an example of a synthetic local variable.
25293 vars.append(SymValueWrapper(``bar'', 99))
25299 @defun FrameDecorator.inferior_frame (self):
25301 This method must return the underlying @code{gdb.Frame} that this
25302 frame decorator is decorating. @value{GDBN} requires the underlying
25303 frame for internal frame information to determine how to print certain
25304 values when printing a frame.
25307 @node Writing a Frame Filter
25308 @subsubsection Writing a Frame Filter
25309 @cindex writing a frame filter
25311 There are three basic elements that a frame filter must implement: it
25312 must correctly implement the documented interface (@pxref{Frame Filter
25313 API}), it must register itself with @value{GDBN}, and finally, it must
25314 decide if it is to work on the data provided by @value{GDBN}. In all
25315 cases, whether it works on the iterator or not, each frame filter must
25316 return an iterator. A bare-bones frame filter follows the pattern in
25317 the following example.
25322 class FrameFilter():
25324 def __init__(self):
25325 # Frame filter attribute creation.
25327 # 'name' is the name of the filter that GDB will display.
25329 # 'priority' is the priority of the filter relative to other
25332 # 'enabled' is a boolean that indicates whether this filter is
25333 # enabled and should be executed.
25336 self.priority = 100
25337 self.enabled = True
25339 # Register this frame filter with the global frame_filters
25341 gdb.frame_filters[self.name] = self
25343 def filter(self, frame_iter):
25344 # Just return the iterator.
25348 The frame filter in the example above implements the three
25349 requirements for all frame filters. It implements the API, self
25350 registers, and makes a decision on the iterator (in this case, it just
25351 returns the iterator untouched).
25353 The first step is attribute creation and assignment, and as shown in
25354 the comments the filter assigns the following attributes: @code{name},
25355 @code{priority} and whether the filter should be enabled with the
25356 @code{enabled} attribute.
25358 The second step is registering the frame filter with the dictionary or
25359 dictionaries that the frame filter has interest in. As shown in the
25360 comments, this filter just registers itself with the global dictionary
25361 @code{gdb.frame_filters}. As noted earlier, @code{gdb.frame_filters}
25362 is a dictionary that is initialized in the @code{gdb} module when
25363 @value{GDBN} starts. What dictionary a filter registers with is an
25364 important consideration. Generally, if a filter is specific to a set
25365 of code, it should be registered either in the @code{objfile} or
25366 @code{progspace} dictionaries as they are specific to the program
25367 currently loaded in @value{GDBN}. The global dictionary is always
25368 present in @value{GDBN} and is never unloaded. Any filters registered
25369 with the global dictionary will exist until @value{GDBN} exits. To
25370 avoid filters that may conflict, it is generally better to register
25371 frame filters against the dictionaries that more closely align with
25372 the usage of the filter currently in question. @xref{Python
25373 Auto-loading}, for further information on auto-loading Python scripts.
25375 @value{GDBN} takes a hands-off approach to frame filter registration,
25376 therefore it is the frame filter's responsibility to ensure
25377 registration has occurred, and that any exceptions are handled
25378 appropriately. In particular, you may wish to handle exceptions
25379 relating to Python dictionary key uniqueness. It is mandatory that
25380 the dictionary key is the same as frame filter's @code{name}
25381 attribute. When a user manages frame filters (@pxref{Frame Filter
25382 Management}), the names @value{GDBN} will display are those contained
25383 in the @code{name} attribute.
25385 The final step of this example is the implementation of the
25386 @code{filter} method. As shown in the example comments, we define the
25387 @code{filter} method and note that the method must take an iterator,
25388 and also must return an iterator. In this bare-bones example, the
25389 frame filter is not very useful as it just returns the iterator
25390 untouched. However this is a valid operation for frame filters that
25391 have the @code{enabled} attribute set, but decide not to operate on
25394 In the next example, the frame filter operates on all frames and
25395 utilizes a frame decorator to perform some work on the frames.
25396 @xref{Frame Decorator API}, for further information on the frame
25397 decorator interface.
25399 This example works on inlined frames. It highlights frames which are
25400 inlined by tagging them with an ``[inlined]'' tag. By applying a
25401 frame decorator to all frames with the Python @code{itertools imap}
25402 method, the example defers actions to the frame decorator. Frame
25403 decorators are only processed when @value{GDBN} prints the backtrace.
25405 This introduces a new decision making topic: whether to perform
25406 decision making operations at the filtering step, or at the printing
25407 step. In this example's approach, it does not perform any filtering
25408 decisions at the filtering step beyond mapping a frame decorator to
25409 each frame. This allows the actual decision making to be performed
25410 when each frame is printed. This is an important consideration, and
25411 well worth reflecting upon when designing a frame filter. An issue
25412 that frame filters should avoid is unwinding the stack if possible.
25413 Some stacks can run very deep, into the tens of thousands in some
25414 cases. To search every frame to determine if it is inlined ahead of
25415 time may be too expensive at the filtering step. The frame filter
25416 cannot know how many frames it has to iterate over, and it would have
25417 to iterate through them all. This ends up duplicating effort as
25418 @value{GDBN} performs this iteration when it prints the frames.
25420 In this example decision making can be deferred to the printing step.
25421 As each frame is printed, the frame decorator can examine each frame
25422 in turn when @value{GDBN} iterates. From a performance viewpoint,
25423 this is the most appropriate decision to make as it avoids duplicating
25424 the effort that the printing step would undertake anyway. Also, if
25425 there are many frame filters unwinding the stack during filtering, it
25426 can substantially delay the printing of the backtrace which will
25427 result in large memory usage, and a poor user experience.
25430 class InlineFilter():
25432 def __init__(self):
25433 self.name = "InlinedFrameFilter"
25434 self.priority = 100
25435 self.enabled = True
25436 gdb.frame_filters[self.name] = self
25438 def filter(self, frame_iter):
25439 frame_iter = itertools.imap(InlinedFrameDecorator,
25444 This frame filter is somewhat similar to the earlier example, except
25445 that the @code{filter} method applies a frame decorator object called
25446 @code{InlinedFrameDecorator} to each element in the iterator. The
25447 @code{imap} Python method is light-weight. It does not proactively
25448 iterate over the iterator, but rather creates a new iterator which
25449 wraps the existing one.
25451 Below is the frame decorator for this example.
25454 class InlinedFrameDecorator(FrameDecorator):
25456 def __init__(self, fobj):
25457 super(InlinedFrameDecorator, self).__init__(fobj)
25459 def function(self):
25460 frame = fobj.inferior_frame()
25461 name = str(frame.name())
25463 if frame.type() == gdb.INLINE_FRAME:
25464 name = name + " [inlined]"
25469 This frame decorator only defines and overrides the @code{function}
25470 method. It lets the supplied @code{FrameDecorator}, which is shipped
25471 with @value{GDBN}, perform the other work associated with printing
25474 The combination of these two objects create this output from a
25478 #0 0x004004e0 in bar () at inline.c:11
25479 #1 0x00400566 in max [inlined] (b=6, a=12) at inline.c:21
25480 #2 0x00400566 in main () at inline.c:31
25483 So in the case of this example, a frame decorator is applied to all
25484 frames, regardless of whether they may be inlined or not. As
25485 @value{GDBN} iterates over the iterator produced by the frame filters,
25486 @value{GDBN} executes each frame decorator which then makes a decision
25487 on what to print in the @code{function} callback. Using a strategy
25488 like this is a way to defer decisions on the frame content to printing
25491 @subheading Eliding Frames
25493 It might be that the above example is not desirable for representing
25494 inlined frames, and a hierarchical approach may be preferred. If we
25495 want to hierarchically represent frames, the @code{elided} frame
25496 decorator interface might be preferable.
25498 This example approaches the issue with the @code{elided} method. This
25499 example is quite long, but very simplistic. It is out-of-scope for
25500 this section to write a complete example that comprehensively covers
25501 all approaches of finding and printing inlined frames. However, this
25502 example illustrates the approach an author might use.
25504 This example comprises of three sections.
25507 class InlineFrameFilter():
25509 def __init__(self):
25510 self.name = "InlinedFrameFilter"
25511 self.priority = 100
25512 self.enabled = True
25513 gdb.frame_filters[self.name] = self
25515 def filter(self, frame_iter):
25516 return ElidingInlineIterator(frame_iter)
25519 This frame filter is very similar to the other examples. The only
25520 difference is this frame filter is wrapping the iterator provided to
25521 it (@code{frame_iter}) with a custom iterator called
25522 @code{ElidingInlineIterator}. This again defers actions to when
25523 @value{GDBN} prints the backtrace, as the iterator is not traversed
25526 The iterator for this example is as follows. It is in this section of
25527 the example where decisions are made on the content of the backtrace.
25530 class ElidingInlineIterator:
25531 def __init__(self, ii):
25532 self.input_iterator = ii
25534 def __iter__(self):
25538 frame = next(self.input_iterator)
25540 if frame.inferior_frame().type() != gdb.INLINE_FRAME:
25544 eliding_frame = next(self.input_iterator)
25545 except StopIteration:
25547 return ElidingFrameDecorator(eliding_frame, [frame])
25550 This iterator implements the Python iterator protocol. When the
25551 @code{next} function is called (when @value{GDBN} prints each frame),
25552 the iterator checks if this frame decorator, @code{frame}, is wrapping
25553 an inlined frame. If it is not, it returns the existing frame decorator
25554 untouched. If it is wrapping an inlined frame, it assumes that the
25555 inlined frame was contained within the next oldest frame,
25556 @code{eliding_frame}, which it fetches. It then creates and returns a
25557 frame decorator, @code{ElidingFrameDecorator}, which contains both the
25558 elided frame, and the eliding frame.
25561 class ElidingInlineDecorator(FrameDecorator):
25563 def __init__(self, frame, elided_frames):
25564 super(ElidingInlineDecorator, self).__init__(frame)
25566 self.elided_frames = elided_frames
25569 return iter(self.elided_frames)
25572 This frame decorator overrides one function and returns the inlined
25573 frame in the @code{elided} method. As before it lets
25574 @code{FrameDecorator} do the rest of the work involved in printing
25575 this frame. This produces the following output.
25578 #0 0x004004e0 in bar () at inline.c:11
25579 #2 0x00400529 in main () at inline.c:25
25580 #1 0x00400529 in max (b=6, a=12) at inline.c:15
25583 In that output, @code{max} which has been inlined into @code{main} is
25584 printed hierarchically. Another approach would be to combine the
25585 @code{function} method, and the @code{elided} method to both print a
25586 marker in the inlined frame, and also show the hierarchical
25589 @node Inferiors In Python
25590 @subsubsection Inferiors In Python
25591 @cindex inferiors in Python
25593 @findex gdb.Inferior
25594 Programs which are being run under @value{GDBN} are called inferiors
25595 (@pxref{Inferiors and Programs}). Python scripts can access
25596 information about and manipulate inferiors controlled by @value{GDBN}
25597 via objects of the @code{gdb.Inferior} class.
25599 The following inferior-related functions are available in the @code{gdb}
25602 @defun gdb.inferiors ()
25603 Return a tuple containing all inferior objects.
25606 @defun gdb.selected_inferior ()
25607 Return an object representing the current inferior.
25610 A @code{gdb.Inferior} object has the following attributes:
25612 @defvar Inferior.num
25613 ID of inferior, as assigned by GDB.
25616 @defvar Inferior.pid
25617 Process ID of the inferior, as assigned by the underlying operating
25621 @defvar Inferior.was_attached
25622 Boolean signaling whether the inferior was created using `attach', or
25623 started by @value{GDBN} itself.
25626 A @code{gdb.Inferior} object has the following methods:
25628 @defun Inferior.is_valid ()
25629 Returns @code{True} if the @code{gdb.Inferior} object is valid,
25630 @code{False} if not. A @code{gdb.Inferior} object will become invalid
25631 if the inferior no longer exists within @value{GDBN}. All other
25632 @code{gdb.Inferior} methods will throw an exception if it is invalid
25633 at the time the method is called.
25636 @defun Inferior.threads ()
25637 This method returns a tuple holding all the threads which are valid
25638 when it is called. If there are no valid threads, the method will
25639 return an empty tuple.
25642 @findex Inferior.read_memory
25643 @defun Inferior.read_memory (address, length)
25644 Read @var{length} bytes of memory from the inferior, starting at
25645 @var{address}. Returns a buffer object, which behaves much like an array
25646 or a string. It can be modified and given to the
25647 @code{Inferior.write_memory} function. In @code{Python} 3, the return
25648 value is a @code{memoryview} object.
25651 @findex Inferior.write_memory
25652 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
25653 Write the contents of @var{buffer} to the inferior, starting at
25654 @var{address}. The @var{buffer} parameter must be a Python object
25655 which supports the buffer protocol, i.e., a string, an array or the
25656 object returned from @code{Inferior.read_memory}. If given, @var{length}
25657 determines the number of bytes from @var{buffer} to be written.
25660 @findex gdb.search_memory
25661 @defun Inferior.search_memory (address, length, pattern)
25662 Search a region of the inferior memory starting at @var{address} with
25663 the given @var{length} using the search pattern supplied in
25664 @var{pattern}. The @var{pattern} parameter must be a Python object
25665 which supports the buffer protocol, i.e., a string, an array or the
25666 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
25667 containing the address where the pattern was found, or @code{None} if
25668 the pattern could not be found.
25671 @node Events In Python
25672 @subsubsection Events In Python
25673 @cindex inferior events in Python
25675 @value{GDBN} provides a general event facility so that Python code can be
25676 notified of various state changes, particularly changes that occur in
25679 An @dfn{event} is just an object that describes some state change. The
25680 type of the object and its attributes will vary depending on the details
25681 of the change. All the existing events are described below.
25683 In order to be notified of an event, you must register an event handler
25684 with an @dfn{event registry}. An event registry is an object in the
25685 @code{gdb.events} module which dispatches particular events. A registry
25686 provides methods to register and unregister event handlers:
25688 @defun EventRegistry.connect (object)
25689 Add the given callable @var{object} to the registry. This object will be
25690 called when an event corresponding to this registry occurs.
25693 @defun EventRegistry.disconnect (object)
25694 Remove the given @var{object} from the registry. Once removed, the object
25695 will no longer receive notifications of events.
25698 Here is an example:
25701 def exit_handler (event):
25702 print "event type: exit"
25703 print "exit code: %d" % (event.exit_code)
25705 gdb.events.exited.connect (exit_handler)
25708 In the above example we connect our handler @code{exit_handler} to the
25709 registry @code{events.exited}. Once connected, @code{exit_handler} gets
25710 called when the inferior exits. The argument @dfn{event} in this example is
25711 of type @code{gdb.ExitedEvent}. As you can see in the example the
25712 @code{ExitedEvent} object has an attribute which indicates the exit code of
25715 The following is a listing of the event registries that are available and
25716 details of the events they emit:
25721 Emits @code{gdb.ThreadEvent}.
25723 Some events can be thread specific when @value{GDBN} is running in non-stop
25724 mode. When represented in Python, these events all extend
25725 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
25726 events which are emitted by this or other modules might extend this event.
25727 Examples of these events are @code{gdb.BreakpointEvent} and
25728 @code{gdb.ContinueEvent}.
25730 @defvar ThreadEvent.inferior_thread
25731 In non-stop mode this attribute will be set to the specific thread which was
25732 involved in the emitted event. Otherwise, it will be set to @code{None}.
25735 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
25737 This event indicates that the inferior has been continued after a stop. For
25738 inherited attribute refer to @code{gdb.ThreadEvent} above.
25740 @item events.exited
25741 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
25742 @code{events.ExitedEvent} has two attributes:
25743 @defvar ExitedEvent.exit_code
25744 An integer representing the exit code, if available, which the inferior
25745 has returned. (The exit code could be unavailable if, for example,
25746 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
25747 the attribute does not exist.
25749 @defvar ExitedEvent inferior
25750 A reference to the inferior which triggered the @code{exited} event.
25754 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
25756 Indicates that the inferior has stopped. All events emitted by this registry
25757 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
25758 will indicate the stopped thread when @value{GDBN} is running in non-stop
25759 mode. Refer to @code{gdb.ThreadEvent} above for more details.
25761 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
25763 This event indicates that the inferior or one of its threads has received as
25764 signal. @code{gdb.SignalEvent} has the following attributes:
25766 @defvar SignalEvent.stop_signal
25767 A string representing the signal received by the inferior. A list of possible
25768 signal values can be obtained by running the command @code{info signals} in
25769 the @value{GDBN} command prompt.
25772 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
25774 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
25775 been hit, and has the following attributes:
25777 @defvar BreakpointEvent.breakpoints
25778 A sequence containing references to all the breakpoints (type
25779 @code{gdb.Breakpoint}) that were hit.
25780 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
25782 @defvar BreakpointEvent.breakpoint
25783 A reference to the first breakpoint that was hit.
25784 This function is maintained for backward compatibility and is now deprecated
25785 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
25788 @item events.new_objfile
25789 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
25790 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
25792 @defvar NewObjFileEvent.new_objfile
25793 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
25794 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
25799 @node Threads In Python
25800 @subsubsection Threads In Python
25801 @cindex threads in python
25803 @findex gdb.InferiorThread
25804 Python scripts can access information about, and manipulate inferior threads
25805 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
25807 The following thread-related functions are available in the @code{gdb}
25810 @findex gdb.selected_thread
25811 @defun gdb.selected_thread ()
25812 This function returns the thread object for the selected thread. If there
25813 is no selected thread, this will return @code{None}.
25816 A @code{gdb.InferiorThread} object has the following attributes:
25818 @defvar InferiorThread.name
25819 The name of the thread. If the user specified a name using
25820 @code{thread name}, then this returns that name. Otherwise, if an
25821 OS-supplied name is available, then it is returned. Otherwise, this
25822 returns @code{None}.
25824 This attribute can be assigned to. The new value must be a string
25825 object, which sets the new name, or @code{None}, which removes any
25826 user-specified thread name.
25829 @defvar InferiorThread.num
25830 ID of the thread, as assigned by GDB.
25833 @defvar InferiorThread.ptid
25834 ID of the thread, as assigned by the operating system. This attribute is a
25835 tuple containing three integers. The first is the Process ID (PID); the second
25836 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
25837 Either the LWPID or TID may be 0, which indicates that the operating system
25838 does not use that identifier.
25841 A @code{gdb.InferiorThread} object has the following methods:
25843 @defun InferiorThread.is_valid ()
25844 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
25845 @code{False} if not. A @code{gdb.InferiorThread} object will become
25846 invalid if the thread exits, or the inferior that the thread belongs
25847 is deleted. All other @code{gdb.InferiorThread} methods will throw an
25848 exception if it is invalid at the time the method is called.
25851 @defun InferiorThread.switch ()
25852 This changes @value{GDBN}'s currently selected thread to the one represented
25856 @defun InferiorThread.is_stopped ()
25857 Return a Boolean indicating whether the thread is stopped.
25860 @defun InferiorThread.is_running ()
25861 Return a Boolean indicating whether the thread is running.
25864 @defun InferiorThread.is_exited ()
25865 Return a Boolean indicating whether the thread is exited.
25868 @node Commands In Python
25869 @subsubsection Commands In Python
25871 @cindex commands in python
25872 @cindex python commands
25873 You can implement new @value{GDBN} CLI commands in Python. A CLI
25874 command is implemented using an instance of the @code{gdb.Command}
25875 class, most commonly using a subclass.
25877 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
25878 The object initializer for @code{Command} registers the new command
25879 with @value{GDBN}. This initializer is normally invoked from the
25880 subclass' own @code{__init__} method.
25882 @var{name} is the name of the command. If @var{name} consists of
25883 multiple words, then the initial words are looked for as prefix
25884 commands. In this case, if one of the prefix commands does not exist,
25885 an exception is raised.
25887 There is no support for multi-line commands.
25889 @var{command_class} should be one of the @samp{COMMAND_} constants
25890 defined below. This argument tells @value{GDBN} how to categorize the
25891 new command in the help system.
25893 @var{completer_class} is an optional argument. If given, it should be
25894 one of the @samp{COMPLETE_} constants defined below. This argument
25895 tells @value{GDBN} how to perform completion for this command. If not
25896 given, @value{GDBN} will attempt to complete using the object's
25897 @code{complete} method (see below); if no such method is found, an
25898 error will occur when completion is attempted.
25900 @var{prefix} is an optional argument. If @code{True}, then the new
25901 command is a prefix command; sub-commands of this command may be
25904 The help text for the new command is taken from the Python
25905 documentation string for the command's class, if there is one. If no
25906 documentation string is provided, the default value ``This command is
25907 not documented.'' is used.
25910 @cindex don't repeat Python command
25911 @defun Command.dont_repeat ()
25912 By default, a @value{GDBN} command is repeated when the user enters a
25913 blank line at the command prompt. A command can suppress this
25914 behavior by invoking the @code{dont_repeat} method. This is similar
25915 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
25918 @defun Command.invoke (argument, from_tty)
25919 This method is called by @value{GDBN} when this command is invoked.
25921 @var{argument} is a string. It is the argument to the command, after
25922 leading and trailing whitespace has been stripped.
25924 @var{from_tty} is a boolean argument. When true, this means that the
25925 command was entered by the user at the terminal; when false it means
25926 that the command came from elsewhere.
25928 If this method throws an exception, it is turned into a @value{GDBN}
25929 @code{error} call. Otherwise, the return value is ignored.
25931 @findex gdb.string_to_argv
25932 To break @var{argument} up into an argv-like string use
25933 @code{gdb.string_to_argv}. This function behaves identically to
25934 @value{GDBN}'s internal argument lexer @code{buildargv}.
25935 It is recommended to use this for consistency.
25936 Arguments are separated by spaces and may be quoted.
25940 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
25941 ['1', '2 "3', '4 "5', "6 '7"]
25946 @cindex completion of Python commands
25947 @defun Command.complete (text, word)
25948 This method is called by @value{GDBN} when the user attempts
25949 completion on this command. All forms of completion are handled by
25950 this method, that is, the @key{TAB} and @key{M-?} key bindings
25951 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
25954 The arguments @var{text} and @var{word} are both strings. @var{text}
25955 holds the complete command line up to the cursor's location.
25956 @var{word} holds the last word of the command line; this is computed
25957 using a word-breaking heuristic.
25959 The @code{complete} method can return several values:
25962 If the return value is a sequence, the contents of the sequence are
25963 used as the completions. It is up to @code{complete} to ensure that the
25964 contents actually do complete the word. A zero-length sequence is
25965 allowed, it means that there were no completions available. Only
25966 string elements of the sequence are used; other elements in the
25967 sequence are ignored.
25970 If the return value is one of the @samp{COMPLETE_} constants defined
25971 below, then the corresponding @value{GDBN}-internal completion
25972 function is invoked, and its result is used.
25975 All other results are treated as though there were no available
25980 When a new command is registered, it must be declared as a member of
25981 some general class of commands. This is used to classify top-level
25982 commands in the on-line help system; note that prefix commands are not
25983 listed under their own category but rather that of their top-level
25984 command. The available classifications are represented by constants
25985 defined in the @code{gdb} module:
25988 @findex COMMAND_NONE
25989 @findex gdb.COMMAND_NONE
25990 @item gdb.COMMAND_NONE
25991 The command does not belong to any particular class. A command in
25992 this category will not be displayed in any of the help categories.
25994 @findex COMMAND_RUNNING
25995 @findex gdb.COMMAND_RUNNING
25996 @item gdb.COMMAND_RUNNING
25997 The command is related to running the inferior. For example,
25998 @code{start}, @code{step}, and @code{continue} are in this category.
25999 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
26000 commands in this category.
26002 @findex COMMAND_DATA
26003 @findex gdb.COMMAND_DATA
26004 @item gdb.COMMAND_DATA
26005 The command is related to data or variables. For example,
26006 @code{call}, @code{find}, and @code{print} are in this category. Type
26007 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
26010 @findex COMMAND_STACK
26011 @findex gdb.COMMAND_STACK
26012 @item gdb.COMMAND_STACK
26013 The command has to do with manipulation of the stack. For example,
26014 @code{backtrace}, @code{frame}, and @code{return} are in this
26015 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
26016 list of commands in this category.
26018 @findex COMMAND_FILES
26019 @findex gdb.COMMAND_FILES
26020 @item gdb.COMMAND_FILES
26021 This class is used for file-related commands. For example,
26022 @code{file}, @code{list} and @code{section} are in this category.
26023 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
26024 commands in this category.
26026 @findex COMMAND_SUPPORT
26027 @findex gdb.COMMAND_SUPPORT
26028 @item gdb.COMMAND_SUPPORT
26029 This should be used for ``support facilities'', generally meaning
26030 things that are useful to the user when interacting with @value{GDBN},
26031 but not related to the state of the inferior. For example,
26032 @code{help}, @code{make}, and @code{shell} are in this category. Type
26033 @kbd{help support} at the @value{GDBN} prompt to see a list of
26034 commands in this category.
26036 @findex COMMAND_STATUS
26037 @findex gdb.COMMAND_STATUS
26038 @item gdb.COMMAND_STATUS
26039 The command is an @samp{info}-related command, that is, related to the
26040 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
26041 and @code{show} are in this category. Type @kbd{help status} at the
26042 @value{GDBN} prompt to see a list of commands in this category.
26044 @findex COMMAND_BREAKPOINTS
26045 @findex gdb.COMMAND_BREAKPOINTS
26046 @item gdb.COMMAND_BREAKPOINTS
26047 The command has to do with breakpoints. For example, @code{break},
26048 @code{clear}, and @code{delete} are in this category. Type @kbd{help
26049 breakpoints} at the @value{GDBN} prompt to see a list of commands in
26052 @findex COMMAND_TRACEPOINTS
26053 @findex gdb.COMMAND_TRACEPOINTS
26054 @item gdb.COMMAND_TRACEPOINTS
26055 The command has to do with tracepoints. For example, @code{trace},
26056 @code{actions}, and @code{tfind} are in this category. Type
26057 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
26058 commands in this category.
26060 @findex COMMAND_USER
26061 @findex gdb.COMMAND_USER
26062 @item gdb.COMMAND_USER
26063 The command is a general purpose command for the user, and typically
26064 does not fit in one of the other categories.
26065 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
26066 a list of commands in this category, as well as the list of gdb macros
26067 (@pxref{Sequences}).
26069 @findex COMMAND_OBSCURE
26070 @findex gdb.COMMAND_OBSCURE
26071 @item gdb.COMMAND_OBSCURE
26072 The command is only used in unusual circumstances, or is not of
26073 general interest to users. For example, @code{checkpoint},
26074 @code{fork}, and @code{stop} are in this category. Type @kbd{help
26075 obscure} at the @value{GDBN} prompt to see a list of commands in this
26078 @findex COMMAND_MAINTENANCE
26079 @findex gdb.COMMAND_MAINTENANCE
26080 @item gdb.COMMAND_MAINTENANCE
26081 The command is only useful to @value{GDBN} maintainers. The
26082 @code{maintenance} and @code{flushregs} commands are in this category.
26083 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
26084 commands in this category.
26087 A new command can use a predefined completion function, either by
26088 specifying it via an argument at initialization, or by returning it
26089 from the @code{complete} method. These predefined completion
26090 constants are all defined in the @code{gdb} module:
26093 @findex COMPLETE_NONE
26094 @findex gdb.COMPLETE_NONE
26095 @item gdb.COMPLETE_NONE
26096 This constant means that no completion should be done.
26098 @findex COMPLETE_FILENAME
26099 @findex gdb.COMPLETE_FILENAME
26100 @item gdb.COMPLETE_FILENAME
26101 This constant means that filename completion should be performed.
26103 @findex COMPLETE_LOCATION
26104 @findex gdb.COMPLETE_LOCATION
26105 @item gdb.COMPLETE_LOCATION
26106 This constant means that location completion should be done.
26107 @xref{Specify Location}.
26109 @findex COMPLETE_COMMAND
26110 @findex gdb.COMPLETE_COMMAND
26111 @item gdb.COMPLETE_COMMAND
26112 This constant means that completion should examine @value{GDBN}
26115 @findex COMPLETE_SYMBOL
26116 @findex gdb.COMPLETE_SYMBOL
26117 @item gdb.COMPLETE_SYMBOL
26118 This constant means that completion should be done using symbol names
26121 @findex COMPLETE_EXPRESSION
26122 @findex gdb.COMPLETE_EXPRESSION
26123 @item gdb.COMPLETE_EXPRESSION
26124 This constant means that completion should be done on expressions.
26125 Often this means completing on symbol names, but some language
26126 parsers also have support for completing on field names.
26129 The following code snippet shows how a trivial CLI command can be
26130 implemented in Python:
26133 class HelloWorld (gdb.Command):
26134 """Greet the whole world."""
26136 def __init__ (self):
26137 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
26139 def invoke (self, arg, from_tty):
26140 print "Hello, World!"
26145 The last line instantiates the class, and is necessary to trigger the
26146 registration of the command with @value{GDBN}. Depending on how the
26147 Python code is read into @value{GDBN}, you may need to import the
26148 @code{gdb} module explicitly.
26150 @node Parameters In Python
26151 @subsubsection Parameters In Python
26153 @cindex parameters in python
26154 @cindex python parameters
26155 @tindex gdb.Parameter
26157 You can implement new @value{GDBN} parameters using Python. A new
26158 parameter is implemented as an instance of the @code{gdb.Parameter}
26161 Parameters are exposed to the user via the @code{set} and
26162 @code{show} commands. @xref{Help}.
26164 There are many parameters that already exist and can be set in
26165 @value{GDBN}. Two examples are: @code{set follow fork} and
26166 @code{set charset}. Setting these parameters influences certain
26167 behavior in @value{GDBN}. Similarly, you can define parameters that
26168 can be used to influence behavior in custom Python scripts and commands.
26170 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
26171 The object initializer for @code{Parameter} registers the new
26172 parameter with @value{GDBN}. This initializer is normally invoked
26173 from the subclass' own @code{__init__} method.
26175 @var{name} is the name of the new parameter. If @var{name} consists
26176 of multiple words, then the initial words are looked for as prefix
26177 parameters. An example of this can be illustrated with the
26178 @code{set print} set of parameters. If @var{name} is
26179 @code{print foo}, then @code{print} will be searched as the prefix
26180 parameter. In this case the parameter can subsequently be accessed in
26181 @value{GDBN} as @code{set print foo}.
26183 If @var{name} consists of multiple words, and no prefix parameter group
26184 can be found, an exception is raised.
26186 @var{command-class} should be one of the @samp{COMMAND_} constants
26187 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
26188 categorize the new parameter in the help system.
26190 @var{parameter-class} should be one of the @samp{PARAM_} constants
26191 defined below. This argument tells @value{GDBN} the type of the new
26192 parameter; this information is used for input validation and
26195 If @var{parameter-class} is @code{PARAM_ENUM}, then
26196 @var{enum-sequence} must be a sequence of strings. These strings
26197 represent the possible values for the parameter.
26199 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
26200 of a fourth argument will cause an exception to be thrown.
26202 The help text for the new parameter is taken from the Python
26203 documentation string for the parameter's class, if there is one. If
26204 there is no documentation string, a default value is used.
26207 @defvar Parameter.set_doc
26208 If this attribute exists, and is a string, then its value is used as
26209 the help text for this parameter's @code{set} command. The value is
26210 examined when @code{Parameter.__init__} is invoked; subsequent changes
26214 @defvar Parameter.show_doc
26215 If this attribute exists, and is a string, then its value is used as
26216 the help text for this parameter's @code{show} command. The value is
26217 examined when @code{Parameter.__init__} is invoked; subsequent changes
26221 @defvar Parameter.value
26222 The @code{value} attribute holds the underlying value of the
26223 parameter. It can be read and assigned to just as any other
26224 attribute. @value{GDBN} does validation when assignments are made.
26227 There are two methods that should be implemented in any
26228 @code{Parameter} class. These are:
26230 @defun Parameter.get_set_string (self)
26231 @value{GDBN} will call this method when a @var{parameter}'s value has
26232 been changed via the @code{set} API (for example, @kbd{set foo off}).
26233 The @code{value} attribute has already been populated with the new
26234 value and may be used in output. This method must return a string.
26237 @defun Parameter.get_show_string (self, svalue)
26238 @value{GDBN} will call this method when a @var{parameter}'s
26239 @code{show} API has been invoked (for example, @kbd{show foo}). The
26240 argument @code{svalue} receives the string representation of the
26241 current value. This method must return a string.
26244 When a new parameter is defined, its type must be specified. The
26245 available types are represented by constants defined in the @code{gdb}
26249 @findex PARAM_BOOLEAN
26250 @findex gdb.PARAM_BOOLEAN
26251 @item gdb.PARAM_BOOLEAN
26252 The value is a plain boolean. The Python boolean values, @code{True}
26253 and @code{False} are the only valid values.
26255 @findex PARAM_AUTO_BOOLEAN
26256 @findex gdb.PARAM_AUTO_BOOLEAN
26257 @item gdb.PARAM_AUTO_BOOLEAN
26258 The value has three possible states: true, false, and @samp{auto}. In
26259 Python, true and false are represented using boolean constants, and
26260 @samp{auto} is represented using @code{None}.
26262 @findex PARAM_UINTEGER
26263 @findex gdb.PARAM_UINTEGER
26264 @item gdb.PARAM_UINTEGER
26265 The value is an unsigned integer. The value of 0 should be
26266 interpreted to mean ``unlimited''.
26268 @findex PARAM_INTEGER
26269 @findex gdb.PARAM_INTEGER
26270 @item gdb.PARAM_INTEGER
26271 The value is a signed integer. The value of 0 should be interpreted
26272 to mean ``unlimited''.
26274 @findex PARAM_STRING
26275 @findex gdb.PARAM_STRING
26276 @item gdb.PARAM_STRING
26277 The value is a string. When the user modifies the string, any escape
26278 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
26279 translated into corresponding characters and encoded into the current
26282 @findex PARAM_STRING_NOESCAPE
26283 @findex gdb.PARAM_STRING_NOESCAPE
26284 @item gdb.PARAM_STRING_NOESCAPE
26285 The value is a string. When the user modifies the string, escapes are
26286 passed through untranslated.
26288 @findex PARAM_OPTIONAL_FILENAME
26289 @findex gdb.PARAM_OPTIONAL_FILENAME
26290 @item gdb.PARAM_OPTIONAL_FILENAME
26291 The value is a either a filename (a string), or @code{None}.
26293 @findex PARAM_FILENAME
26294 @findex gdb.PARAM_FILENAME
26295 @item gdb.PARAM_FILENAME
26296 The value is a filename. This is just like
26297 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
26299 @findex PARAM_ZINTEGER
26300 @findex gdb.PARAM_ZINTEGER
26301 @item gdb.PARAM_ZINTEGER
26302 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
26303 is interpreted as itself.
26306 @findex gdb.PARAM_ENUM
26307 @item gdb.PARAM_ENUM
26308 The value is a string, which must be one of a collection string
26309 constants provided when the parameter is created.
26312 @node Functions In Python
26313 @subsubsection Writing new convenience functions
26315 @cindex writing convenience functions
26316 @cindex convenience functions in python
26317 @cindex python convenience functions
26318 @tindex gdb.Function
26320 You can implement new convenience functions (@pxref{Convenience Vars})
26321 in Python. A convenience function is an instance of a subclass of the
26322 class @code{gdb.Function}.
26324 @defun Function.__init__ (name)
26325 The initializer for @code{Function} registers the new function with
26326 @value{GDBN}. The argument @var{name} is the name of the function,
26327 a string. The function will be visible to the user as a convenience
26328 variable of type @code{internal function}, whose name is the same as
26329 the given @var{name}.
26331 The documentation for the new function is taken from the documentation
26332 string for the new class.
26335 @defun Function.invoke (@var{*args})
26336 When a convenience function is evaluated, its arguments are converted
26337 to instances of @code{gdb.Value}, and then the function's
26338 @code{invoke} method is called. Note that @value{GDBN} does not
26339 predetermine the arity of convenience functions. Instead, all
26340 available arguments are passed to @code{invoke}, following the
26341 standard Python calling convention. In particular, a convenience
26342 function can have default values for parameters without ill effect.
26344 The return value of this method is used as its value in the enclosing
26345 expression. If an ordinary Python value is returned, it is converted
26346 to a @code{gdb.Value} following the usual rules.
26349 The following code snippet shows how a trivial convenience function can
26350 be implemented in Python:
26353 class Greet (gdb.Function):
26354 """Return string to greet someone.
26355 Takes a name as argument."""
26357 def __init__ (self):
26358 super (Greet, self).__init__ ("greet")
26360 def invoke (self, name):
26361 return "Hello, %s!" % name.string ()
26366 The last line instantiates the class, and is necessary to trigger the
26367 registration of the function with @value{GDBN}. Depending on how the
26368 Python code is read into @value{GDBN}, you may need to import the
26369 @code{gdb} module explicitly.
26371 Now you can use the function in an expression:
26374 (gdb) print $greet("Bob")
26378 @node Progspaces In Python
26379 @subsubsection Program Spaces In Python
26381 @cindex progspaces in python
26382 @tindex gdb.Progspace
26384 A program space, or @dfn{progspace}, represents a symbolic view
26385 of an address space.
26386 It consists of all of the objfiles of the program.
26387 @xref{Objfiles In Python}.
26388 @xref{Inferiors and Programs, program spaces}, for more details
26389 about program spaces.
26391 The following progspace-related functions are available in the
26394 @findex gdb.current_progspace
26395 @defun gdb.current_progspace ()
26396 This function returns the program space of the currently selected inferior.
26397 @xref{Inferiors and Programs}.
26400 @findex gdb.progspaces
26401 @defun gdb.progspaces ()
26402 Return a sequence of all the progspaces currently known to @value{GDBN}.
26405 Each progspace is represented by an instance of the @code{gdb.Progspace}
26408 @defvar Progspace.filename
26409 The file name of the progspace as a string.
26412 @defvar Progspace.pretty_printers
26413 The @code{pretty_printers} attribute is a list of functions. It is
26414 used to look up pretty-printers. A @code{Value} is passed to each
26415 function in order; if the function returns @code{None}, then the
26416 search continues. Otherwise, the return value should be an object
26417 which is used to format the value. @xref{Pretty Printing API}, for more
26421 @defvar Progspace.type_printers
26422 The @code{type_printers} attribute is a list of type printer objects.
26423 @xref{Type Printing API}, for more information.
26426 @defvar Progspace.frame_filters
26427 The @code{frame_filters} attribute is a dictionary of frame filter
26428 objects. @xref{Frame Filter API}, for more information.
26431 @node Objfiles In Python
26432 @subsubsection Objfiles In Python
26434 @cindex objfiles in python
26435 @tindex gdb.Objfile
26437 @value{GDBN} loads symbols for an inferior from various
26438 symbol-containing files (@pxref{Files}). These include the primary
26439 executable file, any shared libraries used by the inferior, and any
26440 separate debug info files (@pxref{Separate Debug Files}).
26441 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
26443 The following objfile-related functions are available in the
26446 @findex gdb.current_objfile
26447 @defun gdb.current_objfile ()
26448 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
26449 sets the ``current objfile'' to the corresponding objfile. This
26450 function returns the current objfile. If there is no current objfile,
26451 this function returns @code{None}.
26454 @findex gdb.objfiles
26455 @defun gdb.objfiles ()
26456 Return a sequence of all the objfiles current known to @value{GDBN}.
26457 @xref{Objfiles In Python}.
26460 Each objfile is represented by an instance of the @code{gdb.Objfile}
26463 @defvar Objfile.filename
26464 The file name of the objfile as a string.
26467 @defvar Objfile.pretty_printers
26468 The @code{pretty_printers} attribute is a list of functions. It is
26469 used to look up pretty-printers. A @code{Value} is passed to each
26470 function in order; if the function returns @code{None}, then the
26471 search continues. Otherwise, the return value should be an object
26472 which is used to format the value. @xref{Pretty Printing API}, for more
26476 @defvar Objfile.type_printers
26477 The @code{type_printers} attribute is a list of type printer objects.
26478 @xref{Type Printing API}, for more information.
26481 @defvar Objfile.frame_filters
26482 The @code{frame_filters} attribute is a dictionary of frame filter
26483 objects. @xref{Frame Filter API}, for more information.
26486 A @code{gdb.Objfile} object has the following methods:
26488 @defun Objfile.is_valid ()
26489 Returns @code{True} if the @code{gdb.Objfile} object is valid,
26490 @code{False} if not. A @code{gdb.Objfile} object can become invalid
26491 if the object file it refers to is not loaded in @value{GDBN} any
26492 longer. All other @code{gdb.Objfile} methods will throw an exception
26493 if it is invalid at the time the method is called.
26496 @node Frames In Python
26497 @subsubsection Accessing inferior stack frames from Python.
26499 @cindex frames in python
26500 When the debugged program stops, @value{GDBN} is able to analyze its call
26501 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
26502 represents a frame in the stack. A @code{gdb.Frame} object is only valid
26503 while its corresponding frame exists in the inferior's stack. If you try
26504 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
26505 exception (@pxref{Exception Handling}).
26507 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
26511 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
26515 The following frame-related functions are available in the @code{gdb} module:
26517 @findex gdb.selected_frame
26518 @defun gdb.selected_frame ()
26519 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
26522 @findex gdb.newest_frame
26523 @defun gdb.newest_frame ()
26524 Return the newest frame object for the selected thread.
26527 @defun gdb.frame_stop_reason_string (reason)
26528 Return a string explaining the reason why @value{GDBN} stopped unwinding
26529 frames, as expressed by the given @var{reason} code (an integer, see the
26530 @code{unwind_stop_reason} method further down in this section).
26533 A @code{gdb.Frame} object has the following methods:
26535 @defun Frame.is_valid ()
26536 Returns true if the @code{gdb.Frame} object is valid, false if not.
26537 A frame object can become invalid if the frame it refers to doesn't
26538 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
26539 an exception if it is invalid at the time the method is called.
26542 @defun Frame.name ()
26543 Returns the function name of the frame, or @code{None} if it can't be
26547 @defun Frame.architecture ()
26548 Returns the @code{gdb.Architecture} object corresponding to the frame's
26549 architecture. @xref{Architectures In Python}.
26552 @defun Frame.type ()
26553 Returns the type of the frame. The value can be one of:
26555 @item gdb.NORMAL_FRAME
26556 An ordinary stack frame.
26558 @item gdb.DUMMY_FRAME
26559 A fake stack frame that was created by @value{GDBN} when performing an
26560 inferior function call.
26562 @item gdb.INLINE_FRAME
26563 A frame representing an inlined function. The function was inlined
26564 into a @code{gdb.NORMAL_FRAME} that is older than this one.
26566 @item gdb.TAILCALL_FRAME
26567 A frame representing a tail call. @xref{Tail Call Frames}.
26569 @item gdb.SIGTRAMP_FRAME
26570 A signal trampoline frame. This is the frame created by the OS when
26571 it calls into a signal handler.
26573 @item gdb.ARCH_FRAME
26574 A fake stack frame representing a cross-architecture call.
26576 @item gdb.SENTINEL_FRAME
26577 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
26582 @defun Frame.unwind_stop_reason ()
26583 Return an integer representing the reason why it's not possible to find
26584 more frames toward the outermost frame. Use
26585 @code{gdb.frame_stop_reason_string} to convert the value returned by this
26586 function to a string. The value can be one of:
26589 @item gdb.FRAME_UNWIND_NO_REASON
26590 No particular reason (older frames should be available).
26592 @item gdb.FRAME_UNWIND_NULL_ID
26593 The previous frame's analyzer returns an invalid result. This is no
26594 longer used by @value{GDBN}, and is kept only for backward
26597 @item gdb.FRAME_UNWIND_OUTERMOST
26598 This frame is the outermost.
26600 @item gdb.FRAME_UNWIND_UNAVAILABLE
26601 Cannot unwind further, because that would require knowing the
26602 values of registers or memory that have not been collected.
26604 @item gdb.FRAME_UNWIND_INNER_ID
26605 This frame ID looks like it ought to belong to a NEXT frame,
26606 but we got it for a PREV frame. Normally, this is a sign of
26607 unwinder failure. It could also indicate stack corruption.
26609 @item gdb.FRAME_UNWIND_SAME_ID
26610 This frame has the same ID as the previous one. That means
26611 that unwinding further would almost certainly give us another
26612 frame with exactly the same ID, so break the chain. Normally,
26613 this is a sign of unwinder failure. It could also indicate
26616 @item gdb.FRAME_UNWIND_NO_SAVED_PC
26617 The frame unwinder did not find any saved PC, but we needed
26618 one to unwind further.
26620 @item gdb.FRAME_UNWIND_FIRST_ERROR
26621 Any stop reason greater or equal to this value indicates some kind
26622 of error. This special value facilitates writing code that tests
26623 for errors in unwinding in a way that will work correctly even if
26624 the list of the other values is modified in future @value{GDBN}
26625 versions. Using it, you could write:
26627 reason = gdb.selected_frame().unwind_stop_reason ()
26628 reason_str = gdb.frame_stop_reason_string (reason)
26629 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
26630 print "An error occured: %s" % reason_str
26637 Returns the frame's resume address.
26640 @defun Frame.block ()
26641 Return the frame's code block. @xref{Blocks In Python}.
26644 @defun Frame.function ()
26645 Return the symbol for the function corresponding to this frame.
26646 @xref{Symbols In Python}.
26649 @defun Frame.older ()
26650 Return the frame that called this frame.
26653 @defun Frame.newer ()
26654 Return the frame called by this frame.
26657 @defun Frame.find_sal ()
26658 Return the frame's symtab and line object.
26659 @xref{Symbol Tables In Python}.
26662 @defun Frame.read_var (variable @r{[}, block@r{]})
26663 Return the value of @var{variable} in this frame. If the optional
26664 argument @var{block} is provided, search for the variable from that
26665 block; otherwise start at the frame's current block (which is
26666 determined by the frame's current program counter). @var{variable}
26667 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
26668 @code{gdb.Block} object.
26671 @defun Frame.select ()
26672 Set this frame to be the selected frame. @xref{Stack, ,Examining the
26676 @node Blocks In Python
26677 @subsubsection Accessing blocks from Python.
26679 @cindex blocks in python
26682 In @value{GDBN}, symbols are stored in blocks. A block corresponds
26683 roughly to a scope in the source code. Blocks are organized
26684 hierarchically, and are represented individually in Python as a
26685 @code{gdb.Block}. Blocks rely on debugging information being
26688 A frame has a block. Please see @ref{Frames In Python}, for a more
26689 in-depth discussion of frames.
26691 The outermost block is known as the @dfn{global block}. The global
26692 block typically holds public global variables and functions.
26694 The block nested just inside the global block is the @dfn{static
26695 block}. The static block typically holds file-scoped variables and
26698 @value{GDBN} provides a method to get a block's superblock, but there
26699 is currently no way to examine the sub-blocks of a block, or to
26700 iterate over all the blocks in a symbol table (@pxref{Symbol Tables In
26703 Here is a short example that should help explain blocks:
26706 /* This is in the global block. */
26709 /* This is in the static block. */
26710 static int file_scope;
26712 /* 'function' is in the global block, and 'argument' is
26713 in a block nested inside of 'function'. */
26714 int function (int argument)
26716 /* 'local' is in a block inside 'function'. It may or may
26717 not be in the same block as 'argument'. */
26721 /* 'inner' is in a block whose superblock is the one holding
26725 /* If this call is expanded by the compiler, you may see
26726 a nested block here whose function is 'inline_function'
26727 and whose superblock is the one holding 'inner'. */
26728 inline_function ();
26733 A @code{gdb.Block} is iterable. The iterator returns the symbols
26734 (@pxref{Symbols In Python}) local to the block. Python programs
26735 should not assume that a specific block object will always contain a
26736 given symbol, since changes in @value{GDBN} features and
26737 infrastructure may cause symbols move across blocks in a symbol
26740 The following block-related functions are available in the @code{gdb}
26743 @findex gdb.block_for_pc
26744 @defun gdb.block_for_pc (pc)
26745 Return the innermost @code{gdb.Block} containing the given @var{pc}
26746 value. If the block cannot be found for the @var{pc} value specified,
26747 the function will return @code{None}.
26750 A @code{gdb.Block} object has the following methods:
26752 @defun Block.is_valid ()
26753 Returns @code{True} if the @code{gdb.Block} object is valid,
26754 @code{False} if not. A block object can become invalid if the block it
26755 refers to doesn't exist anymore in the inferior. All other
26756 @code{gdb.Block} methods will throw an exception if it is invalid at
26757 the time the method is called. The block's validity is also checked
26758 during iteration over symbols of the block.
26761 A @code{gdb.Block} object has the following attributes:
26763 @defvar Block.start
26764 The start address of the block. This attribute is not writable.
26768 The end address of the block. This attribute is not writable.
26771 @defvar Block.function
26772 The name of the block represented as a @code{gdb.Symbol}. If the
26773 block is not named, then this attribute holds @code{None}. This
26774 attribute is not writable.
26776 For ordinary function blocks, the superblock is the static block.
26777 However, you should note that it is possible for a function block to
26778 have a superblock that is not the static block -- for instance this
26779 happens for an inlined function.
26782 @defvar Block.superblock
26783 The block containing this block. If this parent block does not exist,
26784 this attribute holds @code{None}. This attribute is not writable.
26787 @defvar Block.global_block
26788 The global block associated with this block. This attribute is not
26792 @defvar Block.static_block
26793 The static block associated with this block. This attribute is not
26797 @defvar Block.is_global
26798 @code{True} if the @code{gdb.Block} object is a global block,
26799 @code{False} if not. This attribute is not
26803 @defvar Block.is_static
26804 @code{True} if the @code{gdb.Block} object is a static block,
26805 @code{False} if not. This attribute is not writable.
26808 @node Symbols In Python
26809 @subsubsection Python representation of Symbols.
26811 @cindex symbols in python
26814 @value{GDBN} represents every variable, function and type as an
26815 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
26816 Similarly, Python represents these symbols in @value{GDBN} with the
26817 @code{gdb.Symbol} object.
26819 The following symbol-related functions are available in the @code{gdb}
26822 @findex gdb.lookup_symbol
26823 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
26824 This function searches for a symbol by name. The search scope can be
26825 restricted to the parameters defined in the optional domain and block
26828 @var{name} is the name of the symbol. It must be a string. The
26829 optional @var{block} argument restricts the search to symbols visible
26830 in that @var{block}. The @var{block} argument must be a
26831 @code{gdb.Block} object. If omitted, the block for the current frame
26832 is used. The optional @var{domain} argument restricts
26833 the search to the domain type. The @var{domain} argument must be a
26834 domain constant defined in the @code{gdb} module and described later
26837 The result is a tuple of two elements.
26838 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
26840 If the symbol is found, the second element is @code{True} if the symbol
26841 is a field of a method's object (e.g., @code{this} in C@t{++}),
26842 otherwise it is @code{False}.
26843 If the symbol is not found, the second element is @code{False}.
26846 @findex gdb.lookup_global_symbol
26847 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
26848 This function searches for a global symbol by name.
26849 The search scope can be restricted to by the domain argument.
26851 @var{name} is the name of the symbol. It must be a string.
26852 The optional @var{domain} argument restricts the search to the domain type.
26853 The @var{domain} argument must be a domain constant defined in the @code{gdb}
26854 module and described later in this chapter.
26856 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
26860 A @code{gdb.Symbol} object has the following attributes:
26862 @defvar Symbol.type
26863 The type of the symbol or @code{None} if no type is recorded.
26864 This attribute is represented as a @code{gdb.Type} object.
26865 @xref{Types In Python}. This attribute is not writable.
26868 @defvar Symbol.symtab
26869 The symbol table in which the symbol appears. This attribute is
26870 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
26871 Python}. This attribute is not writable.
26874 @defvar Symbol.line
26875 The line number in the source code at which the symbol was defined.
26876 This is an integer.
26879 @defvar Symbol.name
26880 The name of the symbol as a string. This attribute is not writable.
26883 @defvar Symbol.linkage_name
26884 The name of the symbol, as used by the linker (i.e., may be mangled).
26885 This attribute is not writable.
26888 @defvar Symbol.print_name
26889 The name of the symbol in a form suitable for output. This is either
26890 @code{name} or @code{linkage_name}, depending on whether the user
26891 asked @value{GDBN} to display demangled or mangled names.
26894 @defvar Symbol.addr_class
26895 The address class of the symbol. This classifies how to find the value
26896 of a symbol. Each address class is a constant defined in the
26897 @code{gdb} module and described later in this chapter.
26900 @defvar Symbol.needs_frame
26901 This is @code{True} if evaluating this symbol's value requires a frame
26902 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
26903 local variables will require a frame, but other symbols will not.
26906 @defvar Symbol.is_argument
26907 @code{True} if the symbol is an argument of a function.
26910 @defvar Symbol.is_constant
26911 @code{True} if the symbol is a constant.
26914 @defvar Symbol.is_function
26915 @code{True} if the symbol is a function or a method.
26918 @defvar Symbol.is_variable
26919 @code{True} if the symbol is a variable.
26922 A @code{gdb.Symbol} object has the following methods:
26924 @defun Symbol.is_valid ()
26925 Returns @code{True} if the @code{gdb.Symbol} object is valid,
26926 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
26927 the symbol it refers to does not exist in @value{GDBN} any longer.
26928 All other @code{gdb.Symbol} methods will throw an exception if it is
26929 invalid at the time the method is called.
26932 @defun Symbol.value (@r{[}frame@r{]})
26933 Compute the value of the symbol, as a @code{gdb.Value}. For
26934 functions, this computes the address of the function, cast to the
26935 appropriate type. If the symbol requires a frame in order to compute
26936 its value, then @var{frame} must be given. If @var{frame} is not
26937 given, or if @var{frame} is invalid, then this method will throw an
26941 The available domain categories in @code{gdb.Symbol} are represented
26942 as constants in the @code{gdb} module:
26945 @findex SYMBOL_UNDEF_DOMAIN
26946 @findex gdb.SYMBOL_UNDEF_DOMAIN
26947 @item gdb.SYMBOL_UNDEF_DOMAIN
26948 This is used when a domain has not been discovered or none of the
26949 following domains apply. This usually indicates an error either
26950 in the symbol information or in @value{GDBN}'s handling of symbols.
26951 @findex SYMBOL_VAR_DOMAIN
26952 @findex gdb.SYMBOL_VAR_DOMAIN
26953 @item gdb.SYMBOL_VAR_DOMAIN
26954 This domain contains variables, function names, typedef names and enum
26956 @findex SYMBOL_STRUCT_DOMAIN
26957 @findex gdb.SYMBOL_STRUCT_DOMAIN
26958 @item gdb.SYMBOL_STRUCT_DOMAIN
26959 This domain holds struct, union and enum type names.
26960 @findex SYMBOL_LABEL_DOMAIN
26961 @findex gdb.SYMBOL_LABEL_DOMAIN
26962 @item gdb.SYMBOL_LABEL_DOMAIN
26963 This domain contains names of labels (for gotos).
26964 @findex SYMBOL_VARIABLES_DOMAIN
26965 @findex gdb.SYMBOL_VARIABLES_DOMAIN
26966 @item gdb.SYMBOL_VARIABLES_DOMAIN
26967 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
26968 contains everything minus functions and types.
26969 @findex SYMBOL_FUNCTIONS_DOMAIN
26970 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
26971 @item gdb.SYMBOL_FUNCTION_DOMAIN
26972 This domain contains all functions.
26973 @findex SYMBOL_TYPES_DOMAIN
26974 @findex gdb.SYMBOL_TYPES_DOMAIN
26975 @item gdb.SYMBOL_TYPES_DOMAIN
26976 This domain contains all types.
26979 The available address class categories in @code{gdb.Symbol} are represented
26980 as constants in the @code{gdb} module:
26983 @findex SYMBOL_LOC_UNDEF
26984 @findex gdb.SYMBOL_LOC_UNDEF
26985 @item gdb.SYMBOL_LOC_UNDEF
26986 If this is returned by address class, it indicates an error either in
26987 the symbol information or in @value{GDBN}'s handling of symbols.
26988 @findex SYMBOL_LOC_CONST
26989 @findex gdb.SYMBOL_LOC_CONST
26990 @item gdb.SYMBOL_LOC_CONST
26991 Value is constant int.
26992 @findex SYMBOL_LOC_STATIC
26993 @findex gdb.SYMBOL_LOC_STATIC
26994 @item gdb.SYMBOL_LOC_STATIC
26995 Value is at a fixed address.
26996 @findex SYMBOL_LOC_REGISTER
26997 @findex gdb.SYMBOL_LOC_REGISTER
26998 @item gdb.SYMBOL_LOC_REGISTER
26999 Value is in a register.
27000 @findex SYMBOL_LOC_ARG
27001 @findex gdb.SYMBOL_LOC_ARG
27002 @item gdb.SYMBOL_LOC_ARG
27003 Value is an argument. This value is at the offset stored within the
27004 symbol inside the frame's argument list.
27005 @findex SYMBOL_LOC_REF_ARG
27006 @findex gdb.SYMBOL_LOC_REF_ARG
27007 @item gdb.SYMBOL_LOC_REF_ARG
27008 Value address is stored in the frame's argument list. Just like
27009 @code{LOC_ARG} except that the value's address is stored at the
27010 offset, not the value itself.
27011 @findex SYMBOL_LOC_REGPARM_ADDR
27012 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
27013 @item gdb.SYMBOL_LOC_REGPARM_ADDR
27014 Value is a specified register. Just like @code{LOC_REGISTER} except
27015 the register holds the address of the argument instead of the argument
27017 @findex SYMBOL_LOC_LOCAL
27018 @findex gdb.SYMBOL_LOC_LOCAL
27019 @item gdb.SYMBOL_LOC_LOCAL
27020 Value is a local variable.
27021 @findex SYMBOL_LOC_TYPEDEF
27022 @findex gdb.SYMBOL_LOC_TYPEDEF
27023 @item gdb.SYMBOL_LOC_TYPEDEF
27024 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
27026 @findex SYMBOL_LOC_BLOCK
27027 @findex gdb.SYMBOL_LOC_BLOCK
27028 @item gdb.SYMBOL_LOC_BLOCK
27030 @findex SYMBOL_LOC_CONST_BYTES
27031 @findex gdb.SYMBOL_LOC_CONST_BYTES
27032 @item gdb.SYMBOL_LOC_CONST_BYTES
27033 Value is a byte-sequence.
27034 @findex SYMBOL_LOC_UNRESOLVED
27035 @findex gdb.SYMBOL_LOC_UNRESOLVED
27036 @item gdb.SYMBOL_LOC_UNRESOLVED
27037 Value is at a fixed address, but the address of the variable has to be
27038 determined from the minimal symbol table whenever the variable is
27040 @findex SYMBOL_LOC_OPTIMIZED_OUT
27041 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
27042 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
27043 The value does not actually exist in the program.
27044 @findex SYMBOL_LOC_COMPUTED
27045 @findex gdb.SYMBOL_LOC_COMPUTED
27046 @item gdb.SYMBOL_LOC_COMPUTED
27047 The value's address is a computed location.
27050 @node Symbol Tables In Python
27051 @subsubsection Symbol table representation in Python.
27053 @cindex symbol tables in python
27055 @tindex gdb.Symtab_and_line
27057 Access to symbol table data maintained by @value{GDBN} on the inferior
27058 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
27059 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
27060 from the @code{find_sal} method in @code{gdb.Frame} object.
27061 @xref{Frames In Python}.
27063 For more information on @value{GDBN}'s symbol table management, see
27064 @ref{Symbols, ,Examining the Symbol Table}, for more information.
27066 A @code{gdb.Symtab_and_line} object has the following attributes:
27068 @defvar Symtab_and_line.symtab
27069 The symbol table object (@code{gdb.Symtab}) for this frame.
27070 This attribute is not writable.
27073 @defvar Symtab_and_line.pc
27074 Indicates the start of the address range occupied by code for the
27075 current source line. This attribute is not writable.
27078 @defvar Symtab_and_line.last
27079 Indicates the end of the address range occupied by code for the current
27080 source line. This attribute is not writable.
27083 @defvar Symtab_and_line.line
27084 Indicates the current line number for this object. This
27085 attribute is not writable.
27088 A @code{gdb.Symtab_and_line} object has the following methods:
27090 @defun Symtab_and_line.is_valid ()
27091 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
27092 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
27093 invalid if the Symbol table and line object it refers to does not
27094 exist in @value{GDBN} any longer. All other
27095 @code{gdb.Symtab_and_line} methods will throw an exception if it is
27096 invalid at the time the method is called.
27099 A @code{gdb.Symtab} object has the following attributes:
27101 @defvar Symtab.filename
27102 The symbol table's source filename. This attribute is not writable.
27105 @defvar Symtab.objfile
27106 The symbol table's backing object file. @xref{Objfiles In Python}.
27107 This attribute is not writable.
27110 A @code{gdb.Symtab} object has the following methods:
27112 @defun Symtab.is_valid ()
27113 Returns @code{True} if the @code{gdb.Symtab} object is valid,
27114 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
27115 the symbol table it refers to does not exist in @value{GDBN} any
27116 longer. All other @code{gdb.Symtab} methods will throw an exception
27117 if it is invalid at the time the method is called.
27120 @defun Symtab.fullname ()
27121 Return the symbol table's source absolute file name.
27124 @defun Symtab.global_block ()
27125 Return the global block of the underlying symbol table.
27126 @xref{Blocks In Python}.
27129 @defun Symtab.static_block ()
27130 Return the static block of the underlying symbol table.
27131 @xref{Blocks In Python}.
27134 @defun Symtab.linetable ()
27135 Return the line table associated with the symbol table.
27136 @xref{Line Tables In Python}.
27139 @node Line Tables In Python
27140 @subsubsection Manipulating line tables using Python
27142 @cindex line tables in python
27143 @tindex gdb.LineTable
27145 Python code can request and inspect line table information from a
27146 symbol table that is loaded in @value{GDBN}. A line table is a
27147 mapping of source lines to their executable locations in memory. To
27148 acquire the line table information for a particular symbol table, use
27149 the @code{linetable} function (@pxref{Symbol Tables In Python}).
27151 A @code{gdb.LineTable} is iterable. The iterator returns
27152 @code{LineTableEntry} objects that correspond to the source line and
27153 address for each line table entry. @code{LineTableEntry} objects have
27154 the following attributes:
27156 @defvar LineTableEntry.line
27157 The source line number for this line table entry. This number
27158 corresponds to the actual line of source. This attribute is not
27162 @defvar LineTableEntry.pc
27163 The address that is associated with the line table entry where the
27164 executable code for that source line resides in memory. This
27165 attribute is not writable.
27168 As there can be multiple addresses for a single source line, you may
27169 receive multiple @code{LineTableEntry} objects with matching
27170 @code{line} attributes, but with different @code{pc} attributes. The
27171 iterator is sorted in ascending @code{pc} order. Here is a small
27172 example illustrating iterating over a line table.
27175 symtab = gdb.selected_frame().find_sal().symtab
27176 linetable = symtab.linetable()
27177 for line in linetable:
27178 print "Line: "+str(line.line)+" Address: "+hex(line.pc)
27181 This will have the following output:
27184 Line: 33 Address: 0x4005c8L
27185 Line: 37 Address: 0x4005caL
27186 Line: 39 Address: 0x4005d2L
27187 Line: 40 Address: 0x4005f8L
27188 Line: 42 Address: 0x4005ffL
27189 Line: 44 Address: 0x400608L
27190 Line: 42 Address: 0x40060cL
27191 Line: 45 Address: 0x400615L
27194 In addition to being able to iterate over a @code{LineTable}, it also
27195 has the following direct access methods:
27197 @defun LineTable.line (line)
27198 Return a Python @code{Tuple} of @code{LineTableEntry} objects for any
27199 entries in the line table for the given @var{line}. @var{line} refers
27200 to the source code line. If there are no entries for that source code
27201 @var{line}, the Python @code{None} is returned.
27204 @defun LineTable.has_line (line)
27205 Return a Python @code{Boolean} indicating whether there is an entry in
27206 the line table for this source line. Return @code{True} if an entry
27207 is found, or @code{False} if not.
27210 @defun LineTable.source_lines ()
27211 Return a Python @code{List} of the source line numbers in the symbol
27212 table. Only lines with executable code locations are returned. The
27213 contents of the @code{List} will just be the source line entries
27214 represented as Python @code{Long} values.
27217 @node Breakpoints In Python
27218 @subsubsection Manipulating breakpoints using Python
27220 @cindex breakpoints in python
27221 @tindex gdb.Breakpoint
27223 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
27226 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal @r{[},temporary@r{]]]]})
27227 Create a new breakpoint. @var{spec} is a string naming the location
27228 of the breakpoint, or an expression that defines a watchpoint. The
27229 contents can be any location recognized by the @code{break} command,
27230 or in the case of a watchpoint, by the @code{watch} command. The
27231 optional @var{type} denotes the breakpoint to create from the types
27232 defined later in this chapter. This argument can be either:
27233 @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
27234 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal}
27235 argument allows the breakpoint to become invisible to the user. The
27236 breakpoint will neither be reported when created, nor will it be
27237 listed in the output from @code{info breakpoints} (but will be listed
27238 with the @code{maint info breakpoints} command). The optional
27239 @var{temporary} argument makes the breakpoint a temporary breakpoint.
27240 Temporary breakpoints are deleted after they have been hit. Any
27241 further access to the Python breakpoint after it has been hit will
27242 result in a runtime error (as that breakpoint has now been
27243 automatically deleted). The optional @var{wp_class} argument defines
27244 the class of watchpoint to create, if @var{type} is
27245 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it
27246 is assumed to be a @code{gdb.WP_WRITE} class.
27249 @defun Breakpoint.stop (self)
27250 The @code{gdb.Breakpoint} class can be sub-classed and, in
27251 particular, you may choose to implement the @code{stop} method.
27252 If this method is defined in a sub-class of @code{gdb.Breakpoint},
27253 it will be called when the inferior reaches any location of a
27254 breakpoint which instantiates that sub-class. If the method returns
27255 @code{True}, the inferior will be stopped at the location of the
27256 breakpoint, otherwise the inferior will continue.
27258 If there are multiple breakpoints at the same location with a
27259 @code{stop} method, each one will be called regardless of the
27260 return status of the previous. This ensures that all @code{stop}
27261 methods have a chance to execute at that location. In this scenario
27262 if one of the methods returns @code{True} but the others return
27263 @code{False}, the inferior will still be stopped.
27265 You should not alter the execution state of the inferior (i.e.@:, step,
27266 next, etc.), alter the current frame context (i.e.@:, change the current
27267 active frame), or alter, add or delete any breakpoint. As a general
27268 rule, you should not alter any data within @value{GDBN} or the inferior
27271 Example @code{stop} implementation:
27274 class MyBreakpoint (gdb.Breakpoint):
27276 inf_val = gdb.parse_and_eval("foo")
27283 The available watchpoint types represented by constants are defined in the
27288 @findex gdb.WP_READ
27290 Read only watchpoint.
27293 @findex gdb.WP_WRITE
27295 Write only watchpoint.
27298 @findex gdb.WP_ACCESS
27299 @item gdb.WP_ACCESS
27300 Read/Write watchpoint.
27303 @defun Breakpoint.is_valid ()
27304 Return @code{True} if this @code{Breakpoint} object is valid,
27305 @code{False} otherwise. A @code{Breakpoint} object can become invalid
27306 if the user deletes the breakpoint. In this case, the object still
27307 exists, but the underlying breakpoint does not. In the cases of
27308 watchpoint scope, the watchpoint remains valid even if execution of the
27309 inferior leaves the scope of that watchpoint.
27312 @defun Breakpoint.delete
27313 Permanently deletes the @value{GDBN} breakpoint. This also
27314 invalidates the Python @code{Breakpoint} object. Any further access
27315 to this object's attributes or methods will raise an error.
27318 @defvar Breakpoint.enabled
27319 This attribute is @code{True} if the breakpoint is enabled, and
27320 @code{False} otherwise. This attribute is writable.
27323 @defvar Breakpoint.silent
27324 This attribute is @code{True} if the breakpoint is silent, and
27325 @code{False} otherwise. This attribute is writable.
27327 Note that a breakpoint can also be silent if it has commands and the
27328 first command is @code{silent}. This is not reported by the
27329 @code{silent} attribute.
27332 @defvar Breakpoint.thread
27333 If the breakpoint is thread-specific, this attribute holds the thread
27334 id. If the breakpoint is not thread-specific, this attribute is
27335 @code{None}. This attribute is writable.
27338 @defvar Breakpoint.task
27339 If the breakpoint is Ada task-specific, this attribute holds the Ada task
27340 id. If the breakpoint is not task-specific (or the underlying
27341 language is not Ada), this attribute is @code{None}. This attribute
27345 @defvar Breakpoint.ignore_count
27346 This attribute holds the ignore count for the breakpoint, an integer.
27347 This attribute is writable.
27350 @defvar Breakpoint.number
27351 This attribute holds the breakpoint's number --- the identifier used by
27352 the user to manipulate the breakpoint. This attribute is not writable.
27355 @defvar Breakpoint.type
27356 This attribute holds the breakpoint's type --- the identifier used to
27357 determine the actual breakpoint type or use-case. This attribute is not
27361 @defvar Breakpoint.visible
27362 This attribute tells whether the breakpoint is visible to the user
27363 when set, or when the @samp{info breakpoints} command is run. This
27364 attribute is not writable.
27367 @defvar Breakpoint.temporary
27368 This attribute indicates whether the breakpoint was created as a
27369 temporary breakpoint. Temporary breakpoints are automatically deleted
27370 after that breakpoint has been hit. Access to this attribute, and all
27371 other attributes and functions other than the @code{is_valid}
27372 function, will result in an error after the breakpoint has been hit
27373 (as it has been automatically deleted). This attribute is not
27377 The available types are represented by constants defined in the @code{gdb}
27381 @findex BP_BREAKPOINT
27382 @findex gdb.BP_BREAKPOINT
27383 @item gdb.BP_BREAKPOINT
27384 Normal code breakpoint.
27386 @findex BP_WATCHPOINT
27387 @findex gdb.BP_WATCHPOINT
27388 @item gdb.BP_WATCHPOINT
27389 Watchpoint breakpoint.
27391 @findex BP_HARDWARE_WATCHPOINT
27392 @findex gdb.BP_HARDWARE_WATCHPOINT
27393 @item gdb.BP_HARDWARE_WATCHPOINT
27394 Hardware assisted watchpoint.
27396 @findex BP_READ_WATCHPOINT
27397 @findex gdb.BP_READ_WATCHPOINT
27398 @item gdb.BP_READ_WATCHPOINT
27399 Hardware assisted read watchpoint.
27401 @findex BP_ACCESS_WATCHPOINT
27402 @findex gdb.BP_ACCESS_WATCHPOINT
27403 @item gdb.BP_ACCESS_WATCHPOINT
27404 Hardware assisted access watchpoint.
27407 @defvar Breakpoint.hit_count
27408 This attribute holds the hit count for the breakpoint, an integer.
27409 This attribute is writable, but currently it can only be set to zero.
27412 @defvar Breakpoint.location
27413 This attribute holds the location of the breakpoint, as specified by
27414 the user. It is a string. If the breakpoint does not have a location
27415 (that is, it is a watchpoint) the attribute's value is @code{None}. This
27416 attribute is not writable.
27419 @defvar Breakpoint.expression
27420 This attribute holds a breakpoint expression, as specified by
27421 the user. It is a string. If the breakpoint does not have an
27422 expression (the breakpoint is not a watchpoint) the attribute's value
27423 is @code{None}. This attribute is not writable.
27426 @defvar Breakpoint.condition
27427 This attribute holds the condition of the breakpoint, as specified by
27428 the user. It is a string. If there is no condition, this attribute's
27429 value is @code{None}. This attribute is writable.
27432 @defvar Breakpoint.commands
27433 This attribute holds the commands attached to the breakpoint. If
27434 there are commands, this attribute's value is a string holding all the
27435 commands, separated by newlines. If there are no commands, this
27436 attribute is @code{None}. This attribute is not writable.
27439 @node Finish Breakpoints in Python
27440 @subsubsection Finish Breakpoints
27442 @cindex python finish breakpoints
27443 @tindex gdb.FinishBreakpoint
27445 A finish breakpoint is a temporary breakpoint set at the return address of
27446 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
27447 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
27448 and deleted when the execution will run out of the breakpoint scope (i.e.@:
27449 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
27450 Finish breakpoints are thread specific and must be create with the right
27453 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
27454 Create a finish breakpoint at the return address of the @code{gdb.Frame}
27455 object @var{frame}. If @var{frame} is not provided, this defaults to the
27456 newest frame. The optional @var{internal} argument allows the breakpoint to
27457 become invisible to the user. @xref{Breakpoints In Python}, for further
27458 details about this argument.
27461 @defun FinishBreakpoint.out_of_scope (self)
27462 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
27463 @code{return} command, @dots{}), a function may not properly terminate, and
27464 thus never hit the finish breakpoint. When @value{GDBN} notices such a
27465 situation, the @code{out_of_scope} callback will be triggered.
27467 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
27471 class MyFinishBreakpoint (gdb.FinishBreakpoint)
27473 print "normal finish"
27476 def out_of_scope ():
27477 print "abnormal finish"
27481 @defvar FinishBreakpoint.return_value
27482 When @value{GDBN} is stopped at a finish breakpoint and the frame
27483 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
27484 attribute will contain a @code{gdb.Value} object corresponding to the return
27485 value of the function. The value will be @code{None} if the function return
27486 type is @code{void} or if the return value was not computable. This attribute
27490 @node Lazy Strings In Python
27491 @subsubsection Python representation of lazy strings.
27493 @cindex lazy strings in python
27494 @tindex gdb.LazyString
27496 A @dfn{lazy string} is a string whose contents is not retrieved or
27497 encoded until it is needed.
27499 A @code{gdb.LazyString} is represented in @value{GDBN} as an
27500 @code{address} that points to a region of memory, an @code{encoding}
27501 that will be used to encode that region of memory, and a @code{length}
27502 to delimit the region of memory that represents the string. The
27503 difference between a @code{gdb.LazyString} and a string wrapped within
27504 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
27505 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
27506 retrieved and encoded during printing, while a @code{gdb.Value}
27507 wrapping a string is immediately retrieved and encoded on creation.
27509 A @code{gdb.LazyString} object has the following functions:
27511 @defun LazyString.value ()
27512 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
27513 will point to the string in memory, but will lose all the delayed
27514 retrieval, encoding and handling that @value{GDBN} applies to a
27515 @code{gdb.LazyString}.
27518 @defvar LazyString.address
27519 This attribute holds the address of the string. This attribute is not
27523 @defvar LazyString.length
27524 This attribute holds the length of the string in characters. If the
27525 length is -1, then the string will be fetched and encoded up to the
27526 first null of appropriate width. This attribute is not writable.
27529 @defvar LazyString.encoding
27530 This attribute holds the encoding that will be applied to the string
27531 when the string is printed by @value{GDBN}. If the encoding is not
27532 set, or contains an empty string, then @value{GDBN} will select the
27533 most appropriate encoding when the string is printed. This attribute
27537 @defvar LazyString.type
27538 This attribute holds the type that is represented by the lazy string's
27539 type. For a lazy string this will always be a pointer type. To
27540 resolve this to the lazy string's character type, use the type's
27541 @code{target} method. @xref{Types In Python}. This attribute is not
27545 @node Architectures In Python
27546 @subsubsection Python representation of architectures
27547 @cindex Python architectures
27549 @value{GDBN} uses architecture specific parameters and artifacts in a
27550 number of its various computations. An architecture is represented
27551 by an instance of the @code{gdb.Architecture} class.
27553 A @code{gdb.Architecture} class has the following methods:
27555 @defun Architecture.name ()
27556 Return the name (string value) of the architecture.
27559 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
27560 Return a list of disassembled instructions starting from the memory
27561 address @var{start_pc}. The optional arguments @var{end_pc} and
27562 @var{count} determine the number of instructions in the returned list.
27563 If both the optional arguments @var{end_pc} and @var{count} are
27564 specified, then a list of at most @var{count} disassembled instructions
27565 whose start address falls in the closed memory address interval from
27566 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
27567 specified, but @var{count} is specified, then @var{count} number of
27568 instructions starting from the address @var{start_pc} are returned. If
27569 @var{count} is not specified but @var{end_pc} is specified, then all
27570 instructions whose start address falls in the closed memory address
27571 interval from @var{start_pc} to @var{end_pc} are returned. If neither
27572 @var{end_pc} nor @var{count} are specified, then a single instruction at
27573 @var{start_pc} is returned. For all of these cases, each element of the
27574 returned list is a Python @code{dict} with the following string keys:
27579 The value corresponding to this key is a Python long integer capturing
27580 the memory address of the instruction.
27583 The value corresponding to this key is a string value which represents
27584 the instruction with assembly language mnemonics. The assembly
27585 language flavor used is the same as that specified by the current CLI
27586 variable @code{disassembly-flavor}. @xref{Machine Code}.
27589 The value corresponding to this key is the length (integer value) of the
27590 instruction in bytes.
27595 @node Python Auto-loading
27596 @subsection Python Auto-loading
27597 @cindex Python auto-loading
27599 When a new object file is read (for example, due to the @code{file}
27600 command, or because the inferior has loaded a shared library),
27601 @value{GDBN} will look for Python support scripts in several ways:
27602 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
27603 and @code{.debug_gdb_scripts} section
27604 (@pxref{dotdebug_gdb_scripts section}).
27606 The auto-loading feature is useful for supplying application-specific
27607 debugging commands and scripts.
27609 Auto-loading can be enabled or disabled,
27610 and the list of auto-loaded scripts can be printed.
27613 @anchor{set auto-load python-scripts}
27614 @kindex set auto-load python-scripts
27615 @item set auto-load python-scripts [on|off]
27616 Enable or disable the auto-loading of Python scripts.
27618 @anchor{show auto-load python-scripts}
27619 @kindex show auto-load python-scripts
27620 @item show auto-load python-scripts
27621 Show whether auto-loading of Python scripts is enabled or disabled.
27623 @anchor{info auto-load python-scripts}
27624 @kindex info auto-load python-scripts
27625 @cindex print list of auto-loaded Python scripts
27626 @item info auto-load python-scripts [@var{regexp}]
27627 Print the list of all Python scripts that @value{GDBN} auto-loaded.
27629 Also printed is the list of Python scripts that were mentioned in
27630 the @code{.debug_gdb_scripts} section and were not found
27631 (@pxref{dotdebug_gdb_scripts section}).
27632 This is useful because their names are not printed when @value{GDBN}
27633 tries to load them and fails. There may be many of them, and printing
27634 an error message for each one is problematic.
27636 If @var{regexp} is supplied only Python scripts with matching names are printed.
27641 (gdb) info auto-load python-scripts
27643 Yes py-section-script.py
27644 full name: /tmp/py-section-script.py
27645 No my-foo-pretty-printers.py
27649 When reading an auto-loaded file, @value{GDBN} sets the
27650 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
27651 function (@pxref{Objfiles In Python}). This can be useful for
27652 registering objfile-specific pretty-printers and frame-filters.
27655 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
27656 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
27657 * Which flavor to choose?::
27660 @node objfile-gdb.py file
27661 @subsubsection The @file{@var{objfile}-gdb.py} file
27662 @cindex @file{@var{objfile}-gdb.py}
27664 When a new object file is read, @value{GDBN} looks for
27665 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
27666 where @var{objfile} is the object file's real name, formed by ensuring
27667 that the file name is absolute, following all symlinks, and resolving
27668 @code{.} and @code{..} components. If this file exists and is
27669 readable, @value{GDBN} will evaluate it as a Python script.
27671 If this file does not exist, then @value{GDBN} will look for
27672 @var{script-name} file in all of the directories as specified below.
27674 Note that loading of this script file also requires accordingly configured
27675 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27677 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
27678 scripts normally according to its @file{.exe} filename. But if no scripts are
27679 found @value{GDBN} also tries script filenames matching the object file without
27680 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
27681 is attempted on any platform. This makes the script filenames compatible
27682 between Unix and MS-Windows hosts.
27685 @anchor{set auto-load scripts-directory}
27686 @kindex set auto-load scripts-directory
27687 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
27688 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
27689 may be delimited by the host platform path separator in use
27690 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
27692 Each entry here needs to be covered also by the security setting
27693 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
27695 @anchor{with-auto-load-dir}
27696 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
27697 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
27698 configuration option @option{--with-auto-load-dir}.
27700 Any reference to @file{$debugdir} will get replaced by
27701 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
27702 reference to @file{$datadir} will get replaced by @var{data-directory} which is
27703 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
27704 @file{$datadir} must be placed as a directory component --- either alone or
27705 delimited by @file{/} or @file{\} directory separators, depending on the host
27708 The list of directories uses path separator (@samp{:} on GNU and Unix
27709 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27710 to the @env{PATH} environment variable.
27712 @anchor{show auto-load scripts-directory}
27713 @kindex show auto-load scripts-directory
27714 @item show auto-load scripts-directory
27715 Show @value{GDBN} auto-loaded scripts location.
27718 @value{GDBN} does not track which files it has already auto-loaded this way.
27719 @value{GDBN} will load the associated script every time the corresponding
27720 @var{objfile} is opened.
27721 So your @file{-gdb.py} file should be careful to avoid errors if it
27722 is evaluated more than once.
27724 @node dotdebug_gdb_scripts section
27725 @subsubsection The @code{.debug_gdb_scripts} section
27726 @cindex @code{.debug_gdb_scripts} section
27728 For systems using file formats like ELF and COFF,
27729 when @value{GDBN} loads a new object file
27730 it will look for a special section named @samp{.debug_gdb_scripts}.
27731 If this section exists, its contents is a list of names of scripts to load.
27733 @value{GDBN} will look for each specified script file first in the
27734 current directory and then along the source search path
27735 (@pxref{Source Path, ,Specifying Source Directories}),
27736 except that @file{$cdir} is not searched, since the compilation
27737 directory is not relevant to scripts.
27739 Entries can be placed in section @code{.debug_gdb_scripts} with,
27740 for example, this GCC macro:
27743 /* Note: The "MS" section flags are to remove duplicates. */
27744 #define DEFINE_GDB_SCRIPT(script_name) \
27746 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
27748 .asciz \"" script_name "\"\n\
27754 Then one can reference the macro in a header or source file like this:
27757 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
27760 The script name may include directories if desired.
27762 Note that loading of this script file also requires accordingly configured
27763 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27765 If the macro is put in a header, any application or library
27766 using this header will get a reference to the specified script.
27768 @node Which flavor to choose?
27769 @subsubsection Which flavor to choose?
27771 Given the multiple ways of auto-loading Python scripts, it might not always
27772 be clear which one to choose. This section provides some guidance.
27774 Benefits of the @file{-gdb.py} way:
27778 Can be used with file formats that don't support multiple sections.
27781 Ease of finding scripts for public libraries.
27783 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
27784 in the source search path.
27785 For publicly installed libraries, e.g., @file{libstdc++}, there typically
27786 isn't a source directory in which to find the script.
27789 Doesn't require source code additions.
27792 Benefits of the @code{.debug_gdb_scripts} way:
27796 Works with static linking.
27798 Scripts for libraries done the @file{-gdb.py} way require an objfile to
27799 trigger their loading. When an application is statically linked the only
27800 objfile available is the executable, and it is cumbersome to attach all the
27801 scripts from all the input libraries to the executable's @file{-gdb.py} script.
27804 Works with classes that are entirely inlined.
27806 Some classes can be entirely inlined, and thus there may not be an associated
27807 shared library to attach a @file{-gdb.py} script to.
27810 Scripts needn't be copied out of the source tree.
27812 In some circumstances, apps can be built out of large collections of internal
27813 libraries, and the build infrastructure necessary to install the
27814 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
27815 cumbersome. It may be easier to specify the scripts in the
27816 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
27817 top of the source tree to the source search path.
27820 @node Python modules
27821 @subsection Python modules
27822 @cindex python modules
27824 @value{GDBN} comes with several modules to assist writing Python code.
27827 * gdb.printing:: Building and registering pretty-printers.
27828 * gdb.types:: Utilities for working with types.
27829 * gdb.prompt:: Utilities for prompt value substitution.
27833 @subsubsection gdb.printing
27834 @cindex gdb.printing
27836 This module provides a collection of utilities for working with
27840 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
27841 This class specifies the API that makes @samp{info pretty-printer},
27842 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
27843 Pretty-printers should generally inherit from this class.
27845 @item SubPrettyPrinter (@var{name})
27846 For printers that handle multiple types, this class specifies the
27847 corresponding API for the subprinters.
27849 @item RegexpCollectionPrettyPrinter (@var{name})
27850 Utility class for handling multiple printers, all recognized via
27851 regular expressions.
27852 @xref{Writing a Pretty-Printer}, for an example.
27854 @item FlagEnumerationPrinter (@var{name})
27855 A pretty-printer which handles printing of @code{enum} values. Unlike
27856 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
27857 work properly when there is some overlap between the enumeration
27858 constants. @var{name} is the name of the printer and also the name of
27859 the @code{enum} type to look up.
27861 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
27862 Register @var{printer} with the pretty-printer list of @var{obj}.
27863 If @var{replace} is @code{True} then any existing copy of the printer
27864 is replaced. Otherwise a @code{RuntimeError} exception is raised
27865 if a printer with the same name already exists.
27869 @subsubsection gdb.types
27872 This module provides a collection of utilities for working with
27873 @code{gdb.Type} objects.
27876 @item get_basic_type (@var{type})
27877 Return @var{type} with const and volatile qualifiers stripped,
27878 and with typedefs and C@t{++} references converted to the underlying type.
27883 typedef const int const_int;
27885 const_int& foo_ref (foo);
27886 int main () @{ return 0; @}
27893 (gdb) python import gdb.types
27894 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
27895 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
27899 @item has_field (@var{type}, @var{field})
27900 Return @code{True} if @var{type}, assumed to be a type with fields
27901 (e.g., a structure or union), has field @var{field}.
27903 @item make_enum_dict (@var{enum_type})
27904 Return a Python @code{dictionary} type produced from @var{enum_type}.
27906 @item deep_items (@var{type})
27907 Returns a Python iterator similar to the standard
27908 @code{gdb.Type.iteritems} method, except that the iterator returned
27909 by @code{deep_items} will recursively traverse anonymous struct or
27910 union fields. For example:
27924 Then in @value{GDBN}:
27926 (@value{GDBP}) python import gdb.types
27927 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
27928 (@value{GDBP}) python print struct_a.keys ()
27930 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
27931 @{['a', 'b0', 'b1']@}
27934 @item get_type_recognizers ()
27935 Return a list of the enabled type recognizers for the current context.
27936 This is called by @value{GDBN} during the type-printing process
27937 (@pxref{Type Printing API}).
27939 @item apply_type_recognizers (recognizers, type_obj)
27940 Apply the type recognizers, @var{recognizers}, to the type object
27941 @var{type_obj}. If any recognizer returns a string, return that
27942 string. Otherwise, return @code{None}. This is called by
27943 @value{GDBN} during the type-printing process (@pxref{Type Printing
27946 @item register_type_printer (locus, printer)
27947 This is a convenience function to register a type printer.
27948 @var{printer} is the type printer to register. It must implement the
27949 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
27950 which case the printer is registered with that objfile; a
27951 @code{gdb.Progspace}, in which case the printer is registered with
27952 that progspace; or @code{None}, in which case the printer is
27953 registered globally.
27956 This is a base class that implements the type printer protocol. Type
27957 printers are encouraged, but not required, to derive from this class.
27958 It defines a constructor:
27960 @defmethod TypePrinter __init__ (self, name)
27961 Initialize the type printer with the given name. The new printer
27962 starts in the enabled state.
27968 @subsubsection gdb.prompt
27971 This module provides a method for prompt value-substitution.
27974 @item substitute_prompt (@var{string})
27975 Return @var{string} with escape sequences substituted by values. Some
27976 escape sequences take arguments. You can specify arguments inside
27977 ``@{@}'' immediately following the escape sequence.
27979 The escape sequences you can pass to this function are:
27983 Substitute a backslash.
27985 Substitute an ESC character.
27987 Substitute the selected frame; an argument names a frame parameter.
27989 Substitute a newline.
27991 Substitute a parameter's value; the argument names the parameter.
27993 Substitute a carriage return.
27995 Substitute the selected thread; an argument names a thread parameter.
27997 Substitute the version of GDB.
27999 Substitute the current working directory.
28001 Begin a sequence of non-printing characters. These sequences are
28002 typically used with the ESC character, and are not counted in the string
28003 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
28004 blue-colored ``(gdb)'' prompt where the length is five.
28006 End a sequence of non-printing characters.
28012 substitute_prompt (``frame: \f,
28013 print arguments: \p@{print frame-arguments@}'')
28016 @exdent will return the string:
28019 "frame: main, print arguments: scalars"
28024 @section Creating new spellings of existing commands
28025 @cindex aliases for commands
28027 It is often useful to define alternate spellings of existing commands.
28028 For example, if a new @value{GDBN} command defined in Python has
28029 a long name to type, it is handy to have an abbreviated version of it
28030 that involves less typing.
28032 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
28033 of the @samp{step} command even though it is otherwise an ambiguous
28034 abbreviation of other commands like @samp{set} and @samp{show}.
28036 Aliases are also used to provide shortened or more common versions
28037 of multi-word commands. For example, @value{GDBN} provides the
28038 @samp{tty} alias of the @samp{set inferior-tty} command.
28040 You can define a new alias with the @samp{alias} command.
28045 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
28049 @var{ALIAS} specifies the name of the new alias.
28050 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
28053 @var{COMMAND} specifies the name of an existing command
28054 that is being aliased.
28056 The @samp{-a} option specifies that the new alias is an abbreviation
28057 of the command. Abbreviations are not shown in command
28058 lists displayed by the @samp{help} command.
28060 The @samp{--} option specifies the end of options,
28061 and is useful when @var{ALIAS} begins with a dash.
28063 Here is a simple example showing how to make an abbreviation
28064 of a command so that there is less to type.
28065 Suppose you were tired of typing @samp{disas}, the current
28066 shortest unambiguous abbreviation of the @samp{disassemble} command
28067 and you wanted an even shorter version named @samp{di}.
28068 The following will accomplish this.
28071 (gdb) alias -a di = disas
28074 Note that aliases are different from user-defined commands.
28075 With a user-defined command, you also need to write documentation
28076 for it with the @samp{document} command.
28077 An alias automatically picks up the documentation of the existing command.
28079 Here is an example where we make @samp{elms} an abbreviation of
28080 @samp{elements} in the @samp{set print elements} command.
28081 This is to show that you can make an abbreviation of any part
28085 (gdb) alias -a set print elms = set print elements
28086 (gdb) alias -a show print elms = show print elements
28087 (gdb) set p elms 20
28089 Limit on string chars or array elements to print is 200.
28092 Note that if you are defining an alias of a @samp{set} command,
28093 and you want to have an alias for the corresponding @samp{show}
28094 command, then you need to define the latter separately.
28096 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
28097 @var{ALIAS}, just as they are normally.
28100 (gdb) alias -a set pr elms = set p ele
28103 Finally, here is an example showing the creation of a one word
28104 alias for a more complex command.
28105 This creates alias @samp{spe} of the command @samp{set print elements}.
28108 (gdb) alias spe = set print elements
28113 @chapter Command Interpreters
28114 @cindex command interpreters
28116 @value{GDBN} supports multiple command interpreters, and some command
28117 infrastructure to allow users or user interface writers to switch
28118 between interpreters or run commands in other interpreters.
28120 @value{GDBN} currently supports two command interpreters, the console
28121 interpreter (sometimes called the command-line interpreter or @sc{cli})
28122 and the machine interface interpreter (or @sc{gdb/mi}). This manual
28123 describes both of these interfaces in great detail.
28125 By default, @value{GDBN} will start with the console interpreter.
28126 However, the user may choose to start @value{GDBN} with another
28127 interpreter by specifying the @option{-i} or @option{--interpreter}
28128 startup options. Defined interpreters include:
28132 @cindex console interpreter
28133 The traditional console or command-line interpreter. This is the most often
28134 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
28135 @value{GDBN} will use this interpreter.
28138 @cindex mi interpreter
28139 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
28140 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
28141 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
28145 @cindex mi2 interpreter
28146 The current @sc{gdb/mi} interface.
28149 @cindex mi1 interpreter
28150 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
28154 @cindex invoke another interpreter
28155 The interpreter being used by @value{GDBN} may not be dynamically
28156 switched at runtime. Although possible, this could lead to a very
28157 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
28158 enters the command "interpreter-set console" in a console view,
28159 @value{GDBN} would switch to using the console interpreter, rendering
28160 the IDE inoperable!
28162 @kindex interpreter-exec
28163 Although you may only choose a single interpreter at startup, you may execute
28164 commands in any interpreter from the current interpreter using the appropriate
28165 command. If you are running the console interpreter, simply use the
28166 @code{interpreter-exec} command:
28169 interpreter-exec mi "-data-list-register-names"
28172 @sc{gdb/mi} has a similar command, although it is only available in versions of
28173 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
28176 @chapter @value{GDBN} Text User Interface
28178 @cindex Text User Interface
28181 * TUI Overview:: TUI overview
28182 * TUI Keys:: TUI key bindings
28183 * TUI Single Key Mode:: TUI single key mode
28184 * TUI Commands:: TUI-specific commands
28185 * TUI Configuration:: TUI configuration variables
28188 The @value{GDBN} Text User Interface (TUI) is a terminal
28189 interface which uses the @code{curses} library to show the source
28190 file, the assembly output, the program registers and @value{GDBN}
28191 commands in separate text windows. The TUI mode is supported only
28192 on platforms where a suitable version of the @code{curses} library
28195 The TUI mode is enabled by default when you invoke @value{GDBN} as
28196 @samp{@value{GDBP} -tui}.
28197 You can also switch in and out of TUI mode while @value{GDBN} runs by
28198 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
28199 @xref{TUI Keys, ,TUI Key Bindings}.
28202 @section TUI Overview
28204 In TUI mode, @value{GDBN} can display several text windows:
28208 This window is the @value{GDBN} command window with the @value{GDBN}
28209 prompt and the @value{GDBN} output. The @value{GDBN} input is still
28210 managed using readline.
28213 The source window shows the source file of the program. The current
28214 line and active breakpoints are displayed in this window.
28217 The assembly window shows the disassembly output of the program.
28220 This window shows the processor registers. Registers are highlighted
28221 when their values change.
28224 The source and assembly windows show the current program position
28225 by highlighting the current line and marking it with a @samp{>} marker.
28226 Breakpoints are indicated with two markers. The first marker
28227 indicates the breakpoint type:
28231 Breakpoint which was hit at least once.
28234 Breakpoint which was never hit.
28237 Hardware breakpoint which was hit at least once.
28240 Hardware breakpoint which was never hit.
28243 The second marker indicates whether the breakpoint is enabled or not:
28247 Breakpoint is enabled.
28250 Breakpoint is disabled.
28253 The source, assembly and register windows are updated when the current
28254 thread changes, when the frame changes, or when the program counter
28257 These windows are not all visible at the same time. The command
28258 window is always visible. The others can be arranged in several
28269 source and assembly,
28272 source and registers, or
28275 assembly and registers.
28278 A status line above the command window shows the following information:
28282 Indicates the current @value{GDBN} target.
28283 (@pxref{Targets, ,Specifying a Debugging Target}).
28286 Gives the current process or thread number.
28287 When no process is being debugged, this field is set to @code{No process}.
28290 Gives the current function name for the selected frame.
28291 The name is demangled if demangling is turned on (@pxref{Print Settings}).
28292 When there is no symbol corresponding to the current program counter,
28293 the string @code{??} is displayed.
28296 Indicates the current line number for the selected frame.
28297 When the current line number is not known, the string @code{??} is displayed.
28300 Indicates the current program counter address.
28304 @section TUI Key Bindings
28305 @cindex TUI key bindings
28307 The TUI installs several key bindings in the readline keymaps
28308 @ifset SYSTEM_READLINE
28309 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
28311 @ifclear SYSTEM_READLINE
28312 (@pxref{Command Line Editing}).
28314 The following key bindings are installed for both TUI mode and the
28315 @value{GDBN} standard mode.
28324 Enter or leave the TUI mode. When leaving the TUI mode,
28325 the curses window management stops and @value{GDBN} operates using
28326 its standard mode, writing on the terminal directly. When reentering
28327 the TUI mode, control is given back to the curses windows.
28328 The screen is then refreshed.
28332 Use a TUI layout with only one window. The layout will
28333 either be @samp{source} or @samp{assembly}. When the TUI mode
28334 is not active, it will switch to the TUI mode.
28336 Think of this key binding as the Emacs @kbd{C-x 1} binding.
28340 Use a TUI layout with at least two windows. When the current
28341 layout already has two windows, the next layout with two windows is used.
28342 When a new layout is chosen, one window will always be common to the
28343 previous layout and the new one.
28345 Think of it as the Emacs @kbd{C-x 2} binding.
28349 Change the active window. The TUI associates several key bindings
28350 (like scrolling and arrow keys) with the active window. This command
28351 gives the focus to the next TUI window.
28353 Think of it as the Emacs @kbd{C-x o} binding.
28357 Switch in and out of the TUI SingleKey mode that binds single
28358 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
28361 The following key bindings only work in the TUI mode:
28366 Scroll the active window one page up.
28370 Scroll the active window one page down.
28374 Scroll the active window one line up.
28378 Scroll the active window one line down.
28382 Scroll the active window one column left.
28386 Scroll the active window one column right.
28390 Refresh the screen.
28393 Because the arrow keys scroll the active window in the TUI mode, they
28394 are not available for their normal use by readline unless the command
28395 window has the focus. When another window is active, you must use
28396 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28397 and @kbd{C-f} to control the command window.
28399 @node TUI Single Key Mode
28400 @section TUI Single Key Mode
28401 @cindex TUI single key mode
28403 The TUI also provides a @dfn{SingleKey} mode, which binds several
28404 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28405 switch into this mode, where the following key bindings are used:
28408 @kindex c @r{(SingleKey TUI key)}
28412 @kindex d @r{(SingleKey TUI key)}
28416 @kindex f @r{(SingleKey TUI key)}
28420 @kindex n @r{(SingleKey TUI key)}
28424 @kindex q @r{(SingleKey TUI key)}
28426 exit the SingleKey mode.
28428 @kindex r @r{(SingleKey TUI key)}
28432 @kindex s @r{(SingleKey TUI key)}
28436 @kindex u @r{(SingleKey TUI key)}
28440 @kindex v @r{(SingleKey TUI key)}
28444 @kindex w @r{(SingleKey TUI key)}
28449 Other keys temporarily switch to the @value{GDBN} command prompt.
28450 The key that was pressed is inserted in the editing buffer so that
28451 it is possible to type most @value{GDBN} commands without interaction
28452 with the TUI SingleKey mode. Once the command is entered the TUI
28453 SingleKey mode is restored. The only way to permanently leave
28454 this mode is by typing @kbd{q} or @kbd{C-x s}.
28458 @section TUI-specific Commands
28459 @cindex TUI commands
28461 The TUI has specific commands to control the text windows.
28462 These commands are always available, even when @value{GDBN} is not in
28463 the TUI mode. When @value{GDBN} is in the standard mode, most
28464 of these commands will automatically switch to the TUI mode.
28466 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28467 terminal, or @value{GDBN} has been started with the machine interface
28468 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28469 these commands will fail with an error, because it would not be
28470 possible or desirable to enable curses window management.
28475 List and give the size of all displayed windows.
28479 Display the next layout.
28482 Display the previous layout.
28485 Display the source window only.
28488 Display the assembly window only.
28491 Display the source and assembly window.
28494 Display the register window together with the source or assembly window.
28498 Make the next window active for scrolling.
28501 Make the previous window active for scrolling.
28504 Make the source window active for scrolling.
28507 Make the assembly window active for scrolling.
28510 Make the register window active for scrolling.
28513 Make the command window active for scrolling.
28517 Refresh the screen. This is similar to typing @kbd{C-L}.
28519 @item tui reg float
28521 Show the floating point registers in the register window.
28523 @item tui reg general
28524 Show the general registers in the register window.
28527 Show the next register group. The list of register groups as well as
28528 their order is target specific. The predefined register groups are the
28529 following: @code{general}, @code{float}, @code{system}, @code{vector},
28530 @code{all}, @code{save}, @code{restore}.
28532 @item tui reg system
28533 Show the system registers in the register window.
28537 Update the source window and the current execution point.
28539 @item winheight @var{name} +@var{count}
28540 @itemx winheight @var{name} -@var{count}
28542 Change the height of the window @var{name} by @var{count}
28543 lines. Positive counts increase the height, while negative counts
28546 @item tabset @var{nchars}
28548 Set the width of tab stops to be @var{nchars} characters.
28551 @node TUI Configuration
28552 @section TUI Configuration Variables
28553 @cindex TUI configuration variables
28555 Several configuration variables control the appearance of TUI windows.
28558 @item set tui border-kind @var{kind}
28559 @kindex set tui border-kind
28560 Select the border appearance for the source, assembly and register windows.
28561 The possible values are the following:
28564 Use a space character to draw the border.
28567 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28570 Use the Alternate Character Set to draw the border. The border is
28571 drawn using character line graphics if the terminal supports them.
28574 @item set tui border-mode @var{mode}
28575 @kindex set tui border-mode
28576 @itemx set tui active-border-mode @var{mode}
28577 @kindex set tui active-border-mode
28578 Select the display attributes for the borders of the inactive windows
28579 or the active window. The @var{mode} can be one of the following:
28582 Use normal attributes to display the border.
28588 Use reverse video mode.
28591 Use half bright mode.
28593 @item half-standout
28594 Use half bright and standout mode.
28597 Use extra bright or bold mode.
28599 @item bold-standout
28600 Use extra bright or bold and standout mode.
28605 @chapter Using @value{GDBN} under @sc{gnu} Emacs
28608 @cindex @sc{gnu} Emacs
28609 A special interface allows you to use @sc{gnu} Emacs to view (and
28610 edit) the source files for the program you are debugging with
28613 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
28614 executable file you want to debug as an argument. This command starts
28615 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
28616 created Emacs buffer.
28617 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
28619 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
28624 All ``terminal'' input and output goes through an Emacs buffer, called
28627 This applies both to @value{GDBN} commands and their output, and to the input
28628 and output done by the program you are debugging.
28630 This is useful because it means that you can copy the text of previous
28631 commands and input them again; you can even use parts of the output
28634 All the facilities of Emacs' Shell mode are available for interacting
28635 with your program. In particular, you can send signals the usual
28636 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
28640 @value{GDBN} displays source code through Emacs.
28642 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
28643 source file for that frame and puts an arrow (@samp{=>}) at the
28644 left margin of the current line. Emacs uses a separate buffer for
28645 source display, and splits the screen to show both your @value{GDBN} session
28648 Explicit @value{GDBN} @code{list} or search commands still produce output as
28649 usual, but you probably have no reason to use them from Emacs.
28652 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
28653 a graphical mode, enabled by default, which provides further buffers
28654 that can control the execution and describe the state of your program.
28655 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
28657 If you specify an absolute file name when prompted for the @kbd{M-x
28658 gdb} argument, then Emacs sets your current working directory to where
28659 your program resides. If you only specify the file name, then Emacs
28660 sets your current working directory to the directory associated
28661 with the previous buffer. In this case, @value{GDBN} may find your
28662 program by searching your environment's @code{PATH} variable, but on
28663 some operating systems it might not find the source. So, although the
28664 @value{GDBN} input and output session proceeds normally, the auxiliary
28665 buffer does not display the current source and line of execution.
28667 The initial working directory of @value{GDBN} is printed on the top
28668 line of the GUD buffer and this serves as a default for the commands
28669 that specify files for @value{GDBN} to operate on. @xref{Files,
28670 ,Commands to Specify Files}.
28672 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
28673 need to call @value{GDBN} by a different name (for example, if you
28674 keep several configurations around, with different names) you can
28675 customize the Emacs variable @code{gud-gdb-command-name} to run the
28678 In the GUD buffer, you can use these special Emacs commands in
28679 addition to the standard Shell mode commands:
28683 Describe the features of Emacs' GUD Mode.
28686 Execute to another source line, like the @value{GDBN} @code{step} command; also
28687 update the display window to show the current file and location.
28690 Execute to next source line in this function, skipping all function
28691 calls, like the @value{GDBN} @code{next} command. Then update the display window
28692 to show the current file and location.
28695 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
28696 display window accordingly.
28699 Execute until exit from the selected stack frame, like the @value{GDBN}
28700 @code{finish} command.
28703 Continue execution of your program, like the @value{GDBN} @code{continue}
28707 Go up the number of frames indicated by the numeric argument
28708 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
28709 like the @value{GDBN} @code{up} command.
28712 Go down the number of frames indicated by the numeric argument, like the
28713 @value{GDBN} @code{down} command.
28716 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
28717 tells @value{GDBN} to set a breakpoint on the source line point is on.
28719 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
28720 separate frame which shows a backtrace when the GUD buffer is current.
28721 Move point to any frame in the stack and type @key{RET} to make it
28722 become the current frame and display the associated source in the
28723 source buffer. Alternatively, click @kbd{Mouse-2} to make the
28724 selected frame become the current one. In graphical mode, the
28725 speedbar displays watch expressions.
28727 If you accidentally delete the source-display buffer, an easy way to get
28728 it back is to type the command @code{f} in the @value{GDBN} buffer, to
28729 request a frame display; when you run under Emacs, this recreates
28730 the source buffer if necessary to show you the context of the current
28733 The source files displayed in Emacs are in ordinary Emacs buffers
28734 which are visiting the source files in the usual way. You can edit
28735 the files with these buffers if you wish; but keep in mind that @value{GDBN}
28736 communicates with Emacs in terms of line numbers. If you add or
28737 delete lines from the text, the line numbers that @value{GDBN} knows cease
28738 to correspond properly with the code.
28740 A more detailed description of Emacs' interaction with @value{GDBN} is
28741 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
28745 @chapter The @sc{gdb/mi} Interface
28747 @unnumberedsec Function and Purpose
28749 @cindex @sc{gdb/mi}, its purpose
28750 @sc{gdb/mi} is a line based machine oriented text interface to
28751 @value{GDBN} and is activated by specifying using the
28752 @option{--interpreter} command line option (@pxref{Mode Options}). It
28753 is specifically intended to support the development of systems which
28754 use the debugger as just one small component of a larger system.
28756 This chapter is a specification of the @sc{gdb/mi} interface. It is written
28757 in the form of a reference manual.
28759 Note that @sc{gdb/mi} is still under construction, so some of the
28760 features described below are incomplete and subject to change
28761 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
28763 @unnumberedsec Notation and Terminology
28765 @cindex notational conventions, for @sc{gdb/mi}
28766 This chapter uses the following notation:
28770 @code{|} separates two alternatives.
28773 @code{[ @var{something} ]} indicates that @var{something} is optional:
28774 it may or may not be given.
28777 @code{( @var{group} )*} means that @var{group} inside the parentheses
28778 may repeat zero or more times.
28781 @code{( @var{group} )+} means that @var{group} inside the parentheses
28782 may repeat one or more times.
28785 @code{"@var{string}"} means a literal @var{string}.
28789 @heading Dependencies
28793 * GDB/MI General Design::
28794 * GDB/MI Command Syntax::
28795 * GDB/MI Compatibility with CLI::
28796 * GDB/MI Development and Front Ends::
28797 * GDB/MI Output Records::
28798 * GDB/MI Simple Examples::
28799 * GDB/MI Command Description Format::
28800 * GDB/MI Breakpoint Commands::
28801 * GDB/MI Catchpoint Commands::
28802 * GDB/MI Program Context::
28803 * GDB/MI Thread Commands::
28804 * GDB/MI Ada Tasking Commands::
28805 * GDB/MI Program Execution::
28806 * GDB/MI Stack Manipulation::
28807 * GDB/MI Variable Objects::
28808 * GDB/MI Data Manipulation::
28809 * GDB/MI Tracepoint Commands::
28810 * GDB/MI Symbol Query::
28811 * GDB/MI File Commands::
28813 * GDB/MI Kod Commands::
28814 * GDB/MI Memory Overlay Commands::
28815 * GDB/MI Signal Handling Commands::
28817 * GDB/MI Target Manipulation::
28818 * GDB/MI File Transfer Commands::
28819 * GDB/MI Ada Exceptions Commands::
28820 * GDB/MI Miscellaneous Commands::
28823 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28824 @node GDB/MI General Design
28825 @section @sc{gdb/mi} General Design
28826 @cindex GDB/MI General Design
28828 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
28829 parts---commands sent to @value{GDBN}, responses to those commands
28830 and notifications. Each command results in exactly one response,
28831 indicating either successful completion of the command, or an error.
28832 For the commands that do not resume the target, the response contains the
28833 requested information. For the commands that resume the target, the
28834 response only indicates whether the target was successfully resumed.
28835 Notifications is the mechanism for reporting changes in the state of the
28836 target, or in @value{GDBN} state, that cannot conveniently be associated with
28837 a command and reported as part of that command response.
28839 The important examples of notifications are:
28843 Exec notifications. These are used to report changes in
28844 target state---when a target is resumed, or stopped. It would not
28845 be feasible to include this information in response of resuming
28846 commands, because one resume commands can result in multiple events in
28847 different threads. Also, quite some time may pass before any event
28848 happens in the target, while a frontend needs to know whether the resuming
28849 command itself was successfully executed.
28852 Console output, and status notifications. Console output
28853 notifications are used to report output of CLI commands, as well as
28854 diagnostics for other commands. Status notifications are used to
28855 report the progress of a long-running operation. Naturally, including
28856 this information in command response would mean no output is produced
28857 until the command is finished, which is undesirable.
28860 General notifications. Commands may have various side effects on
28861 the @value{GDBN} or target state beyond their official purpose. For example,
28862 a command may change the selected thread. Although such changes can
28863 be included in command response, using notification allows for more
28864 orthogonal frontend design.
28868 There's no guarantee that whenever an MI command reports an error,
28869 @value{GDBN} or the target are in any specific state, and especially,
28870 the state is not reverted to the state before the MI command was
28871 processed. Therefore, whenever an MI command results in an error,
28872 we recommend that the frontend refreshes all the information shown in
28873 the user interface.
28877 * Context management::
28878 * Asynchronous and non-stop modes::
28882 @node Context management
28883 @subsection Context management
28885 @subsubsection Threads and Frames
28887 In most cases when @value{GDBN} accesses the target, this access is
28888 done in context of a specific thread and frame (@pxref{Frames}).
28889 Often, even when accessing global data, the target requires that a thread
28890 be specified. The CLI interface maintains the selected thread and frame,
28891 and supplies them to target on each command. This is convenient,
28892 because a command line user would not want to specify that information
28893 explicitly on each command, and because user interacts with
28894 @value{GDBN} via a single terminal, so no confusion is possible as
28895 to what thread and frame are the current ones.
28897 In the case of MI, the concept of selected thread and frame is less
28898 useful. First, a frontend can easily remember this information
28899 itself. Second, a graphical frontend can have more than one window,
28900 each one used for debugging a different thread, and the frontend might
28901 want to access additional threads for internal purposes. This
28902 increases the risk that by relying on implicitly selected thread, the
28903 frontend may be operating on a wrong one. Therefore, each MI command
28904 should explicitly specify which thread and frame to operate on. To
28905 make it possible, each MI command accepts the @samp{--thread} and
28906 @samp{--frame} options, the value to each is @value{GDBN} identifier
28907 for thread and frame to operate on.
28909 Usually, each top-level window in a frontend allows the user to select
28910 a thread and a frame, and remembers the user selection for further
28911 operations. However, in some cases @value{GDBN} may suggest that the
28912 current thread be changed. For example, when stopping on a breakpoint
28913 it is reasonable to switch to the thread where breakpoint is hit. For
28914 another example, if the user issues the CLI @samp{thread} command via
28915 the frontend, it is desirable to change the frontend's selected thread to the
28916 one specified by user. @value{GDBN} communicates the suggestion to
28917 change current thread using the @samp{=thread-selected} notification.
28918 No such notification is available for the selected frame at the moment.
28920 Note that historically, MI shares the selected thread with CLI, so
28921 frontends used the @code{-thread-select} to execute commands in the
28922 right context. However, getting this to work right is cumbersome. The
28923 simplest way is for frontend to emit @code{-thread-select} command
28924 before every command. This doubles the number of commands that need
28925 to be sent. The alternative approach is to suppress @code{-thread-select}
28926 if the selected thread in @value{GDBN} is supposed to be identical to the
28927 thread the frontend wants to operate on. However, getting this
28928 optimization right can be tricky. In particular, if the frontend
28929 sends several commands to @value{GDBN}, and one of the commands changes the
28930 selected thread, then the behaviour of subsequent commands will
28931 change. So, a frontend should either wait for response from such
28932 problematic commands, or explicitly add @code{-thread-select} for
28933 all subsequent commands. No frontend is known to do this exactly
28934 right, so it is suggested to just always pass the @samp{--thread} and
28935 @samp{--frame} options.
28937 @subsubsection Language
28939 The execution of several commands depends on which language is selected.
28940 By default, the current language (@pxref{show language}) is used.
28941 But for commands known to be language-sensitive, it is recommended
28942 to use the @samp{--language} option. This option takes one argument,
28943 which is the name of the language to use while executing the command.
28947 -data-evaluate-expression --language c "sizeof (void*)"
28952 The valid language names are the same names accepted by the
28953 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
28954 @samp{local} or @samp{unknown}.
28956 @node Asynchronous and non-stop modes
28957 @subsection Asynchronous command execution and non-stop mode
28959 On some targets, @value{GDBN} is capable of processing MI commands
28960 even while the target is running. This is called @dfn{asynchronous
28961 command execution} (@pxref{Background Execution}). The frontend may
28962 specify a preferrence for asynchronous execution using the
28963 @code{-gdb-set target-async 1} command, which should be emitted before
28964 either running the executable or attaching to the target. After the
28965 frontend has started the executable or attached to the target, it can
28966 find if asynchronous execution is enabled using the
28967 @code{-list-target-features} command.
28969 Even if @value{GDBN} can accept a command while target is running,
28970 many commands that access the target do not work when the target is
28971 running. Therefore, asynchronous command execution is most useful
28972 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
28973 it is possible to examine the state of one thread, while other threads
28976 When a given thread is running, MI commands that try to access the
28977 target in the context of that thread may not work, or may work only on
28978 some targets. In particular, commands that try to operate on thread's
28979 stack will not work, on any target. Commands that read memory, or
28980 modify breakpoints, may work or not work, depending on the target. Note
28981 that even commands that operate on global state, such as @code{print},
28982 @code{set}, and breakpoint commands, still access the target in the
28983 context of a specific thread, so frontend should try to find a
28984 stopped thread and perform the operation on that thread (using the
28985 @samp{--thread} option).
28987 Which commands will work in the context of a running thread is
28988 highly target dependent. However, the two commands
28989 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
28990 to find the state of a thread, will always work.
28992 @node Thread groups
28993 @subsection Thread groups
28994 @value{GDBN} may be used to debug several processes at the same time.
28995 On some platfroms, @value{GDBN} may support debugging of several
28996 hardware systems, each one having several cores with several different
28997 processes running on each core. This section describes the MI
28998 mechanism to support such debugging scenarios.
29000 The key observation is that regardless of the structure of the
29001 target, MI can have a global list of threads, because most commands that
29002 accept the @samp{--thread} option do not need to know what process that
29003 thread belongs to. Therefore, it is not necessary to introduce
29004 neither additional @samp{--process} option, nor an notion of the
29005 current process in the MI interface. The only strictly new feature
29006 that is required is the ability to find how the threads are grouped
29009 To allow the user to discover such grouping, and to support arbitrary
29010 hierarchy of machines/cores/processes, MI introduces the concept of a
29011 @dfn{thread group}. Thread group is a collection of threads and other
29012 thread groups. A thread group always has a string identifier, a type,
29013 and may have additional attributes specific to the type. A new
29014 command, @code{-list-thread-groups}, returns the list of top-level
29015 thread groups, which correspond to processes that @value{GDBN} is
29016 debugging at the moment. By passing an identifier of a thread group
29017 to the @code{-list-thread-groups} command, it is possible to obtain
29018 the members of specific thread group.
29020 To allow the user to easily discover processes, and other objects, he
29021 wishes to debug, a concept of @dfn{available thread group} is
29022 introduced. Available thread group is an thread group that
29023 @value{GDBN} is not debugging, but that can be attached to, using the
29024 @code{-target-attach} command. The list of available top-level thread
29025 groups can be obtained using @samp{-list-thread-groups --available}.
29026 In general, the content of a thread group may be only retrieved only
29027 after attaching to that thread group.
29029 Thread groups are related to inferiors (@pxref{Inferiors and
29030 Programs}). Each inferior corresponds to a thread group of a special
29031 type @samp{process}, and some additional operations are permitted on
29032 such thread groups.
29034 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29035 @node GDB/MI Command Syntax
29036 @section @sc{gdb/mi} Command Syntax
29039 * GDB/MI Input Syntax::
29040 * GDB/MI Output Syntax::
29043 @node GDB/MI Input Syntax
29044 @subsection @sc{gdb/mi} Input Syntax
29046 @cindex input syntax for @sc{gdb/mi}
29047 @cindex @sc{gdb/mi}, input syntax
29049 @item @var{command} @expansion{}
29050 @code{@var{cli-command} | @var{mi-command}}
29052 @item @var{cli-command} @expansion{}
29053 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
29054 @var{cli-command} is any existing @value{GDBN} CLI command.
29056 @item @var{mi-command} @expansion{}
29057 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
29058 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
29060 @item @var{token} @expansion{}
29061 "any sequence of digits"
29063 @item @var{option} @expansion{}
29064 @code{"-" @var{parameter} [ " " @var{parameter} ]}
29066 @item @var{parameter} @expansion{}
29067 @code{@var{non-blank-sequence} | @var{c-string}}
29069 @item @var{operation} @expansion{}
29070 @emph{any of the operations described in this chapter}
29072 @item @var{non-blank-sequence} @expansion{}
29073 @emph{anything, provided it doesn't contain special characters such as
29074 "-", @var{nl}, """ and of course " "}
29076 @item @var{c-string} @expansion{}
29077 @code{""" @var{seven-bit-iso-c-string-content} """}
29079 @item @var{nl} @expansion{}
29088 The CLI commands are still handled by the @sc{mi} interpreter; their
29089 output is described below.
29092 The @code{@var{token}}, when present, is passed back when the command
29096 Some @sc{mi} commands accept optional arguments as part of the parameter
29097 list. Each option is identified by a leading @samp{-} (dash) and may be
29098 followed by an optional argument parameter. Options occur first in the
29099 parameter list and can be delimited from normal parameters using
29100 @samp{--} (this is useful when some parameters begin with a dash).
29107 We want easy access to the existing CLI syntax (for debugging).
29110 We want it to be easy to spot a @sc{mi} operation.
29113 @node GDB/MI Output Syntax
29114 @subsection @sc{gdb/mi} Output Syntax
29116 @cindex output syntax of @sc{gdb/mi}
29117 @cindex @sc{gdb/mi}, output syntax
29118 The output from @sc{gdb/mi} consists of zero or more out-of-band records
29119 followed, optionally, by a single result record. This result record
29120 is for the most recent command. The sequence of output records is
29121 terminated by @samp{(gdb)}.
29123 If an input command was prefixed with a @code{@var{token}} then the
29124 corresponding output for that command will also be prefixed by that same
29128 @item @var{output} @expansion{}
29129 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
29131 @item @var{result-record} @expansion{}
29132 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
29134 @item @var{out-of-band-record} @expansion{}
29135 @code{@var{async-record} | @var{stream-record}}
29137 @item @var{async-record} @expansion{}
29138 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
29140 @item @var{exec-async-output} @expansion{}
29141 @code{[ @var{token} ] "*" @var{async-output}}
29143 @item @var{status-async-output} @expansion{}
29144 @code{[ @var{token} ] "+" @var{async-output}}
29146 @item @var{notify-async-output} @expansion{}
29147 @code{[ @var{token} ] "=" @var{async-output}}
29149 @item @var{async-output} @expansion{}
29150 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
29152 @item @var{result-class} @expansion{}
29153 @code{"done" | "running" | "connected" | "error" | "exit"}
29155 @item @var{async-class} @expansion{}
29156 @code{"stopped" | @var{others}} (where @var{others} will be added
29157 depending on the needs---this is still in development).
29159 @item @var{result} @expansion{}
29160 @code{ @var{variable} "=" @var{value}}
29162 @item @var{variable} @expansion{}
29163 @code{ @var{string} }
29165 @item @var{value} @expansion{}
29166 @code{ @var{const} | @var{tuple} | @var{list} }
29168 @item @var{const} @expansion{}
29169 @code{@var{c-string}}
29171 @item @var{tuple} @expansion{}
29172 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
29174 @item @var{list} @expansion{}
29175 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
29176 @var{result} ( "," @var{result} )* "]" }
29178 @item @var{stream-record} @expansion{}
29179 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
29181 @item @var{console-stream-output} @expansion{}
29182 @code{"~" @var{c-string}}
29184 @item @var{target-stream-output} @expansion{}
29185 @code{"@@" @var{c-string}}
29187 @item @var{log-stream-output} @expansion{}
29188 @code{"&" @var{c-string}}
29190 @item @var{nl} @expansion{}
29193 @item @var{token} @expansion{}
29194 @emph{any sequence of digits}.
29202 All output sequences end in a single line containing a period.
29205 The @code{@var{token}} is from the corresponding request. Note that
29206 for all async output, while the token is allowed by the grammar and
29207 may be output by future versions of @value{GDBN} for select async
29208 output messages, it is generally omitted. Frontends should treat
29209 all async output as reporting general changes in the state of the
29210 target and there should be no need to associate async output to any
29214 @cindex status output in @sc{gdb/mi}
29215 @var{status-async-output} contains on-going status information about the
29216 progress of a slow operation. It can be discarded. All status output is
29217 prefixed by @samp{+}.
29220 @cindex async output in @sc{gdb/mi}
29221 @var{exec-async-output} contains asynchronous state change on the target
29222 (stopped, started, disappeared). All async output is prefixed by
29226 @cindex notify output in @sc{gdb/mi}
29227 @var{notify-async-output} contains supplementary information that the
29228 client should handle (e.g., a new breakpoint information). All notify
29229 output is prefixed by @samp{=}.
29232 @cindex console output in @sc{gdb/mi}
29233 @var{console-stream-output} is output that should be displayed as is in the
29234 console. It is the textual response to a CLI command. All the console
29235 output is prefixed by @samp{~}.
29238 @cindex target output in @sc{gdb/mi}
29239 @var{target-stream-output} is the output produced by the target program.
29240 All the target output is prefixed by @samp{@@}.
29243 @cindex log output in @sc{gdb/mi}
29244 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
29245 instance messages that should be displayed as part of an error log. All
29246 the log output is prefixed by @samp{&}.
29249 @cindex list output in @sc{gdb/mi}
29250 New @sc{gdb/mi} commands should only output @var{lists} containing
29256 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
29257 details about the various output records.
29259 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29260 @node GDB/MI Compatibility with CLI
29261 @section @sc{gdb/mi} Compatibility with CLI
29263 @cindex compatibility, @sc{gdb/mi} and CLI
29264 @cindex @sc{gdb/mi}, compatibility with CLI
29266 For the developers convenience CLI commands can be entered directly,
29267 but there may be some unexpected behaviour. For example, commands
29268 that query the user will behave as if the user replied yes, breakpoint
29269 command lists are not executed and some CLI commands, such as
29270 @code{if}, @code{when} and @code{define}, prompt for further input with
29271 @samp{>}, which is not valid MI output.
29273 This feature may be removed at some stage in the future and it is
29274 recommended that front ends use the @code{-interpreter-exec} command
29275 (@pxref{-interpreter-exec}).
29277 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29278 @node GDB/MI Development and Front Ends
29279 @section @sc{gdb/mi} Development and Front Ends
29280 @cindex @sc{gdb/mi} development
29282 The application which takes the MI output and presents the state of the
29283 program being debugged to the user is called a @dfn{front end}.
29285 Although @sc{gdb/mi} is still incomplete, it is currently being used
29286 by a variety of front ends to @value{GDBN}. This makes it difficult
29287 to introduce new functionality without breaking existing usage. This
29288 section tries to minimize the problems by describing how the protocol
29291 Some changes in MI need not break a carefully designed front end, and
29292 for these the MI version will remain unchanged. The following is a
29293 list of changes that may occur within one level, so front ends should
29294 parse MI output in a way that can handle them:
29298 New MI commands may be added.
29301 New fields may be added to the output of any MI command.
29304 The range of values for fields with specified values, e.g.,
29305 @code{in_scope} (@pxref{-var-update}) may be extended.
29307 @c The format of field's content e.g type prefix, may change so parse it
29308 @c at your own risk. Yes, in general?
29310 @c The order of fields may change? Shouldn't really matter but it might
29311 @c resolve inconsistencies.
29314 If the changes are likely to break front ends, the MI version level
29315 will be increased by one. This will allow the front end to parse the
29316 output according to the MI version. Apart from mi0, new versions of
29317 @value{GDBN} will not support old versions of MI and it will be the
29318 responsibility of the front end to work with the new one.
29320 @c Starting with mi3, add a new command -mi-version that prints the MI
29323 The best way to avoid unexpected changes in MI that might break your front
29324 end is to make your project known to @value{GDBN} developers and
29325 follow development on @email{gdb@@sourceware.org} and
29326 @email{gdb-patches@@sourceware.org}.
29327 @cindex mailing lists
29329 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29330 @node GDB/MI Output Records
29331 @section @sc{gdb/mi} Output Records
29334 * GDB/MI Result Records::
29335 * GDB/MI Stream Records::
29336 * GDB/MI Async Records::
29337 * GDB/MI Breakpoint Information::
29338 * GDB/MI Frame Information::
29339 * GDB/MI Thread Information::
29340 * GDB/MI Ada Exception Information::
29343 @node GDB/MI Result Records
29344 @subsection @sc{gdb/mi} Result Records
29346 @cindex result records in @sc{gdb/mi}
29347 @cindex @sc{gdb/mi}, result records
29348 In addition to a number of out-of-band notifications, the response to a
29349 @sc{gdb/mi} command includes one of the following result indications:
29353 @item "^done" [ "," @var{results} ]
29354 The synchronous operation was successful, @code{@var{results}} are the return
29359 This result record is equivalent to @samp{^done}. Historically, it
29360 was output instead of @samp{^done} if the command has resumed the
29361 target. This behaviour is maintained for backward compatibility, but
29362 all frontends should treat @samp{^done} and @samp{^running}
29363 identically and rely on the @samp{*running} output record to determine
29364 which threads are resumed.
29368 @value{GDBN} has connected to a remote target.
29370 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
29372 The operation failed. The @code{msg=@var{c-string}} variable contains
29373 the corresponding error message.
29375 If present, the @code{code=@var{c-string}} variable provides an error
29376 code on which consumers can rely on to detect the corresponding
29377 error condition. At present, only one error code is defined:
29380 @item "undefined-command"
29381 Indicates that the command causing the error does not exist.
29386 @value{GDBN} has terminated.
29390 @node GDB/MI Stream Records
29391 @subsection @sc{gdb/mi} Stream Records
29393 @cindex @sc{gdb/mi}, stream records
29394 @cindex stream records in @sc{gdb/mi}
29395 @value{GDBN} internally maintains a number of output streams: the console, the
29396 target, and the log. The output intended for each of these streams is
29397 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
29399 Each stream record begins with a unique @dfn{prefix character} which
29400 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
29401 Syntax}). In addition to the prefix, each stream record contains a
29402 @code{@var{string-output}}. This is either raw text (with an implicit new
29403 line) or a quoted C string (which does not contain an implicit newline).
29406 @item "~" @var{string-output}
29407 The console output stream contains text that should be displayed in the
29408 CLI console window. It contains the textual responses to CLI commands.
29410 @item "@@" @var{string-output}
29411 The target output stream contains any textual output from the running
29412 target. This is only present when GDB's event loop is truly
29413 asynchronous, which is currently only the case for remote targets.
29415 @item "&" @var{string-output}
29416 The log stream contains debugging messages being produced by @value{GDBN}'s
29420 @node GDB/MI Async Records
29421 @subsection @sc{gdb/mi} Async Records
29423 @cindex async records in @sc{gdb/mi}
29424 @cindex @sc{gdb/mi}, async records
29425 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
29426 additional changes that have occurred. Those changes can either be a
29427 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
29428 target activity (e.g., target stopped).
29430 The following is the list of possible async records:
29434 @item *running,thread-id="@var{thread}"
29435 The target is now running. The @var{thread} field tells which
29436 specific thread is now running, and can be @samp{all} if all threads
29437 are running. The frontend should assume that no interaction with a
29438 running thread is possible after this notification is produced.
29439 The frontend should not assume that this notification is output
29440 only once for any command. @value{GDBN} may emit this notification
29441 several times, either for different threads, because it cannot resume
29442 all threads together, or even for a single thread, if the thread must
29443 be stepped though some code before letting it run freely.
29445 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
29446 The target has stopped. The @var{reason} field can have one of the
29450 @item breakpoint-hit
29451 A breakpoint was reached.
29452 @item watchpoint-trigger
29453 A watchpoint was triggered.
29454 @item read-watchpoint-trigger
29455 A read watchpoint was triggered.
29456 @item access-watchpoint-trigger
29457 An access watchpoint was triggered.
29458 @item function-finished
29459 An -exec-finish or similar CLI command was accomplished.
29460 @item location-reached
29461 An -exec-until or similar CLI command was accomplished.
29462 @item watchpoint-scope
29463 A watchpoint has gone out of scope.
29464 @item end-stepping-range
29465 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
29466 similar CLI command was accomplished.
29467 @item exited-signalled
29468 The inferior exited because of a signal.
29470 The inferior exited.
29471 @item exited-normally
29472 The inferior exited normally.
29473 @item signal-received
29474 A signal was received by the inferior.
29476 The inferior has stopped due to a library being loaded or unloaded.
29477 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
29478 set or when a @code{catch load} or @code{catch unload} catchpoint is
29479 in use (@pxref{Set Catchpoints}).
29481 The inferior has forked. This is reported when @code{catch fork}
29482 (@pxref{Set Catchpoints}) has been used.
29484 The inferior has vforked. This is reported in when @code{catch vfork}
29485 (@pxref{Set Catchpoints}) has been used.
29486 @item syscall-entry
29487 The inferior entered a system call. This is reported when @code{catch
29488 syscall} (@pxref{Set Catchpoints}) has been used.
29489 @item syscall-entry
29490 The inferior returned from a system call. This is reported when
29491 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
29493 The inferior called @code{exec}. This is reported when @code{catch exec}
29494 (@pxref{Set Catchpoints}) has been used.
29497 The @var{id} field identifies the thread that directly caused the stop
29498 -- for example by hitting a breakpoint. Depending on whether all-stop
29499 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
29500 stop all threads, or only the thread that directly triggered the stop.
29501 If all threads are stopped, the @var{stopped} field will have the
29502 value of @code{"all"}. Otherwise, the value of the @var{stopped}
29503 field will be a list of thread identifiers. Presently, this list will
29504 always include a single thread, but frontend should be prepared to see
29505 several threads in the list. The @var{core} field reports the
29506 processor core on which the stop event has happened. This field may be absent
29507 if such information is not available.
29509 @item =thread-group-added,id="@var{id}"
29510 @itemx =thread-group-removed,id="@var{id}"
29511 A thread group was either added or removed. The @var{id} field
29512 contains the @value{GDBN} identifier of the thread group. When a thread
29513 group is added, it generally might not be associated with a running
29514 process. When a thread group is removed, its id becomes invalid and
29515 cannot be used in any way.
29517 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
29518 A thread group became associated with a running program,
29519 either because the program was just started or the thread group
29520 was attached to a program. The @var{id} field contains the
29521 @value{GDBN} identifier of the thread group. The @var{pid} field
29522 contains process identifier, specific to the operating system.
29524 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
29525 A thread group is no longer associated with a running program,
29526 either because the program has exited, or because it was detached
29527 from. The @var{id} field contains the @value{GDBN} identifier of the
29528 thread group. @var{code} is the exit code of the inferior; it exists
29529 only when the inferior exited with some code.
29531 @item =thread-created,id="@var{id}",group-id="@var{gid}"
29532 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
29533 A thread either was created, or has exited. The @var{id} field
29534 contains the @value{GDBN} identifier of the thread. The @var{gid}
29535 field identifies the thread group this thread belongs to.
29537 @item =thread-selected,id="@var{id}"
29538 Informs that the selected thread was changed as result of the last
29539 command. This notification is not emitted as result of @code{-thread-select}
29540 command but is emitted whenever an MI command that is not documented
29541 to change the selected thread actually changes it. In particular,
29542 invoking, directly or indirectly (via user-defined command), the CLI
29543 @code{thread} command, will generate this notification.
29545 We suggest that in response to this notification, front ends
29546 highlight the selected thread and cause subsequent commands to apply to
29549 @item =library-loaded,...
29550 Reports that a new library file was loaded by the program. This
29551 notification has 4 fields---@var{id}, @var{target-name},
29552 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
29553 opaque identifier of the library. For remote debugging case,
29554 @var{target-name} and @var{host-name} fields give the name of the
29555 library file on the target, and on the host respectively. For native
29556 debugging, both those fields have the same value. The
29557 @var{symbols-loaded} field is emitted only for backward compatibility
29558 and should not be relied on to convey any useful information. The
29559 @var{thread-group} field, if present, specifies the id of the thread
29560 group in whose context the library was loaded. If the field is
29561 absent, it means the library was loaded in the context of all present
29564 @item =library-unloaded,...
29565 Reports that a library was unloaded by the program. This notification
29566 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
29567 the same meaning as for the @code{=library-loaded} notification.
29568 The @var{thread-group} field, if present, specifies the id of the
29569 thread group in whose context the library was unloaded. If the field is
29570 absent, it means the library was unloaded in the context of all present
29573 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
29574 @itemx =traceframe-changed,end
29575 Reports that the trace frame was changed and its new number is
29576 @var{tfnum}. The number of the tracepoint associated with this trace
29577 frame is @var{tpnum}.
29579 @item =tsv-created,name=@var{name},initial=@var{initial}
29580 Reports that the new trace state variable @var{name} is created with
29581 initial value @var{initial}.
29583 @item =tsv-deleted,name=@var{name}
29584 @itemx =tsv-deleted
29585 Reports that the trace state variable @var{name} is deleted or all
29586 trace state variables are deleted.
29588 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
29589 Reports that the trace state variable @var{name} is modified with
29590 the initial value @var{initial}. The current value @var{current} of
29591 trace state variable is optional and is reported if the current
29592 value of trace state variable is known.
29594 @item =breakpoint-created,bkpt=@{...@}
29595 @itemx =breakpoint-modified,bkpt=@{...@}
29596 @itemx =breakpoint-deleted,id=@var{number}
29597 Reports that a breakpoint was created, modified, or deleted,
29598 respectively. Only user-visible breakpoints are reported to the MI
29601 The @var{bkpt} argument is of the same form as returned by the various
29602 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
29603 @var{number} is the ordinal number of the breakpoint.
29605 Note that if a breakpoint is emitted in the result record of a
29606 command, then it will not also be emitted in an async record.
29608 @item =record-started,thread-group="@var{id}"
29609 @itemx =record-stopped,thread-group="@var{id}"
29610 Execution log recording was either started or stopped on an
29611 inferior. The @var{id} is the @value{GDBN} identifier of the thread
29612 group corresponding to the affected inferior.
29614 @item =cmd-param-changed,param=@var{param},value=@var{value}
29615 Reports that a parameter of the command @code{set @var{param}} is
29616 changed to @var{value}. In the multi-word @code{set} command,
29617 the @var{param} is the whole parameter list to @code{set} command.
29618 For example, In command @code{set check type on}, @var{param}
29619 is @code{check type} and @var{value} is @code{on}.
29621 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
29622 Reports that bytes from @var{addr} to @var{data} + @var{len} were
29623 written in an inferior. The @var{id} is the identifier of the
29624 thread group corresponding to the affected inferior. The optional
29625 @code{type="code"} part is reported if the memory written to holds
29629 @node GDB/MI Breakpoint Information
29630 @subsection @sc{gdb/mi} Breakpoint Information
29632 When @value{GDBN} reports information about a breakpoint, a
29633 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
29638 The breakpoint number. For a breakpoint that represents one location
29639 of a multi-location breakpoint, this will be a dotted pair, like
29643 The type of the breakpoint. For ordinary breakpoints this will be
29644 @samp{breakpoint}, but many values are possible.
29647 If the type of the breakpoint is @samp{catchpoint}, then this
29648 indicates the exact type of catchpoint.
29651 This is the breakpoint disposition---either @samp{del}, meaning that
29652 the breakpoint will be deleted at the next stop, or @samp{keep},
29653 meaning that the breakpoint will not be deleted.
29656 This indicates whether the breakpoint is enabled, in which case the
29657 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29658 Note that this is not the same as the field @code{enable}.
29661 The address of the breakpoint. This may be a hexidecimal number,
29662 giving the address; or the string @samp{<PENDING>}, for a pending
29663 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
29664 multiple locations. This field will not be present if no address can
29665 be determined. For example, a watchpoint does not have an address.
29668 If known, the function in which the breakpoint appears.
29669 If not known, this field is not present.
29672 The name of the source file which contains this function, if known.
29673 If not known, this field is not present.
29676 The full file name of the source file which contains this function, if
29677 known. If not known, this field is not present.
29680 The line number at which this breakpoint appears, if known.
29681 If not known, this field is not present.
29684 If the source file is not known, this field may be provided. If
29685 provided, this holds the address of the breakpoint, possibly followed
29689 If this breakpoint is pending, this field is present and holds the
29690 text used to set the breakpoint, as entered by the user.
29693 Where this breakpoint's condition is evaluated, either @samp{host} or
29697 If this is a thread-specific breakpoint, then this identifies the
29698 thread in which the breakpoint can trigger.
29701 If this breakpoint is restricted to a particular Ada task, then this
29702 field will hold the task identifier.
29705 If the breakpoint is conditional, this is the condition expression.
29708 The ignore count of the breakpoint.
29711 The enable count of the breakpoint.
29713 @item traceframe-usage
29716 @item static-tracepoint-marker-string-id
29717 For a static tracepoint, the name of the static tracepoint marker.
29720 For a masked watchpoint, this is the mask.
29723 A tracepoint's pass count.
29725 @item original-location
29726 The location of the breakpoint as originally specified by the user.
29727 This field is optional.
29730 The number of times the breakpoint has been hit.
29733 This field is only given for tracepoints. This is either @samp{y},
29734 meaning that the tracepoint is installed, or @samp{n}, meaning that it
29738 Some extra data, the exact contents of which are type-dependent.
29742 For example, here is what the output of @code{-break-insert}
29743 (@pxref{GDB/MI Breakpoint Commands}) might be:
29746 -> -break-insert main
29747 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29748 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29749 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29754 @node GDB/MI Frame Information
29755 @subsection @sc{gdb/mi} Frame Information
29757 Response from many MI commands includes an information about stack
29758 frame. This information is a tuple that may have the following
29763 The level of the stack frame. The innermost frame has the level of
29764 zero. This field is always present.
29767 The name of the function corresponding to the frame. This field may
29768 be absent if @value{GDBN} is unable to determine the function name.
29771 The code address for the frame. This field is always present.
29774 The name of the source files that correspond to the frame's code
29775 address. This field may be absent.
29778 The source line corresponding to the frames' code address. This field
29782 The name of the binary file (either executable or shared library) the
29783 corresponds to the frame's code address. This field may be absent.
29787 @node GDB/MI Thread Information
29788 @subsection @sc{gdb/mi} Thread Information
29790 Whenever @value{GDBN} has to report an information about a thread, it
29791 uses a tuple with the following fields:
29795 The numeric id assigned to the thread by @value{GDBN}. This field is
29799 Target-specific string identifying the thread. This field is always present.
29802 Additional information about the thread provided by the target.
29803 It is supposed to be human-readable and not interpreted by the
29804 frontend. This field is optional.
29807 Either @samp{stopped} or @samp{running}, depending on whether the
29808 thread is presently running. This field is always present.
29811 The value of this field is an integer number of the processor core the
29812 thread was last seen on. This field is optional.
29815 @node GDB/MI Ada Exception Information
29816 @subsection @sc{gdb/mi} Ada Exception Information
29818 Whenever a @code{*stopped} record is emitted because the program
29819 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
29820 @value{GDBN} provides the name of the exception that was raised via
29821 the @code{exception-name} field.
29823 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29824 @node GDB/MI Simple Examples
29825 @section Simple Examples of @sc{gdb/mi} Interaction
29826 @cindex @sc{gdb/mi}, simple examples
29828 This subsection presents several simple examples of interaction using
29829 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
29830 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
29831 the output received from @sc{gdb/mi}.
29833 Note the line breaks shown in the examples are here only for
29834 readability, they don't appear in the real output.
29836 @subheading Setting a Breakpoint
29838 Setting a breakpoint generates synchronous output which contains detailed
29839 information of the breakpoint.
29842 -> -break-insert main
29843 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29844 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29845 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29850 @subheading Program Execution
29852 Program execution generates asynchronous records and MI gives the
29853 reason that execution stopped.
29859 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29860 frame=@{addr="0x08048564",func="main",
29861 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
29862 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
29867 <- *stopped,reason="exited-normally"
29871 @subheading Quitting @value{GDBN}
29873 Quitting @value{GDBN} just prints the result class @samp{^exit}.
29881 Please note that @samp{^exit} is printed immediately, but it might
29882 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
29883 performs necessary cleanups, including killing programs being debugged
29884 or disconnecting from debug hardware, so the frontend should wait till
29885 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
29886 fails to exit in reasonable time.
29888 @subheading A Bad Command
29890 Here's what happens if you pass a non-existent command:
29894 <- ^error,msg="Undefined MI command: rubbish"
29899 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29900 @node GDB/MI Command Description Format
29901 @section @sc{gdb/mi} Command Description Format
29903 The remaining sections describe blocks of commands. Each block of
29904 commands is laid out in a fashion similar to this section.
29906 @subheading Motivation
29908 The motivation for this collection of commands.
29910 @subheading Introduction
29912 A brief introduction to this collection of commands as a whole.
29914 @subheading Commands
29916 For each command in the block, the following is described:
29918 @subsubheading Synopsis
29921 -command @var{args}@dots{}
29924 @subsubheading Result
29926 @subsubheading @value{GDBN} Command
29928 The corresponding @value{GDBN} CLI command(s), if any.
29930 @subsubheading Example
29932 Example(s) formatted for readability. Some of the described commands have
29933 not been implemented yet and these are labeled N.A.@: (not available).
29936 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29937 @node GDB/MI Breakpoint Commands
29938 @section @sc{gdb/mi} Breakpoint Commands
29940 @cindex breakpoint commands for @sc{gdb/mi}
29941 @cindex @sc{gdb/mi}, breakpoint commands
29942 This section documents @sc{gdb/mi} commands for manipulating
29945 @subheading The @code{-break-after} Command
29946 @findex -break-after
29948 @subsubheading Synopsis
29951 -break-after @var{number} @var{count}
29954 The breakpoint number @var{number} is not in effect until it has been
29955 hit @var{count} times. To see how this is reflected in the output of
29956 the @samp{-break-list} command, see the description of the
29957 @samp{-break-list} command below.
29959 @subsubheading @value{GDBN} Command
29961 The corresponding @value{GDBN} command is @samp{ignore}.
29963 @subsubheading Example
29968 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29969 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29970 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29978 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29979 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29980 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29981 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29982 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29983 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29984 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29985 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29986 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29987 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
29992 @subheading The @code{-break-catch} Command
29993 @findex -break-catch
29996 @subheading The @code{-break-commands} Command
29997 @findex -break-commands
29999 @subsubheading Synopsis
30002 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
30005 Specifies the CLI commands that should be executed when breakpoint
30006 @var{number} is hit. The parameters @var{command1} to @var{commandN}
30007 are the commands. If no command is specified, any previously-set
30008 commands are cleared. @xref{Break Commands}. Typical use of this
30009 functionality is tracing a program, that is, printing of values of
30010 some variables whenever breakpoint is hit and then continuing.
30012 @subsubheading @value{GDBN} Command
30014 The corresponding @value{GDBN} command is @samp{commands}.
30016 @subsubheading Example
30021 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30022 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30023 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30026 -break-commands 1 "print v" "continue"
30031 @subheading The @code{-break-condition} Command
30032 @findex -break-condition
30034 @subsubheading Synopsis
30037 -break-condition @var{number} @var{expr}
30040 Breakpoint @var{number} will stop the program only if the condition in
30041 @var{expr} is true. The condition becomes part of the
30042 @samp{-break-list} output (see the description of the @samp{-break-list}
30045 @subsubheading @value{GDBN} Command
30047 The corresponding @value{GDBN} command is @samp{condition}.
30049 @subsubheading Example
30053 -break-condition 1 1
30057 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30058 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30059 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30060 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30061 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30062 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30063 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30064 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30065 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30066 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
30070 @subheading The @code{-break-delete} Command
30071 @findex -break-delete
30073 @subsubheading Synopsis
30076 -break-delete ( @var{breakpoint} )+
30079 Delete the breakpoint(s) whose number(s) are specified in the argument
30080 list. This is obviously reflected in the breakpoint list.
30082 @subsubheading @value{GDBN} Command
30084 The corresponding @value{GDBN} command is @samp{delete}.
30086 @subsubheading Example
30094 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30095 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30096 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30097 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30098 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30099 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30100 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30105 @subheading The @code{-break-disable} Command
30106 @findex -break-disable
30108 @subsubheading Synopsis
30111 -break-disable ( @var{breakpoint} )+
30114 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
30115 break list is now set to @samp{n} for the named @var{breakpoint}(s).
30117 @subsubheading @value{GDBN} Command
30119 The corresponding @value{GDBN} command is @samp{disable}.
30121 @subsubheading Example
30129 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30130 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30131 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30132 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30133 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30134 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30135 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30136 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
30137 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30138 line="5",thread-groups=["i1"],times="0"@}]@}
30142 @subheading The @code{-break-enable} Command
30143 @findex -break-enable
30145 @subsubheading Synopsis
30148 -break-enable ( @var{breakpoint} )+
30151 Enable (previously disabled) @var{breakpoint}(s).
30153 @subsubheading @value{GDBN} Command
30155 The corresponding @value{GDBN} command is @samp{enable}.
30157 @subsubheading Example
30165 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30166 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30167 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30168 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30169 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30170 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30171 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30172 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30173 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30174 line="5",thread-groups=["i1"],times="0"@}]@}
30178 @subheading The @code{-break-info} Command
30179 @findex -break-info
30181 @subsubheading Synopsis
30184 -break-info @var{breakpoint}
30188 Get information about a single breakpoint.
30190 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
30191 Information}, for details on the format of each breakpoint in the
30194 @subsubheading @value{GDBN} Command
30196 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
30198 @subsubheading Example
30201 @subheading The @code{-break-insert} Command
30202 @findex -break-insert
30204 @subsubheading Synopsis
30207 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
30208 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30209 [ -p @var{thread-id} ] [ @var{location} ]
30213 If specified, @var{location}, can be one of:
30220 @item filename:linenum
30221 @item filename:function
30225 The possible optional parameters of this command are:
30229 Insert a temporary breakpoint.
30231 Insert a hardware breakpoint.
30233 If @var{location} cannot be parsed (for example if it
30234 refers to unknown files or functions), create a pending
30235 breakpoint. Without this flag, @value{GDBN} will report
30236 an error, and won't create a breakpoint, if @var{location}
30239 Create a disabled breakpoint.
30241 Create a tracepoint. @xref{Tracepoints}. When this parameter
30242 is used together with @samp{-h}, a fast tracepoint is created.
30243 @item -c @var{condition}
30244 Make the breakpoint conditional on @var{condition}.
30245 @item -i @var{ignore-count}
30246 Initialize the @var{ignore-count}.
30247 @item -p @var{thread-id}
30248 Restrict the breakpoint to the specified @var{thread-id}.
30251 @subsubheading Result
30253 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30254 resulting breakpoint.
30256 Note: this format is open to change.
30257 @c An out-of-band breakpoint instead of part of the result?
30259 @subsubheading @value{GDBN} Command
30261 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
30262 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
30264 @subsubheading Example
30269 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
30270 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
30273 -break-insert -t foo
30274 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
30275 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
30279 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30280 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30281 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30282 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30283 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30284 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30285 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30286 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30287 addr="0x0001072c", func="main",file="recursive2.c",
30288 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
30290 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
30291 addr="0x00010774",func="foo",file="recursive2.c",
30292 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30295 @c -break-insert -r foo.*
30296 @c ~int foo(int, int);
30297 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
30298 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30303 @subheading The @code{-dprintf-insert} Command
30304 @findex -dprintf-insert
30306 @subsubheading Synopsis
30309 -dprintf-insert [ -t ] [ -f ] [ -d ]
30310 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30311 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
30316 If specified, @var{location}, can be one of:
30319 @item @var{function}
30322 @c @item @var{linenum}
30323 @item @var{filename}:@var{linenum}
30324 @item @var{filename}:function
30325 @item *@var{address}
30328 The possible optional parameters of this command are:
30332 Insert a temporary breakpoint.
30334 If @var{location} cannot be parsed (for example, if it
30335 refers to unknown files or functions), create a pending
30336 breakpoint. Without this flag, @value{GDBN} will report
30337 an error, and won't create a breakpoint, if @var{location}
30340 Create a disabled breakpoint.
30341 @item -c @var{condition}
30342 Make the breakpoint conditional on @var{condition}.
30343 @item -i @var{ignore-count}
30344 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
30345 to @var{ignore-count}.
30346 @item -p @var{thread-id}
30347 Restrict the breakpoint to the specified @var{thread-id}.
30350 @subsubheading Result
30352 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30353 resulting breakpoint.
30355 @c An out-of-band breakpoint instead of part of the result?
30357 @subsubheading @value{GDBN} Command
30359 The corresponding @value{GDBN} command is @samp{dprintf}.
30361 @subsubheading Example
30365 4-dprintf-insert foo "At foo entry\n"
30366 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
30367 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
30368 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
30369 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
30370 original-location="foo"@}
30372 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
30373 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
30374 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
30375 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
30376 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
30377 original-location="mi-dprintf.c:26"@}
30381 @subheading The @code{-break-list} Command
30382 @findex -break-list
30384 @subsubheading Synopsis
30390 Displays the list of inserted breakpoints, showing the following fields:
30394 number of the breakpoint
30396 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
30398 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
30401 is the breakpoint enabled or no: @samp{y} or @samp{n}
30403 memory location at which the breakpoint is set
30405 logical location of the breakpoint, expressed by function name, file
30407 @item Thread-groups
30408 list of thread groups to which this breakpoint applies
30410 number of times the breakpoint has been hit
30413 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
30414 @code{body} field is an empty list.
30416 @subsubheading @value{GDBN} Command
30418 The corresponding @value{GDBN} command is @samp{info break}.
30420 @subsubheading Example
30425 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30426 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30427 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30428 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30429 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30430 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30431 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30432 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30433 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
30435 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30436 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
30437 line="13",thread-groups=["i1"],times="0"@}]@}
30441 Here's an example of the result when there are no breakpoints:
30446 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30447 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30448 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30449 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30450 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30451 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30452 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30457 @subheading The @code{-break-passcount} Command
30458 @findex -break-passcount
30460 @subsubheading Synopsis
30463 -break-passcount @var{tracepoint-number} @var{passcount}
30466 Set the passcount for tracepoint @var{tracepoint-number} to
30467 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
30468 is not a tracepoint, error is emitted. This corresponds to CLI
30469 command @samp{passcount}.
30471 @subheading The @code{-break-watch} Command
30472 @findex -break-watch
30474 @subsubheading Synopsis
30477 -break-watch [ -a | -r ]
30480 Create a watchpoint. With the @samp{-a} option it will create an
30481 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
30482 read from or on a write to the memory location. With the @samp{-r}
30483 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
30484 trigger only when the memory location is accessed for reading. Without
30485 either of the options, the watchpoint created is a regular watchpoint,
30486 i.e., it will trigger when the memory location is accessed for writing.
30487 @xref{Set Watchpoints, , Setting Watchpoints}.
30489 Note that @samp{-break-list} will report a single list of watchpoints and
30490 breakpoints inserted.
30492 @subsubheading @value{GDBN} Command
30494 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
30497 @subsubheading Example
30499 Setting a watchpoint on a variable in the @code{main} function:
30504 ^done,wpt=@{number="2",exp="x"@}
30509 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
30510 value=@{old="-268439212",new="55"@},
30511 frame=@{func="main",args=[],file="recursive2.c",
30512 fullname="/home/foo/bar/recursive2.c",line="5"@}
30516 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
30517 the program execution twice: first for the variable changing value, then
30518 for the watchpoint going out of scope.
30523 ^done,wpt=@{number="5",exp="C"@}
30528 *stopped,reason="watchpoint-trigger",
30529 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
30530 frame=@{func="callee4",args=[],
30531 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30532 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30537 *stopped,reason="watchpoint-scope",wpnum="5",
30538 frame=@{func="callee3",args=[@{name="strarg",
30539 value="0x11940 \"A string argument.\""@}],
30540 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30541 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30545 Listing breakpoints and watchpoints, at different points in the program
30546 execution. Note that once the watchpoint goes out of scope, it is
30552 ^done,wpt=@{number="2",exp="C"@}
30555 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30556 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30557 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30558 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30559 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30560 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30561 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30562 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30563 addr="0x00010734",func="callee4",
30564 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30565 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
30567 bkpt=@{number="2",type="watchpoint",disp="keep",
30568 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
30573 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
30574 value=@{old="-276895068",new="3"@},
30575 frame=@{func="callee4",args=[],
30576 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30577 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30580 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30581 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30582 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30583 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30584 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30585 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30586 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30587 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30588 addr="0x00010734",func="callee4",
30589 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30590 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
30592 bkpt=@{number="2",type="watchpoint",disp="keep",
30593 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
30597 ^done,reason="watchpoint-scope",wpnum="2",
30598 frame=@{func="callee3",args=[@{name="strarg",
30599 value="0x11940 \"A string argument.\""@}],
30600 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30601 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30604 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30605 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30606 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30607 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30608 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30609 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30610 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30611 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30612 addr="0x00010734",func="callee4",
30613 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30614 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30615 thread-groups=["i1"],times="1"@}]@}
30620 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30621 @node GDB/MI Catchpoint Commands
30622 @section @sc{gdb/mi} Catchpoint Commands
30624 This section documents @sc{gdb/mi} commands for manipulating
30628 * Shared Library GDB/MI Catchpoint Commands::
30629 * Ada Exception GDB/MI Catchpoint Commands::
30632 @node Shared Library GDB/MI Catchpoint Commands
30633 @subsection Shared Library @sc{gdb/mi} Catchpoints
30635 @subheading The @code{-catch-load} Command
30636 @findex -catch-load
30638 @subsubheading Synopsis
30641 -catch-load [ -t ] [ -d ] @var{regexp}
30644 Add a catchpoint for library load events. If the @samp{-t} option is used,
30645 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30646 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
30647 in a disabled state. The @samp{regexp} argument is a regular
30648 expression used to match the name of the loaded library.
30651 @subsubheading @value{GDBN} Command
30653 The corresponding @value{GDBN} command is @samp{catch load}.
30655 @subsubheading Example
30658 -catch-load -t foo.so
30659 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
30660 what="load of library matching foo.so",catch-type="load",times="0"@}
30665 @subheading The @code{-catch-unload} Command
30666 @findex -catch-unload
30668 @subsubheading Synopsis
30671 -catch-unload [ -t ] [ -d ] @var{regexp}
30674 Add a catchpoint for library unload events. If the @samp{-t} option is
30675 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30676 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
30677 created in a disabled state. The @samp{regexp} argument is a regular
30678 expression used to match the name of the unloaded library.
30680 @subsubheading @value{GDBN} Command
30682 The corresponding @value{GDBN} command is @samp{catch unload}.
30684 @subsubheading Example
30687 -catch-unload -d bar.so
30688 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
30689 what="load of library matching bar.so",catch-type="unload",times="0"@}
30693 @node Ada Exception GDB/MI Catchpoint Commands
30694 @subsection Ada Exception @sc{gdb/mi} Catchpoints
30696 The following @sc{gdb/mi} commands can be used to create catchpoints
30697 that stop the execution when Ada exceptions are being raised.
30699 @subheading The @code{-catch-assert} Command
30700 @findex -catch-assert
30702 @subsubheading Synopsis
30705 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
30708 Add a catchpoint for failed Ada assertions.
30710 The possible optional parameters for this command are:
30713 @item -c @var{condition}
30714 Make the catchpoint conditional on @var{condition}.
30716 Create a disabled catchpoint.
30718 Create a temporary catchpoint.
30721 @subsubheading @value{GDBN} Command
30723 The corresponding @value{GDBN} command is @samp{catch assert}.
30725 @subsubheading Example
30729 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
30730 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
30731 thread-groups=["i1"],times="0",
30732 original-location="__gnat_debug_raise_assert_failure"@}
30736 @subheading The @code{-catch-exception} Command
30737 @findex -catch-exception
30739 @subsubheading Synopsis
30742 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30746 Add a catchpoint stopping when Ada exceptions are raised.
30747 By default, the command stops the program when any Ada exception
30748 gets raised. But it is also possible, by using some of the
30749 optional parameters described below, to create more selective
30752 The possible optional parameters for this command are:
30755 @item -c @var{condition}
30756 Make the catchpoint conditional on @var{condition}.
30758 Create a disabled catchpoint.
30759 @item -e @var{exception-name}
30760 Only stop when @var{exception-name} is raised. This option cannot
30761 be used combined with @samp{-u}.
30763 Create a temporary catchpoint.
30765 Stop only when an unhandled exception gets raised. This option
30766 cannot be used combined with @samp{-e}.
30769 @subsubheading @value{GDBN} Command
30771 The corresponding @value{GDBN} commands are @samp{catch exception}
30772 and @samp{catch exception unhandled}.
30774 @subsubheading Example
30777 -catch-exception -e Program_Error
30778 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30779 enabled="y",addr="0x0000000000404874",
30780 what="`Program_Error' Ada exception", thread-groups=["i1"],
30781 times="0",original-location="__gnat_debug_raise_exception"@}
30785 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30786 @node GDB/MI Program Context
30787 @section @sc{gdb/mi} Program Context
30789 @subheading The @code{-exec-arguments} Command
30790 @findex -exec-arguments
30793 @subsubheading Synopsis
30796 -exec-arguments @var{args}
30799 Set the inferior program arguments, to be used in the next
30802 @subsubheading @value{GDBN} Command
30804 The corresponding @value{GDBN} command is @samp{set args}.
30806 @subsubheading Example
30810 -exec-arguments -v word
30817 @subheading The @code{-exec-show-arguments} Command
30818 @findex -exec-show-arguments
30820 @subsubheading Synopsis
30823 -exec-show-arguments
30826 Print the arguments of the program.
30828 @subsubheading @value{GDBN} Command
30830 The corresponding @value{GDBN} command is @samp{show args}.
30832 @subsubheading Example
30837 @subheading The @code{-environment-cd} Command
30838 @findex -environment-cd
30840 @subsubheading Synopsis
30843 -environment-cd @var{pathdir}
30846 Set @value{GDBN}'s working directory.
30848 @subsubheading @value{GDBN} Command
30850 The corresponding @value{GDBN} command is @samp{cd}.
30852 @subsubheading Example
30856 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30862 @subheading The @code{-environment-directory} Command
30863 @findex -environment-directory
30865 @subsubheading Synopsis
30868 -environment-directory [ -r ] [ @var{pathdir} ]+
30871 Add directories @var{pathdir} to beginning of search path for source files.
30872 If the @samp{-r} option is used, the search path is reset to the default
30873 search path. If directories @var{pathdir} are supplied in addition to the
30874 @samp{-r} option, the search path is first reset and then addition
30876 Multiple directories may be specified, separated by blanks. Specifying
30877 multiple directories in a single command
30878 results in the directories added to the beginning of the
30879 search path in the same order they were presented in the command.
30880 If blanks are needed as
30881 part of a directory name, double-quotes should be used around
30882 the name. In the command output, the path will show up separated
30883 by the system directory-separator character. The directory-separator
30884 character must not be used
30885 in any directory name.
30886 If no directories are specified, the current search path is displayed.
30888 @subsubheading @value{GDBN} Command
30890 The corresponding @value{GDBN} command is @samp{dir}.
30892 @subsubheading Example
30896 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30897 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30899 -environment-directory ""
30900 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30902 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
30903 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
30905 -environment-directory -r
30906 ^done,source-path="$cdir:$cwd"
30911 @subheading The @code{-environment-path} Command
30912 @findex -environment-path
30914 @subsubheading Synopsis
30917 -environment-path [ -r ] [ @var{pathdir} ]+
30920 Add directories @var{pathdir} to beginning of search path for object files.
30921 If the @samp{-r} option is used, the search path is reset to the original
30922 search path that existed at gdb start-up. If directories @var{pathdir} are
30923 supplied in addition to the
30924 @samp{-r} option, the search path is first reset and then addition
30926 Multiple directories may be specified, separated by blanks. Specifying
30927 multiple directories in a single command
30928 results in the directories added to the beginning of the
30929 search path in the same order they were presented in the command.
30930 If blanks are needed as
30931 part of a directory name, double-quotes should be used around
30932 the name. In the command output, the path will show up separated
30933 by the system directory-separator character. The directory-separator
30934 character must not be used
30935 in any directory name.
30936 If no directories are specified, the current path is displayed.
30939 @subsubheading @value{GDBN} Command
30941 The corresponding @value{GDBN} command is @samp{path}.
30943 @subsubheading Example
30948 ^done,path="/usr/bin"
30950 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
30951 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
30953 -environment-path -r /usr/local/bin
30954 ^done,path="/usr/local/bin:/usr/bin"
30959 @subheading The @code{-environment-pwd} Command
30960 @findex -environment-pwd
30962 @subsubheading Synopsis
30968 Show the current working directory.
30970 @subsubheading @value{GDBN} Command
30972 The corresponding @value{GDBN} command is @samp{pwd}.
30974 @subsubheading Example
30979 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
30983 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30984 @node GDB/MI Thread Commands
30985 @section @sc{gdb/mi} Thread Commands
30988 @subheading The @code{-thread-info} Command
30989 @findex -thread-info
30991 @subsubheading Synopsis
30994 -thread-info [ @var{thread-id} ]
30997 Reports information about either a specific thread, if
30998 the @var{thread-id} parameter is present, or about all
30999 threads. When printing information about all threads,
31000 also reports the current thread.
31002 @subsubheading @value{GDBN} Command
31004 The @samp{info thread} command prints the same information
31007 @subsubheading Result
31009 The result is a list of threads. The following attributes are
31010 defined for a given thread:
31014 This field exists only for the current thread. It has the value @samp{*}.
31017 The identifier that @value{GDBN} uses to refer to the thread.
31020 The identifier that the target uses to refer to the thread.
31023 Extra information about the thread, in a target-specific format. This
31027 The name of the thread. If the user specified a name using the
31028 @code{thread name} command, then this name is given. Otherwise, if
31029 @value{GDBN} can extract the thread name from the target, then that
31030 name is given. If @value{GDBN} cannot find the thread name, then this
31034 The stack frame currently executing in the thread.
31037 The thread's state. The @samp{state} field may have the following
31042 The thread is stopped. Frame information is available for stopped
31046 The thread is running. There's no frame information for running
31052 If @value{GDBN} can find the CPU core on which this thread is running,
31053 then this field is the core identifier. This field is optional.
31057 @subsubheading Example
31062 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31063 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
31064 args=[]@},state="running"@},
31065 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31066 frame=@{level="0",addr="0x0804891f",func="foo",
31067 args=[@{name="i",value="10"@}],
31068 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
31069 state="running"@}],
31070 current-thread-id="1"
31074 @subheading The @code{-thread-list-ids} Command
31075 @findex -thread-list-ids
31077 @subsubheading Synopsis
31083 Produces a list of the currently known @value{GDBN} thread ids. At the
31084 end of the list it also prints the total number of such threads.
31086 This command is retained for historical reasons, the
31087 @code{-thread-info} command should be used instead.
31089 @subsubheading @value{GDBN} Command
31091 Part of @samp{info threads} supplies the same information.
31093 @subsubheading Example
31098 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31099 current-thread-id="1",number-of-threads="3"
31104 @subheading The @code{-thread-select} Command
31105 @findex -thread-select
31107 @subsubheading Synopsis
31110 -thread-select @var{threadnum}
31113 Make @var{threadnum} the current thread. It prints the number of the new
31114 current thread, and the topmost frame for that thread.
31116 This command is deprecated in favor of explicitly using the
31117 @samp{--thread} option to each command.
31119 @subsubheading @value{GDBN} Command
31121 The corresponding @value{GDBN} command is @samp{thread}.
31123 @subsubheading Example
31130 *stopped,reason="end-stepping-range",thread-id="2",line="187",
31131 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
31135 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31136 number-of-threads="3"
31139 ^done,new-thread-id="3",
31140 frame=@{level="0",func="vprintf",
31141 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
31142 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
31146 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31147 @node GDB/MI Ada Tasking Commands
31148 @section @sc{gdb/mi} Ada Tasking Commands
31150 @subheading The @code{-ada-task-info} Command
31151 @findex -ada-task-info
31153 @subsubheading Synopsis
31156 -ada-task-info [ @var{task-id} ]
31159 Reports information about either a specific Ada task, if the
31160 @var{task-id} parameter is present, or about all Ada tasks.
31162 @subsubheading @value{GDBN} Command
31164 The @samp{info tasks} command prints the same information
31165 about all Ada tasks (@pxref{Ada Tasks}).
31167 @subsubheading Result
31169 The result is a table of Ada tasks. The following columns are
31170 defined for each Ada task:
31174 This field exists only for the current thread. It has the value @samp{*}.
31177 The identifier that @value{GDBN} uses to refer to the Ada task.
31180 The identifier that the target uses to refer to the Ada task.
31183 The identifier of the thread corresponding to the Ada task.
31185 This field should always exist, as Ada tasks are always implemented
31186 on top of a thread. But if @value{GDBN} cannot find this corresponding
31187 thread for any reason, the field is omitted.
31190 This field exists only when the task was created by another task.
31191 In this case, it provides the ID of the parent task.
31194 The base priority of the task.
31197 The current state of the task. For a detailed description of the
31198 possible states, see @ref{Ada Tasks}.
31201 The name of the task.
31205 @subsubheading Example
31209 ^done,tasks=@{nr_rows="3",nr_cols="8",
31210 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
31211 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
31212 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
31213 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
31214 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
31215 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
31216 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
31217 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
31218 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
31219 state="Child Termination Wait",name="main_task"@}]@}
31223 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31224 @node GDB/MI Program Execution
31225 @section @sc{gdb/mi} Program Execution
31227 These are the asynchronous commands which generate the out-of-band
31228 record @samp{*stopped}. Currently @value{GDBN} only really executes
31229 asynchronously with remote targets and this interaction is mimicked in
31232 @subheading The @code{-exec-continue} Command
31233 @findex -exec-continue
31235 @subsubheading Synopsis
31238 -exec-continue [--reverse] [--all|--thread-group N]
31241 Resumes the execution of the inferior program, which will continue
31242 to execute until it reaches a debugger stop event. If the
31243 @samp{--reverse} option is specified, execution resumes in reverse until
31244 it reaches a stop event. Stop events may include
31247 breakpoints or watchpoints
31249 signals or exceptions
31251 the end of the process (or its beginning under @samp{--reverse})
31253 the end or beginning of a replay log if one is being used.
31255 In all-stop mode (@pxref{All-Stop
31256 Mode}), may resume only one thread, or all threads, depending on the
31257 value of the @samp{scheduler-locking} variable. If @samp{--all} is
31258 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
31259 ignored in all-stop mode. If the @samp{--thread-group} options is
31260 specified, then all threads in that thread group are resumed.
31262 @subsubheading @value{GDBN} Command
31264 The corresponding @value{GDBN} corresponding is @samp{continue}.
31266 @subsubheading Example
31273 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
31274 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
31280 @subheading The @code{-exec-finish} Command
31281 @findex -exec-finish
31283 @subsubheading Synopsis
31286 -exec-finish [--reverse]
31289 Resumes the execution of the inferior program until the current
31290 function is exited. Displays the results returned by the function.
31291 If the @samp{--reverse} option is specified, resumes the reverse
31292 execution of the inferior program until the point where current
31293 function was called.
31295 @subsubheading @value{GDBN} Command
31297 The corresponding @value{GDBN} command is @samp{finish}.
31299 @subsubheading Example
31301 Function returning @code{void}.
31308 *stopped,reason="function-finished",frame=@{func="main",args=[],
31309 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
31313 Function returning other than @code{void}. The name of the internal
31314 @value{GDBN} variable storing the result is printed, together with the
31321 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
31322 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
31323 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31324 gdb-result-var="$1",return-value="0"
31329 @subheading The @code{-exec-interrupt} Command
31330 @findex -exec-interrupt
31332 @subsubheading Synopsis
31335 -exec-interrupt [--all|--thread-group N]
31338 Interrupts the background execution of the target. Note how the token
31339 associated with the stop message is the one for the execution command
31340 that has been interrupted. The token for the interrupt itself only
31341 appears in the @samp{^done} output. If the user is trying to
31342 interrupt a non-running program, an error message will be printed.
31344 Note that when asynchronous execution is enabled, this command is
31345 asynchronous just like other execution commands. That is, first the
31346 @samp{^done} response will be printed, and the target stop will be
31347 reported after that using the @samp{*stopped} notification.
31349 In non-stop mode, only the context thread is interrupted by default.
31350 All threads (in all inferiors) will be interrupted if the
31351 @samp{--all} option is specified. If the @samp{--thread-group}
31352 option is specified, all threads in that group will be interrupted.
31354 @subsubheading @value{GDBN} Command
31356 The corresponding @value{GDBN} command is @samp{interrupt}.
31358 @subsubheading Example
31369 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
31370 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
31371 fullname="/home/foo/bar/try.c",line="13"@}
31376 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
31380 @subheading The @code{-exec-jump} Command
31383 @subsubheading Synopsis
31386 -exec-jump @var{location}
31389 Resumes execution of the inferior program at the location specified by
31390 parameter. @xref{Specify Location}, for a description of the
31391 different forms of @var{location}.
31393 @subsubheading @value{GDBN} Command
31395 The corresponding @value{GDBN} command is @samp{jump}.
31397 @subsubheading Example
31400 -exec-jump foo.c:10
31401 *running,thread-id="all"
31406 @subheading The @code{-exec-next} Command
31409 @subsubheading Synopsis
31412 -exec-next [--reverse]
31415 Resumes execution of the inferior program, stopping when the beginning
31416 of the next source line is reached.
31418 If the @samp{--reverse} option is specified, resumes reverse execution
31419 of the inferior program, stopping at the beginning of the previous
31420 source line. If you issue this command on the first line of a
31421 function, it will take you back to the caller of that function, to the
31422 source line where the function was called.
31425 @subsubheading @value{GDBN} Command
31427 The corresponding @value{GDBN} command is @samp{next}.
31429 @subsubheading Example
31435 *stopped,reason="end-stepping-range",line="8",file="hello.c"
31440 @subheading The @code{-exec-next-instruction} Command
31441 @findex -exec-next-instruction
31443 @subsubheading Synopsis
31446 -exec-next-instruction [--reverse]
31449 Executes one machine instruction. If the instruction is a function
31450 call, continues until the function returns. If the program stops at an
31451 instruction in the middle of a source line, the address will be
31454 If the @samp{--reverse} option is specified, resumes reverse execution
31455 of the inferior program, stopping at the previous instruction. If the
31456 previously executed instruction was a return from another function,
31457 it will continue to execute in reverse until the call to that function
31458 (from the current stack frame) is reached.
31460 @subsubheading @value{GDBN} Command
31462 The corresponding @value{GDBN} command is @samp{nexti}.
31464 @subsubheading Example
31468 -exec-next-instruction
31472 *stopped,reason="end-stepping-range",
31473 addr="0x000100d4",line="5",file="hello.c"
31478 @subheading The @code{-exec-return} Command
31479 @findex -exec-return
31481 @subsubheading Synopsis
31487 Makes current function return immediately. Doesn't execute the inferior.
31488 Displays the new current frame.
31490 @subsubheading @value{GDBN} Command
31492 The corresponding @value{GDBN} command is @samp{return}.
31494 @subsubheading Example
31498 200-break-insert callee4
31499 200^done,bkpt=@{number="1",addr="0x00010734",
31500 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31505 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31506 frame=@{func="callee4",args=[],
31507 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31508 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31514 111^done,frame=@{level="0",func="callee3",
31515 args=[@{name="strarg",
31516 value="0x11940 \"A string argument.\""@}],
31517 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31518 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
31523 @subheading The @code{-exec-run} Command
31526 @subsubheading Synopsis
31529 -exec-run [ --all | --thread-group N ] [ --start ]
31532 Starts execution of the inferior from the beginning. The inferior
31533 executes until either a breakpoint is encountered or the program
31534 exits. In the latter case the output will include an exit code, if
31535 the program has exited exceptionally.
31537 When neither the @samp{--all} nor the @samp{--thread-group} option
31538 is specified, the current inferior is started. If the
31539 @samp{--thread-group} option is specified, it should refer to a thread
31540 group of type @samp{process}, and that thread group will be started.
31541 If the @samp{--all} option is specified, then all inferiors will be started.
31543 Using the @samp{--start} option instructs the debugger to stop
31544 the execution at the start of the inferior's main subprogram,
31545 following the same behavior as the @code{start} command
31546 (@pxref{Starting}).
31548 @subsubheading @value{GDBN} Command
31550 The corresponding @value{GDBN} command is @samp{run}.
31552 @subsubheading Examples
31557 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
31562 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31563 frame=@{func="main",args=[],file="recursive2.c",
31564 fullname="/home/foo/bar/recursive2.c",line="4"@}
31569 Program exited normally:
31577 *stopped,reason="exited-normally"
31582 Program exited exceptionally:
31590 *stopped,reason="exited",exit-code="01"
31594 Another way the program can terminate is if it receives a signal such as
31595 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31599 *stopped,reason="exited-signalled",signal-name="SIGINT",
31600 signal-meaning="Interrupt"
31604 @c @subheading -exec-signal
31607 @subheading The @code{-exec-step} Command
31610 @subsubheading Synopsis
31613 -exec-step [--reverse]
31616 Resumes execution of the inferior program, stopping when the beginning
31617 of the next source line is reached, if the next source line is not a
31618 function call. If it is, stop at the first instruction of the called
31619 function. If the @samp{--reverse} option is specified, resumes reverse
31620 execution of the inferior program, stopping at the beginning of the
31621 previously executed source line.
31623 @subsubheading @value{GDBN} Command
31625 The corresponding @value{GDBN} command is @samp{step}.
31627 @subsubheading Example
31629 Stepping into a function:
31635 *stopped,reason="end-stepping-range",
31636 frame=@{func="foo",args=[@{name="a",value="10"@},
31637 @{name="b",value="0"@}],file="recursive2.c",
31638 fullname="/home/foo/bar/recursive2.c",line="11"@}
31648 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
31653 @subheading The @code{-exec-step-instruction} Command
31654 @findex -exec-step-instruction
31656 @subsubheading Synopsis
31659 -exec-step-instruction [--reverse]
31662 Resumes the inferior which executes one machine instruction. If the
31663 @samp{--reverse} option is specified, resumes reverse execution of the
31664 inferior program, stopping at the previously executed instruction.
31665 The output, once @value{GDBN} has stopped, will vary depending on
31666 whether we have stopped in the middle of a source line or not. In the
31667 former case, the address at which the program stopped will be printed
31670 @subsubheading @value{GDBN} Command
31672 The corresponding @value{GDBN} command is @samp{stepi}.
31674 @subsubheading Example
31678 -exec-step-instruction
31682 *stopped,reason="end-stepping-range",
31683 frame=@{func="foo",args=[],file="try.c",
31684 fullname="/home/foo/bar/try.c",line="10"@}
31686 -exec-step-instruction
31690 *stopped,reason="end-stepping-range",
31691 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
31692 fullname="/home/foo/bar/try.c",line="10"@}
31697 @subheading The @code{-exec-until} Command
31698 @findex -exec-until
31700 @subsubheading Synopsis
31703 -exec-until [ @var{location} ]
31706 Executes the inferior until the @var{location} specified in the
31707 argument is reached. If there is no argument, the inferior executes
31708 until a source line greater than the current one is reached. The
31709 reason for stopping in this case will be @samp{location-reached}.
31711 @subsubheading @value{GDBN} Command
31713 The corresponding @value{GDBN} command is @samp{until}.
31715 @subsubheading Example
31719 -exec-until recursive2.c:6
31723 *stopped,reason="location-reached",frame=@{func="main",args=[],
31724 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
31729 @subheading -file-clear
31730 Is this going away????
31733 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31734 @node GDB/MI Stack Manipulation
31735 @section @sc{gdb/mi} Stack Manipulation Commands
31737 @subheading The @code{-enable-frame-filters} Command
31738 @findex -enable-frame-filters
31741 -enable-frame-filters
31744 @value{GDBN} allows Python-based frame filters to affect the output of
31745 the MI commands relating to stack traces. As there is no way to
31746 implement this in a fully backward-compatible way, a front end must
31747 request that this functionality be enabled.
31749 Once enabled, this feature cannot be disabled.
31751 Note that if Python support has not been compiled into @value{GDBN},
31752 this command will still succeed (and do nothing).
31754 @subheading The @code{-stack-info-frame} Command
31755 @findex -stack-info-frame
31757 @subsubheading Synopsis
31763 Get info on the selected frame.
31765 @subsubheading @value{GDBN} Command
31767 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
31768 (without arguments).
31770 @subsubheading Example
31775 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
31776 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31777 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
31781 @subheading The @code{-stack-info-depth} Command
31782 @findex -stack-info-depth
31784 @subsubheading Synopsis
31787 -stack-info-depth [ @var{max-depth} ]
31790 Return the depth of the stack. If the integer argument @var{max-depth}
31791 is specified, do not count beyond @var{max-depth} frames.
31793 @subsubheading @value{GDBN} Command
31795 There's no equivalent @value{GDBN} command.
31797 @subsubheading Example
31799 For a stack with frame levels 0 through 11:
31806 -stack-info-depth 4
31809 -stack-info-depth 12
31812 -stack-info-depth 11
31815 -stack-info-depth 13
31820 @anchor{-stack-list-arguments}
31821 @subheading The @code{-stack-list-arguments} Command
31822 @findex -stack-list-arguments
31824 @subsubheading Synopsis
31827 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31828 [ @var{low-frame} @var{high-frame} ]
31831 Display a list of the arguments for the frames between @var{low-frame}
31832 and @var{high-frame} (inclusive). If @var{low-frame} and
31833 @var{high-frame} are not provided, list the arguments for the whole
31834 call stack. If the two arguments are equal, show the single frame
31835 at the corresponding level. It is an error if @var{low-frame} is
31836 larger than the actual number of frames. On the other hand,
31837 @var{high-frame} may be larger than the actual number of frames, in
31838 which case only existing frames will be returned.
31840 If @var{print-values} is 0 or @code{--no-values}, print only the names of
31841 the variables; if it is 1 or @code{--all-values}, print also their
31842 values; and if it is 2 or @code{--simple-values}, print the name,
31843 type and value for simple data types, and the name and type for arrays,
31844 structures and unions. If the option @code{--no-frame-filters} is
31845 supplied, then Python frame filters will not be executed.
31847 If the @code{--skip-unavailable} option is specified, arguments that
31848 are not available are not listed. Partially available arguments
31849 are still displayed, however.
31851 Use of this command to obtain arguments in a single frame is
31852 deprecated in favor of the @samp{-stack-list-variables} command.
31854 @subsubheading @value{GDBN} Command
31856 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
31857 @samp{gdb_get_args} command which partially overlaps with the
31858 functionality of @samp{-stack-list-arguments}.
31860 @subsubheading Example
31867 frame=@{level="0",addr="0x00010734",func="callee4",
31868 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31869 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
31870 frame=@{level="1",addr="0x0001076c",func="callee3",
31871 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31872 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
31873 frame=@{level="2",addr="0x0001078c",func="callee2",
31874 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31875 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
31876 frame=@{level="3",addr="0x000107b4",func="callee1",
31877 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31878 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
31879 frame=@{level="4",addr="0x000107e0",func="main",
31880 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31881 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
31883 -stack-list-arguments 0
31886 frame=@{level="0",args=[]@},
31887 frame=@{level="1",args=[name="strarg"]@},
31888 frame=@{level="2",args=[name="intarg",name="strarg"]@},
31889 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
31890 frame=@{level="4",args=[]@}]
31892 -stack-list-arguments 1
31895 frame=@{level="0",args=[]@},
31897 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31898 frame=@{level="2",args=[
31899 @{name="intarg",value="2"@},
31900 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31901 @{frame=@{level="3",args=[
31902 @{name="intarg",value="2"@},
31903 @{name="strarg",value="0x11940 \"A string argument.\""@},
31904 @{name="fltarg",value="3.5"@}]@},
31905 frame=@{level="4",args=[]@}]
31907 -stack-list-arguments 0 2 2
31908 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
31910 -stack-list-arguments 1 2 2
31911 ^done,stack-args=[frame=@{level="2",
31912 args=[@{name="intarg",value="2"@},
31913 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
31917 @c @subheading -stack-list-exception-handlers
31920 @anchor{-stack-list-frames}
31921 @subheading The @code{-stack-list-frames} Command
31922 @findex -stack-list-frames
31924 @subsubheading Synopsis
31927 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
31930 List the frames currently on the stack. For each frame it displays the
31935 The frame number, 0 being the topmost frame, i.e., the innermost function.
31937 The @code{$pc} value for that frame.
31941 File name of the source file where the function lives.
31942 @item @var{fullname}
31943 The full file name of the source file where the function lives.
31945 Line number corresponding to the @code{$pc}.
31947 The shared library where this function is defined. This is only given
31948 if the frame's function is not known.
31951 If invoked without arguments, this command prints a backtrace for the
31952 whole stack. If given two integer arguments, it shows the frames whose
31953 levels are between the two arguments (inclusive). If the two arguments
31954 are equal, it shows the single frame at the corresponding level. It is
31955 an error if @var{low-frame} is larger than the actual number of
31956 frames. On the other hand, @var{high-frame} may be larger than the
31957 actual number of frames, in which case only existing frames will be
31958 returned. If the option @code{--no-frame-filters} is supplied, then
31959 Python frame filters will not be executed.
31961 @subsubheading @value{GDBN} Command
31963 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
31965 @subsubheading Example
31967 Full stack backtrace:
31973 [frame=@{level="0",addr="0x0001076c",func="foo",
31974 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
31975 frame=@{level="1",addr="0x000107a4",func="foo",
31976 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31977 frame=@{level="2",addr="0x000107a4",func="foo",
31978 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31979 frame=@{level="3",addr="0x000107a4",func="foo",
31980 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31981 frame=@{level="4",addr="0x000107a4",func="foo",
31982 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31983 frame=@{level="5",addr="0x000107a4",func="foo",
31984 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31985 frame=@{level="6",addr="0x000107a4",func="foo",
31986 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31987 frame=@{level="7",addr="0x000107a4",func="foo",
31988 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31989 frame=@{level="8",addr="0x000107a4",func="foo",
31990 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31991 frame=@{level="9",addr="0x000107a4",func="foo",
31992 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31993 frame=@{level="10",addr="0x000107a4",func="foo",
31994 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31995 frame=@{level="11",addr="0x00010738",func="main",
31996 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
32000 Show frames between @var{low_frame} and @var{high_frame}:
32004 -stack-list-frames 3 5
32006 [frame=@{level="3",addr="0x000107a4",func="foo",
32007 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32008 frame=@{level="4",addr="0x000107a4",func="foo",
32009 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32010 frame=@{level="5",addr="0x000107a4",func="foo",
32011 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
32015 Show a single frame:
32019 -stack-list-frames 3 3
32021 [frame=@{level="3",addr="0x000107a4",func="foo",
32022 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
32027 @subheading The @code{-stack-list-locals} Command
32028 @findex -stack-list-locals
32029 @anchor{-stack-list-locals}
32031 @subsubheading Synopsis
32034 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32037 Display the local variable names for the selected frame. If
32038 @var{print-values} is 0 or @code{--no-values}, print only the names of
32039 the variables; if it is 1 or @code{--all-values}, print also their
32040 values; and if it is 2 or @code{--simple-values}, print the name,
32041 type and value for simple data types, and the name and type for arrays,
32042 structures and unions. In this last case, a frontend can immediately
32043 display the value of simple data types and create variable objects for
32044 other data types when the user wishes to explore their values in
32045 more detail. If the option @code{--no-frame-filters} is supplied, then
32046 Python frame filters will not be executed.
32048 If the @code{--skip-unavailable} option is specified, local variables
32049 that are not available are not listed. Partially available local
32050 variables are still displayed, however.
32052 This command is deprecated in favor of the
32053 @samp{-stack-list-variables} command.
32055 @subsubheading @value{GDBN} Command
32057 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
32059 @subsubheading Example
32063 -stack-list-locals 0
32064 ^done,locals=[name="A",name="B",name="C"]
32066 -stack-list-locals --all-values
32067 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
32068 @{name="C",value="@{1, 2, 3@}"@}]
32069 -stack-list-locals --simple-values
32070 ^done,locals=[@{name="A",type="int",value="1"@},
32071 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
32075 @anchor{-stack-list-variables}
32076 @subheading The @code{-stack-list-variables} Command
32077 @findex -stack-list-variables
32079 @subsubheading Synopsis
32082 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32085 Display the names of local variables and function arguments for the selected frame. If
32086 @var{print-values} is 0 or @code{--no-values}, print only the names of
32087 the variables; if it is 1 or @code{--all-values}, print also their
32088 values; and if it is 2 or @code{--simple-values}, print the name,
32089 type and value for simple data types, and the name and type for arrays,
32090 structures and unions. If the option @code{--no-frame-filters} is
32091 supplied, then Python frame filters will not be executed.
32093 If the @code{--skip-unavailable} option is specified, local variables
32094 and arguments that are not available are not listed. Partially
32095 available arguments and local variables are still displayed, however.
32097 @subsubheading Example
32101 -stack-list-variables --thread 1 --frame 0 --all-values
32102 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
32107 @subheading The @code{-stack-select-frame} Command
32108 @findex -stack-select-frame
32110 @subsubheading Synopsis
32113 -stack-select-frame @var{framenum}
32116 Change the selected frame. Select a different frame @var{framenum} on
32119 This command in deprecated in favor of passing the @samp{--frame}
32120 option to every command.
32122 @subsubheading @value{GDBN} Command
32124 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
32125 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
32127 @subsubheading Example
32131 -stack-select-frame 2
32136 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32137 @node GDB/MI Variable Objects
32138 @section @sc{gdb/mi} Variable Objects
32142 @subheading Motivation for Variable Objects in @sc{gdb/mi}
32144 For the implementation of a variable debugger window (locals, watched
32145 expressions, etc.), we are proposing the adaptation of the existing code
32146 used by @code{Insight}.
32148 The two main reasons for that are:
32152 It has been proven in practice (it is already on its second generation).
32155 It will shorten development time (needless to say how important it is
32159 The original interface was designed to be used by Tcl code, so it was
32160 slightly changed so it could be used through @sc{gdb/mi}. This section
32161 describes the @sc{gdb/mi} operations that will be available and gives some
32162 hints about their use.
32164 @emph{Note}: In addition to the set of operations described here, we
32165 expect the @sc{gui} implementation of a variable window to require, at
32166 least, the following operations:
32169 @item @code{-gdb-show} @code{output-radix}
32170 @item @code{-stack-list-arguments}
32171 @item @code{-stack-list-locals}
32172 @item @code{-stack-select-frame}
32177 @subheading Introduction to Variable Objects
32179 @cindex variable objects in @sc{gdb/mi}
32181 Variable objects are "object-oriented" MI interface for examining and
32182 changing values of expressions. Unlike some other MI interfaces that
32183 work with expressions, variable objects are specifically designed for
32184 simple and efficient presentation in the frontend. A variable object
32185 is identified by string name. When a variable object is created, the
32186 frontend specifies the expression for that variable object. The
32187 expression can be a simple variable, or it can be an arbitrary complex
32188 expression, and can even involve CPU registers. After creating a
32189 variable object, the frontend can invoke other variable object
32190 operations---for example to obtain or change the value of a variable
32191 object, or to change display format.
32193 Variable objects have hierarchical tree structure. Any variable object
32194 that corresponds to a composite type, such as structure in C, has
32195 a number of child variable objects, for example corresponding to each
32196 element of a structure. A child variable object can itself have
32197 children, recursively. Recursion ends when we reach
32198 leaf variable objects, which always have built-in types. Child variable
32199 objects are created only by explicit request, so if a frontend
32200 is not interested in the children of a particular variable object, no
32201 child will be created.
32203 For a leaf variable object it is possible to obtain its value as a
32204 string, or set the value from a string. String value can be also
32205 obtained for a non-leaf variable object, but it's generally a string
32206 that only indicates the type of the object, and does not list its
32207 contents. Assignment to a non-leaf variable object is not allowed.
32209 A frontend does not need to read the values of all variable objects each time
32210 the program stops. Instead, MI provides an update command that lists all
32211 variable objects whose values has changed since the last update
32212 operation. This considerably reduces the amount of data that must
32213 be transferred to the frontend. As noted above, children variable
32214 objects are created on demand, and only leaf variable objects have a
32215 real value. As result, gdb will read target memory only for leaf
32216 variables that frontend has created.
32218 The automatic update is not always desirable. For example, a frontend
32219 might want to keep a value of some expression for future reference,
32220 and never update it. For another example, fetching memory is
32221 relatively slow for embedded targets, so a frontend might want
32222 to disable automatic update for the variables that are either not
32223 visible on the screen, or ``closed''. This is possible using so
32224 called ``frozen variable objects''. Such variable objects are never
32225 implicitly updated.
32227 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
32228 fixed variable object, the expression is parsed when the variable
32229 object is created, including associating identifiers to specific
32230 variables. The meaning of expression never changes. For a floating
32231 variable object the values of variables whose names appear in the
32232 expressions are re-evaluated every time in the context of the current
32233 frame. Consider this example:
32238 struct work_state state;
32245 If a fixed variable object for the @code{state} variable is created in
32246 this function, and we enter the recursive call, the variable
32247 object will report the value of @code{state} in the top-level
32248 @code{do_work} invocation. On the other hand, a floating variable
32249 object will report the value of @code{state} in the current frame.
32251 If an expression specified when creating a fixed variable object
32252 refers to a local variable, the variable object becomes bound to the
32253 thread and frame in which the variable object is created. When such
32254 variable object is updated, @value{GDBN} makes sure that the
32255 thread/frame combination the variable object is bound to still exists,
32256 and re-evaluates the variable object in context of that thread/frame.
32258 The following is the complete set of @sc{gdb/mi} operations defined to
32259 access this functionality:
32261 @multitable @columnfractions .4 .6
32262 @item @strong{Operation}
32263 @tab @strong{Description}
32265 @item @code{-enable-pretty-printing}
32266 @tab enable Python-based pretty-printing
32267 @item @code{-var-create}
32268 @tab create a variable object
32269 @item @code{-var-delete}
32270 @tab delete the variable object and/or its children
32271 @item @code{-var-set-format}
32272 @tab set the display format of this variable
32273 @item @code{-var-show-format}
32274 @tab show the display format of this variable
32275 @item @code{-var-info-num-children}
32276 @tab tells how many children this object has
32277 @item @code{-var-list-children}
32278 @tab return a list of the object's children
32279 @item @code{-var-info-type}
32280 @tab show the type of this variable object
32281 @item @code{-var-info-expression}
32282 @tab print parent-relative expression that this variable object represents
32283 @item @code{-var-info-path-expression}
32284 @tab print full expression that this variable object represents
32285 @item @code{-var-show-attributes}
32286 @tab is this variable editable? does it exist here?
32287 @item @code{-var-evaluate-expression}
32288 @tab get the value of this variable
32289 @item @code{-var-assign}
32290 @tab set the value of this variable
32291 @item @code{-var-update}
32292 @tab update the variable and its children
32293 @item @code{-var-set-frozen}
32294 @tab set frozeness attribute
32295 @item @code{-var-set-update-range}
32296 @tab set range of children to display on update
32299 In the next subsection we describe each operation in detail and suggest
32300 how it can be used.
32302 @subheading Description And Use of Operations on Variable Objects
32304 @subheading The @code{-enable-pretty-printing} Command
32305 @findex -enable-pretty-printing
32308 -enable-pretty-printing
32311 @value{GDBN} allows Python-based visualizers to affect the output of the
32312 MI variable object commands. However, because there was no way to
32313 implement this in a fully backward-compatible way, a front end must
32314 request that this functionality be enabled.
32316 Once enabled, this feature cannot be disabled.
32318 Note that if Python support has not been compiled into @value{GDBN},
32319 this command will still succeed (and do nothing).
32321 This feature is currently (as of @value{GDBN} 7.0) experimental, and
32322 may work differently in future versions of @value{GDBN}.
32324 @subheading The @code{-var-create} Command
32325 @findex -var-create
32327 @subsubheading Synopsis
32330 -var-create @{@var{name} | "-"@}
32331 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
32334 This operation creates a variable object, which allows the monitoring of
32335 a variable, the result of an expression, a memory cell or a CPU
32338 The @var{name} parameter is the string by which the object can be
32339 referenced. It must be unique. If @samp{-} is specified, the varobj
32340 system will generate a string ``varNNNNNN'' automatically. It will be
32341 unique provided that one does not specify @var{name} of that format.
32342 The command fails if a duplicate name is found.
32344 The frame under which the expression should be evaluated can be
32345 specified by @var{frame-addr}. A @samp{*} indicates that the current
32346 frame should be used. A @samp{@@} indicates that a floating variable
32347 object must be created.
32349 @var{expression} is any expression valid on the current language set (must not
32350 begin with a @samp{*}), or one of the following:
32354 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
32357 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
32360 @samp{$@var{regname}} --- a CPU register name
32363 @cindex dynamic varobj
32364 A varobj's contents may be provided by a Python-based pretty-printer. In this
32365 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
32366 have slightly different semantics in some cases. If the
32367 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
32368 will never create a dynamic varobj. This ensures backward
32369 compatibility for existing clients.
32371 @subsubheading Result
32373 This operation returns attributes of the newly-created varobj. These
32378 The name of the varobj.
32381 The number of children of the varobj. This number is not necessarily
32382 reliable for a dynamic varobj. Instead, you must examine the
32383 @samp{has_more} attribute.
32386 The varobj's scalar value. For a varobj whose type is some sort of
32387 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
32388 will not be interesting.
32391 The varobj's type. This is a string representation of the type, as
32392 would be printed by the @value{GDBN} CLI. If @samp{print object}
32393 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32394 @emph{actual} (derived) type of the object is shown rather than the
32395 @emph{declared} one.
32398 If a variable object is bound to a specific thread, then this is the
32399 thread's identifier.
32402 For a dynamic varobj, this indicates whether there appear to be any
32403 children available. For a non-dynamic varobj, this will be 0.
32406 This attribute will be present and have the value @samp{1} if the
32407 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32408 then this attribute will not be present.
32411 A dynamic varobj can supply a display hint to the front end. The
32412 value comes directly from the Python pretty-printer object's
32413 @code{display_hint} method. @xref{Pretty Printing API}.
32416 Typical output will look like this:
32419 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
32420 has_more="@var{has_more}"
32424 @subheading The @code{-var-delete} Command
32425 @findex -var-delete
32427 @subsubheading Synopsis
32430 -var-delete [ -c ] @var{name}
32433 Deletes a previously created variable object and all of its children.
32434 With the @samp{-c} option, just deletes the children.
32436 Returns an error if the object @var{name} is not found.
32439 @subheading The @code{-var-set-format} Command
32440 @findex -var-set-format
32442 @subsubheading Synopsis
32445 -var-set-format @var{name} @var{format-spec}
32448 Sets the output format for the value of the object @var{name} to be
32451 @anchor{-var-set-format}
32452 The syntax for the @var{format-spec} is as follows:
32455 @var{format-spec} @expansion{}
32456 @{binary | decimal | hexadecimal | octal | natural@}
32459 The natural format is the default format choosen automatically
32460 based on the variable type (like decimal for an @code{int}, hex
32461 for pointers, etc.).
32463 For a variable with children, the format is set only on the
32464 variable itself, and the children are not affected.
32466 @subheading The @code{-var-show-format} Command
32467 @findex -var-show-format
32469 @subsubheading Synopsis
32472 -var-show-format @var{name}
32475 Returns the format used to display the value of the object @var{name}.
32478 @var{format} @expansion{}
32483 @subheading The @code{-var-info-num-children} Command
32484 @findex -var-info-num-children
32486 @subsubheading Synopsis
32489 -var-info-num-children @var{name}
32492 Returns the number of children of a variable object @var{name}:
32498 Note that this number is not completely reliable for a dynamic varobj.
32499 It will return the current number of children, but more children may
32503 @subheading The @code{-var-list-children} Command
32504 @findex -var-list-children
32506 @subsubheading Synopsis
32509 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
32511 @anchor{-var-list-children}
32513 Return a list of the children of the specified variable object and
32514 create variable objects for them, if they do not already exist. With
32515 a single argument or if @var{print-values} has a value of 0 or
32516 @code{--no-values}, print only the names of the variables; if
32517 @var{print-values} is 1 or @code{--all-values}, also print their
32518 values; and if it is 2 or @code{--simple-values} print the name and
32519 value for simple data types and just the name for arrays, structures
32522 @var{from} and @var{to}, if specified, indicate the range of children
32523 to report. If @var{from} or @var{to} is less than zero, the range is
32524 reset and all children will be reported. Otherwise, children starting
32525 at @var{from} (zero-based) and up to and excluding @var{to} will be
32528 If a child range is requested, it will only affect the current call to
32529 @code{-var-list-children}, but not future calls to @code{-var-update}.
32530 For this, you must instead use @code{-var-set-update-range}. The
32531 intent of this approach is to enable a front end to implement any
32532 update approach it likes; for example, scrolling a view may cause the
32533 front end to request more children with @code{-var-list-children}, and
32534 then the front end could call @code{-var-set-update-range} with a
32535 different range to ensure that future updates are restricted to just
32538 For each child the following results are returned:
32543 Name of the variable object created for this child.
32546 The expression to be shown to the user by the front end to designate this child.
32547 For example this may be the name of a structure member.
32549 For a dynamic varobj, this value cannot be used to form an
32550 expression. There is no way to do this at all with a dynamic varobj.
32552 For C/C@t{++} structures there are several pseudo children returned to
32553 designate access qualifiers. For these pseudo children @var{exp} is
32554 @samp{public}, @samp{private}, or @samp{protected}. In this case the
32555 type and value are not present.
32557 A dynamic varobj will not report the access qualifying
32558 pseudo-children, regardless of the language. This information is not
32559 available at all with a dynamic varobj.
32562 Number of children this child has. For a dynamic varobj, this will be
32566 The type of the child. If @samp{print object}
32567 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32568 @emph{actual} (derived) type of the object is shown rather than the
32569 @emph{declared} one.
32572 If values were requested, this is the value.
32575 If this variable object is associated with a thread, this is the thread id.
32576 Otherwise this result is not present.
32579 If the variable object is frozen, this variable will be present with a value of 1.
32582 A dynamic varobj can supply a display hint to the front end. The
32583 value comes directly from the Python pretty-printer object's
32584 @code{display_hint} method. @xref{Pretty Printing API}.
32587 This attribute will be present and have the value @samp{1} if the
32588 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32589 then this attribute will not be present.
32593 The result may have its own attributes:
32597 A dynamic varobj can supply a display hint to the front end. The
32598 value comes directly from the Python pretty-printer object's
32599 @code{display_hint} method. @xref{Pretty Printing API}.
32602 This is an integer attribute which is nonzero if there are children
32603 remaining after the end of the selected range.
32606 @subsubheading Example
32610 -var-list-children n
32611 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32612 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
32614 -var-list-children --all-values n
32615 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32616 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
32620 @subheading The @code{-var-info-type} Command
32621 @findex -var-info-type
32623 @subsubheading Synopsis
32626 -var-info-type @var{name}
32629 Returns the type of the specified variable @var{name}. The type is
32630 returned as a string in the same format as it is output by the
32634 type=@var{typename}
32638 @subheading The @code{-var-info-expression} Command
32639 @findex -var-info-expression
32641 @subsubheading Synopsis
32644 -var-info-expression @var{name}
32647 Returns a string that is suitable for presenting this
32648 variable object in user interface. The string is generally
32649 not valid expression in the current language, and cannot be evaluated.
32651 For example, if @code{a} is an array, and variable object
32652 @code{A} was created for @code{a}, then we'll get this output:
32655 (gdb) -var-info-expression A.1
32656 ^done,lang="C",exp="1"
32660 Here, the value of @code{lang} is the language name, which can be
32661 found in @ref{Supported Languages}.
32663 Note that the output of the @code{-var-list-children} command also
32664 includes those expressions, so the @code{-var-info-expression} command
32667 @subheading The @code{-var-info-path-expression} Command
32668 @findex -var-info-path-expression
32670 @subsubheading Synopsis
32673 -var-info-path-expression @var{name}
32676 Returns an expression that can be evaluated in the current
32677 context and will yield the same value that a variable object has.
32678 Compare this with the @code{-var-info-expression} command, which
32679 result can be used only for UI presentation. Typical use of
32680 the @code{-var-info-path-expression} command is creating a
32681 watchpoint from a variable object.
32683 This command is currently not valid for children of a dynamic varobj,
32684 and will give an error when invoked on one.
32686 For example, suppose @code{C} is a C@t{++} class, derived from class
32687 @code{Base}, and that the @code{Base} class has a member called
32688 @code{m_size}. Assume a variable @code{c} is has the type of
32689 @code{C} and a variable object @code{C} was created for variable
32690 @code{c}. Then, we'll get this output:
32692 (gdb) -var-info-path-expression C.Base.public.m_size
32693 ^done,path_expr=((Base)c).m_size)
32696 @subheading The @code{-var-show-attributes} Command
32697 @findex -var-show-attributes
32699 @subsubheading Synopsis
32702 -var-show-attributes @var{name}
32705 List attributes of the specified variable object @var{name}:
32708 status=@var{attr} [ ( ,@var{attr} )* ]
32712 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
32714 @subheading The @code{-var-evaluate-expression} Command
32715 @findex -var-evaluate-expression
32717 @subsubheading Synopsis
32720 -var-evaluate-expression [-f @var{format-spec}] @var{name}
32723 Evaluates the expression that is represented by the specified variable
32724 object and returns its value as a string. The format of the string
32725 can be specified with the @samp{-f} option. The possible values of
32726 this option are the same as for @code{-var-set-format}
32727 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
32728 the current display format will be used. The current display format
32729 can be changed using the @code{-var-set-format} command.
32735 Note that one must invoke @code{-var-list-children} for a variable
32736 before the value of a child variable can be evaluated.
32738 @subheading The @code{-var-assign} Command
32739 @findex -var-assign
32741 @subsubheading Synopsis
32744 -var-assign @var{name} @var{expression}
32747 Assigns the value of @var{expression} to the variable object specified
32748 by @var{name}. The object must be @samp{editable}. If the variable's
32749 value is altered by the assign, the variable will show up in any
32750 subsequent @code{-var-update} list.
32752 @subsubheading Example
32760 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
32764 @subheading The @code{-var-update} Command
32765 @findex -var-update
32767 @subsubheading Synopsis
32770 -var-update [@var{print-values}] @{@var{name} | "*"@}
32773 Reevaluate the expressions corresponding to the variable object
32774 @var{name} and all its direct and indirect children, and return the
32775 list of variable objects whose values have changed; @var{name} must
32776 be a root variable object. Here, ``changed'' means that the result of
32777 @code{-var-evaluate-expression} before and after the
32778 @code{-var-update} is different. If @samp{*} is used as the variable
32779 object names, all existing variable objects are updated, except
32780 for frozen ones (@pxref{-var-set-frozen}). The option
32781 @var{print-values} determines whether both names and values, or just
32782 names are printed. The possible values of this option are the same
32783 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
32784 recommended to use the @samp{--all-values} option, to reduce the
32785 number of MI commands needed on each program stop.
32787 With the @samp{*} parameter, if a variable object is bound to a
32788 currently running thread, it will not be updated, without any
32791 If @code{-var-set-update-range} was previously used on a varobj, then
32792 only the selected range of children will be reported.
32794 @code{-var-update} reports all the changed varobjs in a tuple named
32797 Each item in the change list is itself a tuple holding:
32801 The name of the varobj.
32804 If values were requested for this update, then this field will be
32805 present and will hold the value of the varobj.
32808 @anchor{-var-update}
32809 This field is a string which may take one of three values:
32813 The variable object's current value is valid.
32816 The variable object does not currently hold a valid value but it may
32817 hold one in the future if its associated expression comes back into
32821 The variable object no longer holds a valid value.
32822 This can occur when the executable file being debugged has changed,
32823 either through recompilation or by using the @value{GDBN} @code{file}
32824 command. The front end should normally choose to delete these variable
32828 In the future new values may be added to this list so the front should
32829 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
32832 This is only present if the varobj is still valid. If the type
32833 changed, then this will be the string @samp{true}; otherwise it will
32836 When a varobj's type changes, its children are also likely to have
32837 become incorrect. Therefore, the varobj's children are automatically
32838 deleted when this attribute is @samp{true}. Also, the varobj's update
32839 range, when set using the @code{-var-set-update-range} command, is
32843 If the varobj's type changed, then this field will be present and will
32846 @item new_num_children
32847 For a dynamic varobj, if the number of children changed, or if the
32848 type changed, this will be the new number of children.
32850 The @samp{numchild} field in other varobj responses is generally not
32851 valid for a dynamic varobj -- it will show the number of children that
32852 @value{GDBN} knows about, but because dynamic varobjs lazily
32853 instantiate their children, this will not reflect the number of
32854 children which may be available.
32856 The @samp{new_num_children} attribute only reports changes to the
32857 number of children known by @value{GDBN}. This is the only way to
32858 detect whether an update has removed children (which necessarily can
32859 only happen at the end of the update range).
32862 The display hint, if any.
32865 This is an integer value, which will be 1 if there are more children
32866 available outside the varobj's update range.
32869 This attribute will be present and have the value @samp{1} if the
32870 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32871 then this attribute will not be present.
32874 If new children were added to a dynamic varobj within the selected
32875 update range (as set by @code{-var-set-update-range}), then they will
32876 be listed in this attribute.
32879 @subsubheading Example
32886 -var-update --all-values var1
32887 ^done,changelist=[@{name="var1",value="3",in_scope="true",
32888 type_changed="false"@}]
32892 @subheading The @code{-var-set-frozen} Command
32893 @findex -var-set-frozen
32894 @anchor{-var-set-frozen}
32896 @subsubheading Synopsis
32899 -var-set-frozen @var{name} @var{flag}
32902 Set the frozenness flag on the variable object @var{name}. The
32903 @var{flag} parameter should be either @samp{1} to make the variable
32904 frozen or @samp{0} to make it unfrozen. If a variable object is
32905 frozen, then neither itself, nor any of its children, are
32906 implicitly updated by @code{-var-update} of
32907 a parent variable or by @code{-var-update *}. Only
32908 @code{-var-update} of the variable itself will update its value and
32909 values of its children. After a variable object is unfrozen, it is
32910 implicitly updated by all subsequent @code{-var-update} operations.
32911 Unfreezing a variable does not update it, only subsequent
32912 @code{-var-update} does.
32914 @subsubheading Example
32918 -var-set-frozen V 1
32923 @subheading The @code{-var-set-update-range} command
32924 @findex -var-set-update-range
32925 @anchor{-var-set-update-range}
32927 @subsubheading Synopsis
32930 -var-set-update-range @var{name} @var{from} @var{to}
32933 Set the range of children to be returned by future invocations of
32934 @code{-var-update}.
32936 @var{from} and @var{to} indicate the range of children to report. If
32937 @var{from} or @var{to} is less than zero, the range is reset and all
32938 children will be reported. Otherwise, children starting at @var{from}
32939 (zero-based) and up to and excluding @var{to} will be reported.
32941 @subsubheading Example
32945 -var-set-update-range V 1 2
32949 @subheading The @code{-var-set-visualizer} command
32950 @findex -var-set-visualizer
32951 @anchor{-var-set-visualizer}
32953 @subsubheading Synopsis
32956 -var-set-visualizer @var{name} @var{visualizer}
32959 Set a visualizer for the variable object @var{name}.
32961 @var{visualizer} is the visualizer to use. The special value
32962 @samp{None} means to disable any visualizer in use.
32964 If not @samp{None}, @var{visualizer} must be a Python expression.
32965 This expression must evaluate to a callable object which accepts a
32966 single argument. @value{GDBN} will call this object with the value of
32967 the varobj @var{name} as an argument (this is done so that the same
32968 Python pretty-printing code can be used for both the CLI and MI).
32969 When called, this object must return an object which conforms to the
32970 pretty-printing interface (@pxref{Pretty Printing API}).
32972 The pre-defined function @code{gdb.default_visualizer} may be used to
32973 select a visualizer by following the built-in process
32974 (@pxref{Selecting Pretty-Printers}). This is done automatically when
32975 a varobj is created, and so ordinarily is not needed.
32977 This feature is only available if Python support is enabled. The MI
32978 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
32979 can be used to check this.
32981 @subsubheading Example
32983 Resetting the visualizer:
32987 -var-set-visualizer V None
32991 Reselecting the default (type-based) visualizer:
32995 -var-set-visualizer V gdb.default_visualizer
32999 Suppose @code{SomeClass} is a visualizer class. A lambda expression
33000 can be used to instantiate this class for a varobj:
33004 -var-set-visualizer V "lambda val: SomeClass()"
33008 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33009 @node GDB/MI Data Manipulation
33010 @section @sc{gdb/mi} Data Manipulation
33012 @cindex data manipulation, in @sc{gdb/mi}
33013 @cindex @sc{gdb/mi}, data manipulation
33014 This section describes the @sc{gdb/mi} commands that manipulate data:
33015 examine memory and registers, evaluate expressions, etc.
33017 @c REMOVED FROM THE INTERFACE.
33018 @c @subheading -data-assign
33019 @c Change the value of a program variable. Plenty of side effects.
33020 @c @subsubheading GDB Command
33022 @c @subsubheading Example
33025 @subheading The @code{-data-disassemble} Command
33026 @findex -data-disassemble
33028 @subsubheading Synopsis
33032 [ -s @var{start-addr} -e @var{end-addr} ]
33033 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
33041 @item @var{start-addr}
33042 is the beginning address (or @code{$pc})
33043 @item @var{end-addr}
33045 @item @var{filename}
33046 is the name of the file to disassemble
33047 @item @var{linenum}
33048 is the line number to disassemble around
33050 is the number of disassembly lines to be produced. If it is -1,
33051 the whole function will be disassembled, in case no @var{end-addr} is
33052 specified. If @var{end-addr} is specified as a non-zero value, and
33053 @var{lines} is lower than the number of disassembly lines between
33054 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
33055 displayed; if @var{lines} is higher than the number of lines between
33056 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
33059 is either 0 (meaning only disassembly), 1 (meaning mixed source and
33060 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
33061 mixed source and disassembly with raw opcodes).
33064 @subsubheading Result
33066 The result of the @code{-data-disassemble} command will be a list named
33067 @samp{asm_insns}, the contents of this list depend on the @var{mode}
33068 used with the @code{-data-disassemble} command.
33070 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
33075 The address at which this instruction was disassembled.
33078 The name of the function this instruction is within.
33081 The decimal offset in bytes from the start of @samp{func-name}.
33084 The text disassembly for this @samp{address}.
33087 This field is only present for mode 2. This contains the raw opcode
33088 bytes for the @samp{inst} field.
33092 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
33093 @samp{src_and_asm_line}, each of which has the following fields:
33097 The line number within @samp{file}.
33100 The file name from the compilation unit. This might be an absolute
33101 file name or a relative file name depending on the compile command
33105 Absolute file name of @samp{file}. It is converted to a canonical form
33106 using the source file search path
33107 (@pxref{Source Path, ,Specifying Source Directories})
33108 and after resolving all the symbolic links.
33110 If the source file is not found this field will contain the path as
33111 present in the debug information.
33113 @item line_asm_insn
33114 This is a list of tuples containing the disassembly for @samp{line} in
33115 @samp{file}. The fields of each tuple are the same as for
33116 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
33117 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
33122 Note that whatever included in the @samp{inst} field, is not
33123 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
33126 @subsubheading @value{GDBN} Command
33128 The corresponding @value{GDBN} command is @samp{disassemble}.
33130 @subsubheading Example
33132 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
33136 -data-disassemble -s $pc -e "$pc + 20" -- 0
33139 @{address="0x000107c0",func-name="main",offset="4",
33140 inst="mov 2, %o0"@},
33141 @{address="0x000107c4",func-name="main",offset="8",
33142 inst="sethi %hi(0x11800), %o2"@},
33143 @{address="0x000107c8",func-name="main",offset="12",
33144 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
33145 @{address="0x000107cc",func-name="main",offset="16",
33146 inst="sethi %hi(0x11800), %o2"@},
33147 @{address="0x000107d0",func-name="main",offset="20",
33148 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
33152 Disassemble the whole @code{main} function. Line 32 is part of
33156 -data-disassemble -f basics.c -l 32 -- 0
33158 @{address="0x000107bc",func-name="main",offset="0",
33159 inst="save %sp, -112, %sp"@},
33160 @{address="0x000107c0",func-name="main",offset="4",
33161 inst="mov 2, %o0"@},
33162 @{address="0x000107c4",func-name="main",offset="8",
33163 inst="sethi %hi(0x11800), %o2"@},
33165 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
33166 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
33170 Disassemble 3 instructions from the start of @code{main}:
33174 -data-disassemble -f basics.c -l 32 -n 3 -- 0
33176 @{address="0x000107bc",func-name="main",offset="0",
33177 inst="save %sp, -112, %sp"@},
33178 @{address="0x000107c0",func-name="main",offset="4",
33179 inst="mov 2, %o0"@},
33180 @{address="0x000107c4",func-name="main",offset="8",
33181 inst="sethi %hi(0x11800), %o2"@}]
33185 Disassemble 3 instructions from the start of @code{main} in mixed mode:
33189 -data-disassemble -f basics.c -l 32 -n 3 -- 1
33191 src_and_asm_line=@{line="31",
33192 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33193 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33194 line_asm_insn=[@{address="0x000107bc",
33195 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
33196 src_and_asm_line=@{line="32",
33197 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33198 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33199 line_asm_insn=[@{address="0x000107c0",
33200 func-name="main",offset="4",inst="mov 2, %o0"@},
33201 @{address="0x000107c4",func-name="main",offset="8",
33202 inst="sethi %hi(0x11800), %o2"@}]@}]
33207 @subheading The @code{-data-evaluate-expression} Command
33208 @findex -data-evaluate-expression
33210 @subsubheading Synopsis
33213 -data-evaluate-expression @var{expr}
33216 Evaluate @var{expr} as an expression. The expression could contain an
33217 inferior function call. The function call will execute synchronously.
33218 If the expression contains spaces, it must be enclosed in double quotes.
33220 @subsubheading @value{GDBN} Command
33222 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
33223 @samp{call}. In @code{gdbtk} only, there's a corresponding
33224 @samp{gdb_eval} command.
33226 @subsubheading Example
33228 In the following example, the numbers that precede the commands are the
33229 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
33230 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
33234 211-data-evaluate-expression A
33237 311-data-evaluate-expression &A
33238 311^done,value="0xefffeb7c"
33240 411-data-evaluate-expression A+3
33243 511-data-evaluate-expression "A + 3"
33249 @subheading The @code{-data-list-changed-registers} Command
33250 @findex -data-list-changed-registers
33252 @subsubheading Synopsis
33255 -data-list-changed-registers
33258 Display a list of the registers that have changed.
33260 @subsubheading @value{GDBN} Command
33262 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
33263 has the corresponding command @samp{gdb_changed_register_list}.
33265 @subsubheading Example
33267 On a PPC MBX board:
33275 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
33276 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
33279 -data-list-changed-registers
33280 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
33281 "10","11","13","14","15","16","17","18","19","20","21","22","23",
33282 "24","25","26","27","28","30","31","64","65","66","67","69"]
33287 @subheading The @code{-data-list-register-names} Command
33288 @findex -data-list-register-names
33290 @subsubheading Synopsis
33293 -data-list-register-names [ ( @var{regno} )+ ]
33296 Show a list of register names for the current target. If no arguments
33297 are given, it shows a list of the names of all the registers. If
33298 integer numbers are given as arguments, it will print a list of the
33299 names of the registers corresponding to the arguments. To ensure
33300 consistency between a register name and its number, the output list may
33301 include empty register names.
33303 @subsubheading @value{GDBN} Command
33305 @value{GDBN} does not have a command which corresponds to
33306 @samp{-data-list-register-names}. In @code{gdbtk} there is a
33307 corresponding command @samp{gdb_regnames}.
33309 @subsubheading Example
33311 For the PPC MBX board:
33314 -data-list-register-names
33315 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
33316 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
33317 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
33318 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
33319 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
33320 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
33321 "", "pc","ps","cr","lr","ctr","xer"]
33323 -data-list-register-names 1 2 3
33324 ^done,register-names=["r1","r2","r3"]
33328 @subheading The @code{-data-list-register-values} Command
33329 @findex -data-list-register-values
33331 @subsubheading Synopsis
33334 -data-list-register-values
33335 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
33338 Display the registers' contents. @var{fmt} is the format according to
33339 which the registers' contents are to be returned, followed by an optional
33340 list of numbers specifying the registers to display. A missing list of
33341 numbers indicates that the contents of all the registers must be
33342 returned. The @code{--skip-unavailable} option indicates that only
33343 the available registers are to be returned.
33345 Allowed formats for @var{fmt} are:
33362 @subsubheading @value{GDBN} Command
33364 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
33365 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
33367 @subsubheading Example
33369 For a PPC MBX board (note: line breaks are for readability only, they
33370 don't appear in the actual output):
33374 -data-list-register-values r 64 65
33375 ^done,register-values=[@{number="64",value="0xfe00a300"@},
33376 @{number="65",value="0x00029002"@}]
33378 -data-list-register-values x
33379 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
33380 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
33381 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
33382 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
33383 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
33384 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
33385 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
33386 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
33387 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
33388 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
33389 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
33390 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
33391 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
33392 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
33393 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
33394 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
33395 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
33396 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
33397 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
33398 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
33399 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
33400 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
33401 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
33402 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
33403 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
33404 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
33405 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
33406 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
33407 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
33408 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
33409 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
33410 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
33411 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
33412 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
33413 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
33414 @{number="69",value="0x20002b03"@}]
33419 @subheading The @code{-data-read-memory} Command
33420 @findex -data-read-memory
33422 This command is deprecated, use @code{-data-read-memory-bytes} instead.
33424 @subsubheading Synopsis
33427 -data-read-memory [ -o @var{byte-offset} ]
33428 @var{address} @var{word-format} @var{word-size}
33429 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
33436 @item @var{address}
33437 An expression specifying the address of the first memory word to be
33438 read. Complex expressions containing embedded white space should be
33439 quoted using the C convention.
33441 @item @var{word-format}
33442 The format to be used to print the memory words. The notation is the
33443 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
33446 @item @var{word-size}
33447 The size of each memory word in bytes.
33449 @item @var{nr-rows}
33450 The number of rows in the output table.
33452 @item @var{nr-cols}
33453 The number of columns in the output table.
33456 If present, indicates that each row should include an @sc{ascii} dump. The
33457 value of @var{aschar} is used as a padding character when a byte is not a
33458 member of the printable @sc{ascii} character set (printable @sc{ascii}
33459 characters are those whose code is between 32 and 126, inclusively).
33461 @item @var{byte-offset}
33462 An offset to add to the @var{address} before fetching memory.
33465 This command displays memory contents as a table of @var{nr-rows} by
33466 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
33467 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
33468 (returned as @samp{total-bytes}). Should less than the requested number
33469 of bytes be returned by the target, the missing words are identified
33470 using @samp{N/A}. The number of bytes read from the target is returned
33471 in @samp{nr-bytes} and the starting address used to read memory in
33474 The address of the next/previous row or page is available in
33475 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
33478 @subsubheading @value{GDBN} Command
33480 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
33481 @samp{gdb_get_mem} memory read command.
33483 @subsubheading Example
33485 Read six bytes of memory starting at @code{bytes+6} but then offset by
33486 @code{-6} bytes. Format as three rows of two columns. One byte per
33487 word. Display each word in hex.
33491 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
33492 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
33493 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
33494 prev-page="0x0000138a",memory=[
33495 @{addr="0x00001390",data=["0x00","0x01"]@},
33496 @{addr="0x00001392",data=["0x02","0x03"]@},
33497 @{addr="0x00001394",data=["0x04","0x05"]@}]
33501 Read two bytes of memory starting at address @code{shorts + 64} and
33502 display as a single word formatted in decimal.
33506 5-data-read-memory shorts+64 d 2 1 1
33507 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
33508 next-row="0x00001512",prev-row="0x0000150e",
33509 next-page="0x00001512",prev-page="0x0000150e",memory=[
33510 @{addr="0x00001510",data=["128"]@}]
33514 Read thirty two bytes of memory starting at @code{bytes+16} and format
33515 as eight rows of four columns. Include a string encoding with @samp{x}
33516 used as the non-printable character.
33520 4-data-read-memory bytes+16 x 1 8 4 x
33521 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
33522 next-row="0x000013c0",prev-row="0x0000139c",
33523 next-page="0x000013c0",prev-page="0x00001380",memory=[
33524 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
33525 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
33526 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
33527 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
33528 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
33529 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
33530 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
33531 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
33535 @subheading The @code{-data-read-memory-bytes} Command
33536 @findex -data-read-memory-bytes
33538 @subsubheading Synopsis
33541 -data-read-memory-bytes [ -o @var{byte-offset} ]
33542 @var{address} @var{count}
33549 @item @var{address}
33550 An expression specifying the address of the first memory word to be
33551 read. Complex expressions containing embedded white space should be
33552 quoted using the C convention.
33555 The number of bytes to read. This should be an integer literal.
33557 @item @var{byte-offset}
33558 The offsets in bytes relative to @var{address} at which to start
33559 reading. This should be an integer literal. This option is provided
33560 so that a frontend is not required to first evaluate address and then
33561 perform address arithmetics itself.
33565 This command attempts to read all accessible memory regions in the
33566 specified range. First, all regions marked as unreadable in the memory
33567 map (if one is defined) will be skipped. @xref{Memory Region
33568 Attributes}. Second, @value{GDBN} will attempt to read the remaining
33569 regions. For each one, if reading full region results in an errors,
33570 @value{GDBN} will try to read a subset of the region.
33572 In general, every single byte in the region may be readable or not,
33573 and the only way to read every readable byte is to try a read at
33574 every address, which is not practical. Therefore, @value{GDBN} will
33575 attempt to read all accessible bytes at either beginning or the end
33576 of the region, using a binary division scheme. This heuristic works
33577 well for reading accross a memory map boundary. Note that if a region
33578 has a readable range that is neither at the beginning or the end,
33579 @value{GDBN} will not read it.
33581 The result record (@pxref{GDB/MI Result Records}) that is output of
33582 the command includes a field named @samp{memory} whose content is a
33583 list of tuples. Each tuple represent a successfully read memory block
33584 and has the following fields:
33588 The start address of the memory block, as hexadecimal literal.
33591 The end address of the memory block, as hexadecimal literal.
33594 The offset of the memory block, as hexadecimal literal, relative to
33595 the start address passed to @code{-data-read-memory-bytes}.
33598 The contents of the memory block, in hex.
33604 @subsubheading @value{GDBN} Command
33606 The corresponding @value{GDBN} command is @samp{x}.
33608 @subsubheading Example
33612 -data-read-memory-bytes &a 10
33613 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
33615 contents="01000000020000000300"@}]
33620 @subheading The @code{-data-write-memory-bytes} Command
33621 @findex -data-write-memory-bytes
33623 @subsubheading Synopsis
33626 -data-write-memory-bytes @var{address} @var{contents}
33627 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
33634 @item @var{address}
33635 An expression specifying the address of the first memory word to be
33636 read. Complex expressions containing embedded white space should be
33637 quoted using the C convention.
33639 @item @var{contents}
33640 The hex-encoded bytes to write.
33643 Optional argument indicating the number of bytes to be written. If @var{count}
33644 is greater than @var{contents}' length, @value{GDBN} will repeatedly
33645 write @var{contents} until it fills @var{count} bytes.
33649 @subsubheading @value{GDBN} Command
33651 There's no corresponding @value{GDBN} command.
33653 @subsubheading Example
33657 -data-write-memory-bytes &a "aabbccdd"
33664 -data-write-memory-bytes &a "aabbccdd" 16e
33669 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33670 @node GDB/MI Tracepoint Commands
33671 @section @sc{gdb/mi} Tracepoint Commands
33673 The commands defined in this section implement MI support for
33674 tracepoints. For detailed introduction, see @ref{Tracepoints}.
33676 @subheading The @code{-trace-find} Command
33677 @findex -trace-find
33679 @subsubheading Synopsis
33682 -trace-find @var{mode} [@var{parameters}@dots{}]
33685 Find a trace frame using criteria defined by @var{mode} and
33686 @var{parameters}. The following table lists permissible
33687 modes and their parameters. For details of operation, see @ref{tfind}.
33692 No parameters are required. Stops examining trace frames.
33695 An integer is required as parameter. Selects tracepoint frame with
33698 @item tracepoint-number
33699 An integer is required as parameter. Finds next
33700 trace frame that corresponds to tracepoint with the specified number.
33703 An address is required as parameter. Finds
33704 next trace frame that corresponds to any tracepoint at the specified
33707 @item pc-inside-range
33708 Two addresses are required as parameters. Finds next trace
33709 frame that corresponds to a tracepoint at an address inside the
33710 specified range. Both bounds are considered to be inside the range.
33712 @item pc-outside-range
33713 Two addresses are required as parameters. Finds
33714 next trace frame that corresponds to a tracepoint at an address outside
33715 the specified range. Both bounds are considered to be inside the range.
33718 Line specification is required as parameter. @xref{Specify Location}.
33719 Finds next trace frame that corresponds to a tracepoint at
33720 the specified location.
33724 If @samp{none} was passed as @var{mode}, the response does not
33725 have fields. Otherwise, the response may have the following fields:
33729 This field has either @samp{0} or @samp{1} as the value, depending
33730 on whether a matching tracepoint was found.
33733 The index of the found traceframe. This field is present iff
33734 the @samp{found} field has value of @samp{1}.
33737 The index of the found tracepoint. This field is present iff
33738 the @samp{found} field has value of @samp{1}.
33741 The information about the frame corresponding to the found trace
33742 frame. This field is present only if a trace frame was found.
33743 @xref{GDB/MI Frame Information}, for description of this field.
33747 @subsubheading @value{GDBN} Command
33749 The corresponding @value{GDBN} command is @samp{tfind}.
33751 @subheading -trace-define-variable
33752 @findex -trace-define-variable
33754 @subsubheading Synopsis
33757 -trace-define-variable @var{name} [ @var{value} ]
33760 Create trace variable @var{name} if it does not exist. If
33761 @var{value} is specified, sets the initial value of the specified
33762 trace variable to that value. Note that the @var{name} should start
33763 with the @samp{$} character.
33765 @subsubheading @value{GDBN} Command
33767 The corresponding @value{GDBN} command is @samp{tvariable}.
33769 @subheading The @code{-trace-frame-collected} Command
33770 @findex -trace-frame-collected
33772 @subsubheading Synopsis
33775 -trace-frame-collected
33776 [--var-print-values @var{var_pval}]
33777 [--comp-print-values @var{comp_pval}]
33778 [--registers-format @var{regformat}]
33779 [--memory-contents]
33782 This command returns the set of collected objects, register names,
33783 trace state variable names, memory ranges and computed expressions
33784 that have been collected at a particular trace frame. The optional
33785 parameters to the command affect the output format in different ways.
33786 See the output description table below for more details.
33788 The reported names can be used in the normal manner to create
33789 varobjs and inspect the objects themselves. The items returned by
33790 this command are categorized so that it is clear which is a variable,
33791 which is a register, which is a trace state variable, which is a
33792 memory range and which is a computed expression.
33794 For instance, if the actions were
33796 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
33797 collect *(int*)0xaf02bef0@@40
33801 the object collected in its entirety would be @code{myVar}. The
33802 object @code{myArray} would be partially collected, because only the
33803 element at index @code{myIndex} would be collected. The remaining
33804 objects would be computed expressions.
33806 An example output would be:
33810 -trace-frame-collected
33812 explicit-variables=[@{name="myVar",value="1"@}],
33813 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
33814 @{name="myObj.field",value="0"@},
33815 @{name="myPtr->field",value="1"@},
33816 @{name="myCount + 2",value="3"@},
33817 @{name="$tvar1 + 1",value="43970027"@}],
33818 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
33819 @{number="1",value="0x0"@},
33820 @{number="2",value="0x4"@},
33822 @{number="125",value="0x0"@}],
33823 tvars=[@{name="$tvar1",current="43970026"@}],
33824 memory=[@{address="0x0000000000602264",length="4"@},
33825 @{address="0x0000000000615bc0",length="4"@}]
33832 @item explicit-variables
33833 The set of objects that have been collected in their entirety (as
33834 opposed to collecting just a few elements of an array or a few struct
33835 members). For each object, its name and value are printed.
33836 The @code{--var-print-values} option affects how or whether the value
33837 field is output. If @var{var_pval} is 0, then print only the names;
33838 if it is 1, print also their values; and if it is 2, print the name,
33839 type and value for simple data types, and the name and type for
33840 arrays, structures and unions.
33842 @item computed-expressions
33843 The set of computed expressions that have been collected at the
33844 current trace frame. The @code{--comp-print-values} option affects
33845 this set like the @code{--var-print-values} option affects the
33846 @code{explicit-variables} set. See above.
33849 The registers that have been collected at the current trace frame.
33850 For each register collected, the name and current value are returned.
33851 The value is formatted according to the @code{--registers-format}
33852 option. See the @command{-data-list-register-values} command for a
33853 list of the allowed formats. The default is @samp{x}.
33856 The trace state variables that have been collected at the current
33857 trace frame. For each trace state variable collected, the name and
33858 current value are returned.
33861 The set of memory ranges that have been collected at the current trace
33862 frame. Its content is a list of tuples. Each tuple represents a
33863 collected memory range and has the following fields:
33867 The start address of the memory range, as hexadecimal literal.
33870 The length of the memory range, as decimal literal.
33873 The contents of the memory block, in hex. This field is only present
33874 if the @code{--memory-contents} option is specified.
33880 @subsubheading @value{GDBN} Command
33882 There is no corresponding @value{GDBN} command.
33884 @subsubheading Example
33886 @subheading -trace-list-variables
33887 @findex -trace-list-variables
33889 @subsubheading Synopsis
33892 -trace-list-variables
33895 Return a table of all defined trace variables. Each element of the
33896 table has the following fields:
33900 The name of the trace variable. This field is always present.
33903 The initial value. This is a 64-bit signed integer. This
33904 field is always present.
33907 The value the trace variable has at the moment. This is a 64-bit
33908 signed integer. This field is absent iff current value is
33909 not defined, for example if the trace was never run, or is
33914 @subsubheading @value{GDBN} Command
33916 The corresponding @value{GDBN} command is @samp{tvariables}.
33918 @subsubheading Example
33922 -trace-list-variables
33923 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
33924 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
33925 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
33926 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
33927 body=[variable=@{name="$trace_timestamp",initial="0"@}
33928 variable=@{name="$foo",initial="10",current="15"@}]@}
33932 @subheading -trace-save
33933 @findex -trace-save
33935 @subsubheading Synopsis
33938 -trace-save [-r ] @var{filename}
33941 Saves the collected trace data to @var{filename}. Without the
33942 @samp{-r} option, the data is downloaded from the target and saved
33943 in a local file. With the @samp{-r} option the target is asked
33944 to perform the save.
33946 @subsubheading @value{GDBN} Command
33948 The corresponding @value{GDBN} command is @samp{tsave}.
33951 @subheading -trace-start
33952 @findex -trace-start
33954 @subsubheading Synopsis
33960 Starts a tracing experiments. The result of this command does not
33963 @subsubheading @value{GDBN} Command
33965 The corresponding @value{GDBN} command is @samp{tstart}.
33967 @subheading -trace-status
33968 @findex -trace-status
33970 @subsubheading Synopsis
33976 Obtains the status of a tracing experiment. The result may include
33977 the following fields:
33982 May have a value of either @samp{0}, when no tracing operations are
33983 supported, @samp{1}, when all tracing operations are supported, or
33984 @samp{file} when examining trace file. In the latter case, examining
33985 of trace frame is possible but new tracing experiement cannot be
33986 started. This field is always present.
33989 May have a value of either @samp{0} or @samp{1} depending on whether
33990 tracing experiement is in progress on target. This field is present
33991 if @samp{supported} field is not @samp{0}.
33994 Report the reason why the tracing was stopped last time. This field
33995 may be absent iff tracing was never stopped on target yet. The
33996 value of @samp{request} means the tracing was stopped as result of
33997 the @code{-trace-stop} command. The value of @samp{overflow} means
33998 the tracing buffer is full. The value of @samp{disconnection} means
33999 tracing was automatically stopped when @value{GDBN} has disconnected.
34000 The value of @samp{passcount} means tracing was stopped when a
34001 tracepoint was passed a maximal number of times for that tracepoint.
34002 This field is present if @samp{supported} field is not @samp{0}.
34004 @item stopping-tracepoint
34005 The number of tracepoint whose passcount as exceeded. This field is
34006 present iff the @samp{stop-reason} field has the value of
34010 @itemx frames-created
34011 The @samp{frames} field is a count of the total number of trace frames
34012 in the trace buffer, while @samp{frames-created} is the total created
34013 during the run, including ones that were discarded, such as when a
34014 circular trace buffer filled up. Both fields are optional.
34018 These fields tell the current size of the tracing buffer and the
34019 remaining space. These fields are optional.
34022 The value of the circular trace buffer flag. @code{1} means that the
34023 trace buffer is circular and old trace frames will be discarded if
34024 necessary to make room, @code{0} means that the trace buffer is linear
34028 The value of the disconnected tracing flag. @code{1} means that
34029 tracing will continue after @value{GDBN} disconnects, @code{0} means
34030 that the trace run will stop.
34033 The filename of the trace file being examined. This field is
34034 optional, and only present when examining a trace file.
34038 @subsubheading @value{GDBN} Command
34040 The corresponding @value{GDBN} command is @samp{tstatus}.
34042 @subheading -trace-stop
34043 @findex -trace-stop
34045 @subsubheading Synopsis
34051 Stops a tracing experiment. The result of this command has the same
34052 fields as @code{-trace-status}, except that the @samp{supported} and
34053 @samp{running} fields are not output.
34055 @subsubheading @value{GDBN} Command
34057 The corresponding @value{GDBN} command is @samp{tstop}.
34060 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34061 @node GDB/MI Symbol Query
34062 @section @sc{gdb/mi} Symbol Query Commands
34066 @subheading The @code{-symbol-info-address} Command
34067 @findex -symbol-info-address
34069 @subsubheading Synopsis
34072 -symbol-info-address @var{symbol}
34075 Describe where @var{symbol} is stored.
34077 @subsubheading @value{GDBN} Command
34079 The corresponding @value{GDBN} command is @samp{info address}.
34081 @subsubheading Example
34085 @subheading The @code{-symbol-info-file} Command
34086 @findex -symbol-info-file
34088 @subsubheading Synopsis
34094 Show the file for the symbol.
34096 @subsubheading @value{GDBN} Command
34098 There's no equivalent @value{GDBN} command. @code{gdbtk} has
34099 @samp{gdb_find_file}.
34101 @subsubheading Example
34105 @subheading The @code{-symbol-info-function} Command
34106 @findex -symbol-info-function
34108 @subsubheading Synopsis
34111 -symbol-info-function
34114 Show which function the symbol lives in.
34116 @subsubheading @value{GDBN} Command
34118 @samp{gdb_get_function} in @code{gdbtk}.
34120 @subsubheading Example
34124 @subheading The @code{-symbol-info-line} Command
34125 @findex -symbol-info-line
34127 @subsubheading Synopsis
34133 Show the core addresses of the code for a source line.
34135 @subsubheading @value{GDBN} Command
34137 The corresponding @value{GDBN} command is @samp{info line}.
34138 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
34140 @subsubheading Example
34144 @subheading The @code{-symbol-info-symbol} Command
34145 @findex -symbol-info-symbol
34147 @subsubheading Synopsis
34150 -symbol-info-symbol @var{addr}
34153 Describe what symbol is at location @var{addr}.
34155 @subsubheading @value{GDBN} Command
34157 The corresponding @value{GDBN} command is @samp{info symbol}.
34159 @subsubheading Example
34163 @subheading The @code{-symbol-list-functions} Command
34164 @findex -symbol-list-functions
34166 @subsubheading Synopsis
34169 -symbol-list-functions
34172 List the functions in the executable.
34174 @subsubheading @value{GDBN} Command
34176 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
34177 @samp{gdb_search} in @code{gdbtk}.
34179 @subsubheading Example
34184 @subheading The @code{-symbol-list-lines} Command
34185 @findex -symbol-list-lines
34187 @subsubheading Synopsis
34190 -symbol-list-lines @var{filename}
34193 Print the list of lines that contain code and their associated program
34194 addresses for the given source filename. The entries are sorted in
34195 ascending PC order.
34197 @subsubheading @value{GDBN} Command
34199 There is no corresponding @value{GDBN} command.
34201 @subsubheading Example
34204 -symbol-list-lines basics.c
34205 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
34211 @subheading The @code{-symbol-list-types} Command
34212 @findex -symbol-list-types
34214 @subsubheading Synopsis
34220 List all the type names.
34222 @subsubheading @value{GDBN} Command
34224 The corresponding commands are @samp{info types} in @value{GDBN},
34225 @samp{gdb_search} in @code{gdbtk}.
34227 @subsubheading Example
34231 @subheading The @code{-symbol-list-variables} Command
34232 @findex -symbol-list-variables
34234 @subsubheading Synopsis
34237 -symbol-list-variables
34240 List all the global and static variable names.
34242 @subsubheading @value{GDBN} Command
34244 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
34246 @subsubheading Example
34250 @subheading The @code{-symbol-locate} Command
34251 @findex -symbol-locate
34253 @subsubheading Synopsis
34259 @subsubheading @value{GDBN} Command
34261 @samp{gdb_loc} in @code{gdbtk}.
34263 @subsubheading Example
34267 @subheading The @code{-symbol-type} Command
34268 @findex -symbol-type
34270 @subsubheading Synopsis
34273 -symbol-type @var{variable}
34276 Show type of @var{variable}.
34278 @subsubheading @value{GDBN} Command
34280 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
34281 @samp{gdb_obj_variable}.
34283 @subsubheading Example
34288 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34289 @node GDB/MI File Commands
34290 @section @sc{gdb/mi} File Commands
34292 This section describes the GDB/MI commands to specify executable file names
34293 and to read in and obtain symbol table information.
34295 @subheading The @code{-file-exec-and-symbols} Command
34296 @findex -file-exec-and-symbols
34298 @subsubheading Synopsis
34301 -file-exec-and-symbols @var{file}
34304 Specify the executable file to be debugged. This file is the one from
34305 which the symbol table is also read. If no file is specified, the
34306 command clears the executable and symbol information. If breakpoints
34307 are set when using this command with no arguments, @value{GDBN} will produce
34308 error messages. Otherwise, no output is produced, except a completion
34311 @subsubheading @value{GDBN} Command
34313 The corresponding @value{GDBN} command is @samp{file}.
34315 @subsubheading Example
34319 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34325 @subheading The @code{-file-exec-file} Command
34326 @findex -file-exec-file
34328 @subsubheading Synopsis
34331 -file-exec-file @var{file}
34334 Specify the executable file to be debugged. Unlike
34335 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
34336 from this file. If used without argument, @value{GDBN} clears the information
34337 about the executable file. No output is produced, except a completion
34340 @subsubheading @value{GDBN} Command
34342 The corresponding @value{GDBN} command is @samp{exec-file}.
34344 @subsubheading Example
34348 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34355 @subheading The @code{-file-list-exec-sections} Command
34356 @findex -file-list-exec-sections
34358 @subsubheading Synopsis
34361 -file-list-exec-sections
34364 List the sections of the current executable file.
34366 @subsubheading @value{GDBN} Command
34368 The @value{GDBN} command @samp{info file} shows, among the rest, the same
34369 information as this command. @code{gdbtk} has a corresponding command
34370 @samp{gdb_load_info}.
34372 @subsubheading Example
34377 @subheading The @code{-file-list-exec-source-file} Command
34378 @findex -file-list-exec-source-file
34380 @subsubheading Synopsis
34383 -file-list-exec-source-file
34386 List the line number, the current source file, and the absolute path
34387 to the current source file for the current executable. The macro
34388 information field has a value of @samp{1} or @samp{0} depending on
34389 whether or not the file includes preprocessor macro information.
34391 @subsubheading @value{GDBN} Command
34393 The @value{GDBN} equivalent is @samp{info source}
34395 @subsubheading Example
34399 123-file-list-exec-source-file
34400 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
34405 @subheading The @code{-file-list-exec-source-files} Command
34406 @findex -file-list-exec-source-files
34408 @subsubheading Synopsis
34411 -file-list-exec-source-files
34414 List the source files for the current executable.
34416 It will always output both the filename and fullname (absolute file
34417 name) of a source file.
34419 @subsubheading @value{GDBN} Command
34421 The @value{GDBN} equivalent is @samp{info sources}.
34422 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
34424 @subsubheading Example
34427 -file-list-exec-source-files
34429 @{file=foo.c,fullname=/home/foo.c@},
34430 @{file=/home/bar.c,fullname=/home/bar.c@},
34431 @{file=gdb_could_not_find_fullpath.c@}]
34436 @subheading The @code{-file-list-shared-libraries} Command
34437 @findex -file-list-shared-libraries
34439 @subsubheading Synopsis
34442 -file-list-shared-libraries
34445 List the shared libraries in the program.
34447 @subsubheading @value{GDBN} Command
34449 The corresponding @value{GDBN} command is @samp{info shared}.
34451 @subsubheading Example
34455 @subheading The @code{-file-list-symbol-files} Command
34456 @findex -file-list-symbol-files
34458 @subsubheading Synopsis
34461 -file-list-symbol-files
34466 @subsubheading @value{GDBN} Command
34468 The corresponding @value{GDBN} command is @samp{info file} (part of it).
34470 @subsubheading Example
34475 @subheading The @code{-file-symbol-file} Command
34476 @findex -file-symbol-file
34478 @subsubheading Synopsis
34481 -file-symbol-file @var{file}
34484 Read symbol table info from the specified @var{file} argument. When
34485 used without arguments, clears @value{GDBN}'s symbol table info. No output is
34486 produced, except for a completion notification.
34488 @subsubheading @value{GDBN} Command
34490 The corresponding @value{GDBN} command is @samp{symbol-file}.
34492 @subsubheading Example
34496 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34502 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34503 @node GDB/MI Memory Overlay Commands
34504 @section @sc{gdb/mi} Memory Overlay Commands
34506 The memory overlay commands are not implemented.
34508 @c @subheading -overlay-auto
34510 @c @subheading -overlay-list-mapping-state
34512 @c @subheading -overlay-list-overlays
34514 @c @subheading -overlay-map
34516 @c @subheading -overlay-off
34518 @c @subheading -overlay-on
34520 @c @subheading -overlay-unmap
34522 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34523 @node GDB/MI Signal Handling Commands
34524 @section @sc{gdb/mi} Signal Handling Commands
34526 Signal handling commands are not implemented.
34528 @c @subheading -signal-handle
34530 @c @subheading -signal-list-handle-actions
34532 @c @subheading -signal-list-signal-types
34536 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34537 @node GDB/MI Target Manipulation
34538 @section @sc{gdb/mi} Target Manipulation Commands
34541 @subheading The @code{-target-attach} Command
34542 @findex -target-attach
34544 @subsubheading Synopsis
34547 -target-attach @var{pid} | @var{gid} | @var{file}
34550 Attach to a process @var{pid} or a file @var{file} outside of
34551 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
34552 group, the id previously returned by
34553 @samp{-list-thread-groups --available} must be used.
34555 @subsubheading @value{GDBN} Command
34557 The corresponding @value{GDBN} command is @samp{attach}.
34559 @subsubheading Example
34563 =thread-created,id="1"
34564 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
34570 @subheading The @code{-target-compare-sections} Command
34571 @findex -target-compare-sections
34573 @subsubheading Synopsis
34576 -target-compare-sections [ @var{section} ]
34579 Compare data of section @var{section} on target to the exec file.
34580 Without the argument, all sections are compared.
34582 @subsubheading @value{GDBN} Command
34584 The @value{GDBN} equivalent is @samp{compare-sections}.
34586 @subsubheading Example
34591 @subheading The @code{-target-detach} Command
34592 @findex -target-detach
34594 @subsubheading Synopsis
34597 -target-detach [ @var{pid} | @var{gid} ]
34600 Detach from the remote target which normally resumes its execution.
34601 If either @var{pid} or @var{gid} is specified, detaches from either
34602 the specified process, or specified thread group. There's no output.
34604 @subsubheading @value{GDBN} Command
34606 The corresponding @value{GDBN} command is @samp{detach}.
34608 @subsubheading Example
34618 @subheading The @code{-target-disconnect} Command
34619 @findex -target-disconnect
34621 @subsubheading Synopsis
34627 Disconnect from the remote target. There's no output and the target is
34628 generally not resumed.
34630 @subsubheading @value{GDBN} Command
34632 The corresponding @value{GDBN} command is @samp{disconnect}.
34634 @subsubheading Example
34644 @subheading The @code{-target-download} Command
34645 @findex -target-download
34647 @subsubheading Synopsis
34653 Loads the executable onto the remote target.
34654 It prints out an update message every half second, which includes the fields:
34658 The name of the section.
34660 The size of what has been sent so far for that section.
34662 The size of the section.
34664 The total size of what was sent so far (the current and the previous sections).
34666 The size of the overall executable to download.
34670 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
34671 @sc{gdb/mi} Output Syntax}).
34673 In addition, it prints the name and size of the sections, as they are
34674 downloaded. These messages include the following fields:
34678 The name of the section.
34680 The size of the section.
34682 The size of the overall executable to download.
34686 At the end, a summary is printed.
34688 @subsubheading @value{GDBN} Command
34690 The corresponding @value{GDBN} command is @samp{load}.
34692 @subsubheading Example
34694 Note: each status message appears on a single line. Here the messages
34695 have been broken down so that they can fit onto a page.
34700 +download,@{section=".text",section-size="6668",total-size="9880"@}
34701 +download,@{section=".text",section-sent="512",section-size="6668",
34702 total-sent="512",total-size="9880"@}
34703 +download,@{section=".text",section-sent="1024",section-size="6668",
34704 total-sent="1024",total-size="9880"@}
34705 +download,@{section=".text",section-sent="1536",section-size="6668",
34706 total-sent="1536",total-size="9880"@}
34707 +download,@{section=".text",section-sent="2048",section-size="6668",
34708 total-sent="2048",total-size="9880"@}
34709 +download,@{section=".text",section-sent="2560",section-size="6668",
34710 total-sent="2560",total-size="9880"@}
34711 +download,@{section=".text",section-sent="3072",section-size="6668",
34712 total-sent="3072",total-size="9880"@}
34713 +download,@{section=".text",section-sent="3584",section-size="6668",
34714 total-sent="3584",total-size="9880"@}
34715 +download,@{section=".text",section-sent="4096",section-size="6668",
34716 total-sent="4096",total-size="9880"@}
34717 +download,@{section=".text",section-sent="4608",section-size="6668",
34718 total-sent="4608",total-size="9880"@}
34719 +download,@{section=".text",section-sent="5120",section-size="6668",
34720 total-sent="5120",total-size="9880"@}
34721 +download,@{section=".text",section-sent="5632",section-size="6668",
34722 total-sent="5632",total-size="9880"@}
34723 +download,@{section=".text",section-sent="6144",section-size="6668",
34724 total-sent="6144",total-size="9880"@}
34725 +download,@{section=".text",section-sent="6656",section-size="6668",
34726 total-sent="6656",total-size="9880"@}
34727 +download,@{section=".init",section-size="28",total-size="9880"@}
34728 +download,@{section=".fini",section-size="28",total-size="9880"@}
34729 +download,@{section=".data",section-size="3156",total-size="9880"@}
34730 +download,@{section=".data",section-sent="512",section-size="3156",
34731 total-sent="7236",total-size="9880"@}
34732 +download,@{section=".data",section-sent="1024",section-size="3156",
34733 total-sent="7748",total-size="9880"@}
34734 +download,@{section=".data",section-sent="1536",section-size="3156",
34735 total-sent="8260",total-size="9880"@}
34736 +download,@{section=".data",section-sent="2048",section-size="3156",
34737 total-sent="8772",total-size="9880"@}
34738 +download,@{section=".data",section-sent="2560",section-size="3156",
34739 total-sent="9284",total-size="9880"@}
34740 +download,@{section=".data",section-sent="3072",section-size="3156",
34741 total-sent="9796",total-size="9880"@}
34742 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
34749 @subheading The @code{-target-exec-status} Command
34750 @findex -target-exec-status
34752 @subsubheading Synopsis
34755 -target-exec-status
34758 Provide information on the state of the target (whether it is running or
34759 not, for instance).
34761 @subsubheading @value{GDBN} Command
34763 There's no equivalent @value{GDBN} command.
34765 @subsubheading Example
34769 @subheading The @code{-target-list-available-targets} Command
34770 @findex -target-list-available-targets
34772 @subsubheading Synopsis
34775 -target-list-available-targets
34778 List the possible targets to connect to.
34780 @subsubheading @value{GDBN} Command
34782 The corresponding @value{GDBN} command is @samp{help target}.
34784 @subsubheading Example
34788 @subheading The @code{-target-list-current-targets} Command
34789 @findex -target-list-current-targets
34791 @subsubheading Synopsis
34794 -target-list-current-targets
34797 Describe the current target.
34799 @subsubheading @value{GDBN} Command
34801 The corresponding information is printed by @samp{info file} (among
34804 @subsubheading Example
34808 @subheading The @code{-target-list-parameters} Command
34809 @findex -target-list-parameters
34811 @subsubheading Synopsis
34814 -target-list-parameters
34820 @subsubheading @value{GDBN} Command
34824 @subsubheading Example
34828 @subheading The @code{-target-select} Command
34829 @findex -target-select
34831 @subsubheading Synopsis
34834 -target-select @var{type} @var{parameters @dots{}}
34837 Connect @value{GDBN} to the remote target. This command takes two args:
34841 The type of target, for instance @samp{remote}, etc.
34842 @item @var{parameters}
34843 Device names, host names and the like. @xref{Target Commands, ,
34844 Commands for Managing Targets}, for more details.
34847 The output is a connection notification, followed by the address at
34848 which the target program is, in the following form:
34851 ^connected,addr="@var{address}",func="@var{function name}",
34852 args=[@var{arg list}]
34855 @subsubheading @value{GDBN} Command
34857 The corresponding @value{GDBN} command is @samp{target}.
34859 @subsubheading Example
34863 -target-select remote /dev/ttya
34864 ^connected,addr="0xfe00a300",func="??",args=[]
34868 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34869 @node GDB/MI File Transfer Commands
34870 @section @sc{gdb/mi} File Transfer Commands
34873 @subheading The @code{-target-file-put} Command
34874 @findex -target-file-put
34876 @subsubheading Synopsis
34879 -target-file-put @var{hostfile} @var{targetfile}
34882 Copy file @var{hostfile} from the host system (the machine running
34883 @value{GDBN}) to @var{targetfile} on the target system.
34885 @subsubheading @value{GDBN} Command
34887 The corresponding @value{GDBN} command is @samp{remote put}.
34889 @subsubheading Example
34893 -target-file-put localfile remotefile
34899 @subheading The @code{-target-file-get} Command
34900 @findex -target-file-get
34902 @subsubheading Synopsis
34905 -target-file-get @var{targetfile} @var{hostfile}
34908 Copy file @var{targetfile} from the target system to @var{hostfile}
34909 on the host system.
34911 @subsubheading @value{GDBN} Command
34913 The corresponding @value{GDBN} command is @samp{remote get}.
34915 @subsubheading Example
34919 -target-file-get remotefile localfile
34925 @subheading The @code{-target-file-delete} Command
34926 @findex -target-file-delete
34928 @subsubheading Synopsis
34931 -target-file-delete @var{targetfile}
34934 Delete @var{targetfile} from the target system.
34936 @subsubheading @value{GDBN} Command
34938 The corresponding @value{GDBN} command is @samp{remote delete}.
34940 @subsubheading Example
34944 -target-file-delete remotefile
34950 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34951 @node GDB/MI Ada Exceptions Commands
34952 @section Ada Exceptions @sc{gdb/mi} Commands
34954 @subheading The @code{-info-ada-exceptions} Command
34955 @findex -info-ada-exceptions
34957 @subsubheading Synopsis
34960 -info-ada-exceptions [ @var{regexp}]
34963 List all Ada exceptions defined within the program being debugged.
34964 With a regular expression @var{regexp}, only those exceptions whose
34965 names match @var{regexp} are listed.
34967 @subsubheading @value{GDBN} Command
34969 The corresponding @value{GDBN} command is @samp{info exceptions}.
34971 @subsubheading Result
34973 The result is a table of Ada exceptions. The following columns are
34974 defined for each exception:
34978 The name of the exception.
34981 The address of the exception.
34985 @subsubheading Example
34988 -info-ada-exceptions aint
34989 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
34990 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
34991 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
34992 body=[@{name="constraint_error",address="0x0000000000613da0"@},
34993 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
34996 @subheading Catching Ada Exceptions
34998 The commands describing how to ask @value{GDBN} to stop when a program
34999 raises an exception are described at @ref{Ada Exception GDB/MI
35000 Catchpoint Commands}.
35003 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35004 @node GDB/MI Miscellaneous Commands
35005 @section Miscellaneous @sc{gdb/mi} Commands
35007 @c @subheading -gdb-complete
35009 @subheading The @code{-gdb-exit} Command
35012 @subsubheading Synopsis
35018 Exit @value{GDBN} immediately.
35020 @subsubheading @value{GDBN} Command
35022 Approximately corresponds to @samp{quit}.
35024 @subsubheading Example
35034 @subheading The @code{-exec-abort} Command
35035 @findex -exec-abort
35037 @subsubheading Synopsis
35043 Kill the inferior running program.
35045 @subsubheading @value{GDBN} Command
35047 The corresponding @value{GDBN} command is @samp{kill}.
35049 @subsubheading Example
35054 @subheading The @code{-gdb-set} Command
35057 @subsubheading Synopsis
35063 Set an internal @value{GDBN} variable.
35064 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
35066 @subsubheading @value{GDBN} Command
35068 The corresponding @value{GDBN} command is @samp{set}.
35070 @subsubheading Example
35080 @subheading The @code{-gdb-show} Command
35083 @subsubheading Synopsis
35089 Show the current value of a @value{GDBN} variable.
35091 @subsubheading @value{GDBN} Command
35093 The corresponding @value{GDBN} command is @samp{show}.
35095 @subsubheading Example
35104 @c @subheading -gdb-source
35107 @subheading The @code{-gdb-version} Command
35108 @findex -gdb-version
35110 @subsubheading Synopsis
35116 Show version information for @value{GDBN}. Used mostly in testing.
35118 @subsubheading @value{GDBN} Command
35120 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
35121 default shows this information when you start an interactive session.
35123 @subsubheading Example
35125 @c This example modifies the actual output from GDB to avoid overfull
35131 ~Copyright 2000 Free Software Foundation, Inc.
35132 ~GDB is free software, covered by the GNU General Public License, and
35133 ~you are welcome to change it and/or distribute copies of it under
35134 ~ certain conditions.
35135 ~Type "show copying" to see the conditions.
35136 ~There is absolutely no warranty for GDB. Type "show warranty" for
35138 ~This GDB was configured as
35139 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
35144 @subheading The @code{-info-gdb-mi-command} Command
35145 @cindex @code{-info-gdb-mi-command}
35146 @findex -info-gdb-mi-command
35148 @subsubheading Synopsis
35151 -info-gdb-mi-command @var{cmd_name}
35154 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
35156 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
35157 is technically not part of the command name (@pxref{GDB/MI Input
35158 Syntax}), and thus should be omitted in @var{cmd_name}. However,
35159 for ease of use, this command also accepts the form with the leading
35162 @subsubheading @value{GDBN} Command
35164 There is no corresponding @value{GDBN} command.
35166 @subsubheading Result
35168 The result is a tuple. There is currently only one field:
35172 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
35173 @code{"false"} otherwise.
35177 @subsubheading Example
35179 Here is an example where the @sc{gdb/mi} command does not exist:
35182 -info-gdb-mi-command unsupported-command
35183 ^done,command=@{exists="false"@}
35187 And here is an example where the @sc{gdb/mi} command is known
35191 -info-gdb-mi-command symbol-list-lines
35192 ^done,command=@{exists="true"@}
35195 @subheading The @code{-list-features} Command
35196 @findex -list-features
35198 Returns a list of particular features of the MI protocol that
35199 this version of gdb implements. A feature can be a command,
35200 or a new field in an output of some command, or even an
35201 important bugfix. While a frontend can sometimes detect presence
35202 of a feature at runtime, it is easier to perform detection at debugger
35205 The command returns a list of strings, with each string naming an
35206 available feature. Each returned string is just a name, it does not
35207 have any internal structure. The list of possible feature names
35213 (gdb) -list-features
35214 ^done,result=["feature1","feature2"]
35217 The current list of features is:
35220 @item frozen-varobjs
35221 Indicates support for the @code{-var-set-frozen} command, as well
35222 as possible presense of the @code{frozen} field in the output
35223 of @code{-varobj-create}.
35224 @item pending-breakpoints
35225 Indicates support for the @option{-f} option to the @code{-break-insert}
35228 Indicates Python scripting support, Python-based
35229 pretty-printing commands, and possible presence of the
35230 @samp{display_hint} field in the output of @code{-var-list-children}
35232 Indicates support for the @code{-thread-info} command.
35233 @item data-read-memory-bytes
35234 Indicates support for the @code{-data-read-memory-bytes} and the
35235 @code{-data-write-memory-bytes} commands.
35236 @item breakpoint-notifications
35237 Indicates that changes to breakpoints and breakpoints created via the
35238 CLI will be announced via async records.
35239 @item ada-task-info
35240 Indicates support for the @code{-ada-task-info} command.
35241 @item language-option
35242 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
35243 option (@pxref{Context management}).
35244 @item info-gdb-mi-command
35245 Indicates support for the @code{-info-gdb-mi-command} command.
35246 @item undefined-command-error-code
35247 Indicates support for the "undefined-command" error code in error result
35248 records, produced when trying to execute an undefined @sc{gdb/mi} command
35249 (@pxref{GDB/MI Result Records}).
35252 @subheading The @code{-list-target-features} Command
35253 @findex -list-target-features
35255 Returns a list of particular features that are supported by the
35256 target. Those features affect the permitted MI commands, but
35257 unlike the features reported by the @code{-list-features} command, the
35258 features depend on which target GDB is using at the moment. Whenever
35259 a target can change, due to commands such as @code{-target-select},
35260 @code{-target-attach} or @code{-exec-run}, the list of target features
35261 may change, and the frontend should obtain it again.
35265 (gdb) -list-target-features
35266 ^done,result=["async"]
35269 The current list of features is:
35273 Indicates that the target is capable of asynchronous command
35274 execution, which means that @value{GDBN} will accept further commands
35275 while the target is running.
35278 Indicates that the target is capable of reverse execution.
35279 @xref{Reverse Execution}, for more information.
35283 @subheading The @code{-list-thread-groups} Command
35284 @findex -list-thread-groups
35286 @subheading Synopsis
35289 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
35292 Lists thread groups (@pxref{Thread groups}). When a single thread
35293 group is passed as the argument, lists the children of that group.
35294 When several thread group are passed, lists information about those
35295 thread groups. Without any parameters, lists information about all
35296 top-level thread groups.
35298 Normally, thread groups that are being debugged are reported.
35299 With the @samp{--available} option, @value{GDBN} reports thread groups
35300 available on the target.
35302 The output of this command may have either a @samp{threads} result or
35303 a @samp{groups} result. The @samp{thread} result has a list of tuples
35304 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
35305 Information}). The @samp{groups} result has a list of tuples as value,
35306 each tuple describing a thread group. If top-level groups are
35307 requested (that is, no parameter is passed), or when several groups
35308 are passed, the output always has a @samp{groups} result. The format
35309 of the @samp{group} result is described below.
35311 To reduce the number of roundtrips it's possible to list thread groups
35312 together with their children, by passing the @samp{--recurse} option
35313 and the recursion depth. Presently, only recursion depth of 1 is
35314 permitted. If this option is present, then every reported thread group
35315 will also include its children, either as @samp{group} or
35316 @samp{threads} field.
35318 In general, any combination of option and parameters is permitted, with
35319 the following caveats:
35323 When a single thread group is passed, the output will typically
35324 be the @samp{threads} result. Because threads may not contain
35325 anything, the @samp{recurse} option will be ignored.
35328 When the @samp{--available} option is passed, limited information may
35329 be available. In particular, the list of threads of a process might
35330 be inaccessible. Further, specifying specific thread groups might
35331 not give any performance advantage over listing all thread groups.
35332 The frontend should assume that @samp{-list-thread-groups --available}
35333 is always an expensive operation and cache the results.
35337 The @samp{groups} result is a list of tuples, where each tuple may
35338 have the following fields:
35342 Identifier of the thread group. This field is always present.
35343 The identifier is an opaque string; frontends should not try to
35344 convert it to an integer, even though it might look like one.
35347 The type of the thread group. At present, only @samp{process} is a
35351 The target-specific process identifier. This field is only present
35352 for thread groups of type @samp{process} and only if the process exists.
35355 The number of children this thread group has. This field may be
35356 absent for an available thread group.
35359 This field has a list of tuples as value, each tuple describing a
35360 thread. It may be present if the @samp{--recurse} option is
35361 specified, and it's actually possible to obtain the threads.
35364 This field is a list of integers, each identifying a core that one
35365 thread of the group is running on. This field may be absent if
35366 such information is not available.
35369 The name of the executable file that corresponds to this thread group.
35370 The field is only present for thread groups of type @samp{process},
35371 and only if there is a corresponding executable file.
35375 @subheading Example
35379 -list-thread-groups
35380 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
35381 -list-thread-groups 17
35382 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
35383 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
35384 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
35385 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
35386 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
35387 -list-thread-groups --available
35388 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
35389 -list-thread-groups --available --recurse 1
35390 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35391 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35392 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
35393 -list-thread-groups --available --recurse 1 17 18
35394 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35395 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35396 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
35399 @subheading The @code{-info-os} Command
35402 @subsubheading Synopsis
35405 -info-os [ @var{type} ]
35408 If no argument is supplied, the command returns a table of available
35409 operating-system-specific information types. If one of these types is
35410 supplied as an argument @var{type}, then the command returns a table
35411 of data of that type.
35413 The types of information available depend on the target operating
35416 @subsubheading @value{GDBN} Command
35418 The corresponding @value{GDBN} command is @samp{info os}.
35420 @subsubheading Example
35422 When run on a @sc{gnu}/Linux system, the output will look something
35428 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
35429 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
35430 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
35431 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
35432 body=[item=@{col0="processes",col1="Listing of all processes",
35433 col2="Processes"@},
35434 item=@{col0="procgroups",col1="Listing of all process groups",
35435 col2="Process groups"@},
35436 item=@{col0="threads",col1="Listing of all threads",
35438 item=@{col0="files",col1="Listing of all file descriptors",
35439 col2="File descriptors"@},
35440 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
35442 item=@{col0="shm",col1="Listing of all shared-memory regions",
35443 col2="Shared-memory regions"@},
35444 item=@{col0="semaphores",col1="Listing of all semaphores",
35445 col2="Semaphores"@},
35446 item=@{col0="msg",col1="Listing of all message queues",
35447 col2="Message queues"@},
35448 item=@{col0="modules",col1="Listing of all loaded kernel modules",
35449 col2="Kernel modules"@}]@}
35452 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
35453 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
35454 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
35455 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
35456 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
35457 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
35458 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
35459 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
35461 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
35462 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
35466 (Note that the MI output here includes a @code{"Title"} column that
35467 does not appear in command-line @code{info os}; this column is useful
35468 for MI clients that want to enumerate the types of data, such as in a
35469 popup menu, but is needless clutter on the command line, and
35470 @code{info os} omits it.)
35472 @subheading The @code{-add-inferior} Command
35473 @findex -add-inferior
35475 @subheading Synopsis
35481 Creates a new inferior (@pxref{Inferiors and Programs}). The created
35482 inferior is not associated with any executable. Such association may
35483 be established with the @samp{-file-exec-and-symbols} command
35484 (@pxref{GDB/MI File Commands}). The command response has a single
35485 field, @samp{inferior}, whose value is the identifier of the
35486 thread group corresponding to the new inferior.
35488 @subheading Example
35493 ^done,inferior="i3"
35496 @subheading The @code{-interpreter-exec} Command
35497 @findex -interpreter-exec
35499 @subheading Synopsis
35502 -interpreter-exec @var{interpreter} @var{command}
35504 @anchor{-interpreter-exec}
35506 Execute the specified @var{command} in the given @var{interpreter}.
35508 @subheading @value{GDBN} Command
35510 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
35512 @subheading Example
35516 -interpreter-exec console "break main"
35517 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
35518 &"During symbol reading, bad structure-type format.\n"
35519 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
35524 @subheading The @code{-inferior-tty-set} Command
35525 @findex -inferior-tty-set
35527 @subheading Synopsis
35530 -inferior-tty-set /dev/pts/1
35533 Set terminal for future runs of the program being debugged.
35535 @subheading @value{GDBN} Command
35537 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
35539 @subheading Example
35543 -inferior-tty-set /dev/pts/1
35548 @subheading The @code{-inferior-tty-show} Command
35549 @findex -inferior-tty-show
35551 @subheading Synopsis
35557 Show terminal for future runs of program being debugged.
35559 @subheading @value{GDBN} Command
35561 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
35563 @subheading Example
35567 -inferior-tty-set /dev/pts/1
35571 ^done,inferior_tty_terminal="/dev/pts/1"
35575 @subheading The @code{-enable-timings} Command
35576 @findex -enable-timings
35578 @subheading Synopsis
35581 -enable-timings [yes | no]
35584 Toggle the printing of the wallclock, user and system times for an MI
35585 command as a field in its output. This command is to help frontend
35586 developers optimize the performance of their code. No argument is
35587 equivalent to @samp{yes}.
35589 @subheading @value{GDBN} Command
35593 @subheading Example
35601 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
35602 addr="0x080484ed",func="main",file="myprog.c",
35603 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
35605 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
35613 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
35614 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
35615 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
35616 fullname="/home/nickrob/myprog.c",line="73"@}
35621 @chapter @value{GDBN} Annotations
35623 This chapter describes annotations in @value{GDBN}. Annotations were
35624 designed to interface @value{GDBN} to graphical user interfaces or other
35625 similar programs which want to interact with @value{GDBN} at a
35626 relatively high level.
35628 The annotation mechanism has largely been superseded by @sc{gdb/mi}
35632 This is Edition @value{EDITION}, @value{DATE}.
35636 * Annotations Overview:: What annotations are; the general syntax.
35637 * Server Prefix:: Issuing a command without affecting user state.
35638 * Prompting:: Annotations marking @value{GDBN}'s need for input.
35639 * Errors:: Annotations for error messages.
35640 * Invalidation:: Some annotations describe things now invalid.
35641 * Annotations for Running::
35642 Whether the program is running, how it stopped, etc.
35643 * Source Annotations:: Annotations describing source code.
35646 @node Annotations Overview
35647 @section What is an Annotation?
35648 @cindex annotations
35650 Annotations start with a newline character, two @samp{control-z}
35651 characters, and the name of the annotation. If there is no additional
35652 information associated with this annotation, the name of the annotation
35653 is followed immediately by a newline. If there is additional
35654 information, the name of the annotation is followed by a space, the
35655 additional information, and a newline. The additional information
35656 cannot contain newline characters.
35658 Any output not beginning with a newline and two @samp{control-z}
35659 characters denotes literal output from @value{GDBN}. Currently there is
35660 no need for @value{GDBN} to output a newline followed by two
35661 @samp{control-z} characters, but if there was such a need, the
35662 annotations could be extended with an @samp{escape} annotation which
35663 means those three characters as output.
35665 The annotation @var{level}, which is specified using the
35666 @option{--annotate} command line option (@pxref{Mode Options}), controls
35667 how much information @value{GDBN} prints together with its prompt,
35668 values of expressions, source lines, and other types of output. Level 0
35669 is for no annotations, level 1 is for use when @value{GDBN} is run as a
35670 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
35671 for programs that control @value{GDBN}, and level 2 annotations have
35672 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
35673 Interface, annotate, GDB's Obsolete Annotations}).
35676 @kindex set annotate
35677 @item set annotate @var{level}
35678 The @value{GDBN} command @code{set annotate} sets the level of
35679 annotations to the specified @var{level}.
35681 @item show annotate
35682 @kindex show annotate
35683 Show the current annotation level.
35686 This chapter describes level 3 annotations.
35688 A simple example of starting up @value{GDBN} with annotations is:
35691 $ @kbd{gdb --annotate=3}
35693 Copyright 2003 Free Software Foundation, Inc.
35694 GDB is free software, covered by the GNU General Public License,
35695 and you are welcome to change it and/or distribute copies of it
35696 under certain conditions.
35697 Type "show copying" to see the conditions.
35698 There is absolutely no warranty for GDB. Type "show warranty"
35700 This GDB was configured as "i386-pc-linux-gnu"
35711 Here @samp{quit} is input to @value{GDBN}; the rest is output from
35712 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
35713 denotes a @samp{control-z} character) are annotations; the rest is
35714 output from @value{GDBN}.
35716 @node Server Prefix
35717 @section The Server Prefix
35718 @cindex server prefix
35720 If you prefix a command with @samp{server } then it will not affect
35721 the command history, nor will it affect @value{GDBN}'s notion of which
35722 command to repeat if @key{RET} is pressed on a line by itself. This
35723 means that commands can be run behind a user's back by a front-end in
35724 a transparent manner.
35726 The @code{server } prefix does not affect the recording of values into
35727 the value history; to print a value without recording it into the
35728 value history, use the @code{output} command instead of the
35729 @code{print} command.
35731 Using this prefix also disables confirmation requests
35732 (@pxref{confirmation requests}).
35735 @section Annotation for @value{GDBN} Input
35737 @cindex annotations for prompts
35738 When @value{GDBN} prompts for input, it annotates this fact so it is possible
35739 to know when to send output, when the output from a given command is
35742 Different kinds of input each have a different @dfn{input type}. Each
35743 input type has three annotations: a @code{pre-} annotation, which
35744 denotes the beginning of any prompt which is being output, a plain
35745 annotation, which denotes the end of the prompt, and then a @code{post-}
35746 annotation which denotes the end of any echo which may (or may not) be
35747 associated with the input. For example, the @code{prompt} input type
35748 features the following annotations:
35756 The input types are
35759 @findex pre-prompt annotation
35760 @findex prompt annotation
35761 @findex post-prompt annotation
35763 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
35765 @findex pre-commands annotation
35766 @findex commands annotation
35767 @findex post-commands annotation
35769 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
35770 command. The annotations are repeated for each command which is input.
35772 @findex pre-overload-choice annotation
35773 @findex overload-choice annotation
35774 @findex post-overload-choice annotation
35775 @item overload-choice
35776 When @value{GDBN} wants the user to select between various overloaded functions.
35778 @findex pre-query annotation
35779 @findex query annotation
35780 @findex post-query annotation
35782 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
35784 @findex pre-prompt-for-continue annotation
35785 @findex prompt-for-continue annotation
35786 @findex post-prompt-for-continue annotation
35787 @item prompt-for-continue
35788 When @value{GDBN} is asking the user to press return to continue. Note: Don't
35789 expect this to work well; instead use @code{set height 0} to disable
35790 prompting. This is because the counting of lines is buggy in the
35791 presence of annotations.
35796 @cindex annotations for errors, warnings and interrupts
35798 @findex quit annotation
35803 This annotation occurs right before @value{GDBN} responds to an interrupt.
35805 @findex error annotation
35810 This annotation occurs right before @value{GDBN} responds to an error.
35812 Quit and error annotations indicate that any annotations which @value{GDBN} was
35813 in the middle of may end abruptly. For example, if a
35814 @code{value-history-begin} annotation is followed by a @code{error}, one
35815 cannot expect to receive the matching @code{value-history-end}. One
35816 cannot expect not to receive it either, however; an error annotation
35817 does not necessarily mean that @value{GDBN} is immediately returning all the way
35820 @findex error-begin annotation
35821 A quit or error annotation may be preceded by
35827 Any output between that and the quit or error annotation is the error
35830 Warning messages are not yet annotated.
35831 @c If we want to change that, need to fix warning(), type_error(),
35832 @c range_error(), and possibly other places.
35835 @section Invalidation Notices
35837 @cindex annotations for invalidation messages
35838 The following annotations say that certain pieces of state may have
35842 @findex frames-invalid annotation
35843 @item ^Z^Zframes-invalid
35845 The frames (for example, output from the @code{backtrace} command) may
35848 @findex breakpoints-invalid annotation
35849 @item ^Z^Zbreakpoints-invalid
35851 The breakpoints may have changed. For example, the user just added or
35852 deleted a breakpoint.
35855 @node Annotations for Running
35856 @section Running the Program
35857 @cindex annotations for running programs
35859 @findex starting annotation
35860 @findex stopping annotation
35861 When the program starts executing due to a @value{GDBN} command such as
35862 @code{step} or @code{continue},
35868 is output. When the program stops,
35874 is output. Before the @code{stopped} annotation, a variety of
35875 annotations describe how the program stopped.
35878 @findex exited annotation
35879 @item ^Z^Zexited @var{exit-status}
35880 The program exited, and @var{exit-status} is the exit status (zero for
35881 successful exit, otherwise nonzero).
35883 @findex signalled annotation
35884 @findex signal-name annotation
35885 @findex signal-name-end annotation
35886 @findex signal-string annotation
35887 @findex signal-string-end annotation
35888 @item ^Z^Zsignalled
35889 The program exited with a signal. After the @code{^Z^Zsignalled}, the
35890 annotation continues:
35896 ^Z^Zsignal-name-end
35900 ^Z^Zsignal-string-end
35905 where @var{name} is the name of the signal, such as @code{SIGILL} or
35906 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
35907 as @code{Illegal Instruction} or @code{Segmentation fault}.
35908 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
35909 user's benefit and have no particular format.
35911 @findex signal annotation
35913 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
35914 just saying that the program received the signal, not that it was
35915 terminated with it.
35917 @findex breakpoint annotation
35918 @item ^Z^Zbreakpoint @var{number}
35919 The program hit breakpoint number @var{number}.
35921 @findex watchpoint annotation
35922 @item ^Z^Zwatchpoint @var{number}
35923 The program hit watchpoint number @var{number}.
35926 @node Source Annotations
35927 @section Displaying Source
35928 @cindex annotations for source display
35930 @findex source annotation
35931 The following annotation is used instead of displaying source code:
35934 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
35937 where @var{filename} is an absolute file name indicating which source
35938 file, @var{line} is the line number within that file (where 1 is the
35939 first line in the file), @var{character} is the character position
35940 within the file (where 0 is the first character in the file) (for most
35941 debug formats this will necessarily point to the beginning of a line),
35942 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
35943 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
35944 @var{addr} is the address in the target program associated with the
35945 source which is being displayed. @var{addr} is in the form @samp{0x}
35946 followed by one or more lowercase hex digits (note that this does not
35947 depend on the language).
35949 @node JIT Interface
35950 @chapter JIT Compilation Interface
35951 @cindex just-in-time compilation
35952 @cindex JIT compilation interface
35954 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
35955 interface. A JIT compiler is a program or library that generates native
35956 executable code at runtime and executes it, usually in order to achieve good
35957 performance while maintaining platform independence.
35959 Programs that use JIT compilation are normally difficult to debug because
35960 portions of their code are generated at runtime, instead of being loaded from
35961 object files, which is where @value{GDBN} normally finds the program's symbols
35962 and debug information. In order to debug programs that use JIT compilation,
35963 @value{GDBN} has an interface that allows the program to register in-memory
35964 symbol files with @value{GDBN} at runtime.
35966 If you are using @value{GDBN} to debug a program that uses this interface, then
35967 it should work transparently so long as you have not stripped the binary. If
35968 you are developing a JIT compiler, then the interface is documented in the rest
35969 of this chapter. At this time, the only known client of this interface is the
35972 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
35973 JIT compiler communicates with @value{GDBN} by writing data into a global
35974 variable and calling a fuction at a well-known symbol. When @value{GDBN}
35975 attaches, it reads a linked list of symbol files from the global variable to
35976 find existing code, and puts a breakpoint in the function so that it can find
35977 out about additional code.
35980 * Declarations:: Relevant C struct declarations
35981 * Registering Code:: Steps to register code
35982 * Unregistering Code:: Steps to unregister code
35983 * Custom Debug Info:: Emit debug information in a custom format
35987 @section JIT Declarations
35989 These are the relevant struct declarations that a C program should include to
35990 implement the interface:
36000 struct jit_code_entry
36002 struct jit_code_entry *next_entry;
36003 struct jit_code_entry *prev_entry;
36004 const char *symfile_addr;
36005 uint64_t symfile_size;
36008 struct jit_descriptor
36011 /* This type should be jit_actions_t, but we use uint32_t
36012 to be explicit about the bitwidth. */
36013 uint32_t action_flag;
36014 struct jit_code_entry *relevant_entry;
36015 struct jit_code_entry *first_entry;
36018 /* GDB puts a breakpoint in this function. */
36019 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
36021 /* Make sure to specify the version statically, because the
36022 debugger may check the version before we can set it. */
36023 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
36026 If the JIT is multi-threaded, then it is important that the JIT synchronize any
36027 modifications to this global data properly, which can easily be done by putting
36028 a global mutex around modifications to these structures.
36030 @node Registering Code
36031 @section Registering Code
36033 To register code with @value{GDBN}, the JIT should follow this protocol:
36037 Generate an object file in memory with symbols and other desired debug
36038 information. The file must include the virtual addresses of the sections.
36041 Create a code entry for the file, which gives the start and size of the symbol
36045 Add it to the linked list in the JIT descriptor.
36048 Point the relevant_entry field of the descriptor at the entry.
36051 Set @code{action_flag} to @code{JIT_REGISTER} and call
36052 @code{__jit_debug_register_code}.
36055 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
36056 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
36057 new code. However, the linked list must still be maintained in order to allow
36058 @value{GDBN} to attach to a running process and still find the symbol files.
36060 @node Unregistering Code
36061 @section Unregistering Code
36063 If code is freed, then the JIT should use the following protocol:
36067 Remove the code entry corresponding to the code from the linked list.
36070 Point the @code{relevant_entry} field of the descriptor at the code entry.
36073 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
36074 @code{__jit_debug_register_code}.
36077 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
36078 and the JIT will leak the memory used for the associated symbol files.
36080 @node Custom Debug Info
36081 @section Custom Debug Info
36082 @cindex custom JIT debug info
36083 @cindex JIT debug info reader
36085 Generating debug information in platform-native file formats (like ELF
36086 or COFF) may be an overkill for JIT compilers; especially if all the
36087 debug info is used for is displaying a meaningful backtrace. The
36088 issue can be resolved by having the JIT writers decide on a debug info
36089 format and also provide a reader that parses the debug info generated
36090 by the JIT compiler. This section gives a brief overview on writing
36091 such a parser. More specific details can be found in the source file
36092 @file{gdb/jit-reader.in}, which is also installed as a header at
36093 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
36095 The reader is implemented as a shared object (so this functionality is
36096 not available on platforms which don't allow loading shared objects at
36097 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
36098 @code{jit-reader-unload} are provided, to be used to load and unload
36099 the readers from a preconfigured directory. Once loaded, the shared
36100 object is used the parse the debug information emitted by the JIT
36104 * Using JIT Debug Info Readers:: How to use supplied readers correctly
36105 * Writing JIT Debug Info Readers:: Creating a debug-info reader
36108 @node Using JIT Debug Info Readers
36109 @subsection Using JIT Debug Info Readers
36110 @kindex jit-reader-load
36111 @kindex jit-reader-unload
36113 Readers can be loaded and unloaded using the @code{jit-reader-load}
36114 and @code{jit-reader-unload} commands.
36117 @item jit-reader-load @var{reader}
36118 Load the JIT reader named @var{reader}. @var{reader} is a shared
36119 object specified as either an absolute or a relative file name. In
36120 the latter case, @value{GDBN} will try to load the reader from a
36121 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
36122 system (here @var{libdir} is the system library directory, often
36123 @file{/usr/local/lib}).
36125 Only one reader can be active at a time; trying to load a second
36126 reader when one is already loaded will result in @value{GDBN}
36127 reporting an error. A new JIT reader can be loaded by first unloading
36128 the current one using @code{jit-reader-unload} and then invoking
36129 @code{jit-reader-load}.
36131 @item jit-reader-unload
36132 Unload the currently loaded JIT reader.
36136 @node Writing JIT Debug Info Readers
36137 @subsection Writing JIT Debug Info Readers
36138 @cindex writing JIT debug info readers
36140 As mentioned, a reader is essentially a shared object conforming to a
36141 certain ABI. This ABI is described in @file{jit-reader.h}.
36143 @file{jit-reader.h} defines the structures, macros and functions
36144 required to write a reader. It is installed (along with
36145 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
36146 the system include directory.
36148 Readers need to be released under a GPL compatible license. A reader
36149 can be declared as released under such a license by placing the macro
36150 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
36152 The entry point for readers is the symbol @code{gdb_init_reader},
36153 which is expected to be a function with the prototype
36155 @findex gdb_init_reader
36157 extern struct gdb_reader_funcs *gdb_init_reader (void);
36160 @cindex @code{struct gdb_reader_funcs}
36162 @code{struct gdb_reader_funcs} contains a set of pointers to callback
36163 functions. These functions are executed to read the debug info
36164 generated by the JIT compiler (@code{read}), to unwind stack frames
36165 (@code{unwind}) and to create canonical frame IDs
36166 (@code{get_Frame_id}). It also has a callback that is called when the
36167 reader is being unloaded (@code{destroy}). The struct looks like this
36170 struct gdb_reader_funcs
36172 /* Must be set to GDB_READER_INTERFACE_VERSION. */
36173 int reader_version;
36175 /* For use by the reader. */
36178 gdb_read_debug_info *read;
36179 gdb_unwind_frame *unwind;
36180 gdb_get_frame_id *get_frame_id;
36181 gdb_destroy_reader *destroy;
36185 @cindex @code{struct gdb_symbol_callbacks}
36186 @cindex @code{struct gdb_unwind_callbacks}
36188 The callbacks are provided with another set of callbacks by
36189 @value{GDBN} to do their job. For @code{read}, these callbacks are
36190 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
36191 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
36192 @code{struct gdb_symbol_callbacks} has callbacks to create new object
36193 files and new symbol tables inside those object files. @code{struct
36194 gdb_unwind_callbacks} has callbacks to read registers off the current
36195 frame and to write out the values of the registers in the previous
36196 frame. Both have a callback (@code{target_read}) to read bytes off the
36197 target's address space.
36199 @node In-Process Agent
36200 @chapter In-Process Agent
36201 @cindex debugging agent
36202 The traditional debugging model is conceptually low-speed, but works fine,
36203 because most bugs can be reproduced in debugging-mode execution. However,
36204 as multi-core or many-core processors are becoming mainstream, and
36205 multi-threaded programs become more and more popular, there should be more
36206 and more bugs that only manifest themselves at normal-mode execution, for
36207 example, thread races, because debugger's interference with the program's
36208 timing may conceal the bugs. On the other hand, in some applications,
36209 it is not feasible for the debugger to interrupt the program's execution
36210 long enough for the developer to learn anything helpful about its behavior.
36211 If the program's correctness depends on its real-time behavior, delays
36212 introduced by a debugger might cause the program to fail, even when the
36213 code itself is correct. It is useful to be able to observe the program's
36214 behavior without interrupting it.
36216 Therefore, traditional debugging model is too intrusive to reproduce
36217 some bugs. In order to reduce the interference with the program, we can
36218 reduce the number of operations performed by debugger. The
36219 @dfn{In-Process Agent}, a shared library, is running within the same
36220 process with inferior, and is able to perform some debugging operations
36221 itself. As a result, debugger is only involved when necessary, and
36222 performance of debugging can be improved accordingly. Note that
36223 interference with program can be reduced but can't be removed completely,
36224 because the in-process agent will still stop or slow down the program.
36226 The in-process agent can interpret and execute Agent Expressions
36227 (@pxref{Agent Expressions}) during performing debugging operations. The
36228 agent expressions can be used for different purposes, such as collecting
36229 data in tracepoints, and condition evaluation in breakpoints.
36231 @anchor{Control Agent}
36232 You can control whether the in-process agent is used as an aid for
36233 debugging with the following commands:
36236 @kindex set agent on
36238 Causes the in-process agent to perform some operations on behalf of the
36239 debugger. Just which operations requested by the user will be done
36240 by the in-process agent depends on the its capabilities. For example,
36241 if you request to evaluate breakpoint conditions in the in-process agent,
36242 and the in-process agent has such capability as well, then breakpoint
36243 conditions will be evaluated in the in-process agent.
36245 @kindex set agent off
36246 @item set agent off
36247 Disables execution of debugging operations by the in-process agent. All
36248 of the operations will be performed by @value{GDBN}.
36252 Display the current setting of execution of debugging operations by
36253 the in-process agent.
36257 * In-Process Agent Protocol::
36260 @node In-Process Agent Protocol
36261 @section In-Process Agent Protocol
36262 @cindex in-process agent protocol
36264 The in-process agent is able to communicate with both @value{GDBN} and
36265 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
36266 used for communications between @value{GDBN} or GDBserver and the IPA.
36267 In general, @value{GDBN} or GDBserver sends commands
36268 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
36269 in-process agent replies back with the return result of the command, or
36270 some other information. The data sent to in-process agent is composed
36271 of primitive data types, such as 4-byte or 8-byte type, and composite
36272 types, which are called objects (@pxref{IPA Protocol Objects}).
36275 * IPA Protocol Objects::
36276 * IPA Protocol Commands::
36279 @node IPA Protocol Objects
36280 @subsection IPA Protocol Objects
36281 @cindex ipa protocol objects
36283 The commands sent to and results received from agent may contain some
36284 complex data types called @dfn{objects}.
36286 The in-process agent is running on the same machine with @value{GDBN}
36287 or GDBserver, so it doesn't have to handle as much differences between
36288 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
36289 However, there are still some differences of two ends in two processes:
36293 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
36294 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
36296 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
36297 GDBserver is compiled with one, and in-process agent is compiled with
36301 Here are the IPA Protocol Objects:
36305 agent expression object. It represents an agent expression
36306 (@pxref{Agent Expressions}).
36307 @anchor{agent expression object}
36309 tracepoint action object. It represents a tracepoint action
36310 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
36311 memory, static trace data and to evaluate expression.
36312 @anchor{tracepoint action object}
36314 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
36315 @anchor{tracepoint object}
36319 The following table describes important attributes of each IPA protocol
36322 @multitable @columnfractions .30 .20 .50
36323 @headitem Name @tab Size @tab Description
36324 @item @emph{agent expression object} @tab @tab
36325 @item length @tab 4 @tab length of bytes code
36326 @item byte code @tab @var{length} @tab contents of byte code
36327 @item @emph{tracepoint action for collecting memory} @tab @tab
36328 @item 'M' @tab 1 @tab type of tracepoint action
36329 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
36330 address of the lowest byte to collect, otherwise @var{addr} is the offset
36331 of @var{basereg} for memory collecting.
36332 @item len @tab 8 @tab length of memory for collecting
36333 @item basereg @tab 4 @tab the register number containing the starting
36334 memory address for collecting.
36335 @item @emph{tracepoint action for collecting registers} @tab @tab
36336 @item 'R' @tab 1 @tab type of tracepoint action
36337 @item @emph{tracepoint action for collecting static trace data} @tab @tab
36338 @item 'L' @tab 1 @tab type of tracepoint action
36339 @item @emph{tracepoint action for expression evaluation} @tab @tab
36340 @item 'X' @tab 1 @tab type of tracepoint action
36341 @item agent expression @tab length of @tab @ref{agent expression object}
36342 @item @emph{tracepoint object} @tab @tab
36343 @item number @tab 4 @tab number of tracepoint
36344 @item address @tab 8 @tab address of tracepoint inserted on
36345 @item type @tab 4 @tab type of tracepoint
36346 @item enabled @tab 1 @tab enable or disable of tracepoint
36347 @item step_count @tab 8 @tab step
36348 @item pass_count @tab 8 @tab pass
36349 @item numactions @tab 4 @tab number of tracepoint actions
36350 @item hit count @tab 8 @tab hit count
36351 @item trace frame usage @tab 8 @tab trace frame usage
36352 @item compiled_cond @tab 8 @tab compiled condition
36353 @item orig_size @tab 8 @tab orig size
36354 @item condition @tab 4 if condition is NULL otherwise length of
36355 @ref{agent expression object}
36356 @tab zero if condition is NULL, otherwise is
36357 @ref{agent expression object}
36358 @item actions @tab variable
36359 @tab numactions number of @ref{tracepoint action object}
36362 @node IPA Protocol Commands
36363 @subsection IPA Protocol Commands
36364 @cindex ipa protocol commands
36366 The spaces in each command are delimiters to ease reading this commands
36367 specification. They don't exist in real commands.
36371 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
36372 Installs a new fast tracepoint described by @var{tracepoint_object}
36373 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
36374 head of @dfn{jumppad}, which is used to jump to data collection routine
36379 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
36380 @var{target_address} is address of tracepoint in the inferior.
36381 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
36382 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
36383 @var{fjump} contains a sequence of instructions jump to jumppad entry.
36384 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
36391 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
36392 is about to kill inferiors.
36400 @item probe_marker_at:@var{address}
36401 Asks in-process agent to probe the marker at @var{address}.
36408 @item unprobe_marker_at:@var{address}
36409 Asks in-process agent to unprobe the marker at @var{address}.
36413 @chapter Reporting Bugs in @value{GDBN}
36414 @cindex bugs in @value{GDBN}
36415 @cindex reporting bugs in @value{GDBN}
36417 Your bug reports play an essential role in making @value{GDBN} reliable.
36419 Reporting a bug may help you by bringing a solution to your problem, or it
36420 may not. But in any case the principal function of a bug report is to help
36421 the entire community by making the next version of @value{GDBN} work better. Bug
36422 reports are your contribution to the maintenance of @value{GDBN}.
36424 In order for a bug report to serve its purpose, you must include the
36425 information that enables us to fix the bug.
36428 * Bug Criteria:: Have you found a bug?
36429 * Bug Reporting:: How to report bugs
36433 @section Have You Found a Bug?
36434 @cindex bug criteria
36436 If you are not sure whether you have found a bug, here are some guidelines:
36439 @cindex fatal signal
36440 @cindex debugger crash
36441 @cindex crash of debugger
36443 If the debugger gets a fatal signal, for any input whatever, that is a
36444 @value{GDBN} bug. Reliable debuggers never crash.
36446 @cindex error on valid input
36448 If @value{GDBN} produces an error message for valid input, that is a
36449 bug. (Note that if you're cross debugging, the problem may also be
36450 somewhere in the connection to the target.)
36452 @cindex invalid input
36454 If @value{GDBN} does not produce an error message for invalid input,
36455 that is a bug. However, you should note that your idea of
36456 ``invalid input'' might be our idea of ``an extension'' or ``support
36457 for traditional practice''.
36460 If you are an experienced user of debugging tools, your suggestions
36461 for improvement of @value{GDBN} are welcome in any case.
36464 @node Bug Reporting
36465 @section How to Report Bugs
36466 @cindex bug reports
36467 @cindex @value{GDBN} bugs, reporting
36469 A number of companies and individuals offer support for @sc{gnu} products.
36470 If you obtained @value{GDBN} from a support organization, we recommend you
36471 contact that organization first.
36473 You can find contact information for many support companies and
36474 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
36476 @c should add a web page ref...
36479 @ifset BUGURL_DEFAULT
36480 In any event, we also recommend that you submit bug reports for
36481 @value{GDBN}. The preferred method is to submit them directly using
36482 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
36483 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
36486 @strong{Do not send bug reports to @samp{info-gdb}, or to
36487 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
36488 not want to receive bug reports. Those that do have arranged to receive
36491 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
36492 serves as a repeater. The mailing list and the newsgroup carry exactly
36493 the same messages. Often people think of posting bug reports to the
36494 newsgroup instead of mailing them. This appears to work, but it has one
36495 problem which can be crucial: a newsgroup posting often lacks a mail
36496 path back to the sender. Thus, if we need to ask for more information,
36497 we may be unable to reach you. For this reason, it is better to send
36498 bug reports to the mailing list.
36500 @ifclear BUGURL_DEFAULT
36501 In any event, we also recommend that you submit bug reports for
36502 @value{GDBN} to @value{BUGURL}.
36506 The fundamental principle of reporting bugs usefully is this:
36507 @strong{report all the facts}. If you are not sure whether to state a
36508 fact or leave it out, state it!
36510 Often people omit facts because they think they know what causes the
36511 problem and assume that some details do not matter. Thus, you might
36512 assume that the name of the variable you use in an example does not matter.
36513 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
36514 stray memory reference which happens to fetch from the location where that
36515 name is stored in memory; perhaps, if the name were different, the contents
36516 of that location would fool the debugger into doing the right thing despite
36517 the bug. Play it safe and give a specific, complete example. That is the
36518 easiest thing for you to do, and the most helpful.
36520 Keep in mind that the purpose of a bug report is to enable us to fix the
36521 bug. It may be that the bug has been reported previously, but neither
36522 you nor we can know that unless your bug report is complete and
36525 Sometimes people give a few sketchy facts and ask, ``Does this ring a
36526 bell?'' Those bug reports are useless, and we urge everyone to
36527 @emph{refuse to respond to them} except to chide the sender to report
36530 To enable us to fix the bug, you should include all these things:
36534 The version of @value{GDBN}. @value{GDBN} announces it if you start
36535 with no arguments; you can also print it at any time using @code{show
36538 Without this, we will not know whether there is any point in looking for
36539 the bug in the current version of @value{GDBN}.
36542 The type of machine you are using, and the operating system name and
36546 The details of the @value{GDBN} build-time configuration.
36547 @value{GDBN} shows these details if you invoke it with the
36548 @option{--configuration} command-line option, or if you type
36549 @code{show configuration} at @value{GDBN}'s prompt.
36552 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
36553 ``@value{GCC}--2.8.1''.
36556 What compiler (and its version) was used to compile the program you are
36557 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
36558 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
36559 to get this information; for other compilers, see the documentation for
36563 The command arguments you gave the compiler to compile your example and
36564 observe the bug. For example, did you use @samp{-O}? To guarantee
36565 you will not omit something important, list them all. A copy of the
36566 Makefile (or the output from make) is sufficient.
36568 If we were to try to guess the arguments, we would probably guess wrong
36569 and then we might not encounter the bug.
36572 A complete input script, and all necessary source files, that will
36576 A description of what behavior you observe that you believe is
36577 incorrect. For example, ``It gets a fatal signal.''
36579 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
36580 will certainly notice it. But if the bug is incorrect output, we might
36581 not notice unless it is glaringly wrong. You might as well not give us
36582 a chance to make a mistake.
36584 Even if the problem you experience is a fatal signal, you should still
36585 say so explicitly. Suppose something strange is going on, such as, your
36586 copy of @value{GDBN} is out of synch, or you have encountered a bug in
36587 the C library on your system. (This has happened!) Your copy might
36588 crash and ours would not. If you told us to expect a crash, then when
36589 ours fails to crash, we would know that the bug was not happening for
36590 us. If you had not told us to expect a crash, then we would not be able
36591 to draw any conclusion from our observations.
36594 @cindex recording a session script
36595 To collect all this information, you can use a session recording program
36596 such as @command{script}, which is available on many Unix systems.
36597 Just run your @value{GDBN} session inside @command{script} and then
36598 include the @file{typescript} file with your bug report.
36600 Another way to record a @value{GDBN} session is to run @value{GDBN}
36601 inside Emacs and then save the entire buffer to a file.
36604 If you wish to suggest changes to the @value{GDBN} source, send us context
36605 diffs. If you even discuss something in the @value{GDBN} source, refer to
36606 it by context, not by line number.
36608 The line numbers in our development sources will not match those in your
36609 sources. Your line numbers would convey no useful information to us.
36613 Here are some things that are not necessary:
36617 A description of the envelope of the bug.
36619 Often people who encounter a bug spend a lot of time investigating
36620 which changes to the input file will make the bug go away and which
36621 changes will not affect it.
36623 This is often time consuming and not very useful, because the way we
36624 will find the bug is by running a single example under the debugger
36625 with breakpoints, not by pure deduction from a series of examples.
36626 We recommend that you save your time for something else.
36628 Of course, if you can find a simpler example to report @emph{instead}
36629 of the original one, that is a convenience for us. Errors in the
36630 output will be easier to spot, running under the debugger will take
36631 less time, and so on.
36633 However, simplification is not vital; if you do not want to do this,
36634 report the bug anyway and send us the entire test case you used.
36637 A patch for the bug.
36639 A patch for the bug does help us if it is a good one. But do not omit
36640 the necessary information, such as the test case, on the assumption that
36641 a patch is all we need. We might see problems with your patch and decide
36642 to fix the problem another way, or we might not understand it at all.
36644 Sometimes with a program as complicated as @value{GDBN} it is very hard to
36645 construct an example that will make the program follow a certain path
36646 through the code. If you do not send us the example, we will not be able
36647 to construct one, so we will not be able to verify that the bug is fixed.
36649 And if we cannot understand what bug you are trying to fix, or why your
36650 patch should be an improvement, we will not install it. A test case will
36651 help us to understand.
36654 A guess about what the bug is or what it depends on.
36656 Such guesses are usually wrong. Even we cannot guess right about such
36657 things without first using the debugger to find the facts.
36660 @c The readline documentation is distributed with the readline code
36661 @c and consists of the two following files:
36664 @c Use -I with makeinfo to point to the appropriate directory,
36665 @c environment var TEXINPUTS with TeX.
36666 @ifclear SYSTEM_READLINE
36667 @include rluser.texi
36668 @include hsuser.texi
36672 @appendix In Memoriam
36674 The @value{GDBN} project mourns the loss of the following long-time
36679 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
36680 to Free Software in general. Outside of @value{GDBN}, he was known in
36681 the Amiga world for his series of Fish Disks, and the GeekGadget project.
36683 @item Michael Snyder
36684 Michael was one of the Global Maintainers of the @value{GDBN} project,
36685 with contributions recorded as early as 1996, until 2011. In addition
36686 to his day to day participation, he was a large driving force behind
36687 adding Reverse Debugging to @value{GDBN}.
36690 Beyond their technical contributions to the project, they were also
36691 enjoyable members of the Free Software Community. We will miss them.
36693 @node Formatting Documentation
36694 @appendix Formatting Documentation
36696 @cindex @value{GDBN} reference card
36697 @cindex reference card
36698 The @value{GDBN} 4 release includes an already-formatted reference card, ready
36699 for printing with PostScript or Ghostscript, in the @file{gdb}
36700 subdirectory of the main source directory@footnote{In
36701 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
36702 release.}. If you can use PostScript or Ghostscript with your printer,
36703 you can print the reference card immediately with @file{refcard.ps}.
36705 The release also includes the source for the reference card. You
36706 can format it, using @TeX{}, by typing:
36712 The @value{GDBN} reference card is designed to print in @dfn{landscape}
36713 mode on US ``letter'' size paper;
36714 that is, on a sheet 11 inches wide by 8.5 inches
36715 high. You will need to specify this form of printing as an option to
36716 your @sc{dvi} output program.
36718 @cindex documentation
36720 All the documentation for @value{GDBN} comes as part of the machine-readable
36721 distribution. The documentation is written in Texinfo format, which is
36722 a documentation system that uses a single source file to produce both
36723 on-line information and a printed manual. You can use one of the Info
36724 formatting commands to create the on-line version of the documentation
36725 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
36727 @value{GDBN} includes an already formatted copy of the on-line Info
36728 version of this manual in the @file{gdb} subdirectory. The main Info
36729 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
36730 subordinate files matching @samp{gdb.info*} in the same directory. If
36731 necessary, you can print out these files, or read them with any editor;
36732 but they are easier to read using the @code{info} subsystem in @sc{gnu}
36733 Emacs or the standalone @code{info} program, available as part of the
36734 @sc{gnu} Texinfo distribution.
36736 If you want to format these Info files yourself, you need one of the
36737 Info formatting programs, such as @code{texinfo-format-buffer} or
36740 If you have @code{makeinfo} installed, and are in the top level
36741 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
36742 version @value{GDBVN}), you can make the Info file by typing:
36749 If you want to typeset and print copies of this manual, you need @TeX{},
36750 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
36751 Texinfo definitions file.
36753 @TeX{} is a typesetting program; it does not print files directly, but
36754 produces output files called @sc{dvi} files. To print a typeset
36755 document, you need a program to print @sc{dvi} files. If your system
36756 has @TeX{} installed, chances are it has such a program. The precise
36757 command to use depends on your system; @kbd{lpr -d} is common; another
36758 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
36759 require a file name without any extension or a @samp{.dvi} extension.
36761 @TeX{} also requires a macro definitions file called
36762 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
36763 written in Texinfo format. On its own, @TeX{} cannot either read or
36764 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
36765 and is located in the @file{gdb-@var{version-number}/texinfo}
36768 If you have @TeX{} and a @sc{dvi} printer program installed, you can
36769 typeset and print this manual. First switch to the @file{gdb}
36770 subdirectory of the main source directory (for example, to
36771 @file{gdb-@value{GDBVN}/gdb}) and type:
36777 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
36779 @node Installing GDB
36780 @appendix Installing @value{GDBN}
36781 @cindex installation
36784 * Requirements:: Requirements for building @value{GDBN}
36785 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
36786 * Separate Objdir:: Compiling @value{GDBN} in another directory
36787 * Config Names:: Specifying names for hosts and targets
36788 * Configure Options:: Summary of options for configure
36789 * System-wide configuration:: Having a system-wide init file
36793 @section Requirements for Building @value{GDBN}
36794 @cindex building @value{GDBN}, requirements for
36796 Building @value{GDBN} requires various tools and packages to be available.
36797 Other packages will be used only if they are found.
36799 @heading Tools/Packages Necessary for Building @value{GDBN}
36801 @item ISO C90 compiler
36802 @value{GDBN} is written in ISO C90. It should be buildable with any
36803 working C90 compiler, e.g.@: GCC.
36807 @heading Tools/Packages Optional for Building @value{GDBN}
36811 @value{GDBN} can use the Expat XML parsing library. This library may be
36812 included with your operating system distribution; if it is not, you
36813 can get the latest version from @url{http://expat.sourceforge.net}.
36814 The @file{configure} script will search for this library in several
36815 standard locations; if it is installed in an unusual path, you can
36816 use the @option{--with-libexpat-prefix} option to specify its location.
36822 Remote protocol memory maps (@pxref{Memory Map Format})
36824 Target descriptions (@pxref{Target Descriptions})
36826 Remote shared library lists (@xref{Library List Format},
36827 or alternatively @pxref{Library List Format for SVR4 Targets})
36829 MS-Windows shared libraries (@pxref{Shared Libraries})
36831 Traceframe info (@pxref{Traceframe Info Format})
36833 Branch trace (@pxref{Branch Trace Format})
36837 @cindex compressed debug sections
36838 @value{GDBN} will use the @samp{zlib} library, if available, to read
36839 compressed debug sections. Some linkers, such as GNU gold, are capable
36840 of producing binaries with compressed debug sections. If @value{GDBN}
36841 is compiled with @samp{zlib}, it will be able to read the debug
36842 information in such binaries.
36844 The @samp{zlib} library is likely included with your operating system
36845 distribution; if it is not, you can get the latest version from
36846 @url{http://zlib.net}.
36849 @value{GDBN}'s features related to character sets (@pxref{Character
36850 Sets}) require a functioning @code{iconv} implementation. If you are
36851 on a GNU system, then this is provided by the GNU C Library. Some
36852 other systems also provide a working @code{iconv}.
36854 If @value{GDBN} is using the @code{iconv} program which is installed
36855 in a non-standard place, you will need to tell @value{GDBN} where to find it.
36856 This is done with @option{--with-iconv-bin} which specifies the
36857 directory that contains the @code{iconv} program.
36859 On systems without @code{iconv}, you can install GNU Libiconv. If you
36860 have previously installed Libiconv, you can use the
36861 @option{--with-libiconv-prefix} option to configure.
36863 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
36864 arrange to build Libiconv if a directory named @file{libiconv} appears
36865 in the top-most source directory. If Libiconv is built this way, and
36866 if the operating system does not provide a suitable @code{iconv}
36867 implementation, then the just-built library will automatically be used
36868 by @value{GDBN}. One easy way to set this up is to download GNU
36869 Libiconv, unpack it, and then rename the directory holding the
36870 Libiconv source code to @samp{libiconv}.
36873 @node Running Configure
36874 @section Invoking the @value{GDBN} @file{configure} Script
36875 @cindex configuring @value{GDBN}
36876 @value{GDBN} comes with a @file{configure} script that automates the process
36877 of preparing @value{GDBN} for installation; you can then use @code{make} to
36878 build the @code{gdb} program.
36880 @c irrelevant in info file; it's as current as the code it lives with.
36881 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
36882 look at the @file{README} file in the sources; we may have improved the
36883 installation procedures since publishing this manual.}
36886 The @value{GDBN} distribution includes all the source code you need for
36887 @value{GDBN} in a single directory, whose name is usually composed by
36888 appending the version number to @samp{gdb}.
36890 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
36891 @file{gdb-@value{GDBVN}} directory. That directory contains:
36894 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
36895 script for configuring @value{GDBN} and all its supporting libraries
36897 @item gdb-@value{GDBVN}/gdb
36898 the source specific to @value{GDBN} itself
36900 @item gdb-@value{GDBVN}/bfd
36901 source for the Binary File Descriptor library
36903 @item gdb-@value{GDBVN}/include
36904 @sc{gnu} include files
36906 @item gdb-@value{GDBVN}/libiberty
36907 source for the @samp{-liberty} free software library
36909 @item gdb-@value{GDBVN}/opcodes
36910 source for the library of opcode tables and disassemblers
36912 @item gdb-@value{GDBVN}/readline
36913 source for the @sc{gnu} command-line interface
36915 @item gdb-@value{GDBVN}/glob
36916 source for the @sc{gnu} filename pattern-matching subroutine
36918 @item gdb-@value{GDBVN}/mmalloc
36919 source for the @sc{gnu} memory-mapped malloc package
36922 The simplest way to configure and build @value{GDBN} is to run @file{configure}
36923 from the @file{gdb-@var{version-number}} source directory, which in
36924 this example is the @file{gdb-@value{GDBVN}} directory.
36926 First switch to the @file{gdb-@var{version-number}} source directory
36927 if you are not already in it; then run @file{configure}. Pass the
36928 identifier for the platform on which @value{GDBN} will run as an
36934 cd gdb-@value{GDBVN}
36935 ./configure @var{host}
36940 where @var{host} is an identifier such as @samp{sun4} or
36941 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
36942 (You can often leave off @var{host}; @file{configure} tries to guess the
36943 correct value by examining your system.)
36945 Running @samp{configure @var{host}} and then running @code{make} builds the
36946 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
36947 libraries, then @code{gdb} itself. The configured source files, and the
36948 binaries, are left in the corresponding source directories.
36951 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
36952 system does not recognize this automatically when you run a different
36953 shell, you may need to run @code{sh} on it explicitly:
36956 sh configure @var{host}
36959 If you run @file{configure} from a directory that contains source
36960 directories for multiple libraries or programs, such as the
36961 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
36963 creates configuration files for every directory level underneath (unless
36964 you tell it not to, with the @samp{--norecursion} option).
36966 You should run the @file{configure} script from the top directory in the
36967 source tree, the @file{gdb-@var{version-number}} directory. If you run
36968 @file{configure} from one of the subdirectories, you will configure only
36969 that subdirectory. That is usually not what you want. In particular,
36970 if you run the first @file{configure} from the @file{gdb} subdirectory
36971 of the @file{gdb-@var{version-number}} directory, you will omit the
36972 configuration of @file{bfd}, @file{readline}, and other sibling
36973 directories of the @file{gdb} subdirectory. This leads to build errors
36974 about missing include files such as @file{bfd/bfd.h}.
36976 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
36977 However, you should make sure that the shell on your path (named by
36978 the @samp{SHELL} environment variable) is publicly readable. Remember
36979 that @value{GDBN} uses the shell to start your program---some systems refuse to
36980 let @value{GDBN} debug child processes whose programs are not readable.
36982 @node Separate Objdir
36983 @section Compiling @value{GDBN} in Another Directory
36985 If you want to run @value{GDBN} versions for several host or target machines,
36986 you need a different @code{gdb} compiled for each combination of
36987 host and target. @file{configure} is designed to make this easy by
36988 allowing you to generate each configuration in a separate subdirectory,
36989 rather than in the source directory. If your @code{make} program
36990 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
36991 @code{make} in each of these directories builds the @code{gdb}
36992 program specified there.
36994 To build @code{gdb} in a separate directory, run @file{configure}
36995 with the @samp{--srcdir} option to specify where to find the source.
36996 (You also need to specify a path to find @file{configure}
36997 itself from your working directory. If the path to @file{configure}
36998 would be the same as the argument to @samp{--srcdir}, you can leave out
36999 the @samp{--srcdir} option; it is assumed.)
37001 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
37002 separate directory for a Sun 4 like this:
37006 cd gdb-@value{GDBVN}
37009 ../gdb-@value{GDBVN}/configure sun4
37014 When @file{configure} builds a configuration using a remote source
37015 directory, it creates a tree for the binaries with the same structure
37016 (and using the same names) as the tree under the source directory. In
37017 the example, you'd find the Sun 4 library @file{libiberty.a} in the
37018 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
37019 @file{gdb-sun4/gdb}.
37021 Make sure that your path to the @file{configure} script has just one
37022 instance of @file{gdb} in it. If your path to @file{configure} looks
37023 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
37024 one subdirectory of @value{GDBN}, not the whole package. This leads to
37025 build errors about missing include files such as @file{bfd/bfd.h}.
37027 One popular reason to build several @value{GDBN} configurations in separate
37028 directories is to configure @value{GDBN} for cross-compiling (where
37029 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
37030 programs that run on another machine---the @dfn{target}).
37031 You specify a cross-debugging target by
37032 giving the @samp{--target=@var{target}} option to @file{configure}.
37034 When you run @code{make} to build a program or library, you must run
37035 it in a configured directory---whatever directory you were in when you
37036 called @file{configure} (or one of its subdirectories).
37038 The @code{Makefile} that @file{configure} generates in each source
37039 directory also runs recursively. If you type @code{make} in a source
37040 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
37041 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
37042 will build all the required libraries, and then build GDB.
37044 When you have multiple hosts or targets configured in separate
37045 directories, you can run @code{make} on them in parallel (for example,
37046 if they are NFS-mounted on each of the hosts); they will not interfere
37050 @section Specifying Names for Hosts and Targets
37052 The specifications used for hosts and targets in the @file{configure}
37053 script are based on a three-part naming scheme, but some short predefined
37054 aliases are also supported. The full naming scheme encodes three pieces
37055 of information in the following pattern:
37058 @var{architecture}-@var{vendor}-@var{os}
37061 For example, you can use the alias @code{sun4} as a @var{host} argument,
37062 or as the value for @var{target} in a @code{--target=@var{target}}
37063 option. The equivalent full name is @samp{sparc-sun-sunos4}.
37065 The @file{configure} script accompanying @value{GDBN} does not provide
37066 any query facility to list all supported host and target names or
37067 aliases. @file{configure} calls the Bourne shell script
37068 @code{config.sub} to map abbreviations to full names; you can read the
37069 script, if you wish, or you can use it to test your guesses on
37070 abbreviations---for example:
37073 % sh config.sub i386-linux
37075 % sh config.sub alpha-linux
37076 alpha-unknown-linux-gnu
37077 % sh config.sub hp9k700
37079 % sh config.sub sun4
37080 sparc-sun-sunos4.1.1
37081 % sh config.sub sun3
37082 m68k-sun-sunos4.1.1
37083 % sh config.sub i986v
37084 Invalid configuration `i986v': machine `i986v' not recognized
37088 @code{config.sub} is also distributed in the @value{GDBN} source
37089 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
37091 @node Configure Options
37092 @section @file{configure} Options
37094 Here is a summary of the @file{configure} options and arguments that
37095 are most often useful for building @value{GDBN}. @file{configure} also has
37096 several other options not listed here. @inforef{What Configure
37097 Does,,configure.info}, for a full explanation of @file{configure}.
37100 configure @r{[}--help@r{]}
37101 @r{[}--prefix=@var{dir}@r{]}
37102 @r{[}--exec-prefix=@var{dir}@r{]}
37103 @r{[}--srcdir=@var{dirname}@r{]}
37104 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
37105 @r{[}--target=@var{target}@r{]}
37110 You may introduce options with a single @samp{-} rather than
37111 @samp{--} if you prefer; but you may abbreviate option names if you use
37116 Display a quick summary of how to invoke @file{configure}.
37118 @item --prefix=@var{dir}
37119 Configure the source to install programs and files under directory
37122 @item --exec-prefix=@var{dir}
37123 Configure the source to install programs under directory
37126 @c avoid splitting the warning from the explanation:
37128 @item --srcdir=@var{dirname}
37129 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
37130 @code{make} that implements the @code{VPATH} feature.}@*
37131 Use this option to make configurations in directories separate from the
37132 @value{GDBN} source directories. Among other things, you can use this to
37133 build (or maintain) several configurations simultaneously, in separate
37134 directories. @file{configure} writes configuration-specific files in
37135 the current directory, but arranges for them to use the source in the
37136 directory @var{dirname}. @file{configure} creates directories under
37137 the working directory in parallel to the source directories below
37140 @item --norecursion
37141 Configure only the directory level where @file{configure} is executed; do not
37142 propagate configuration to subdirectories.
37144 @item --target=@var{target}
37145 Configure @value{GDBN} for cross-debugging programs running on the specified
37146 @var{target}. Without this option, @value{GDBN} is configured to debug
37147 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
37149 There is no convenient way to generate a list of all available targets.
37151 @item @var{host} @dots{}
37152 Configure @value{GDBN} to run on the specified @var{host}.
37154 There is no convenient way to generate a list of all available hosts.
37157 There are many other options available as well, but they are generally
37158 needed for special purposes only.
37160 @node System-wide configuration
37161 @section System-wide configuration and settings
37162 @cindex system-wide init file
37164 @value{GDBN} can be configured to have a system-wide init file;
37165 this file will be read and executed at startup (@pxref{Startup, , What
37166 @value{GDBN} does during startup}).
37168 Here is the corresponding configure option:
37171 @item --with-system-gdbinit=@var{file}
37172 Specify that the default location of the system-wide init file is
37176 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
37177 it may be subject to relocation. Two possible cases:
37181 If the default location of this init file contains @file{$prefix},
37182 it will be subject to relocation. Suppose that the configure options
37183 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
37184 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
37185 init file is looked for as @file{$install/etc/gdbinit} instead of
37186 @file{$prefix/etc/gdbinit}.
37189 By contrast, if the default location does not contain the prefix,
37190 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
37191 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
37192 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
37193 wherever @value{GDBN} is installed.
37196 If the configured location of the system-wide init file (as given by the
37197 @option{--with-system-gdbinit} option at configure time) is in the
37198 data-directory (as specified by @option{--with-gdb-datadir} at configure
37199 time) or in one of its subdirectories, then @value{GDBN} will look for the
37200 system-wide init file in the directory specified by the
37201 @option{--data-directory} command-line option.
37202 Note that the system-wide init file is only read once, during @value{GDBN}
37203 initialization. If the data-directory is changed after @value{GDBN} has
37204 started with the @code{set data-directory} command, the file will not be
37208 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
37211 @node System-wide Configuration Scripts
37212 @subsection Installed System-wide Configuration Scripts
37213 @cindex system-wide configuration scripts
37215 The @file{system-gdbinit} directory, located inside the data-directory
37216 (as specified by @option{--with-gdb-datadir} at configure time) contains
37217 a number of scripts which can be used as system-wide init files. To
37218 automatically source those scripts at startup, @value{GDBN} should be
37219 configured with @option{--with-system-gdbinit}. Otherwise, any user
37220 should be able to source them by hand as needed.
37222 The following scripts are currently available:
37225 @item @file{elinos.py}
37227 @cindex ELinOS system-wide configuration script
37228 This script is useful when debugging a program on an ELinOS target.
37229 It takes advantage of the environment variables defined in a standard
37230 ELinOS environment in order to determine the location of the system
37231 shared libraries, and then sets the @samp{solib-absolute-prefix}
37232 and @samp{solib-search-path} variables appropriately.
37234 @item @file{wrs-linux.py}
37235 @pindex wrs-linux.py
37236 @cindex Wind River Linux system-wide configuration script
37237 This script is useful when debugging a program on a target running
37238 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
37239 the host-side sysroot used by the target system.
37243 @node Maintenance Commands
37244 @appendix Maintenance Commands
37245 @cindex maintenance commands
37246 @cindex internal commands
37248 In addition to commands intended for @value{GDBN} users, @value{GDBN}
37249 includes a number of commands intended for @value{GDBN} developers,
37250 that are not documented elsewhere in this manual. These commands are
37251 provided here for reference. (For commands that turn on debugging
37252 messages, see @ref{Debugging Output}.)
37255 @kindex maint agent
37256 @kindex maint agent-eval
37257 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37258 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37259 Translate the given @var{expression} into remote agent bytecodes.
37260 This command is useful for debugging the Agent Expression mechanism
37261 (@pxref{Agent Expressions}). The @samp{agent} version produces an
37262 expression useful for data collection, such as by tracepoints, while
37263 @samp{maint agent-eval} produces an expression that evaluates directly
37264 to a result. For instance, a collection expression for @code{globa +
37265 globb} will include bytecodes to record four bytes of memory at each
37266 of the addresses of @code{globa} and @code{globb}, while discarding
37267 the result of the addition, while an evaluation expression will do the
37268 addition and return the sum.
37269 If @code{-at} is given, generate remote agent bytecode for @var{location}.
37270 If not, generate remote agent bytecode for current frame PC address.
37272 @kindex maint agent-printf
37273 @item maint agent-printf @var{format},@var{expr},...
37274 Translate the given format string and list of argument expressions
37275 into remote agent bytecodes and display them as a disassembled list.
37276 This command is useful for debugging the agent version of dynamic
37277 printf (@pxref{Dynamic Printf}).
37279 @kindex maint info breakpoints
37280 @item @anchor{maint info breakpoints}maint info breakpoints
37281 Using the same format as @samp{info breakpoints}, display both the
37282 breakpoints you've set explicitly, and those @value{GDBN} is using for
37283 internal purposes. Internal breakpoints are shown with negative
37284 breakpoint numbers. The type column identifies what kind of breakpoint
37289 Normal, explicitly set breakpoint.
37292 Normal, explicitly set watchpoint.
37295 Internal breakpoint, used to handle correctly stepping through
37296 @code{longjmp} calls.
37298 @item longjmp resume
37299 Internal breakpoint at the target of a @code{longjmp}.
37302 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
37305 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
37308 Shared library events.
37312 @kindex maint info bfds
37313 @item maint info bfds
37314 This prints information about each @code{bfd} object that is known to
37315 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
37317 @kindex set displaced-stepping
37318 @kindex show displaced-stepping
37319 @cindex displaced stepping support
37320 @cindex out-of-line single-stepping
37321 @item set displaced-stepping
37322 @itemx show displaced-stepping
37323 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
37324 if the target supports it. Displaced stepping is a way to single-step
37325 over breakpoints without removing them from the inferior, by executing
37326 an out-of-line copy of the instruction that was originally at the
37327 breakpoint location. It is also known as out-of-line single-stepping.
37330 @item set displaced-stepping on
37331 If the target architecture supports it, @value{GDBN} will use
37332 displaced stepping to step over breakpoints.
37334 @item set displaced-stepping off
37335 @value{GDBN} will not use displaced stepping to step over breakpoints,
37336 even if such is supported by the target architecture.
37338 @cindex non-stop mode, and @samp{set displaced-stepping}
37339 @item set displaced-stepping auto
37340 This is the default mode. @value{GDBN} will use displaced stepping
37341 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
37342 architecture supports displaced stepping.
37345 @kindex maint check-psymtabs
37346 @item maint check-psymtabs
37347 Check the consistency of currently expanded psymtabs versus symtabs.
37348 Use this to check, for example, whether a symbol is in one but not the other.
37350 @kindex maint check-symtabs
37351 @item maint check-symtabs
37352 Check the consistency of currently expanded symtabs.
37354 @kindex maint expand-symtabs
37355 @item maint expand-symtabs [@var{regexp}]
37356 Expand symbol tables.
37357 If @var{regexp} is specified, only expand symbol tables for file
37358 names matching @var{regexp}.
37360 @kindex maint cplus first_component
37361 @item maint cplus first_component @var{name}
37362 Print the first C@t{++} class/namespace component of @var{name}.
37364 @kindex maint cplus namespace
37365 @item maint cplus namespace
37366 Print the list of possible C@t{++} namespaces.
37368 @kindex maint demangle
37369 @item maint demangle @var{name}
37370 Demangle a C@t{++} or Objective-C mangled @var{name}.
37372 @kindex maint deprecate
37373 @kindex maint undeprecate
37374 @cindex deprecated commands
37375 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
37376 @itemx maint undeprecate @var{command}
37377 Deprecate or undeprecate the named @var{command}. Deprecated commands
37378 cause @value{GDBN} to issue a warning when you use them. The optional
37379 argument @var{replacement} says which newer command should be used in
37380 favor of the deprecated one; if it is given, @value{GDBN} will mention
37381 the replacement as part of the warning.
37383 @kindex maint dump-me
37384 @item maint dump-me
37385 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
37386 Cause a fatal signal in the debugger and force it to dump its core.
37387 This is supported only on systems which support aborting a program
37388 with the @code{SIGQUIT} signal.
37390 @kindex maint internal-error
37391 @kindex maint internal-warning
37392 @item maint internal-error @r{[}@var{message-text}@r{]}
37393 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
37394 Cause @value{GDBN} to call the internal function @code{internal_error}
37395 or @code{internal_warning} and hence behave as though an internal error
37396 or internal warning has been detected. In addition to reporting the
37397 internal problem, these functions give the user the opportunity to
37398 either quit @value{GDBN} or create a core file of the current
37399 @value{GDBN} session.
37401 These commands take an optional parameter @var{message-text} that is
37402 used as the text of the error or warning message.
37404 Here's an example of using @code{internal-error}:
37407 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
37408 @dots{}/maint.c:121: internal-error: testing, 1, 2
37409 A problem internal to GDB has been detected. Further
37410 debugging may prove unreliable.
37411 Quit this debugging session? (y or n) @kbd{n}
37412 Create a core file? (y or n) @kbd{n}
37416 @cindex @value{GDBN} internal error
37417 @cindex internal errors, control of @value{GDBN} behavior
37419 @kindex maint set internal-error
37420 @kindex maint show internal-error
37421 @kindex maint set internal-warning
37422 @kindex maint show internal-warning
37423 @item maint set internal-error @var{action} [ask|yes|no]
37424 @itemx maint show internal-error @var{action}
37425 @itemx maint set internal-warning @var{action} [ask|yes|no]
37426 @itemx maint show internal-warning @var{action}
37427 When @value{GDBN} reports an internal problem (error or warning) it
37428 gives the user the opportunity to both quit @value{GDBN} and create a
37429 core file of the current @value{GDBN} session. These commands let you
37430 override the default behaviour for each particular @var{action},
37431 described in the table below.
37435 You can specify that @value{GDBN} should always (yes) or never (no)
37436 quit. The default is to ask the user what to do.
37439 You can specify that @value{GDBN} should always (yes) or never (no)
37440 create a core file. The default is to ask the user what to do.
37443 @kindex maint packet
37444 @item maint packet @var{text}
37445 If @value{GDBN} is talking to an inferior via the serial protocol,
37446 then this command sends the string @var{text} to the inferior, and
37447 displays the response packet. @value{GDBN} supplies the initial
37448 @samp{$} character, the terminating @samp{#} character, and the
37451 @kindex maint print architecture
37452 @item maint print architecture @r{[}@var{file}@r{]}
37453 Print the entire architecture configuration. The optional argument
37454 @var{file} names the file where the output goes.
37456 @kindex maint print c-tdesc
37457 @item maint print c-tdesc
37458 Print the current target description (@pxref{Target Descriptions}) as
37459 a C source file. The created source file can be used in @value{GDBN}
37460 when an XML parser is not available to parse the description.
37462 @kindex maint print dummy-frames
37463 @item maint print dummy-frames
37464 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
37467 (@value{GDBP}) @kbd{b add}
37469 (@value{GDBP}) @kbd{print add(2,3)}
37470 Breakpoint 2, add (a=2, b=3) at @dots{}
37472 The program being debugged stopped while in a function called from GDB.
37474 (@value{GDBP}) @kbd{maint print dummy-frames}
37475 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
37476 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
37477 call_lo=0x01014000 call_hi=0x01014001
37481 Takes an optional file parameter.
37483 @kindex maint print registers
37484 @kindex maint print raw-registers
37485 @kindex maint print cooked-registers
37486 @kindex maint print register-groups
37487 @kindex maint print remote-registers
37488 @item maint print registers @r{[}@var{file}@r{]}
37489 @itemx maint print raw-registers @r{[}@var{file}@r{]}
37490 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
37491 @itemx maint print register-groups @r{[}@var{file}@r{]}
37492 @itemx maint print remote-registers @r{[}@var{file}@r{]}
37493 Print @value{GDBN}'s internal register data structures.
37495 The command @code{maint print raw-registers} includes the contents of
37496 the raw register cache; the command @code{maint print
37497 cooked-registers} includes the (cooked) value of all registers,
37498 including registers which aren't available on the target nor visible
37499 to user; the command @code{maint print register-groups} includes the
37500 groups that each register is a member of; and the command @code{maint
37501 print remote-registers} includes the remote target's register numbers
37502 and offsets in the `G' packets.
37504 These commands take an optional parameter, a file name to which to
37505 write the information.
37507 @kindex maint print reggroups
37508 @item maint print reggroups @r{[}@var{file}@r{]}
37509 Print @value{GDBN}'s internal register group data structures. The
37510 optional argument @var{file} tells to what file to write the
37513 The register groups info looks like this:
37516 (@value{GDBP}) @kbd{maint print reggroups}
37529 This command forces @value{GDBN} to flush its internal register cache.
37531 @kindex maint print objfiles
37532 @cindex info for known object files
37533 @item maint print objfiles @r{[}@var{regexp}@r{]}
37534 Print a dump of all known object files.
37535 If @var{regexp} is specified, only print object files whose names
37536 match @var{regexp}. For each object file, this command prints its name,
37537 address in memory, and all of its psymtabs and symtabs.
37539 @kindex maint print section-scripts
37540 @cindex info for known .debug_gdb_scripts-loaded scripts
37541 @item maint print section-scripts [@var{regexp}]
37542 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
37543 If @var{regexp} is specified, only print scripts loaded by object files
37544 matching @var{regexp}.
37545 For each script, this command prints its name as specified in the objfile,
37546 and the full path if known.
37547 @xref{dotdebug_gdb_scripts section}.
37549 @kindex maint print statistics
37550 @cindex bcache statistics
37551 @item maint print statistics
37552 This command prints, for each object file in the program, various data
37553 about that object file followed by the byte cache (@dfn{bcache})
37554 statistics for the object file. The objfile data includes the number
37555 of minimal, partial, full, and stabs symbols, the number of types
37556 defined by the objfile, the number of as yet unexpanded psym tables,
37557 the number of line tables and string tables, and the amount of memory
37558 used by the various tables. The bcache statistics include the counts,
37559 sizes, and counts of duplicates of all and unique objects, max,
37560 average, and median entry size, total memory used and its overhead and
37561 savings, and various measures of the hash table size and chain
37564 @kindex maint print target-stack
37565 @cindex target stack description
37566 @item maint print target-stack
37567 A @dfn{target} is an interface between the debugger and a particular
37568 kind of file or process. Targets can be stacked in @dfn{strata},
37569 so that more than one target can potentially respond to a request.
37570 In particular, memory accesses will walk down the stack of targets
37571 until they find a target that is interested in handling that particular
37574 This command prints a short description of each layer that was pushed on
37575 the @dfn{target stack}, starting from the top layer down to the bottom one.
37577 @kindex maint print type
37578 @cindex type chain of a data type
37579 @item maint print type @var{expr}
37580 Print the type chain for a type specified by @var{expr}. The argument
37581 can be either a type name or a symbol. If it is a symbol, the type of
37582 that symbol is described. The type chain produced by this command is
37583 a recursive definition of the data type as stored in @value{GDBN}'s
37584 data structures, including its flags and contained types.
37586 @kindex maint set dwarf2 always-disassemble
37587 @kindex maint show dwarf2 always-disassemble
37588 @item maint set dwarf2 always-disassemble
37589 @item maint show dwarf2 always-disassemble
37590 Control the behavior of @code{info address} when using DWARF debugging
37593 The default is @code{off}, which means that @value{GDBN} should try to
37594 describe a variable's location in an easily readable format. When
37595 @code{on}, @value{GDBN} will instead display the DWARF location
37596 expression in an assembly-like format. Note that some locations are
37597 too complex for @value{GDBN} to describe simply; in this case you will
37598 always see the disassembly form.
37600 Here is an example of the resulting disassembly:
37603 (gdb) info addr argc
37604 Symbol "argc" is a complex DWARF expression:
37608 For more information on these expressions, see
37609 @uref{http://www.dwarfstd.org/, the DWARF standard}.
37611 @kindex maint set dwarf2 max-cache-age
37612 @kindex maint show dwarf2 max-cache-age
37613 @item maint set dwarf2 max-cache-age
37614 @itemx maint show dwarf2 max-cache-age
37615 Control the DWARF 2 compilation unit cache.
37617 @cindex DWARF 2 compilation units cache
37618 In object files with inter-compilation-unit references, such as those
37619 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
37620 reader needs to frequently refer to previously read compilation units.
37621 This setting controls how long a compilation unit will remain in the
37622 cache if it is not referenced. A higher limit means that cached
37623 compilation units will be stored in memory longer, and more total
37624 memory will be used. Setting it to zero disables caching, which will
37625 slow down @value{GDBN} startup, but reduce memory consumption.
37627 @kindex maint set profile
37628 @kindex maint show profile
37629 @cindex profiling GDB
37630 @item maint set profile
37631 @itemx maint show profile
37632 Control profiling of @value{GDBN}.
37634 Profiling will be disabled until you use the @samp{maint set profile}
37635 command to enable it. When you enable profiling, the system will begin
37636 collecting timing and execution count data; when you disable profiling or
37637 exit @value{GDBN}, the results will be written to a log file. Remember that
37638 if you use profiling, @value{GDBN} will overwrite the profiling log file
37639 (often called @file{gmon.out}). If you have a record of important profiling
37640 data in a @file{gmon.out} file, be sure to move it to a safe location.
37642 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
37643 compiled with the @samp{-pg} compiler option.
37645 @kindex maint set show-debug-regs
37646 @kindex maint show show-debug-regs
37647 @cindex hardware debug registers
37648 @item maint set show-debug-regs
37649 @itemx maint show show-debug-regs
37650 Control whether to show variables that mirror the hardware debug
37651 registers. Use @code{on} to enable, @code{off} to disable. If
37652 enabled, the debug registers values are shown when @value{GDBN} inserts or
37653 removes a hardware breakpoint or watchpoint, and when the inferior
37654 triggers a hardware-assisted breakpoint or watchpoint.
37656 @kindex maint set show-all-tib
37657 @kindex maint show show-all-tib
37658 @item maint set show-all-tib
37659 @itemx maint show show-all-tib
37660 Control whether to show all non zero areas within a 1k block starting
37661 at thread local base, when using the @samp{info w32 thread-information-block}
37664 @kindex maint set per-command
37665 @kindex maint show per-command
37666 @item maint set per-command
37667 @itemx maint show per-command
37668 @cindex resources used by commands
37670 @value{GDBN} can display the resources used by each command.
37671 This is useful in debugging performance problems.
37674 @item maint set per-command space [on|off]
37675 @itemx maint show per-command space
37676 Enable or disable the printing of the memory used by GDB for each command.
37677 If enabled, @value{GDBN} will display how much memory each command
37678 took, following the command's own output.
37679 This can also be requested by invoking @value{GDBN} with the
37680 @option{--statistics} command-line switch (@pxref{Mode Options}).
37682 @item maint set per-command time [on|off]
37683 @itemx maint show per-command time
37684 Enable or disable the printing of the execution time of @value{GDBN}
37686 If enabled, @value{GDBN} will display how much time it
37687 took to execute each command, following the command's own output.
37688 Both CPU time and wallclock time are printed.
37689 Printing both is useful when trying to determine whether the cost is
37690 CPU or, e.g., disk/network latency.
37691 Note that the CPU time printed is for @value{GDBN} only, it does not include
37692 the execution time of the inferior because there's no mechanism currently
37693 to compute how much time was spent by @value{GDBN} and how much time was
37694 spent by the program been debugged.
37695 This can also be requested by invoking @value{GDBN} with the
37696 @option{--statistics} command-line switch (@pxref{Mode Options}).
37698 @item maint set per-command symtab [on|off]
37699 @itemx maint show per-command symtab
37700 Enable or disable the printing of basic symbol table statistics
37702 If enabled, @value{GDBN} will display the following information:
37706 number of symbol tables
37708 number of primary symbol tables
37710 number of blocks in the blockvector
37714 @kindex maint space
37715 @cindex memory used by commands
37716 @item maint space @var{value}
37717 An alias for @code{maint set per-command space}.
37718 A non-zero value enables it, zero disables it.
37721 @cindex time of command execution
37722 @item maint time @var{value}
37723 An alias for @code{maint set per-command time}.
37724 A non-zero value enables it, zero disables it.
37726 @kindex maint translate-address
37727 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
37728 Find the symbol stored at the location specified by the address
37729 @var{addr} and an optional section name @var{section}. If found,
37730 @value{GDBN} prints the name of the closest symbol and an offset from
37731 the symbol's location to the specified address. This is similar to
37732 the @code{info address} command (@pxref{Symbols}), except that this
37733 command also allows to find symbols in other sections.
37735 If section was not specified, the section in which the symbol was found
37736 is also printed. For dynamically linked executables, the name of
37737 executable or shared library containing the symbol is printed as well.
37741 The following command is useful for non-interactive invocations of
37742 @value{GDBN}, such as in the test suite.
37745 @item set watchdog @var{nsec}
37746 @kindex set watchdog
37747 @cindex watchdog timer
37748 @cindex timeout for commands
37749 Set the maximum number of seconds @value{GDBN} will wait for the
37750 target operation to finish. If this time expires, @value{GDBN}
37751 reports and error and the command is aborted.
37753 @item show watchdog
37754 Show the current setting of the target wait timeout.
37757 @node Remote Protocol
37758 @appendix @value{GDBN} Remote Serial Protocol
37763 * Stop Reply Packets::
37764 * General Query Packets::
37765 * Architecture-Specific Protocol Details::
37766 * Tracepoint Packets::
37767 * Host I/O Packets::
37769 * Notification Packets::
37770 * Remote Non-Stop::
37771 * Packet Acknowledgment::
37773 * File-I/O Remote Protocol Extension::
37774 * Library List Format::
37775 * Library List Format for SVR4 Targets::
37776 * Memory Map Format::
37777 * Thread List Format::
37778 * Traceframe Info Format::
37779 * Branch Trace Format::
37785 There may be occasions when you need to know something about the
37786 protocol---for example, if there is only one serial port to your target
37787 machine, you might want your program to do something special if it
37788 recognizes a packet meant for @value{GDBN}.
37790 In the examples below, @samp{->} and @samp{<-} are used to indicate
37791 transmitted and received data, respectively.
37793 @cindex protocol, @value{GDBN} remote serial
37794 @cindex serial protocol, @value{GDBN} remote
37795 @cindex remote serial protocol
37796 All @value{GDBN} commands and responses (other than acknowledgments
37797 and notifications, see @ref{Notification Packets}) are sent as a
37798 @var{packet}. A @var{packet} is introduced with the character
37799 @samp{$}, the actual @var{packet-data}, and the terminating character
37800 @samp{#} followed by a two-digit @var{checksum}:
37803 @code{$}@var{packet-data}@code{#}@var{checksum}
37807 @cindex checksum, for @value{GDBN} remote
37809 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37810 characters between the leading @samp{$} and the trailing @samp{#} (an
37811 eight bit unsigned checksum).
37813 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37814 specification also included an optional two-digit @var{sequence-id}:
37817 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37820 @cindex sequence-id, for @value{GDBN} remote
37822 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37823 has never output @var{sequence-id}s. Stubs that handle packets added
37824 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37826 When either the host or the target machine receives a packet, the first
37827 response expected is an acknowledgment: either @samp{+} (to indicate
37828 the package was received correctly) or @samp{-} (to request
37832 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37837 The @samp{+}/@samp{-} acknowledgments can be disabled
37838 once a connection is established.
37839 @xref{Packet Acknowledgment}, for details.
37841 The host (@value{GDBN}) sends @var{command}s, and the target (the
37842 debugging stub incorporated in your program) sends a @var{response}. In
37843 the case of step and continue @var{command}s, the response is only sent
37844 when the operation has completed, and the target has again stopped all
37845 threads in all attached processes. This is the default all-stop mode
37846 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37847 execution mode; see @ref{Remote Non-Stop}, for details.
37849 @var{packet-data} consists of a sequence of characters with the
37850 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37853 @cindex remote protocol, field separator
37854 Fields within the packet should be separated using @samp{,} @samp{;} or
37855 @samp{:}. Except where otherwise noted all numbers are represented in
37856 @sc{hex} with leading zeros suppressed.
37858 Implementors should note that prior to @value{GDBN} 5.0, the character
37859 @samp{:} could not appear as the third character in a packet (as it
37860 would potentially conflict with the @var{sequence-id}).
37862 @cindex remote protocol, binary data
37863 @anchor{Binary Data}
37864 Binary data in most packets is encoded either as two hexadecimal
37865 digits per byte of binary data. This allowed the traditional remote
37866 protocol to work over connections which were only seven-bit clean.
37867 Some packets designed more recently assume an eight-bit clean
37868 connection, and use a more efficient encoding to send and receive
37871 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37872 as an escape character. Any escaped byte is transmitted as the escape
37873 character followed by the original character XORed with @code{0x20}.
37874 For example, the byte @code{0x7d} would be transmitted as the two
37875 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37876 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37877 @samp{@}}) must always be escaped. Responses sent by the stub
37878 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37879 is not interpreted as the start of a run-length encoded sequence
37882 Response @var{data} can be run-length encoded to save space.
37883 Run-length encoding replaces runs of identical characters with one
37884 instance of the repeated character, followed by a @samp{*} and a
37885 repeat count. The repeat count is itself sent encoded, to avoid
37886 binary characters in @var{data}: a value of @var{n} is sent as
37887 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37888 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37889 code 32) for a repeat count of 3. (This is because run-length
37890 encoding starts to win for counts 3 or more.) Thus, for example,
37891 @samp{0* } is a run-length encoding of ``0000'': the space character
37892 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37895 The printable characters @samp{#} and @samp{$} or with a numeric value
37896 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37897 seven repeats (@samp{$}) can be expanded using a repeat count of only
37898 five (@samp{"}). For example, @samp{00000000} can be encoded as
37901 The error response returned for some packets includes a two character
37902 error number. That number is not well defined.
37904 @cindex empty response, for unsupported packets
37905 For any @var{command} not supported by the stub, an empty response
37906 (@samp{$#00}) should be returned. That way it is possible to extend the
37907 protocol. A newer @value{GDBN} can tell if a packet is supported based
37910 At a minimum, a stub is required to support the @samp{g} and @samp{G}
37911 commands for register access, and the @samp{m} and @samp{M} commands
37912 for memory access. Stubs that only control single-threaded targets
37913 can implement run control with the @samp{c} (continue), and @samp{s}
37914 (step) commands. Stubs that support multi-threading targets should
37915 support the @samp{vCont} command. All other commands are optional.
37920 The following table provides a complete list of all currently defined
37921 @var{command}s and their corresponding response @var{data}.
37922 @xref{File-I/O Remote Protocol Extension}, for details about the File
37923 I/O extension of the remote protocol.
37925 Each packet's description has a template showing the packet's overall
37926 syntax, followed by an explanation of the packet's meaning. We
37927 include spaces in some of the templates for clarity; these are not
37928 part of the packet's syntax. No @value{GDBN} packet uses spaces to
37929 separate its components. For example, a template like @samp{foo
37930 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
37931 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
37932 @var{baz}. @value{GDBN} does not transmit a space character between the
37933 @samp{foo} and the @var{bar}, or between the @var{bar} and the
37936 @cindex @var{thread-id}, in remote protocol
37937 @anchor{thread-id syntax}
37938 Several packets and replies include a @var{thread-id} field to identify
37939 a thread. Normally these are positive numbers with a target-specific
37940 interpretation, formatted as big-endian hex strings. A @var{thread-id}
37941 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
37944 In addition, the remote protocol supports a multiprocess feature in
37945 which the @var{thread-id} syntax is extended to optionally include both
37946 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
37947 The @var{pid} (process) and @var{tid} (thread) components each have the
37948 format described above: a positive number with target-specific
37949 interpretation formatted as a big-endian hex string, literal @samp{-1}
37950 to indicate all processes or threads (respectively), or @samp{0} to
37951 indicate an arbitrary process or thread. Specifying just a process, as
37952 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
37953 error to specify all processes but a specific thread, such as
37954 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
37955 for those packets and replies explicitly documented to include a process
37956 ID, rather than a @var{thread-id}.
37958 The multiprocess @var{thread-id} syntax extensions are only used if both
37959 @value{GDBN} and the stub report support for the @samp{multiprocess}
37960 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
37963 Note that all packet forms beginning with an upper- or lower-case
37964 letter, other than those described here, are reserved for future use.
37966 Here are the packet descriptions.
37971 @cindex @samp{!} packet
37972 @anchor{extended mode}
37973 Enable extended mode. In extended mode, the remote server is made
37974 persistent. The @samp{R} packet is used to restart the program being
37980 The remote target both supports and has enabled extended mode.
37984 @cindex @samp{?} packet
37985 Indicate the reason the target halted. The reply is the same as for
37986 step and continue. This packet has a special interpretation when the
37987 target is in non-stop mode; see @ref{Remote Non-Stop}.
37990 @xref{Stop Reply Packets}, for the reply specifications.
37992 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
37993 @cindex @samp{A} packet
37994 Initialized @code{argv[]} array passed into program. @var{arglen}
37995 specifies the number of bytes in the hex encoded byte stream
37996 @var{arg}. See @code{gdbserver} for more details.
38001 The arguments were set.
38007 @cindex @samp{b} packet
38008 (Don't use this packet; its behavior is not well-defined.)
38009 Change the serial line speed to @var{baud}.
38011 JTC: @emph{When does the transport layer state change? When it's
38012 received, or after the ACK is transmitted. In either case, there are
38013 problems if the command or the acknowledgment packet is dropped.}
38015 Stan: @emph{If people really wanted to add something like this, and get
38016 it working for the first time, they ought to modify ser-unix.c to send
38017 some kind of out-of-band message to a specially-setup stub and have the
38018 switch happen "in between" packets, so that from remote protocol's point
38019 of view, nothing actually happened.}
38021 @item B @var{addr},@var{mode}
38022 @cindex @samp{B} packet
38023 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
38024 breakpoint at @var{addr}.
38026 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
38027 (@pxref{insert breakpoint or watchpoint packet}).
38029 @cindex @samp{bc} packet
38032 Backward continue. Execute the target system in reverse. No parameter.
38033 @xref{Reverse Execution}, for more information.
38036 @xref{Stop Reply Packets}, for the reply specifications.
38038 @cindex @samp{bs} packet
38041 Backward single step. Execute one instruction in reverse. No parameter.
38042 @xref{Reverse Execution}, for more information.
38045 @xref{Stop Reply Packets}, for the reply specifications.
38047 @item c @r{[}@var{addr}@r{]}
38048 @cindex @samp{c} packet
38049 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
38050 resume at current address.
38052 This packet is deprecated for multi-threading support. @xref{vCont
38056 @xref{Stop Reply Packets}, for the reply specifications.
38058 @item C @var{sig}@r{[};@var{addr}@r{]}
38059 @cindex @samp{C} packet
38060 Continue with signal @var{sig} (hex signal number). If
38061 @samp{;@var{addr}} is omitted, resume at same address.
38063 This packet is deprecated for multi-threading support. @xref{vCont
38067 @xref{Stop Reply Packets}, for the reply specifications.
38070 @cindex @samp{d} packet
38073 Don't use this packet; instead, define a general set packet
38074 (@pxref{General Query Packets}).
38078 @cindex @samp{D} packet
38079 The first form of the packet is used to detach @value{GDBN} from the
38080 remote system. It is sent to the remote target
38081 before @value{GDBN} disconnects via the @code{detach} command.
38083 The second form, including a process ID, is used when multiprocess
38084 protocol extensions are enabled (@pxref{multiprocess extensions}), to
38085 detach only a specific process. The @var{pid} is specified as a
38086 big-endian hex string.
38096 @item F @var{RC},@var{EE},@var{CF};@var{XX}
38097 @cindex @samp{F} packet
38098 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
38099 This is part of the File-I/O protocol extension. @xref{File-I/O
38100 Remote Protocol Extension}, for the specification.
38103 @anchor{read registers packet}
38104 @cindex @samp{g} packet
38105 Read general registers.
38109 @item @var{XX@dots{}}
38110 Each byte of register data is described by two hex digits. The bytes
38111 with the register are transmitted in target byte order. The size of
38112 each register and their position within the @samp{g} packet are
38113 determined by the @value{GDBN} internal gdbarch functions
38114 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
38115 specification of several standard @samp{g} packets is specified below.
38117 When reading registers from a trace frame (@pxref{Analyze Collected
38118 Data,,Using the Collected Data}), the stub may also return a string of
38119 literal @samp{x}'s in place of the register data digits, to indicate
38120 that the corresponding register has not been collected, thus its value
38121 is unavailable. For example, for an architecture with 4 registers of
38122 4 bytes each, the following reply indicates to @value{GDBN} that
38123 registers 0 and 2 have not been collected, while registers 1 and 3
38124 have been collected, and both have zero value:
38128 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
38135 @item G @var{XX@dots{}}
38136 @cindex @samp{G} packet
38137 Write general registers. @xref{read registers packet}, for a
38138 description of the @var{XX@dots{}} data.
38148 @item H @var{op} @var{thread-id}
38149 @cindex @samp{H} packet
38150 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
38151 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
38152 it should be @samp{c} for step and continue operations (note that this
38153 is deprecated, supporting the @samp{vCont} command is a better
38154 option), @samp{g} for other operations. The thread designator
38155 @var{thread-id} has the format and interpretation described in
38156 @ref{thread-id syntax}.
38167 @c 'H': How restrictive (or permissive) is the thread model. If a
38168 @c thread is selected and stopped, are other threads allowed
38169 @c to continue to execute? As I mentioned above, I think the
38170 @c semantics of each command when a thread is selected must be
38171 @c described. For example:
38173 @c 'g': If the stub supports threads and a specific thread is
38174 @c selected, returns the register block from that thread;
38175 @c otherwise returns current registers.
38177 @c 'G' If the stub supports threads and a specific thread is
38178 @c selected, sets the registers of the register block of
38179 @c that thread; otherwise sets current registers.
38181 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
38182 @anchor{cycle step packet}
38183 @cindex @samp{i} packet
38184 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
38185 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
38186 step starting at that address.
38189 @cindex @samp{I} packet
38190 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
38194 @cindex @samp{k} packet
38197 FIXME: @emph{There is no description of how to operate when a specific
38198 thread context has been selected (i.e.@: does 'k' kill only that
38201 @item m @var{addr},@var{length}
38202 @cindex @samp{m} packet
38203 Read @var{length} bytes of memory starting at address @var{addr}.
38204 Note that @var{addr} may not be aligned to any particular boundary.
38206 The stub need not use any particular size or alignment when gathering
38207 data from memory for the response; even if @var{addr} is word-aligned
38208 and @var{length} is a multiple of the word size, the stub is free to
38209 use byte accesses, or not. For this reason, this packet may not be
38210 suitable for accessing memory-mapped I/O devices.
38211 @cindex alignment of remote memory accesses
38212 @cindex size of remote memory accesses
38213 @cindex memory, alignment and size of remote accesses
38217 @item @var{XX@dots{}}
38218 Memory contents; each byte is transmitted as a two-digit hexadecimal
38219 number. The reply may contain fewer bytes than requested if the
38220 server was able to read only part of the region of memory.
38225 @item M @var{addr},@var{length}:@var{XX@dots{}}
38226 @cindex @samp{M} packet
38227 Write @var{length} bytes of memory starting at address @var{addr}.
38228 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
38229 hexadecimal number.
38236 for an error (this includes the case where only part of the data was
38241 @cindex @samp{p} packet
38242 Read the value of register @var{n}; @var{n} is in hex.
38243 @xref{read registers packet}, for a description of how the returned
38244 register value is encoded.
38248 @item @var{XX@dots{}}
38249 the register's value
38253 Indicating an unrecognized @var{query}.
38256 @item P @var{n@dots{}}=@var{r@dots{}}
38257 @anchor{write register packet}
38258 @cindex @samp{P} packet
38259 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
38260 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
38261 digits for each byte in the register (target byte order).
38271 @item q @var{name} @var{params}@dots{}
38272 @itemx Q @var{name} @var{params}@dots{}
38273 @cindex @samp{q} packet
38274 @cindex @samp{Q} packet
38275 General query (@samp{q}) and set (@samp{Q}). These packets are
38276 described fully in @ref{General Query Packets}.
38279 @cindex @samp{r} packet
38280 Reset the entire system.
38282 Don't use this packet; use the @samp{R} packet instead.
38285 @cindex @samp{R} packet
38286 Restart the program being debugged. @var{XX}, while needed, is ignored.
38287 This packet is only available in extended mode (@pxref{extended mode}).
38289 The @samp{R} packet has no reply.
38291 @item s @r{[}@var{addr}@r{]}
38292 @cindex @samp{s} packet
38293 Single step. @var{addr} is the address at which to resume. If
38294 @var{addr} is omitted, resume at same address.
38296 This packet is deprecated for multi-threading support. @xref{vCont
38300 @xref{Stop Reply Packets}, for the reply specifications.
38302 @item S @var{sig}@r{[};@var{addr}@r{]}
38303 @anchor{step with signal packet}
38304 @cindex @samp{S} packet
38305 Step with signal. This is analogous to the @samp{C} packet, but
38306 requests a single-step, rather than a normal resumption of execution.
38308 This packet is deprecated for multi-threading support. @xref{vCont
38312 @xref{Stop Reply Packets}, for the reply specifications.
38314 @item t @var{addr}:@var{PP},@var{MM}
38315 @cindex @samp{t} packet
38316 Search backwards starting at address @var{addr} for a match with pattern
38317 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
38318 @var{addr} must be at least 3 digits.
38320 @item T @var{thread-id}
38321 @cindex @samp{T} packet
38322 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
38327 thread is still alive
38333 Packets starting with @samp{v} are identified by a multi-letter name,
38334 up to the first @samp{;} or @samp{?} (or the end of the packet).
38336 @item vAttach;@var{pid}
38337 @cindex @samp{vAttach} packet
38338 Attach to a new process with the specified process ID @var{pid}.
38339 The process ID is a
38340 hexadecimal integer identifying the process. In all-stop mode, all
38341 threads in the attached process are stopped; in non-stop mode, it may be
38342 attached without being stopped if that is supported by the target.
38344 @c In non-stop mode, on a successful vAttach, the stub should set the
38345 @c current thread to a thread of the newly-attached process. After
38346 @c attaching, GDB queries for the attached process's thread ID with qC.
38347 @c Also note that, from a user perspective, whether or not the
38348 @c target is stopped on attach in non-stop mode depends on whether you
38349 @c use the foreground or background version of the attach command, not
38350 @c on what vAttach does; GDB does the right thing with respect to either
38351 @c stopping or restarting threads.
38353 This packet is only available in extended mode (@pxref{extended mode}).
38359 @item @r{Any stop packet}
38360 for success in all-stop mode (@pxref{Stop Reply Packets})
38362 for success in non-stop mode (@pxref{Remote Non-Stop})
38365 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
38366 @cindex @samp{vCont} packet
38367 @anchor{vCont packet}
38368 Resume the inferior, specifying different actions for each thread.
38369 If an action is specified with no @var{thread-id}, then it is applied to any
38370 threads that don't have a specific action specified; if no default action is
38371 specified then other threads should remain stopped in all-stop mode and
38372 in their current state in non-stop mode.
38373 Specifying multiple
38374 default actions is an error; specifying no actions is also an error.
38375 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
38377 Currently supported actions are:
38383 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
38387 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
38390 @item r @var{start},@var{end}
38391 Step once, and then keep stepping as long as the thread stops at
38392 addresses between @var{start} (inclusive) and @var{end} (exclusive).
38393 The remote stub reports a stop reply when either the thread goes out
38394 of the range or is stopped due to an unrelated reason, such as hitting
38395 a breakpoint. @xref{range stepping}.
38397 If the range is empty (@var{start} == @var{end}), then the action
38398 becomes equivalent to the @samp{s} action. In other words,
38399 single-step once, and report the stop (even if the stepped instruction
38400 jumps to @var{start}).
38402 (A stop reply may be sent at any point even if the PC is still within
38403 the stepping range; for example, it is valid to implement this packet
38404 in a degenerate way as a single instruction step operation.)
38408 The optional argument @var{addr} normally associated with the
38409 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
38410 not supported in @samp{vCont}.
38412 The @samp{t} action is only relevant in non-stop mode
38413 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
38414 A stop reply should be generated for any affected thread not already stopped.
38415 When a thread is stopped by means of a @samp{t} action,
38416 the corresponding stop reply should indicate that the thread has stopped with
38417 signal @samp{0}, regardless of whether the target uses some other signal
38418 as an implementation detail.
38420 The stub must support @samp{vCont} if it reports support for
38421 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
38422 this case @samp{vCont} actions can be specified to apply to all threads
38423 in a process by using the @samp{p@var{pid}.-1} form of the
38427 @xref{Stop Reply Packets}, for the reply specifications.
38430 @cindex @samp{vCont?} packet
38431 Request a list of actions supported by the @samp{vCont} packet.
38435 @item vCont@r{[};@var{action}@dots{}@r{]}
38436 The @samp{vCont} packet is supported. Each @var{action} is a supported
38437 command in the @samp{vCont} packet.
38439 The @samp{vCont} packet is not supported.
38442 @item vFile:@var{operation}:@var{parameter}@dots{}
38443 @cindex @samp{vFile} packet
38444 Perform a file operation on the target system. For details,
38445 see @ref{Host I/O Packets}.
38447 @item vFlashErase:@var{addr},@var{length}
38448 @cindex @samp{vFlashErase} packet
38449 Direct the stub to erase @var{length} bytes of flash starting at
38450 @var{addr}. The region may enclose any number of flash blocks, but
38451 its start and end must fall on block boundaries, as indicated by the
38452 flash block size appearing in the memory map (@pxref{Memory Map
38453 Format}). @value{GDBN} groups flash memory programming operations
38454 together, and sends a @samp{vFlashDone} request after each group; the
38455 stub is allowed to delay erase operation until the @samp{vFlashDone}
38456 packet is received.
38466 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
38467 @cindex @samp{vFlashWrite} packet
38468 Direct the stub to write data to flash address @var{addr}. The data
38469 is passed in binary form using the same encoding as for the @samp{X}
38470 packet (@pxref{Binary Data}). The memory ranges specified by
38471 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
38472 not overlap, and must appear in order of increasing addresses
38473 (although @samp{vFlashErase} packets for higher addresses may already
38474 have been received; the ordering is guaranteed only between
38475 @samp{vFlashWrite} packets). If a packet writes to an address that was
38476 neither erased by a preceding @samp{vFlashErase} packet nor by some other
38477 target-specific method, the results are unpredictable.
38485 for vFlashWrite addressing non-flash memory
38491 @cindex @samp{vFlashDone} packet
38492 Indicate to the stub that flash programming operation is finished.
38493 The stub is permitted to delay or batch the effects of a group of
38494 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
38495 @samp{vFlashDone} packet is received. The contents of the affected
38496 regions of flash memory are unpredictable until the @samp{vFlashDone}
38497 request is completed.
38499 @item vKill;@var{pid}
38500 @cindex @samp{vKill} packet
38501 Kill the process with the specified process ID. @var{pid} is a
38502 hexadecimal integer identifying the process. This packet is used in
38503 preference to @samp{k} when multiprocess protocol extensions are
38504 supported; see @ref{multiprocess extensions}.
38514 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
38515 @cindex @samp{vRun} packet
38516 Run the program @var{filename}, passing it each @var{argument} on its
38517 command line. The file and arguments are hex-encoded strings. If
38518 @var{filename} is an empty string, the stub may use a default program
38519 (e.g.@: the last program run). The program is created in the stopped
38522 @c FIXME: What about non-stop mode?
38524 This packet is only available in extended mode (@pxref{extended mode}).
38530 @item @r{Any stop packet}
38531 for success (@pxref{Stop Reply Packets})
38535 @cindex @samp{vStopped} packet
38536 @xref{Notification Packets}.
38538 @item X @var{addr},@var{length}:@var{XX@dots{}}
38540 @cindex @samp{X} packet
38541 Write data to memory, where the data is transmitted in binary.
38542 @var{addr} is address, @var{length} is number of bytes,
38543 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
38553 @item z @var{type},@var{addr},@var{kind}
38554 @itemx Z @var{type},@var{addr},@var{kind}
38555 @anchor{insert breakpoint or watchpoint packet}
38556 @cindex @samp{z} packet
38557 @cindex @samp{Z} packets
38558 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
38559 watchpoint starting at address @var{address} of kind @var{kind}.
38561 Each breakpoint and watchpoint packet @var{type} is documented
38564 @emph{Implementation notes: A remote target shall return an empty string
38565 for an unrecognized breakpoint or watchpoint packet @var{type}. A
38566 remote target shall support either both or neither of a given
38567 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
38568 avoid potential problems with duplicate packets, the operations should
38569 be implemented in an idempotent way.}
38571 @item z0,@var{addr},@var{kind}
38572 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
38573 @cindex @samp{z0} packet
38574 @cindex @samp{Z0} packet
38575 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
38576 @var{addr} of type @var{kind}.
38578 A memory breakpoint is implemented by replacing the instruction at
38579 @var{addr} with a software breakpoint or trap instruction. The
38580 @var{kind} is target-specific and typically indicates the size of
38581 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
38582 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
38583 architectures have additional meanings for @var{kind};
38584 @var{cond_list} is an optional list of conditional expressions in bytecode
38585 form that should be evaluated on the target's side. These are the
38586 conditions that should be taken into consideration when deciding if
38587 the breakpoint trigger should be reported back to @var{GDBN}.
38589 The @var{cond_list} parameter is comprised of a series of expressions,
38590 concatenated without separators. Each expression has the following form:
38594 @item X @var{len},@var{expr}
38595 @var{len} is the length of the bytecode expression and @var{expr} is the
38596 actual conditional expression in bytecode form.
38600 The optional @var{cmd_list} parameter introduces commands that may be
38601 run on the target, rather than being reported back to @value{GDBN}.
38602 The parameter starts with a numeric flag @var{persist}; if the flag is
38603 nonzero, then the breakpoint may remain active and the commands
38604 continue to be run even when @value{GDBN} disconnects from the target.
38605 Following this flag is a series of expressions concatenated with no
38606 separators. Each expression has the following form:
38610 @item X @var{len},@var{expr}
38611 @var{len} is the length of the bytecode expression and @var{expr} is the
38612 actual conditional expression in bytecode form.
38616 see @ref{Architecture-Specific Protocol Details}.
38618 @emph{Implementation note: It is possible for a target to copy or move
38619 code that contains memory breakpoints (e.g., when implementing
38620 overlays). The behavior of this packet, in the presence of such a
38621 target, is not defined.}
38633 @item z1,@var{addr},@var{kind}
38634 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
38635 @cindex @samp{z1} packet
38636 @cindex @samp{Z1} packet
38637 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
38638 address @var{addr}.
38640 A hardware breakpoint is implemented using a mechanism that is not
38641 dependant on being able to modify the target's memory. @var{kind}
38642 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
38644 @emph{Implementation note: A hardware breakpoint is not affected by code
38657 @item z2,@var{addr},@var{kind}
38658 @itemx Z2,@var{addr},@var{kind}
38659 @cindex @samp{z2} packet
38660 @cindex @samp{Z2} packet
38661 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
38662 @var{kind} is interpreted as the number of bytes to watch.
38674 @item z3,@var{addr},@var{kind}
38675 @itemx Z3,@var{addr},@var{kind}
38676 @cindex @samp{z3} packet
38677 @cindex @samp{Z3} packet
38678 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
38679 @var{kind} is interpreted as the number of bytes to watch.
38691 @item z4,@var{addr},@var{kind}
38692 @itemx Z4,@var{addr},@var{kind}
38693 @cindex @samp{z4} packet
38694 @cindex @samp{Z4} packet
38695 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
38696 @var{kind} is interpreted as the number of bytes to watch.
38710 @node Stop Reply Packets
38711 @section Stop Reply Packets
38712 @cindex stop reply packets
38714 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
38715 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
38716 receive any of the below as a reply. Except for @samp{?}
38717 and @samp{vStopped}, that reply is only returned
38718 when the target halts. In the below the exact meaning of @dfn{signal
38719 number} is defined by the header @file{include/gdb/signals.h} in the
38720 @value{GDBN} source code.
38722 As in the description of request packets, we include spaces in the
38723 reply templates for clarity; these are not part of the reply packet's
38724 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
38730 The program received signal number @var{AA} (a two-digit hexadecimal
38731 number). This is equivalent to a @samp{T} response with no
38732 @var{n}:@var{r} pairs.
38734 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
38735 @cindex @samp{T} packet reply
38736 The program received signal number @var{AA} (a two-digit hexadecimal
38737 number). This is equivalent to an @samp{S} response, except that the
38738 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38739 and other information directly in the stop reply packet, reducing
38740 round-trip latency. Single-step and breakpoint traps are reported
38741 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38745 If @var{n} is a hexadecimal number, it is a register number, and the
38746 corresponding @var{r} gives that register's value. @var{r} is a
38747 series of bytes in target byte order, with each byte given by a
38748 two-digit hex number.
38751 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38752 the stopped thread, as specified in @ref{thread-id syntax}.
38755 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38756 the core on which the stop event was detected.
38759 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38760 specific event that stopped the target. The currently defined stop
38761 reasons are listed below. @var{aa} should be @samp{05}, the trap
38762 signal. At most one stop reason should be present.
38765 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38766 and go on to the next; this allows us to extend the protocol in the
38770 The currently defined stop reasons are:
38776 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38779 @cindex shared library events, remote reply
38781 The packet indicates that the loaded libraries have changed.
38782 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38783 list of loaded libraries. @var{r} is ignored.
38785 @cindex replay log events, remote reply
38787 The packet indicates that the target cannot continue replaying
38788 logged execution events, because it has reached the end (or the
38789 beginning when executing backward) of the log. The value of @var{r}
38790 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38791 for more information.
38795 @itemx W @var{AA} ; process:@var{pid}
38796 The process exited, and @var{AA} is the exit status. This is only
38797 applicable to certain targets.
38799 The second form of the response, including the process ID of the exited
38800 process, can be used only when @value{GDBN} has reported support for
38801 multiprocess protocol extensions; see @ref{multiprocess extensions}.
38802 The @var{pid} is formatted as a big-endian hex string.
38805 @itemx X @var{AA} ; process:@var{pid}
38806 The process terminated with signal @var{AA}.
38808 The second form of the response, including the process ID of the
38809 terminated process, can be used only when @value{GDBN} has reported
38810 support for multiprocess protocol extensions; see @ref{multiprocess
38811 extensions}. The @var{pid} is formatted as a big-endian hex string.
38813 @item O @var{XX}@dots{}
38814 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38815 written as the program's console output. This can happen at any time
38816 while the program is running and the debugger should continue to wait
38817 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38819 @item F @var{call-id},@var{parameter}@dots{}
38820 @var{call-id} is the identifier which says which host system call should
38821 be called. This is just the name of the function. Translation into the
38822 correct system call is only applicable as it's defined in @value{GDBN}.
38823 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38826 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38827 this very system call.
38829 The target replies with this packet when it expects @value{GDBN} to
38830 call a host system call on behalf of the target. @value{GDBN} replies
38831 with an appropriate @samp{F} packet and keeps up waiting for the next
38832 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38833 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38834 Protocol Extension}, for more details.
38838 @node General Query Packets
38839 @section General Query Packets
38840 @cindex remote query requests
38842 Packets starting with @samp{q} are @dfn{general query packets};
38843 packets starting with @samp{Q} are @dfn{general set packets}. General
38844 query and set packets are a semi-unified form for retrieving and
38845 sending information to and from the stub.
38847 The initial letter of a query or set packet is followed by a name
38848 indicating what sort of thing the packet applies to. For example,
38849 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38850 definitions with the stub. These packet names follow some
38855 The name must not contain commas, colons or semicolons.
38857 Most @value{GDBN} query and set packets have a leading upper case
38860 The names of custom vendor packets should use a company prefix, in
38861 lower case, followed by a period. For example, packets designed at
38862 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38863 foos) or @samp{Qacme.bar} (for setting bars).
38866 The name of a query or set packet should be separated from any
38867 parameters by a @samp{:}; the parameters themselves should be
38868 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38869 full packet name, and check for a separator or the end of the packet,
38870 in case two packet names share a common prefix. New packets should not begin
38871 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38872 packets predate these conventions, and have arguments without any terminator
38873 for the packet name; we suspect they are in widespread use in places that
38874 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38875 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38878 Like the descriptions of the other packets, each description here
38879 has a template showing the packet's overall syntax, followed by an
38880 explanation of the packet's meaning. We include spaces in some of the
38881 templates for clarity; these are not part of the packet's syntax. No
38882 @value{GDBN} packet uses spaces to separate its components.
38884 Here are the currently defined query and set packets:
38890 Turn on or off the agent as a helper to perform some debugging operations
38891 delegated from @value{GDBN} (@pxref{Control Agent}).
38893 @item QAllow:@var{op}:@var{val}@dots{}
38894 @cindex @samp{QAllow} packet
38895 Specify which operations @value{GDBN} expects to request of the
38896 target, as a semicolon-separated list of operation name and value
38897 pairs. Possible values for @var{op} include @samp{WriteReg},
38898 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38899 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38900 indicating that @value{GDBN} will not request the operation, or 1,
38901 indicating that it may. (The target can then use this to set up its
38902 own internals optimally, for instance if the debugger never expects to
38903 insert breakpoints, it may not need to install its own trap handler.)
38906 @cindex current thread, remote request
38907 @cindex @samp{qC} packet
38908 Return the current thread ID.
38912 @item QC @var{thread-id}
38913 Where @var{thread-id} is a thread ID as documented in
38914 @ref{thread-id syntax}.
38915 @item @r{(anything else)}
38916 Any other reply implies the old thread ID.
38919 @item qCRC:@var{addr},@var{length}
38920 @cindex CRC of memory block, remote request
38921 @cindex @samp{qCRC} packet
38922 Compute the CRC checksum of a block of memory using CRC-32 defined in
38923 IEEE 802.3. The CRC is computed byte at a time, taking the most
38924 significant bit of each byte first. The initial pattern code
38925 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
38927 @emph{Note:} This is the same CRC used in validating separate debug
38928 files (@pxref{Separate Debug Files, , Debugging Information in Separate
38929 Files}). However the algorithm is slightly different. When validating
38930 separate debug files, the CRC is computed taking the @emph{least}
38931 significant bit of each byte first, and the final result is inverted to
38932 detect trailing zeros.
38937 An error (such as memory fault)
38938 @item C @var{crc32}
38939 The specified memory region's checksum is @var{crc32}.
38942 @item QDisableRandomization:@var{value}
38943 @cindex disable address space randomization, remote request
38944 @cindex @samp{QDisableRandomization} packet
38945 Some target operating systems will randomize the virtual address space
38946 of the inferior process as a security feature, but provide a feature
38947 to disable such randomization, e.g.@: to allow for a more deterministic
38948 debugging experience. On such systems, this packet with a @var{value}
38949 of 1 directs the target to disable address space randomization for
38950 processes subsequently started via @samp{vRun} packets, while a packet
38951 with a @var{value} of 0 tells the target to enable address space
38954 This packet is only available in extended mode (@pxref{extended mode}).
38959 The request succeeded.
38962 An error occurred. @var{nn} are hex digits.
38965 An empty reply indicates that @samp{QDisableRandomization} is not supported
38969 This packet is not probed by default; the remote stub must request it,
38970 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38971 This should only be done on targets that actually support disabling
38972 address space randomization.
38975 @itemx qsThreadInfo
38976 @cindex list active threads, remote request
38977 @cindex @samp{qfThreadInfo} packet
38978 @cindex @samp{qsThreadInfo} packet
38979 Obtain a list of all active thread IDs from the target (OS). Since there
38980 may be too many active threads to fit into one reply packet, this query
38981 works iteratively: it may require more than one query/reply sequence to
38982 obtain the entire list of threads. The first query of the sequence will
38983 be the @samp{qfThreadInfo} query; subsequent queries in the
38984 sequence will be the @samp{qsThreadInfo} query.
38986 NOTE: This packet replaces the @samp{qL} query (see below).
38990 @item m @var{thread-id}
38992 @item m @var{thread-id},@var{thread-id}@dots{}
38993 a comma-separated list of thread IDs
38995 (lower case letter @samp{L}) denotes end of list.
38998 In response to each query, the target will reply with a list of one or
38999 more thread IDs, separated by commas.
39000 @value{GDBN} will respond to each reply with a request for more thread
39001 ids (using the @samp{qs} form of the query), until the target responds
39002 with @samp{l} (lower-case ell, for @dfn{last}).
39003 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
39006 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
39007 @cindex get thread-local storage address, remote request
39008 @cindex @samp{qGetTLSAddr} packet
39009 Fetch the address associated with thread local storage specified
39010 by @var{thread-id}, @var{offset}, and @var{lm}.
39012 @var{thread-id} is the thread ID associated with the
39013 thread for which to fetch the TLS address. @xref{thread-id syntax}.
39015 @var{offset} is the (big endian, hex encoded) offset associated with the
39016 thread local variable. (This offset is obtained from the debug
39017 information associated with the variable.)
39019 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
39020 load module associated with the thread local storage. For example,
39021 a @sc{gnu}/Linux system will pass the link map address of the shared
39022 object associated with the thread local storage under consideration.
39023 Other operating environments may choose to represent the load module
39024 differently, so the precise meaning of this parameter will vary.
39028 @item @var{XX}@dots{}
39029 Hex encoded (big endian) bytes representing the address of the thread
39030 local storage requested.
39033 An error occurred. @var{nn} are hex digits.
39036 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
39039 @item qGetTIBAddr:@var{thread-id}
39040 @cindex get thread information block address
39041 @cindex @samp{qGetTIBAddr} packet
39042 Fetch address of the Windows OS specific Thread Information Block.
39044 @var{thread-id} is the thread ID associated with the thread.
39048 @item @var{XX}@dots{}
39049 Hex encoded (big endian) bytes representing the linear address of the
39050 thread information block.
39053 An error occured. This means that either the thread was not found, or the
39054 address could not be retrieved.
39057 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
39060 @item qL @var{startflag} @var{threadcount} @var{nextthread}
39061 Obtain thread information from RTOS. Where: @var{startflag} (one hex
39062 digit) is one to indicate the first query and zero to indicate a
39063 subsequent query; @var{threadcount} (two hex digits) is the maximum
39064 number of threads the response packet can contain; and @var{nextthread}
39065 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
39066 returned in the response as @var{argthread}.
39068 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
39072 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
39073 Where: @var{count} (two hex digits) is the number of threads being
39074 returned; @var{done} (one hex digit) is zero to indicate more threads
39075 and one indicates no further threads; @var{argthreadid} (eight hex
39076 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
39077 is a sequence of thread IDs from the target. @var{threadid} (eight hex
39078 digits). See @code{remote.c:parse_threadlist_response()}.
39082 @cindex section offsets, remote request
39083 @cindex @samp{qOffsets} packet
39084 Get section offsets that the target used when relocating the downloaded
39089 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
39090 Relocate the @code{Text} section by @var{xxx} from its original address.
39091 Relocate the @code{Data} section by @var{yyy} from its original address.
39092 If the object file format provides segment information (e.g.@: @sc{elf}
39093 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
39094 segments by the supplied offsets.
39096 @emph{Note: while a @code{Bss} offset may be included in the response,
39097 @value{GDBN} ignores this and instead applies the @code{Data} offset
39098 to the @code{Bss} section.}
39100 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
39101 Relocate the first segment of the object file, which conventionally
39102 contains program code, to a starting address of @var{xxx}. If
39103 @samp{DataSeg} is specified, relocate the second segment, which
39104 conventionally contains modifiable data, to a starting address of
39105 @var{yyy}. @value{GDBN} will report an error if the object file
39106 does not contain segment information, or does not contain at least
39107 as many segments as mentioned in the reply. Extra segments are
39108 kept at fixed offsets relative to the last relocated segment.
39111 @item qP @var{mode} @var{thread-id}
39112 @cindex thread information, remote request
39113 @cindex @samp{qP} packet
39114 Returns information on @var{thread-id}. Where: @var{mode} is a hex
39115 encoded 32 bit mode; @var{thread-id} is a thread ID
39116 (@pxref{thread-id syntax}).
39118 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
39121 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
39125 @cindex non-stop mode, remote request
39126 @cindex @samp{QNonStop} packet
39128 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
39129 @xref{Remote Non-Stop}, for more information.
39134 The request succeeded.
39137 An error occurred. @var{nn} are hex digits.
39140 An empty reply indicates that @samp{QNonStop} is not supported by
39144 This packet is not probed by default; the remote stub must request it,
39145 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39146 Use of this packet is controlled by the @code{set non-stop} command;
39147 @pxref{Non-Stop Mode}.
39149 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39150 @cindex pass signals to inferior, remote request
39151 @cindex @samp{QPassSignals} packet
39152 @anchor{QPassSignals}
39153 Each listed @var{signal} should be passed directly to the inferior process.
39154 Signals are numbered identically to continue packets and stop replies
39155 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39156 strictly greater than the previous item. These signals do not need to stop
39157 the inferior, or be reported to @value{GDBN}. All other signals should be
39158 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
39159 combine; any earlier @samp{QPassSignals} list is completely replaced by the
39160 new list. This packet improves performance when using @samp{handle
39161 @var{signal} nostop noprint pass}.
39166 The request succeeded.
39169 An error occurred. @var{nn} are hex digits.
39172 An empty reply indicates that @samp{QPassSignals} is not supported by
39176 Use of this packet is controlled by the @code{set remote pass-signals}
39177 command (@pxref{Remote Configuration, set remote pass-signals}).
39178 This packet is not probed by default; the remote stub must request it,
39179 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39181 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39182 @cindex signals the inferior may see, remote request
39183 @cindex @samp{QProgramSignals} packet
39184 @anchor{QProgramSignals}
39185 Each listed @var{signal} may be delivered to the inferior process.
39186 Others should be silently discarded.
39188 In some cases, the remote stub may need to decide whether to deliver a
39189 signal to the program or not without @value{GDBN} involvement. One
39190 example of that is while detaching --- the program's threads may have
39191 stopped for signals that haven't yet had a chance of being reported to
39192 @value{GDBN}, and so the remote stub can use the signal list specified
39193 by this packet to know whether to deliver or ignore those pending
39196 This does not influence whether to deliver a signal as requested by a
39197 resumption packet (@pxref{vCont packet}).
39199 Signals are numbered identically to continue packets and stop replies
39200 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39201 strictly greater than the previous item. Multiple
39202 @samp{QProgramSignals} packets do not combine; any earlier
39203 @samp{QProgramSignals} list is completely replaced by the new list.
39208 The request succeeded.
39211 An error occurred. @var{nn} are hex digits.
39214 An empty reply indicates that @samp{QProgramSignals} is not supported
39218 Use of this packet is controlled by the @code{set remote program-signals}
39219 command (@pxref{Remote Configuration, set remote program-signals}).
39220 This packet is not probed by default; the remote stub must request it,
39221 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39223 @item qRcmd,@var{command}
39224 @cindex execute remote command, remote request
39225 @cindex @samp{qRcmd} packet
39226 @var{command} (hex encoded) is passed to the local interpreter for
39227 execution. Invalid commands should be reported using the output
39228 string. Before the final result packet, the target may also respond
39229 with a number of intermediate @samp{O@var{output}} console output
39230 packets. @emph{Implementors should note that providing access to a
39231 stubs's interpreter may have security implications}.
39236 A command response with no output.
39238 A command response with the hex encoded output string @var{OUTPUT}.
39240 Indicate a badly formed request.
39242 An empty reply indicates that @samp{qRcmd} is not recognized.
39245 (Note that the @code{qRcmd} packet's name is separated from the
39246 command by a @samp{,}, not a @samp{:}, contrary to the naming
39247 conventions above. Please don't use this packet as a model for new
39250 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
39251 @cindex searching memory, in remote debugging
39253 @cindex @samp{qSearch:memory} packet
39255 @cindex @samp{qSearch memory} packet
39256 @anchor{qSearch memory}
39257 Search @var{length} bytes at @var{address} for @var{search-pattern}.
39258 @var{address} and @var{length} are encoded in hex.
39259 @var{search-pattern} is a sequence of bytes, hex encoded.
39264 The pattern was not found.
39266 The pattern was found at @var{address}.
39268 A badly formed request or an error was encountered while searching memory.
39270 An empty reply indicates that @samp{qSearch:memory} is not recognized.
39273 @item QStartNoAckMode
39274 @cindex @samp{QStartNoAckMode} packet
39275 @anchor{QStartNoAckMode}
39276 Request that the remote stub disable the normal @samp{+}/@samp{-}
39277 protocol acknowledgments (@pxref{Packet Acknowledgment}).
39282 The stub has switched to no-acknowledgment mode.
39283 @value{GDBN} acknowledges this reponse,
39284 but neither the stub nor @value{GDBN} shall send or expect further
39285 @samp{+}/@samp{-} acknowledgments in the current connection.
39287 An empty reply indicates that the stub does not support no-acknowledgment mode.
39290 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
39291 @cindex supported packets, remote query
39292 @cindex features of the remote protocol
39293 @cindex @samp{qSupported} packet
39294 @anchor{qSupported}
39295 Tell the remote stub about features supported by @value{GDBN}, and
39296 query the stub for features it supports. This packet allows
39297 @value{GDBN} and the remote stub to take advantage of each others'
39298 features. @samp{qSupported} also consolidates multiple feature probes
39299 at startup, to improve @value{GDBN} performance---a single larger
39300 packet performs better than multiple smaller probe packets on
39301 high-latency links. Some features may enable behavior which must not
39302 be on by default, e.g.@: because it would confuse older clients or
39303 stubs. Other features may describe packets which could be
39304 automatically probed for, but are not. These features must be
39305 reported before @value{GDBN} will use them. This ``default
39306 unsupported'' behavior is not appropriate for all packets, but it
39307 helps to keep the initial connection time under control with new
39308 versions of @value{GDBN} which support increasing numbers of packets.
39312 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
39313 The stub supports or does not support each returned @var{stubfeature},
39314 depending on the form of each @var{stubfeature} (see below for the
39317 An empty reply indicates that @samp{qSupported} is not recognized,
39318 or that no features needed to be reported to @value{GDBN}.
39321 The allowed forms for each feature (either a @var{gdbfeature} in the
39322 @samp{qSupported} packet, or a @var{stubfeature} in the response)
39326 @item @var{name}=@var{value}
39327 The remote protocol feature @var{name} is supported, and associated
39328 with the specified @var{value}. The format of @var{value} depends
39329 on the feature, but it must not include a semicolon.
39331 The remote protocol feature @var{name} is supported, and does not
39332 need an associated value.
39334 The remote protocol feature @var{name} is not supported.
39336 The remote protocol feature @var{name} may be supported, and
39337 @value{GDBN} should auto-detect support in some other way when it is
39338 needed. This form will not be used for @var{gdbfeature} notifications,
39339 but may be used for @var{stubfeature} responses.
39342 Whenever the stub receives a @samp{qSupported} request, the
39343 supplied set of @value{GDBN} features should override any previous
39344 request. This allows @value{GDBN} to put the stub in a known
39345 state, even if the stub had previously been communicating with
39346 a different version of @value{GDBN}.
39348 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
39353 This feature indicates whether @value{GDBN} supports multiprocess
39354 extensions to the remote protocol. @value{GDBN} does not use such
39355 extensions unless the stub also reports that it supports them by
39356 including @samp{multiprocess+} in its @samp{qSupported} reply.
39357 @xref{multiprocess extensions}, for details.
39360 This feature indicates that @value{GDBN} supports the XML target
39361 description. If the stub sees @samp{xmlRegisters=} with target
39362 specific strings separated by a comma, it will report register
39366 This feature indicates whether @value{GDBN} supports the
39367 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
39368 instruction reply packet}).
39371 Stubs should ignore any unknown values for
39372 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
39373 packet supports receiving packets of unlimited length (earlier
39374 versions of @value{GDBN} may reject overly long responses). Additional values
39375 for @var{gdbfeature} may be defined in the future to let the stub take
39376 advantage of new features in @value{GDBN}, e.g.@: incompatible
39377 improvements in the remote protocol---the @samp{multiprocess} feature is
39378 an example of such a feature. The stub's reply should be independent
39379 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
39380 describes all the features it supports, and then the stub replies with
39381 all the features it supports.
39383 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
39384 responses, as long as each response uses one of the standard forms.
39386 Some features are flags. A stub which supports a flag feature
39387 should respond with a @samp{+} form response. Other features
39388 require values, and the stub should respond with an @samp{=}
39391 Each feature has a default value, which @value{GDBN} will use if
39392 @samp{qSupported} is not available or if the feature is not mentioned
39393 in the @samp{qSupported} response. The default values are fixed; a
39394 stub is free to omit any feature responses that match the defaults.
39396 Not all features can be probed, but for those which can, the probing
39397 mechanism is useful: in some cases, a stub's internal
39398 architecture may not allow the protocol layer to know some information
39399 about the underlying target in advance. This is especially common in
39400 stubs which may be configured for multiple targets.
39402 These are the currently defined stub features and their properties:
39404 @multitable @columnfractions 0.35 0.2 0.12 0.2
39405 @c NOTE: The first row should be @headitem, but we do not yet require
39406 @c a new enough version of Texinfo (4.7) to use @headitem.
39408 @tab Value Required
39412 @item @samp{PacketSize}
39417 @item @samp{qXfer:auxv:read}
39422 @item @samp{qXfer:btrace:read}
39427 @item @samp{qXfer:features:read}
39432 @item @samp{qXfer:libraries:read}
39437 @item @samp{qXfer:libraries-svr4:read}
39442 @item @samp{augmented-libraries-svr4-read}
39447 @item @samp{qXfer:memory-map:read}
39452 @item @samp{qXfer:sdata:read}
39457 @item @samp{qXfer:spu:read}
39462 @item @samp{qXfer:spu:write}
39467 @item @samp{qXfer:siginfo:read}
39472 @item @samp{qXfer:siginfo:write}
39477 @item @samp{qXfer:threads:read}
39482 @item @samp{qXfer:traceframe-info:read}
39487 @item @samp{qXfer:uib:read}
39492 @item @samp{qXfer:fdpic:read}
39497 @item @samp{Qbtrace:off}
39502 @item @samp{Qbtrace:bts}
39507 @item @samp{QNonStop}
39512 @item @samp{QPassSignals}
39517 @item @samp{QStartNoAckMode}
39522 @item @samp{multiprocess}
39527 @item @samp{ConditionalBreakpoints}
39532 @item @samp{ConditionalTracepoints}
39537 @item @samp{ReverseContinue}
39542 @item @samp{ReverseStep}
39547 @item @samp{TracepointSource}
39552 @item @samp{QAgent}
39557 @item @samp{QAllow}
39562 @item @samp{QDisableRandomization}
39567 @item @samp{EnableDisableTracepoints}
39572 @item @samp{QTBuffer:size}
39577 @item @samp{tracenz}
39582 @item @samp{BreakpointCommands}
39589 These are the currently defined stub features, in more detail:
39592 @cindex packet size, remote protocol
39593 @item PacketSize=@var{bytes}
39594 The remote stub can accept packets up to at least @var{bytes} in
39595 length. @value{GDBN} will send packets up to this size for bulk
39596 transfers, and will never send larger packets. This is a limit on the
39597 data characters in the packet, including the frame and checksum.
39598 There is no trailing NUL byte in a remote protocol packet; if the stub
39599 stores packets in a NUL-terminated format, it should allow an extra
39600 byte in its buffer for the NUL. If this stub feature is not supported,
39601 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39603 @item qXfer:auxv:read
39604 The remote stub understands the @samp{qXfer:auxv:read} packet
39605 (@pxref{qXfer auxiliary vector read}).
39607 @item qXfer:btrace:read
39608 The remote stub understands the @samp{qXfer:btrace:read}
39609 packet (@pxref{qXfer btrace read}).
39611 @item qXfer:features:read
39612 The remote stub understands the @samp{qXfer:features:read} packet
39613 (@pxref{qXfer target description read}).
39615 @item qXfer:libraries:read
39616 The remote stub understands the @samp{qXfer:libraries:read} packet
39617 (@pxref{qXfer library list read}).
39619 @item qXfer:libraries-svr4:read
39620 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39621 (@pxref{qXfer svr4 library list read}).
39623 @item augmented-libraries-svr4-read
39624 The remote stub understands the augmented form of the
39625 @samp{qXfer:libraries-svr4:read} packet
39626 (@pxref{qXfer svr4 library list read}).
39628 @item qXfer:memory-map:read
39629 The remote stub understands the @samp{qXfer:memory-map:read} packet
39630 (@pxref{qXfer memory map read}).
39632 @item qXfer:sdata:read
39633 The remote stub understands the @samp{qXfer:sdata:read} packet
39634 (@pxref{qXfer sdata read}).
39636 @item qXfer:spu:read
39637 The remote stub understands the @samp{qXfer:spu:read} packet
39638 (@pxref{qXfer spu read}).
39640 @item qXfer:spu:write
39641 The remote stub understands the @samp{qXfer:spu:write} packet
39642 (@pxref{qXfer spu write}).
39644 @item qXfer:siginfo:read
39645 The remote stub understands the @samp{qXfer:siginfo:read} packet
39646 (@pxref{qXfer siginfo read}).
39648 @item qXfer:siginfo:write
39649 The remote stub understands the @samp{qXfer:siginfo:write} packet
39650 (@pxref{qXfer siginfo write}).
39652 @item qXfer:threads:read
39653 The remote stub understands the @samp{qXfer:threads:read} packet
39654 (@pxref{qXfer threads read}).
39656 @item qXfer:traceframe-info:read
39657 The remote stub understands the @samp{qXfer:traceframe-info:read}
39658 packet (@pxref{qXfer traceframe info read}).
39660 @item qXfer:uib:read
39661 The remote stub understands the @samp{qXfer:uib:read}
39662 packet (@pxref{qXfer unwind info block}).
39664 @item qXfer:fdpic:read
39665 The remote stub understands the @samp{qXfer:fdpic:read}
39666 packet (@pxref{qXfer fdpic loadmap read}).
39669 The remote stub understands the @samp{QNonStop} packet
39670 (@pxref{QNonStop}).
39673 The remote stub understands the @samp{QPassSignals} packet
39674 (@pxref{QPassSignals}).
39676 @item QStartNoAckMode
39677 The remote stub understands the @samp{QStartNoAckMode} packet and
39678 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39681 @anchor{multiprocess extensions}
39682 @cindex multiprocess extensions, in remote protocol
39683 The remote stub understands the multiprocess extensions to the remote
39684 protocol syntax. The multiprocess extensions affect the syntax of
39685 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39686 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39687 replies. Note that reporting this feature indicates support for the
39688 syntactic extensions only, not that the stub necessarily supports
39689 debugging of more than one process at a time. The stub must not use
39690 multiprocess extensions in packet replies unless @value{GDBN} has also
39691 indicated it supports them in its @samp{qSupported} request.
39693 @item qXfer:osdata:read
39694 The remote stub understands the @samp{qXfer:osdata:read} packet
39695 ((@pxref{qXfer osdata read}).
39697 @item ConditionalBreakpoints
39698 The target accepts and implements evaluation of conditional expressions
39699 defined for breakpoints. The target will only report breakpoint triggers
39700 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39702 @item ConditionalTracepoints
39703 The remote stub accepts and implements conditional expressions defined
39704 for tracepoints (@pxref{Tracepoint Conditions}).
39706 @item ReverseContinue
39707 The remote stub accepts and implements the reverse continue packet
39711 The remote stub accepts and implements the reverse step packet
39714 @item TracepointSource
39715 The remote stub understands the @samp{QTDPsrc} packet that supplies
39716 the source form of tracepoint definitions.
39719 The remote stub understands the @samp{QAgent} packet.
39722 The remote stub understands the @samp{QAllow} packet.
39724 @item QDisableRandomization
39725 The remote stub understands the @samp{QDisableRandomization} packet.
39727 @item StaticTracepoint
39728 @cindex static tracepoints, in remote protocol
39729 The remote stub supports static tracepoints.
39731 @item InstallInTrace
39732 @anchor{install tracepoint in tracing}
39733 The remote stub supports installing tracepoint in tracing.
39735 @item EnableDisableTracepoints
39736 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39737 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39738 to be enabled and disabled while a trace experiment is running.
39740 @item QTBuffer:size
39741 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39742 packet that allows to change the size of the trace buffer.
39745 @cindex string tracing, in remote protocol
39746 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39747 See @ref{Bytecode Descriptions} for details about the bytecode.
39749 @item BreakpointCommands
39750 @cindex breakpoint commands, in remote protocol
39751 The remote stub supports running a breakpoint's command list itself,
39752 rather than reporting the hit to @value{GDBN}.
39755 The remote stub understands the @samp{Qbtrace:off} packet.
39758 The remote stub understands the @samp{Qbtrace:bts} packet.
39763 @cindex symbol lookup, remote request
39764 @cindex @samp{qSymbol} packet
39765 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39766 requests. Accept requests from the target for the values of symbols.
39771 The target does not need to look up any (more) symbols.
39772 @item qSymbol:@var{sym_name}
39773 The target requests the value of symbol @var{sym_name} (hex encoded).
39774 @value{GDBN} may provide the value by using the
39775 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39779 @item qSymbol:@var{sym_value}:@var{sym_name}
39780 Set the value of @var{sym_name} to @var{sym_value}.
39782 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39783 target has previously requested.
39785 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39786 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39792 The target does not need to look up any (more) symbols.
39793 @item qSymbol:@var{sym_name}
39794 The target requests the value of a new symbol @var{sym_name} (hex
39795 encoded). @value{GDBN} will continue to supply the values of symbols
39796 (if available), until the target ceases to request them.
39801 @itemx QTDisconnected
39808 @itemx qTMinFTPILen
39810 @xref{Tracepoint Packets}.
39812 @item qThreadExtraInfo,@var{thread-id}
39813 @cindex thread attributes info, remote request
39814 @cindex @samp{qThreadExtraInfo} packet
39815 Obtain a printable string description of a thread's attributes from
39816 the target OS. @var{thread-id} is a thread ID;
39817 see @ref{thread-id syntax}. This
39818 string may contain anything that the target OS thinks is interesting
39819 for @value{GDBN} to tell the user about the thread. The string is
39820 displayed in @value{GDBN}'s @code{info threads} display. Some
39821 examples of possible thread extra info strings are @samp{Runnable}, or
39822 @samp{Blocked on Mutex}.
39826 @item @var{XX}@dots{}
39827 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39828 comprising the printable string containing the extra information about
39829 the thread's attributes.
39832 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39833 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39834 conventions above. Please don't use this packet as a model for new
39853 @xref{Tracepoint Packets}.
39855 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39856 @cindex read special object, remote request
39857 @cindex @samp{qXfer} packet
39858 @anchor{qXfer read}
39859 Read uninterpreted bytes from the target's special data area
39860 identified by the keyword @var{object}. Request @var{length} bytes
39861 starting at @var{offset} bytes into the data. The content and
39862 encoding of @var{annex} is specific to @var{object}; it can supply
39863 additional details about what data to access.
39865 Here are the specific requests of this form defined so far. All
39866 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39867 formats, listed below.
39870 @item qXfer:auxv:read::@var{offset},@var{length}
39871 @anchor{qXfer auxiliary vector read}
39872 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39873 auxiliary vector}. Note @var{annex} must be empty.
39875 This packet is not probed by default; the remote stub must request it,
39876 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39878 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39879 @anchor{qXfer btrace read}
39881 Return a description of the current branch trace.
39882 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39883 packet may have one of the following values:
39887 Returns all available branch trace.
39890 Returns all available branch trace if the branch trace changed since
39891 the last read request.
39894 This packet is not probed by default; the remote stub must request it
39895 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39897 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39898 @anchor{qXfer target description read}
39899 Access the @dfn{target description}. @xref{Target Descriptions}. The
39900 annex specifies which XML document to access. The main description is
39901 always loaded from the @samp{target.xml} annex.
39903 This packet is not probed by default; the remote stub must request it,
39904 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39906 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39907 @anchor{qXfer library list read}
39908 Access the target's list of loaded libraries. @xref{Library List Format}.
39909 The annex part of the generic @samp{qXfer} packet must be empty
39910 (@pxref{qXfer read}).
39912 Targets which maintain a list of libraries in the program's memory do
39913 not need to implement this packet; it is designed for platforms where
39914 the operating system manages the list of loaded libraries.
39916 This packet is not probed by default; the remote stub must request it,
39917 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39919 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39920 @anchor{qXfer svr4 library list read}
39921 Access the target's list of loaded libraries when the target is an SVR4
39922 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39923 of the generic @samp{qXfer} packet must be empty unless the remote
39924 stub indicated it supports the augmented form of this packet
39925 by supplying an appropriate @samp{qSupported} response
39926 (@pxref{qXfer read}, @ref{qSupported}).
39928 This packet is optional for better performance on SVR4 targets.
39929 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39931 This packet is not probed by default; the remote stub must request it,
39932 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39934 If the remote stub indicates it supports the augmented form of this
39935 packet then the annex part of the generic @samp{qXfer} packet may
39936 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39937 arguments. The currently supported arguments are:
39940 @item start=@var{address}
39941 A hexadecimal number specifying the address of the @samp{struct
39942 link_map} to start reading the library list from. If unset or zero
39943 then the first @samp{struct link_map} in the library list will be
39944 chosen as the starting point.
39946 @item prev=@var{address}
39947 A hexadecimal number specifying the address of the @samp{struct
39948 link_map} immediately preceding the @samp{struct link_map}
39949 specified by the @samp{start} argument. If unset or zero then
39950 the remote stub will expect that no @samp{struct link_map}
39951 exists prior to the starting point.
39955 Arguments that are not understood by the remote stub will be silently
39958 @item qXfer:memory-map:read::@var{offset},@var{length}
39959 @anchor{qXfer memory map read}
39960 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39961 annex part of the generic @samp{qXfer} packet must be empty
39962 (@pxref{qXfer read}).
39964 This packet is not probed by default; the remote stub must request it,
39965 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39967 @item qXfer:sdata:read::@var{offset},@var{length}
39968 @anchor{qXfer sdata read}
39970 Read contents of the extra collected static tracepoint marker
39971 information. The annex part of the generic @samp{qXfer} packet must
39972 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39975 This packet is not probed by default; the remote stub must request it,
39976 by supplying an appropriate @samp{qSupported} response
39977 (@pxref{qSupported}).
39979 @item qXfer:siginfo:read::@var{offset},@var{length}
39980 @anchor{qXfer siginfo read}
39981 Read contents of the extra signal information on the target
39982 system. The annex part of the generic @samp{qXfer} packet must be
39983 empty (@pxref{qXfer read}).
39985 This packet is not probed by default; the remote stub must request it,
39986 by supplying an appropriate @samp{qSupported} response
39987 (@pxref{qSupported}).
39989 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39990 @anchor{qXfer spu read}
39991 Read contents of an @code{spufs} file on the target system. The
39992 annex specifies which file to read; it must be of the form
39993 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39994 in the target process, and @var{name} identifes the @code{spufs} file
39995 in that context to be accessed.
39997 This packet is not probed by default; the remote stub must request it,
39998 by supplying an appropriate @samp{qSupported} response
39999 (@pxref{qSupported}).
40001 @item qXfer:threads:read::@var{offset},@var{length}
40002 @anchor{qXfer threads read}
40003 Access the list of threads on target. @xref{Thread List Format}. The
40004 annex part of the generic @samp{qXfer} packet must be empty
40005 (@pxref{qXfer read}).
40007 This packet is not probed by default; the remote stub must request it,
40008 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40010 @item qXfer:traceframe-info:read::@var{offset},@var{length}
40011 @anchor{qXfer traceframe info read}
40013 Return a description of the current traceframe's contents.
40014 @xref{Traceframe Info Format}. The annex part of the generic
40015 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
40017 This packet is not probed by default; the remote stub must request it,
40018 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40020 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
40021 @anchor{qXfer unwind info block}
40023 Return the unwind information block for @var{pc}. This packet is used
40024 on OpenVMS/ia64 to ask the kernel unwind information.
40026 This packet is not probed by default.
40028 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
40029 @anchor{qXfer fdpic loadmap read}
40030 Read contents of @code{loadmap}s on the target system. The
40031 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
40032 executable @code{loadmap} or interpreter @code{loadmap} to read.
40034 This packet is not probed by default; the remote stub must request it,
40035 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40037 @item qXfer:osdata:read::@var{offset},@var{length}
40038 @anchor{qXfer osdata read}
40039 Access the target's @dfn{operating system information}.
40040 @xref{Operating System Information}.
40047 Data @var{data} (@pxref{Binary Data}) has been read from the
40048 target. There may be more data at a higher address (although
40049 it is permitted to return @samp{m} even for the last valid
40050 block of data, as long as at least one byte of data was read).
40051 @var{data} may have fewer bytes than the @var{length} in the
40055 Data @var{data} (@pxref{Binary Data}) has been read from the target.
40056 There is no more data to be read. @var{data} may have fewer bytes
40057 than the @var{length} in the request.
40060 The @var{offset} in the request is at the end of the data.
40061 There is no more data to be read.
40064 The request was malformed, or @var{annex} was invalid.
40067 The offset was invalid, or there was an error encountered reading the data.
40068 @var{nn} is a hex-encoded @code{errno} value.
40071 An empty reply indicates the @var{object} string was not recognized by
40072 the stub, or that the object does not support reading.
40075 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
40076 @cindex write data into object, remote request
40077 @anchor{qXfer write}
40078 Write uninterpreted bytes into the target's special data area
40079 identified by the keyword @var{object}, starting at @var{offset} bytes
40080 into the data. @var{data}@dots{} is the binary-encoded data
40081 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
40082 is specific to @var{object}; it can supply additional details about what data
40085 Here are the specific requests of this form defined so far. All
40086 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
40087 formats, listed below.
40090 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
40091 @anchor{qXfer siginfo write}
40092 Write @var{data} to the extra signal information on the target system.
40093 The annex part of the generic @samp{qXfer} packet must be
40094 empty (@pxref{qXfer write}).
40096 This packet is not probed by default; the remote stub must request it,
40097 by supplying an appropriate @samp{qSupported} response
40098 (@pxref{qSupported}).
40100 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
40101 @anchor{qXfer spu write}
40102 Write @var{data} to an @code{spufs} file on the target system. The
40103 annex specifies which file to write; it must be of the form
40104 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
40105 in the target process, and @var{name} identifes the @code{spufs} file
40106 in that context to be accessed.
40108 This packet is not probed by default; the remote stub must request it,
40109 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40115 @var{nn} (hex encoded) is the number of bytes written.
40116 This may be fewer bytes than supplied in the request.
40119 The request was malformed, or @var{annex} was invalid.
40122 The offset was invalid, or there was an error encountered writing the data.
40123 @var{nn} is a hex-encoded @code{errno} value.
40126 An empty reply indicates the @var{object} string was not
40127 recognized by the stub, or that the object does not support writing.
40130 @item qXfer:@var{object}:@var{operation}:@dots{}
40131 Requests of this form may be added in the future. When a stub does
40132 not recognize the @var{object} keyword, or its support for
40133 @var{object} does not recognize the @var{operation} keyword, the stub
40134 must respond with an empty packet.
40136 @item qAttached:@var{pid}
40137 @cindex query attached, remote request
40138 @cindex @samp{qAttached} packet
40139 Return an indication of whether the remote server attached to an
40140 existing process or created a new process. When the multiprocess
40141 protocol extensions are supported (@pxref{multiprocess extensions}),
40142 @var{pid} is an integer in hexadecimal format identifying the target
40143 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
40144 the query packet will be simplified as @samp{qAttached}.
40146 This query is used, for example, to know whether the remote process
40147 should be detached or killed when a @value{GDBN} session is ended with
40148 the @code{quit} command.
40153 The remote server attached to an existing process.
40155 The remote server created a new process.
40157 A badly formed request or an error was encountered.
40161 Enable branch tracing for the current thread using bts tracing.
40166 Branch tracing has been enabled.
40168 A badly formed request or an error was encountered.
40172 Disable branch tracing for the current thread.
40177 Branch tracing has been disabled.
40179 A badly formed request or an error was encountered.
40184 @node Architecture-Specific Protocol Details
40185 @section Architecture-Specific Protocol Details
40187 This section describes how the remote protocol is applied to specific
40188 target architectures. Also see @ref{Standard Target Features}, for
40189 details of XML target descriptions for each architecture.
40192 * ARM-Specific Protocol Details::
40193 * MIPS-Specific Protocol Details::
40196 @node ARM-Specific Protocol Details
40197 @subsection @acronym{ARM}-specific Protocol Details
40200 * ARM Breakpoint Kinds::
40203 @node ARM Breakpoint Kinds
40204 @subsubsection @acronym{ARM} Breakpoint Kinds
40205 @cindex breakpoint kinds, @acronym{ARM}
40207 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40212 16-bit Thumb mode breakpoint.
40215 32-bit Thumb mode (Thumb-2) breakpoint.
40218 32-bit @acronym{ARM} mode breakpoint.
40222 @node MIPS-Specific Protocol Details
40223 @subsection @acronym{MIPS}-specific Protocol Details
40226 * MIPS Register packet Format::
40227 * MIPS Breakpoint Kinds::
40230 @node MIPS Register packet Format
40231 @subsubsection @acronym{MIPS} Register Packet Format
40232 @cindex register packet format, @acronym{MIPS}
40234 The following @code{g}/@code{G} packets have previously been defined.
40235 In the below, some thirty-two bit registers are transferred as
40236 sixty-four bits. Those registers should be zero/sign extended (which?)
40237 to fill the space allocated. Register bytes are transferred in target
40238 byte order. The two nibbles within a register byte are transferred
40239 most-significant -- least-significant.
40244 All registers are transferred as thirty-two bit quantities in the order:
40245 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
40246 registers; fsr; fir; fp.
40249 All registers are transferred as sixty-four bit quantities (including
40250 thirty-two bit registers such as @code{sr}). The ordering is the same
40255 @node MIPS Breakpoint Kinds
40256 @subsubsection @acronym{MIPS} Breakpoint Kinds
40257 @cindex breakpoint kinds, @acronym{MIPS}
40259 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40264 16-bit @acronym{MIPS16} mode breakpoint.
40267 16-bit @acronym{microMIPS} mode breakpoint.
40270 32-bit standard @acronym{MIPS} mode breakpoint.
40273 32-bit @acronym{microMIPS} mode breakpoint.
40277 @node Tracepoint Packets
40278 @section Tracepoint Packets
40279 @cindex tracepoint packets
40280 @cindex packets, tracepoint
40282 Here we describe the packets @value{GDBN} uses to implement
40283 tracepoints (@pxref{Tracepoints}).
40287 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
40288 @cindex @samp{QTDP} packet
40289 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
40290 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
40291 the tracepoint is disabled. @var{step} is the tracepoint's step
40292 count, and @var{pass} is its pass count. If an @samp{F} is present,
40293 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
40294 the number of bytes that the target should copy elsewhere to make room
40295 for the tracepoint. If an @samp{X} is present, it introduces a
40296 tracepoint condition, which consists of a hexadecimal length, followed
40297 by a comma and hex-encoded bytes, in a manner similar to action
40298 encodings as described below. If the trailing @samp{-} is present,
40299 further @samp{QTDP} packets will follow to specify this tracepoint's
40305 The packet was understood and carried out.
40307 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40309 The packet was not recognized.
40312 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
40313 Define actions to be taken when a tracepoint is hit. @var{n} and
40314 @var{addr} must be the same as in the initial @samp{QTDP} packet for
40315 this tracepoint. This packet may only be sent immediately after
40316 another @samp{QTDP} packet that ended with a @samp{-}. If the
40317 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
40318 specifying more actions for this tracepoint.
40320 In the series of action packets for a given tracepoint, at most one
40321 can have an @samp{S} before its first @var{action}. If such a packet
40322 is sent, it and the following packets define ``while-stepping''
40323 actions. Any prior packets define ordinary actions --- that is, those
40324 taken when the tracepoint is first hit. If no action packet has an
40325 @samp{S}, then all the packets in the series specify ordinary
40326 tracepoint actions.
40328 The @samp{@var{action}@dots{}} portion of the packet is a series of
40329 actions, concatenated without separators. Each action has one of the
40335 Collect the registers whose bits are set in @var{mask}. @var{mask} is
40336 a hexadecimal number whose @var{i}'th bit is set if register number
40337 @var{i} should be collected. (The least significant bit is numbered
40338 zero.) Note that @var{mask} may be any number of digits long; it may
40339 not fit in a 32-bit word.
40341 @item M @var{basereg},@var{offset},@var{len}
40342 Collect @var{len} bytes of memory starting at the address in register
40343 number @var{basereg}, plus @var{offset}. If @var{basereg} is
40344 @samp{-1}, then the range has a fixed address: @var{offset} is the
40345 address of the lowest byte to collect. The @var{basereg},
40346 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
40347 values (the @samp{-1} value for @var{basereg} is a special case).
40349 @item X @var{len},@var{expr}
40350 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
40351 it directs. @var{expr} is an agent expression, as described in
40352 @ref{Agent Expressions}. Each byte of the expression is encoded as a
40353 two-digit hex number in the packet; @var{len} is the number of bytes
40354 in the expression (and thus one-half the number of hex digits in the
40359 Any number of actions may be packed together in a single @samp{QTDP}
40360 packet, as long as the packet does not exceed the maximum packet
40361 length (400 bytes, for many stubs). There may be only one @samp{R}
40362 action per tracepoint, and it must precede any @samp{M} or @samp{X}
40363 actions. Any registers referred to by @samp{M} and @samp{X} actions
40364 must be collected by a preceding @samp{R} action. (The
40365 ``while-stepping'' actions are treated as if they were attached to a
40366 separate tracepoint, as far as these restrictions are concerned.)
40371 The packet was understood and carried out.
40373 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40375 The packet was not recognized.
40378 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
40379 @cindex @samp{QTDPsrc} packet
40380 Specify a source string of tracepoint @var{n} at address @var{addr}.
40381 This is useful to get accurate reproduction of the tracepoints
40382 originally downloaded at the beginning of the trace run. @var{type}
40383 is the name of the tracepoint part, such as @samp{cond} for the
40384 tracepoint's conditional expression (see below for a list of types), while
40385 @var{bytes} is the string, encoded in hexadecimal.
40387 @var{start} is the offset of the @var{bytes} within the overall source
40388 string, while @var{slen} is the total length of the source string.
40389 This is intended for handling source strings that are longer than will
40390 fit in a single packet.
40391 @c Add detailed example when this info is moved into a dedicated
40392 @c tracepoint descriptions section.
40394 The available string types are @samp{at} for the location,
40395 @samp{cond} for the conditional, and @samp{cmd} for an action command.
40396 @value{GDBN} sends a separate packet for each command in the action
40397 list, in the same order in which the commands are stored in the list.
40399 The target does not need to do anything with source strings except
40400 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
40403 Although this packet is optional, and @value{GDBN} will only send it
40404 if the target replies with @samp{TracepointSource} @xref{General
40405 Query Packets}, it makes both disconnected tracing and trace files
40406 much easier to use. Otherwise the user must be careful that the
40407 tracepoints in effect while looking at trace frames are identical to
40408 the ones in effect during the trace run; even a small discrepancy
40409 could cause @samp{tdump} not to work, or a particular trace frame not
40412 @item QTDV:@var{n}:@var{value}
40413 @cindex define trace state variable, remote request
40414 @cindex @samp{QTDV} packet
40415 Create a new trace state variable, number @var{n}, with an initial
40416 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
40417 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
40418 the option of not using this packet for initial values of zero; the
40419 target should simply create the trace state variables as they are
40420 mentioned in expressions.
40422 @item QTFrame:@var{n}
40423 @cindex @samp{QTFrame} packet
40424 Select the @var{n}'th tracepoint frame from the buffer, and use the
40425 register and memory contents recorded there to answer subsequent
40426 request packets from @value{GDBN}.
40428 A successful reply from the stub indicates that the stub has found the
40429 requested frame. The response is a series of parts, concatenated
40430 without separators, describing the frame we selected. Each part has
40431 one of the following forms:
40435 The selected frame is number @var{n} in the trace frame buffer;
40436 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40437 was no frame matching the criteria in the request packet.
40440 The selected trace frame records a hit of tracepoint number @var{t};
40441 @var{t} is a hexadecimal number.
40445 @item QTFrame:pc:@var{addr}
40446 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40447 currently selected frame whose PC is @var{addr};
40448 @var{addr} is a hexadecimal number.
40450 @item QTFrame:tdp:@var{t}
40451 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40452 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40453 is a hexadecimal number.
40455 @item QTFrame:range:@var{start}:@var{end}
40456 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40457 currently selected frame whose PC is between @var{start} (inclusive)
40458 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40461 @item QTFrame:outside:@var{start}:@var{end}
40462 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40463 frame @emph{outside} the given range of addresses (exclusive).
40466 @cindex @samp{qTMinFTPILen} packet
40467 This packet requests the minimum length of instruction at which a fast
40468 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40469 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40470 it depends on the target system being able to create trampolines in
40471 the first 64K of memory, which might or might not be possible for that
40472 system. So the reply to this packet will be 4 if it is able to
40479 The minimum instruction length is currently unknown.
40481 The minimum instruction length is @var{length}, where @var{length} is greater
40482 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
40483 that a fast tracepoint may be placed on any instruction regardless of size.
40485 An error has occurred.
40487 An empty reply indicates that the request is not supported by the stub.
40491 @cindex @samp{QTStart} packet
40492 Begin the tracepoint experiment. Begin collecting data from
40493 tracepoint hits in the trace frame buffer. This packet supports the
40494 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40495 instruction reply packet}).
40498 @cindex @samp{QTStop} packet
40499 End the tracepoint experiment. Stop collecting trace frames.
40501 @item QTEnable:@var{n}:@var{addr}
40503 @cindex @samp{QTEnable} packet
40504 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40505 experiment. If the tracepoint was previously disabled, then collection
40506 of data from it will resume.
40508 @item QTDisable:@var{n}:@var{addr}
40510 @cindex @samp{QTDisable} packet
40511 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40512 experiment. No more data will be collected from the tracepoint unless
40513 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40516 @cindex @samp{QTinit} packet
40517 Clear the table of tracepoints, and empty the trace frame buffer.
40519 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40520 @cindex @samp{QTro} packet
40521 Establish the given ranges of memory as ``transparent''. The stub
40522 will answer requests for these ranges from memory's current contents,
40523 if they were not collected as part of the tracepoint hit.
40525 @value{GDBN} uses this to mark read-only regions of memory, like those
40526 containing program code. Since these areas never change, they should
40527 still have the same contents they did when the tracepoint was hit, so
40528 there's no reason for the stub to refuse to provide their contents.
40530 @item QTDisconnected:@var{value}
40531 @cindex @samp{QTDisconnected} packet
40532 Set the choice to what to do with the tracing run when @value{GDBN}
40533 disconnects from the target. A @var{value} of 1 directs the target to
40534 continue the tracing run, while 0 tells the target to stop tracing if
40535 @value{GDBN} is no longer in the picture.
40538 @cindex @samp{qTStatus} packet
40539 Ask the stub if there is a trace experiment running right now.
40541 The reply has the form:
40545 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40546 @var{running} is a single digit @code{1} if the trace is presently
40547 running, or @code{0} if not. It is followed by semicolon-separated
40548 optional fields that an agent may use to report additional status.
40552 If the trace is not running, the agent may report any of several
40553 explanations as one of the optional fields:
40558 No trace has been run yet.
40560 @item tstop[:@var{text}]:0
40561 The trace was stopped by a user-originated stop command. The optional
40562 @var{text} field is a user-supplied string supplied as part of the
40563 stop command (for instance, an explanation of why the trace was
40564 stopped manually). It is hex-encoded.
40567 The trace stopped because the trace buffer filled up.
40569 @item tdisconnected:0
40570 The trace stopped because @value{GDBN} disconnected from the target.
40572 @item tpasscount:@var{tpnum}
40573 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40575 @item terror:@var{text}:@var{tpnum}
40576 The trace stopped because tracepoint @var{tpnum} had an error. The
40577 string @var{text} is available to describe the nature of the error
40578 (for instance, a divide by zero in the condition expression).
40579 @var{text} is hex encoded.
40582 The trace stopped for some other reason.
40586 Additional optional fields supply statistical and other information.
40587 Although not required, they are extremely useful for users monitoring
40588 the progress of a trace run. If a trace has stopped, and these
40589 numbers are reported, they must reflect the state of the just-stopped
40594 @item tframes:@var{n}
40595 The number of trace frames in the buffer.
40597 @item tcreated:@var{n}
40598 The total number of trace frames created during the run. This may
40599 be larger than the trace frame count, if the buffer is circular.
40601 @item tsize:@var{n}
40602 The total size of the trace buffer, in bytes.
40604 @item tfree:@var{n}
40605 The number of bytes still unused in the buffer.
40607 @item circular:@var{n}
40608 The value of the circular trace buffer flag. @code{1} means that the
40609 trace buffer is circular and old trace frames will be discarded if
40610 necessary to make room, @code{0} means that the trace buffer is linear
40613 @item disconn:@var{n}
40614 The value of the disconnected tracing flag. @code{1} means that
40615 tracing will continue after @value{GDBN} disconnects, @code{0} means
40616 that the trace run will stop.
40620 @item qTP:@var{tp}:@var{addr}
40621 @cindex tracepoint status, remote request
40622 @cindex @samp{qTP} packet
40623 Ask the stub for the current state of tracepoint number @var{tp} at
40624 address @var{addr}.
40628 @item V@var{hits}:@var{usage}
40629 The tracepoint has been hit @var{hits} times so far during the trace
40630 run, and accounts for @var{usage} in the trace buffer. Note that
40631 @code{while-stepping} steps are not counted as separate hits, but the
40632 steps' space consumption is added into the usage number.
40636 @item qTV:@var{var}
40637 @cindex trace state variable value, remote request
40638 @cindex @samp{qTV} packet
40639 Ask the stub for the value of the trace state variable number @var{var}.
40644 The value of the variable is @var{value}. This will be the current
40645 value of the variable if the user is examining a running target, or a
40646 saved value if the variable was collected in the trace frame that the
40647 user is looking at. Note that multiple requests may result in
40648 different reply values, such as when requesting values while the
40649 program is running.
40652 The value of the variable is unknown. This would occur, for example,
40653 if the user is examining a trace frame in which the requested variable
40658 @cindex @samp{qTfP} packet
40660 @cindex @samp{qTsP} packet
40661 These packets request data about tracepoints that are being used by
40662 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40663 of data, and multiple @code{qTsP} to get additional pieces. Replies
40664 to these packets generally take the form of the @code{QTDP} packets
40665 that define tracepoints. (FIXME add detailed syntax)
40668 @cindex @samp{qTfV} packet
40670 @cindex @samp{qTsV} packet
40671 These packets request data about trace state variables that are on the
40672 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40673 and multiple @code{qTsV} to get additional variables. Replies to
40674 these packets follow the syntax of the @code{QTDV} packets that define
40675 trace state variables.
40681 @cindex @samp{qTfSTM} packet
40682 @cindex @samp{qTsSTM} packet
40683 These packets request data about static tracepoint markers that exist
40684 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40685 first piece of data, and multiple @code{qTsSTM} to get additional
40686 pieces. Replies to these packets take the following form:
40690 @item m @var{address}:@var{id}:@var{extra}
40692 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40693 a comma-separated list of markers
40695 (lower case letter @samp{L}) denotes end of list.
40697 An error occurred. @var{nn} are hex digits.
40699 An empty reply indicates that the request is not supported by the
40703 @var{address} is encoded in hex.
40704 @var{id} and @var{extra} are strings encoded in hex.
40706 In response to each query, the target will reply with a list of one or
40707 more markers, separated by commas. @value{GDBN} will respond to each
40708 reply with a request for more markers (using the @samp{qs} form of the
40709 query), until the target responds with @samp{l} (lower-case ell, for
40712 @item qTSTMat:@var{address}
40714 @cindex @samp{qTSTMat} packet
40715 This packets requests data about static tracepoint markers in the
40716 target program at @var{address}. Replies to this packet follow the
40717 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40718 tracepoint markers.
40720 @item QTSave:@var{filename}
40721 @cindex @samp{QTSave} packet
40722 This packet directs the target to save trace data to the file name
40723 @var{filename} in the target's filesystem. @var{filename} is encoded
40724 as a hex string; the interpretation of the file name (relative vs
40725 absolute, wild cards, etc) is up to the target.
40727 @item qTBuffer:@var{offset},@var{len}
40728 @cindex @samp{qTBuffer} packet
40729 Return up to @var{len} bytes of the current contents of trace buffer,
40730 starting at @var{offset}. The trace buffer is treated as if it were
40731 a contiguous collection of traceframes, as per the trace file format.
40732 The reply consists as many hex-encoded bytes as the target can deliver
40733 in a packet; it is not an error to return fewer than were asked for.
40734 A reply consisting of just @code{l} indicates that no bytes are
40737 @item QTBuffer:circular:@var{value}
40738 This packet directs the target to use a circular trace buffer if
40739 @var{value} is 1, or a linear buffer if the value is 0.
40741 @item QTBuffer:size:@var{size}
40742 @anchor{QTBuffer-size}
40743 @cindex @samp{QTBuffer size} packet
40744 This packet directs the target to make the trace buffer be of size
40745 @var{size} if possible. A value of @code{-1} tells the target to
40746 use whatever size it prefers.
40748 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40749 @cindex @samp{QTNotes} packet
40750 This packet adds optional textual notes to the trace run. Allowable
40751 types include @code{user}, @code{notes}, and @code{tstop}, the
40752 @var{text} fields are arbitrary strings, hex-encoded.
40756 @subsection Relocate instruction reply packet
40757 When installing fast tracepoints in memory, the target may need to
40758 relocate the instruction currently at the tracepoint address to a
40759 different address in memory. For most instructions, a simple copy is
40760 enough, but, for example, call instructions that implicitly push the
40761 return address on the stack, and relative branches or other
40762 PC-relative instructions require offset adjustment, so that the effect
40763 of executing the instruction at a different address is the same as if
40764 it had executed in the original location.
40766 In response to several of the tracepoint packets, the target may also
40767 respond with a number of intermediate @samp{qRelocInsn} request
40768 packets before the final result packet, to have @value{GDBN} handle
40769 this relocation operation. If a packet supports this mechanism, its
40770 documentation will explicitly say so. See for example the above
40771 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40772 format of the request is:
40775 @item qRelocInsn:@var{from};@var{to}
40777 This requests @value{GDBN} to copy instruction at address @var{from}
40778 to address @var{to}, possibly adjusted so that executing the
40779 instruction at @var{to} has the same effect as executing it at
40780 @var{from}. @value{GDBN} writes the adjusted instruction to target
40781 memory starting at @var{to}.
40786 @item qRelocInsn:@var{adjusted_size}
40787 Informs the stub the relocation is complete. @var{adjusted_size} is
40788 the length in bytes of resulting relocated instruction sequence.
40790 A badly formed request was detected, or an error was encountered while
40791 relocating the instruction.
40794 @node Host I/O Packets
40795 @section Host I/O Packets
40796 @cindex Host I/O, remote protocol
40797 @cindex file transfer, remote protocol
40799 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40800 operations on the far side of a remote link. For example, Host I/O is
40801 used to upload and download files to a remote target with its own
40802 filesystem. Host I/O uses the same constant values and data structure
40803 layout as the target-initiated File-I/O protocol. However, the
40804 Host I/O packets are structured differently. The target-initiated
40805 protocol relies on target memory to store parameters and buffers.
40806 Host I/O requests are initiated by @value{GDBN}, and the
40807 target's memory is not involved. @xref{File-I/O Remote Protocol
40808 Extension}, for more details on the target-initiated protocol.
40810 The Host I/O request packets all encode a single operation along with
40811 its arguments. They have this format:
40815 @item vFile:@var{operation}: @var{parameter}@dots{}
40816 @var{operation} is the name of the particular request; the target
40817 should compare the entire packet name up to the second colon when checking
40818 for a supported operation. The format of @var{parameter} depends on
40819 the operation. Numbers are always passed in hexadecimal. Negative
40820 numbers have an explicit minus sign (i.e.@: two's complement is not
40821 used). Strings (e.g.@: filenames) are encoded as a series of
40822 hexadecimal bytes. The last argument to a system call may be a
40823 buffer of escaped binary data (@pxref{Binary Data}).
40827 The valid responses to Host I/O packets are:
40831 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40832 @var{result} is the integer value returned by this operation, usually
40833 non-negative for success and -1 for errors. If an error has occured,
40834 @var{errno} will be included in the result. @var{errno} will have a
40835 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40836 operations which return data, @var{attachment} supplies the data as a
40837 binary buffer. Binary buffers in response packets are escaped in the
40838 normal way (@pxref{Binary Data}). See the individual packet
40839 documentation for the interpretation of @var{result} and
40843 An empty response indicates that this operation is not recognized.
40847 These are the supported Host I/O operations:
40850 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
40851 Open a file at @var{pathname} and return a file descriptor for it, or
40852 return -1 if an error occurs. @var{pathname} is a string,
40853 @var{flags} is an integer indicating a mask of open flags
40854 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40855 of mode bits to use if the file is created (@pxref{mode_t Values}).
40856 @xref{open}, for details of the open flags and mode values.
40858 @item vFile:close: @var{fd}
40859 Close the open file corresponding to @var{fd} and return 0, or
40860 -1 if an error occurs.
40862 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40863 Read data from the open file corresponding to @var{fd}. Up to
40864 @var{count} bytes will be read from the file, starting at @var{offset}
40865 relative to the start of the file. The target may read fewer bytes;
40866 common reasons include packet size limits and an end-of-file
40867 condition. The number of bytes read is returned. Zero should only be
40868 returned for a successful read at the end of the file, or if
40869 @var{count} was zero.
40871 The data read should be returned as a binary attachment on success.
40872 If zero bytes were read, the response should include an empty binary
40873 attachment (i.e.@: a trailing semicolon). The return value is the
40874 number of target bytes read; the binary attachment may be longer if
40875 some characters were escaped.
40877 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40878 Write @var{data} (a binary buffer) to the open file corresponding
40879 to @var{fd}. Start the write at @var{offset} from the start of the
40880 file. Unlike many @code{write} system calls, there is no
40881 separate @var{count} argument; the length of @var{data} in the
40882 packet is used. @samp{vFile:write} returns the number of bytes written,
40883 which may be shorter than the length of @var{data}, or -1 if an
40886 @item vFile:unlink: @var{pathname}
40887 Delete the file at @var{pathname} on the target. Return 0,
40888 or -1 if an error occurs. @var{pathname} is a string.
40890 @item vFile:readlink: @var{filename}
40891 Read value of symbolic link @var{filename} on the target. Return
40892 the number of bytes read, or -1 if an error occurs.
40894 The data read should be returned as a binary attachment on success.
40895 If zero bytes were read, the response should include an empty binary
40896 attachment (i.e.@: a trailing semicolon). The return value is the
40897 number of target bytes read; the binary attachment may be longer if
40898 some characters were escaped.
40903 @section Interrupts
40904 @cindex interrupts (remote protocol)
40906 When a program on the remote target is running, @value{GDBN} may
40907 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
40908 a @code{BREAK} followed by @code{g},
40909 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40911 The precise meaning of @code{BREAK} is defined by the transport
40912 mechanism and may, in fact, be undefined. @value{GDBN} does not
40913 currently define a @code{BREAK} mechanism for any of the network
40914 interfaces except for TCP, in which case @value{GDBN} sends the
40915 @code{telnet} BREAK sequence.
40917 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40918 transport mechanisms. It is represented by sending the single byte
40919 @code{0x03} without any of the usual packet overhead described in
40920 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40921 transmitted as part of a packet, it is considered to be packet data
40922 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40923 (@pxref{X packet}), used for binary downloads, may include an unescaped
40924 @code{0x03} as part of its packet.
40926 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40927 When Linux kernel receives this sequence from serial port,
40928 it stops execution and connects to gdb.
40930 Stubs are not required to recognize these interrupt mechanisms and the
40931 precise meaning associated with receipt of the interrupt is
40932 implementation defined. If the target supports debugging of multiple
40933 threads and/or processes, it should attempt to interrupt all
40934 currently-executing threads and processes.
40935 If the stub is successful at interrupting the
40936 running program, it should send one of the stop
40937 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40938 of successfully stopping the program in all-stop mode, and a stop reply
40939 for each stopped thread in non-stop mode.
40940 Interrupts received while the
40941 program is stopped are discarded.
40943 @node Notification Packets
40944 @section Notification Packets
40945 @cindex notification packets
40946 @cindex packets, notification
40948 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40949 packets that require no acknowledgment. Both the GDB and the stub
40950 may send notifications (although the only notifications defined at
40951 present are sent by the stub). Notifications carry information
40952 without incurring the round-trip latency of an acknowledgment, and so
40953 are useful for low-impact communications where occasional packet loss
40956 A notification packet has the form @samp{% @var{data} #
40957 @var{checksum}}, where @var{data} is the content of the notification,
40958 and @var{checksum} is a checksum of @var{data}, computed and formatted
40959 as for ordinary @value{GDBN} packets. A notification's @var{data}
40960 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40961 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40962 to acknowledge the notification's receipt or to report its corruption.
40964 Every notification's @var{data} begins with a name, which contains no
40965 colon characters, followed by a colon character.
40967 Recipients should silently ignore corrupted notifications and
40968 notifications they do not understand. Recipients should restart
40969 timeout periods on receipt of a well-formed notification, whether or
40970 not they understand it.
40972 Senders should only send the notifications described here when this
40973 protocol description specifies that they are permitted. In the
40974 future, we may extend the protocol to permit existing notifications in
40975 new contexts; this rule helps older senders avoid confusing newer
40978 (Older versions of @value{GDBN} ignore bytes received until they see
40979 the @samp{$} byte that begins an ordinary packet, so new stubs may
40980 transmit notifications without fear of confusing older clients. There
40981 are no notifications defined for @value{GDBN} to send at the moment, but we
40982 assume that most older stubs would ignore them, as well.)
40984 Each notification is comprised of three parts:
40986 @item @var{name}:@var{event}
40987 The notification packet is sent by the side that initiates the
40988 exchange (currently, only the stub does that), with @var{event}
40989 carrying the specific information about the notification.
40990 @var{name} is the name of the notification.
40992 The acknowledge sent by the other side, usually @value{GDBN}, to
40993 acknowledge the exchange and request the event.
40996 The purpose of an asynchronous notification mechanism is to report to
40997 @value{GDBN} that something interesting happened in the remote stub.
40999 The remote stub may send notification @var{name}:@var{event}
41000 at any time, but @value{GDBN} acknowledges the notification when
41001 appropriate. The notification event is pending before @value{GDBN}
41002 acknowledges. Only one notification at a time may be pending; if
41003 additional events occur before @value{GDBN} has acknowledged the
41004 previous notification, they must be queued by the stub for later
41005 synchronous transmission in response to @var{ack} packets from
41006 @value{GDBN}. Because the notification mechanism is unreliable,
41007 the stub is permitted to resend a notification if it believes
41008 @value{GDBN} may not have received it.
41010 Specifically, notifications may appear when @value{GDBN} is not
41011 otherwise reading input from the stub, or when @value{GDBN} is
41012 expecting to read a normal synchronous response or a
41013 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
41014 Notification packets are distinct from any other communication from
41015 the stub so there is no ambiguity.
41017 After receiving a notification, @value{GDBN} shall acknowledge it by
41018 sending a @var{ack} packet as a regular, synchronous request to the
41019 stub. Such acknowledgment is not required to happen immediately, as
41020 @value{GDBN} is permitted to send other, unrelated packets to the
41021 stub first, which the stub should process normally.
41023 Upon receiving a @var{ack} packet, if the stub has other queued
41024 events to report to @value{GDBN}, it shall respond by sending a
41025 normal @var{event}. @value{GDBN} shall then send another @var{ack}
41026 packet to solicit further responses; again, it is permitted to send
41027 other, unrelated packets as well which the stub should process
41030 If the stub receives a @var{ack} packet and there are no additional
41031 @var{event} to report, the stub shall return an @samp{OK} response.
41032 At this point, @value{GDBN} has finished processing a notification
41033 and the stub has completed sending any queued events. @value{GDBN}
41034 won't accept any new notifications until the final @samp{OK} is
41035 received . If further notification events occur, the stub shall send
41036 a new notification, @value{GDBN} shall accept the notification, and
41037 the process shall be repeated.
41039 The process of asynchronous notification can be illustrated by the
41042 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
41045 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
41047 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
41052 The following notifications are defined:
41053 @multitable @columnfractions 0.12 0.12 0.38 0.38
41062 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
41063 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
41064 for information on how these notifications are acknowledged by
41066 @tab Report an asynchronous stop event in non-stop mode.
41070 @node Remote Non-Stop
41071 @section Remote Protocol Support for Non-Stop Mode
41073 @value{GDBN}'s remote protocol supports non-stop debugging of
41074 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
41075 supports non-stop mode, it should report that to @value{GDBN} by including
41076 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
41078 @value{GDBN} typically sends a @samp{QNonStop} packet only when
41079 establishing a new connection with the stub. Entering non-stop mode
41080 does not alter the state of any currently-running threads, but targets
41081 must stop all threads in any already-attached processes when entering
41082 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
41083 probe the target state after a mode change.
41085 In non-stop mode, when an attached process encounters an event that
41086 would otherwise be reported with a stop reply, it uses the
41087 asynchronous notification mechanism (@pxref{Notification Packets}) to
41088 inform @value{GDBN}. In contrast to all-stop mode, where all threads
41089 in all processes are stopped when a stop reply is sent, in non-stop
41090 mode only the thread reporting the stop event is stopped. That is,
41091 when reporting a @samp{S} or @samp{T} response to indicate completion
41092 of a step operation, hitting a breakpoint, or a fault, only the
41093 affected thread is stopped; any other still-running threads continue
41094 to run. When reporting a @samp{W} or @samp{X} response, all running
41095 threads belonging to other attached processes continue to run.
41097 In non-stop mode, the target shall respond to the @samp{?} packet as
41098 follows. First, any incomplete stop reply notification/@samp{vStopped}
41099 sequence in progress is abandoned. The target must begin a new
41100 sequence reporting stop events for all stopped threads, whether or not
41101 it has previously reported those events to @value{GDBN}. The first
41102 stop reply is sent as a synchronous reply to the @samp{?} packet, and
41103 subsequent stop replies are sent as responses to @samp{vStopped} packets
41104 using the mechanism described above. The target must not send
41105 asynchronous stop reply notifications until the sequence is complete.
41106 If all threads are running when the target receives the @samp{?} packet,
41107 or if the target is not attached to any process, it shall respond
41110 @node Packet Acknowledgment
41111 @section Packet Acknowledgment
41113 @cindex acknowledgment, for @value{GDBN} remote
41114 @cindex packet acknowledgment, for @value{GDBN} remote
41115 By default, when either the host or the target machine receives a packet,
41116 the first response expected is an acknowledgment: either @samp{+} (to indicate
41117 the package was received correctly) or @samp{-} (to request retransmission).
41118 This mechanism allows the @value{GDBN} remote protocol to operate over
41119 unreliable transport mechanisms, such as a serial line.
41121 In cases where the transport mechanism is itself reliable (such as a pipe or
41122 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
41123 It may be desirable to disable them in that case to reduce communication
41124 overhead, or for other reasons. This can be accomplished by means of the
41125 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
41127 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
41128 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
41129 and response format still includes the normal checksum, as described in
41130 @ref{Overview}, but the checksum may be ignored by the receiver.
41132 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
41133 no-acknowledgment mode, it should report that to @value{GDBN}
41134 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
41135 @pxref{qSupported}.
41136 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
41137 disabled via the @code{set remote noack-packet off} command
41138 (@pxref{Remote Configuration}),
41139 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
41140 Only then may the stub actually turn off packet acknowledgments.
41141 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
41142 response, which can be safely ignored by the stub.
41144 Note that @code{set remote noack-packet} command only affects negotiation
41145 between @value{GDBN} and the stub when subsequent connections are made;
41146 it does not affect the protocol acknowledgment state for any current
41148 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
41149 new connection is established,
41150 there is also no protocol request to re-enable the acknowledgments
41151 for the current connection, once disabled.
41156 Example sequence of a target being re-started. Notice how the restart
41157 does not get any direct output:
41162 @emph{target restarts}
41165 <- @code{T001:1234123412341234}
41169 Example sequence of a target being stepped by a single instruction:
41172 -> @code{G1445@dots{}}
41177 <- @code{T001:1234123412341234}
41181 <- @code{1455@dots{}}
41185 @node File-I/O Remote Protocol Extension
41186 @section File-I/O Remote Protocol Extension
41187 @cindex File-I/O remote protocol extension
41190 * File-I/O Overview::
41191 * Protocol Basics::
41192 * The F Request Packet::
41193 * The F Reply Packet::
41194 * The Ctrl-C Message::
41196 * List of Supported Calls::
41197 * Protocol-specific Representation of Datatypes::
41199 * File-I/O Examples::
41202 @node File-I/O Overview
41203 @subsection File-I/O Overview
41204 @cindex file-i/o overview
41206 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
41207 target to use the host's file system and console I/O to perform various
41208 system calls. System calls on the target system are translated into a
41209 remote protocol packet to the host system, which then performs the needed
41210 actions and returns a response packet to the target system.
41211 This simulates file system operations even on targets that lack file systems.
41213 The protocol is defined to be independent of both the host and target systems.
41214 It uses its own internal representation of datatypes and values. Both
41215 @value{GDBN} and the target's @value{GDBN} stub are responsible for
41216 translating the system-dependent value representations into the internal
41217 protocol representations when data is transmitted.
41219 The communication is synchronous. A system call is possible only when
41220 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
41221 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
41222 the target is stopped to allow deterministic access to the target's
41223 memory. Therefore File-I/O is not interruptible by target signals. On
41224 the other hand, it is possible to interrupt File-I/O by a user interrupt
41225 (@samp{Ctrl-C}) within @value{GDBN}.
41227 The target's request to perform a host system call does not finish
41228 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
41229 after finishing the system call, the target returns to continuing the
41230 previous activity (continue, step). No additional continue or step
41231 request from @value{GDBN} is required.
41234 (@value{GDBP}) continue
41235 <- target requests 'system call X'
41236 target is stopped, @value{GDBN} executes system call
41237 -> @value{GDBN} returns result
41238 ... target continues, @value{GDBN} returns to wait for the target
41239 <- target hits breakpoint and sends a Txx packet
41242 The protocol only supports I/O on the console and to regular files on
41243 the host file system. Character or block special devices, pipes,
41244 named pipes, sockets or any other communication method on the host
41245 system are not supported by this protocol.
41247 File I/O is not supported in non-stop mode.
41249 @node Protocol Basics
41250 @subsection Protocol Basics
41251 @cindex protocol basics, file-i/o
41253 The File-I/O protocol uses the @code{F} packet as the request as well
41254 as reply packet. Since a File-I/O system call can only occur when
41255 @value{GDBN} is waiting for a response from the continuing or stepping target,
41256 the File-I/O request is a reply that @value{GDBN} has to expect as a result
41257 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
41258 This @code{F} packet contains all information needed to allow @value{GDBN}
41259 to call the appropriate host system call:
41263 A unique identifier for the requested system call.
41266 All parameters to the system call. Pointers are given as addresses
41267 in the target memory address space. Pointers to strings are given as
41268 pointer/length pair. Numerical values are given as they are.
41269 Numerical control flags are given in a protocol-specific representation.
41273 At this point, @value{GDBN} has to perform the following actions.
41277 If the parameters include pointer values to data needed as input to a
41278 system call, @value{GDBN} requests this data from the target with a
41279 standard @code{m} packet request. This additional communication has to be
41280 expected by the target implementation and is handled as any other @code{m}
41284 @value{GDBN} translates all value from protocol representation to host
41285 representation as needed. Datatypes are coerced into the host types.
41288 @value{GDBN} calls the system call.
41291 It then coerces datatypes back to protocol representation.
41294 If the system call is expected to return data in buffer space specified
41295 by pointer parameters to the call, the data is transmitted to the
41296 target using a @code{M} or @code{X} packet. This packet has to be expected
41297 by the target implementation and is handled as any other @code{M} or @code{X}
41302 Eventually @value{GDBN} replies with another @code{F} packet which contains all
41303 necessary information for the target to continue. This at least contains
41310 @code{errno}, if has been changed by the system call.
41317 After having done the needed type and value coercion, the target continues
41318 the latest continue or step action.
41320 @node The F Request Packet
41321 @subsection The @code{F} Request Packet
41322 @cindex file-i/o request packet
41323 @cindex @code{F} request packet
41325 The @code{F} request packet has the following format:
41328 @item F@var{call-id},@var{parameter@dots{}}
41330 @var{call-id} is the identifier to indicate the host system call to be called.
41331 This is just the name of the function.
41333 @var{parameter@dots{}} are the parameters to the system call.
41334 Parameters are hexadecimal integer values, either the actual values in case
41335 of scalar datatypes, pointers to target buffer space in case of compound
41336 datatypes and unspecified memory areas, or pointer/length pairs in case
41337 of string parameters. These are appended to the @var{call-id} as a
41338 comma-delimited list. All values are transmitted in ASCII
41339 string representation, pointer/length pairs separated by a slash.
41345 @node The F Reply Packet
41346 @subsection The @code{F} Reply Packet
41347 @cindex file-i/o reply packet
41348 @cindex @code{F} reply packet
41350 The @code{F} reply packet has the following format:
41354 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
41356 @var{retcode} is the return code of the system call as hexadecimal value.
41358 @var{errno} is the @code{errno} set by the call, in protocol-specific
41360 This parameter can be omitted if the call was successful.
41362 @var{Ctrl-C flag} is only sent if the user requested a break. In this
41363 case, @var{errno} must be sent as well, even if the call was successful.
41364 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
41371 or, if the call was interrupted before the host call has been performed:
41378 assuming 4 is the protocol-specific representation of @code{EINTR}.
41383 @node The Ctrl-C Message
41384 @subsection The @samp{Ctrl-C} Message
41385 @cindex ctrl-c message, in file-i/o protocol
41387 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
41388 reply packet (@pxref{The F Reply Packet}),
41389 the target should behave as if it had
41390 gotten a break message. The meaning for the target is ``system call
41391 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
41392 (as with a break message) and return to @value{GDBN} with a @code{T02}
41395 It's important for the target to know in which
41396 state the system call was interrupted. There are two possible cases:
41400 The system call hasn't been performed on the host yet.
41403 The system call on the host has been finished.
41407 These two states can be distinguished by the target by the value of the
41408 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
41409 call hasn't been performed. This is equivalent to the @code{EINTR} handling
41410 on POSIX systems. In any other case, the target may presume that the
41411 system call has been finished --- successfully or not --- and should behave
41412 as if the break message arrived right after the system call.
41414 @value{GDBN} must behave reliably. If the system call has not been called
41415 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
41416 @code{errno} in the packet. If the system call on the host has been finished
41417 before the user requests a break, the full action must be finished by
41418 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
41419 The @code{F} packet may only be sent when either nothing has happened
41420 or the full action has been completed.
41423 @subsection Console I/O
41424 @cindex console i/o as part of file-i/o
41426 By default and if not explicitly closed by the target system, the file
41427 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41428 on the @value{GDBN} console is handled as any other file output operation
41429 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41430 by @value{GDBN} so that after the target read request from file descriptor
41431 0 all following typing is buffered until either one of the following
41436 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41438 system call is treated as finished.
41441 The user presses @key{RET}. This is treated as end of input with a trailing
41445 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41446 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41450 If the user has typed more characters than fit in the buffer given to
41451 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41452 either another @code{read(0, @dots{})} is requested by the target, or debugging
41453 is stopped at the user's request.
41456 @node List of Supported Calls
41457 @subsection List of Supported Calls
41458 @cindex list of supported file-i/o calls
41475 @unnumberedsubsubsec open
41476 @cindex open, file-i/o system call
41481 int open(const char *pathname, int flags);
41482 int open(const char *pathname, int flags, mode_t mode);
41486 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41489 @var{flags} is the bitwise @code{OR} of the following values:
41493 If the file does not exist it will be created. The host
41494 rules apply as far as file ownership and time stamps
41498 When used with @code{O_CREAT}, if the file already exists it is
41499 an error and open() fails.
41502 If the file already exists and the open mode allows
41503 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41504 truncated to zero length.
41507 The file is opened in append mode.
41510 The file is opened for reading only.
41513 The file is opened for writing only.
41516 The file is opened for reading and writing.
41520 Other bits are silently ignored.
41524 @var{mode} is the bitwise @code{OR} of the following values:
41528 User has read permission.
41531 User has write permission.
41534 Group has read permission.
41537 Group has write permission.
41540 Others have read permission.
41543 Others have write permission.
41547 Other bits are silently ignored.
41550 @item Return value:
41551 @code{open} returns the new file descriptor or -1 if an error
41558 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41561 @var{pathname} refers to a directory.
41564 The requested access is not allowed.
41567 @var{pathname} was too long.
41570 A directory component in @var{pathname} does not exist.
41573 @var{pathname} refers to a device, pipe, named pipe or socket.
41576 @var{pathname} refers to a file on a read-only filesystem and
41577 write access was requested.
41580 @var{pathname} is an invalid pointer value.
41583 No space on device to create the file.
41586 The process already has the maximum number of files open.
41589 The limit on the total number of files open on the system
41593 The call was interrupted by the user.
41599 @unnumberedsubsubsec close
41600 @cindex close, file-i/o system call
41609 @samp{Fclose,@var{fd}}
41611 @item Return value:
41612 @code{close} returns zero on success, or -1 if an error occurred.
41618 @var{fd} isn't a valid open file descriptor.
41621 The call was interrupted by the user.
41627 @unnumberedsubsubsec read
41628 @cindex read, file-i/o system call
41633 int read(int fd, void *buf, unsigned int count);
41637 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41639 @item Return value:
41640 On success, the number of bytes read is returned.
41641 Zero indicates end of file. If count is zero, read
41642 returns zero as well. On error, -1 is returned.
41648 @var{fd} is not a valid file descriptor or is not open for
41652 @var{bufptr} is an invalid pointer value.
41655 The call was interrupted by the user.
41661 @unnumberedsubsubsec write
41662 @cindex write, file-i/o system call
41667 int write(int fd, const void *buf, unsigned int count);
41671 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41673 @item Return value:
41674 On success, the number of bytes written are returned.
41675 Zero indicates nothing was written. On error, -1
41682 @var{fd} is not a valid file descriptor or is not open for
41686 @var{bufptr} is an invalid pointer value.
41689 An attempt was made to write a file that exceeds the
41690 host-specific maximum file size allowed.
41693 No space on device to write the data.
41696 The call was interrupted by the user.
41702 @unnumberedsubsubsec lseek
41703 @cindex lseek, file-i/o system call
41708 long lseek (int fd, long offset, int flag);
41712 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41714 @var{flag} is one of:
41718 The offset is set to @var{offset} bytes.
41721 The offset is set to its current location plus @var{offset}
41725 The offset is set to the size of the file plus @var{offset}
41729 @item Return value:
41730 On success, the resulting unsigned offset in bytes from
41731 the beginning of the file is returned. Otherwise, a
41732 value of -1 is returned.
41738 @var{fd} is not a valid open file descriptor.
41741 @var{fd} is associated with the @value{GDBN} console.
41744 @var{flag} is not a proper value.
41747 The call was interrupted by the user.
41753 @unnumberedsubsubsec rename
41754 @cindex rename, file-i/o system call
41759 int rename(const char *oldpath, const char *newpath);
41763 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41765 @item Return value:
41766 On success, zero is returned. On error, -1 is returned.
41772 @var{newpath} is an existing directory, but @var{oldpath} is not a
41776 @var{newpath} is a non-empty directory.
41779 @var{oldpath} or @var{newpath} is a directory that is in use by some
41783 An attempt was made to make a directory a subdirectory
41787 A component used as a directory in @var{oldpath} or new
41788 path is not a directory. Or @var{oldpath} is a directory
41789 and @var{newpath} exists but is not a directory.
41792 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41795 No access to the file or the path of the file.
41799 @var{oldpath} or @var{newpath} was too long.
41802 A directory component in @var{oldpath} or @var{newpath} does not exist.
41805 The file is on a read-only filesystem.
41808 The device containing the file has no room for the new
41812 The call was interrupted by the user.
41818 @unnumberedsubsubsec unlink
41819 @cindex unlink, file-i/o system call
41824 int unlink(const char *pathname);
41828 @samp{Funlink,@var{pathnameptr}/@var{len}}
41830 @item Return value:
41831 On success, zero is returned. On error, -1 is returned.
41837 No access to the file or the path of the file.
41840 The system does not allow unlinking of directories.
41843 The file @var{pathname} cannot be unlinked because it's
41844 being used by another process.
41847 @var{pathnameptr} is an invalid pointer value.
41850 @var{pathname} was too long.
41853 A directory component in @var{pathname} does not exist.
41856 A component of the path is not a directory.
41859 The file is on a read-only filesystem.
41862 The call was interrupted by the user.
41868 @unnumberedsubsubsec stat/fstat
41869 @cindex fstat, file-i/o system call
41870 @cindex stat, file-i/o system call
41875 int stat(const char *pathname, struct stat *buf);
41876 int fstat(int fd, struct stat *buf);
41880 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41881 @samp{Ffstat,@var{fd},@var{bufptr}}
41883 @item Return value:
41884 On success, zero is returned. On error, -1 is returned.
41890 @var{fd} is not a valid open file.
41893 A directory component in @var{pathname} does not exist or the
41894 path is an empty string.
41897 A component of the path is not a directory.
41900 @var{pathnameptr} is an invalid pointer value.
41903 No access to the file or the path of the file.
41906 @var{pathname} was too long.
41909 The call was interrupted by the user.
41915 @unnumberedsubsubsec gettimeofday
41916 @cindex gettimeofday, file-i/o system call
41921 int gettimeofday(struct timeval *tv, void *tz);
41925 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41927 @item Return value:
41928 On success, 0 is returned, -1 otherwise.
41934 @var{tz} is a non-NULL pointer.
41937 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41943 @unnumberedsubsubsec isatty
41944 @cindex isatty, file-i/o system call
41949 int isatty(int fd);
41953 @samp{Fisatty,@var{fd}}
41955 @item Return value:
41956 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
41962 The call was interrupted by the user.
41967 Note that the @code{isatty} call is treated as a special case: it returns
41968 1 to the target if the file descriptor is attached
41969 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
41970 would require implementing @code{ioctl} and would be more complex than
41975 @unnumberedsubsubsec system
41976 @cindex system, file-i/o system call
41981 int system(const char *command);
41985 @samp{Fsystem,@var{commandptr}/@var{len}}
41987 @item Return value:
41988 If @var{len} is zero, the return value indicates whether a shell is
41989 available. A zero return value indicates a shell is not available.
41990 For non-zero @var{len}, the value returned is -1 on error and the
41991 return status of the command otherwise. Only the exit status of the
41992 command is returned, which is extracted from the host's @code{system}
41993 return value by calling @code{WEXITSTATUS(retval)}. In case
41994 @file{/bin/sh} could not be executed, 127 is returned.
42000 The call was interrupted by the user.
42005 @value{GDBN} takes over the full task of calling the necessary host calls
42006 to perform the @code{system} call. The return value of @code{system} on
42007 the host is simplified before it's returned
42008 to the target. Any termination signal information from the child process
42009 is discarded, and the return value consists
42010 entirely of the exit status of the called command.
42012 Due to security concerns, the @code{system} call is by default refused
42013 by @value{GDBN}. The user has to allow this call explicitly with the
42014 @code{set remote system-call-allowed 1} command.
42017 @item set remote system-call-allowed
42018 @kindex set remote system-call-allowed
42019 Control whether to allow the @code{system} calls in the File I/O
42020 protocol for the remote target. The default is zero (disabled).
42022 @item show remote system-call-allowed
42023 @kindex show remote system-call-allowed
42024 Show whether the @code{system} calls are allowed in the File I/O
42028 @node Protocol-specific Representation of Datatypes
42029 @subsection Protocol-specific Representation of Datatypes
42030 @cindex protocol-specific representation of datatypes, in file-i/o protocol
42033 * Integral Datatypes::
42035 * Memory Transfer::
42040 @node Integral Datatypes
42041 @unnumberedsubsubsec Integral Datatypes
42042 @cindex integral datatypes, in file-i/o protocol
42044 The integral datatypes used in the system calls are @code{int},
42045 @code{unsigned int}, @code{long}, @code{unsigned long},
42046 @code{mode_t}, and @code{time_t}.
42048 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
42049 implemented as 32 bit values in this protocol.
42051 @code{long} and @code{unsigned long} are implemented as 64 bit types.
42053 @xref{Limits}, for corresponding MIN and MAX values (similar to those
42054 in @file{limits.h}) to allow range checking on host and target.
42056 @code{time_t} datatypes are defined as seconds since the Epoch.
42058 All integral datatypes transferred as part of a memory read or write of a
42059 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
42062 @node Pointer Values
42063 @unnumberedsubsubsec Pointer Values
42064 @cindex pointer values, in file-i/o protocol
42066 Pointers to target data are transmitted as they are. An exception
42067 is made for pointers to buffers for which the length isn't
42068 transmitted as part of the function call, namely strings. Strings
42069 are transmitted as a pointer/length pair, both as hex values, e.g.@:
42076 which is a pointer to data of length 18 bytes at position 0x1aaf.
42077 The length is defined as the full string length in bytes, including
42078 the trailing null byte. For example, the string @code{"hello world"}
42079 at address 0x123456 is transmitted as
42085 @node Memory Transfer
42086 @unnumberedsubsubsec Memory Transfer
42087 @cindex memory transfer, in file-i/o protocol
42089 Structured data which is transferred using a memory read or write (for
42090 example, a @code{struct stat}) is expected to be in a protocol-specific format
42091 with all scalar multibyte datatypes being big endian. Translation to
42092 this representation needs to be done both by the target before the @code{F}
42093 packet is sent, and by @value{GDBN} before
42094 it transfers memory to the target. Transferred pointers to structured
42095 data should point to the already-coerced data at any time.
42099 @unnumberedsubsubsec struct stat
42100 @cindex struct stat, in file-i/o protocol
42102 The buffer of type @code{struct stat} used by the target and @value{GDBN}
42103 is defined as follows:
42107 unsigned int st_dev; /* device */
42108 unsigned int st_ino; /* inode */
42109 mode_t st_mode; /* protection */
42110 unsigned int st_nlink; /* number of hard links */
42111 unsigned int st_uid; /* user ID of owner */
42112 unsigned int st_gid; /* group ID of owner */
42113 unsigned int st_rdev; /* device type (if inode device) */
42114 unsigned long st_size; /* total size, in bytes */
42115 unsigned long st_blksize; /* blocksize for filesystem I/O */
42116 unsigned long st_blocks; /* number of blocks allocated */
42117 time_t st_atime; /* time of last access */
42118 time_t st_mtime; /* time of last modification */
42119 time_t st_ctime; /* time of last change */
42123 The integral datatypes conform to the definitions given in the
42124 appropriate section (see @ref{Integral Datatypes}, for details) so this
42125 structure is of size 64 bytes.
42127 The values of several fields have a restricted meaning and/or
42133 A value of 0 represents a file, 1 the console.
42136 No valid meaning for the target. Transmitted unchanged.
42139 Valid mode bits are described in @ref{Constants}. Any other
42140 bits have currently no meaning for the target.
42145 No valid meaning for the target. Transmitted unchanged.
42150 These values have a host and file system dependent
42151 accuracy. Especially on Windows hosts, the file system may not
42152 support exact timing values.
42155 The target gets a @code{struct stat} of the above representation and is
42156 responsible for coercing it to the target representation before
42159 Note that due to size differences between the host, target, and protocol
42160 representations of @code{struct stat} members, these members could eventually
42161 get truncated on the target.
42163 @node struct timeval
42164 @unnumberedsubsubsec struct timeval
42165 @cindex struct timeval, in file-i/o protocol
42167 The buffer of type @code{struct timeval} used by the File-I/O protocol
42168 is defined as follows:
42172 time_t tv_sec; /* second */
42173 long tv_usec; /* microsecond */
42177 The integral datatypes conform to the definitions given in the
42178 appropriate section (see @ref{Integral Datatypes}, for details) so this
42179 structure is of size 8 bytes.
42182 @subsection Constants
42183 @cindex constants, in file-i/o protocol
42185 The following values are used for the constants inside of the
42186 protocol. @value{GDBN} and target are responsible for translating these
42187 values before and after the call as needed.
42198 @unnumberedsubsubsec Open Flags
42199 @cindex open flags, in file-i/o protocol
42201 All values are given in hexadecimal representation.
42213 @node mode_t Values
42214 @unnumberedsubsubsec mode_t Values
42215 @cindex mode_t values, in file-i/o protocol
42217 All values are given in octal representation.
42234 @unnumberedsubsubsec Errno Values
42235 @cindex errno values, in file-i/o protocol
42237 All values are given in decimal representation.
42262 @code{EUNKNOWN} is used as a fallback error value if a host system returns
42263 any error value not in the list of supported error numbers.
42266 @unnumberedsubsubsec Lseek Flags
42267 @cindex lseek flags, in file-i/o protocol
42276 @unnumberedsubsubsec Limits
42277 @cindex limits, in file-i/o protocol
42279 All values are given in decimal representation.
42282 INT_MIN -2147483648
42284 UINT_MAX 4294967295
42285 LONG_MIN -9223372036854775808
42286 LONG_MAX 9223372036854775807
42287 ULONG_MAX 18446744073709551615
42290 @node File-I/O Examples
42291 @subsection File-I/O Examples
42292 @cindex file-i/o examples
42294 Example sequence of a write call, file descriptor 3, buffer is at target
42295 address 0x1234, 6 bytes should be written:
42298 <- @code{Fwrite,3,1234,6}
42299 @emph{request memory read from target}
42302 @emph{return "6 bytes written"}
42306 Example sequence of a read call, file descriptor 3, buffer is at target
42307 address 0x1234, 6 bytes should be read:
42310 <- @code{Fread,3,1234,6}
42311 @emph{request memory write to target}
42312 -> @code{X1234,6:XXXXXX}
42313 @emph{return "6 bytes read"}
42317 Example sequence of a read call, call fails on the host due to invalid
42318 file descriptor (@code{EBADF}):
42321 <- @code{Fread,3,1234,6}
42325 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
42329 <- @code{Fread,3,1234,6}
42334 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
42338 <- @code{Fread,3,1234,6}
42339 -> @code{X1234,6:XXXXXX}
42343 @node Library List Format
42344 @section Library List Format
42345 @cindex library list format, remote protocol
42347 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
42348 same process as your application to manage libraries. In this case,
42349 @value{GDBN} can use the loader's symbol table and normal memory
42350 operations to maintain a list of shared libraries. On other
42351 platforms, the operating system manages loaded libraries.
42352 @value{GDBN} can not retrieve the list of currently loaded libraries
42353 through memory operations, so it uses the @samp{qXfer:libraries:read}
42354 packet (@pxref{qXfer library list read}) instead. The remote stub
42355 queries the target's operating system and reports which libraries
42358 The @samp{qXfer:libraries:read} packet returns an XML document which
42359 lists loaded libraries and their offsets. Each library has an
42360 associated name and one or more segment or section base addresses,
42361 which report where the library was loaded in memory.
42363 For the common case of libraries that are fully linked binaries, the
42364 library should have a list of segments. If the target supports
42365 dynamic linking of a relocatable object file, its library XML element
42366 should instead include a list of allocated sections. The segment or
42367 section bases are start addresses, not relocation offsets; they do not
42368 depend on the library's link-time base addresses.
42370 @value{GDBN} must be linked with the Expat library to support XML
42371 library lists. @xref{Expat}.
42373 A simple memory map, with one loaded library relocated by a single
42374 offset, looks like this:
42378 <library name="/lib/libc.so.6">
42379 <segment address="0x10000000"/>
42384 Another simple memory map, with one loaded library with three
42385 allocated sections (.text, .data, .bss), looks like this:
42389 <library name="sharedlib.o">
42390 <section address="0x10000000"/>
42391 <section address="0x20000000"/>
42392 <section address="0x30000000"/>
42397 The format of a library list is described by this DTD:
42400 <!-- library-list: Root element with versioning -->
42401 <!ELEMENT library-list (library)*>
42402 <!ATTLIST library-list version CDATA #FIXED "1.0">
42403 <!ELEMENT library (segment*, section*)>
42404 <!ATTLIST library name CDATA #REQUIRED>
42405 <!ELEMENT segment EMPTY>
42406 <!ATTLIST segment address CDATA #REQUIRED>
42407 <!ELEMENT section EMPTY>
42408 <!ATTLIST section address CDATA #REQUIRED>
42411 In addition, segments and section descriptors cannot be mixed within a
42412 single library element, and you must supply at least one segment or
42413 section for each library.
42415 @node Library List Format for SVR4 Targets
42416 @section Library List Format for SVR4 Targets
42417 @cindex library list format, remote protocol
42419 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
42420 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42421 shared libraries. Still a special library list provided by this packet is
42422 more efficient for the @value{GDBN} remote protocol.
42424 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42425 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42426 target, the following parameters are reported:
42430 @code{name}, the absolute file name from the @code{l_name} field of
42431 @code{struct link_map}.
42433 @code{lm} with address of @code{struct link_map} used for TLS
42434 (Thread Local Storage) access.
42436 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42437 @code{struct link_map}. For prelinked libraries this is not an absolute
42438 memory address. It is a displacement of absolute memory address against
42439 address the file was prelinked to during the library load.
42441 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42444 Additionally the single @code{main-lm} attribute specifies address of
42445 @code{struct link_map} used for the main executable. This parameter is used
42446 for TLS access and its presence is optional.
42448 @value{GDBN} must be linked with the Expat library to support XML
42449 SVR4 library lists. @xref{Expat}.
42451 A simple memory map, with two loaded libraries (which do not use prelink),
42455 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42456 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42458 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42460 </library-list-svr>
42463 The format of an SVR4 library list is described by this DTD:
42466 <!-- library-list-svr4: Root element with versioning -->
42467 <!ELEMENT library-list-svr4 (library)*>
42468 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42469 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42470 <!ELEMENT library EMPTY>
42471 <!ATTLIST library name CDATA #REQUIRED>
42472 <!ATTLIST library lm CDATA #REQUIRED>
42473 <!ATTLIST library l_addr CDATA #REQUIRED>
42474 <!ATTLIST library l_ld CDATA #REQUIRED>
42477 @node Memory Map Format
42478 @section Memory Map Format
42479 @cindex memory map format
42481 To be able to write into flash memory, @value{GDBN} needs to obtain a
42482 memory map from the target. This section describes the format of the
42485 The memory map is obtained using the @samp{qXfer:memory-map:read}
42486 (@pxref{qXfer memory map read}) packet and is an XML document that
42487 lists memory regions.
42489 @value{GDBN} must be linked with the Expat library to support XML
42490 memory maps. @xref{Expat}.
42492 The top-level structure of the document is shown below:
42495 <?xml version="1.0"?>
42496 <!DOCTYPE memory-map
42497 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42498 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42504 Each region can be either:
42509 A region of RAM starting at @var{addr} and extending for @var{length}
42513 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42518 A region of read-only memory:
42521 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42526 A region of flash memory, with erasure blocks @var{blocksize}
42530 <memory type="flash" start="@var{addr}" length="@var{length}">
42531 <property name="blocksize">@var{blocksize}</property>
42537 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42538 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42539 packets to write to addresses in such ranges.
42541 The formal DTD for memory map format is given below:
42544 <!-- ................................................... -->
42545 <!-- Memory Map XML DTD ................................ -->
42546 <!-- File: memory-map.dtd .............................. -->
42547 <!-- .................................... .............. -->
42548 <!-- memory-map.dtd -->
42549 <!-- memory-map: Root element with versioning -->
42550 <!ELEMENT memory-map (memory | property)>
42551 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42552 <!ELEMENT memory (property)>
42553 <!-- memory: Specifies a memory region,
42554 and its type, or device. -->
42555 <!ATTLIST memory type CDATA #REQUIRED
42556 start CDATA #REQUIRED
42557 length CDATA #REQUIRED
42558 device CDATA #IMPLIED>
42559 <!-- property: Generic attribute tag -->
42560 <!ELEMENT property (#PCDATA | property)*>
42561 <!ATTLIST property name CDATA #REQUIRED>
42564 @node Thread List Format
42565 @section Thread List Format
42566 @cindex thread list format
42568 To efficiently update the list of threads and their attributes,
42569 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42570 (@pxref{qXfer threads read}) and obtains the XML document with
42571 the following structure:
42574 <?xml version="1.0"?>
42576 <thread id="id" core="0">
42577 ... description ...
42582 Each @samp{thread} element must have the @samp{id} attribute that
42583 identifies the thread (@pxref{thread-id syntax}). The
42584 @samp{core} attribute, if present, specifies which processor core
42585 the thread was last executing on. The content of the of @samp{thread}
42586 element is interpreted as human-readable auxilliary information.
42588 @node Traceframe Info Format
42589 @section Traceframe Info Format
42590 @cindex traceframe info format
42592 To be able to know which objects in the inferior can be examined when
42593 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42594 memory ranges, registers and trace state variables that have been
42595 collected in a traceframe.
42597 This list is obtained using the @samp{qXfer:traceframe-info:read}
42598 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42600 @value{GDBN} must be linked with the Expat library to support XML
42601 traceframe info discovery. @xref{Expat}.
42603 The top-level structure of the document is shown below:
42606 <?xml version="1.0"?>
42607 <!DOCTYPE traceframe-info
42608 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42609 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42615 Each traceframe block can be either:
42620 A region of collected memory starting at @var{addr} and extending for
42621 @var{length} bytes from there:
42624 <memory start="@var{addr}" length="@var{length}"/>
42628 A block indicating trace state variable numbered @var{number} has been
42632 <tvar id="@var{number}"/>
42637 The formal DTD for the traceframe info format is given below:
42640 <!ELEMENT traceframe-info (memory | tvar)* >
42641 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42643 <!ELEMENT memory EMPTY>
42644 <!ATTLIST memory start CDATA #REQUIRED
42645 length CDATA #REQUIRED>
42647 <!ATTLIST tvar id CDATA #REQUIRED>
42650 @node Branch Trace Format
42651 @section Branch Trace Format
42652 @cindex branch trace format
42654 In order to display the branch trace of an inferior thread,
42655 @value{GDBN} needs to obtain the list of branches. This list is
42656 represented as list of sequential code blocks that are connected via
42657 branches. The code in each block has been executed sequentially.
42659 This list is obtained using the @samp{qXfer:btrace:read}
42660 (@pxref{qXfer btrace read}) packet and is an XML document.
42662 @value{GDBN} must be linked with the Expat library to support XML
42663 traceframe info discovery. @xref{Expat}.
42665 The top-level structure of the document is shown below:
42668 <?xml version="1.0"?>
42670 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42671 "http://sourceware.org/gdb/gdb-btrace.dtd">
42680 A block of sequentially executed instructions starting at @var{begin}
42681 and ending at @var{end}:
42684 <block begin="@var{begin}" end="@var{end}"/>
42689 The formal DTD for the branch trace format is given below:
42692 <!ELEMENT btrace (block)* >
42693 <!ATTLIST btrace version CDATA #FIXED "1.0">
42695 <!ELEMENT block EMPTY>
42696 <!ATTLIST block begin CDATA #REQUIRED
42697 end CDATA #REQUIRED>
42700 @include agentexpr.texi
42702 @node Target Descriptions
42703 @appendix Target Descriptions
42704 @cindex target descriptions
42706 One of the challenges of using @value{GDBN} to debug embedded systems
42707 is that there are so many minor variants of each processor
42708 architecture in use. It is common practice for vendors to start with
42709 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42710 and then make changes to adapt it to a particular market niche. Some
42711 architectures have hundreds of variants, available from dozens of
42712 vendors. This leads to a number of problems:
42716 With so many different customized processors, it is difficult for
42717 the @value{GDBN} maintainers to keep up with the changes.
42719 Since individual variants may have short lifetimes or limited
42720 audiences, it may not be worthwhile to carry information about every
42721 variant in the @value{GDBN} source tree.
42723 When @value{GDBN} does support the architecture of the embedded system
42724 at hand, the task of finding the correct architecture name to give the
42725 @command{set architecture} command can be error-prone.
42728 To address these problems, the @value{GDBN} remote protocol allows a
42729 target system to not only identify itself to @value{GDBN}, but to
42730 actually describe its own features. This lets @value{GDBN} support
42731 processor variants it has never seen before --- to the extent that the
42732 descriptions are accurate, and that @value{GDBN} understands them.
42734 @value{GDBN} must be linked with the Expat library to support XML
42735 target descriptions. @xref{Expat}.
42738 * Retrieving Descriptions:: How descriptions are fetched from a target.
42739 * Target Description Format:: The contents of a target description.
42740 * Predefined Target Types:: Standard types available for target
42742 * Standard Target Features:: Features @value{GDBN} knows about.
42745 @node Retrieving Descriptions
42746 @section Retrieving Descriptions
42748 Target descriptions can be read from the target automatically, or
42749 specified by the user manually. The default behavior is to read the
42750 description from the target. @value{GDBN} retrieves it via the remote
42751 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42752 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42753 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42754 XML document, of the form described in @ref{Target Description
42757 Alternatively, you can specify a file to read for the target description.
42758 If a file is set, the target will not be queried. The commands to
42759 specify a file are:
42762 @cindex set tdesc filename
42763 @item set tdesc filename @var{path}
42764 Read the target description from @var{path}.
42766 @cindex unset tdesc filename
42767 @item unset tdesc filename
42768 Do not read the XML target description from a file. @value{GDBN}
42769 will use the description supplied by the current target.
42771 @cindex show tdesc filename
42772 @item show tdesc filename
42773 Show the filename to read for a target description, if any.
42777 @node Target Description Format
42778 @section Target Description Format
42779 @cindex target descriptions, XML format
42781 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42782 document which complies with the Document Type Definition provided in
42783 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42784 means you can use generally available tools like @command{xmllint} to
42785 check that your feature descriptions are well-formed and valid.
42786 However, to help people unfamiliar with XML write descriptions for
42787 their targets, we also describe the grammar here.
42789 Target descriptions can identify the architecture of the remote target
42790 and (for some architectures) provide information about custom register
42791 sets. They can also identify the OS ABI of the remote target.
42792 @value{GDBN} can use this information to autoconfigure for your
42793 target, or to warn you if you connect to an unsupported target.
42795 Here is a simple target description:
42798 <target version="1.0">
42799 <architecture>i386:x86-64</architecture>
42804 This minimal description only says that the target uses
42805 the x86-64 architecture.
42807 A target description has the following overall form, with [ ] marking
42808 optional elements and @dots{} marking repeatable elements. The elements
42809 are explained further below.
42812 <?xml version="1.0"?>
42813 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42814 <target version="1.0">
42815 @r{[}@var{architecture}@r{]}
42816 @r{[}@var{osabi}@r{]}
42817 @r{[}@var{compatible}@r{]}
42818 @r{[}@var{feature}@dots{}@r{]}
42823 The description is generally insensitive to whitespace and line
42824 breaks, under the usual common-sense rules. The XML version
42825 declaration and document type declaration can generally be omitted
42826 (@value{GDBN} does not require them), but specifying them may be
42827 useful for XML validation tools. The @samp{version} attribute for
42828 @samp{<target>} may also be omitted, but we recommend
42829 including it; if future versions of @value{GDBN} use an incompatible
42830 revision of @file{gdb-target.dtd}, they will detect and report
42831 the version mismatch.
42833 @subsection Inclusion
42834 @cindex target descriptions, inclusion
42837 @cindex <xi:include>
42840 It can sometimes be valuable to split a target description up into
42841 several different annexes, either for organizational purposes, or to
42842 share files between different possible target descriptions. You can
42843 divide a description into multiple files by replacing any element of
42844 the target description with an inclusion directive of the form:
42847 <xi:include href="@var{document}"/>
42851 When @value{GDBN} encounters an element of this form, it will retrieve
42852 the named XML @var{document}, and replace the inclusion directive with
42853 the contents of that document. If the current description was read
42854 using @samp{qXfer}, then so will be the included document;
42855 @var{document} will be interpreted as the name of an annex. If the
42856 current description was read from a file, @value{GDBN} will look for
42857 @var{document} as a file in the same directory where it found the
42858 original description.
42860 @subsection Architecture
42861 @cindex <architecture>
42863 An @samp{<architecture>} element has this form:
42866 <architecture>@var{arch}</architecture>
42869 @var{arch} is one of the architectures from the set accepted by
42870 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42873 @cindex @code{<osabi>}
42875 This optional field was introduced in @value{GDBN} version 7.0.
42876 Previous versions of @value{GDBN} ignore it.
42878 An @samp{<osabi>} element has this form:
42881 <osabi>@var{abi-name}</osabi>
42884 @var{abi-name} is an OS ABI name from the same selection accepted by
42885 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42887 @subsection Compatible Architecture
42888 @cindex @code{<compatible>}
42890 This optional field was introduced in @value{GDBN} version 7.0.
42891 Previous versions of @value{GDBN} ignore it.
42893 A @samp{<compatible>} element has this form:
42896 <compatible>@var{arch}</compatible>
42899 @var{arch} is one of the architectures from the set accepted by
42900 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42902 A @samp{<compatible>} element is used to specify that the target
42903 is able to run binaries in some other than the main target architecture
42904 given by the @samp{<architecture>} element. For example, on the
42905 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42906 or @code{powerpc:common64}, but the system is able to run binaries
42907 in the @code{spu} architecture as well. The way to describe this
42908 capability with @samp{<compatible>} is as follows:
42911 <architecture>powerpc:common</architecture>
42912 <compatible>spu</compatible>
42915 @subsection Features
42918 Each @samp{<feature>} describes some logical portion of the target
42919 system. Features are currently used to describe available CPU
42920 registers and the types of their contents. A @samp{<feature>} element
42924 <feature name="@var{name}">
42925 @r{[}@var{type}@dots{}@r{]}
42931 Each feature's name should be unique within the description. The name
42932 of a feature does not matter unless @value{GDBN} has some special
42933 knowledge of the contents of that feature; if it does, the feature
42934 should have its standard name. @xref{Standard Target Features}.
42938 Any register's value is a collection of bits which @value{GDBN} must
42939 interpret. The default interpretation is a two's complement integer,
42940 but other types can be requested by name in the register description.
42941 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
42942 Target Types}), and the description can define additional composite types.
42944 Each type element must have an @samp{id} attribute, which gives
42945 a unique (within the containing @samp{<feature>}) name to the type.
42946 Types must be defined before they are used.
42949 Some targets offer vector registers, which can be treated as arrays
42950 of scalar elements. These types are written as @samp{<vector>} elements,
42951 specifying the array element type, @var{type}, and the number of elements,
42955 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
42959 If a register's value is usefully viewed in multiple ways, define it
42960 with a union type containing the useful representations. The
42961 @samp{<union>} element contains one or more @samp{<field>} elements,
42962 each of which has a @var{name} and a @var{type}:
42965 <union id="@var{id}">
42966 <field name="@var{name}" type="@var{type}"/>
42972 If a register's value is composed from several separate values, define
42973 it with a structure type. There are two forms of the @samp{<struct>}
42974 element; a @samp{<struct>} element must either contain only bitfields
42975 or contain no bitfields. If the structure contains only bitfields,
42976 its total size in bytes must be specified, each bitfield must have an
42977 explicit start and end, and bitfields are automatically assigned an
42978 integer type. The field's @var{start} should be less than or
42979 equal to its @var{end}, and zero represents the least significant bit.
42982 <struct id="@var{id}" size="@var{size}">
42983 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
42988 If the structure contains no bitfields, then each field has an
42989 explicit type, and no implicit padding is added.
42992 <struct id="@var{id}">
42993 <field name="@var{name}" type="@var{type}"/>
42999 If a register's value is a series of single-bit flags, define it with
43000 a flags type. The @samp{<flags>} element has an explicit @var{size}
43001 and contains one or more @samp{<field>} elements. Each field has a
43002 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
43006 <flags id="@var{id}" size="@var{size}">
43007 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
43012 @subsection Registers
43015 Each register is represented as an element with this form:
43018 <reg name="@var{name}"
43019 bitsize="@var{size}"
43020 @r{[}regnum="@var{num}"@r{]}
43021 @r{[}save-restore="@var{save-restore}"@r{]}
43022 @r{[}type="@var{type}"@r{]}
43023 @r{[}group="@var{group}"@r{]}/>
43027 The components are as follows:
43032 The register's name; it must be unique within the target description.
43035 The register's size, in bits.
43038 The register's number. If omitted, a register's number is one greater
43039 than that of the previous register (either in the current feature or in
43040 a preceding feature); the first register in the target description
43041 defaults to zero. This register number is used to read or write
43042 the register; e.g.@: it is used in the remote @code{p} and @code{P}
43043 packets, and registers appear in the @code{g} and @code{G} packets
43044 in order of increasing register number.
43047 Whether the register should be preserved across inferior function
43048 calls; this must be either @code{yes} or @code{no}. The default is
43049 @code{yes}, which is appropriate for most registers except for
43050 some system control registers; this is not related to the target's
43054 The type of the register. @var{type} may be a predefined type, a type
43055 defined in the current feature, or one of the special types @code{int}
43056 and @code{float}. @code{int} is an integer type of the correct size
43057 for @var{bitsize}, and @code{float} is a floating point type (in the
43058 architecture's normal floating point format) of the correct size for
43059 @var{bitsize}. The default is @code{int}.
43062 The register group to which this register belongs. @var{group} must
43063 be either @code{general}, @code{float}, or @code{vector}. If no
43064 @var{group} is specified, @value{GDBN} will not display the register
43065 in @code{info registers}.
43069 @node Predefined Target Types
43070 @section Predefined Target Types
43071 @cindex target descriptions, predefined types
43073 Type definitions in the self-description can build up composite types
43074 from basic building blocks, but can not define fundamental types. Instead,
43075 standard identifiers are provided by @value{GDBN} for the fundamental
43076 types. The currently supported types are:
43085 Signed integer types holding the specified number of bits.
43092 Unsigned integer types holding the specified number of bits.
43096 Pointers to unspecified code and data. The program counter and
43097 any dedicated return address register may be marked as code
43098 pointers; printing a code pointer converts it into a symbolic
43099 address. The stack pointer and any dedicated address registers
43100 may be marked as data pointers.
43103 Single precision IEEE floating point.
43106 Double precision IEEE floating point.
43109 The 12-byte extended precision format used by ARM FPA registers.
43112 The 10-byte extended precision format used by x87 registers.
43115 32bit @sc{eflags} register used by x86.
43118 32bit @sc{mxcsr} register used by x86.
43122 @node Standard Target Features
43123 @section Standard Target Features
43124 @cindex target descriptions, standard features
43126 A target description must contain either no registers or all the
43127 target's registers. If the description contains no registers, then
43128 @value{GDBN} will assume a default register layout, selected based on
43129 the architecture. If the description contains any registers, the
43130 default layout will not be used; the standard registers must be
43131 described in the target description, in such a way that @value{GDBN}
43132 can recognize them.
43134 This is accomplished by giving specific names to feature elements
43135 which contain standard registers. @value{GDBN} will look for features
43136 with those names and verify that they contain the expected registers;
43137 if any known feature is missing required registers, or if any required
43138 feature is missing, @value{GDBN} will reject the target
43139 description. You can add additional registers to any of the
43140 standard features --- @value{GDBN} will display them just as if
43141 they were added to an unrecognized feature.
43143 This section lists the known features and their expected contents.
43144 Sample XML documents for these features are included in the
43145 @value{GDBN} source tree, in the directory @file{gdb/features}.
43147 Names recognized by @value{GDBN} should include the name of the
43148 company or organization which selected the name, and the overall
43149 architecture to which the feature applies; so e.g.@: the feature
43150 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
43152 The names of registers are not case sensitive for the purpose
43153 of recognizing standard features, but @value{GDBN} will only display
43154 registers using the capitalization used in the description.
43157 * AArch64 Features::
43162 * Nios II Features::
43163 * PowerPC Features::
43164 * S/390 and System z Features::
43169 @node AArch64 Features
43170 @subsection AArch64 Features
43171 @cindex target descriptions, AArch64 features
43173 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
43174 targets. It should contain registers @samp{x0} through @samp{x30},
43175 @samp{sp}, @samp{pc}, and @samp{cpsr}.
43177 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
43178 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
43182 @subsection ARM Features
43183 @cindex target descriptions, ARM features
43185 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
43187 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
43188 @samp{lr}, @samp{pc}, and @samp{cpsr}.
43190 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
43191 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
43192 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
43195 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
43196 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
43198 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
43199 it should contain at least registers @samp{wR0} through @samp{wR15} and
43200 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
43201 @samp{wCSSF}, and @samp{wCASF} registers are optional.
43203 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
43204 should contain at least registers @samp{d0} through @samp{d15}. If
43205 they are present, @samp{d16} through @samp{d31} should also be included.
43206 @value{GDBN} will synthesize the single-precision registers from
43207 halves of the double-precision registers.
43209 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
43210 need to contain registers; it instructs @value{GDBN} to display the
43211 VFP double-precision registers as vectors and to synthesize the
43212 quad-precision registers from pairs of double-precision registers.
43213 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
43214 be present and include 32 double-precision registers.
43216 @node i386 Features
43217 @subsection i386 Features
43218 @cindex target descriptions, i386 features
43220 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
43221 targets. It should describe the following registers:
43225 @samp{eax} through @samp{edi} plus @samp{eip} for i386
43227 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
43229 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
43230 @samp{fs}, @samp{gs}
43232 @samp{st0} through @samp{st7}
43234 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
43235 @samp{foseg}, @samp{fooff} and @samp{fop}
43238 The register sets may be different, depending on the target.
43240 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
43241 describe registers:
43245 @samp{xmm0} through @samp{xmm7} for i386
43247 @samp{xmm0} through @samp{xmm15} for amd64
43252 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
43253 @samp{org.gnu.gdb.i386.sse} feature. It should
43254 describe the upper 128 bits of @sc{ymm} registers:
43258 @samp{ymm0h} through @samp{ymm7h} for i386
43260 @samp{ymm0h} through @samp{ymm15h} for amd64
43263 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
43264 Memory Protection Extension (MPX). It should describe the following registers:
43268 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
43270 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
43273 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
43274 describe a single register, @samp{orig_eax}.
43276 @node MIPS Features
43277 @subsection @acronym{MIPS} Features
43278 @cindex target descriptions, @acronym{MIPS} features
43280 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
43281 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
43282 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
43285 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
43286 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
43287 registers. They may be 32-bit or 64-bit depending on the target.
43289 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
43290 it may be optional in a future version of @value{GDBN}. It should
43291 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
43292 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
43294 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
43295 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
43296 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
43297 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
43299 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
43300 contain a single register, @samp{restart}, which is used by the
43301 Linux kernel to control restartable syscalls.
43303 @node M68K Features
43304 @subsection M68K Features
43305 @cindex target descriptions, M68K features
43308 @item @samp{org.gnu.gdb.m68k.core}
43309 @itemx @samp{org.gnu.gdb.coldfire.core}
43310 @itemx @samp{org.gnu.gdb.fido.core}
43311 One of those features must be always present.
43312 The feature that is present determines which flavor of m68k is
43313 used. The feature that is present should contain registers
43314 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
43315 @samp{sp}, @samp{ps} and @samp{pc}.
43317 @item @samp{org.gnu.gdb.coldfire.fp}
43318 This feature is optional. If present, it should contain registers
43319 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
43323 @node Nios II Features
43324 @subsection Nios II Features
43325 @cindex target descriptions, Nios II features
43327 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
43328 targets. It should contain the 32 core registers (@samp{zero},
43329 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
43330 @samp{pc}, and the 16 control registers (@samp{status} through
43333 @node PowerPC Features
43334 @subsection PowerPC Features
43335 @cindex target descriptions, PowerPC features
43337 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
43338 targets. It should contain registers @samp{r0} through @samp{r31},
43339 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
43340 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
43342 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
43343 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
43345 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
43346 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
43349 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
43350 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
43351 will combine these registers with the floating point registers
43352 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
43353 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
43354 through @samp{vs63}, the set of vector registers for POWER7.
43356 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
43357 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
43358 @samp{spefscr}. SPE targets should provide 32-bit registers in
43359 @samp{org.gnu.gdb.power.core} and provide the upper halves in
43360 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
43361 these to present registers @samp{ev0} through @samp{ev31} to the
43364 @node S/390 and System z Features
43365 @subsection S/390 and System z Features
43366 @cindex target descriptions, S/390 features
43367 @cindex target descriptions, System z features
43369 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
43370 System z targets. It should contain the PSW and the 16 general
43371 registers. In particular, System z targets should provide the 64-bit
43372 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
43373 S/390 targets should provide the 32-bit versions of these registers.
43374 A System z target that runs in 31-bit addressing mode should provide
43375 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
43376 register's upper halves @samp{r0h} through @samp{r15h}, and their
43377 lower halves @samp{r0l} through @samp{r15l}.
43379 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
43380 contain the 64-bit registers @samp{f0} through @samp{f15}, and
43383 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
43384 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
43386 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
43387 contain the register @samp{orig_r2}, which is 64-bit wide on System z
43388 targets and 32-bit otherwise. In addition, the feature may contain
43389 the @samp{last_break} register, whose width depends on the addressing
43390 mode, as well as the @samp{system_call} register, which is always
43393 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
43394 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
43395 @samp{atia}, and @samp{tr0} through @samp{tr15}.
43397 @node TIC6x Features
43398 @subsection TMS320C6x Features
43399 @cindex target descriptions, TIC6x features
43400 @cindex target descriptions, TMS320C6x features
43401 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
43402 targets. It should contain registers @samp{A0} through @samp{A15},
43403 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
43405 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
43406 contain registers @samp{A16} through @samp{A31} and @samp{B16}
43407 through @samp{B31}.
43409 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
43410 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
43412 @node Operating System Information
43413 @appendix Operating System Information
43414 @cindex operating system information
43420 Users of @value{GDBN} often wish to obtain information about the state of
43421 the operating system running on the target---for example the list of
43422 processes, or the list of open files. This section describes the
43423 mechanism that makes it possible. This mechanism is similar to the
43424 target features mechanism (@pxref{Target Descriptions}), but focuses
43425 on a different aspect of target.
43427 Operating system information is retrived from the target via the
43428 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
43429 read}). The object name in the request should be @samp{osdata}, and
43430 the @var{annex} identifies the data to be fetched.
43433 @appendixsection Process list
43434 @cindex operating system information, process list
43436 When requesting the process list, the @var{annex} field in the
43437 @samp{qXfer} request should be @samp{processes}. The returned data is
43438 an XML document. The formal syntax of this document is defined in
43439 @file{gdb/features/osdata.dtd}.
43441 An example document is:
43444 <?xml version="1.0"?>
43445 <!DOCTYPE target SYSTEM "osdata.dtd">
43446 <osdata type="processes">
43448 <column name="pid">1</column>
43449 <column name="user">root</column>
43450 <column name="command">/sbin/init</column>
43451 <column name="cores">1,2,3</column>
43456 Each item should include a column whose name is @samp{pid}. The value
43457 of that column should identify the process on the target. The
43458 @samp{user} and @samp{command} columns are optional, and will be
43459 displayed by @value{GDBN}. The @samp{cores} column, if present,
43460 should contain a comma-separated list of cores that this process
43461 is running on. Target may provide additional columns,
43462 which @value{GDBN} currently ignores.
43464 @node Trace File Format
43465 @appendix Trace File Format
43466 @cindex trace file format
43468 The trace file comes in three parts: a header, a textual description
43469 section, and a trace frame section with binary data.
43471 The header has the form @code{\x7fTRACE0\n}. The first byte is
43472 @code{0x7f} so as to indicate that the file contains binary data,
43473 while the @code{0} is a version number that may have different values
43476 The description section consists of multiple lines of @sc{ascii} text
43477 separated by newline characters (@code{0xa}). The lines may include a
43478 variety of optional descriptive or context-setting information, such
43479 as tracepoint definitions or register set size. @value{GDBN} will
43480 ignore any line that it does not recognize. An empty line marks the end
43483 @c FIXME add some specific types of data
43485 The trace frame section consists of a number of consecutive frames.
43486 Each frame begins with a two-byte tracepoint number, followed by a
43487 four-byte size giving the amount of data in the frame. The data in
43488 the frame consists of a number of blocks, each introduced by a
43489 character indicating its type (at least register, memory, and trace
43490 state variable). The data in this section is raw binary, not a
43491 hexadecimal or other encoding; its endianness matches the target's
43494 @c FIXME bi-arch may require endianness/arch info in description section
43497 @item R @var{bytes}
43498 Register block. The number and ordering of bytes matches that of a
43499 @code{g} packet in the remote protocol. Note that these are the
43500 actual bytes, in target order and @value{GDBN} register order, not a
43501 hexadecimal encoding.
43503 @item M @var{address} @var{length} @var{bytes}...
43504 Memory block. This is a contiguous block of memory, at the 8-byte
43505 address @var{address}, with a 2-byte length @var{length}, followed by
43506 @var{length} bytes.
43508 @item V @var{number} @var{value}
43509 Trace state variable block. This records the 8-byte signed value
43510 @var{value} of trace state variable numbered @var{number}.
43514 Future enhancements of the trace file format may include additional types
43517 @node Index Section Format
43518 @appendix @code{.gdb_index} section format
43519 @cindex .gdb_index section format
43520 @cindex index section format
43522 This section documents the index section that is created by @code{save
43523 gdb-index} (@pxref{Index Files}). The index section is
43524 DWARF-specific; some knowledge of DWARF is assumed in this
43527 The mapped index file format is designed to be directly
43528 @code{mmap}able on any architecture. In most cases, a datum is
43529 represented using a little-endian 32-bit integer value, called an
43530 @code{offset_type}. Big endian machines must byte-swap the values
43531 before using them. Exceptions to this rule are noted. The data is
43532 laid out such that alignment is always respected.
43534 A mapped index consists of several areas, laid out in order.
43538 The file header. This is a sequence of values, of @code{offset_type}
43539 unless otherwise noted:
43543 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43544 Version 4 uses a different hashing function from versions 5 and 6.
43545 Version 6 includes symbols for inlined functions, whereas versions 4
43546 and 5 do not. Version 7 adds attributes to the CU indices in the
43547 symbol table. Version 8 specifies that symbols from DWARF type units
43548 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43549 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43551 @value{GDBN} will only read version 4, 5, or 6 indices
43552 by specifying @code{set use-deprecated-index-sections on}.
43553 GDB has a workaround for potentially broken version 7 indices so it is
43554 currently not flagged as deprecated.
43557 The offset, from the start of the file, of the CU list.
43560 The offset, from the start of the file, of the types CU list. Note
43561 that this area can be empty, in which case this offset will be equal
43562 to the next offset.
43565 The offset, from the start of the file, of the address area.
43568 The offset, from the start of the file, of the symbol table.
43571 The offset, from the start of the file, of the constant pool.
43575 The CU list. This is a sequence of pairs of 64-bit little-endian
43576 values, sorted by the CU offset. The first element in each pair is
43577 the offset of a CU in the @code{.debug_info} section. The second
43578 element in each pair is the length of that CU. References to a CU
43579 elsewhere in the map are done using a CU index, which is just the
43580 0-based index into this table. Note that if there are type CUs, then
43581 conceptually CUs and type CUs form a single list for the purposes of
43585 The types CU list. This is a sequence of triplets of 64-bit
43586 little-endian values. In a triplet, the first value is the CU offset,
43587 the second value is the type offset in the CU, and the third value is
43588 the type signature. The types CU list is not sorted.
43591 The address area. The address area consists of a sequence of address
43592 entries. Each address entry has three elements:
43596 The low address. This is a 64-bit little-endian value.
43599 The high address. This is a 64-bit little-endian value. Like
43600 @code{DW_AT_high_pc}, the value is one byte beyond the end.
43603 The CU index. This is an @code{offset_type} value.
43607 The symbol table. This is an open-addressed hash table. The size of
43608 the hash table is always a power of 2.
43610 Each slot in the hash table consists of a pair of @code{offset_type}
43611 values. The first value is the offset of the symbol's name in the
43612 constant pool. The second value is the offset of the CU vector in the
43615 If both values are 0, then this slot in the hash table is empty. This
43616 is ok because while 0 is a valid constant pool index, it cannot be a
43617 valid index for both a string and a CU vector.
43619 The hash value for a table entry is computed by applying an
43620 iterative hash function to the symbol's name. Starting with an
43621 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
43622 the string is incorporated into the hash using the formula depending on the
43627 The formula is @code{r = r * 67 + c - 113}.
43629 @item Versions 5 to 7
43630 The formula is @code{r = r * 67 + tolower (c) - 113}.
43633 The terminating @samp{\0} is not incorporated into the hash.
43635 The step size used in the hash table is computed via
43636 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43637 value, and @samp{size} is the size of the hash table. The step size
43638 is used to find the next candidate slot when handling a hash
43641 The names of C@t{++} symbols in the hash table are canonicalized. We
43642 don't currently have a simple description of the canonicalization
43643 algorithm; if you intend to create new index sections, you must read
43647 The constant pool. This is simply a bunch of bytes. It is organized
43648 so that alignment is correct: CU vectors are stored first, followed by
43651 A CU vector in the constant pool is a sequence of @code{offset_type}
43652 values. The first value is the number of CU indices in the vector.
43653 Each subsequent value is the index and symbol attributes of a CU in
43654 the CU list. This element in the hash table is used to indicate which
43655 CUs define the symbol and how the symbol is used.
43656 See below for the format of each CU index+attributes entry.
43658 A string in the constant pool is zero-terminated.
43661 Attributes were added to CU index values in @code{.gdb_index} version 7.
43662 If a symbol has multiple uses within a CU then there is one
43663 CU index+attributes value for each use.
43665 The format of each CU index+attributes entry is as follows
43671 This is the index of the CU in the CU list.
43673 These bits are reserved for future purposes and must be zero.
43675 The kind of the symbol in the CU.
43679 This value is reserved and should not be used.
43680 By reserving zero the full @code{offset_type} value is backwards compatible
43681 with previous versions of the index.
43683 The symbol is a type.
43685 The symbol is a variable or an enum value.
43687 The symbol is a function.
43689 Any other kind of symbol.
43691 These values are reserved.
43695 This bit is zero if the value is global and one if it is static.
43697 The determination of whether a symbol is global or static is complicated.
43698 The authorative reference is the file @file{dwarf2read.c} in
43699 @value{GDBN} sources.
43703 This pseudo-code describes the computation of a symbol's kind and
43704 global/static attributes in the index.
43707 is_external = get_attribute (die, DW_AT_external);
43708 language = get_attribute (cu_die, DW_AT_language);
43711 case DW_TAG_typedef:
43712 case DW_TAG_base_type:
43713 case DW_TAG_subrange_type:
43717 case DW_TAG_enumerator:
43719 is_static = (language != CPLUS && language != JAVA);
43721 case DW_TAG_subprogram:
43723 is_static = ! (is_external || language == ADA);
43725 case DW_TAG_constant:
43727 is_static = ! is_external;
43729 case DW_TAG_variable:
43731 is_static = ! is_external;
43733 case DW_TAG_namespace:
43737 case DW_TAG_class_type:
43738 case DW_TAG_interface_type:
43739 case DW_TAG_structure_type:
43740 case DW_TAG_union_type:
43741 case DW_TAG_enumeration_type:
43743 is_static = (language != CPLUS && language != JAVA);
43751 @appendix Manual pages
43755 * gdb man:: The GNU Debugger man page
43756 * gdbserver man:: Remote Server for the GNU Debugger man page
43757 * gcore man:: Generate a core file of a running program
43758 * gdbinit man:: gdbinit scripts
43764 @c man title gdb The GNU Debugger
43766 @c man begin SYNOPSIS gdb
43767 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
43768 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
43769 [@option{-b}@w{ }@var{bps}]
43770 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
43771 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
43772 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
43773 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
43774 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
43777 @c man begin DESCRIPTION gdb
43778 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
43779 going on ``inside'' another program while it executes -- or what another
43780 program was doing at the moment it crashed.
43782 @value{GDBN} can do four main kinds of things (plus other things in support of
43783 these) to help you catch bugs in the act:
43787 Start your program, specifying anything that might affect its behavior.
43790 Make your program stop on specified conditions.
43793 Examine what has happened, when your program has stopped.
43796 Change things in your program, so you can experiment with correcting the
43797 effects of one bug and go on to learn about another.
43800 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
43803 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
43804 commands from the terminal until you tell it to exit with the @value{GDBN}
43805 command @code{quit}. You can get online help from @value{GDBN} itself
43806 by using the command @code{help}.
43808 You can run @code{gdb} with no arguments or options; but the most
43809 usual way to start @value{GDBN} is with one argument or two, specifying an
43810 executable program as the argument:
43816 You can also start with both an executable program and a core file specified:
43822 You can, instead, specify a process ID as a second argument, if you want
43823 to debug a running process:
43831 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43832 named @file{1234}; @value{GDBN} does check for a core file first).
43833 With option @option{-p} you can omit the @var{program} filename.
43835 Here are some of the most frequently needed @value{GDBN} commands:
43837 @c pod2man highlights the right hand side of the @item lines.
43839 @item break [@var{file}:]@var{functiop}
43840 Set a breakpoint at @var{function} (in @var{file}).
43842 @item run [@var{arglist}]
43843 Start your program (with @var{arglist}, if specified).
43846 Backtrace: display the program stack.
43848 @item print @var{expr}
43849 Display the value of an expression.
43852 Continue running your program (after stopping, e.g. at a breakpoint).
43855 Execute next program line (after stopping); step @emph{over} any
43856 function calls in the line.
43858 @item edit [@var{file}:]@var{function}
43859 look at the program line where it is presently stopped.
43861 @item list [@var{file}:]@var{function}
43862 type the text of the program in the vicinity of where it is presently stopped.
43865 Execute next program line (after stopping); step @emph{into} any
43866 function calls in the line.
43868 @item help [@var{name}]
43869 Show information about @value{GDBN} command @var{name}, or general information
43870 about using @value{GDBN}.
43873 Exit from @value{GDBN}.
43877 For full details on @value{GDBN},
43878 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43879 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43880 as the @code{gdb} entry in the @code{info} program.
43884 @c man begin OPTIONS gdb
43885 Any arguments other than options specify an executable
43886 file and core file (or process ID); that is, the first argument
43887 encountered with no
43888 associated option flag is equivalent to a @option{-se} option, and the second,
43889 if any, is equivalent to a @option{-c} option if it's the name of a file.
43891 both long and short forms; both are shown here. The long forms are also
43892 recognized if you truncate them, so long as enough of the option is
43893 present to be unambiguous. (If you prefer, you can flag option
43894 arguments with @option{+} rather than @option{-}, though we illustrate the
43895 more usual convention.)
43897 All the options and command line arguments you give are processed
43898 in sequential order. The order makes a difference when the @option{-x}
43904 List all options, with brief explanations.
43906 @item -symbols=@var{file}
43907 @itemx -s @var{file}
43908 Read symbol table from file @var{file}.
43911 Enable writing into executable and core files.
43913 @item -exec=@var{file}
43914 @itemx -e @var{file}
43915 Use file @var{file} as the executable file to execute when
43916 appropriate, and for examining pure data in conjunction with a core
43919 @item -se=@var{file}
43920 Read symbol table from file @var{file} and use it as the executable
43923 @item -core=@var{file}
43924 @itemx -c @var{file}
43925 Use file @var{file} as a core dump to examine.
43927 @item -command=@var{file}
43928 @itemx -x @var{file}
43929 Execute @value{GDBN} commands from file @var{file}.
43931 @item -ex @var{command}
43932 Execute given @value{GDBN} @var{command}.
43934 @item -directory=@var{directory}
43935 @itemx -d @var{directory}
43936 Add @var{directory} to the path to search for source files.
43939 Do not execute commands from @file{~/.gdbinit}.
43943 Do not execute commands from any @file{.gdbinit} initialization files.
43947 ``Quiet''. Do not print the introductory and copyright messages. These
43948 messages are also suppressed in batch mode.
43951 Run in batch mode. Exit with status @code{0} after processing all the command
43952 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
43953 Exit with nonzero status if an error occurs in executing the @value{GDBN}
43954 commands in the command files.
43956 Batch mode may be useful for running @value{GDBN} as a filter, for example to
43957 download and run a program on another computer; in order to make this
43958 more useful, the message
43961 Program exited normally.
43965 (which is ordinarily issued whenever a program running under @value{GDBN} control
43966 terminates) is not issued when running in batch mode.
43968 @item -cd=@var{directory}
43969 Run @value{GDBN} using @var{directory} as its working directory,
43970 instead of the current directory.
43974 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
43975 @value{GDBN} to output the full file name and line number in a standard,
43976 recognizable fashion each time a stack frame is displayed (which
43977 includes each time the program stops). This recognizable format looks
43978 like two @samp{\032} characters, followed by the file name, line number
43979 and character position separated by colons, and a newline. The
43980 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
43981 characters as a signal to display the source code for the frame.
43984 Set the line speed (baud rate or bits per second) of any serial
43985 interface used by @value{GDBN} for remote debugging.
43987 @item -tty=@var{device}
43988 Run using @var{device} for your program's standard input and output.
43992 @c man begin SEEALSO gdb
43994 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43995 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43996 documentation are properly installed at your site, the command
44003 should give you access to the complete manual.
44005 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44006 Richard M. Stallman and Roland H. Pesch, July 1991.
44010 @node gdbserver man
44011 @heading gdbserver man
44013 @c man title gdbserver Remote Server for the GNU Debugger
44015 @c man begin SYNOPSIS gdbserver
44016 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44018 gdbserver --attach @var{comm} @var{pid}
44020 gdbserver --multi @var{comm}
44024 @c man begin DESCRIPTION gdbserver
44025 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
44026 than the one which is running the program being debugged.
44029 @subheading Usage (server (target) side)
44032 Usage (server (target) side):
44035 First, you need to have a copy of the program you want to debug put onto
44036 the target system. The program can be stripped to save space if needed, as
44037 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
44038 the @value{GDBN} running on the host system.
44040 To use the server, you log on to the target system, and run the @command{gdbserver}
44041 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
44042 your program, and (c) its arguments. The general syntax is:
44045 target> gdbserver @var{comm} @var{program} [@var{args} ...]
44048 For example, using a serial port, you might say:
44052 @c @file would wrap it as F</dev/com1>.
44053 target> gdbserver /dev/com1 emacs foo.txt
44056 target> gdbserver @file{/dev/com1} emacs foo.txt
44060 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
44061 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
44062 waits patiently for the host @value{GDBN} to communicate with it.
44064 To use a TCP connection, you could say:
44067 target> gdbserver host:2345 emacs foo.txt
44070 This says pretty much the same thing as the last example, except that we are
44071 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
44072 that we are expecting to see a TCP connection from @code{host} to local TCP port
44073 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
44074 want for the port number as long as it does not conflict with any existing TCP
44075 ports on the target system. This same port number must be used in the host
44076 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
44077 you chose a port number that conflicts with another service, @command{gdbserver} will
44078 print an error message and exit.
44080 @command{gdbserver} can also attach to running programs.
44081 This is accomplished via the @option{--attach} argument. The syntax is:
44084 target> gdbserver --attach @var{comm} @var{pid}
44087 @var{pid} is the process ID of a currently running process. It isn't
44088 necessary to point @command{gdbserver} at a binary for the running process.
44090 To start @code{gdbserver} without supplying an initial command to run
44091 or process ID to attach, use the @option{--multi} command line option.
44092 In such case you should connect using @kbd{target extended-remote} to start
44093 the program you want to debug.
44096 target> gdbserver --multi @var{comm}
44100 @subheading Usage (host side)
44106 You need an unstripped copy of the target program on your host system, since
44107 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
44108 would, with the target program as the first argument. (You may need to use the
44109 @option{--baud} option if the serial line is running at anything except 9600 baud.)
44110 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
44111 new command you need to know about is @code{target remote}
44112 (or @code{target extended-remote}). Its argument is either
44113 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
44114 descriptor. For example:
44118 @c @file would wrap it as F</dev/ttyb>.
44119 (gdb) target remote /dev/ttyb
44122 (gdb) target remote @file{/dev/ttyb}
44127 communicates with the server via serial line @file{/dev/ttyb}, and:
44130 (gdb) target remote the-target:2345
44134 communicates via a TCP connection to port 2345 on host `the-target', where
44135 you previously started up @command{gdbserver} with the same port number. Note that for
44136 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
44137 command, otherwise you may get an error that looks something like
44138 `Connection refused'.
44140 @command{gdbserver} can also debug multiple inferiors at once,
44143 the @value{GDBN} manual in node @code{Inferiors and Programs}
44144 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
44147 @ref{Inferiors and Programs}.
44149 In such case use the @code{extended-remote} @value{GDBN} command variant:
44152 (gdb) target extended-remote the-target:2345
44155 The @command{gdbserver} option @option{--multi} may or may not be used in such
44159 @c man begin OPTIONS gdbserver
44160 There are three different modes for invoking @command{gdbserver}:
44165 Debug a specific program specified by its program name:
44168 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44171 The @var{comm} parameter specifies how should the server communicate
44172 with @value{GDBN}; it is either a device name (to use a serial line),
44173 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
44174 stdin/stdout of @code{gdbserver}. Specify the name of the program to
44175 debug in @var{prog}. Any remaining arguments will be passed to the
44176 program verbatim. When the program exits, @value{GDBN} will close the
44177 connection, and @code{gdbserver} will exit.
44180 Debug a specific program by specifying the process ID of a running
44184 gdbserver --attach @var{comm} @var{pid}
44187 The @var{comm} parameter is as described above. Supply the process ID
44188 of a running program in @var{pid}; @value{GDBN} will do everything
44189 else. Like with the previous mode, when the process @var{pid} exits,
44190 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
44193 Multi-process mode -- debug more than one program/process:
44196 gdbserver --multi @var{comm}
44199 In this mode, @value{GDBN} can instruct @command{gdbserver} which
44200 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
44201 close the connection when a process being debugged exits, so you can
44202 debug several processes in the same session.
44205 In each of the modes you may specify these options:
44210 List all options, with brief explanations.
44213 This option causes @command{gdbserver} to print its version number and exit.
44216 @command{gdbserver} will attach to a running program. The syntax is:
44219 target> gdbserver --attach @var{comm} @var{pid}
44222 @var{pid} is the process ID of a currently running process. It isn't
44223 necessary to point @command{gdbserver} at a binary for the running process.
44226 To start @code{gdbserver} without supplying an initial command to run
44227 or process ID to attach, use this command line option.
44228 Then you can connect using @kbd{target extended-remote} and start
44229 the program you want to debug. The syntax is:
44232 target> gdbserver --multi @var{comm}
44236 Instruct @code{gdbserver} to display extra status information about the debugging
44238 This option is intended for @code{gdbserver} development and for bug reports to
44241 @item --remote-debug
44242 Instruct @code{gdbserver} to display remote protocol debug output.
44243 This option is intended for @code{gdbserver} development and for bug reports to
44247 Specify a wrapper to launch programs
44248 for debugging. The option should be followed by the name of the
44249 wrapper, then any command-line arguments to pass to the wrapper, then
44250 @kbd{--} indicating the end of the wrapper arguments.
44253 By default, @command{gdbserver} keeps the listening TCP port open, so that
44254 additional connections are possible. However, if you start @code{gdbserver}
44255 with the @option{--once} option, it will stop listening for any further
44256 connection attempts after connecting to the first @value{GDBN} session.
44258 @c --disable-packet is not documented for users.
44260 @c --disable-randomization and --no-disable-randomization are superseded by
44261 @c QDisableRandomization.
44266 @c man begin SEEALSO gdbserver
44268 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44269 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44270 documentation are properly installed at your site, the command
44276 should give you access to the complete manual.
44278 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44279 Richard M. Stallman and Roland H. Pesch, July 1991.
44286 @c man title gcore Generate a core file of a running program
44289 @c man begin SYNOPSIS gcore
44290 gcore [-o @var{filename}] @var{pid}
44294 @c man begin DESCRIPTION gcore
44295 Generate a core dump of a running program with process ID @var{pid}.
44296 Produced file is equivalent to a kernel produced core file as if the process
44297 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
44298 limit). Unlike after a crash, after @command{gcore} the program remains
44299 running without any change.
44302 @c man begin OPTIONS gcore
44304 @item -o @var{filename}
44305 The optional argument
44306 @var{filename} specifies the file name where to put the core dump.
44307 If not specified, the file name defaults to @file{core.@var{pid}},
44308 where @var{pid} is the running program process ID.
44312 @c man begin SEEALSO gcore
44314 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44315 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44316 documentation are properly installed at your site, the command
44323 should give you access to the complete manual.
44325 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44326 Richard M. Stallman and Roland H. Pesch, July 1991.
44333 @c man title gdbinit GDB initialization scripts
44336 @c man begin SYNOPSIS gdbinit
44337 @ifset SYSTEM_GDBINIT
44338 @value{SYSTEM_GDBINIT}
44347 @c man begin DESCRIPTION gdbinit
44348 These files contain @value{GDBN} commands to automatically execute during
44349 @value{GDBN} startup. The lines of contents are canned sequences of commands,
44352 the @value{GDBN} manual in node @code{Sequences}
44353 -- shell command @code{info -f gdb -n Sequences}.
44359 Please read more in
44361 the @value{GDBN} manual in node @code{Startup}
44362 -- shell command @code{info -f gdb -n Startup}.
44369 @ifset SYSTEM_GDBINIT
44370 @item @value{SYSTEM_GDBINIT}
44372 @ifclear SYSTEM_GDBINIT
44373 @item (not enabled with @code{--with-system-gdbinit} during compilation)
44375 System-wide initialization file. It is executed unless user specified
44376 @value{GDBN} option @code{-nx} or @code{-n}.
44379 the @value{GDBN} manual in node @code{System-wide configuration}
44380 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
44383 @ref{System-wide configuration}.
44387 User initialization file. It is executed unless user specified
44388 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
44391 Initialization file for current directory. It may need to be enabled with
44392 @value{GDBN} security command @code{set auto-load local-gdbinit}.
44395 the @value{GDBN} manual in node @code{Init File in the Current Directory}
44396 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
44399 @ref{Init File in the Current Directory}.
44404 @c man begin SEEALSO gdbinit
44406 gdb(1), @code{info -f gdb -n Startup}
44408 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44409 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44410 documentation are properly installed at your site, the command
44416 should give you access to the complete manual.
44418 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44419 Richard M. Stallman and Roland H. Pesch, July 1991.
44425 @node GNU Free Documentation License
44426 @appendix GNU Free Documentation License
44429 @node Concept Index
44430 @unnumbered Concept Index
44434 @node Command and Variable Index
44435 @unnumbered Command, Variable, and Function Index
44440 % I think something like @@colophon should be in texinfo. In the
44442 \long\def\colophon{\hbox to0pt{}\vfill
44443 \centerline{The body of this manual is set in}
44444 \centerline{\fontname\tenrm,}
44445 \centerline{with headings in {\bf\fontname\tenbf}}
44446 \centerline{and examples in {\tt\fontname\tentt}.}
44447 \centerline{{\it\fontname\tenit\/},}
44448 \centerline{{\bf\fontname\tenbf}, and}
44449 \centerline{{\sl\fontname\tensl\/}}
44450 \centerline{are used for emphasis.}\vfill}
44452 % Blame: doc@@cygnus.com, 1991.