1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
35 @c !!set GDB edit command default editor
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
44 * Gdb: (gdb). The GNU debugger.
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
50 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.3 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
104 This edition of the GDB manual is dedicated to the memory of Fred
105 Fish. Fred was a long-standing contributor to GDB and to Free
106 software in general. We will miss him.
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) 1988-2010 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.
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 * Command Line Editing:: Command Line Editing
167 * Using History Interactively:: Using History Interactively
168 * Formatting Documentation:: How to format and print @value{GDBN} documentation
169 * Installing GDB:: Installing GDB
170 * Maintenance Commands:: Maintenance Commands
171 * Remote Protocol:: GDB Remote Serial Protocol
172 * Agent Expressions:: The GDB Agent Expression Mechanism
173 * Target Descriptions:: How targets can describe themselves to
175 * Operating System Information:: Getting additional information from
177 * Trace File Format:: GDB trace file format
178 * Copying:: GNU General Public License says
179 how you can copy and share GDB
180 * GNU Free Documentation License:: The license for this documentation
189 @unnumbered Summary of @value{GDBN}
191 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
192 going on ``inside'' another program while it executes---or what another
193 program was doing at the moment it crashed.
195 @value{GDBN} can do four main kinds of things (plus other things in support of
196 these) to help you catch bugs in the act:
200 Start your program, specifying anything that might affect its behavior.
203 Make your program stop on specified conditions.
206 Examine what has happened, when your program has stopped.
209 Change things in your program, so you can experiment with correcting the
210 effects of one bug and go on to learn about another.
213 You can use @value{GDBN} to debug programs written in C and C@t{++}.
214 For more information, see @ref{Supported Languages,,Supported Languages}.
215 For more information, see @ref{C,,C and C++}.
217 Support for D is partial. For information on D, see
221 Support for Modula-2 is partial. For information on Modula-2, see
222 @ref{Modula-2,,Modula-2}.
225 Debugging Pascal programs which use sets, subranges, file variables, or
226 nested functions does not currently work. @value{GDBN} does not support
227 entering expressions, printing values, or similar features using Pascal
231 @value{GDBN} can be used to debug programs written in Fortran, although
232 it may be necessary to refer to some variables with a trailing
235 @value{GDBN} can be used to debug programs written in Objective-C,
236 using either the Apple/NeXT or the GNU Objective-C runtime.
239 * Free Software:: Freely redistributable software
240 * Contributors:: Contributors to GDB
244 @unnumberedsec Free Software
246 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
247 General Public License
248 (GPL). The GPL gives you the freedom to copy or adapt a licensed
249 program---but every person getting a copy also gets with it the
250 freedom to modify that copy (which means that they must get access to
251 the source code), and the freedom to distribute further copies.
252 Typical software companies use copyrights to limit your freedoms; the
253 Free Software Foundation uses the GPL to preserve these freedoms.
255 Fundamentally, the General Public License is a license which says that
256 you have these freedoms and that you cannot take these freedoms away
259 @unnumberedsec Free Software Needs Free Documentation
261 The biggest deficiency in the free software community today is not in
262 the software---it is the lack of good free documentation that we can
263 include with the free software. Many of our most important
264 programs do not come with free reference manuals and free introductory
265 texts. Documentation is an essential part of any software package;
266 when an important free software package does not come with a free
267 manual and a free tutorial, that is a major gap. We have many such
270 Consider Perl, for instance. The tutorial manuals that people
271 normally use are non-free. How did this come about? Because the
272 authors of those manuals published them with restrictive terms---no
273 copying, no modification, source files not available---which exclude
274 them from the free software world.
276 That wasn't the first time this sort of thing happened, and it was far
277 from the last. Many times we have heard a GNU user eagerly describe a
278 manual that he is writing, his intended contribution to the community,
279 only to learn that he had ruined everything by signing a publication
280 contract to make it non-free.
282 Free documentation, like free software, is a matter of freedom, not
283 price. The problem with the non-free manual is not that publishers
284 charge a price for printed copies---that in itself is fine. (The Free
285 Software Foundation sells printed copies of manuals, too.) The
286 problem is the restrictions on the use of the manual. Free manuals
287 are available in source code form, and give you permission to copy and
288 modify. Non-free manuals do not allow this.
290 The criteria of freedom for a free manual are roughly the same as for
291 free software. Redistribution (including the normal kinds of
292 commercial redistribution) must be permitted, so that the manual can
293 accompany every copy of the program, both on-line and on paper.
295 Permission for modification of the technical content is crucial too.
296 When people modify the software, adding or changing features, if they
297 are conscientious they will change the manual too---so they can
298 provide accurate and clear documentation for the modified program. A
299 manual that leaves you no choice but to write a new manual to document
300 a changed version of the program is not really available to our
303 Some kinds of limits on the way modification is handled are
304 acceptable. For example, requirements to preserve the original
305 author's copyright notice, the distribution terms, or the list of
306 authors, are ok. It is also no problem to require modified versions
307 to include notice that they were modified. Even entire sections that
308 may not be deleted or changed are acceptable, as long as they deal
309 with nontechnical topics (like this one). These kinds of restrictions
310 are acceptable because they don't obstruct the community's normal use
313 However, it must be possible to modify all the @emph{technical}
314 content of the manual, and then distribute the result in all the usual
315 media, through all the usual channels. Otherwise, the restrictions
316 obstruct the use of the manual, it is not free, and we need another
317 manual to replace it.
319 Please spread the word about this issue. Our community continues to
320 lose manuals to proprietary publishing. If we spread the word that
321 free software needs free reference manuals and free tutorials, perhaps
322 the next person who wants to contribute by writing documentation will
323 realize, before it is too late, that only free manuals contribute to
324 the free software community.
326 If you are writing documentation, please insist on publishing it under
327 the GNU Free Documentation License or another free documentation
328 license. Remember that this decision requires your approval---you
329 don't have to let the publisher decide. Some commercial publishers
330 will use a free license if you insist, but they will not propose the
331 option; it is up to you to raise the issue and say firmly that this is
332 what you want. If the publisher you are dealing with refuses, please
333 try other publishers. If you're not sure whether a proposed license
334 is free, write to @email{licensing@@gnu.org}.
336 You can encourage commercial publishers to sell more free, copylefted
337 manuals and tutorials by buying them, and particularly by buying
338 copies from the publishers that paid for their writing or for major
339 improvements. Meanwhile, try to avoid buying non-free documentation
340 at all. Check the distribution terms of a manual before you buy it,
341 and insist that whoever seeks your business must respect your freedom.
342 Check the history of the book, and try to reward the publishers that
343 have paid or pay the authors to work on it.
345 The Free Software Foundation maintains a list of free documentation
346 published by other publishers, at
347 @url{http://www.fsf.org/doc/other-free-books.html}.
350 @unnumberedsec Contributors to @value{GDBN}
352 Richard Stallman was the original author of @value{GDBN}, and of many
353 other @sc{gnu} programs. Many others have contributed to its
354 development. This section attempts to credit major contributors. One
355 of the virtues of free software is that everyone is free to contribute
356 to it; with regret, we cannot actually acknowledge everyone here. The
357 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
358 blow-by-blow account.
360 Changes much prior to version 2.0 are lost in the mists of time.
363 @emph{Plea:} Additions to this section are particularly welcome. If you
364 or your friends (or enemies, to be evenhanded) have been unfairly
365 omitted from this list, we would like to add your names!
368 So that they may not regard their many labors as thankless, we
369 particularly thank those who shepherded @value{GDBN} through major
371 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
372 Jim Blandy (release 4.18);
373 Jason Molenda (release 4.17);
374 Stan Shebs (release 4.14);
375 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
376 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
377 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
378 Jim Kingdon (releases 3.5, 3.4, and 3.3);
379 and Randy Smith (releases 3.2, 3.1, and 3.0).
381 Richard Stallman, assisted at various times by Peter TerMaat, Chris
382 Hanson, and Richard Mlynarik, handled releases through 2.8.
384 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
385 in @value{GDBN}, with significant additional contributions from Per
386 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
387 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
388 much general update work leading to release 3.0).
390 @value{GDBN} uses the BFD subroutine library to examine multiple
391 object-file formats; BFD was a joint project of David V.
392 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
394 David Johnson wrote the original COFF support; Pace Willison did
395 the original support for encapsulated COFF.
397 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
399 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
400 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
402 Jean-Daniel Fekete contributed Sun 386i support.
403 Chris Hanson improved the HP9000 support.
404 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
405 David Johnson contributed Encore Umax support.
406 Jyrki Kuoppala contributed Altos 3068 support.
407 Jeff Law contributed HP PA and SOM support.
408 Keith Packard contributed NS32K support.
409 Doug Rabson contributed Acorn Risc Machine support.
410 Bob Rusk contributed Harris Nighthawk CX-UX support.
411 Chris Smith contributed Convex support (and Fortran debugging).
412 Jonathan Stone contributed Pyramid support.
413 Michael Tiemann contributed SPARC support.
414 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
415 Pace Willison contributed Intel 386 support.
416 Jay Vosburgh contributed Symmetry support.
417 Marko Mlinar contributed OpenRISC 1000 support.
419 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
421 Rich Schaefer and Peter Schauer helped with support of SunOS shared
424 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
425 about several machine instruction sets.
427 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
428 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
429 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
430 and RDI targets, respectively.
432 Brian Fox is the author of the readline libraries providing
433 command-line editing and command history.
435 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
436 Modula-2 support, and contributed the Languages chapter of this manual.
438 Fred Fish wrote most of the support for Unix System Vr4.
439 He also enhanced the command-completion support to cover C@t{++} overloaded
442 Hitachi America (now Renesas America), Ltd. sponsored the support for
443 H8/300, H8/500, and Super-H processors.
445 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
447 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
450 Toshiba sponsored the support for the TX39 Mips processor.
452 Matsushita sponsored the support for the MN10200 and MN10300 processors.
454 Fujitsu sponsored the support for SPARClite and FR30 processors.
456 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
459 Michael Snyder added support for tracepoints.
461 Stu Grossman wrote gdbserver.
463 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
464 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
466 The following people at the Hewlett-Packard Company contributed
467 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
468 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
469 compiler, and the Text User Interface (nee Terminal User Interface):
470 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
471 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
472 provided HP-specific information in this manual.
474 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
475 Robert Hoehne made significant contributions to the DJGPP port.
477 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
478 development since 1991. Cygnus engineers who have worked on @value{GDBN}
479 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
480 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
481 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
482 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
483 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
484 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
485 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
486 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
487 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
488 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
489 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
490 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
491 Zuhn have made contributions both large and small.
493 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
494 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
496 Jim Blandy added support for preprocessor macros, while working for Red
499 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
500 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
501 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
502 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
503 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
504 with the migration of old architectures to this new framework.
506 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
507 unwinder framework, this consisting of a fresh new design featuring
508 frame IDs, independent frame sniffers, and the sentinel frame. Mark
509 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
510 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
511 trad unwinders. The architecture-specific changes, each involving a
512 complete rewrite of the architecture's frame code, were carried out by
513 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
514 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
515 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
516 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
519 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
520 Tensilica, Inc.@: contributed support for Xtensa processors. Others
521 who have worked on the Xtensa port of @value{GDBN} in the past include
522 Steve Tjiang, John Newlin, and Scott Foehner.
524 Michael Eager and staff of Xilinx, Inc., contributed support for the
525 Xilinx MicroBlaze architecture.
528 @chapter A Sample @value{GDBN} Session
530 You can use this manual at your leisure to read all about @value{GDBN}.
531 However, a handful of commands are enough to get started using the
532 debugger. This chapter illustrates those commands.
535 In this sample session, we emphasize user input like this: @b{input},
536 to make it easier to pick out from the surrounding output.
539 @c FIXME: this example may not be appropriate for some configs, where
540 @c FIXME...primary interest is in remote use.
542 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
543 processor) exhibits the following bug: sometimes, when we change its
544 quote strings from the default, the commands used to capture one macro
545 definition within another stop working. In the following short @code{m4}
546 session, we define a macro @code{foo} which expands to @code{0000}; we
547 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
548 same thing. However, when we change the open quote string to
549 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
550 procedure fails to define a new synonym @code{baz}:
559 @b{define(bar,defn(`foo'))}
563 @b{changequote(<QUOTE>,<UNQUOTE>)}
565 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
568 m4: End of input: 0: fatal error: EOF in string
572 Let us use @value{GDBN} to try to see what is going on.
575 $ @b{@value{GDBP} m4}
576 @c FIXME: this falsifies the exact text played out, to permit smallbook
577 @c FIXME... format to come out better.
578 @value{GDBN} is free software and you are welcome to distribute copies
579 of it under certain conditions; type "show copying" to see
581 There is absolutely no warranty for @value{GDBN}; type "show warranty"
584 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
589 @value{GDBN} reads only enough symbol data to know where to find the
590 rest when needed; as a result, the first prompt comes up very quickly.
591 We now tell @value{GDBN} to use a narrower display width than usual, so
592 that examples fit in this manual.
595 (@value{GDBP}) @b{set width 70}
599 We need to see how the @code{m4} built-in @code{changequote} works.
600 Having looked at the source, we know the relevant subroutine is
601 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
602 @code{break} command.
605 (@value{GDBP}) @b{break m4_changequote}
606 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
610 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
611 control; as long as control does not reach the @code{m4_changequote}
612 subroutine, the program runs as usual:
615 (@value{GDBP}) @b{run}
616 Starting program: /work/Editorial/gdb/gnu/m4/m4
624 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
625 suspends execution of @code{m4}, displaying information about the
626 context where it stops.
629 @b{changequote(<QUOTE>,<UNQUOTE>)}
631 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
633 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
637 Now we use the command @code{n} (@code{next}) to advance execution to
638 the next line of the current function.
642 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
647 @code{set_quotes} looks like a promising subroutine. We can go into it
648 by using the command @code{s} (@code{step}) instead of @code{next}.
649 @code{step} goes to the next line to be executed in @emph{any}
650 subroutine, so it steps into @code{set_quotes}.
654 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
656 530 if (lquote != def_lquote)
660 The display that shows the subroutine where @code{m4} is now
661 suspended (and its arguments) is called a stack frame display. It
662 shows a summary of the stack. We can use the @code{backtrace}
663 command (which can also be spelled @code{bt}), to see where we are
664 in the stack as a whole: the @code{backtrace} command displays a
665 stack frame for each active subroutine.
668 (@value{GDBP}) @b{bt}
669 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
671 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
673 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
674 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
676 #4 0x79dc in expand_input () at macro.c:40
677 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
681 We step through a few more lines to see what happens. The first two
682 times, we can use @samp{s}; the next two times we use @code{n} to avoid
683 falling into the @code{xstrdup} subroutine.
687 0x3b5c 532 if (rquote != def_rquote)
689 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
690 def_lquote : xstrdup(lq);
692 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
695 538 len_lquote = strlen(rquote);
699 The last line displayed looks a little odd; we can examine the variables
700 @code{lquote} and @code{rquote} to see if they are in fact the new left
701 and right quotes we specified. We use the command @code{p}
702 (@code{print}) to see their values.
705 (@value{GDBP}) @b{p lquote}
706 $1 = 0x35d40 "<QUOTE>"
707 (@value{GDBP}) @b{p rquote}
708 $2 = 0x35d50 "<UNQUOTE>"
712 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
713 To look at some context, we can display ten lines of source
714 surrounding the current line with the @code{l} (@code{list}) command.
720 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
722 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
725 538 len_lquote = strlen(rquote);
726 539 len_rquote = strlen(lquote);
733 Let us step past the two lines that set @code{len_lquote} and
734 @code{len_rquote}, and then examine the values of those variables.
738 539 len_rquote = strlen(lquote);
741 (@value{GDBP}) @b{p len_lquote}
743 (@value{GDBP}) @b{p len_rquote}
748 That certainly looks wrong, assuming @code{len_lquote} and
749 @code{len_rquote} are meant to be the lengths of @code{lquote} and
750 @code{rquote} respectively. We can set them to better values using
751 the @code{p} command, since it can print the value of
752 any expression---and that expression can include subroutine calls and
756 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
758 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
763 Is that enough to fix the problem of using the new quotes with the
764 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
765 executing with the @code{c} (@code{continue}) command, and then try the
766 example that caused trouble initially:
772 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
779 Success! The new quotes now work just as well as the default ones. The
780 problem seems to have been just the two typos defining the wrong
781 lengths. We allow @code{m4} exit by giving it an EOF as input:
785 Program exited normally.
789 The message @samp{Program exited normally.} is from @value{GDBN}; it
790 indicates @code{m4} has finished executing. We can end our @value{GDBN}
791 session with the @value{GDBN} @code{quit} command.
794 (@value{GDBP}) @b{quit}
798 @chapter Getting In and Out of @value{GDBN}
800 This chapter discusses how to start @value{GDBN}, and how to get out of it.
804 type @samp{@value{GDBP}} to start @value{GDBN}.
806 type @kbd{quit} or @kbd{Ctrl-d} to exit.
810 * Invoking GDB:: How to start @value{GDBN}
811 * Quitting GDB:: How to quit @value{GDBN}
812 * Shell Commands:: How to use shell commands inside @value{GDBN}
813 * Logging Output:: How to log @value{GDBN}'s output to a file
817 @section Invoking @value{GDBN}
819 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
820 @value{GDBN} reads commands from the terminal until you tell it to exit.
822 You can also run @code{@value{GDBP}} with a variety of arguments and options,
823 to specify more of your debugging environment at the outset.
825 The command-line options described here are designed
826 to cover a variety of situations; in some environments, some of these
827 options may effectively be unavailable.
829 The most usual way to start @value{GDBN} is with one argument,
830 specifying an executable program:
833 @value{GDBP} @var{program}
837 You can also start with both an executable program and a core file
841 @value{GDBP} @var{program} @var{core}
844 You can, instead, specify a process ID as a second argument, if you want
845 to debug a running process:
848 @value{GDBP} @var{program} 1234
852 would attach @value{GDBN} to process @code{1234} (unless you also have a file
853 named @file{1234}; @value{GDBN} does check for a core file first).
855 Taking advantage of the second command-line argument requires a fairly
856 complete operating system; when you use @value{GDBN} as a remote
857 debugger attached to a bare board, there may not be any notion of
858 ``process'', and there is often no way to get a core dump. @value{GDBN}
859 will warn you if it is unable to attach or to read core dumps.
861 You can optionally have @code{@value{GDBP}} pass any arguments after the
862 executable file to the inferior using @code{--args}. This option stops
865 @value{GDBP} --args gcc -O2 -c foo.c
867 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
868 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
870 You can run @code{@value{GDBP}} without printing the front material, which describes
871 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
878 You can further control how @value{GDBN} starts up by using command-line
879 options. @value{GDBN} itself can remind you of the options available.
889 to display all available options and briefly describe their use
890 (@samp{@value{GDBP} -h} is a shorter equivalent).
892 All options and command line arguments you give are processed
893 in sequential order. The order makes a difference when the
894 @samp{-x} option is used.
898 * File Options:: Choosing files
899 * Mode Options:: Choosing modes
900 * Startup:: What @value{GDBN} does during startup
904 @subsection Choosing Files
906 When @value{GDBN} starts, it reads any arguments other than options as
907 specifying an executable file and core file (or process ID). This is
908 the same as if the arguments were specified by the @samp{-se} and
909 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
910 first argument that does not have an associated option flag as
911 equivalent to the @samp{-se} option followed by that argument; and the
912 second argument that does not have an associated option flag, if any, as
913 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
914 If the second argument begins with a decimal digit, @value{GDBN} will
915 first attempt to attach to it as a process, and if that fails, attempt
916 to open it as a corefile. If you have a corefile whose name begins with
917 a digit, you can prevent @value{GDBN} from treating it as a pid by
918 prefixing it with @file{./}, e.g.@: @file{./12345}.
920 If @value{GDBN} has not been configured to included core file support,
921 such as for most embedded targets, then it will complain about a second
922 argument and ignore it.
924 Many options have both long and short forms; both are shown in the
925 following list. @value{GDBN} also recognizes the long forms if you truncate
926 them, so long as enough of the option is present to be unambiguous.
927 (If you prefer, you can flag option arguments with @samp{--} rather
928 than @samp{-}, though we illustrate the more usual convention.)
930 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
931 @c way, both those who look for -foo and --foo in the index, will find
935 @item -symbols @var{file}
937 @cindex @code{--symbols}
939 Read symbol table from file @var{file}.
941 @item -exec @var{file}
943 @cindex @code{--exec}
945 Use file @var{file} as the executable file to execute when appropriate,
946 and for examining pure data in conjunction with a core dump.
950 Read symbol table from file @var{file} and use it as the executable
953 @item -core @var{file}
955 @cindex @code{--core}
957 Use file @var{file} as a core dump to examine.
959 @item -pid @var{number}
960 @itemx -p @var{number}
963 Connect to process ID @var{number}, as with the @code{attach} command.
965 @item -command @var{file}
967 @cindex @code{--command}
969 Execute commands from file @var{file}. The contents of this file is
970 evaluated exactly as the @code{source} command would.
971 @xref{Command Files,, Command files}.
973 @item -eval-command @var{command}
974 @itemx -ex @var{command}
975 @cindex @code{--eval-command}
977 Execute a single @value{GDBN} command.
979 This option may be used multiple times to call multiple commands. It may
980 also be interleaved with @samp{-command} as required.
983 @value{GDBP} -ex 'target sim' -ex 'load' \
984 -x setbreakpoints -ex 'run' a.out
987 @item -directory @var{directory}
988 @itemx -d @var{directory}
989 @cindex @code{--directory}
991 Add @var{directory} to the path to search for source and script files.
995 @cindex @code{--readnow}
997 Read each symbol file's entire symbol table immediately, rather than
998 the default, which is to read it incrementally as it is needed.
999 This makes startup slower, but makes future operations faster.
1004 @subsection Choosing Modes
1006 You can run @value{GDBN} in various alternative modes---for example, in
1007 batch mode or quiet mode.
1014 Do not execute commands found in any initialization files. Normally,
1015 @value{GDBN} executes the commands in these files after all the command
1016 options and arguments have been processed. @xref{Command Files,,Command
1022 @cindex @code{--quiet}
1023 @cindex @code{--silent}
1025 ``Quiet''. Do not print the introductory and copyright messages. These
1026 messages are also suppressed in batch mode.
1029 @cindex @code{--batch}
1030 Run in batch mode. Exit with status @code{0} after processing all the
1031 command files specified with @samp{-x} (and all commands from
1032 initialization files, if not inhibited with @samp{-n}). Exit with
1033 nonzero status if an error occurs in executing the @value{GDBN} commands
1034 in the command files. Batch mode also disables pagination;
1035 @pxref{Screen Size} and acts as if @kbd{set confirm off} were in
1036 effect (@pxref{Messages/Warnings}).
1038 Batch mode may be useful for running @value{GDBN} as a filter, for
1039 example to download and run a program on another computer; in order to
1040 make this more useful, the message
1043 Program exited normally.
1047 (which is ordinarily issued whenever a program running under
1048 @value{GDBN} control terminates) is not issued when running in batch
1052 @cindex @code{--batch-silent}
1053 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1054 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1055 unaffected). This is much quieter than @samp{-silent} and would be useless
1056 for an interactive session.
1058 This is particularly useful when using targets that give @samp{Loading section}
1059 messages, for example.
1061 Note that targets that give their output via @value{GDBN}, as opposed to
1062 writing directly to @code{stdout}, will also be made silent.
1064 @item -return-child-result
1065 @cindex @code{--return-child-result}
1066 The return code from @value{GDBN} will be the return code from the child
1067 process (the process being debugged), with the following exceptions:
1071 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1072 internal error. In this case the exit code is the same as it would have been
1073 without @samp{-return-child-result}.
1075 The user quits with an explicit value. E.g., @samp{quit 1}.
1077 The child process never runs, or is not allowed to terminate, in which case
1078 the exit code will be -1.
1081 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1082 when @value{GDBN} is being used as a remote program loader or simulator
1087 @cindex @code{--nowindows}
1089 ``No windows''. If @value{GDBN} comes with a graphical user interface
1090 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1091 interface. If no GUI is available, this option has no effect.
1095 @cindex @code{--windows}
1097 If @value{GDBN} includes a GUI, then this option requires it to be
1100 @item -cd @var{directory}
1102 Run @value{GDBN} using @var{directory} as its working directory,
1103 instead of the current directory.
1107 @cindex @code{--fullname}
1109 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1110 subprocess. It tells @value{GDBN} to output the full file name and line
1111 number in a standard, recognizable fashion each time a stack frame is
1112 displayed (which includes each time your program stops). This
1113 recognizable format looks like two @samp{\032} characters, followed by
1114 the file name, line number and character position separated by colons,
1115 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1116 @samp{\032} characters as a signal to display the source code for the
1120 @cindex @code{--epoch}
1121 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1122 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1123 routines so as to allow Epoch to display values of expressions in a
1126 @item -annotate @var{level}
1127 @cindex @code{--annotate}
1128 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1129 effect is identical to using @samp{set annotate @var{level}}
1130 (@pxref{Annotations}). The annotation @var{level} controls how much
1131 information @value{GDBN} prints together with its prompt, values of
1132 expressions, source lines, and other types of output. Level 0 is the
1133 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1134 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1135 that control @value{GDBN}, and level 2 has been deprecated.
1137 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1141 @cindex @code{--args}
1142 Change interpretation of command line so that arguments following the
1143 executable file are passed as command line arguments to the inferior.
1144 This option stops option processing.
1146 @item -baud @var{bps}
1148 @cindex @code{--baud}
1150 Set the line speed (baud rate or bits per second) of any serial
1151 interface used by @value{GDBN} for remote debugging.
1153 @item -l @var{timeout}
1155 Set the timeout (in seconds) of any communication used by @value{GDBN}
1156 for remote debugging.
1158 @item -tty @var{device}
1159 @itemx -t @var{device}
1160 @cindex @code{--tty}
1162 Run using @var{device} for your program's standard input and output.
1163 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1165 @c resolve the situation of these eventually
1167 @cindex @code{--tui}
1168 Activate the @dfn{Text User Interface} when starting. The Text User
1169 Interface manages several text windows on the terminal, showing
1170 source, assembly, registers and @value{GDBN} command outputs
1171 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1172 Text User Interface can be enabled by invoking the program
1173 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1174 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1177 @c @cindex @code{--xdb}
1178 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1179 @c For information, see the file @file{xdb_trans.html}, which is usually
1180 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1183 @item -interpreter @var{interp}
1184 @cindex @code{--interpreter}
1185 Use the interpreter @var{interp} for interface with the controlling
1186 program or device. This option is meant to be set by programs which
1187 communicate with @value{GDBN} using it as a back end.
1188 @xref{Interpreters, , Command Interpreters}.
1190 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1191 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1192 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1193 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1194 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1195 @sc{gdb/mi} interfaces are no longer supported.
1198 @cindex @code{--write}
1199 Open the executable and core files for both reading and writing. This
1200 is equivalent to the @samp{set write on} command inside @value{GDBN}
1204 @cindex @code{--statistics}
1205 This option causes @value{GDBN} to print statistics about time and
1206 memory usage after it completes each command and returns to the prompt.
1209 @cindex @code{--version}
1210 This option causes @value{GDBN} to print its version number and
1211 no-warranty blurb, and exit.
1216 @subsection What @value{GDBN} Does During Startup
1217 @cindex @value{GDBN} startup
1219 Here's the description of what @value{GDBN} does during session startup:
1223 Sets up the command interpreter as specified by the command line
1224 (@pxref{Mode Options, interpreter}).
1228 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1229 used when building @value{GDBN}; @pxref{System-wide configuration,
1230 ,System-wide configuration and settings}) and executes all the commands in
1234 Reads the init file (if any) in your home directory@footnote{On
1235 DOS/Windows systems, the home directory is the one pointed to by the
1236 @code{HOME} environment variable.} and executes all the commands in
1240 Processes command line options and operands.
1243 Reads and executes the commands from init file (if any) in the current
1244 working directory. This is only done if the current directory is
1245 different from your home directory. Thus, you can have more than one
1246 init file, one generic in your home directory, and another, specific
1247 to the program you are debugging, in the directory where you invoke
1251 Reads command files specified by the @samp{-x} option. @xref{Command
1252 Files}, for more details about @value{GDBN} command files.
1255 Reads the command history recorded in the @dfn{history file}.
1256 @xref{Command History}, for more details about the command history and the
1257 files where @value{GDBN} records it.
1260 Init files use the same syntax as @dfn{command files} (@pxref{Command
1261 Files}) and are processed by @value{GDBN} in the same way. The init
1262 file in your home directory can set options (such as @samp{set
1263 complaints}) that affect subsequent processing of command line options
1264 and operands. Init files are not executed if you use the @samp{-nx}
1265 option (@pxref{Mode Options, ,Choosing Modes}).
1267 To display the list of init files loaded by gdb at startup, you
1268 can use @kbd{gdb --help}.
1270 @cindex init file name
1271 @cindex @file{.gdbinit}
1272 @cindex @file{gdb.ini}
1273 The @value{GDBN} init files are normally called @file{.gdbinit}.
1274 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1275 the limitations of file names imposed by DOS filesystems. The Windows
1276 ports of @value{GDBN} use the standard name, but if they find a
1277 @file{gdb.ini} file, they warn you about that and suggest to rename
1278 the file to the standard name.
1282 @section Quitting @value{GDBN}
1283 @cindex exiting @value{GDBN}
1284 @cindex leaving @value{GDBN}
1287 @kindex quit @r{[}@var{expression}@r{]}
1288 @kindex q @r{(@code{quit})}
1289 @item quit @r{[}@var{expression}@r{]}
1291 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1292 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1293 do not supply @var{expression}, @value{GDBN} will terminate normally;
1294 otherwise it will terminate using the result of @var{expression} as the
1299 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1300 terminates the action of any @value{GDBN} command that is in progress and
1301 returns to @value{GDBN} command level. It is safe to type the interrupt
1302 character at any time because @value{GDBN} does not allow it to take effect
1303 until a time when it is safe.
1305 If you have been using @value{GDBN} to control an attached process or
1306 device, you can release it with the @code{detach} command
1307 (@pxref{Attach, ,Debugging an Already-running Process}).
1309 @node Shell Commands
1310 @section Shell Commands
1312 If you need to execute occasional shell commands during your
1313 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1314 just use the @code{shell} command.
1318 @cindex shell escape
1319 @item shell @var{command string}
1320 Invoke a standard shell to execute @var{command string}.
1321 If it exists, the environment variable @code{SHELL} determines which
1322 shell to run. Otherwise @value{GDBN} uses the default shell
1323 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1326 The utility @code{make} is often needed in development environments.
1327 You do not have to use the @code{shell} command for this purpose in
1332 @cindex calling make
1333 @item make @var{make-args}
1334 Execute the @code{make} program with the specified
1335 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1338 @node Logging Output
1339 @section Logging Output
1340 @cindex logging @value{GDBN} output
1341 @cindex save @value{GDBN} output to a file
1343 You may want to save the output of @value{GDBN} commands to a file.
1344 There are several commands to control @value{GDBN}'s logging.
1348 @item set logging on
1350 @item set logging off
1352 @cindex logging file name
1353 @item set logging file @var{file}
1354 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1355 @item set logging overwrite [on|off]
1356 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1357 you want @code{set logging on} to overwrite the logfile instead.
1358 @item set logging redirect [on|off]
1359 By default, @value{GDBN} output will go to both the terminal and the logfile.
1360 Set @code{redirect} if you want output to go only to the log file.
1361 @kindex show logging
1363 Show the current values of the logging settings.
1367 @chapter @value{GDBN} Commands
1369 You can abbreviate a @value{GDBN} command to the first few letters of the command
1370 name, if that abbreviation is unambiguous; and you can repeat certain
1371 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1372 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1373 show you the alternatives available, if there is more than one possibility).
1376 * Command Syntax:: How to give commands to @value{GDBN}
1377 * Completion:: Command completion
1378 * Help:: How to ask @value{GDBN} for help
1381 @node Command Syntax
1382 @section Command Syntax
1384 A @value{GDBN} command is a single line of input. There is no limit on
1385 how long it can be. It starts with a command name, which is followed by
1386 arguments whose meaning depends on the command name. For example, the
1387 command @code{step} accepts an argument which is the number of times to
1388 step, as in @samp{step 5}. You can also use the @code{step} command
1389 with no arguments. Some commands do not allow any arguments.
1391 @cindex abbreviation
1392 @value{GDBN} command names may always be truncated if that abbreviation is
1393 unambiguous. Other possible command abbreviations are listed in the
1394 documentation for individual commands. In some cases, even ambiguous
1395 abbreviations are allowed; for example, @code{s} is specially defined as
1396 equivalent to @code{step} even though there are other commands whose
1397 names start with @code{s}. You can test abbreviations by using them as
1398 arguments to the @code{help} command.
1400 @cindex repeating commands
1401 @kindex RET @r{(repeat last command)}
1402 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1403 repeat the previous command. Certain commands (for example, @code{run})
1404 will not repeat this way; these are commands whose unintentional
1405 repetition might cause trouble and which you are unlikely to want to
1406 repeat. User-defined commands can disable this feature; see
1407 @ref{Define, dont-repeat}.
1409 The @code{list} and @code{x} commands, when you repeat them with
1410 @key{RET}, construct new arguments rather than repeating
1411 exactly as typed. This permits easy scanning of source or memory.
1413 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1414 output, in a way similar to the common utility @code{more}
1415 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1416 @key{RET} too many in this situation, @value{GDBN} disables command
1417 repetition after any command that generates this sort of display.
1419 @kindex # @r{(a comment)}
1421 Any text from a @kbd{#} to the end of the line is a comment; it does
1422 nothing. This is useful mainly in command files (@pxref{Command
1423 Files,,Command Files}).
1425 @cindex repeating command sequences
1426 @kindex Ctrl-o @r{(operate-and-get-next)}
1427 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1428 commands. This command accepts the current line, like @key{RET}, and
1429 then fetches the next line relative to the current line from the history
1433 @section Command Completion
1436 @cindex word completion
1437 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1438 only one possibility; it can also show you what the valid possibilities
1439 are for the next word in a command, at any time. This works for @value{GDBN}
1440 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1442 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1443 of a word. If there is only one possibility, @value{GDBN} fills in the
1444 word, and waits for you to finish the command (or press @key{RET} to
1445 enter it). For example, if you type
1447 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1448 @c complete accuracy in these examples; space introduced for clarity.
1449 @c If texinfo enhancements make it unnecessary, it would be nice to
1450 @c replace " @key" by "@key" in the following...
1452 (@value{GDBP}) info bre @key{TAB}
1456 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1457 the only @code{info} subcommand beginning with @samp{bre}:
1460 (@value{GDBP}) info breakpoints
1464 You can either press @key{RET} at this point, to run the @code{info
1465 breakpoints} command, or backspace and enter something else, if
1466 @samp{breakpoints} does not look like the command you expected. (If you
1467 were sure you wanted @code{info breakpoints} in the first place, you
1468 might as well just type @key{RET} immediately after @samp{info bre},
1469 to exploit command abbreviations rather than command completion).
1471 If there is more than one possibility for the next word when you press
1472 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1473 characters and try again, or just press @key{TAB} a second time;
1474 @value{GDBN} displays all the possible completions for that word. For
1475 example, you might want to set a breakpoint on a subroutine whose name
1476 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1477 just sounds the bell. Typing @key{TAB} again displays all the
1478 function names in your program that begin with those characters, for
1482 (@value{GDBP}) b make_ @key{TAB}
1483 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1484 make_a_section_from_file make_environ
1485 make_abs_section make_function_type
1486 make_blockvector make_pointer_type
1487 make_cleanup make_reference_type
1488 make_command make_symbol_completion_list
1489 (@value{GDBP}) b make_
1493 After displaying the available possibilities, @value{GDBN} copies your
1494 partial input (@samp{b make_} in the example) so you can finish the
1497 If you just want to see the list of alternatives in the first place, you
1498 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1499 means @kbd{@key{META} ?}. You can type this either by holding down a
1500 key designated as the @key{META} shift on your keyboard (if there is
1501 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1503 @cindex quotes in commands
1504 @cindex completion of quoted strings
1505 Sometimes the string you need, while logically a ``word'', may contain
1506 parentheses or other characters that @value{GDBN} normally excludes from
1507 its notion of a word. To permit word completion to work in this
1508 situation, you may enclose words in @code{'} (single quote marks) in
1509 @value{GDBN} commands.
1511 The most likely situation where you might need this is in typing the
1512 name of a C@t{++} function. This is because C@t{++} allows function
1513 overloading (multiple definitions of the same function, distinguished
1514 by argument type). For example, when you want to set a breakpoint you
1515 may need to distinguish whether you mean the version of @code{name}
1516 that takes an @code{int} parameter, @code{name(int)}, or the version
1517 that takes a @code{float} parameter, @code{name(float)}. To use the
1518 word-completion facilities in this situation, type a single quote
1519 @code{'} at the beginning of the function name. This alerts
1520 @value{GDBN} that it may need to consider more information than usual
1521 when you press @key{TAB} or @kbd{M-?} to request word completion:
1524 (@value{GDBP}) b 'bubble( @kbd{M-?}
1525 bubble(double,double) bubble(int,int)
1526 (@value{GDBP}) b 'bubble(
1529 In some cases, @value{GDBN} can tell that completing a name requires using
1530 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1531 completing as much as it can) if you do not type the quote in the first
1535 (@value{GDBP}) b bub @key{TAB}
1536 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1537 (@value{GDBP}) b 'bubble(
1541 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1542 you have not yet started typing the argument list when you ask for
1543 completion on an overloaded symbol.
1545 For more information about overloaded functions, see @ref{C Plus Plus
1546 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1547 overload-resolution off} to disable overload resolution;
1548 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1550 @cindex completion of structure field names
1551 @cindex structure field name completion
1552 @cindex completion of union field names
1553 @cindex union field name completion
1554 When completing in an expression which looks up a field in a
1555 structure, @value{GDBN} also tries@footnote{The completer can be
1556 confused by certain kinds of invalid expressions. Also, it only
1557 examines the static type of the expression, not the dynamic type.} to
1558 limit completions to the field names available in the type of the
1562 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1563 magic to_delete to_fputs to_put to_rewind
1564 to_data to_flush to_isatty to_read to_write
1568 This is because the @code{gdb_stdout} is a variable of the type
1569 @code{struct ui_file} that is defined in @value{GDBN} sources as
1576 ui_file_flush_ftype *to_flush;
1577 ui_file_write_ftype *to_write;
1578 ui_file_fputs_ftype *to_fputs;
1579 ui_file_read_ftype *to_read;
1580 ui_file_delete_ftype *to_delete;
1581 ui_file_isatty_ftype *to_isatty;
1582 ui_file_rewind_ftype *to_rewind;
1583 ui_file_put_ftype *to_put;
1590 @section Getting Help
1591 @cindex online documentation
1594 You can always ask @value{GDBN} itself for information on its commands,
1595 using the command @code{help}.
1598 @kindex h @r{(@code{help})}
1601 You can use @code{help} (abbreviated @code{h}) with no arguments to
1602 display a short list of named classes of commands:
1606 List of classes of commands:
1608 aliases -- Aliases of other commands
1609 breakpoints -- Making program stop at certain points
1610 data -- Examining data
1611 files -- Specifying and examining files
1612 internals -- Maintenance commands
1613 obscure -- Obscure features
1614 running -- Running the program
1615 stack -- Examining the stack
1616 status -- Status inquiries
1617 support -- Support facilities
1618 tracepoints -- Tracing of program execution without
1619 stopping the program
1620 user-defined -- User-defined commands
1622 Type "help" followed by a class name for a list of
1623 commands in that class.
1624 Type "help" followed by command name for full
1626 Command name abbreviations are allowed if unambiguous.
1629 @c the above line break eliminates huge line overfull...
1631 @item help @var{class}
1632 Using one of the general help classes as an argument, you can get a
1633 list of the individual commands in that class. For example, here is the
1634 help display for the class @code{status}:
1637 (@value{GDBP}) help status
1642 @c Line break in "show" line falsifies real output, but needed
1643 @c to fit in smallbook page size.
1644 info -- Generic command for showing things
1645 about the program being debugged
1646 show -- Generic command for showing things
1649 Type "help" followed by command name for full
1651 Command name abbreviations are allowed if unambiguous.
1655 @item help @var{command}
1656 With a command name as @code{help} argument, @value{GDBN} displays a
1657 short paragraph on how to use that command.
1660 @item apropos @var{args}
1661 The @code{apropos} command searches through all of the @value{GDBN}
1662 commands, and their documentation, for the regular expression specified in
1663 @var{args}. It prints out all matches found. For example:
1674 set symbol-reloading -- Set dynamic symbol table reloading
1675 multiple times in one run
1676 show symbol-reloading -- Show dynamic symbol table reloading
1677 multiple times in one run
1682 @item complete @var{args}
1683 The @code{complete @var{args}} command lists all the possible completions
1684 for the beginning of a command. Use @var{args} to specify the beginning of the
1685 command you want completed. For example:
1691 @noindent results in:
1702 @noindent This is intended for use by @sc{gnu} Emacs.
1705 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1706 and @code{show} to inquire about the state of your program, or the state
1707 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1708 manual introduces each of them in the appropriate context. The listings
1709 under @code{info} and under @code{show} in the Index point to
1710 all the sub-commands. @xref{Index}.
1715 @kindex i @r{(@code{info})}
1717 This command (abbreviated @code{i}) is for describing the state of your
1718 program. For example, you can show the arguments passed to a function
1719 with @code{info args}, list the registers currently in use with @code{info
1720 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1721 You can get a complete list of the @code{info} sub-commands with
1722 @w{@code{help info}}.
1726 You can assign the result of an expression to an environment variable with
1727 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1728 @code{set prompt $}.
1732 In contrast to @code{info}, @code{show} is for describing the state of
1733 @value{GDBN} itself.
1734 You can change most of the things you can @code{show}, by using the
1735 related command @code{set}; for example, you can control what number
1736 system is used for displays with @code{set radix}, or simply inquire
1737 which is currently in use with @code{show radix}.
1740 To display all the settable parameters and their current
1741 values, you can use @code{show} with no arguments; you may also use
1742 @code{info set}. Both commands produce the same display.
1743 @c FIXME: "info set" violates the rule that "info" is for state of
1744 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1745 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1749 Here are three miscellaneous @code{show} subcommands, all of which are
1750 exceptional in lacking corresponding @code{set} commands:
1753 @kindex show version
1754 @cindex @value{GDBN} version number
1756 Show what version of @value{GDBN} is running. You should include this
1757 information in @value{GDBN} bug-reports. If multiple versions of
1758 @value{GDBN} are in use at your site, you may need to determine which
1759 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1760 commands are introduced, and old ones may wither away. Also, many
1761 system vendors ship variant versions of @value{GDBN}, and there are
1762 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1763 The version number is the same as the one announced when you start
1766 @kindex show copying
1767 @kindex info copying
1768 @cindex display @value{GDBN} copyright
1771 Display information about permission for copying @value{GDBN}.
1773 @kindex show warranty
1774 @kindex info warranty
1776 @itemx info warranty
1777 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1778 if your version of @value{GDBN} comes with one.
1783 @chapter Running Programs Under @value{GDBN}
1785 When you run a program under @value{GDBN}, you must first generate
1786 debugging information when you compile it.
1788 You may start @value{GDBN} with its arguments, if any, in an environment
1789 of your choice. If you are doing native debugging, you may redirect
1790 your program's input and output, debug an already running process, or
1791 kill a child process.
1794 * Compilation:: Compiling for debugging
1795 * Starting:: Starting your program
1796 * Arguments:: Your program's arguments
1797 * Environment:: Your program's environment
1799 * Working Directory:: Your program's working directory
1800 * Input/Output:: Your program's input and output
1801 * Attach:: Debugging an already-running process
1802 * Kill Process:: Killing the child process
1804 * Inferiors and Programs:: Debugging multiple inferiors and programs
1805 * Threads:: Debugging programs with multiple threads
1806 * Forks:: Debugging forks
1807 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1811 @section Compiling for Debugging
1813 In order to debug a program effectively, you need to generate
1814 debugging information when you compile it. This debugging information
1815 is stored in the object file; it describes the data type of each
1816 variable or function and the correspondence between source line numbers
1817 and addresses in the executable code.
1819 To request debugging information, specify the @samp{-g} option when you run
1822 Programs that are to be shipped to your customers are compiled with
1823 optimizations, using the @samp{-O} compiler option. However, some
1824 compilers are unable to handle the @samp{-g} and @samp{-O} options
1825 together. Using those compilers, you cannot generate optimized
1826 executables containing debugging information.
1828 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1829 without @samp{-O}, making it possible to debug optimized code. We
1830 recommend that you @emph{always} use @samp{-g} whenever you compile a
1831 program. You may think your program is correct, but there is no sense
1832 in pushing your luck. For more information, see @ref{Optimized Code}.
1834 Older versions of the @sc{gnu} C compiler permitted a variant option
1835 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1836 format; if your @sc{gnu} C compiler has this option, do not use it.
1838 @value{GDBN} knows about preprocessor macros and can show you their
1839 expansion (@pxref{Macros}). Most compilers do not include information
1840 about preprocessor macros in the debugging information if you specify
1841 the @option{-g} flag alone, because this information is rather large.
1842 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1843 provides macro information if you specify the options
1844 @option{-gdwarf-2} and @option{-g3}; the former option requests
1845 debugging information in the Dwarf 2 format, and the latter requests
1846 ``extra information''. In the future, we hope to find more compact
1847 ways to represent macro information, so that it can be included with
1852 @section Starting your Program
1858 @kindex r @r{(@code{run})}
1861 Use the @code{run} command to start your program under @value{GDBN}.
1862 You must first specify the program name (except on VxWorks) with an
1863 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1864 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1865 (@pxref{Files, ,Commands to Specify Files}).
1869 If you are running your program in an execution environment that
1870 supports processes, @code{run} creates an inferior process and makes
1871 that process run your program. In some environments without processes,
1872 @code{run} jumps to the start of your program. Other targets,
1873 like @samp{remote}, are always running. If you get an error
1874 message like this one:
1877 The "remote" target does not support "run".
1878 Try "help target" or "continue".
1882 then use @code{continue} to run your program. You may need @code{load}
1883 first (@pxref{load}).
1885 The execution of a program is affected by certain information it
1886 receives from its superior. @value{GDBN} provides ways to specify this
1887 information, which you must do @emph{before} starting your program. (You
1888 can change it after starting your program, but such changes only affect
1889 your program the next time you start it.) This information may be
1890 divided into four categories:
1893 @item The @emph{arguments.}
1894 Specify the arguments to give your program as the arguments of the
1895 @code{run} command. If a shell is available on your target, the shell
1896 is used to pass the arguments, so that you may use normal conventions
1897 (such as wildcard expansion or variable substitution) in describing
1899 In Unix systems, you can control which shell is used with the
1900 @code{SHELL} environment variable.
1901 @xref{Arguments, ,Your Program's Arguments}.
1903 @item The @emph{environment.}
1904 Your program normally inherits its environment from @value{GDBN}, but you can
1905 use the @value{GDBN} commands @code{set environment} and @code{unset
1906 environment} to change parts of the environment that affect
1907 your program. @xref{Environment, ,Your Program's Environment}.
1909 @item The @emph{working directory.}
1910 Your program inherits its working directory from @value{GDBN}. You can set
1911 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1912 @xref{Working Directory, ,Your Program's Working Directory}.
1914 @item The @emph{standard input and output.}
1915 Your program normally uses the same device for standard input and
1916 standard output as @value{GDBN} is using. You can redirect input and output
1917 in the @code{run} command line, or you can use the @code{tty} command to
1918 set a different device for your program.
1919 @xref{Input/Output, ,Your Program's Input and Output}.
1922 @emph{Warning:} While input and output redirection work, you cannot use
1923 pipes to pass the output of the program you are debugging to another
1924 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1928 When you issue the @code{run} command, your program begins to execute
1929 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1930 of how to arrange for your program to stop. Once your program has
1931 stopped, you may call functions in your program, using the @code{print}
1932 or @code{call} commands. @xref{Data, ,Examining Data}.
1934 If the modification time of your symbol file has changed since the last
1935 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1936 table, and reads it again. When it does this, @value{GDBN} tries to retain
1937 your current breakpoints.
1942 @cindex run to main procedure
1943 The name of the main procedure can vary from language to language.
1944 With C or C@t{++}, the main procedure name is always @code{main}, but
1945 other languages such as Ada do not require a specific name for their
1946 main procedure. The debugger provides a convenient way to start the
1947 execution of the program and to stop at the beginning of the main
1948 procedure, depending on the language used.
1950 The @samp{start} command does the equivalent of setting a temporary
1951 breakpoint at the beginning of the main procedure and then invoking
1952 the @samp{run} command.
1954 @cindex elaboration phase
1955 Some programs contain an @dfn{elaboration} phase where some startup code is
1956 executed before the main procedure is called. This depends on the
1957 languages used to write your program. In C@t{++}, for instance,
1958 constructors for static and global objects are executed before
1959 @code{main} is called. It is therefore possible that the debugger stops
1960 before reaching the main procedure. However, the temporary breakpoint
1961 will remain to halt execution.
1963 Specify the arguments to give to your program as arguments to the
1964 @samp{start} command. These arguments will be given verbatim to the
1965 underlying @samp{run} command. Note that the same arguments will be
1966 reused if no argument is provided during subsequent calls to
1967 @samp{start} or @samp{run}.
1969 It is sometimes necessary to debug the program during elaboration. In
1970 these cases, using the @code{start} command would stop the execution of
1971 your program too late, as the program would have already completed the
1972 elaboration phase. Under these circumstances, insert breakpoints in your
1973 elaboration code before running your program.
1975 @kindex set exec-wrapper
1976 @item set exec-wrapper @var{wrapper}
1977 @itemx show exec-wrapper
1978 @itemx unset exec-wrapper
1979 When @samp{exec-wrapper} is set, the specified wrapper is used to
1980 launch programs for debugging. @value{GDBN} starts your program
1981 with a shell command of the form @kbd{exec @var{wrapper}
1982 @var{program}}. Quoting is added to @var{program} and its
1983 arguments, but not to @var{wrapper}, so you should add quotes if
1984 appropriate for your shell. The wrapper runs until it executes
1985 your program, and then @value{GDBN} takes control.
1987 You can use any program that eventually calls @code{execve} with
1988 its arguments as a wrapper. Several standard Unix utilities do
1989 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1990 with @code{exec "$@@"} will also work.
1992 For example, you can use @code{env} to pass an environment variable to
1993 the debugged program, without setting the variable in your shell's
1997 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2001 This command is available when debugging locally on most targets, excluding
2002 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2004 @kindex set disable-randomization
2005 @item set disable-randomization
2006 @itemx set disable-randomization on
2007 This option (enabled by default in @value{GDBN}) will turn off the native
2008 randomization of the virtual address space of the started program. This option
2009 is useful for multiple debugging sessions to make the execution better
2010 reproducible and memory addresses reusable across debugging sessions.
2012 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2016 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2019 @item set disable-randomization off
2020 Leave the behavior of the started executable unchanged. Some bugs rear their
2021 ugly heads only when the program is loaded at certain addresses. If your bug
2022 disappears when you run the program under @value{GDBN}, that might be because
2023 @value{GDBN} by default disables the address randomization on platforms, such
2024 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2025 disable-randomization off} to try to reproduce such elusive bugs.
2027 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2028 It protects the programs against some kinds of security attacks. In these
2029 cases the attacker needs to know the exact location of a concrete executable
2030 code. Randomizing its location makes it impossible to inject jumps misusing
2031 a code at its expected addresses.
2033 Prelinking shared libraries provides a startup performance advantage but it
2034 makes addresses in these libraries predictable for privileged processes by
2035 having just unprivileged access at the target system. Reading the shared
2036 library binary gives enough information for assembling the malicious code
2037 misusing it. Still even a prelinked shared library can get loaded at a new
2038 random address just requiring the regular relocation process during the
2039 startup. Shared libraries not already prelinked are always loaded at
2040 a randomly chosen address.
2042 Position independent executables (PIE) contain position independent code
2043 similar to the shared libraries and therefore such executables get loaded at
2044 a randomly chosen address upon startup. PIE executables always load even
2045 already prelinked shared libraries at a random address. You can build such
2046 executable using @command{gcc -fPIE -pie}.
2048 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2049 (as long as the randomization is enabled).
2051 @item show disable-randomization
2052 Show the current setting of the explicit disable of the native randomization of
2053 the virtual address space of the started program.
2058 @section Your Program's Arguments
2060 @cindex arguments (to your program)
2061 The arguments to your program can be specified by the arguments of the
2063 They are passed to a shell, which expands wildcard characters and
2064 performs redirection of I/O, and thence to your program. Your
2065 @code{SHELL} environment variable (if it exists) specifies what shell
2066 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2067 the default shell (@file{/bin/sh} on Unix).
2069 On non-Unix systems, the program is usually invoked directly by
2070 @value{GDBN}, which emulates I/O redirection via the appropriate system
2071 calls, and the wildcard characters are expanded by the startup code of
2072 the program, not by the shell.
2074 @code{run} with no arguments uses the same arguments used by the previous
2075 @code{run}, or those set by the @code{set args} command.
2080 Specify the arguments to be used the next time your program is run. If
2081 @code{set args} has no arguments, @code{run} executes your program
2082 with no arguments. Once you have run your program with arguments,
2083 using @code{set args} before the next @code{run} is the only way to run
2084 it again without arguments.
2088 Show the arguments to give your program when it is started.
2092 @section Your Program's Environment
2094 @cindex environment (of your program)
2095 The @dfn{environment} consists of a set of environment variables and
2096 their values. Environment variables conventionally record such things as
2097 your user name, your home directory, your terminal type, and your search
2098 path for programs to run. Usually you set up environment variables with
2099 the shell and they are inherited by all the other programs you run. When
2100 debugging, it can be useful to try running your program with a modified
2101 environment without having to start @value{GDBN} over again.
2105 @item path @var{directory}
2106 Add @var{directory} to the front of the @code{PATH} environment variable
2107 (the search path for executables) that will be passed to your program.
2108 The value of @code{PATH} used by @value{GDBN} does not change.
2109 You may specify several directory names, separated by whitespace or by a
2110 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2111 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2112 is moved to the front, so it is searched sooner.
2114 You can use the string @samp{$cwd} to refer to whatever is the current
2115 working directory at the time @value{GDBN} searches the path. If you
2116 use @samp{.} instead, it refers to the directory where you executed the
2117 @code{path} command. @value{GDBN} replaces @samp{.} in the
2118 @var{directory} argument (with the current path) before adding
2119 @var{directory} to the search path.
2120 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2121 @c document that, since repeating it would be a no-op.
2125 Display the list of search paths for executables (the @code{PATH}
2126 environment variable).
2128 @kindex show environment
2129 @item show environment @r{[}@var{varname}@r{]}
2130 Print the value of environment variable @var{varname} to be given to
2131 your program when it starts. If you do not supply @var{varname},
2132 print the names and values of all environment variables to be given to
2133 your program. You can abbreviate @code{environment} as @code{env}.
2135 @kindex set environment
2136 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2137 Set environment variable @var{varname} to @var{value}. The value
2138 changes for your program only, not for @value{GDBN} itself. @var{value} may
2139 be any string; the values of environment variables are just strings, and
2140 any interpretation is supplied by your program itself. The @var{value}
2141 parameter is optional; if it is eliminated, the variable is set to a
2143 @c "any string" here does not include leading, trailing
2144 @c blanks. Gnu asks: does anyone care?
2146 For example, this command:
2153 tells the debugged program, when subsequently run, that its user is named
2154 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2155 are not actually required.)
2157 @kindex unset environment
2158 @item unset environment @var{varname}
2159 Remove variable @var{varname} from the environment to be passed to your
2160 program. This is different from @samp{set env @var{varname} =};
2161 @code{unset environment} removes the variable from the environment,
2162 rather than assigning it an empty value.
2165 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2167 by your @code{SHELL} environment variable if it exists (or
2168 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2169 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2170 @file{.bashrc} for BASH---any variables you set in that file affect
2171 your program. You may wish to move setting of environment variables to
2172 files that are only run when you sign on, such as @file{.login} or
2175 @node Working Directory
2176 @section Your Program's Working Directory
2178 @cindex working directory (of your program)
2179 Each time you start your program with @code{run}, it inherits its
2180 working directory from the current working directory of @value{GDBN}.
2181 The @value{GDBN} working directory is initially whatever it inherited
2182 from its parent process (typically the shell), but you can specify a new
2183 working directory in @value{GDBN} with the @code{cd} command.
2185 The @value{GDBN} working directory also serves as a default for the commands
2186 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2191 @cindex change working directory
2192 @item cd @var{directory}
2193 Set the @value{GDBN} working directory to @var{directory}.
2197 Print the @value{GDBN} working directory.
2200 It is generally impossible to find the current working directory of
2201 the process being debugged (since a program can change its directory
2202 during its run). If you work on a system where @value{GDBN} is
2203 configured with the @file{/proc} support, you can use the @code{info
2204 proc} command (@pxref{SVR4 Process Information}) to find out the
2205 current working directory of the debuggee.
2208 @section Your Program's Input and Output
2213 By default, the program you run under @value{GDBN} does input and output to
2214 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2215 to its own terminal modes to interact with you, but it records the terminal
2216 modes your program was using and switches back to them when you continue
2217 running your program.
2220 @kindex info terminal
2222 Displays information recorded by @value{GDBN} about the terminal modes your
2226 You can redirect your program's input and/or output using shell
2227 redirection with the @code{run} command. For example,
2234 starts your program, diverting its output to the file @file{outfile}.
2237 @cindex controlling terminal
2238 Another way to specify where your program should do input and output is
2239 with the @code{tty} command. This command accepts a file name as
2240 argument, and causes this file to be the default for future @code{run}
2241 commands. It also resets the controlling terminal for the child
2242 process, for future @code{run} commands. For example,
2249 directs that processes started with subsequent @code{run} commands
2250 default to do input and output on the terminal @file{/dev/ttyb} and have
2251 that as their controlling terminal.
2253 An explicit redirection in @code{run} overrides the @code{tty} command's
2254 effect on the input/output device, but not its effect on the controlling
2257 When you use the @code{tty} command or redirect input in the @code{run}
2258 command, only the input @emph{for your program} is affected. The input
2259 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2260 for @code{set inferior-tty}.
2262 @cindex inferior tty
2263 @cindex set inferior controlling terminal
2264 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2265 display the name of the terminal that will be used for future runs of your
2269 @item set inferior-tty /dev/ttyb
2270 @kindex set inferior-tty
2271 Set the tty for the program being debugged to /dev/ttyb.
2273 @item show inferior-tty
2274 @kindex show inferior-tty
2275 Show the current tty for the program being debugged.
2279 @section Debugging an Already-running Process
2284 @item attach @var{process-id}
2285 This command attaches to a running process---one that was started
2286 outside @value{GDBN}. (@code{info files} shows your active
2287 targets.) The command takes as argument a process ID. The usual way to
2288 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2289 or with the @samp{jobs -l} shell command.
2291 @code{attach} does not repeat if you press @key{RET} a second time after
2292 executing the command.
2295 To use @code{attach}, your program must be running in an environment
2296 which supports processes; for example, @code{attach} does not work for
2297 programs on bare-board targets that lack an operating system. You must
2298 also have permission to send the process a signal.
2300 When you use @code{attach}, the debugger finds the program running in
2301 the process first by looking in the current working directory, then (if
2302 the program is not found) by using the source file search path
2303 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2304 the @code{file} command to load the program. @xref{Files, ,Commands to
2307 The first thing @value{GDBN} does after arranging to debug the specified
2308 process is to stop it. You can examine and modify an attached process
2309 with all the @value{GDBN} commands that are ordinarily available when
2310 you start processes with @code{run}. You can insert breakpoints; you
2311 can step and continue; you can modify storage. If you would rather the
2312 process continue running, you may use the @code{continue} command after
2313 attaching @value{GDBN} to the process.
2318 When you have finished debugging the attached process, you can use the
2319 @code{detach} command to release it from @value{GDBN} control. Detaching
2320 the process continues its execution. After the @code{detach} command,
2321 that process and @value{GDBN} become completely independent once more, and you
2322 are ready to @code{attach} another process or start one with @code{run}.
2323 @code{detach} does not repeat if you press @key{RET} again after
2324 executing the command.
2327 If you exit @value{GDBN} while you have an attached process, you detach
2328 that process. If you use the @code{run} command, you kill that process.
2329 By default, @value{GDBN} asks for confirmation if you try to do either of these
2330 things; you can control whether or not you need to confirm by using the
2331 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2335 @section Killing the Child Process
2340 Kill the child process in which your program is running under @value{GDBN}.
2343 This command is useful if you wish to debug a core dump instead of a
2344 running process. @value{GDBN} ignores any core dump file while your program
2347 On some operating systems, a program cannot be executed outside @value{GDBN}
2348 while you have breakpoints set on it inside @value{GDBN}. You can use the
2349 @code{kill} command in this situation to permit running your program
2350 outside the debugger.
2352 The @code{kill} command is also useful if you wish to recompile and
2353 relink your program, since on many systems it is impossible to modify an
2354 executable file while it is running in a process. In this case, when you
2355 next type @code{run}, @value{GDBN} notices that the file has changed, and
2356 reads the symbol table again (while trying to preserve your current
2357 breakpoint settings).
2359 @node Inferiors and Programs
2360 @section Debugging Multiple Inferiors and Programs
2362 @value{GDBN} lets you run and debug multiple programs in a single
2363 session. In addition, @value{GDBN} on some systems may let you run
2364 several programs simultaneously (otherwise you have to exit from one
2365 before starting another). In the most general case, you can have
2366 multiple threads of execution in each of multiple processes, launched
2367 from multiple executables.
2370 @value{GDBN} represents the state of each program execution with an
2371 object called an @dfn{inferior}. An inferior typically corresponds to
2372 a process, but is more general and applies also to targets that do not
2373 have processes. Inferiors may be created before a process runs, and
2374 may be retained after a process exits. Inferiors have unique
2375 identifiers that are different from process ids. Usually each
2376 inferior will also have its own distinct address space, although some
2377 embedded targets may have several inferiors running in different parts
2378 of a single address space. Each inferior may in turn have multiple
2379 threads running in it.
2381 To find out what inferiors exist at any moment, use @w{@code{info
2385 @kindex info inferiors
2386 @item info inferiors
2387 Print a list of all inferiors currently being managed by @value{GDBN}.
2389 @value{GDBN} displays for each inferior (in this order):
2393 the inferior number assigned by @value{GDBN}
2396 the target system's inferior identifier
2399 the name of the executable the inferior is running.
2404 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2405 indicates the current inferior.
2409 @c end table here to get a little more width for example
2412 (@value{GDBP}) info inferiors
2413 Num Description Executable
2414 2 process 2307 hello
2415 * 1 process 3401 goodbye
2418 To switch focus between inferiors, use the @code{inferior} command:
2421 @kindex inferior @var{infno}
2422 @item inferior @var{infno}
2423 Make inferior number @var{infno} the current inferior. The argument
2424 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2425 in the first field of the @samp{info inferiors} display.
2429 You can get multiple executables into a debugging session via the
2430 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2431 systems @value{GDBN} can add inferiors to the debug session
2432 automatically by following calls to @code{fork} and @code{exec}. To
2433 remove inferiors from the debugging session use the
2434 @w{@code{remove-inferior}} command.
2437 @kindex add-inferior
2438 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2439 Adds @var{n} inferiors to be run using @var{executable} as the
2440 executable. @var{n} defaults to 1. If no executable is specified,
2441 the inferiors begins empty, with no program. You can still assign or
2442 change the program assigned to the inferior at any time by using the
2443 @code{file} command with the executable name as its argument.
2445 @kindex clone-inferior
2446 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2447 Adds @var{n} inferiors ready to execute the same program as inferior
2448 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2449 number of the current inferior. This is a convenient command when you
2450 want to run another instance of the inferior you are debugging.
2453 (@value{GDBP}) info inferiors
2454 Num Description Executable
2455 * 1 process 29964 helloworld
2456 (@value{GDBP}) clone-inferior
2459 (@value{GDBP}) info inferiors
2460 Num Description Executable
2462 * 1 process 29964 helloworld
2465 You can now simply switch focus to inferior 2 and run it.
2467 @kindex remove-inferior
2468 @item remove-inferior @var{infno}
2469 Removes the inferior @var{infno}. It is not possible to remove an
2470 inferior that is running with this command. For those, use the
2471 @code{kill} or @code{detach} command first.
2475 To quit debugging one of the running inferiors that is not the current
2476 inferior, you can either detach from it by using the @w{@code{detach
2477 inferior}} command (allowing it to run independently), or kill it
2478 using the @w{@code{kill inferior}} command:
2481 @kindex detach inferior @var{infno}
2482 @item detach inferior @var{infno}
2483 Detach from the inferior identified by @value{GDBN} inferior number
2484 @var{infno}. Note that the inferior's entry still stays on the list
2485 of inferiors shown by @code{info inferiors}, but its Description will
2488 @kindex kill inferior @var{infno}
2489 @item kill inferior @var{infno}
2490 Kill the inferior identified by @value{GDBN} inferior number
2491 @var{infno}. Note that the inferior's entry still stays on the list
2492 of inferiors shown by @code{info inferiors}, but its Description will
2496 After the successful completion of a command such as @code{detach},
2497 @code{detach inferior}, @code{kill} or @code{kill inferior}, or after
2498 a normal process exit, the inferior is still valid and listed with
2499 @code{info inferiors}, ready to be restarted.
2502 To be notified when inferiors are started or exit under @value{GDBN}'s
2503 control use @w{@code{set print inferior-events}}:
2506 @kindex set print inferior-events
2507 @cindex print messages on inferior start and exit
2508 @item set print inferior-events
2509 @itemx set print inferior-events on
2510 @itemx set print inferior-events off
2511 The @code{set print inferior-events} command allows you to enable or
2512 disable printing of messages when @value{GDBN} notices that new
2513 inferiors have started or that inferiors have exited or have been
2514 detached. By default, these messages will not be printed.
2516 @kindex show print inferior-events
2517 @item show print inferior-events
2518 Show whether messages will be printed when @value{GDBN} detects that
2519 inferiors have started, exited or have been detached.
2522 Many commands will work the same with multiple programs as with a
2523 single program: e.g., @code{print myglobal} will simply display the
2524 value of @code{myglobal} in the current inferior.
2527 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2528 get more info about the relationship of inferiors, programs, address
2529 spaces in a debug session. You can do that with the @w{@code{maint
2530 info program-spaces}} command.
2533 @kindex maint info program-spaces
2534 @item maint info program-spaces
2535 Print a list of all program spaces currently being managed by
2538 @value{GDBN} displays for each program space (in this order):
2542 the program space number assigned by @value{GDBN}
2545 the name of the executable loaded into the program space, with e.g.,
2546 the @code{file} command.
2551 An asterisk @samp{*} preceding the @value{GDBN} program space number
2552 indicates the current program space.
2554 In addition, below each program space line, @value{GDBN} prints extra
2555 information that isn't suitable to display in tabular form. For
2556 example, the list of inferiors bound to the program space.
2559 (@value{GDBP}) maint info program-spaces
2562 Bound inferiors: ID 1 (process 21561)
2566 Here we can see that no inferior is running the program @code{hello},
2567 while @code{process 21561} is running the program @code{goodbye}. On
2568 some targets, it is possible that multiple inferiors are bound to the
2569 same program space. The most common example is that of debugging both
2570 the parent and child processes of a @code{vfork} call. For example,
2573 (@value{GDBP}) maint info program-spaces
2576 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2579 Here, both inferior 2 and inferior 1 are running in the same program
2580 space as a result of inferior 1 having executed a @code{vfork} call.
2584 @section Debugging Programs with Multiple Threads
2586 @cindex threads of execution
2587 @cindex multiple threads
2588 @cindex switching threads
2589 In some operating systems, such as HP-UX and Solaris, a single program
2590 may have more than one @dfn{thread} of execution. The precise semantics
2591 of threads differ from one operating system to another, but in general
2592 the threads of a single program are akin to multiple processes---except
2593 that they share one address space (that is, they can all examine and
2594 modify the same variables). On the other hand, each thread has its own
2595 registers and execution stack, and perhaps private memory.
2597 @value{GDBN} provides these facilities for debugging multi-thread
2601 @item automatic notification of new threads
2602 @item @samp{thread @var{threadno}}, a command to switch among threads
2603 @item @samp{info threads}, a command to inquire about existing threads
2604 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2605 a command to apply a command to a list of threads
2606 @item thread-specific breakpoints
2607 @item @samp{set print thread-events}, which controls printing of
2608 messages on thread start and exit.
2609 @item @samp{set libthread-db-search-path @var{path}}, which lets
2610 the user specify which @code{libthread_db} to use if the default choice
2611 isn't compatible with the program.
2615 @emph{Warning:} These facilities are not yet available on every
2616 @value{GDBN} configuration where the operating system supports threads.
2617 If your @value{GDBN} does not support threads, these commands have no
2618 effect. For example, a system without thread support shows no output
2619 from @samp{info threads}, and always rejects the @code{thread} command,
2623 (@value{GDBP}) info threads
2624 (@value{GDBP}) thread 1
2625 Thread ID 1 not known. Use the "info threads" command to
2626 see the IDs of currently known threads.
2628 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2629 @c doesn't support threads"?
2632 @cindex focus of debugging
2633 @cindex current thread
2634 The @value{GDBN} thread debugging facility allows you to observe all
2635 threads while your program runs---but whenever @value{GDBN} takes
2636 control, one thread in particular is always the focus of debugging.
2637 This thread is called the @dfn{current thread}. Debugging commands show
2638 program information from the perspective of the current thread.
2640 @cindex @code{New} @var{systag} message
2641 @cindex thread identifier (system)
2642 @c FIXME-implementors!! It would be more helpful if the [New...] message
2643 @c included GDB's numeric thread handle, so you could just go to that
2644 @c thread without first checking `info threads'.
2645 Whenever @value{GDBN} detects a new thread in your program, it displays
2646 the target system's identification for the thread with a message in the
2647 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2648 whose form varies depending on the particular system. For example, on
2649 @sc{gnu}/Linux, you might see
2652 [New Thread 46912507313328 (LWP 25582)]
2656 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2657 the @var{systag} is simply something like @samp{process 368}, with no
2660 @c FIXME!! (1) Does the [New...] message appear even for the very first
2661 @c thread of a program, or does it only appear for the
2662 @c second---i.e.@: when it becomes obvious we have a multithread
2664 @c (2) *Is* there necessarily a first thread always? Or do some
2665 @c multithread systems permit starting a program with multiple
2666 @c threads ab initio?
2668 @cindex thread number
2669 @cindex thread identifier (GDB)
2670 For debugging purposes, @value{GDBN} associates its own thread
2671 number---always a single integer---with each thread in your program.
2674 @kindex info threads
2676 Display a summary of all threads currently in your
2677 program. @value{GDBN} displays for each thread (in this order):
2681 the thread number assigned by @value{GDBN}
2684 the target system's thread identifier (@var{systag})
2687 the current stack frame summary for that thread
2691 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2692 indicates the current thread.
2696 @c end table here to get a little more width for example
2699 (@value{GDBP}) info threads
2700 3 process 35 thread 27 0x34e5 in sigpause ()
2701 2 process 35 thread 23 0x34e5 in sigpause ()
2702 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2708 @cindex debugging multithreaded programs (on HP-UX)
2709 @cindex thread identifier (GDB), on HP-UX
2710 For debugging purposes, @value{GDBN} associates its own thread
2711 number---a small integer assigned in thread-creation order---with each
2712 thread in your program.
2714 @cindex @code{New} @var{systag} message, on HP-UX
2715 @cindex thread identifier (system), on HP-UX
2716 @c FIXME-implementors!! It would be more helpful if the [New...] message
2717 @c included GDB's numeric thread handle, so you could just go to that
2718 @c thread without first checking `info threads'.
2719 Whenever @value{GDBN} detects a new thread in your program, it displays
2720 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2721 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2722 whose form varies depending on the particular system. For example, on
2726 [New thread 2 (system thread 26594)]
2730 when @value{GDBN} notices a new thread.
2733 @kindex info threads (HP-UX)
2735 Display a summary of all threads currently in your
2736 program. @value{GDBN} displays for each thread (in this order):
2739 @item the thread number assigned by @value{GDBN}
2741 @item the target system's thread identifier (@var{systag})
2743 @item the current stack frame summary for that thread
2747 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2748 indicates the current thread.
2752 @c end table here to get a little more width for example
2755 (@value{GDBP}) info threads
2756 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2758 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2759 from /usr/lib/libc.2
2760 1 system thread 27905 0x7b003498 in _brk () \@*
2761 from /usr/lib/libc.2
2764 On Solaris, you can display more information about user threads with a
2765 Solaris-specific command:
2768 @item maint info sol-threads
2769 @kindex maint info sol-threads
2770 @cindex thread info (Solaris)
2771 Display info on Solaris user threads.
2775 @kindex thread @var{threadno}
2776 @item thread @var{threadno}
2777 Make thread number @var{threadno} the current thread. The command
2778 argument @var{threadno} is the internal @value{GDBN} thread number, as
2779 shown in the first field of the @samp{info threads} display.
2780 @value{GDBN} responds by displaying the system identifier of the thread
2781 you selected, and its current stack frame summary:
2784 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2785 (@value{GDBP}) thread 2
2786 [Switching to process 35 thread 23]
2787 0x34e5 in sigpause ()
2791 As with the @samp{[New @dots{}]} message, the form of the text after
2792 @samp{Switching to} depends on your system's conventions for identifying
2795 @vindex $_thread@r{, convenience variable}
2796 The debugger convenience variable @samp{$_thread} contains the number
2797 of the current thread. You may find this useful in writing breakpoint
2798 conditional expressions, command scripts, and so forth. See
2799 @xref{Convenience Vars,, Convenience Variables}, for general
2800 information on convenience variables.
2802 @kindex thread apply
2803 @cindex apply command to several threads
2804 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2805 The @code{thread apply} command allows you to apply the named
2806 @var{command} to one or more threads. Specify the numbers of the
2807 threads that you want affected with the command argument
2808 @var{threadno}. It can be a single thread number, one of the numbers
2809 shown in the first field of the @samp{info threads} display; or it
2810 could be a range of thread numbers, as in @code{2-4}. To apply a
2811 command to all threads, type @kbd{thread apply all @var{command}}.
2813 @kindex set print thread-events
2814 @cindex print messages on thread start and exit
2815 @item set print thread-events
2816 @itemx set print thread-events on
2817 @itemx set print thread-events off
2818 The @code{set print thread-events} command allows you to enable or
2819 disable printing of messages when @value{GDBN} notices that new threads have
2820 started or that threads have exited. By default, these messages will
2821 be printed if detection of these events is supported by the target.
2822 Note that these messages cannot be disabled on all targets.
2824 @kindex show print thread-events
2825 @item show print thread-events
2826 Show whether messages will be printed when @value{GDBN} detects that threads
2827 have started and exited.
2830 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2831 more information about how @value{GDBN} behaves when you stop and start
2832 programs with multiple threads.
2834 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2835 watchpoints in programs with multiple threads.
2838 @kindex set libthread-db-search-path
2839 @cindex search path for @code{libthread_db}
2840 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2841 If this variable is set, @var{path} is a colon-separated list of
2842 directories @value{GDBN} will use to search for @code{libthread_db}.
2843 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2846 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2847 @code{libthread_db} library to obtain information about threads in the
2848 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2849 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2850 with default system shared library directories, and finally the directory
2851 from which @code{libpthread} was loaded in the inferior process.
2853 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2854 @value{GDBN} attempts to initialize it with the current inferior process.
2855 If this initialization fails (which could happen because of a version
2856 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2857 will unload @code{libthread_db}, and continue with the next directory.
2858 If none of @code{libthread_db} libraries initialize successfully,
2859 @value{GDBN} will issue a warning and thread debugging will be disabled.
2861 Setting @code{libthread-db-search-path} is currently implemented
2862 only on some platforms.
2864 @kindex show libthread-db-search-path
2865 @item show libthread-db-search-path
2866 Display current libthread_db search path.
2870 @section Debugging Forks
2872 @cindex fork, debugging programs which call
2873 @cindex multiple processes
2874 @cindex processes, multiple
2875 On most systems, @value{GDBN} has no special support for debugging
2876 programs which create additional processes using the @code{fork}
2877 function. When a program forks, @value{GDBN} will continue to debug the
2878 parent process and the child process will run unimpeded. If you have
2879 set a breakpoint in any code which the child then executes, the child
2880 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2881 will cause it to terminate.
2883 However, if you want to debug the child process there is a workaround
2884 which isn't too painful. Put a call to @code{sleep} in the code which
2885 the child process executes after the fork. It may be useful to sleep
2886 only if a certain environment variable is set, or a certain file exists,
2887 so that the delay need not occur when you don't want to run @value{GDBN}
2888 on the child. While the child is sleeping, use the @code{ps} program to
2889 get its process ID. Then tell @value{GDBN} (a new invocation of
2890 @value{GDBN} if you are also debugging the parent process) to attach to
2891 the child process (@pxref{Attach}). From that point on you can debug
2892 the child process just like any other process which you attached to.
2894 On some systems, @value{GDBN} provides support for debugging programs that
2895 create additional processes using the @code{fork} or @code{vfork} functions.
2896 Currently, the only platforms with this feature are HP-UX (11.x and later
2897 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2899 By default, when a program forks, @value{GDBN} will continue to debug
2900 the parent process and the child process will run unimpeded.
2902 If you want to follow the child process instead of the parent process,
2903 use the command @w{@code{set follow-fork-mode}}.
2906 @kindex set follow-fork-mode
2907 @item set follow-fork-mode @var{mode}
2908 Set the debugger response to a program call of @code{fork} or
2909 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2910 process. The @var{mode} argument can be:
2914 The original process is debugged after a fork. The child process runs
2915 unimpeded. This is the default.
2918 The new process is debugged after a fork. The parent process runs
2923 @kindex show follow-fork-mode
2924 @item show follow-fork-mode
2925 Display the current debugger response to a @code{fork} or @code{vfork} call.
2928 @cindex debugging multiple processes
2929 On Linux, if you want to debug both the parent and child processes, use the
2930 command @w{@code{set detach-on-fork}}.
2933 @kindex set detach-on-fork
2934 @item set detach-on-fork @var{mode}
2935 Tells gdb whether to detach one of the processes after a fork, or
2936 retain debugger control over them both.
2940 The child process (or parent process, depending on the value of
2941 @code{follow-fork-mode}) will be detached and allowed to run
2942 independently. This is the default.
2945 Both processes will be held under the control of @value{GDBN}.
2946 One process (child or parent, depending on the value of
2947 @code{follow-fork-mode}) is debugged as usual, while the other
2952 @kindex show detach-on-fork
2953 @item show detach-on-fork
2954 Show whether detach-on-fork mode is on/off.
2957 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2958 will retain control of all forked processes (including nested forks).
2959 You can list the forked processes under the control of @value{GDBN} by
2960 using the @w{@code{info inferiors}} command, and switch from one fork
2961 to another by using the @code{inferior} command (@pxref{Inferiors and
2962 Programs, ,Debugging Multiple Inferiors and Programs}).
2964 To quit debugging one of the forked processes, you can either detach
2965 from it by using the @w{@code{detach inferior}} command (allowing it
2966 to run independently), or kill it using the @w{@code{kill inferior}}
2967 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2970 If you ask to debug a child process and a @code{vfork} is followed by an
2971 @code{exec}, @value{GDBN} executes the new target up to the first
2972 breakpoint in the new target. If you have a breakpoint set on
2973 @code{main} in your original program, the breakpoint will also be set on
2974 the child process's @code{main}.
2976 On some systems, when a child process is spawned by @code{vfork}, you
2977 cannot debug the child or parent until an @code{exec} call completes.
2979 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2980 call executes, the new target restarts. To restart the parent
2981 process, use the @code{file} command with the parent executable name
2982 as its argument. By default, after an @code{exec} call executes,
2983 @value{GDBN} discards the symbols of the previous executable image.
2984 You can change this behaviour with the @w{@code{set follow-exec-mode}}
2988 @kindex set follow-exec-mode
2989 @item set follow-exec-mode @var{mode}
2991 Set debugger response to a program call of @code{exec}. An
2992 @code{exec} call replaces the program image of a process.
2994 @code{follow-exec-mode} can be:
2998 @value{GDBN} creates a new inferior and rebinds the process to this
2999 new inferior. The program the process was running before the
3000 @code{exec} call can be restarted afterwards by restarting the
3006 (@value{GDBP}) info inferiors
3008 Id Description Executable
3011 process 12020 is executing new program: prog2
3012 Program exited normally.
3013 (@value{GDBP}) info inferiors
3014 Id Description Executable
3020 @value{GDBN} keeps the process bound to the same inferior. The new
3021 executable image replaces the previous executable loaded in the
3022 inferior. Restarting the inferior after the @code{exec} call, with
3023 e.g., the @code{run} command, restarts the executable the process was
3024 running after the @code{exec} call. This is the default mode.
3029 (@value{GDBP}) info inferiors
3030 Id Description Executable
3033 process 12020 is executing new program: prog2
3034 Program exited normally.
3035 (@value{GDBP}) info inferiors
3036 Id Description Executable
3043 You can use the @code{catch} command to make @value{GDBN} stop whenever
3044 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3045 Catchpoints, ,Setting Catchpoints}.
3047 @node Checkpoint/Restart
3048 @section Setting a @emph{Bookmark} to Return to Later
3053 @cindex snapshot of a process
3054 @cindex rewind program state
3056 On certain operating systems@footnote{Currently, only
3057 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3058 program's state, called a @dfn{checkpoint}, and come back to it
3061 Returning to a checkpoint effectively undoes everything that has
3062 happened in the program since the @code{checkpoint} was saved. This
3063 includes changes in memory, registers, and even (within some limits)
3064 system state. Effectively, it is like going back in time to the
3065 moment when the checkpoint was saved.
3067 Thus, if you're stepping thru a program and you think you're
3068 getting close to the point where things go wrong, you can save
3069 a checkpoint. Then, if you accidentally go too far and miss
3070 the critical statement, instead of having to restart your program
3071 from the beginning, you can just go back to the checkpoint and
3072 start again from there.
3074 This can be especially useful if it takes a lot of time or
3075 steps to reach the point where you think the bug occurs.
3077 To use the @code{checkpoint}/@code{restart} method of debugging:
3082 Save a snapshot of the debugged program's current execution state.
3083 The @code{checkpoint} command takes no arguments, but each checkpoint
3084 is assigned a small integer id, similar to a breakpoint id.
3086 @kindex info checkpoints
3087 @item info checkpoints
3088 List the checkpoints that have been saved in the current debugging
3089 session. For each checkpoint, the following information will be
3096 @item Source line, or label
3099 @kindex restart @var{checkpoint-id}
3100 @item restart @var{checkpoint-id}
3101 Restore the program state that was saved as checkpoint number
3102 @var{checkpoint-id}. All program variables, registers, stack frames
3103 etc.@: will be returned to the values that they had when the checkpoint
3104 was saved. In essence, gdb will ``wind back the clock'' to the point
3105 in time when the checkpoint was saved.
3107 Note that breakpoints, @value{GDBN} variables, command history etc.
3108 are not affected by restoring a checkpoint. In general, a checkpoint
3109 only restores things that reside in the program being debugged, not in
3112 @kindex delete checkpoint @var{checkpoint-id}
3113 @item delete checkpoint @var{checkpoint-id}
3114 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3118 Returning to a previously saved checkpoint will restore the user state
3119 of the program being debugged, plus a significant subset of the system
3120 (OS) state, including file pointers. It won't ``un-write'' data from
3121 a file, but it will rewind the file pointer to the previous location,
3122 so that the previously written data can be overwritten. For files
3123 opened in read mode, the pointer will also be restored so that the
3124 previously read data can be read again.
3126 Of course, characters that have been sent to a printer (or other
3127 external device) cannot be ``snatched back'', and characters received
3128 from eg.@: a serial device can be removed from internal program buffers,
3129 but they cannot be ``pushed back'' into the serial pipeline, ready to
3130 be received again. Similarly, the actual contents of files that have
3131 been changed cannot be restored (at this time).
3133 However, within those constraints, you actually can ``rewind'' your
3134 program to a previously saved point in time, and begin debugging it
3135 again --- and you can change the course of events so as to debug a
3136 different execution path this time.
3138 @cindex checkpoints and process id
3139 Finally, there is one bit of internal program state that will be
3140 different when you return to a checkpoint --- the program's process
3141 id. Each checkpoint will have a unique process id (or @var{pid}),
3142 and each will be different from the program's original @var{pid}.
3143 If your program has saved a local copy of its process id, this could
3144 potentially pose a problem.
3146 @subsection A Non-obvious Benefit of Using Checkpoints
3148 On some systems such as @sc{gnu}/Linux, address space randomization
3149 is performed on new processes for security reasons. This makes it
3150 difficult or impossible to set a breakpoint, or watchpoint, on an
3151 absolute address if you have to restart the program, since the
3152 absolute location of a symbol will change from one execution to the
3155 A checkpoint, however, is an @emph{identical} copy of a process.
3156 Therefore if you create a checkpoint at (eg.@:) the start of main,
3157 and simply return to that checkpoint instead of restarting the
3158 process, you can avoid the effects of address randomization and
3159 your symbols will all stay in the same place.
3162 @chapter Stopping and Continuing
3164 The principal purposes of using a debugger are so that you can stop your
3165 program before it terminates; or so that, if your program runs into
3166 trouble, you can investigate and find out why.
3168 Inside @value{GDBN}, your program may stop for any of several reasons,
3169 such as a signal, a breakpoint, or reaching a new line after a
3170 @value{GDBN} command such as @code{step}. You may then examine and
3171 change variables, set new breakpoints or remove old ones, and then
3172 continue execution. Usually, the messages shown by @value{GDBN} provide
3173 ample explanation of the status of your program---but you can also
3174 explicitly request this information at any time.
3177 @kindex info program
3179 Display information about the status of your program: whether it is
3180 running or not, what process it is, and why it stopped.
3184 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3185 * Continuing and Stepping:: Resuming execution
3187 * Thread Stops:: Stopping and starting multi-thread programs
3191 @section Breakpoints, Watchpoints, and Catchpoints
3194 A @dfn{breakpoint} makes your program stop whenever a certain point in
3195 the program is reached. For each breakpoint, you can add conditions to
3196 control in finer detail whether your program stops. You can set
3197 breakpoints with the @code{break} command and its variants (@pxref{Set
3198 Breaks, ,Setting Breakpoints}), to specify the place where your program
3199 should stop by line number, function name or exact address in the
3202 On some systems, you can set breakpoints in shared libraries before
3203 the executable is run. There is a minor limitation on HP-UX systems:
3204 you must wait until the executable is run in order to set breakpoints
3205 in shared library routines that are not called directly by the program
3206 (for example, routines that are arguments in a @code{pthread_create}
3210 @cindex data breakpoints
3211 @cindex memory tracing
3212 @cindex breakpoint on memory address
3213 @cindex breakpoint on variable modification
3214 A @dfn{watchpoint} is a special breakpoint that stops your program
3215 when the value of an expression changes. The expression may be a value
3216 of a variable, or it could involve values of one or more variables
3217 combined by operators, such as @samp{a + b}. This is sometimes called
3218 @dfn{data breakpoints}. You must use a different command to set
3219 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3220 from that, you can manage a watchpoint like any other breakpoint: you
3221 enable, disable, and delete both breakpoints and watchpoints using the
3224 You can arrange to have values from your program displayed automatically
3225 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3229 @cindex breakpoint on events
3230 A @dfn{catchpoint} is another special breakpoint that stops your program
3231 when a certain kind of event occurs, such as the throwing of a C@t{++}
3232 exception or the loading of a library. As with watchpoints, you use a
3233 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3234 Catchpoints}), but aside from that, you can manage a catchpoint like any
3235 other breakpoint. (To stop when your program receives a signal, use the
3236 @code{handle} command; see @ref{Signals, ,Signals}.)
3238 @cindex breakpoint numbers
3239 @cindex numbers for breakpoints
3240 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3241 catchpoint when you create it; these numbers are successive integers
3242 starting with one. In many of the commands for controlling various
3243 features of breakpoints you use the breakpoint number to say which
3244 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3245 @dfn{disabled}; if disabled, it has no effect on your program until you
3248 @cindex breakpoint ranges
3249 @cindex ranges of breakpoints
3250 Some @value{GDBN} commands accept a range of breakpoints on which to
3251 operate. A breakpoint range is either a single breakpoint number, like
3252 @samp{5}, or two such numbers, in increasing order, separated by a
3253 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3254 all breakpoints in that range are operated on.
3257 * Set Breaks:: Setting breakpoints
3258 * Set Watchpoints:: Setting watchpoints
3259 * Set Catchpoints:: Setting catchpoints
3260 * Delete Breaks:: Deleting breakpoints
3261 * Disabling:: Disabling breakpoints
3262 * Conditions:: Break conditions
3263 * Break Commands:: Breakpoint command lists
3264 * Save Breakpoints:: How to save breakpoints in a file
3265 * Error in Breakpoints:: ``Cannot insert breakpoints''
3266 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3270 @subsection Setting Breakpoints
3272 @c FIXME LMB what does GDB do if no code on line of breakpt?
3273 @c consider in particular declaration with/without initialization.
3275 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3278 @kindex b @r{(@code{break})}
3279 @vindex $bpnum@r{, convenience variable}
3280 @cindex latest breakpoint
3281 Breakpoints are set with the @code{break} command (abbreviated
3282 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3283 number of the breakpoint you've set most recently; see @ref{Convenience
3284 Vars,, Convenience Variables}, for a discussion of what you can do with
3285 convenience variables.
3288 @item break @var{location}
3289 Set a breakpoint at the given @var{location}, which can specify a
3290 function name, a line number, or an address of an instruction.
3291 (@xref{Specify Location}, for a list of all the possible ways to
3292 specify a @var{location}.) The breakpoint will stop your program just
3293 before it executes any of the code in the specified @var{location}.
3295 When using source languages that permit overloading of symbols, such as
3296 C@t{++}, a function name may refer to more than one possible place to break.
3297 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3300 It is also possible to insert a breakpoint that will stop the program
3301 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3302 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3305 When called without any arguments, @code{break} sets a breakpoint at
3306 the next instruction to be executed in the selected stack frame
3307 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3308 innermost, this makes your program stop as soon as control
3309 returns to that frame. This is similar to the effect of a
3310 @code{finish} command in the frame inside the selected frame---except
3311 that @code{finish} does not leave an active breakpoint. If you use
3312 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3313 the next time it reaches the current location; this may be useful
3316 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3317 least one instruction has been executed. If it did not do this, you
3318 would be unable to proceed past a breakpoint without first disabling the
3319 breakpoint. This rule applies whether or not the breakpoint already
3320 existed when your program stopped.
3322 @item break @dots{} if @var{cond}
3323 Set a breakpoint with condition @var{cond}; evaluate the expression
3324 @var{cond} each time the breakpoint is reached, and stop only if the
3325 value is nonzero---that is, if @var{cond} evaluates as true.
3326 @samp{@dots{}} stands for one of the possible arguments described
3327 above (or no argument) specifying where to break. @xref{Conditions,
3328 ,Break Conditions}, for more information on breakpoint conditions.
3331 @item tbreak @var{args}
3332 Set a breakpoint enabled only for one stop. @var{args} are the
3333 same as for the @code{break} command, and the breakpoint is set in the same
3334 way, but the breakpoint is automatically deleted after the first time your
3335 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3338 @cindex hardware breakpoints
3339 @item hbreak @var{args}
3340 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3341 @code{break} command and the breakpoint is set in the same way, but the
3342 breakpoint requires hardware support and some target hardware may not
3343 have this support. The main purpose of this is EPROM/ROM code
3344 debugging, so you can set a breakpoint at an instruction without
3345 changing the instruction. This can be used with the new trap-generation
3346 provided by SPARClite DSU and most x86-based targets. These targets
3347 will generate traps when a program accesses some data or instruction
3348 address that is assigned to the debug registers. However the hardware
3349 breakpoint registers can take a limited number of breakpoints. For
3350 example, on the DSU, only two data breakpoints can be set at a time, and
3351 @value{GDBN} will reject this command if more than two are used. Delete
3352 or disable unused hardware breakpoints before setting new ones
3353 (@pxref{Disabling, ,Disabling Breakpoints}).
3354 @xref{Conditions, ,Break Conditions}.
3355 For remote targets, you can restrict the number of hardware
3356 breakpoints @value{GDBN} will use, see @ref{set remote
3357 hardware-breakpoint-limit}.
3360 @item thbreak @var{args}
3361 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3362 are the same as for the @code{hbreak} command and the breakpoint is set in
3363 the same way. However, like the @code{tbreak} command,
3364 the breakpoint is automatically deleted after the
3365 first time your program stops there. Also, like the @code{hbreak}
3366 command, the breakpoint requires hardware support and some target hardware
3367 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3368 See also @ref{Conditions, ,Break Conditions}.
3371 @cindex regular expression
3372 @cindex breakpoints at functions matching a regexp
3373 @cindex set breakpoints in many functions
3374 @item rbreak @var{regex}
3375 Set breakpoints on all functions matching the regular expression
3376 @var{regex}. This command sets an unconditional breakpoint on all
3377 matches, printing a list of all breakpoints it set. Once these
3378 breakpoints are set, they are treated just like the breakpoints set with
3379 the @code{break} command. You can delete them, disable them, or make
3380 them conditional the same way as any other breakpoint.
3382 The syntax of the regular expression is the standard one used with tools
3383 like @file{grep}. Note that this is different from the syntax used by
3384 shells, so for instance @code{foo*} matches all functions that include
3385 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3386 @code{.*} leading and trailing the regular expression you supply, so to
3387 match only functions that begin with @code{foo}, use @code{^foo}.
3389 @cindex non-member C@t{++} functions, set breakpoint in
3390 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3391 breakpoints on overloaded functions that are not members of any special
3394 @cindex set breakpoints on all functions
3395 The @code{rbreak} command can be used to set breakpoints in
3396 @strong{all} the functions in a program, like this:
3399 (@value{GDBP}) rbreak .
3402 @item rbreak @var{file}:@var{regex}
3403 If @code{rbreak} is called with a filename qualification, it limits
3404 the search for functions matching the given regular expression to the
3405 specified @var{file}. This can be used, for example, to set breakpoints on
3406 every function in a given file:
3409 (@value{GDBP}) rbreak file.c:.
3412 The colon separating the filename qualifier from the regex may
3413 optionally be surrounded by spaces.
3415 @kindex info breakpoints
3416 @cindex @code{$_} and @code{info breakpoints}
3417 @item info breakpoints @r{[}@var{n}@r{]}
3418 @itemx info break @r{[}@var{n}@r{]}
3419 Print a table of all breakpoints, watchpoints, and catchpoints set and
3420 not deleted. Optional argument @var{n} means print information only
3421 about the specified breakpoint (or watchpoint or catchpoint). For
3422 each breakpoint, following columns are printed:
3425 @item Breakpoint Numbers
3427 Breakpoint, watchpoint, or catchpoint.
3429 Whether the breakpoint is marked to be disabled or deleted when hit.
3430 @item Enabled or Disabled
3431 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3432 that are not enabled.
3434 Where the breakpoint is in your program, as a memory address. For a
3435 pending breakpoint whose address is not yet known, this field will
3436 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3437 library that has the symbol or line referred by breakpoint is loaded.
3438 See below for details. A breakpoint with several locations will
3439 have @samp{<MULTIPLE>} in this field---see below for details.
3441 Where the breakpoint is in the source for your program, as a file and
3442 line number. For a pending breakpoint, the original string passed to
3443 the breakpoint command will be listed as it cannot be resolved until
3444 the appropriate shared library is loaded in the future.
3448 If a breakpoint is conditional, @code{info break} shows the condition on
3449 the line following the affected breakpoint; breakpoint commands, if any,
3450 are listed after that. A pending breakpoint is allowed to have a condition
3451 specified for it. The condition is not parsed for validity until a shared
3452 library is loaded that allows the pending breakpoint to resolve to a
3456 @code{info break} with a breakpoint
3457 number @var{n} as argument lists only that breakpoint. The
3458 convenience variable @code{$_} and the default examining-address for
3459 the @code{x} command are set to the address of the last breakpoint
3460 listed (@pxref{Memory, ,Examining Memory}).
3463 @code{info break} displays a count of the number of times the breakpoint
3464 has been hit. This is especially useful in conjunction with the
3465 @code{ignore} command. You can ignore a large number of breakpoint
3466 hits, look at the breakpoint info to see how many times the breakpoint
3467 was hit, and then run again, ignoring one less than that number. This
3468 will get you quickly to the last hit of that breakpoint.
3471 @value{GDBN} allows you to set any number of breakpoints at the same place in
3472 your program. There is nothing silly or meaningless about this. When
3473 the breakpoints are conditional, this is even useful
3474 (@pxref{Conditions, ,Break Conditions}).
3476 @cindex multiple locations, breakpoints
3477 @cindex breakpoints, multiple locations
3478 It is possible that a breakpoint corresponds to several locations
3479 in your program. Examples of this situation are:
3483 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3484 instances of the function body, used in different cases.
3487 For a C@t{++} template function, a given line in the function can
3488 correspond to any number of instantiations.
3491 For an inlined function, a given source line can correspond to
3492 several places where that function is inlined.
3495 In all those cases, @value{GDBN} will insert a breakpoint at all
3496 the relevant locations@footnote{
3497 As of this writing, multiple-location breakpoints work only if there's
3498 line number information for all the locations. This means that they
3499 will generally not work in system libraries, unless you have debug
3500 info with line numbers for them.}.
3502 A breakpoint with multiple locations is displayed in the breakpoint
3503 table using several rows---one header row, followed by one row for
3504 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3505 address column. The rows for individual locations contain the actual
3506 addresses for locations, and show the functions to which those
3507 locations belong. The number column for a location is of the form
3508 @var{breakpoint-number}.@var{location-number}.
3513 Num Type Disp Enb Address What
3514 1 breakpoint keep y <MULTIPLE>
3516 breakpoint already hit 1 time
3517 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3518 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3521 Each location can be individually enabled or disabled by passing
3522 @var{breakpoint-number}.@var{location-number} as argument to the
3523 @code{enable} and @code{disable} commands. Note that you cannot
3524 delete the individual locations from the list, you can only delete the
3525 entire list of locations that belong to their parent breakpoint (with
3526 the @kbd{delete @var{num}} command, where @var{num} is the number of
3527 the parent breakpoint, 1 in the above example). Disabling or enabling
3528 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3529 that belong to that breakpoint.
3531 @cindex pending breakpoints
3532 It's quite common to have a breakpoint inside a shared library.
3533 Shared libraries can be loaded and unloaded explicitly,
3534 and possibly repeatedly, as the program is executed. To support
3535 this use case, @value{GDBN} updates breakpoint locations whenever
3536 any shared library is loaded or unloaded. Typically, you would
3537 set a breakpoint in a shared library at the beginning of your
3538 debugging session, when the library is not loaded, and when the
3539 symbols from the library are not available. When you try to set
3540 breakpoint, @value{GDBN} will ask you if you want to set
3541 a so called @dfn{pending breakpoint}---breakpoint whose address
3542 is not yet resolved.
3544 After the program is run, whenever a new shared library is loaded,
3545 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3546 shared library contains the symbol or line referred to by some
3547 pending breakpoint, that breakpoint is resolved and becomes an
3548 ordinary breakpoint. When a library is unloaded, all breakpoints
3549 that refer to its symbols or source lines become pending again.
3551 This logic works for breakpoints with multiple locations, too. For
3552 example, if you have a breakpoint in a C@t{++} template function, and
3553 a newly loaded shared library has an instantiation of that template,
3554 a new location is added to the list of locations for the breakpoint.
3556 Except for having unresolved address, pending breakpoints do not
3557 differ from regular breakpoints. You can set conditions or commands,
3558 enable and disable them and perform other breakpoint operations.
3560 @value{GDBN} provides some additional commands for controlling what
3561 happens when the @samp{break} command cannot resolve breakpoint
3562 address specification to an address:
3564 @kindex set breakpoint pending
3565 @kindex show breakpoint pending
3567 @item set breakpoint pending auto
3568 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3569 location, it queries you whether a pending breakpoint should be created.
3571 @item set breakpoint pending on
3572 This indicates that an unrecognized breakpoint location should automatically
3573 result in a pending breakpoint being created.
3575 @item set breakpoint pending off
3576 This indicates that pending breakpoints are not to be created. Any
3577 unrecognized breakpoint location results in an error. This setting does
3578 not affect any pending breakpoints previously created.
3580 @item show breakpoint pending
3581 Show the current behavior setting for creating pending breakpoints.
3584 The settings above only affect the @code{break} command and its
3585 variants. Once breakpoint is set, it will be automatically updated
3586 as shared libraries are loaded and unloaded.
3588 @cindex automatic hardware breakpoints
3589 For some targets, @value{GDBN} can automatically decide if hardware or
3590 software breakpoints should be used, depending on whether the
3591 breakpoint address is read-only or read-write. This applies to
3592 breakpoints set with the @code{break} command as well as to internal
3593 breakpoints set by commands like @code{next} and @code{finish}. For
3594 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3597 You can control this automatic behaviour with the following commands::
3599 @kindex set breakpoint auto-hw
3600 @kindex show breakpoint auto-hw
3602 @item set breakpoint auto-hw on
3603 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3604 will try to use the target memory map to decide if software or hardware
3605 breakpoint must be used.
3607 @item set breakpoint auto-hw off
3608 This indicates @value{GDBN} should not automatically select breakpoint
3609 type. If the target provides a memory map, @value{GDBN} will warn when
3610 trying to set software breakpoint at a read-only address.
3613 @value{GDBN} normally implements breakpoints by replacing the program code
3614 at the breakpoint address with a special instruction, which, when
3615 executed, given control to the debugger. By default, the program
3616 code is so modified only when the program is resumed. As soon as
3617 the program stops, @value{GDBN} restores the original instructions. This
3618 behaviour guards against leaving breakpoints inserted in the
3619 target should gdb abrubptly disconnect. However, with slow remote
3620 targets, inserting and removing breakpoint can reduce the performance.
3621 This behavior can be controlled with the following commands::
3623 @kindex set breakpoint always-inserted
3624 @kindex show breakpoint always-inserted
3626 @item set breakpoint always-inserted off
3627 All breakpoints, including newly added by the user, are inserted in
3628 the target only when the target is resumed. All breakpoints are
3629 removed from the target when it stops.
3631 @item set breakpoint always-inserted on
3632 Causes all breakpoints to be inserted in the target at all times. If
3633 the user adds a new breakpoint, or changes an existing breakpoint, the
3634 breakpoints in the target are updated immediately. A breakpoint is
3635 removed from the target only when breakpoint itself is removed.
3637 @cindex non-stop mode, and @code{breakpoint always-inserted}
3638 @item set breakpoint always-inserted auto
3639 This is the default mode. If @value{GDBN} is controlling the inferior
3640 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3641 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3642 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3643 @code{breakpoint always-inserted} mode is off.
3646 @cindex negative breakpoint numbers
3647 @cindex internal @value{GDBN} breakpoints
3648 @value{GDBN} itself sometimes sets breakpoints in your program for
3649 special purposes, such as proper handling of @code{longjmp} (in C
3650 programs). These internal breakpoints are assigned negative numbers,
3651 starting with @code{-1}; @samp{info breakpoints} does not display them.
3652 You can see these breakpoints with the @value{GDBN} maintenance command
3653 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3656 @node Set Watchpoints
3657 @subsection Setting Watchpoints
3659 @cindex setting watchpoints
3660 You can use a watchpoint to stop execution whenever the value of an
3661 expression changes, without having to predict a particular place where
3662 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3663 The expression may be as simple as the value of a single variable, or
3664 as complex as many variables combined by operators. Examples include:
3668 A reference to the value of a single variable.
3671 An address cast to an appropriate data type. For example,
3672 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3673 address (assuming an @code{int} occupies 4 bytes).
3676 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3677 expression can use any operators valid in the program's native
3678 language (@pxref{Languages}).
3681 You can set a watchpoint on an expression even if the expression can
3682 not be evaluated yet. For instance, you can set a watchpoint on
3683 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3684 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3685 the expression produces a valid value. If the expression becomes
3686 valid in some other way than changing a variable (e.g.@: if the memory
3687 pointed to by @samp{*global_ptr} becomes readable as the result of a
3688 @code{malloc} call), @value{GDBN} may not stop until the next time
3689 the expression changes.
3691 @cindex software watchpoints
3692 @cindex hardware watchpoints
3693 Depending on your system, watchpoints may be implemented in software or
3694 hardware. @value{GDBN} does software watchpointing by single-stepping your
3695 program and testing the variable's value each time, which is hundreds of
3696 times slower than normal execution. (But this may still be worth it, to
3697 catch errors where you have no clue what part of your program is the
3700 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3701 x86-based targets, @value{GDBN} includes support for hardware
3702 watchpoints, which do not slow down the running of your program.
3706 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3707 Set a watchpoint for an expression. @value{GDBN} will break when the
3708 expression @var{expr} is written into by the program and its value
3709 changes. The simplest (and the most popular) use of this command is
3710 to watch the value of a single variable:
3713 (@value{GDBP}) watch foo
3716 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3717 clause, @value{GDBN} breaks only when the thread identified by
3718 @var{threadnum} changes the value of @var{expr}. If any other threads
3719 change the value of @var{expr}, @value{GDBN} will not break. Note
3720 that watchpoints restricted to a single thread in this way only work
3721 with Hardware Watchpoints.
3724 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3725 Set a watchpoint that will break when the value of @var{expr} is read
3729 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3730 Set a watchpoint that will break when @var{expr} is either read from
3731 or written into by the program.
3733 @kindex info watchpoints @r{[}@var{n}@r{]}
3734 @item info watchpoints
3735 This command prints a list of watchpoints, using the same format as
3736 @code{info break} (@pxref{Set Breaks}).
3739 If you watch for a change in a numerically entered address you need to
3740 dereference it, as the address itself is just a constant number which will
3741 never change. @value{GDBN} refuses to create a watchpoint that watches
3742 a never-changing value:
3745 (@value{GDBP}) watch 0x600850
3746 Cannot watch constant value 0x600850.
3747 (@value{GDBP}) watch *(int *) 0x600850
3748 Watchpoint 1: *(int *) 6293584
3751 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3752 watchpoints execute very quickly, and the debugger reports a change in
3753 value at the exact instruction where the change occurs. If @value{GDBN}
3754 cannot set a hardware watchpoint, it sets a software watchpoint, which
3755 executes more slowly and reports the change in value at the next
3756 @emph{statement}, not the instruction, after the change occurs.
3758 @cindex use only software watchpoints
3759 You can force @value{GDBN} to use only software watchpoints with the
3760 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3761 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3762 the underlying system supports them. (Note that hardware-assisted
3763 watchpoints that were set @emph{before} setting
3764 @code{can-use-hw-watchpoints} to zero will still use the hardware
3765 mechanism of watching expression values.)
3768 @item set can-use-hw-watchpoints
3769 @kindex set can-use-hw-watchpoints
3770 Set whether or not to use hardware watchpoints.
3772 @item show can-use-hw-watchpoints
3773 @kindex show can-use-hw-watchpoints
3774 Show the current mode of using hardware watchpoints.
3777 For remote targets, you can restrict the number of hardware
3778 watchpoints @value{GDBN} will use, see @ref{set remote
3779 hardware-breakpoint-limit}.
3781 When you issue the @code{watch} command, @value{GDBN} reports
3784 Hardware watchpoint @var{num}: @var{expr}
3788 if it was able to set a hardware watchpoint.
3790 Currently, the @code{awatch} and @code{rwatch} commands can only set
3791 hardware watchpoints, because accesses to data that don't change the
3792 value of the watched expression cannot be detected without examining
3793 every instruction as it is being executed, and @value{GDBN} does not do
3794 that currently. If @value{GDBN} finds that it is unable to set a
3795 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3796 will print a message like this:
3799 Expression cannot be implemented with read/access watchpoint.
3802 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3803 data type of the watched expression is wider than what a hardware
3804 watchpoint on the target machine can handle. For example, some systems
3805 can only watch regions that are up to 4 bytes wide; on such systems you
3806 cannot set hardware watchpoints for an expression that yields a
3807 double-precision floating-point number (which is typically 8 bytes
3808 wide). As a work-around, it might be possible to break the large region
3809 into a series of smaller ones and watch them with separate watchpoints.
3811 If you set too many hardware watchpoints, @value{GDBN} might be unable
3812 to insert all of them when you resume the execution of your program.
3813 Since the precise number of active watchpoints is unknown until such
3814 time as the program is about to be resumed, @value{GDBN} might not be
3815 able to warn you about this when you set the watchpoints, and the
3816 warning will be printed only when the program is resumed:
3819 Hardware watchpoint @var{num}: Could not insert watchpoint
3823 If this happens, delete or disable some of the watchpoints.
3825 Watching complex expressions that reference many variables can also
3826 exhaust the resources available for hardware-assisted watchpoints.
3827 That's because @value{GDBN} needs to watch every variable in the
3828 expression with separately allocated resources.
3830 If you call a function interactively using @code{print} or @code{call},
3831 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3832 kind of breakpoint or the call completes.
3834 @value{GDBN} automatically deletes watchpoints that watch local
3835 (automatic) variables, or expressions that involve such variables, when
3836 they go out of scope, that is, when the execution leaves the block in
3837 which these variables were defined. In particular, when the program
3838 being debugged terminates, @emph{all} local variables go out of scope,
3839 and so only watchpoints that watch global variables remain set. If you
3840 rerun the program, you will need to set all such watchpoints again. One
3841 way of doing that would be to set a code breakpoint at the entry to the
3842 @code{main} function and when it breaks, set all the watchpoints.
3844 @cindex watchpoints and threads
3845 @cindex threads and watchpoints
3846 In multi-threaded programs, watchpoints will detect changes to the
3847 watched expression from every thread.
3850 @emph{Warning:} In multi-threaded programs, software watchpoints
3851 have only limited usefulness. If @value{GDBN} creates a software
3852 watchpoint, it can only watch the value of an expression @emph{in a
3853 single thread}. If you are confident that the expression can only
3854 change due to the current thread's activity (and if you are also
3855 confident that no other thread can become current), then you can use
3856 software watchpoints as usual. However, @value{GDBN} may not notice
3857 when a non-current thread's activity changes the expression. (Hardware
3858 watchpoints, in contrast, watch an expression in all threads.)
3861 @xref{set remote hardware-watchpoint-limit}.
3863 @node Set Catchpoints
3864 @subsection Setting Catchpoints
3865 @cindex catchpoints, setting
3866 @cindex exception handlers
3867 @cindex event handling
3869 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3870 kinds of program events, such as C@t{++} exceptions or the loading of a
3871 shared library. Use the @code{catch} command to set a catchpoint.
3875 @item catch @var{event}
3876 Stop when @var{event} occurs. @var{event} can be any of the following:
3879 @cindex stop on C@t{++} exceptions
3880 The throwing of a C@t{++} exception.
3883 The catching of a C@t{++} exception.
3886 @cindex Ada exception catching
3887 @cindex catch Ada exceptions
3888 An Ada exception being raised. If an exception name is specified
3889 at the end of the command (eg @code{catch exception Program_Error}),
3890 the debugger will stop only when this specific exception is raised.
3891 Otherwise, the debugger stops execution when any Ada exception is raised.
3893 When inserting an exception catchpoint on a user-defined exception whose
3894 name is identical to one of the exceptions defined by the language, the
3895 fully qualified name must be used as the exception name. Otherwise,
3896 @value{GDBN} will assume that it should stop on the pre-defined exception
3897 rather than the user-defined one. For instance, assuming an exception
3898 called @code{Constraint_Error} is defined in package @code{Pck}, then
3899 the command to use to catch such exceptions is @kbd{catch exception
3900 Pck.Constraint_Error}.
3902 @item exception unhandled
3903 An exception that was raised but is not handled by the program.
3906 A failed Ada assertion.
3909 @cindex break on fork/exec
3910 A call to @code{exec}. This is currently only available for HP-UX
3914 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3915 @cindex break on a system call.
3916 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3917 syscall is a mechanism for application programs to request a service
3918 from the operating system (OS) or one of the OS system services.
3919 @value{GDBN} can catch some or all of the syscalls issued by the
3920 debuggee, and show the related information for each syscall. If no
3921 argument is specified, calls to and returns from all system calls
3924 @var{name} can be any system call name that is valid for the
3925 underlying OS. Just what syscalls are valid depends on the OS. On
3926 GNU and Unix systems, you can find the full list of valid syscall
3927 names on @file{/usr/include/asm/unistd.h}.
3929 @c For MS-Windows, the syscall names and the corresponding numbers
3930 @c can be found, e.g., on this URL:
3931 @c http://www.metasploit.com/users/opcode/syscalls.html
3932 @c but we don't support Windows syscalls yet.
3934 Normally, @value{GDBN} knows in advance which syscalls are valid for
3935 each OS, so you can use the @value{GDBN} command-line completion
3936 facilities (@pxref{Completion,, command completion}) to list the
3939 You may also specify the system call numerically. A syscall's
3940 number is the value passed to the OS's syscall dispatcher to
3941 identify the requested service. When you specify the syscall by its
3942 name, @value{GDBN} uses its database of syscalls to convert the name
3943 into the corresponding numeric code, but using the number directly
3944 may be useful if @value{GDBN}'s database does not have the complete
3945 list of syscalls on your system (e.g., because @value{GDBN} lags
3946 behind the OS upgrades).
3948 The example below illustrates how this command works if you don't provide
3952 (@value{GDBP}) catch syscall
3953 Catchpoint 1 (syscall)
3955 Starting program: /tmp/catch-syscall
3957 Catchpoint 1 (call to syscall 'close'), \
3958 0xffffe424 in __kernel_vsyscall ()
3962 Catchpoint 1 (returned from syscall 'close'), \
3963 0xffffe424 in __kernel_vsyscall ()
3967 Here is an example of catching a system call by name:
3970 (@value{GDBP}) catch syscall chroot
3971 Catchpoint 1 (syscall 'chroot' [61])
3973 Starting program: /tmp/catch-syscall
3975 Catchpoint 1 (call to syscall 'chroot'), \
3976 0xffffe424 in __kernel_vsyscall ()
3980 Catchpoint 1 (returned from syscall 'chroot'), \
3981 0xffffe424 in __kernel_vsyscall ()
3985 An example of specifying a system call numerically. In the case
3986 below, the syscall number has a corresponding entry in the XML
3987 file, so @value{GDBN} finds its name and prints it:
3990 (@value{GDBP}) catch syscall 252
3991 Catchpoint 1 (syscall(s) 'exit_group')
3993 Starting program: /tmp/catch-syscall
3995 Catchpoint 1 (call to syscall 'exit_group'), \
3996 0xffffe424 in __kernel_vsyscall ()
4000 Program exited normally.
4004 However, there can be situations when there is no corresponding name
4005 in XML file for that syscall number. In this case, @value{GDBN} prints
4006 a warning message saying that it was not able to find the syscall name,
4007 but the catchpoint will be set anyway. See the example below:
4010 (@value{GDBP}) catch syscall 764
4011 warning: The number '764' does not represent a known syscall.
4012 Catchpoint 2 (syscall 764)
4016 If you configure @value{GDBN} using the @samp{--without-expat} option,
4017 it will not be able to display syscall names. Also, if your
4018 architecture does not have an XML file describing its system calls,
4019 you will not be able to see the syscall names. It is important to
4020 notice that these two features are used for accessing the syscall
4021 name database. In either case, you will see a warning like this:
4024 (@value{GDBP}) catch syscall
4025 warning: Could not open "syscalls/i386-linux.xml"
4026 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4027 GDB will not be able to display syscall names.
4028 Catchpoint 1 (syscall)
4032 Of course, the file name will change depending on your architecture and system.
4034 Still using the example above, you can also try to catch a syscall by its
4035 number. In this case, you would see something like:
4038 (@value{GDBP}) catch syscall 252
4039 Catchpoint 1 (syscall(s) 252)
4042 Again, in this case @value{GDBN} would not be able to display syscall's names.
4045 A call to @code{fork}. This is currently only available for HP-UX
4049 A call to @code{vfork}. This is currently only available for HP-UX
4054 @item tcatch @var{event}
4055 Set a catchpoint that is enabled only for one stop. The catchpoint is
4056 automatically deleted after the first time the event is caught.
4060 Use the @code{info break} command to list the current catchpoints.
4062 There are currently some limitations to C@t{++} exception handling
4063 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4067 If you call a function interactively, @value{GDBN} normally returns
4068 control to you when the function has finished executing. If the call
4069 raises an exception, however, the call may bypass the mechanism that
4070 returns control to you and cause your program either to abort or to
4071 simply continue running until it hits a breakpoint, catches a signal
4072 that @value{GDBN} is listening for, or exits. This is the case even if
4073 you set a catchpoint for the exception; catchpoints on exceptions are
4074 disabled within interactive calls.
4077 You cannot raise an exception interactively.
4080 You cannot install an exception handler interactively.
4083 @cindex raise exceptions
4084 Sometimes @code{catch} is not the best way to debug exception handling:
4085 if you need to know exactly where an exception is raised, it is better to
4086 stop @emph{before} the exception handler is called, since that way you
4087 can see the stack before any unwinding takes place. If you set a
4088 breakpoint in an exception handler instead, it may not be easy to find
4089 out where the exception was raised.
4091 To stop just before an exception handler is called, you need some
4092 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4093 raised by calling a library function named @code{__raise_exception}
4094 which has the following ANSI C interface:
4097 /* @var{addr} is where the exception identifier is stored.
4098 @var{id} is the exception identifier. */
4099 void __raise_exception (void **addr, void *id);
4103 To make the debugger catch all exceptions before any stack
4104 unwinding takes place, set a breakpoint on @code{__raise_exception}
4105 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4107 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4108 that depends on the value of @var{id}, you can stop your program when
4109 a specific exception is raised. You can use multiple conditional
4110 breakpoints to stop your program when any of a number of exceptions are
4115 @subsection Deleting Breakpoints
4117 @cindex clearing breakpoints, watchpoints, catchpoints
4118 @cindex deleting breakpoints, watchpoints, catchpoints
4119 It is often necessary to eliminate a breakpoint, watchpoint, or
4120 catchpoint once it has done its job and you no longer want your program
4121 to stop there. This is called @dfn{deleting} the breakpoint. A
4122 breakpoint that has been deleted no longer exists; it is forgotten.
4124 With the @code{clear} command you can delete breakpoints according to
4125 where they are in your program. With the @code{delete} command you can
4126 delete individual breakpoints, watchpoints, or catchpoints by specifying
4127 their breakpoint numbers.
4129 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4130 automatically ignores breakpoints on the first instruction to be executed
4131 when you continue execution without changing the execution address.
4136 Delete any breakpoints at the next instruction to be executed in the
4137 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4138 the innermost frame is selected, this is a good way to delete a
4139 breakpoint where your program just stopped.
4141 @item clear @var{location}
4142 Delete any breakpoints set at the specified @var{location}.
4143 @xref{Specify Location}, for the various forms of @var{location}; the
4144 most useful ones are listed below:
4147 @item clear @var{function}
4148 @itemx clear @var{filename}:@var{function}
4149 Delete any breakpoints set at entry to the named @var{function}.
4151 @item clear @var{linenum}
4152 @itemx clear @var{filename}:@var{linenum}
4153 Delete any breakpoints set at or within the code of the specified
4154 @var{linenum} of the specified @var{filename}.
4157 @cindex delete breakpoints
4159 @kindex d @r{(@code{delete})}
4160 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4161 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4162 ranges specified as arguments. If no argument is specified, delete all
4163 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4164 confirm off}). You can abbreviate this command as @code{d}.
4168 @subsection Disabling Breakpoints
4170 @cindex enable/disable a breakpoint
4171 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4172 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4173 it had been deleted, but remembers the information on the breakpoint so
4174 that you can @dfn{enable} it again later.
4176 You disable and enable breakpoints, watchpoints, and catchpoints with
4177 the @code{enable} and @code{disable} commands, optionally specifying
4178 one or more breakpoint numbers as arguments. Use @code{info break} to
4179 print a list of all breakpoints, watchpoints, and catchpoints if you
4180 do not know which numbers to use.
4182 Disabling and enabling a breakpoint that has multiple locations
4183 affects all of its locations.
4185 A breakpoint, watchpoint, or catchpoint can have any of four different
4186 states of enablement:
4190 Enabled. The breakpoint stops your program. A breakpoint set
4191 with the @code{break} command starts out in this state.
4193 Disabled. The breakpoint has no effect on your program.
4195 Enabled once. The breakpoint stops your program, but then becomes
4198 Enabled for deletion. The breakpoint stops your program, but
4199 immediately after it does so it is deleted permanently. A breakpoint
4200 set with the @code{tbreak} command starts out in this state.
4203 You can use the following commands to enable or disable breakpoints,
4204 watchpoints, and catchpoints:
4208 @kindex dis @r{(@code{disable})}
4209 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4210 Disable the specified breakpoints---or all breakpoints, if none are
4211 listed. A disabled breakpoint has no effect but is not forgotten. All
4212 options such as ignore-counts, conditions and commands are remembered in
4213 case the breakpoint is enabled again later. You may abbreviate
4214 @code{disable} as @code{dis}.
4217 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4218 Enable the specified breakpoints (or all defined breakpoints). They
4219 become effective once again in stopping your program.
4221 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4222 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4223 of these breakpoints immediately after stopping your program.
4225 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4226 Enable the specified breakpoints to work once, then die. @value{GDBN}
4227 deletes any of these breakpoints as soon as your program stops there.
4228 Breakpoints set by the @code{tbreak} command start out in this state.
4231 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4232 @c confusing: tbreak is also initially enabled.
4233 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4234 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4235 subsequently, they become disabled or enabled only when you use one of
4236 the commands above. (The command @code{until} can set and delete a
4237 breakpoint of its own, but it does not change the state of your other
4238 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4242 @subsection Break Conditions
4243 @cindex conditional breakpoints
4244 @cindex breakpoint conditions
4246 @c FIXME what is scope of break condition expr? Context where wanted?
4247 @c in particular for a watchpoint?
4248 The simplest sort of breakpoint breaks every time your program reaches a
4249 specified place. You can also specify a @dfn{condition} for a
4250 breakpoint. A condition is just a Boolean expression in your
4251 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4252 a condition evaluates the expression each time your program reaches it,
4253 and your program stops only if the condition is @emph{true}.
4255 This is the converse of using assertions for program validation; in that
4256 situation, you want to stop when the assertion is violated---that is,
4257 when the condition is false. In C, if you want to test an assertion expressed
4258 by the condition @var{assert}, you should set the condition
4259 @samp{! @var{assert}} on the appropriate breakpoint.
4261 Conditions are also accepted for watchpoints; you may not need them,
4262 since a watchpoint is inspecting the value of an expression anyhow---but
4263 it might be simpler, say, to just set a watchpoint on a variable name,
4264 and specify a condition that tests whether the new value is an interesting
4267 Break conditions can have side effects, and may even call functions in
4268 your program. This can be useful, for example, to activate functions
4269 that log program progress, or to use your own print functions to
4270 format special data structures. The effects are completely predictable
4271 unless there is another enabled breakpoint at the same address. (In
4272 that case, @value{GDBN} might see the other breakpoint first and stop your
4273 program without checking the condition of this one.) Note that
4274 breakpoint commands are usually more convenient and flexible than break
4276 purpose of performing side effects when a breakpoint is reached
4277 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4279 Break conditions can be specified when a breakpoint is set, by using
4280 @samp{if} in the arguments to the @code{break} command. @xref{Set
4281 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4282 with the @code{condition} command.
4284 You can also use the @code{if} keyword with the @code{watch} command.
4285 The @code{catch} command does not recognize the @code{if} keyword;
4286 @code{condition} is the only way to impose a further condition on a
4291 @item condition @var{bnum} @var{expression}
4292 Specify @var{expression} as the break condition for breakpoint,
4293 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4294 breakpoint @var{bnum} stops your program only if the value of
4295 @var{expression} is true (nonzero, in C). When you use
4296 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4297 syntactic correctness, and to determine whether symbols in it have
4298 referents in the context of your breakpoint. If @var{expression} uses
4299 symbols not referenced in the context of the breakpoint, @value{GDBN}
4300 prints an error message:
4303 No symbol "foo" in current context.
4308 not actually evaluate @var{expression} at the time the @code{condition}
4309 command (or a command that sets a breakpoint with a condition, like
4310 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4312 @item condition @var{bnum}
4313 Remove the condition from breakpoint number @var{bnum}. It becomes
4314 an ordinary unconditional breakpoint.
4317 @cindex ignore count (of breakpoint)
4318 A special case of a breakpoint condition is to stop only when the
4319 breakpoint has been reached a certain number of times. This is so
4320 useful that there is a special way to do it, using the @dfn{ignore
4321 count} of the breakpoint. Every breakpoint has an ignore count, which
4322 is an integer. Most of the time, the ignore count is zero, and
4323 therefore has no effect. But if your program reaches a breakpoint whose
4324 ignore count is positive, then instead of stopping, it just decrements
4325 the ignore count by one and continues. As a result, if the ignore count
4326 value is @var{n}, the breakpoint does not stop the next @var{n} times
4327 your program reaches it.
4331 @item ignore @var{bnum} @var{count}
4332 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4333 The next @var{count} times the breakpoint is reached, your program's
4334 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4337 To make the breakpoint stop the next time it is reached, specify
4340 When you use @code{continue} to resume execution of your program from a
4341 breakpoint, you can specify an ignore count directly as an argument to
4342 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4343 Stepping,,Continuing and Stepping}.
4345 If a breakpoint has a positive ignore count and a condition, the
4346 condition is not checked. Once the ignore count reaches zero,
4347 @value{GDBN} resumes checking the condition.
4349 You could achieve the effect of the ignore count with a condition such
4350 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4351 is decremented each time. @xref{Convenience Vars, ,Convenience
4355 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4358 @node Break Commands
4359 @subsection Breakpoint Command Lists
4361 @cindex breakpoint commands
4362 You can give any breakpoint (or watchpoint or catchpoint) a series of
4363 commands to execute when your program stops due to that breakpoint. For
4364 example, you might want to print the values of certain expressions, or
4365 enable other breakpoints.
4369 @kindex end@r{ (breakpoint commands)}
4370 @item commands @r{[}@var{range}@dots{}@r{]}
4371 @itemx @dots{} @var{command-list} @dots{}
4373 Specify a list of commands for the given breakpoints. The commands
4374 themselves appear on the following lines. Type a line containing just
4375 @code{end} to terminate the commands.
4377 To remove all commands from a breakpoint, type @code{commands} and
4378 follow it immediately with @code{end}; that is, give no commands.
4380 With no argument, @code{commands} refers to the last breakpoint,
4381 watchpoint, or catchpoint set (not to the breakpoint most recently
4382 encountered). If the most recent breakpoints were set with a single
4383 command, then the @code{commands} will apply to all the breakpoints
4384 set by that command. This applies to breakpoints set by
4385 @code{rbreak}, and also applies when a single @code{break} command
4386 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4390 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4391 disabled within a @var{command-list}.
4393 You can use breakpoint commands to start your program up again. Simply
4394 use the @code{continue} command, or @code{step}, or any other command
4395 that resumes execution.
4397 Any other commands in the command list, after a command that resumes
4398 execution, are ignored. This is because any time you resume execution
4399 (even with a simple @code{next} or @code{step}), you may encounter
4400 another breakpoint---which could have its own command list, leading to
4401 ambiguities about which list to execute.
4404 If the first command you specify in a command list is @code{silent}, the
4405 usual message about stopping at a breakpoint is not printed. This may
4406 be desirable for breakpoints that are to print a specific message and
4407 then continue. If none of the remaining commands print anything, you
4408 see no sign that the breakpoint was reached. @code{silent} is
4409 meaningful only at the beginning of a breakpoint command list.
4411 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4412 print precisely controlled output, and are often useful in silent
4413 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4415 For example, here is how you could use breakpoint commands to print the
4416 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4422 printf "x is %d\n",x
4427 One application for breakpoint commands is to compensate for one bug so
4428 you can test for another. Put a breakpoint just after the erroneous line
4429 of code, give it a condition to detect the case in which something
4430 erroneous has been done, and give it commands to assign correct values
4431 to any variables that need them. End with the @code{continue} command
4432 so that your program does not stop, and start with the @code{silent}
4433 command so that no output is produced. Here is an example:
4444 @node Save Breakpoints
4445 @subsection How to save breakpoints to a file
4447 To save breakpoint definitions to a file use the @w{@code{save
4448 breakpoints}} command.
4451 @kindex save breakpoints
4452 @cindex save breakpoints to a file for future sessions
4453 @item save breakpoints [@var{filename}]
4454 This command saves all current breakpoint definitions together with
4455 their commands and ignore counts, into a file @file{@var{filename}}
4456 suitable for use in a later debugging session. This includes all
4457 types of breakpoints (breakpoints, watchpoints, catchpoints,
4458 tracepoints). To read the saved breakpoint definitions, use the
4459 @code{source} command (@pxref{Command Files}). Note that watchpoints
4460 with expressions involving local variables may fail to be recreated
4461 because it may not be possible to access the context where the
4462 watchpoint is valid anymore. Because the saved breakpoint definitions
4463 are simply a sequence of @value{GDBN} commands that recreate the
4464 breakpoints, you can edit the file in your favorite editing program,
4465 and remove the breakpoint definitions you're not interested in, or
4466 that can no longer be recreated.
4469 @c @ifclear BARETARGET
4470 @node Error in Breakpoints
4471 @subsection ``Cannot insert breakpoints''
4473 If you request too many active hardware-assisted breakpoints and
4474 watchpoints, you will see this error message:
4476 @c FIXME: the precise wording of this message may change; the relevant
4477 @c source change is not committed yet (Sep 3, 1999).
4479 Stopped; cannot insert breakpoints.
4480 You may have requested too many hardware breakpoints and watchpoints.
4484 This message is printed when you attempt to resume the program, since
4485 only then @value{GDBN} knows exactly how many hardware breakpoints and
4486 watchpoints it needs to insert.
4488 When this message is printed, you need to disable or remove some of the
4489 hardware-assisted breakpoints and watchpoints, and then continue.
4491 @node Breakpoint-related Warnings
4492 @subsection ``Breakpoint address adjusted...''
4493 @cindex breakpoint address adjusted
4495 Some processor architectures place constraints on the addresses at
4496 which breakpoints may be placed. For architectures thus constrained,
4497 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4498 with the constraints dictated by the architecture.
4500 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4501 a VLIW architecture in which a number of RISC-like instructions may be
4502 bundled together for parallel execution. The FR-V architecture
4503 constrains the location of a breakpoint instruction within such a
4504 bundle to the instruction with the lowest address. @value{GDBN}
4505 honors this constraint by adjusting a breakpoint's address to the
4506 first in the bundle.
4508 It is not uncommon for optimized code to have bundles which contain
4509 instructions from different source statements, thus it may happen that
4510 a breakpoint's address will be adjusted from one source statement to
4511 another. Since this adjustment may significantly alter @value{GDBN}'s
4512 breakpoint related behavior from what the user expects, a warning is
4513 printed when the breakpoint is first set and also when the breakpoint
4516 A warning like the one below is printed when setting a breakpoint
4517 that's been subject to address adjustment:
4520 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4523 Such warnings are printed both for user settable and @value{GDBN}'s
4524 internal breakpoints. If you see one of these warnings, you should
4525 verify that a breakpoint set at the adjusted address will have the
4526 desired affect. If not, the breakpoint in question may be removed and
4527 other breakpoints may be set which will have the desired behavior.
4528 E.g., it may be sufficient to place the breakpoint at a later
4529 instruction. A conditional breakpoint may also be useful in some
4530 cases to prevent the breakpoint from triggering too often.
4532 @value{GDBN} will also issue a warning when stopping at one of these
4533 adjusted breakpoints:
4536 warning: Breakpoint 1 address previously adjusted from 0x00010414
4540 When this warning is encountered, it may be too late to take remedial
4541 action except in cases where the breakpoint is hit earlier or more
4542 frequently than expected.
4544 @node Continuing and Stepping
4545 @section Continuing and Stepping
4549 @cindex resuming execution
4550 @dfn{Continuing} means resuming program execution until your program
4551 completes normally. In contrast, @dfn{stepping} means executing just
4552 one more ``step'' of your program, where ``step'' may mean either one
4553 line of source code, or one machine instruction (depending on what
4554 particular command you use). Either when continuing or when stepping,
4555 your program may stop even sooner, due to a breakpoint or a signal. (If
4556 it stops due to a signal, you may want to use @code{handle}, or use
4557 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4561 @kindex c @r{(@code{continue})}
4562 @kindex fg @r{(resume foreground execution)}
4563 @item continue @r{[}@var{ignore-count}@r{]}
4564 @itemx c @r{[}@var{ignore-count}@r{]}
4565 @itemx fg @r{[}@var{ignore-count}@r{]}
4566 Resume program execution, at the address where your program last stopped;
4567 any breakpoints set at that address are bypassed. The optional argument
4568 @var{ignore-count} allows you to specify a further number of times to
4569 ignore a breakpoint at this location; its effect is like that of
4570 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4572 The argument @var{ignore-count} is meaningful only when your program
4573 stopped due to a breakpoint. At other times, the argument to
4574 @code{continue} is ignored.
4576 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4577 debugged program is deemed to be the foreground program) are provided
4578 purely for convenience, and have exactly the same behavior as
4582 To resume execution at a different place, you can use @code{return}
4583 (@pxref{Returning, ,Returning from a Function}) to go back to the
4584 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4585 Different Address}) to go to an arbitrary location in your program.
4587 A typical technique for using stepping is to set a breakpoint
4588 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4589 beginning of the function or the section of your program where a problem
4590 is believed to lie, run your program until it stops at that breakpoint,
4591 and then step through the suspect area, examining the variables that are
4592 interesting, until you see the problem happen.
4596 @kindex s @r{(@code{step})}
4598 Continue running your program until control reaches a different source
4599 line, then stop it and return control to @value{GDBN}. This command is
4600 abbreviated @code{s}.
4603 @c "without debugging information" is imprecise; actually "without line
4604 @c numbers in the debugging information". (gcc -g1 has debugging info but
4605 @c not line numbers). But it seems complex to try to make that
4606 @c distinction here.
4607 @emph{Warning:} If you use the @code{step} command while control is
4608 within a function that was compiled without debugging information,
4609 execution proceeds until control reaches a function that does have
4610 debugging information. Likewise, it will not step into a function which
4611 is compiled without debugging information. To step through functions
4612 without debugging information, use the @code{stepi} command, described
4616 The @code{step} command only stops at the first instruction of a source
4617 line. This prevents the multiple stops that could otherwise occur in
4618 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4619 to stop if a function that has debugging information is called within
4620 the line. In other words, @code{step} @emph{steps inside} any functions
4621 called within the line.
4623 Also, the @code{step} command only enters a function if there is line
4624 number information for the function. Otherwise it acts like the
4625 @code{next} command. This avoids problems when using @code{cc -gl}
4626 on MIPS machines. Previously, @code{step} entered subroutines if there
4627 was any debugging information about the routine.
4629 @item step @var{count}
4630 Continue running as in @code{step}, but do so @var{count} times. If a
4631 breakpoint is reached, or a signal not related to stepping occurs before
4632 @var{count} steps, stepping stops right away.
4635 @kindex n @r{(@code{next})}
4636 @item next @r{[}@var{count}@r{]}
4637 Continue to the next source line in the current (innermost) stack frame.
4638 This is similar to @code{step}, but function calls that appear within
4639 the line of code are executed without stopping. Execution stops when
4640 control reaches a different line of code at the original stack level
4641 that was executing when you gave the @code{next} command. This command
4642 is abbreviated @code{n}.
4644 An argument @var{count} is a repeat count, as for @code{step}.
4647 @c FIX ME!! Do we delete this, or is there a way it fits in with
4648 @c the following paragraph? --- Vctoria
4650 @c @code{next} within a function that lacks debugging information acts like
4651 @c @code{step}, but any function calls appearing within the code of the
4652 @c function are executed without stopping.
4654 The @code{next} command only stops at the first instruction of a
4655 source line. This prevents multiple stops that could otherwise occur in
4656 @code{switch} statements, @code{for} loops, etc.
4658 @kindex set step-mode
4660 @cindex functions without line info, and stepping
4661 @cindex stepping into functions with no line info
4662 @itemx set step-mode on
4663 The @code{set step-mode on} command causes the @code{step} command to
4664 stop at the first instruction of a function which contains no debug line
4665 information rather than stepping over it.
4667 This is useful in cases where you may be interested in inspecting the
4668 machine instructions of a function which has no symbolic info and do not
4669 want @value{GDBN} to automatically skip over this function.
4671 @item set step-mode off
4672 Causes the @code{step} command to step over any functions which contains no
4673 debug information. This is the default.
4675 @item show step-mode
4676 Show whether @value{GDBN} will stop in or step over functions without
4677 source line debug information.
4680 @kindex fin @r{(@code{finish})}
4682 Continue running until just after function in the selected stack frame
4683 returns. Print the returned value (if any). This command can be
4684 abbreviated as @code{fin}.
4686 Contrast this with the @code{return} command (@pxref{Returning,
4687 ,Returning from a Function}).
4690 @kindex u @r{(@code{until})}
4691 @cindex run until specified location
4694 Continue running until a source line past the current line, in the
4695 current stack frame, is reached. This command is used to avoid single
4696 stepping through a loop more than once. It is like the @code{next}
4697 command, except that when @code{until} encounters a jump, it
4698 automatically continues execution until the program counter is greater
4699 than the address of the jump.
4701 This means that when you reach the end of a loop after single stepping
4702 though it, @code{until} makes your program continue execution until it
4703 exits the loop. In contrast, a @code{next} command at the end of a loop
4704 simply steps back to the beginning of the loop, which forces you to step
4705 through the next iteration.
4707 @code{until} always stops your program if it attempts to exit the current
4710 @code{until} may produce somewhat counterintuitive results if the order
4711 of machine code does not match the order of the source lines. For
4712 example, in the following excerpt from a debugging session, the @code{f}
4713 (@code{frame}) command shows that execution is stopped at line
4714 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4718 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4720 (@value{GDBP}) until
4721 195 for ( ; argc > 0; NEXTARG) @{
4724 This happened because, for execution efficiency, the compiler had
4725 generated code for the loop closure test at the end, rather than the
4726 start, of the loop---even though the test in a C @code{for}-loop is
4727 written before the body of the loop. The @code{until} command appeared
4728 to step back to the beginning of the loop when it advanced to this
4729 expression; however, it has not really gone to an earlier
4730 statement---not in terms of the actual machine code.
4732 @code{until} with no argument works by means of single
4733 instruction stepping, and hence is slower than @code{until} with an
4736 @item until @var{location}
4737 @itemx u @var{location}
4738 Continue running your program until either the specified location is
4739 reached, or the current stack frame returns. @var{location} is any of
4740 the forms described in @ref{Specify Location}.
4741 This form of the command uses temporary breakpoints, and
4742 hence is quicker than @code{until} without an argument. The specified
4743 location is actually reached only if it is in the current frame. This
4744 implies that @code{until} can be used to skip over recursive function
4745 invocations. For instance in the code below, if the current location is
4746 line @code{96}, issuing @code{until 99} will execute the program up to
4747 line @code{99} in the same invocation of factorial, i.e., after the inner
4748 invocations have returned.
4751 94 int factorial (int value)
4753 96 if (value > 1) @{
4754 97 value *= factorial (value - 1);
4761 @kindex advance @var{location}
4762 @itemx advance @var{location}
4763 Continue running the program up to the given @var{location}. An argument is
4764 required, which should be of one of the forms described in
4765 @ref{Specify Location}.
4766 Execution will also stop upon exit from the current stack
4767 frame. This command is similar to @code{until}, but @code{advance} will
4768 not skip over recursive function calls, and the target location doesn't
4769 have to be in the same frame as the current one.
4773 @kindex si @r{(@code{stepi})}
4775 @itemx stepi @var{arg}
4777 Execute one machine instruction, then stop and return to the debugger.
4779 It is often useful to do @samp{display/i $pc} when stepping by machine
4780 instructions. This makes @value{GDBN} automatically display the next
4781 instruction to be executed, each time your program stops. @xref{Auto
4782 Display,, Automatic Display}.
4784 An argument is a repeat count, as in @code{step}.
4788 @kindex ni @r{(@code{nexti})}
4790 @itemx nexti @var{arg}
4792 Execute one machine instruction, but if it is a function call,
4793 proceed until the function returns.
4795 An argument is a repeat count, as in @code{next}.
4802 A signal is an asynchronous event that can happen in a program. The
4803 operating system defines the possible kinds of signals, and gives each
4804 kind a name and a number. For example, in Unix @code{SIGINT} is the
4805 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4806 @code{SIGSEGV} is the signal a program gets from referencing a place in
4807 memory far away from all the areas in use; @code{SIGALRM} occurs when
4808 the alarm clock timer goes off (which happens only if your program has
4809 requested an alarm).
4811 @cindex fatal signals
4812 Some signals, including @code{SIGALRM}, are a normal part of the
4813 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4814 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4815 program has not specified in advance some other way to handle the signal.
4816 @code{SIGINT} does not indicate an error in your program, but it is normally
4817 fatal so it can carry out the purpose of the interrupt: to kill the program.
4819 @value{GDBN} has the ability to detect any occurrence of a signal in your
4820 program. You can tell @value{GDBN} in advance what to do for each kind of
4823 @cindex handling signals
4824 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4825 @code{SIGALRM} be silently passed to your program
4826 (so as not to interfere with their role in the program's functioning)
4827 but to stop your program immediately whenever an error signal happens.
4828 You can change these settings with the @code{handle} command.
4831 @kindex info signals
4835 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4836 handle each one. You can use this to see the signal numbers of all
4837 the defined types of signals.
4839 @item info signals @var{sig}
4840 Similar, but print information only about the specified signal number.
4842 @code{info handle} is an alias for @code{info signals}.
4845 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4846 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4847 can be the number of a signal or its name (with or without the
4848 @samp{SIG} at the beginning); a list of signal numbers of the form
4849 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4850 known signals. Optional arguments @var{keywords}, described below,
4851 say what change to make.
4855 The keywords allowed by the @code{handle} command can be abbreviated.
4856 Their full names are:
4860 @value{GDBN} should not stop your program when this signal happens. It may
4861 still print a message telling you that the signal has come in.
4864 @value{GDBN} should stop your program when this signal happens. This implies
4865 the @code{print} keyword as well.
4868 @value{GDBN} should print a message when this signal happens.
4871 @value{GDBN} should not mention the occurrence of the signal at all. This
4872 implies the @code{nostop} keyword as well.
4876 @value{GDBN} should allow your program to see this signal; your program
4877 can handle the signal, or else it may terminate if the signal is fatal
4878 and not handled. @code{pass} and @code{noignore} are synonyms.
4882 @value{GDBN} should not allow your program to see this signal.
4883 @code{nopass} and @code{ignore} are synonyms.
4887 When a signal stops your program, the signal is not visible to the
4889 continue. Your program sees the signal then, if @code{pass} is in
4890 effect for the signal in question @emph{at that time}. In other words,
4891 after @value{GDBN} reports a signal, you can use the @code{handle}
4892 command with @code{pass} or @code{nopass} to control whether your
4893 program sees that signal when you continue.
4895 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4896 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4897 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4900 You can also use the @code{signal} command to prevent your program from
4901 seeing a signal, or cause it to see a signal it normally would not see,
4902 or to give it any signal at any time. For example, if your program stopped
4903 due to some sort of memory reference error, you might store correct
4904 values into the erroneous variables and continue, hoping to see more
4905 execution; but your program would probably terminate immediately as
4906 a result of the fatal signal once it saw the signal. To prevent this,
4907 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4910 @cindex extra signal information
4911 @anchor{extra signal information}
4913 On some targets, @value{GDBN} can inspect extra signal information
4914 associated with the intercepted signal, before it is actually
4915 delivered to the program being debugged. This information is exported
4916 by the convenience variable @code{$_siginfo}, and consists of data
4917 that is passed by the kernel to the signal handler at the time of the
4918 receipt of a signal. The data type of the information itself is
4919 target dependent. You can see the data type using the @code{ptype
4920 $_siginfo} command. On Unix systems, it typically corresponds to the
4921 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4924 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4925 referenced address that raised a segmentation fault.
4929 (@value{GDBP}) continue
4930 Program received signal SIGSEGV, Segmentation fault.
4931 0x0000000000400766 in main ()
4933 (@value{GDBP}) ptype $_siginfo
4940 struct @{...@} _kill;
4941 struct @{...@} _timer;
4943 struct @{...@} _sigchld;
4944 struct @{...@} _sigfault;
4945 struct @{...@} _sigpoll;
4948 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4952 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4953 $1 = (void *) 0x7ffff7ff7000
4957 Depending on target support, @code{$_siginfo} may also be writable.
4960 @section Stopping and Starting Multi-thread Programs
4962 @cindex stopped threads
4963 @cindex threads, stopped
4965 @cindex continuing threads
4966 @cindex threads, continuing
4968 @value{GDBN} supports debugging programs with multiple threads
4969 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4970 are two modes of controlling execution of your program within the
4971 debugger. In the default mode, referred to as @dfn{all-stop mode},
4972 when any thread in your program stops (for example, at a breakpoint
4973 or while being stepped), all other threads in the program are also stopped by
4974 @value{GDBN}. On some targets, @value{GDBN} also supports
4975 @dfn{non-stop mode}, in which other threads can continue to run freely while
4976 you examine the stopped thread in the debugger.
4979 * All-Stop Mode:: All threads stop when GDB takes control
4980 * Non-Stop Mode:: Other threads continue to execute
4981 * Background Execution:: Running your program asynchronously
4982 * Thread-Specific Breakpoints:: Controlling breakpoints
4983 * Interrupted System Calls:: GDB may interfere with system calls
4984 * Observer Mode:: GDB does not alter program behavior
4988 @subsection All-Stop Mode
4990 @cindex all-stop mode
4992 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4993 @emph{all} threads of execution stop, not just the current thread. This
4994 allows you to examine the overall state of the program, including
4995 switching between threads, without worrying that things may change
4998 Conversely, whenever you restart the program, @emph{all} threads start
4999 executing. @emph{This is true even when single-stepping} with commands
5000 like @code{step} or @code{next}.
5002 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5003 Since thread scheduling is up to your debugging target's operating
5004 system (not controlled by @value{GDBN}), other threads may
5005 execute more than one statement while the current thread completes a
5006 single step. Moreover, in general other threads stop in the middle of a
5007 statement, rather than at a clean statement boundary, when the program
5010 You might even find your program stopped in another thread after
5011 continuing or even single-stepping. This happens whenever some other
5012 thread runs into a breakpoint, a signal, or an exception before the
5013 first thread completes whatever you requested.
5015 @cindex automatic thread selection
5016 @cindex switching threads automatically
5017 @cindex threads, automatic switching
5018 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5019 signal, it automatically selects the thread where that breakpoint or
5020 signal happened. @value{GDBN} alerts you to the context switch with a
5021 message such as @samp{[Switching to Thread @var{n}]} to identify the
5024 On some OSes, you can modify @value{GDBN}'s default behavior by
5025 locking the OS scheduler to allow only a single thread to run.
5028 @item set scheduler-locking @var{mode}
5029 @cindex scheduler locking mode
5030 @cindex lock scheduler
5031 Set the scheduler locking mode. If it is @code{off}, then there is no
5032 locking and any thread may run at any time. If @code{on}, then only the
5033 current thread may run when the inferior is resumed. The @code{step}
5034 mode optimizes for single-stepping; it prevents other threads
5035 from preempting the current thread while you are stepping, so that
5036 the focus of debugging does not change unexpectedly.
5037 Other threads only rarely (or never) get a chance to run
5038 when you step. They are more likely to run when you @samp{next} over a
5039 function call, and they are completely free to run when you use commands
5040 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5041 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5042 the current thread away from the thread that you are debugging.
5044 @item show scheduler-locking
5045 Display the current scheduler locking mode.
5048 @cindex resume threads of multiple processes simultaneously
5049 By default, when you issue one of the execution commands such as
5050 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5051 threads of the current inferior to run. For example, if @value{GDBN}
5052 is attached to two inferiors, each with two threads, the
5053 @code{continue} command resumes only the two threads of the current
5054 inferior. This is useful, for example, when you debug a program that
5055 forks and you want to hold the parent stopped (so that, for instance,
5056 it doesn't run to exit), while you debug the child. In other
5057 situations, you may not be interested in inspecting the current state
5058 of any of the processes @value{GDBN} is attached to, and you may want
5059 to resume them all until some breakpoint is hit. In the latter case,
5060 you can instruct @value{GDBN} to allow all threads of all the
5061 inferiors to run with the @w{@code{set schedule-multiple}} command.
5064 @kindex set schedule-multiple
5065 @item set schedule-multiple
5066 Set the mode for allowing threads of multiple processes to be resumed
5067 when an execution command is issued. When @code{on}, all threads of
5068 all processes are allowed to run. When @code{off}, only the threads
5069 of the current process are resumed. The default is @code{off}. The
5070 @code{scheduler-locking} mode takes precedence when set to @code{on},
5071 or while you are stepping and set to @code{step}.
5073 @item show schedule-multiple
5074 Display the current mode for resuming the execution of threads of
5079 @subsection Non-Stop Mode
5081 @cindex non-stop mode
5083 @c This section is really only a place-holder, and needs to be expanded
5084 @c with more details.
5086 For some multi-threaded targets, @value{GDBN} supports an optional
5087 mode of operation in which you can examine stopped program threads in
5088 the debugger while other threads continue to execute freely. This
5089 minimizes intrusion when debugging live systems, such as programs
5090 where some threads have real-time constraints or must continue to
5091 respond to external events. This is referred to as @dfn{non-stop} mode.
5093 In non-stop mode, when a thread stops to report a debugging event,
5094 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5095 threads as well, in contrast to the all-stop mode behavior. Additionally,
5096 execution commands such as @code{continue} and @code{step} apply by default
5097 only to the current thread in non-stop mode, rather than all threads as
5098 in all-stop mode. This allows you to control threads explicitly in
5099 ways that are not possible in all-stop mode --- for example, stepping
5100 one thread while allowing others to run freely, stepping
5101 one thread while holding all others stopped, or stepping several threads
5102 independently and simultaneously.
5104 To enter non-stop mode, use this sequence of commands before you run
5105 or attach to your program:
5108 # Enable the async interface.
5111 # If using the CLI, pagination breaks non-stop.
5114 # Finally, turn it on!
5118 You can use these commands to manipulate the non-stop mode setting:
5121 @kindex set non-stop
5122 @item set non-stop on
5123 Enable selection of non-stop mode.
5124 @item set non-stop off
5125 Disable selection of non-stop mode.
5126 @kindex show non-stop
5128 Show the current non-stop enablement setting.
5131 Note these commands only reflect whether non-stop mode is enabled,
5132 not whether the currently-executing program is being run in non-stop mode.
5133 In particular, the @code{set non-stop} preference is only consulted when
5134 @value{GDBN} starts or connects to the target program, and it is generally
5135 not possible to switch modes once debugging has started. Furthermore,
5136 since not all targets support non-stop mode, even when you have enabled
5137 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5140 In non-stop mode, all execution commands apply only to the current thread
5141 by default. That is, @code{continue} only continues one thread.
5142 To continue all threads, issue @code{continue -a} or @code{c -a}.
5144 You can use @value{GDBN}'s background execution commands
5145 (@pxref{Background Execution}) to run some threads in the background
5146 while you continue to examine or step others from @value{GDBN}.
5147 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5148 always executed asynchronously in non-stop mode.
5150 Suspending execution is done with the @code{interrupt} command when
5151 running in the background, or @kbd{Ctrl-c} during foreground execution.
5152 In all-stop mode, this stops the whole process;
5153 but in non-stop mode the interrupt applies only to the current thread.
5154 To stop the whole program, use @code{interrupt -a}.
5156 Other execution commands do not currently support the @code{-a} option.
5158 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5159 that thread current, as it does in all-stop mode. This is because the
5160 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5161 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5162 changed to a different thread just as you entered a command to operate on the
5163 previously current thread.
5165 @node Background Execution
5166 @subsection Background Execution
5168 @cindex foreground execution
5169 @cindex background execution
5170 @cindex asynchronous execution
5171 @cindex execution, foreground, background and asynchronous
5173 @value{GDBN}'s execution commands have two variants: the normal
5174 foreground (synchronous) behavior, and a background
5175 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5176 the program to report that some thread has stopped before prompting for
5177 another command. In background execution, @value{GDBN} immediately gives
5178 a command prompt so that you can issue other commands while your program runs.
5180 You need to explicitly enable asynchronous mode before you can use
5181 background execution commands. You can use these commands to
5182 manipulate the asynchronous mode setting:
5185 @kindex set target-async
5186 @item set target-async on
5187 Enable asynchronous mode.
5188 @item set target-async off
5189 Disable asynchronous mode.
5190 @kindex show target-async
5191 @item show target-async
5192 Show the current target-async setting.
5195 If the target doesn't support async mode, @value{GDBN} issues an error
5196 message if you attempt to use the background execution commands.
5198 To specify background execution, add a @code{&} to the command. For example,
5199 the background form of the @code{continue} command is @code{continue&}, or
5200 just @code{c&}. The execution commands that accept background execution
5206 @xref{Starting, , Starting your Program}.
5210 @xref{Attach, , Debugging an Already-running Process}.
5214 @xref{Continuing and Stepping, step}.
5218 @xref{Continuing and Stepping, stepi}.
5222 @xref{Continuing and Stepping, next}.
5226 @xref{Continuing and Stepping, nexti}.
5230 @xref{Continuing and Stepping, continue}.
5234 @xref{Continuing and Stepping, finish}.
5238 @xref{Continuing and Stepping, until}.
5242 Background execution is especially useful in conjunction with non-stop
5243 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5244 However, you can also use these commands in the normal all-stop mode with
5245 the restriction that you cannot issue another execution command until the
5246 previous one finishes. Examples of commands that are valid in all-stop
5247 mode while the program is running include @code{help} and @code{info break}.
5249 You can interrupt your program while it is running in the background by
5250 using the @code{interrupt} command.
5257 Suspend execution of the running program. In all-stop mode,
5258 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5259 only the current thread. To stop the whole program in non-stop mode,
5260 use @code{interrupt -a}.
5263 @node Thread-Specific Breakpoints
5264 @subsection Thread-Specific Breakpoints
5266 When your program has multiple threads (@pxref{Threads,, Debugging
5267 Programs with Multiple Threads}), you can choose whether to set
5268 breakpoints on all threads, or on a particular thread.
5271 @cindex breakpoints and threads
5272 @cindex thread breakpoints
5273 @kindex break @dots{} thread @var{threadno}
5274 @item break @var{linespec} thread @var{threadno}
5275 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5276 @var{linespec} specifies source lines; there are several ways of
5277 writing them (@pxref{Specify Location}), but the effect is always to
5278 specify some source line.
5280 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5281 to specify that you only want @value{GDBN} to stop the program when a
5282 particular thread reaches this breakpoint. @var{threadno} is one of the
5283 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5284 column of the @samp{info threads} display.
5286 If you do not specify @samp{thread @var{threadno}} when you set a
5287 breakpoint, the breakpoint applies to @emph{all} threads of your
5290 You can use the @code{thread} qualifier on conditional breakpoints as
5291 well; in this case, place @samp{thread @var{threadno}} before or
5292 after the breakpoint condition, like this:
5295 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5300 @node Interrupted System Calls
5301 @subsection Interrupted System Calls
5303 @cindex thread breakpoints and system calls
5304 @cindex system calls and thread breakpoints
5305 @cindex premature return from system calls
5306 There is an unfortunate side effect when using @value{GDBN} to debug
5307 multi-threaded programs. If one thread stops for a
5308 breakpoint, or for some other reason, and another thread is blocked in a
5309 system call, then the system call may return prematurely. This is a
5310 consequence of the interaction between multiple threads and the signals
5311 that @value{GDBN} uses to implement breakpoints and other events that
5314 To handle this problem, your program should check the return value of
5315 each system call and react appropriately. This is good programming
5318 For example, do not write code like this:
5324 The call to @code{sleep} will return early if a different thread stops
5325 at a breakpoint or for some other reason.
5327 Instead, write this:
5332 unslept = sleep (unslept);
5335 A system call is allowed to return early, so the system is still
5336 conforming to its specification. But @value{GDBN} does cause your
5337 multi-threaded program to behave differently than it would without
5340 Also, @value{GDBN} uses internal breakpoints in the thread library to
5341 monitor certain events such as thread creation and thread destruction.
5342 When such an event happens, a system call in another thread may return
5343 prematurely, even though your program does not appear to stop.
5346 @subsection Observer Mode
5348 If you want to build on non-stop mode and observe program behavior
5349 without any chance of disruption by @value{GDBN}, you can set
5350 variables to disable all of the debugger's attempts to modify state,
5351 whether by writing memory, inserting breakpoints, etc. These operate
5352 at a low level, intercepting operations from all commands.
5354 When all of these are set to @code{off}, then @value{GDBN} is said to
5355 be @dfn{observer mode}. As a convenience, the variable
5356 @code{observer} can be set to disable these, plus enable non-stop
5359 Note that @value{GDBN} will not prevent you from making nonsensical
5360 combinations of these settings. For instance, if you have enabled
5361 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5362 then breakpoints that work by writing trap instructions into the code
5363 stream will still not be able to be placed.
5368 @item set observer on
5369 @itemx set observer off
5370 When set to @code{on}, this disables all the permission variables
5371 below (except for @code{insert-fast-tracepoints}), plus enables
5372 non-stop debugging. Setting this to @code{off} switches back to
5373 normal debugging, though remaining in non-stop mode.
5376 Show whether observer mode is on or off.
5378 @kindex may-write-registers
5379 @item set may-write-registers on
5380 @itemx set may-write-registers off
5381 This controls whether @value{GDBN} will attempt to alter the values of
5382 registers, such as with assignment expressions in @code{print}, or the
5383 @code{jump} command. It defaults to @code{on}.
5385 @item show may-write-registers
5386 Show the current permission to write registers.
5388 @kindex may-write-memory
5389 @item set may-write-memory on
5390 @itemx set may-write-memory off
5391 This controls whether @value{GDBN} will attempt to alter the contents
5392 of memory, such as with assignment expressions in @code{print}. It
5393 defaults to @code{on}.
5395 @item show may-write-memory
5396 Show the current permission to write memory.
5398 @kindex may-insert-breakpoints
5399 @item set may-insert-breakpoints on
5400 @itemx set may-insert-breakpoints off
5401 This controls whether @value{GDBN} will attempt to insert breakpoints.
5402 This affects all breakpoints, including internal breakpoints defined
5403 by @value{GDBN}. It defaults to @code{on}.
5405 @item show may-insert-breakpoints
5406 Show the current permission to insert breakpoints.
5408 @kindex may-insert-tracepoints
5409 @item set may-insert-tracepoints on
5410 @itemx set may-insert-tracepoints off
5411 This controls whether @value{GDBN} will attempt to insert (regular)
5412 tracepoints at the beginning of a tracing experiment. It affects only
5413 non-fast tracepoints, fast tracepoints being under the control of
5414 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5416 @item show may-insert-tracepoints
5417 Show the current permission to insert tracepoints.
5419 @kindex may-insert-fast-tracepoints
5420 @item set may-insert-fast-tracepoints on
5421 @itemx set may-insert-fast-tracepoints off
5422 This controls whether @value{GDBN} will attempt to insert fast
5423 tracepoints at the beginning of a tracing experiment. It affects only
5424 fast tracepoints, regular (non-fast) tracepoints being under the
5425 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5427 @item show may-insert-fast-tracepoints
5428 Show the current permission to insert fast tracepoints.
5430 @kindex may-interrupt
5431 @item set may-interrupt on
5432 @itemx set may-interrupt off
5433 This controls whether @value{GDBN} will attempt to interrupt or stop
5434 program execution. When this variable is @code{off}, the
5435 @code{interrupt} command will have no effect, nor will
5436 @kbd{Ctrl-c}. It defaults to @code{on}.
5438 @item show may-interrupt
5439 Show the current permission to interrupt or stop the program.
5443 @node Reverse Execution
5444 @chapter Running programs backward
5445 @cindex reverse execution
5446 @cindex running programs backward
5448 When you are debugging a program, it is not unusual to realize that
5449 you have gone too far, and some event of interest has already happened.
5450 If the target environment supports it, @value{GDBN} can allow you to
5451 ``rewind'' the program by running it backward.
5453 A target environment that supports reverse execution should be able
5454 to ``undo'' the changes in machine state that have taken place as the
5455 program was executing normally. Variables, registers etc.@: should
5456 revert to their previous values. Obviously this requires a great
5457 deal of sophistication on the part of the target environment; not
5458 all target environments can support reverse execution.
5460 When a program is executed in reverse, the instructions that
5461 have most recently been executed are ``un-executed'', in reverse
5462 order. The program counter runs backward, following the previous
5463 thread of execution in reverse. As each instruction is ``un-executed'',
5464 the values of memory and/or registers that were changed by that
5465 instruction are reverted to their previous states. After executing
5466 a piece of source code in reverse, all side effects of that code
5467 should be ``undone'', and all variables should be returned to their
5468 prior values@footnote{
5469 Note that some side effects are easier to undo than others. For instance,
5470 memory and registers are relatively easy, but device I/O is hard. Some
5471 targets may be able undo things like device I/O, and some may not.
5473 The contract between @value{GDBN} and the reverse executing target
5474 requires only that the target do something reasonable when
5475 @value{GDBN} tells it to execute backwards, and then report the
5476 results back to @value{GDBN}. Whatever the target reports back to
5477 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5478 assumes that the memory and registers that the target reports are in a
5479 consistant state, but @value{GDBN} accepts whatever it is given.
5482 If you are debugging in a target environment that supports
5483 reverse execution, @value{GDBN} provides the following commands.
5486 @kindex reverse-continue
5487 @kindex rc @r{(@code{reverse-continue})}
5488 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5489 @itemx rc @r{[}@var{ignore-count}@r{]}
5490 Beginning at the point where your program last stopped, start executing
5491 in reverse. Reverse execution will stop for breakpoints and synchronous
5492 exceptions (signals), just like normal execution. Behavior of
5493 asynchronous signals depends on the target environment.
5495 @kindex reverse-step
5496 @kindex rs @r{(@code{step})}
5497 @item reverse-step @r{[}@var{count}@r{]}
5498 Run the program backward until control reaches the start of a
5499 different source line; then stop it, and return control to @value{GDBN}.
5501 Like the @code{step} command, @code{reverse-step} will only stop
5502 at the beginning of a source line. It ``un-executes'' the previously
5503 executed source line. If the previous source line included calls to
5504 debuggable functions, @code{reverse-step} will step (backward) into
5505 the called function, stopping at the beginning of the @emph{last}
5506 statement in the called function (typically a return statement).
5508 Also, as with the @code{step} command, if non-debuggable functions are
5509 called, @code{reverse-step} will run thru them backward without stopping.
5511 @kindex reverse-stepi
5512 @kindex rsi @r{(@code{reverse-stepi})}
5513 @item reverse-stepi @r{[}@var{count}@r{]}
5514 Reverse-execute one machine instruction. Note that the instruction
5515 to be reverse-executed is @emph{not} the one pointed to by the program
5516 counter, but the instruction executed prior to that one. For instance,
5517 if the last instruction was a jump, @code{reverse-stepi} will take you
5518 back from the destination of the jump to the jump instruction itself.
5520 @kindex reverse-next
5521 @kindex rn @r{(@code{reverse-next})}
5522 @item reverse-next @r{[}@var{count}@r{]}
5523 Run backward to the beginning of the previous line executed in
5524 the current (innermost) stack frame. If the line contains function
5525 calls, they will be ``un-executed'' without stopping. Starting from
5526 the first line of a function, @code{reverse-next} will take you back
5527 to the caller of that function, @emph{before} the function was called,
5528 just as the normal @code{next} command would take you from the last
5529 line of a function back to its return to its caller
5530 @footnote{Unless the code is too heavily optimized.}.
5532 @kindex reverse-nexti
5533 @kindex rni @r{(@code{reverse-nexti})}
5534 @item reverse-nexti @r{[}@var{count}@r{]}
5535 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5536 in reverse, except that called functions are ``un-executed'' atomically.
5537 That is, if the previously executed instruction was a return from
5538 another function, @code{reverse-nexti} will continue to execute
5539 in reverse until the call to that function (from the current stack
5542 @kindex reverse-finish
5543 @item reverse-finish
5544 Just as the @code{finish} command takes you to the point where the
5545 current function returns, @code{reverse-finish} takes you to the point
5546 where it was called. Instead of ending up at the end of the current
5547 function invocation, you end up at the beginning.
5549 @kindex set exec-direction
5550 @item set exec-direction
5551 Set the direction of target execution.
5552 @itemx set exec-direction reverse
5553 @cindex execute forward or backward in time
5554 @value{GDBN} will perform all execution commands in reverse, until the
5555 exec-direction mode is changed to ``forward''. Affected commands include
5556 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5557 command cannot be used in reverse mode.
5558 @item set exec-direction forward
5559 @value{GDBN} will perform all execution commands in the normal fashion.
5560 This is the default.
5564 @node Process Record and Replay
5565 @chapter Recording Inferior's Execution and Replaying It
5566 @cindex process record and replay
5567 @cindex recording inferior's execution and replaying it
5569 On some platforms, @value{GDBN} provides a special @dfn{process record
5570 and replay} target that can record a log of the process execution, and
5571 replay it later with both forward and reverse execution commands.
5574 When this target is in use, if the execution log includes the record
5575 for the next instruction, @value{GDBN} will debug in @dfn{replay
5576 mode}. In the replay mode, the inferior does not really execute code
5577 instructions. Instead, all the events that normally happen during
5578 code execution are taken from the execution log. While code is not
5579 really executed in replay mode, the values of registers (including the
5580 program counter register) and the memory of the inferior are still
5581 changed as they normally would. Their contents are taken from the
5585 If the record for the next instruction is not in the execution log,
5586 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5587 inferior executes normally, and @value{GDBN} records the execution log
5590 The process record and replay target supports reverse execution
5591 (@pxref{Reverse Execution}), even if the platform on which the
5592 inferior runs does not. However, the reverse execution is limited in
5593 this case by the range of the instructions recorded in the execution
5594 log. In other words, reverse execution on platforms that don't
5595 support it directly can only be done in the replay mode.
5597 When debugging in the reverse direction, @value{GDBN} will work in
5598 replay mode as long as the execution log includes the record for the
5599 previous instruction; otherwise, it will work in record mode, if the
5600 platform supports reverse execution, or stop if not.
5602 For architecture environments that support process record and replay,
5603 @value{GDBN} provides the following commands:
5606 @kindex target record
5610 This command starts the process record and replay target. The process
5611 record and replay target can only debug a process that is already
5612 running. Therefore, you need first to start the process with the
5613 @kbd{run} or @kbd{start} commands, and then start the recording with
5614 the @kbd{target record} command.
5616 Both @code{record} and @code{rec} are aliases of @code{target record}.
5618 @cindex displaced stepping, and process record and replay
5619 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5620 will be automatically disabled when process record and replay target
5621 is started. That's because the process record and replay target
5622 doesn't support displaced stepping.
5624 @cindex non-stop mode, and process record and replay
5625 @cindex asynchronous execution, and process record and replay
5626 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5627 the asynchronous execution mode (@pxref{Background Execution}), the
5628 process record and replay target cannot be started because it doesn't
5629 support these two modes.
5634 Stop the process record and replay target. When process record and
5635 replay target stops, the entire execution log will be deleted and the
5636 inferior will either be terminated, or will remain in its final state.
5638 When you stop the process record and replay target in record mode (at
5639 the end of the execution log), the inferior will be stopped at the
5640 next instruction that would have been recorded. In other words, if
5641 you record for a while and then stop recording, the inferior process
5642 will be left in the same state as if the recording never happened.
5644 On the other hand, if the process record and replay target is stopped
5645 while in replay mode (that is, not at the end of the execution log,
5646 but at some earlier point), the inferior process will become ``live''
5647 at that earlier state, and it will then be possible to continue the
5648 usual ``live'' debugging of the process from that state.
5650 When the inferior process exits, or @value{GDBN} detaches from it,
5651 process record and replay target will automatically stop itself.
5654 @item record save @var{filename}
5655 Save the execution log to a file @file{@var{filename}}.
5656 Default filename is @file{gdb_record.@var{process_id}}, where
5657 @var{process_id} is the process ID of the inferior.
5659 @kindex record restore
5660 @item record restore @var{filename}
5661 Restore the execution log from a file @file{@var{filename}}.
5662 File must have been created with @code{record save}.
5664 @kindex set record insn-number-max
5665 @item set record insn-number-max @var{limit}
5666 Set the limit of instructions to be recorded. Default value is 200000.
5668 If @var{limit} is a positive number, then @value{GDBN} will start
5669 deleting instructions from the log once the number of the record
5670 instructions becomes greater than @var{limit}. For every new recorded
5671 instruction, @value{GDBN} will delete the earliest recorded
5672 instruction to keep the number of recorded instructions at the limit.
5673 (Since deleting recorded instructions loses information, @value{GDBN}
5674 lets you control what happens when the limit is reached, by means of
5675 the @code{stop-at-limit} option, described below.)
5677 If @var{limit} is zero, @value{GDBN} will never delete recorded
5678 instructions from the execution log. The number of recorded
5679 instructions is unlimited in this case.
5681 @kindex show record insn-number-max
5682 @item show record insn-number-max
5683 Show the limit of instructions to be recorded.
5685 @kindex set record stop-at-limit
5686 @item set record stop-at-limit
5687 Control the behavior when the number of recorded instructions reaches
5688 the limit. If ON (the default), @value{GDBN} will stop when the limit
5689 is reached for the first time and ask you whether you want to stop the
5690 inferior or continue running it and recording the execution log. If
5691 you decide to continue recording, each new recorded instruction will
5692 cause the oldest one to be deleted.
5694 If this option is OFF, @value{GDBN} will automatically delete the
5695 oldest record to make room for each new one, without asking.
5697 @kindex show record stop-at-limit
5698 @item show record stop-at-limit
5699 Show the current setting of @code{stop-at-limit}.
5701 @kindex set record memory-query
5702 @item set record memory-query
5703 Control the behavior when @value{GDBN} is unable to record memory
5704 changes caused by an instruction. If ON, @value{GDBN} will query
5705 whether to stop the inferior in that case.
5707 If this option is OFF (the default), @value{GDBN} will automatically
5708 ignore the effect of such instructions on memory. Later, when
5709 @value{GDBN} replays this execution log, it will mark the log of this
5710 instruction as not accessible, and it will not affect the replay
5713 @kindex show record memory-query
5714 @item show record memory-query
5715 Show the current setting of @code{memory-query}.
5719 Show various statistics about the state of process record and its
5720 in-memory execution log buffer, including:
5724 Whether in record mode or replay mode.
5726 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5728 Highest recorded instruction number.
5730 Current instruction about to be replayed (if in replay mode).
5732 Number of instructions contained in the execution log.
5734 Maximum number of instructions that may be contained in the execution log.
5737 @kindex record delete
5740 When record target runs in replay mode (``in the past''), delete the
5741 subsequent execution log and begin to record a new execution log starting
5742 from the current address. This means you will abandon the previously
5743 recorded ``future'' and begin recording a new ``future''.
5748 @chapter Examining the Stack
5750 When your program has stopped, the first thing you need to know is where it
5751 stopped and how it got there.
5754 Each time your program performs a function call, information about the call
5756 That information includes the location of the call in your program,
5757 the arguments of the call,
5758 and the local variables of the function being called.
5759 The information is saved in a block of data called a @dfn{stack frame}.
5760 The stack frames are allocated in a region of memory called the @dfn{call
5763 When your program stops, the @value{GDBN} commands for examining the
5764 stack allow you to see all of this information.
5766 @cindex selected frame
5767 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5768 @value{GDBN} commands refer implicitly to the selected frame. In
5769 particular, whenever you ask @value{GDBN} for the value of a variable in
5770 your program, the value is found in the selected frame. There are
5771 special @value{GDBN} commands to select whichever frame you are
5772 interested in. @xref{Selection, ,Selecting a Frame}.
5774 When your program stops, @value{GDBN} automatically selects the
5775 currently executing frame and describes it briefly, similar to the
5776 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5779 * Frames:: Stack frames
5780 * Backtrace:: Backtraces
5781 * Selection:: Selecting a frame
5782 * Frame Info:: Information on a frame
5787 @section Stack Frames
5789 @cindex frame, definition
5791 The call stack is divided up into contiguous pieces called @dfn{stack
5792 frames}, or @dfn{frames} for short; each frame is the data associated
5793 with one call to one function. The frame contains the arguments given
5794 to the function, the function's local variables, and the address at
5795 which the function is executing.
5797 @cindex initial frame
5798 @cindex outermost frame
5799 @cindex innermost frame
5800 When your program is started, the stack has only one frame, that of the
5801 function @code{main}. This is called the @dfn{initial} frame or the
5802 @dfn{outermost} frame. Each time a function is called, a new frame is
5803 made. Each time a function returns, the frame for that function invocation
5804 is eliminated. If a function is recursive, there can be many frames for
5805 the same function. The frame for the function in which execution is
5806 actually occurring is called the @dfn{innermost} frame. This is the most
5807 recently created of all the stack frames that still exist.
5809 @cindex frame pointer
5810 Inside your program, stack frames are identified by their addresses. A
5811 stack frame consists of many bytes, each of which has its own address; each
5812 kind of computer has a convention for choosing one byte whose
5813 address serves as the address of the frame. Usually this address is kept
5814 in a register called the @dfn{frame pointer register}
5815 (@pxref{Registers, $fp}) while execution is going on in that frame.
5817 @cindex frame number
5818 @value{GDBN} assigns numbers to all existing stack frames, starting with
5819 zero for the innermost frame, one for the frame that called it,
5820 and so on upward. These numbers do not really exist in your program;
5821 they are assigned by @value{GDBN} to give you a way of designating stack
5822 frames in @value{GDBN} commands.
5824 @c The -fomit-frame-pointer below perennially causes hbox overflow
5825 @c underflow problems.
5826 @cindex frameless execution
5827 Some compilers provide a way to compile functions so that they operate
5828 without stack frames. (For example, the @value{NGCC} option
5830 @samp{-fomit-frame-pointer}
5832 generates functions without a frame.)
5833 This is occasionally done with heavily used library functions to save
5834 the frame setup time. @value{GDBN} has limited facilities for dealing
5835 with these function invocations. If the innermost function invocation
5836 has no stack frame, @value{GDBN} nevertheless regards it as though
5837 it had a separate frame, which is numbered zero as usual, allowing
5838 correct tracing of the function call chain. However, @value{GDBN} has
5839 no provision for frameless functions elsewhere in the stack.
5842 @kindex frame@r{, command}
5843 @cindex current stack frame
5844 @item frame @var{args}
5845 The @code{frame} command allows you to move from one stack frame to another,
5846 and to print the stack frame you select. @var{args} may be either the
5847 address of the frame or the stack frame number. Without an argument,
5848 @code{frame} prints the current stack frame.
5850 @kindex select-frame
5851 @cindex selecting frame silently
5853 The @code{select-frame} command allows you to move from one stack frame
5854 to another without printing the frame. This is the silent version of
5862 @cindex call stack traces
5863 A backtrace is a summary of how your program got where it is. It shows one
5864 line per frame, for many frames, starting with the currently executing
5865 frame (frame zero), followed by its caller (frame one), and on up the
5870 @kindex bt @r{(@code{backtrace})}
5873 Print a backtrace of the entire stack: one line per frame for all
5874 frames in the stack.
5876 You can stop the backtrace at any time by typing the system interrupt
5877 character, normally @kbd{Ctrl-c}.
5879 @item backtrace @var{n}
5881 Similar, but print only the innermost @var{n} frames.
5883 @item backtrace -@var{n}
5885 Similar, but print only the outermost @var{n} frames.
5887 @item backtrace full
5889 @itemx bt full @var{n}
5890 @itemx bt full -@var{n}
5891 Print the values of the local variables also. @var{n} specifies the
5892 number of frames to print, as described above.
5897 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5898 are additional aliases for @code{backtrace}.
5900 @cindex multiple threads, backtrace
5901 In a multi-threaded program, @value{GDBN} by default shows the
5902 backtrace only for the current thread. To display the backtrace for
5903 several or all of the threads, use the command @code{thread apply}
5904 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5905 apply all backtrace}, @value{GDBN} will display the backtrace for all
5906 the threads; this is handy when you debug a core dump of a
5907 multi-threaded program.
5909 Each line in the backtrace shows the frame number and the function name.
5910 The program counter value is also shown---unless you use @code{set
5911 print address off}. The backtrace also shows the source file name and
5912 line number, as well as the arguments to the function. The program
5913 counter value is omitted if it is at the beginning of the code for that
5916 Here is an example of a backtrace. It was made with the command
5917 @samp{bt 3}, so it shows the innermost three frames.
5921 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5923 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5924 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5926 (More stack frames follow...)
5931 The display for frame zero does not begin with a program counter
5932 value, indicating that your program has stopped at the beginning of the
5933 code for line @code{993} of @code{builtin.c}.
5936 The value of parameter @code{data} in frame 1 has been replaced by
5937 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5938 only if it is a scalar (integer, pointer, enumeration, etc). See command
5939 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5940 on how to configure the way function parameter values are printed.
5942 @cindex value optimized out, in backtrace
5943 @cindex function call arguments, optimized out
5944 If your program was compiled with optimizations, some compilers will
5945 optimize away arguments passed to functions if those arguments are
5946 never used after the call. Such optimizations generate code that
5947 passes arguments through registers, but doesn't store those arguments
5948 in the stack frame. @value{GDBN} has no way of displaying such
5949 arguments in stack frames other than the innermost one. Here's what
5950 such a backtrace might look like:
5954 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5956 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5957 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5959 (More stack frames follow...)
5964 The values of arguments that were not saved in their stack frames are
5965 shown as @samp{<value optimized out>}.
5967 If you need to display the values of such optimized-out arguments,
5968 either deduce that from other variables whose values depend on the one
5969 you are interested in, or recompile without optimizations.
5971 @cindex backtrace beyond @code{main} function
5972 @cindex program entry point
5973 @cindex startup code, and backtrace
5974 Most programs have a standard user entry point---a place where system
5975 libraries and startup code transition into user code. For C this is
5976 @code{main}@footnote{
5977 Note that embedded programs (the so-called ``free-standing''
5978 environment) are not required to have a @code{main} function as the
5979 entry point. They could even have multiple entry points.}.
5980 When @value{GDBN} finds the entry function in a backtrace
5981 it will terminate the backtrace, to avoid tracing into highly
5982 system-specific (and generally uninteresting) code.
5984 If you need to examine the startup code, or limit the number of levels
5985 in a backtrace, you can change this behavior:
5988 @item set backtrace past-main
5989 @itemx set backtrace past-main on
5990 @kindex set backtrace
5991 Backtraces will continue past the user entry point.
5993 @item set backtrace past-main off
5994 Backtraces will stop when they encounter the user entry point. This is the
5997 @item show backtrace past-main
5998 @kindex show backtrace
5999 Display the current user entry point backtrace policy.
6001 @item set backtrace past-entry
6002 @itemx set backtrace past-entry on
6003 Backtraces will continue past the internal entry point of an application.
6004 This entry point is encoded by the linker when the application is built,
6005 and is likely before the user entry point @code{main} (or equivalent) is called.
6007 @item set backtrace past-entry off
6008 Backtraces will stop when they encounter the internal entry point of an
6009 application. This is the default.
6011 @item show backtrace past-entry
6012 Display the current internal entry point backtrace policy.
6014 @item set backtrace limit @var{n}
6015 @itemx set backtrace limit 0
6016 @cindex backtrace limit
6017 Limit the backtrace to @var{n} levels. A value of zero means
6020 @item show backtrace limit
6021 Display the current limit on backtrace levels.
6025 @section Selecting a Frame
6027 Most commands for examining the stack and other data in your program work on
6028 whichever stack frame is selected at the moment. Here are the commands for
6029 selecting a stack frame; all of them finish by printing a brief description
6030 of the stack frame just selected.
6033 @kindex frame@r{, selecting}
6034 @kindex f @r{(@code{frame})}
6037 Select frame number @var{n}. Recall that frame zero is the innermost
6038 (currently executing) frame, frame one is the frame that called the
6039 innermost one, and so on. The highest-numbered frame is the one for
6042 @item frame @var{addr}
6044 Select the frame at address @var{addr}. This is useful mainly if the
6045 chaining of stack frames has been damaged by a bug, making it
6046 impossible for @value{GDBN} to assign numbers properly to all frames. In
6047 addition, this can be useful when your program has multiple stacks and
6048 switches between them.
6050 On the SPARC architecture, @code{frame} needs two addresses to
6051 select an arbitrary frame: a frame pointer and a stack pointer.
6053 On the MIPS and Alpha architecture, it needs two addresses: a stack
6054 pointer and a program counter.
6056 On the 29k architecture, it needs three addresses: a register stack
6057 pointer, a program counter, and a memory stack pointer.
6061 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6062 advances toward the outermost frame, to higher frame numbers, to frames
6063 that have existed longer. @var{n} defaults to one.
6066 @kindex do @r{(@code{down})}
6068 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6069 advances toward the innermost frame, to lower frame numbers, to frames
6070 that were created more recently. @var{n} defaults to one. You may
6071 abbreviate @code{down} as @code{do}.
6074 All of these commands end by printing two lines of output describing the
6075 frame. The first line shows the frame number, the function name, the
6076 arguments, and the source file and line number of execution in that
6077 frame. The second line shows the text of that source line.
6085 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6087 10 read_input_file (argv[i]);
6091 After such a printout, the @code{list} command with no arguments
6092 prints ten lines centered on the point of execution in the frame.
6093 You can also edit the program at the point of execution with your favorite
6094 editing program by typing @code{edit}.
6095 @xref{List, ,Printing Source Lines},
6099 @kindex down-silently
6101 @item up-silently @var{n}
6102 @itemx down-silently @var{n}
6103 These two commands are variants of @code{up} and @code{down},
6104 respectively; they differ in that they do their work silently, without
6105 causing display of the new frame. They are intended primarily for use
6106 in @value{GDBN} command scripts, where the output might be unnecessary and
6111 @section Information About a Frame
6113 There are several other commands to print information about the selected
6119 When used without any argument, this command does not change which
6120 frame is selected, but prints a brief description of the currently
6121 selected stack frame. It can be abbreviated @code{f}. With an
6122 argument, this command is used to select a stack frame.
6123 @xref{Selection, ,Selecting a Frame}.
6126 @kindex info f @r{(@code{info frame})}
6129 This command prints a verbose description of the selected stack frame,
6134 the address of the frame
6136 the address of the next frame down (called by this frame)
6138 the address of the next frame up (caller of this frame)
6140 the language in which the source code corresponding to this frame is written
6142 the address of the frame's arguments
6144 the address of the frame's local variables
6146 the program counter saved in it (the address of execution in the caller frame)
6148 which registers were saved in the frame
6151 @noindent The verbose description is useful when
6152 something has gone wrong that has made the stack format fail to fit
6153 the usual conventions.
6155 @item info frame @var{addr}
6156 @itemx info f @var{addr}
6157 Print a verbose description of the frame at address @var{addr}, without
6158 selecting that frame. The selected frame remains unchanged by this
6159 command. This requires the same kind of address (more than one for some
6160 architectures) that you specify in the @code{frame} command.
6161 @xref{Selection, ,Selecting a Frame}.
6165 Print the arguments of the selected frame, each on a separate line.
6169 Print the local variables of the selected frame, each on a separate
6170 line. These are all variables (declared either static or automatic)
6171 accessible at the point of execution of the selected frame.
6174 @cindex catch exceptions, list active handlers
6175 @cindex exception handlers, how to list
6177 Print a list of all the exception handlers that are active in the
6178 current stack frame at the current point of execution. To see other
6179 exception handlers, visit the associated frame (using the @code{up},
6180 @code{down}, or @code{frame} commands); then type @code{info catch}.
6181 @xref{Set Catchpoints, , Setting Catchpoints}.
6187 @chapter Examining Source Files
6189 @value{GDBN} can print parts of your program's source, since the debugging
6190 information recorded in the program tells @value{GDBN} what source files were
6191 used to build it. When your program stops, @value{GDBN} spontaneously prints
6192 the line where it stopped. Likewise, when you select a stack frame
6193 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6194 execution in that frame has stopped. You can print other portions of
6195 source files by explicit command.
6197 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6198 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6199 @value{GDBN} under @sc{gnu} Emacs}.
6202 * List:: Printing source lines
6203 * Specify Location:: How to specify code locations
6204 * Edit:: Editing source files
6205 * Search:: Searching source files
6206 * Source Path:: Specifying source directories
6207 * Machine Code:: Source and machine code
6211 @section Printing Source Lines
6214 @kindex l @r{(@code{list})}
6215 To print lines from a source file, use the @code{list} command
6216 (abbreviated @code{l}). By default, ten lines are printed.
6217 There are several ways to specify what part of the file you want to
6218 print; see @ref{Specify Location}, for the full list.
6220 Here are the forms of the @code{list} command most commonly used:
6223 @item list @var{linenum}
6224 Print lines centered around line number @var{linenum} in the
6225 current source file.
6227 @item list @var{function}
6228 Print lines centered around the beginning of function
6232 Print more lines. If the last lines printed were printed with a
6233 @code{list} command, this prints lines following the last lines
6234 printed; however, if the last line printed was a solitary line printed
6235 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6236 Stack}), this prints lines centered around that line.
6239 Print lines just before the lines last printed.
6242 @cindex @code{list}, how many lines to display
6243 By default, @value{GDBN} prints ten source lines with any of these forms of
6244 the @code{list} command. You can change this using @code{set listsize}:
6247 @kindex set listsize
6248 @item set listsize @var{count}
6249 Make the @code{list} command display @var{count} source lines (unless
6250 the @code{list} argument explicitly specifies some other number).
6252 @kindex show listsize
6254 Display the number of lines that @code{list} prints.
6257 Repeating a @code{list} command with @key{RET} discards the argument,
6258 so it is equivalent to typing just @code{list}. This is more useful
6259 than listing the same lines again. An exception is made for an
6260 argument of @samp{-}; that argument is preserved in repetition so that
6261 each repetition moves up in the source file.
6263 In general, the @code{list} command expects you to supply zero, one or two
6264 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6265 of writing them (@pxref{Specify Location}), but the effect is always
6266 to specify some source line.
6268 Here is a complete description of the possible arguments for @code{list}:
6271 @item list @var{linespec}
6272 Print lines centered around the line specified by @var{linespec}.
6274 @item list @var{first},@var{last}
6275 Print lines from @var{first} to @var{last}. Both arguments are
6276 linespecs. When a @code{list} command has two linespecs, and the
6277 source file of the second linespec is omitted, this refers to
6278 the same source file as the first linespec.
6280 @item list ,@var{last}
6281 Print lines ending with @var{last}.
6283 @item list @var{first},
6284 Print lines starting with @var{first}.
6287 Print lines just after the lines last printed.
6290 Print lines just before the lines last printed.
6293 As described in the preceding table.
6296 @node Specify Location
6297 @section Specifying a Location
6298 @cindex specifying location
6301 Several @value{GDBN} commands accept arguments that specify a location
6302 of your program's code. Since @value{GDBN} is a source-level
6303 debugger, a location usually specifies some line in the source code;
6304 for that reason, locations are also known as @dfn{linespecs}.
6306 Here are all the different ways of specifying a code location that
6307 @value{GDBN} understands:
6311 Specifies the line number @var{linenum} of the current source file.
6314 @itemx +@var{offset}
6315 Specifies the line @var{offset} lines before or after the @dfn{current
6316 line}. For the @code{list} command, the current line is the last one
6317 printed; for the breakpoint commands, this is the line at which
6318 execution stopped in the currently selected @dfn{stack frame}
6319 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6320 used as the second of the two linespecs in a @code{list} command,
6321 this specifies the line @var{offset} lines up or down from the first
6324 @item @var{filename}:@var{linenum}
6325 Specifies the line @var{linenum} in the source file @var{filename}.
6327 @item @var{function}
6328 Specifies the line that begins the body of the function @var{function}.
6329 For example, in C, this is the line with the open brace.
6331 @item @var{filename}:@var{function}
6332 Specifies the line that begins the body of the function @var{function}
6333 in the file @var{filename}. You only need the file name with a
6334 function name to avoid ambiguity when there are identically named
6335 functions in different source files.
6338 Specifies the line at which the label named @var{label} appears.
6339 @value{GDBN} searches for the label in the function corresponding to
6340 the currently selected stack frame. If there is no current selected
6341 stack frame (for instance, if the inferior is not running), then
6342 @value{GDBN} will not search for a label.
6344 @item *@var{address}
6345 Specifies the program address @var{address}. For line-oriented
6346 commands, such as @code{list} and @code{edit}, this specifies a source
6347 line that contains @var{address}. For @code{break} and other
6348 breakpoint oriented commands, this can be used to set breakpoints in
6349 parts of your program which do not have debugging information or
6352 Here @var{address} may be any expression valid in the current working
6353 language (@pxref{Languages, working language}) that specifies a code
6354 address. In addition, as a convenience, @value{GDBN} extends the
6355 semantics of expressions used in locations to cover the situations
6356 that frequently happen during debugging. Here are the various forms
6360 @item @var{expression}
6361 Any expression valid in the current working language.
6363 @item @var{funcaddr}
6364 An address of a function or procedure derived from its name. In C,
6365 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6366 simply the function's name @var{function} (and actually a special case
6367 of a valid expression). In Pascal and Modula-2, this is
6368 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6369 (although the Pascal form also works).
6371 This form specifies the address of the function's first instruction,
6372 before the stack frame and arguments have been set up.
6374 @item '@var{filename}'::@var{funcaddr}
6375 Like @var{funcaddr} above, but also specifies the name of the source
6376 file explicitly. This is useful if the name of the function does not
6377 specify the function unambiguously, e.g., if there are several
6378 functions with identical names in different source files.
6385 @section Editing Source Files
6386 @cindex editing source files
6389 @kindex e @r{(@code{edit})}
6390 To edit the lines in a source file, use the @code{edit} command.
6391 The editing program of your choice
6392 is invoked with the current line set to
6393 the active line in the program.
6394 Alternatively, there are several ways to specify what part of the file you
6395 want to print if you want to see other parts of the program:
6398 @item edit @var{location}
6399 Edit the source file specified by @code{location}. Editing starts at
6400 that @var{location}, e.g., at the specified source line of the
6401 specified file. @xref{Specify Location}, for all the possible forms
6402 of the @var{location} argument; here are the forms of the @code{edit}
6403 command most commonly used:
6406 @item edit @var{number}
6407 Edit the current source file with @var{number} as the active line number.
6409 @item edit @var{function}
6410 Edit the file containing @var{function} at the beginning of its definition.
6415 @subsection Choosing your Editor
6416 You can customize @value{GDBN} to use any editor you want
6418 The only restriction is that your editor (say @code{ex}), recognizes the
6419 following command-line syntax:
6421 ex +@var{number} file
6423 The optional numeric value +@var{number} specifies the number of the line in
6424 the file where to start editing.}.
6425 By default, it is @file{@value{EDITOR}}, but you can change this
6426 by setting the environment variable @code{EDITOR} before using
6427 @value{GDBN}. For example, to configure @value{GDBN} to use the
6428 @code{vi} editor, you could use these commands with the @code{sh} shell:
6434 or in the @code{csh} shell,
6436 setenv EDITOR /usr/bin/vi
6441 @section Searching Source Files
6442 @cindex searching source files
6444 There are two commands for searching through the current source file for a
6449 @kindex forward-search
6450 @item forward-search @var{regexp}
6451 @itemx search @var{regexp}
6452 The command @samp{forward-search @var{regexp}} checks each line,
6453 starting with the one following the last line listed, for a match for
6454 @var{regexp}. It lists the line that is found. You can use the
6455 synonym @samp{search @var{regexp}} or abbreviate the command name as
6458 @kindex reverse-search
6459 @item reverse-search @var{regexp}
6460 The command @samp{reverse-search @var{regexp}} checks each line, starting
6461 with the one before the last line listed and going backward, for a match
6462 for @var{regexp}. It lists the line that is found. You can abbreviate
6463 this command as @code{rev}.
6467 @section Specifying Source Directories
6470 @cindex directories for source files
6471 Executable programs sometimes do not record the directories of the source
6472 files from which they were compiled, just the names. Even when they do,
6473 the directories could be moved between the compilation and your debugging
6474 session. @value{GDBN} has a list of directories to search for source files;
6475 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6476 it tries all the directories in the list, in the order they are present
6477 in the list, until it finds a file with the desired name.
6479 For example, suppose an executable references the file
6480 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6481 @file{/mnt/cross}. The file is first looked up literally; if this
6482 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6483 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6484 message is printed. @value{GDBN} does not look up the parts of the
6485 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6486 Likewise, the subdirectories of the source path are not searched: if
6487 the source path is @file{/mnt/cross}, and the binary refers to
6488 @file{foo.c}, @value{GDBN} would not find it under
6489 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6491 Plain file names, relative file names with leading directories, file
6492 names containing dots, etc.@: are all treated as described above; for
6493 instance, if the source path is @file{/mnt/cross}, and the source file
6494 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6495 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6496 that---@file{/mnt/cross/foo.c}.
6498 Note that the executable search path is @emph{not} used to locate the
6501 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6502 any information it has cached about where source files are found and where
6503 each line is in the file.
6507 When you start @value{GDBN}, its source path includes only @samp{cdir}
6508 and @samp{cwd}, in that order.
6509 To add other directories, use the @code{directory} command.
6511 The search path is used to find both program source files and @value{GDBN}
6512 script files (read using the @samp{-command} option and @samp{source} command).
6514 In addition to the source path, @value{GDBN} provides a set of commands
6515 that manage a list of source path substitution rules. A @dfn{substitution
6516 rule} specifies how to rewrite source directories stored in the program's
6517 debug information in case the sources were moved to a different
6518 directory between compilation and debugging. A rule is made of
6519 two strings, the first specifying what needs to be rewritten in
6520 the path, and the second specifying how it should be rewritten.
6521 In @ref{set substitute-path}, we name these two parts @var{from} and
6522 @var{to} respectively. @value{GDBN} does a simple string replacement
6523 of @var{from} with @var{to} at the start of the directory part of the
6524 source file name, and uses that result instead of the original file
6525 name to look up the sources.
6527 Using the previous example, suppose the @file{foo-1.0} tree has been
6528 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6529 @value{GDBN} to replace @file{/usr/src} in all source path names with
6530 @file{/mnt/cross}. The first lookup will then be
6531 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6532 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6533 substitution rule, use the @code{set substitute-path} command
6534 (@pxref{set substitute-path}).
6536 To avoid unexpected substitution results, a rule is applied only if the
6537 @var{from} part of the directory name ends at a directory separator.
6538 For instance, a rule substituting @file{/usr/source} into
6539 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6540 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6541 is applied only at the beginning of the directory name, this rule will
6542 not be applied to @file{/root/usr/source/baz.c} either.
6544 In many cases, you can achieve the same result using the @code{directory}
6545 command. However, @code{set substitute-path} can be more efficient in
6546 the case where the sources are organized in a complex tree with multiple
6547 subdirectories. With the @code{directory} command, you need to add each
6548 subdirectory of your project. If you moved the entire tree while
6549 preserving its internal organization, then @code{set substitute-path}
6550 allows you to direct the debugger to all the sources with one single
6553 @code{set substitute-path} is also more than just a shortcut command.
6554 The source path is only used if the file at the original location no
6555 longer exists. On the other hand, @code{set substitute-path} modifies
6556 the debugger behavior to look at the rewritten location instead. So, if
6557 for any reason a source file that is not relevant to your executable is
6558 located at the original location, a substitution rule is the only
6559 method available to point @value{GDBN} at the new location.
6561 @cindex @samp{--with-relocated-sources}
6562 @cindex default source path substitution
6563 You can configure a default source path substitution rule by
6564 configuring @value{GDBN} with the
6565 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6566 should be the name of a directory under @value{GDBN}'s configured
6567 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6568 directory names in debug information under @var{dir} will be adjusted
6569 automatically if the installed @value{GDBN} is moved to a new
6570 location. This is useful if @value{GDBN}, libraries or executables
6571 with debug information and corresponding source code are being moved
6575 @item directory @var{dirname} @dots{}
6576 @item dir @var{dirname} @dots{}
6577 Add directory @var{dirname} to the front of the source path. Several
6578 directory names may be given to this command, separated by @samp{:}
6579 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6580 part of absolute file names) or
6581 whitespace. You may specify a directory that is already in the source
6582 path; this moves it forward, so @value{GDBN} searches it sooner.
6586 @vindex $cdir@r{, convenience variable}
6587 @vindex $cwd@r{, convenience variable}
6588 @cindex compilation directory
6589 @cindex current directory
6590 @cindex working directory
6591 @cindex directory, current
6592 @cindex directory, compilation
6593 You can use the string @samp{$cdir} to refer to the compilation
6594 directory (if one is recorded), and @samp{$cwd} to refer to the current
6595 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6596 tracks the current working directory as it changes during your @value{GDBN}
6597 session, while the latter is immediately expanded to the current
6598 directory at the time you add an entry to the source path.
6601 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6603 @c RET-repeat for @code{directory} is explicitly disabled, but since
6604 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6606 @item show directories
6607 @kindex show directories
6608 Print the source path: show which directories it contains.
6610 @anchor{set substitute-path}
6611 @item set substitute-path @var{from} @var{to}
6612 @kindex set substitute-path
6613 Define a source path substitution rule, and add it at the end of the
6614 current list of existing substitution rules. If a rule with the same
6615 @var{from} was already defined, then the old rule is also deleted.
6617 For example, if the file @file{/foo/bar/baz.c} was moved to
6618 @file{/mnt/cross/baz.c}, then the command
6621 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6625 will tell @value{GDBN} to replace @samp{/usr/src} with
6626 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6627 @file{baz.c} even though it was moved.
6629 In the case when more than one substitution rule have been defined,
6630 the rules are evaluated one by one in the order where they have been
6631 defined. The first one matching, if any, is selected to perform
6634 For instance, if we had entered the following commands:
6637 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6638 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6642 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6643 @file{/mnt/include/defs.h} by using the first rule. However, it would
6644 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6645 @file{/mnt/src/lib/foo.c}.
6648 @item unset substitute-path [path]
6649 @kindex unset substitute-path
6650 If a path is specified, search the current list of substitution rules
6651 for a rule that would rewrite that path. Delete that rule if found.
6652 A warning is emitted by the debugger if no rule could be found.
6654 If no path is specified, then all substitution rules are deleted.
6656 @item show substitute-path [path]
6657 @kindex show substitute-path
6658 If a path is specified, then print the source path substitution rule
6659 which would rewrite that path, if any.
6661 If no path is specified, then print all existing source path substitution
6666 If your source path is cluttered with directories that are no longer of
6667 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6668 versions of source. You can correct the situation as follows:
6672 Use @code{directory} with no argument to reset the source path to its default value.
6675 Use @code{directory} with suitable arguments to reinstall the
6676 directories you want in the source path. You can add all the
6677 directories in one command.
6681 @section Source and Machine Code
6682 @cindex source line and its code address
6684 You can use the command @code{info line} to map source lines to program
6685 addresses (and vice versa), and the command @code{disassemble} to display
6686 a range of addresses as machine instructions. You can use the command
6687 @code{set disassemble-next-line} to set whether to disassemble next
6688 source line when execution stops. When run under @sc{gnu} Emacs
6689 mode, the @code{info line} command causes the arrow to point to the
6690 line specified. Also, @code{info line} prints addresses in symbolic form as
6695 @item info line @var{linespec}
6696 Print the starting and ending addresses of the compiled code for
6697 source line @var{linespec}. You can specify source lines in any of
6698 the ways documented in @ref{Specify Location}.
6701 For example, we can use @code{info line} to discover the location of
6702 the object code for the first line of function
6703 @code{m4_changequote}:
6705 @c FIXME: I think this example should also show the addresses in
6706 @c symbolic form, as they usually would be displayed.
6708 (@value{GDBP}) info line m4_changequote
6709 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6713 @cindex code address and its source line
6714 We can also inquire (using @code{*@var{addr}} as the form for
6715 @var{linespec}) what source line covers a particular address:
6717 (@value{GDBP}) info line *0x63ff
6718 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6721 @cindex @code{$_} and @code{info line}
6722 @cindex @code{x} command, default address
6723 @kindex x@r{(examine), and} info line
6724 After @code{info line}, the default address for the @code{x} command
6725 is changed to the starting address of the line, so that @samp{x/i} is
6726 sufficient to begin examining the machine code (@pxref{Memory,
6727 ,Examining Memory}). Also, this address is saved as the value of the
6728 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6733 @cindex assembly instructions
6734 @cindex instructions, assembly
6735 @cindex machine instructions
6736 @cindex listing machine instructions
6738 @itemx disassemble /m
6739 @itemx disassemble /r
6740 This specialized command dumps a range of memory as machine
6741 instructions. It can also print mixed source+disassembly by specifying
6742 the @code{/m} modifier and print the raw instructions in hex as well as
6743 in symbolic form by specifying the @code{/r}.
6744 The default memory range is the function surrounding the
6745 program counter of the selected frame. A single argument to this
6746 command is a program counter value; @value{GDBN} dumps the function
6747 surrounding this value. When two arguments are given, they should
6748 be separated by a comma, possibly surrounded by whitespace. The
6749 arguments specify a range of addresses to dump, in one of two forms:
6752 @item @var{start},@var{end}
6753 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6754 @item @var{start},+@var{length}
6755 the addresses from @var{start} (inclusive) to
6756 @code{@var{start}+@var{length}} (exclusive).
6760 When 2 arguments are specified, the name of the function is also
6761 printed (since there could be several functions in the given range).
6763 The argument(s) can be any expression yielding a numeric value, such as
6764 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6766 If the range of memory being disassembled contains current program counter,
6767 the instruction at that location is shown with a @code{=>} marker.
6770 The following example shows the disassembly of a range of addresses of
6771 HP PA-RISC 2.0 code:
6774 (@value{GDBP}) disas 0x32c4, 0x32e4
6775 Dump of assembler code from 0x32c4 to 0x32e4:
6776 0x32c4 <main+204>: addil 0,dp
6777 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6778 0x32cc <main+212>: ldil 0x3000,r31
6779 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6780 0x32d4 <main+220>: ldo 0(r31),rp
6781 0x32d8 <main+224>: addil -0x800,dp
6782 0x32dc <main+228>: ldo 0x588(r1),r26
6783 0x32e0 <main+232>: ldil 0x3000,r31
6784 End of assembler dump.
6787 Here is an example showing mixed source+assembly for Intel x86, when the
6788 program is stopped just after function prologue:
6791 (@value{GDBP}) disas /m main
6792 Dump of assembler code for function main:
6794 0x08048330 <+0>: push %ebp
6795 0x08048331 <+1>: mov %esp,%ebp
6796 0x08048333 <+3>: sub $0x8,%esp
6797 0x08048336 <+6>: and $0xfffffff0,%esp
6798 0x08048339 <+9>: sub $0x10,%esp
6800 6 printf ("Hello.\n");
6801 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6802 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6806 0x08048348 <+24>: mov $0x0,%eax
6807 0x0804834d <+29>: leave
6808 0x0804834e <+30>: ret
6810 End of assembler dump.
6813 Here is another example showing raw instructions in hex for AMD x86-64,
6816 (gdb) disas /r 0x400281,+10
6817 Dump of assembler code from 0x400281 to 0x40028b:
6818 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6819 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6820 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6821 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6822 End of assembler dump.
6825 Some architectures have more than one commonly-used set of instruction
6826 mnemonics or other syntax.
6828 For programs that were dynamically linked and use shared libraries,
6829 instructions that call functions or branch to locations in the shared
6830 libraries might show a seemingly bogus location---it's actually a
6831 location of the relocation table. On some architectures, @value{GDBN}
6832 might be able to resolve these to actual function names.
6835 @kindex set disassembly-flavor
6836 @cindex Intel disassembly flavor
6837 @cindex AT&T disassembly flavor
6838 @item set disassembly-flavor @var{instruction-set}
6839 Select the instruction set to use when disassembling the
6840 program via the @code{disassemble} or @code{x/i} commands.
6842 Currently this command is only defined for the Intel x86 family. You
6843 can set @var{instruction-set} to either @code{intel} or @code{att}.
6844 The default is @code{att}, the AT&T flavor used by default by Unix
6845 assemblers for x86-based targets.
6847 @kindex show disassembly-flavor
6848 @item show disassembly-flavor
6849 Show the current setting of the disassembly flavor.
6853 @kindex set disassemble-next-line
6854 @kindex show disassemble-next-line
6855 @item set disassemble-next-line
6856 @itemx show disassemble-next-line
6857 Control whether or not @value{GDBN} will disassemble the next source
6858 line or instruction when execution stops. If ON, @value{GDBN} will
6859 display disassembly of the next source line when execution of the
6860 program being debugged stops. This is @emph{in addition} to
6861 displaying the source line itself, which @value{GDBN} always does if
6862 possible. If the next source line cannot be displayed for some reason
6863 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6864 info in the debug info), @value{GDBN} will display disassembly of the
6865 next @emph{instruction} instead of showing the next source line. If
6866 AUTO, @value{GDBN} will display disassembly of next instruction only
6867 if the source line cannot be displayed. This setting causes
6868 @value{GDBN} to display some feedback when you step through a function
6869 with no line info or whose source file is unavailable. The default is
6870 OFF, which means never display the disassembly of the next line or
6876 @chapter Examining Data
6878 @cindex printing data
6879 @cindex examining data
6882 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6883 @c document because it is nonstandard... Under Epoch it displays in a
6884 @c different window or something like that.
6885 The usual way to examine data in your program is with the @code{print}
6886 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6887 evaluates and prints the value of an expression of the language your
6888 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6889 Different Languages}). It may also print the expression using a
6890 Python-based pretty-printer (@pxref{Pretty Printing}).
6893 @item print @var{expr}
6894 @itemx print /@var{f} @var{expr}
6895 @var{expr} is an expression (in the source language). By default the
6896 value of @var{expr} is printed in a format appropriate to its data type;
6897 you can choose a different format by specifying @samp{/@var{f}}, where
6898 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6902 @itemx print /@var{f}
6903 @cindex reprint the last value
6904 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6905 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6906 conveniently inspect the same value in an alternative format.
6909 A more low-level way of examining data is with the @code{x} command.
6910 It examines data in memory at a specified address and prints it in a
6911 specified format. @xref{Memory, ,Examining Memory}.
6913 If you are interested in information about types, or about how the
6914 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6915 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6919 * Expressions:: Expressions
6920 * Ambiguous Expressions:: Ambiguous Expressions
6921 * Variables:: Program variables
6922 * Arrays:: Artificial arrays
6923 * Output Formats:: Output formats
6924 * Memory:: Examining memory
6925 * Auto Display:: Automatic display
6926 * Print Settings:: Print settings
6927 * Pretty Printing:: Python pretty printing
6928 * Value History:: Value history
6929 * Convenience Vars:: Convenience variables
6930 * Registers:: Registers
6931 * Floating Point Hardware:: Floating point hardware
6932 * Vector Unit:: Vector Unit
6933 * OS Information:: Auxiliary data provided by operating system
6934 * Memory Region Attributes:: Memory region attributes
6935 * Dump/Restore Files:: Copy between memory and a file
6936 * Core File Generation:: Cause a program dump its core
6937 * Character Sets:: Debugging programs that use a different
6938 character set than GDB does
6939 * Caching Remote Data:: Data caching for remote targets
6940 * Searching Memory:: Searching memory for a sequence of bytes
6944 @section Expressions
6947 @code{print} and many other @value{GDBN} commands accept an expression and
6948 compute its value. Any kind of constant, variable or operator defined
6949 by the programming language you are using is valid in an expression in
6950 @value{GDBN}. This includes conditional expressions, function calls,
6951 casts, and string constants. It also includes preprocessor macros, if
6952 you compiled your program to include this information; see
6955 @cindex arrays in expressions
6956 @value{GDBN} supports array constants in expressions input by
6957 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6958 you can use the command @code{print @{1, 2, 3@}} to create an array
6959 of three integers. If you pass an array to a function or assign it
6960 to a program variable, @value{GDBN} copies the array to memory that
6961 is @code{malloc}ed in the target program.
6963 Because C is so widespread, most of the expressions shown in examples in
6964 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6965 Languages}, for information on how to use expressions in other
6968 In this section, we discuss operators that you can use in @value{GDBN}
6969 expressions regardless of your programming language.
6971 @cindex casts, in expressions
6972 Casts are supported in all languages, not just in C, because it is so
6973 useful to cast a number into a pointer in order to examine a structure
6974 at that address in memory.
6975 @c FIXME: casts supported---Mod2 true?
6977 @value{GDBN} supports these operators, in addition to those common
6978 to programming languages:
6982 @samp{@@} is a binary operator for treating parts of memory as arrays.
6983 @xref{Arrays, ,Artificial Arrays}, for more information.
6986 @samp{::} allows you to specify a variable in terms of the file or
6987 function where it is defined. @xref{Variables, ,Program Variables}.
6989 @cindex @{@var{type}@}
6990 @cindex type casting memory
6991 @cindex memory, viewing as typed object
6992 @cindex casts, to view memory
6993 @item @{@var{type}@} @var{addr}
6994 Refers to an object of type @var{type} stored at address @var{addr} in
6995 memory. @var{addr} may be any expression whose value is an integer or
6996 pointer (but parentheses are required around binary operators, just as in
6997 a cast). This construct is allowed regardless of what kind of data is
6998 normally supposed to reside at @var{addr}.
7001 @node Ambiguous Expressions
7002 @section Ambiguous Expressions
7003 @cindex ambiguous expressions
7005 Expressions can sometimes contain some ambiguous elements. For instance,
7006 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7007 a single function name to be defined several times, for application in
7008 different contexts. This is called @dfn{overloading}. Another example
7009 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7010 templates and is typically instantiated several times, resulting in
7011 the same function name being defined in different contexts.
7013 In some cases and depending on the language, it is possible to adjust
7014 the expression to remove the ambiguity. For instance in C@t{++}, you
7015 can specify the signature of the function you want to break on, as in
7016 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7017 qualified name of your function often makes the expression unambiguous
7020 When an ambiguity that needs to be resolved is detected, the debugger
7021 has the capability to display a menu of numbered choices for each
7022 possibility, and then waits for the selection with the prompt @samp{>}.
7023 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7024 aborts the current command. If the command in which the expression was
7025 used allows more than one choice to be selected, the next option in the
7026 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7029 For example, the following session excerpt shows an attempt to set a
7030 breakpoint at the overloaded symbol @code{String::after}.
7031 We choose three particular definitions of that function name:
7033 @c FIXME! This is likely to change to show arg type lists, at least
7036 (@value{GDBP}) b String::after
7039 [2] file:String.cc; line number:867
7040 [3] file:String.cc; line number:860
7041 [4] file:String.cc; line number:875
7042 [5] file:String.cc; line number:853
7043 [6] file:String.cc; line number:846
7044 [7] file:String.cc; line number:735
7046 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7047 Breakpoint 2 at 0xb344: file String.cc, line 875.
7048 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7049 Multiple breakpoints were set.
7050 Use the "delete" command to delete unwanted
7057 @kindex set multiple-symbols
7058 @item set multiple-symbols @var{mode}
7059 @cindex multiple-symbols menu
7061 This option allows you to adjust the debugger behavior when an expression
7064 By default, @var{mode} is set to @code{all}. If the command with which
7065 the expression is used allows more than one choice, then @value{GDBN}
7066 automatically selects all possible choices. For instance, inserting
7067 a breakpoint on a function using an ambiguous name results in a breakpoint
7068 inserted on each possible match. However, if a unique choice must be made,
7069 then @value{GDBN} uses the menu to help you disambiguate the expression.
7070 For instance, printing the address of an overloaded function will result
7071 in the use of the menu.
7073 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7074 when an ambiguity is detected.
7076 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7077 an error due to the ambiguity and the command is aborted.
7079 @kindex show multiple-symbols
7080 @item show multiple-symbols
7081 Show the current value of the @code{multiple-symbols} setting.
7085 @section Program Variables
7087 The most common kind of expression to use is the name of a variable
7090 Variables in expressions are understood in the selected stack frame
7091 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7095 global (or file-static)
7102 visible according to the scope rules of the
7103 programming language from the point of execution in that frame
7106 @noindent This means that in the function
7121 you can examine and use the variable @code{a} whenever your program is
7122 executing within the function @code{foo}, but you can only use or
7123 examine the variable @code{b} while your program is executing inside
7124 the block where @code{b} is declared.
7126 @cindex variable name conflict
7127 There is an exception: you can refer to a variable or function whose
7128 scope is a single source file even if the current execution point is not
7129 in this file. But it is possible to have more than one such variable or
7130 function with the same name (in different source files). If that
7131 happens, referring to that name has unpredictable effects. If you wish,
7132 you can specify a static variable in a particular function or file,
7133 using the colon-colon (@code{::}) notation:
7135 @cindex colon-colon, context for variables/functions
7137 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7138 @cindex @code{::}, context for variables/functions
7141 @var{file}::@var{variable}
7142 @var{function}::@var{variable}
7146 Here @var{file} or @var{function} is the name of the context for the
7147 static @var{variable}. In the case of file names, you can use quotes to
7148 make sure @value{GDBN} parses the file name as a single word---for example,
7149 to print a global value of @code{x} defined in @file{f2.c}:
7152 (@value{GDBP}) p 'f2.c'::x
7155 @cindex C@t{++} scope resolution
7156 This use of @samp{::} is very rarely in conflict with the very similar
7157 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7158 scope resolution operator in @value{GDBN} expressions.
7159 @c FIXME: Um, so what happens in one of those rare cases where it's in
7162 @cindex wrong values
7163 @cindex variable values, wrong
7164 @cindex function entry/exit, wrong values of variables
7165 @cindex optimized code, wrong values of variables
7167 @emph{Warning:} Occasionally, a local variable may appear to have the
7168 wrong value at certain points in a function---just after entry to a new
7169 scope, and just before exit.
7171 You may see this problem when you are stepping by machine instructions.
7172 This is because, on most machines, it takes more than one instruction to
7173 set up a stack frame (including local variable definitions); if you are
7174 stepping by machine instructions, variables may appear to have the wrong
7175 values until the stack frame is completely built. On exit, it usually
7176 also takes more than one machine instruction to destroy a stack frame;
7177 after you begin stepping through that group of instructions, local
7178 variable definitions may be gone.
7180 This may also happen when the compiler does significant optimizations.
7181 To be sure of always seeing accurate values, turn off all optimization
7184 @cindex ``No symbol "foo" in current context''
7185 Another possible effect of compiler optimizations is to optimize
7186 unused variables out of existence, or assign variables to registers (as
7187 opposed to memory addresses). Depending on the support for such cases
7188 offered by the debug info format used by the compiler, @value{GDBN}
7189 might not be able to display values for such local variables. If that
7190 happens, @value{GDBN} will print a message like this:
7193 No symbol "foo" in current context.
7196 To solve such problems, either recompile without optimizations, or use a
7197 different debug info format, if the compiler supports several such
7198 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7199 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7200 produces debug info in a format that is superior to formats such as
7201 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7202 an effective form for debug info. @xref{Debugging Options,,Options
7203 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7204 Compiler Collection (GCC)}.
7205 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7206 that are best suited to C@t{++} programs.
7208 If you ask to print an object whose contents are unknown to
7209 @value{GDBN}, e.g., because its data type is not completely specified
7210 by the debug information, @value{GDBN} will say @samp{<incomplete
7211 type>}. @xref{Symbols, incomplete type}, for more about this.
7213 Strings are identified as arrays of @code{char} values without specified
7214 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7215 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7216 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7217 defines literal string type @code{"char"} as @code{char} without a sign.
7222 signed char var1[] = "A";
7225 You get during debugging
7230 $2 = @{65 'A', 0 '\0'@}
7234 @section Artificial Arrays
7236 @cindex artificial array
7238 @kindex @@@r{, referencing memory as an array}
7239 It is often useful to print out several successive objects of the
7240 same type in memory; a section of an array, or an array of
7241 dynamically determined size for which only a pointer exists in the
7244 You can do this by referring to a contiguous span of memory as an
7245 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7246 operand of @samp{@@} should be the first element of the desired array
7247 and be an individual object. The right operand should be the desired length
7248 of the array. The result is an array value whose elements are all of
7249 the type of the left argument. The first element is actually the left
7250 argument; the second element comes from bytes of memory immediately
7251 following those that hold the first element, and so on. Here is an
7252 example. If a program says
7255 int *array = (int *) malloc (len * sizeof (int));
7259 you can print the contents of @code{array} with
7265 The left operand of @samp{@@} must reside in memory. Array values made
7266 with @samp{@@} in this way behave just like other arrays in terms of
7267 subscripting, and are coerced to pointers when used in expressions.
7268 Artificial arrays most often appear in expressions via the value history
7269 (@pxref{Value History, ,Value History}), after printing one out.
7271 Another way to create an artificial array is to use a cast.
7272 This re-interprets a value as if it were an array.
7273 The value need not be in memory:
7275 (@value{GDBP}) p/x (short[2])0x12345678
7276 $1 = @{0x1234, 0x5678@}
7279 As a convenience, if you leave the array length out (as in
7280 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7281 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7283 (@value{GDBP}) p/x (short[])0x12345678
7284 $2 = @{0x1234, 0x5678@}
7287 Sometimes the artificial array mechanism is not quite enough; in
7288 moderately complex data structures, the elements of interest may not
7289 actually be adjacent---for example, if you are interested in the values
7290 of pointers in an array. One useful work-around in this situation is
7291 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7292 Variables}) as a counter in an expression that prints the first
7293 interesting value, and then repeat that expression via @key{RET}. For
7294 instance, suppose you have an array @code{dtab} of pointers to
7295 structures, and you are interested in the values of a field @code{fv}
7296 in each structure. Here is an example of what you might type:
7306 @node Output Formats
7307 @section Output Formats
7309 @cindex formatted output
7310 @cindex output formats
7311 By default, @value{GDBN} prints a value according to its data type. Sometimes
7312 this is not what you want. For example, you might want to print a number
7313 in hex, or a pointer in decimal. Or you might want to view data in memory
7314 at a certain address as a character string or as an instruction. To do
7315 these things, specify an @dfn{output format} when you print a value.
7317 The simplest use of output formats is to say how to print a value
7318 already computed. This is done by starting the arguments of the
7319 @code{print} command with a slash and a format letter. The format
7320 letters supported are:
7324 Regard the bits of the value as an integer, and print the integer in
7328 Print as integer in signed decimal.
7331 Print as integer in unsigned decimal.
7334 Print as integer in octal.
7337 Print as integer in binary. The letter @samp{t} stands for ``two''.
7338 @footnote{@samp{b} cannot be used because these format letters are also
7339 used with the @code{x} command, where @samp{b} stands for ``byte'';
7340 see @ref{Memory,,Examining Memory}.}
7343 @cindex unknown address, locating
7344 @cindex locate address
7345 Print as an address, both absolute in hexadecimal and as an offset from
7346 the nearest preceding symbol. You can use this format used to discover
7347 where (in what function) an unknown address is located:
7350 (@value{GDBP}) p/a 0x54320
7351 $3 = 0x54320 <_initialize_vx+396>
7355 The command @code{info symbol 0x54320} yields similar results.
7356 @xref{Symbols, info symbol}.
7359 Regard as an integer and print it as a character constant. This
7360 prints both the numerical value and its character representation. The
7361 character representation is replaced with the octal escape @samp{\nnn}
7362 for characters outside the 7-bit @sc{ascii} range.
7364 Without this format, @value{GDBN} displays @code{char},
7365 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7366 constants. Single-byte members of vectors are displayed as integer
7370 Regard the bits of the value as a floating point number and print
7371 using typical floating point syntax.
7374 @cindex printing strings
7375 @cindex printing byte arrays
7376 Regard as a string, if possible. With this format, pointers to single-byte
7377 data are displayed as null-terminated strings and arrays of single-byte data
7378 are displayed as fixed-length strings. Other values are displayed in their
7381 Without this format, @value{GDBN} displays pointers to and arrays of
7382 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7383 strings. Single-byte members of a vector are displayed as an integer
7387 @cindex raw printing
7388 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7389 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7390 Printing}). This typically results in a higher-level display of the
7391 value's contents. The @samp{r} format bypasses any Python
7392 pretty-printer which might exist.
7395 For example, to print the program counter in hex (@pxref{Registers}), type
7402 Note that no space is required before the slash; this is because command
7403 names in @value{GDBN} cannot contain a slash.
7405 To reprint the last value in the value history with a different format,
7406 you can use the @code{print} command with just a format and no
7407 expression. For example, @samp{p/x} reprints the last value in hex.
7410 @section Examining Memory
7412 You can use the command @code{x} (for ``examine'') to examine memory in
7413 any of several formats, independently of your program's data types.
7415 @cindex examining memory
7417 @kindex x @r{(examine memory)}
7418 @item x/@var{nfu} @var{addr}
7421 Use the @code{x} command to examine memory.
7424 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7425 much memory to display and how to format it; @var{addr} is an
7426 expression giving the address where you want to start displaying memory.
7427 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7428 Several commands set convenient defaults for @var{addr}.
7431 @item @var{n}, the repeat count
7432 The repeat count is a decimal integer; the default is 1. It specifies
7433 how much memory (counting by units @var{u}) to display.
7434 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7437 @item @var{f}, the display format
7438 The display format is one of the formats used by @code{print}
7439 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7440 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7441 The default is @samp{x} (hexadecimal) initially. The default changes
7442 each time you use either @code{x} or @code{print}.
7444 @item @var{u}, the unit size
7445 The unit size is any of
7451 Halfwords (two bytes).
7453 Words (four bytes). This is the initial default.
7455 Giant words (eight bytes).
7458 Each time you specify a unit size with @code{x}, that size becomes the
7459 default unit the next time you use @code{x}. For the @samp{i} format,
7460 the unit size is ignored and is normally not written. For the @samp{s} format,
7461 the unit size defaults to @samp{b}, unless it is explicitly given.
7462 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7463 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7464 Note that the results depend on the programming language of the
7465 current compilation unit. If the language is C, the @samp{s}
7466 modifier will use the UTF-16 encoding while @samp{w} will use
7467 UTF-32. The encoding is set by the programming language and cannot
7470 @item @var{addr}, starting display address
7471 @var{addr} is the address where you want @value{GDBN} to begin displaying
7472 memory. The expression need not have a pointer value (though it may);
7473 it is always interpreted as an integer address of a byte of memory.
7474 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7475 @var{addr} is usually just after the last address examined---but several
7476 other commands also set the default address: @code{info breakpoints} (to
7477 the address of the last breakpoint listed), @code{info line} (to the
7478 starting address of a line), and @code{print} (if you use it to display
7479 a value from memory).
7482 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7483 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7484 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7485 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7486 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7488 Since the letters indicating unit sizes are all distinct from the
7489 letters specifying output formats, you do not have to remember whether
7490 unit size or format comes first; either order works. The output
7491 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7492 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7494 Even though the unit size @var{u} is ignored for the formats @samp{s}
7495 and @samp{i}, you might still want to use a count @var{n}; for example,
7496 @samp{3i} specifies that you want to see three machine instructions,
7497 including any operands. For convenience, especially when used with
7498 the @code{display} command, the @samp{i} format also prints branch delay
7499 slot instructions, if any, beyond the count specified, which immediately
7500 follow the last instruction that is within the count. The command
7501 @code{disassemble} gives an alternative way of inspecting machine
7502 instructions; see @ref{Machine Code,,Source and Machine Code}.
7504 All the defaults for the arguments to @code{x} are designed to make it
7505 easy to continue scanning memory with minimal specifications each time
7506 you use @code{x}. For example, after you have inspected three machine
7507 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7508 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7509 the repeat count @var{n} is used again; the other arguments default as
7510 for successive uses of @code{x}.
7512 When examining machine instructions, the instruction at current program
7513 counter is shown with a @code{=>} marker. For example:
7516 (@value{GDBP}) x/5i $pc-6
7517 0x804837f <main+11>: mov %esp,%ebp
7518 0x8048381 <main+13>: push %ecx
7519 0x8048382 <main+14>: sub $0x4,%esp
7520 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7521 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7524 @cindex @code{$_}, @code{$__}, and value history
7525 The addresses and contents printed by the @code{x} command are not saved
7526 in the value history because there is often too much of them and they
7527 would get in the way. Instead, @value{GDBN} makes these values available for
7528 subsequent use in expressions as values of the convenience variables
7529 @code{$_} and @code{$__}. After an @code{x} command, the last address
7530 examined is available for use in expressions in the convenience variable
7531 @code{$_}. The contents of that address, as examined, are available in
7532 the convenience variable @code{$__}.
7534 If the @code{x} command has a repeat count, the address and contents saved
7535 are from the last memory unit printed; this is not the same as the last
7536 address printed if several units were printed on the last line of output.
7538 @cindex remote memory comparison
7539 @cindex verify remote memory image
7540 When you are debugging a program running on a remote target machine
7541 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7542 remote machine's memory against the executable file you downloaded to
7543 the target. The @code{compare-sections} command is provided for such
7547 @kindex compare-sections
7548 @item compare-sections @r{[}@var{section-name}@r{]}
7549 Compare the data of a loadable section @var{section-name} in the
7550 executable file of the program being debugged with the same section in
7551 the remote machine's memory, and report any mismatches. With no
7552 arguments, compares all loadable sections. This command's
7553 availability depends on the target's support for the @code{"qCRC"}
7558 @section Automatic Display
7559 @cindex automatic display
7560 @cindex display of expressions
7562 If you find that you want to print the value of an expression frequently
7563 (to see how it changes), you might want to add it to the @dfn{automatic
7564 display list} so that @value{GDBN} prints its value each time your program stops.
7565 Each expression added to the list is given a number to identify it;
7566 to remove an expression from the list, you specify that number.
7567 The automatic display looks like this:
7571 3: bar[5] = (struct hack *) 0x3804
7575 This display shows item numbers, expressions and their current values. As with
7576 displays you request manually using @code{x} or @code{print}, you can
7577 specify the output format you prefer; in fact, @code{display} decides
7578 whether to use @code{print} or @code{x} depending your format
7579 specification---it uses @code{x} if you specify either the @samp{i}
7580 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7584 @item display @var{expr}
7585 Add the expression @var{expr} to the list of expressions to display
7586 each time your program stops. @xref{Expressions, ,Expressions}.
7588 @code{display} does not repeat if you press @key{RET} again after using it.
7590 @item display/@var{fmt} @var{expr}
7591 For @var{fmt} specifying only a display format and not a size or
7592 count, add the expression @var{expr} to the auto-display list but
7593 arrange to display it each time in the specified format @var{fmt}.
7594 @xref{Output Formats,,Output Formats}.
7596 @item display/@var{fmt} @var{addr}
7597 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7598 number of units, add the expression @var{addr} as a memory address to
7599 be examined each time your program stops. Examining means in effect
7600 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7603 For example, @samp{display/i $pc} can be helpful, to see the machine
7604 instruction about to be executed each time execution stops (@samp{$pc}
7605 is a common name for the program counter; @pxref{Registers, ,Registers}).
7608 @kindex delete display
7610 @item undisplay @var{dnums}@dots{}
7611 @itemx delete display @var{dnums}@dots{}
7612 Remove item numbers @var{dnums} from the list of expressions to display.
7614 @code{undisplay} does not repeat if you press @key{RET} after using it.
7615 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7617 @kindex disable display
7618 @item disable display @var{dnums}@dots{}
7619 Disable the display of item numbers @var{dnums}. A disabled display
7620 item is not printed automatically, but is not forgotten. It may be
7621 enabled again later.
7623 @kindex enable display
7624 @item enable display @var{dnums}@dots{}
7625 Enable display of item numbers @var{dnums}. It becomes effective once
7626 again in auto display of its expression, until you specify otherwise.
7629 Display the current values of the expressions on the list, just as is
7630 done when your program stops.
7632 @kindex info display
7634 Print the list of expressions previously set up to display
7635 automatically, each one with its item number, but without showing the
7636 values. This includes disabled expressions, which are marked as such.
7637 It also includes expressions which would not be displayed right now
7638 because they refer to automatic variables not currently available.
7641 @cindex display disabled out of scope
7642 If a display expression refers to local variables, then it does not make
7643 sense outside the lexical context for which it was set up. Such an
7644 expression is disabled when execution enters a context where one of its
7645 variables is not defined. For example, if you give the command
7646 @code{display last_char} while inside a function with an argument
7647 @code{last_char}, @value{GDBN} displays this argument while your program
7648 continues to stop inside that function. When it stops elsewhere---where
7649 there is no variable @code{last_char}---the display is disabled
7650 automatically. The next time your program stops where @code{last_char}
7651 is meaningful, you can enable the display expression once again.
7653 @node Print Settings
7654 @section Print Settings
7656 @cindex format options
7657 @cindex print settings
7658 @value{GDBN} provides the following ways to control how arrays, structures,
7659 and symbols are printed.
7662 These settings are useful for debugging programs in any language:
7666 @item set print address
7667 @itemx set print address on
7668 @cindex print/don't print memory addresses
7669 @value{GDBN} prints memory addresses showing the location of stack
7670 traces, structure values, pointer values, breakpoints, and so forth,
7671 even when it also displays the contents of those addresses. The default
7672 is @code{on}. For example, this is what a stack frame display looks like with
7673 @code{set print address on}:
7678 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7680 530 if (lquote != def_lquote)
7684 @item set print address off
7685 Do not print addresses when displaying their contents. For example,
7686 this is the same stack frame displayed with @code{set print address off}:
7690 (@value{GDBP}) set print addr off
7692 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7693 530 if (lquote != def_lquote)
7697 You can use @samp{set print address off} to eliminate all machine
7698 dependent displays from the @value{GDBN} interface. For example, with
7699 @code{print address off}, you should get the same text for backtraces on
7700 all machines---whether or not they involve pointer arguments.
7703 @item show print address
7704 Show whether or not addresses are to be printed.
7707 When @value{GDBN} prints a symbolic address, it normally prints the
7708 closest earlier symbol plus an offset. If that symbol does not uniquely
7709 identify the address (for example, it is a name whose scope is a single
7710 source file), you may need to clarify. One way to do this is with
7711 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7712 you can set @value{GDBN} to print the source file and line number when
7713 it prints a symbolic address:
7716 @item set print symbol-filename on
7717 @cindex source file and line of a symbol
7718 @cindex symbol, source file and line
7719 Tell @value{GDBN} to print the source file name and line number of a
7720 symbol in the symbolic form of an address.
7722 @item set print symbol-filename off
7723 Do not print source file name and line number of a symbol. This is the
7726 @item show print symbol-filename
7727 Show whether or not @value{GDBN} will print the source file name and
7728 line number of a symbol in the symbolic form of an address.
7731 Another situation where it is helpful to show symbol filenames and line
7732 numbers is when disassembling code; @value{GDBN} shows you the line
7733 number and source file that corresponds to each instruction.
7735 Also, you may wish to see the symbolic form only if the address being
7736 printed is reasonably close to the closest earlier symbol:
7739 @item set print max-symbolic-offset @var{max-offset}
7740 @cindex maximum value for offset of closest symbol
7741 Tell @value{GDBN} to only display the symbolic form of an address if the
7742 offset between the closest earlier symbol and the address is less than
7743 @var{max-offset}. The default is 0, which tells @value{GDBN}
7744 to always print the symbolic form of an address if any symbol precedes it.
7746 @item show print max-symbolic-offset
7747 Ask how large the maximum offset is that @value{GDBN} prints in a
7751 @cindex wild pointer, interpreting
7752 @cindex pointer, finding referent
7753 If you have a pointer and you are not sure where it points, try
7754 @samp{set print symbol-filename on}. Then you can determine the name
7755 and source file location of the variable where it points, using
7756 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7757 For example, here @value{GDBN} shows that a variable @code{ptt} points
7758 at another variable @code{t}, defined in @file{hi2.c}:
7761 (@value{GDBP}) set print symbol-filename on
7762 (@value{GDBP}) p/a ptt
7763 $4 = 0xe008 <t in hi2.c>
7767 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7768 does not show the symbol name and filename of the referent, even with
7769 the appropriate @code{set print} options turned on.
7772 Other settings control how different kinds of objects are printed:
7775 @item set print array
7776 @itemx set print array on
7777 @cindex pretty print arrays
7778 Pretty print arrays. This format is more convenient to read,
7779 but uses more space. The default is off.
7781 @item set print array off
7782 Return to compressed format for arrays.
7784 @item show print array
7785 Show whether compressed or pretty format is selected for displaying
7788 @cindex print array indexes
7789 @item set print array-indexes
7790 @itemx set print array-indexes on
7791 Print the index of each element when displaying arrays. May be more
7792 convenient to locate a given element in the array or quickly find the
7793 index of a given element in that printed array. The default is off.
7795 @item set print array-indexes off
7796 Stop printing element indexes when displaying arrays.
7798 @item show print array-indexes
7799 Show whether the index of each element is printed when displaying
7802 @item set print elements @var{number-of-elements}
7803 @cindex number of array elements to print
7804 @cindex limit on number of printed array elements
7805 Set a limit on how many elements of an array @value{GDBN} will print.
7806 If @value{GDBN} is printing a large array, it stops printing after it has
7807 printed the number of elements set by the @code{set print elements} command.
7808 This limit also applies to the display of strings.
7809 When @value{GDBN} starts, this limit is set to 200.
7810 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7812 @item show print elements
7813 Display the number of elements of a large array that @value{GDBN} will print.
7814 If the number is 0, then the printing is unlimited.
7816 @item set print frame-arguments @var{value}
7817 @kindex set print frame-arguments
7818 @cindex printing frame argument values
7819 @cindex print all frame argument values
7820 @cindex print frame argument values for scalars only
7821 @cindex do not print frame argument values
7822 This command allows to control how the values of arguments are printed
7823 when the debugger prints a frame (@pxref{Frames}). The possible
7828 The values of all arguments are printed.
7831 Print the value of an argument only if it is a scalar. The value of more
7832 complex arguments such as arrays, structures, unions, etc, is replaced
7833 by @code{@dots{}}. This is the default. Here is an example where
7834 only scalar arguments are shown:
7837 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7842 None of the argument values are printed. Instead, the value of each argument
7843 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7846 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7851 By default, only scalar arguments are printed. This command can be used
7852 to configure the debugger to print the value of all arguments, regardless
7853 of their type. However, it is often advantageous to not print the value
7854 of more complex parameters. For instance, it reduces the amount of
7855 information printed in each frame, making the backtrace more readable.
7856 Also, it improves performance when displaying Ada frames, because
7857 the computation of large arguments can sometimes be CPU-intensive,
7858 especially in large applications. Setting @code{print frame-arguments}
7859 to @code{scalars} (the default) or @code{none} avoids this computation,
7860 thus speeding up the display of each Ada frame.
7862 @item show print frame-arguments
7863 Show how the value of arguments should be displayed when printing a frame.
7865 @item set print repeats
7866 @cindex repeated array elements
7867 Set the threshold for suppressing display of repeated array
7868 elements. When the number of consecutive identical elements of an
7869 array exceeds the threshold, @value{GDBN} prints the string
7870 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7871 identical repetitions, instead of displaying the identical elements
7872 themselves. Setting the threshold to zero will cause all elements to
7873 be individually printed. The default threshold is 10.
7875 @item show print repeats
7876 Display the current threshold for printing repeated identical
7879 @item set print null-stop
7880 @cindex @sc{null} elements in arrays
7881 Cause @value{GDBN} to stop printing the characters of an array when the first
7882 @sc{null} is encountered. This is useful when large arrays actually
7883 contain only short strings.
7886 @item show print null-stop
7887 Show whether @value{GDBN} stops printing an array on the first
7888 @sc{null} character.
7890 @item set print pretty on
7891 @cindex print structures in indented form
7892 @cindex indentation in structure display
7893 Cause @value{GDBN} to print structures in an indented format with one member
7894 per line, like this:
7909 @item set print pretty off
7910 Cause @value{GDBN} to print structures in a compact format, like this:
7914 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7915 meat = 0x54 "Pork"@}
7920 This is the default format.
7922 @item show print pretty
7923 Show which format @value{GDBN} is using to print structures.
7925 @item set print sevenbit-strings on
7926 @cindex eight-bit characters in strings
7927 @cindex octal escapes in strings
7928 Print using only seven-bit characters; if this option is set,
7929 @value{GDBN} displays any eight-bit characters (in strings or
7930 character values) using the notation @code{\}@var{nnn}. This setting is
7931 best if you are working in English (@sc{ascii}) and you use the
7932 high-order bit of characters as a marker or ``meta'' bit.
7934 @item set print sevenbit-strings off
7935 Print full eight-bit characters. This allows the use of more
7936 international character sets, and is the default.
7938 @item show print sevenbit-strings
7939 Show whether or not @value{GDBN} is printing only seven-bit characters.
7941 @item set print union on
7942 @cindex unions in structures, printing
7943 Tell @value{GDBN} to print unions which are contained in structures
7944 and other unions. This is the default setting.
7946 @item set print union off
7947 Tell @value{GDBN} not to print unions which are contained in
7948 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7951 @item show print union
7952 Ask @value{GDBN} whether or not it will print unions which are contained in
7953 structures and other unions.
7955 For example, given the declarations
7958 typedef enum @{Tree, Bug@} Species;
7959 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7960 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7971 struct thing foo = @{Tree, @{Acorn@}@};
7975 with @code{set print union on} in effect @samp{p foo} would print
7978 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7982 and with @code{set print union off} in effect it would print
7985 $1 = @{it = Tree, form = @{...@}@}
7989 @code{set print union} affects programs written in C-like languages
7995 These settings are of interest when debugging C@t{++} programs:
7998 @cindex demangling C@t{++} names
7999 @item set print demangle
8000 @itemx set print demangle on
8001 Print C@t{++} names in their source form rather than in the encoded
8002 (``mangled'') form passed to the assembler and linker for type-safe
8003 linkage. The default is on.
8005 @item show print demangle
8006 Show whether C@t{++} names are printed in mangled or demangled form.
8008 @item set print asm-demangle
8009 @itemx set print asm-demangle on
8010 Print C@t{++} names in their source form rather than their mangled form, even
8011 in assembler code printouts such as instruction disassemblies.
8014 @item show print asm-demangle
8015 Show whether C@t{++} names in assembly listings are printed in mangled
8018 @cindex C@t{++} symbol decoding style
8019 @cindex symbol decoding style, C@t{++}
8020 @kindex set demangle-style
8021 @item set demangle-style @var{style}
8022 Choose among several encoding schemes used by different compilers to
8023 represent C@t{++} names. The choices for @var{style} are currently:
8027 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8030 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8031 This is the default.
8034 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8037 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8040 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8041 @strong{Warning:} this setting alone is not sufficient to allow
8042 debugging @code{cfront}-generated executables. @value{GDBN} would
8043 require further enhancement to permit that.
8046 If you omit @var{style}, you will see a list of possible formats.
8048 @item show demangle-style
8049 Display the encoding style currently in use for decoding C@t{++} symbols.
8051 @item set print object
8052 @itemx set print object on
8053 @cindex derived type of an object, printing
8054 @cindex display derived types
8055 When displaying a pointer to an object, identify the @emph{actual}
8056 (derived) type of the object rather than the @emph{declared} type, using
8057 the virtual function table.
8059 @item set print object off
8060 Display only the declared type of objects, without reference to the
8061 virtual function table. This is the default setting.
8063 @item show print object
8064 Show whether actual, or declared, object types are displayed.
8066 @item set print static-members
8067 @itemx set print static-members on
8068 @cindex static members of C@t{++} objects
8069 Print static members when displaying a C@t{++} object. The default is on.
8071 @item set print static-members off
8072 Do not print static members when displaying a C@t{++} object.
8074 @item show print static-members
8075 Show whether C@t{++} static members are printed or not.
8077 @item set print pascal_static-members
8078 @itemx set print pascal_static-members on
8079 @cindex static members of Pascal objects
8080 @cindex Pascal objects, static members display
8081 Print static members when displaying a Pascal object. The default is on.
8083 @item set print pascal_static-members off
8084 Do not print static members when displaying a Pascal object.
8086 @item show print pascal_static-members
8087 Show whether Pascal static members are printed or not.
8089 @c These don't work with HP ANSI C++ yet.
8090 @item set print vtbl
8091 @itemx set print vtbl on
8092 @cindex pretty print C@t{++} virtual function tables
8093 @cindex virtual functions (C@t{++}) display
8094 @cindex VTBL display
8095 Pretty print C@t{++} virtual function tables. The default is off.
8096 (The @code{vtbl} commands do not work on programs compiled with the HP
8097 ANSI C@t{++} compiler (@code{aCC}).)
8099 @item set print vtbl off
8100 Do not pretty print C@t{++} virtual function tables.
8102 @item show print vtbl
8103 Show whether C@t{++} virtual function tables are pretty printed, or not.
8106 @node Pretty Printing
8107 @section Pretty Printing
8109 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8110 Python code. It greatly simplifies the display of complex objects. This
8111 mechanism works for both MI and the CLI.
8113 For example, here is how a C@t{++} @code{std::string} looks without a
8117 (@value{GDBP}) print s
8119 static npos = 4294967295,
8121 <std::allocator<char>> = @{
8122 <__gnu_cxx::new_allocator<char>> = @{
8123 <No data fields>@}, <No data fields>
8125 members of std::basic_string<char, std::char_traits<char>,
8126 std::allocator<char> >::_Alloc_hider:
8127 _M_p = 0x804a014 "abcd"
8132 With a pretty-printer for @code{std::string} only the contents are printed:
8135 (@value{GDBP}) print s
8139 For implementing pretty printers for new types you should read the Python API
8140 details (@pxref{Pretty Printing API}).
8143 @section Value History
8145 @cindex value history
8146 @cindex history of values printed by @value{GDBN}
8147 Values printed by the @code{print} command are saved in the @value{GDBN}
8148 @dfn{value history}. This allows you to refer to them in other expressions.
8149 Values are kept until the symbol table is re-read or discarded
8150 (for example with the @code{file} or @code{symbol-file} commands).
8151 When the symbol table changes, the value history is discarded,
8152 since the values may contain pointers back to the types defined in the
8157 @cindex history number
8158 The values printed are given @dfn{history numbers} by which you can
8159 refer to them. These are successive integers starting with one.
8160 @code{print} shows you the history number assigned to a value by
8161 printing @samp{$@var{num} = } before the value; here @var{num} is the
8164 To refer to any previous value, use @samp{$} followed by the value's
8165 history number. The way @code{print} labels its output is designed to
8166 remind you of this. Just @code{$} refers to the most recent value in
8167 the history, and @code{$$} refers to the value before that.
8168 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8169 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8170 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8172 For example, suppose you have just printed a pointer to a structure and
8173 want to see the contents of the structure. It suffices to type
8179 If you have a chain of structures where the component @code{next} points
8180 to the next one, you can print the contents of the next one with this:
8187 You can print successive links in the chain by repeating this
8188 command---which you can do by just typing @key{RET}.
8190 Note that the history records values, not expressions. If the value of
8191 @code{x} is 4 and you type these commands:
8199 then the value recorded in the value history by the @code{print} command
8200 remains 4 even though the value of @code{x} has changed.
8205 Print the last ten values in the value history, with their item numbers.
8206 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8207 values} does not change the history.
8209 @item show values @var{n}
8210 Print ten history values centered on history item number @var{n}.
8213 Print ten history values just after the values last printed. If no more
8214 values are available, @code{show values +} produces no display.
8217 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8218 same effect as @samp{show values +}.
8220 @node Convenience Vars
8221 @section Convenience Variables
8223 @cindex convenience variables
8224 @cindex user-defined variables
8225 @value{GDBN} provides @dfn{convenience variables} that you can use within
8226 @value{GDBN} to hold on to a value and refer to it later. These variables
8227 exist entirely within @value{GDBN}; they are not part of your program, and
8228 setting a convenience variable has no direct effect on further execution
8229 of your program. That is why you can use them freely.
8231 Convenience variables are prefixed with @samp{$}. Any name preceded by
8232 @samp{$} can be used for a convenience variable, unless it is one of
8233 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8234 (Value history references, in contrast, are @emph{numbers} preceded
8235 by @samp{$}. @xref{Value History, ,Value History}.)
8237 You can save a value in a convenience variable with an assignment
8238 expression, just as you would set a variable in your program.
8242 set $foo = *object_ptr
8246 would save in @code{$foo} the value contained in the object pointed to by
8249 Using a convenience variable for the first time creates it, but its
8250 value is @code{void} until you assign a new value. You can alter the
8251 value with another assignment at any time.
8253 Convenience variables have no fixed types. You can assign a convenience
8254 variable any type of value, including structures and arrays, even if
8255 that variable already has a value of a different type. The convenience
8256 variable, when used as an expression, has the type of its current value.
8259 @kindex show convenience
8260 @cindex show all user variables
8261 @item show convenience
8262 Print a list of convenience variables used so far, and their values.
8263 Abbreviated @code{show conv}.
8265 @kindex init-if-undefined
8266 @cindex convenience variables, initializing
8267 @item init-if-undefined $@var{variable} = @var{expression}
8268 Set a convenience variable if it has not already been set. This is useful
8269 for user-defined commands that keep some state. It is similar, in concept,
8270 to using local static variables with initializers in C (except that
8271 convenience variables are global). It can also be used to allow users to
8272 override default values used in a command script.
8274 If the variable is already defined then the expression is not evaluated so
8275 any side-effects do not occur.
8278 One of the ways to use a convenience variable is as a counter to be
8279 incremented or a pointer to be advanced. For example, to print
8280 a field from successive elements of an array of structures:
8284 print bar[$i++]->contents
8288 Repeat that command by typing @key{RET}.
8290 Some convenience variables are created automatically by @value{GDBN} and given
8291 values likely to be useful.
8294 @vindex $_@r{, convenience variable}
8296 The variable @code{$_} is automatically set by the @code{x} command to
8297 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8298 commands which provide a default address for @code{x} to examine also
8299 set @code{$_} to that address; these commands include @code{info line}
8300 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8301 except when set by the @code{x} command, in which case it is a pointer
8302 to the type of @code{$__}.
8304 @vindex $__@r{, convenience variable}
8306 The variable @code{$__} is automatically set by the @code{x} command
8307 to the value found in the last address examined. Its type is chosen
8308 to match the format in which the data was printed.
8311 @vindex $_exitcode@r{, convenience variable}
8312 The variable @code{$_exitcode} is automatically set to the exit code when
8313 the program being debugged terminates.
8316 @vindex $_sdata@r{, inspect, convenience variable}
8317 The variable @code{$_sdata} contains extra collected static tracepoint
8318 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8319 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8320 if extra static tracepoint data has not been collected.
8323 @vindex $_siginfo@r{, convenience variable}
8324 The variable @code{$_siginfo} contains extra signal information
8325 (@pxref{extra signal information}). Note that @code{$_siginfo}
8326 could be empty, if the application has not yet received any signals.
8327 For example, it will be empty before you execute the @code{run} command.
8330 @vindex $_tlb@r{, convenience variable}
8331 The variable @code{$_tlb} is automatically set when debugging
8332 applications running on MS-Windows in native mode or connected to
8333 gdbserver that supports the @code{qGetTIBAddr} request.
8334 @xref{General Query Packets}.
8335 This variable contains the address of the thread information block.
8339 On HP-UX systems, if you refer to a function or variable name that
8340 begins with a dollar sign, @value{GDBN} searches for a user or system
8341 name first, before it searches for a convenience variable.
8343 @cindex convenience functions
8344 @value{GDBN} also supplies some @dfn{convenience functions}. These
8345 have a syntax similar to convenience variables. A convenience
8346 function can be used in an expression just like an ordinary function;
8347 however, a convenience function is implemented internally to
8352 @kindex help function
8353 @cindex show all convenience functions
8354 Print a list of all convenience functions.
8361 You can refer to machine register contents, in expressions, as variables
8362 with names starting with @samp{$}. The names of registers are different
8363 for each machine; use @code{info registers} to see the names used on
8367 @kindex info registers
8368 @item info registers
8369 Print the names and values of all registers except floating-point
8370 and vector registers (in the selected stack frame).
8372 @kindex info all-registers
8373 @cindex floating point registers
8374 @item info all-registers
8375 Print the names and values of all registers, including floating-point
8376 and vector registers (in the selected stack frame).
8378 @item info registers @var{regname} @dots{}
8379 Print the @dfn{relativized} value of each specified register @var{regname}.
8380 As discussed in detail below, register values are normally relative to
8381 the selected stack frame. @var{regname} may be any register name valid on
8382 the machine you are using, with or without the initial @samp{$}.
8385 @cindex stack pointer register
8386 @cindex program counter register
8387 @cindex process status register
8388 @cindex frame pointer register
8389 @cindex standard registers
8390 @value{GDBN} has four ``standard'' register names that are available (in
8391 expressions) on most machines---whenever they do not conflict with an
8392 architecture's canonical mnemonics for registers. The register names
8393 @code{$pc} and @code{$sp} are used for the program counter register and
8394 the stack pointer. @code{$fp} is used for a register that contains a
8395 pointer to the current stack frame, and @code{$ps} is used for a
8396 register that contains the processor status. For example,
8397 you could print the program counter in hex with
8404 or print the instruction to be executed next with
8411 or add four to the stack pointer@footnote{This is a way of removing
8412 one word from the stack, on machines where stacks grow downward in
8413 memory (most machines, nowadays). This assumes that the innermost
8414 stack frame is selected; setting @code{$sp} is not allowed when other
8415 stack frames are selected. To pop entire frames off the stack,
8416 regardless of machine architecture, use @code{return};
8417 see @ref{Returning, ,Returning from a Function}.} with
8423 Whenever possible, these four standard register names are available on
8424 your machine even though the machine has different canonical mnemonics,
8425 so long as there is no conflict. The @code{info registers} command
8426 shows the canonical names. For example, on the SPARC, @code{info
8427 registers} displays the processor status register as @code{$psr} but you
8428 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8429 is an alias for the @sc{eflags} register.
8431 @value{GDBN} always considers the contents of an ordinary register as an
8432 integer when the register is examined in this way. Some machines have
8433 special registers which can hold nothing but floating point; these
8434 registers are considered to have floating point values. There is no way
8435 to refer to the contents of an ordinary register as floating point value
8436 (although you can @emph{print} it as a floating point value with
8437 @samp{print/f $@var{regname}}).
8439 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8440 means that the data format in which the register contents are saved by
8441 the operating system is not the same one that your program normally
8442 sees. For example, the registers of the 68881 floating point
8443 coprocessor are always saved in ``extended'' (raw) format, but all C
8444 programs expect to work with ``double'' (virtual) format. In such
8445 cases, @value{GDBN} normally works with the virtual format only (the format
8446 that makes sense for your program), but the @code{info registers} command
8447 prints the data in both formats.
8449 @cindex SSE registers (x86)
8450 @cindex MMX registers (x86)
8451 Some machines have special registers whose contents can be interpreted
8452 in several different ways. For example, modern x86-based machines
8453 have SSE and MMX registers that can hold several values packed
8454 together in several different formats. @value{GDBN} refers to such
8455 registers in @code{struct} notation:
8458 (@value{GDBP}) print $xmm1
8460 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8461 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8462 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8463 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8464 v4_int32 = @{0, 20657912, 11, 13@},
8465 v2_int64 = @{88725056443645952, 55834574859@},
8466 uint128 = 0x0000000d0000000b013b36f800000000
8471 To set values of such registers, you need to tell @value{GDBN} which
8472 view of the register you wish to change, as if you were assigning
8473 value to a @code{struct} member:
8476 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8479 Normally, register values are relative to the selected stack frame
8480 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8481 value that the register would contain if all stack frames farther in
8482 were exited and their saved registers restored. In order to see the
8483 true contents of hardware registers, you must select the innermost
8484 frame (with @samp{frame 0}).
8486 However, @value{GDBN} must deduce where registers are saved, from the machine
8487 code generated by your compiler. If some registers are not saved, or if
8488 @value{GDBN} is unable to locate the saved registers, the selected stack
8489 frame makes no difference.
8491 @node Floating Point Hardware
8492 @section Floating Point Hardware
8493 @cindex floating point
8495 Depending on the configuration, @value{GDBN} may be able to give
8496 you more information about the status of the floating point hardware.
8501 Display hardware-dependent information about the floating
8502 point unit. The exact contents and layout vary depending on the
8503 floating point chip. Currently, @samp{info float} is supported on
8504 the ARM and x86 machines.
8508 @section Vector Unit
8511 Depending on the configuration, @value{GDBN} may be able to give you
8512 more information about the status of the vector unit.
8517 Display information about the vector unit. The exact contents and
8518 layout vary depending on the hardware.
8521 @node OS Information
8522 @section Operating System Auxiliary Information
8523 @cindex OS information
8525 @value{GDBN} provides interfaces to useful OS facilities that can help
8526 you debug your program.
8528 @cindex @code{ptrace} system call
8529 @cindex @code{struct user} contents
8530 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8531 machines), it interfaces with the inferior via the @code{ptrace}
8532 system call. The operating system creates a special sata structure,
8533 called @code{struct user}, for this interface. You can use the
8534 command @code{info udot} to display the contents of this data
8540 Display the contents of the @code{struct user} maintained by the OS
8541 kernel for the program being debugged. @value{GDBN} displays the
8542 contents of @code{struct user} as a list of hex numbers, similar to
8543 the @code{examine} command.
8546 @cindex auxiliary vector
8547 @cindex vector, auxiliary
8548 Some operating systems supply an @dfn{auxiliary vector} to programs at
8549 startup. This is akin to the arguments and environment that you
8550 specify for a program, but contains a system-dependent variety of
8551 binary values that tell system libraries important details about the
8552 hardware, operating system, and process. Each value's purpose is
8553 identified by an integer tag; the meanings are well-known but system-specific.
8554 Depending on the configuration and operating system facilities,
8555 @value{GDBN} may be able to show you this information. For remote
8556 targets, this functionality may further depend on the remote stub's
8557 support of the @samp{qXfer:auxv:read} packet, see
8558 @ref{qXfer auxiliary vector read}.
8563 Display the auxiliary vector of the inferior, which can be either a
8564 live process or a core dump file. @value{GDBN} prints each tag value
8565 numerically, and also shows names and text descriptions for recognized
8566 tags. Some values in the vector are numbers, some bit masks, and some
8567 pointers to strings or other data. @value{GDBN} displays each value in the
8568 most appropriate form for a recognized tag, and in hexadecimal for
8569 an unrecognized tag.
8572 On some targets, @value{GDBN} can access operating-system-specific information
8573 and display it to user, without interpretation. For remote targets,
8574 this functionality depends on the remote stub's support of the
8575 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8580 List the types of OS information available for the target. If the
8581 target does not return a list of possible types, this command will
8584 @kindex info os processes
8585 @item info os processes
8586 Display the list of processes on the target. For each process,
8587 @value{GDBN} prints the process identifier, the name of the user, and
8588 the command corresponding to the process.
8591 @node Memory Region Attributes
8592 @section Memory Region Attributes
8593 @cindex memory region attributes
8595 @dfn{Memory region attributes} allow you to describe special handling
8596 required by regions of your target's memory. @value{GDBN} uses
8597 attributes to determine whether to allow certain types of memory
8598 accesses; whether to use specific width accesses; and whether to cache
8599 target memory. By default the description of memory regions is
8600 fetched from the target (if the current target supports this), but the
8601 user can override the fetched regions.
8603 Defined memory regions can be individually enabled and disabled. When a
8604 memory region is disabled, @value{GDBN} uses the default attributes when
8605 accessing memory in that region. Similarly, if no memory regions have
8606 been defined, @value{GDBN} uses the default attributes when accessing
8609 When a memory region is defined, it is given a number to identify it;
8610 to enable, disable, or remove a memory region, you specify that number.
8614 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8615 Define a memory region bounded by @var{lower} and @var{upper} with
8616 attributes @var{attributes}@dots{}, and add it to the list of regions
8617 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8618 case: it is treated as the target's maximum memory address.
8619 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8622 Discard any user changes to the memory regions and use target-supplied
8623 regions, if available, or no regions if the target does not support.
8626 @item delete mem @var{nums}@dots{}
8627 Remove memory regions @var{nums}@dots{} from the list of regions
8628 monitored by @value{GDBN}.
8631 @item disable mem @var{nums}@dots{}
8632 Disable monitoring of memory regions @var{nums}@dots{}.
8633 A disabled memory region is not forgotten.
8634 It may be enabled again later.
8637 @item enable mem @var{nums}@dots{}
8638 Enable monitoring of memory regions @var{nums}@dots{}.
8642 Print a table of all defined memory regions, with the following columns
8646 @item Memory Region Number
8647 @item Enabled or Disabled.
8648 Enabled memory regions are marked with @samp{y}.
8649 Disabled memory regions are marked with @samp{n}.
8652 The address defining the inclusive lower bound of the memory region.
8655 The address defining the exclusive upper bound of the memory region.
8658 The list of attributes set for this memory region.
8663 @subsection Attributes
8665 @subsubsection Memory Access Mode
8666 The access mode attributes set whether @value{GDBN} may make read or
8667 write accesses to a memory region.
8669 While these attributes prevent @value{GDBN} from performing invalid
8670 memory accesses, they do nothing to prevent the target system, I/O DMA,
8671 etc.@: from accessing memory.
8675 Memory is read only.
8677 Memory is write only.
8679 Memory is read/write. This is the default.
8682 @subsubsection Memory Access Size
8683 The access size attribute tells @value{GDBN} to use specific sized
8684 accesses in the memory region. Often memory mapped device registers
8685 require specific sized accesses. If no access size attribute is
8686 specified, @value{GDBN} may use accesses of any size.
8690 Use 8 bit memory accesses.
8692 Use 16 bit memory accesses.
8694 Use 32 bit memory accesses.
8696 Use 64 bit memory accesses.
8699 @c @subsubsection Hardware/Software Breakpoints
8700 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8701 @c will use hardware or software breakpoints for the internal breakpoints
8702 @c used by the step, next, finish, until, etc. commands.
8706 @c Always use hardware breakpoints
8707 @c @item swbreak (default)
8710 @subsubsection Data Cache
8711 The data cache attributes set whether @value{GDBN} will cache target
8712 memory. While this generally improves performance by reducing debug
8713 protocol overhead, it can lead to incorrect results because @value{GDBN}
8714 does not know about volatile variables or memory mapped device
8719 Enable @value{GDBN} to cache target memory.
8721 Disable @value{GDBN} from caching target memory. This is the default.
8724 @subsection Memory Access Checking
8725 @value{GDBN} can be instructed to refuse accesses to memory that is
8726 not explicitly described. This can be useful if accessing such
8727 regions has undesired effects for a specific target, or to provide
8728 better error checking. The following commands control this behaviour.
8731 @kindex set mem inaccessible-by-default
8732 @item set mem inaccessible-by-default [on|off]
8733 If @code{on} is specified, make @value{GDBN} treat memory not
8734 explicitly described by the memory ranges as non-existent and refuse accesses
8735 to such memory. The checks are only performed if there's at least one
8736 memory range defined. If @code{off} is specified, make @value{GDBN}
8737 treat the memory not explicitly described by the memory ranges as RAM.
8738 The default value is @code{on}.
8739 @kindex show mem inaccessible-by-default
8740 @item show mem inaccessible-by-default
8741 Show the current handling of accesses to unknown memory.
8745 @c @subsubsection Memory Write Verification
8746 @c The memory write verification attributes set whether @value{GDBN}
8747 @c will re-reads data after each write to verify the write was successful.
8751 @c @item noverify (default)
8754 @node Dump/Restore Files
8755 @section Copy Between Memory and a File
8756 @cindex dump/restore files
8757 @cindex append data to a file
8758 @cindex dump data to a file
8759 @cindex restore data from a file
8761 You can use the commands @code{dump}, @code{append}, and
8762 @code{restore} to copy data between target memory and a file. The
8763 @code{dump} and @code{append} commands write data to a file, and the
8764 @code{restore} command reads data from a file back into the inferior's
8765 memory. Files may be in binary, Motorola S-record, Intel hex, or
8766 Tektronix Hex format; however, @value{GDBN} can only append to binary
8772 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8773 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8774 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8775 or the value of @var{expr}, to @var{filename} in the given format.
8777 The @var{format} parameter may be any one of:
8784 Motorola S-record format.
8786 Tektronix Hex format.
8789 @value{GDBN} uses the same definitions of these formats as the
8790 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8791 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8795 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8796 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8797 Append the contents of memory from @var{start_addr} to @var{end_addr},
8798 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8799 (@value{GDBN} can only append data to files in raw binary form.)
8802 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8803 Restore the contents of file @var{filename} into memory. The
8804 @code{restore} command can automatically recognize any known @sc{bfd}
8805 file format, except for raw binary. To restore a raw binary file you
8806 must specify the optional keyword @code{binary} after the filename.
8808 If @var{bias} is non-zero, its value will be added to the addresses
8809 contained in the file. Binary files always start at address zero, so
8810 they will be restored at address @var{bias}. Other bfd files have
8811 a built-in location; they will be restored at offset @var{bias}
8814 If @var{start} and/or @var{end} are non-zero, then only data between
8815 file offset @var{start} and file offset @var{end} will be restored.
8816 These offsets are relative to the addresses in the file, before
8817 the @var{bias} argument is applied.
8821 @node Core File Generation
8822 @section How to Produce a Core File from Your Program
8823 @cindex dump core from inferior
8825 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8826 image of a running process and its process status (register values
8827 etc.). Its primary use is post-mortem debugging of a program that
8828 crashed while it ran outside a debugger. A program that crashes
8829 automatically produces a core file, unless this feature is disabled by
8830 the user. @xref{Files}, for information on invoking @value{GDBN} in
8831 the post-mortem debugging mode.
8833 Occasionally, you may wish to produce a core file of the program you
8834 are debugging in order to preserve a snapshot of its state.
8835 @value{GDBN} has a special command for that.
8839 @kindex generate-core-file
8840 @item generate-core-file [@var{file}]
8841 @itemx gcore [@var{file}]
8842 Produce a core dump of the inferior process. The optional argument
8843 @var{file} specifies the file name where to put the core dump. If not
8844 specified, the file name defaults to @file{core.@var{pid}}, where
8845 @var{pid} is the inferior process ID.
8847 Note that this command is implemented only for some systems (as of
8848 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8851 @node Character Sets
8852 @section Character Sets
8853 @cindex character sets
8855 @cindex translating between character sets
8856 @cindex host character set
8857 @cindex target character set
8859 If the program you are debugging uses a different character set to
8860 represent characters and strings than the one @value{GDBN} uses itself,
8861 @value{GDBN} can automatically translate between the character sets for
8862 you. The character set @value{GDBN} uses we call the @dfn{host
8863 character set}; the one the inferior program uses we call the
8864 @dfn{target character set}.
8866 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8867 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8868 remote protocol (@pxref{Remote Debugging}) to debug a program
8869 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8870 then the host character set is Latin-1, and the target character set is
8871 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8872 target-charset EBCDIC-US}, then @value{GDBN} translates between
8873 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8874 character and string literals in expressions.
8876 @value{GDBN} has no way to automatically recognize which character set
8877 the inferior program uses; you must tell it, using the @code{set
8878 target-charset} command, described below.
8880 Here are the commands for controlling @value{GDBN}'s character set
8884 @item set target-charset @var{charset}
8885 @kindex set target-charset
8886 Set the current target character set to @var{charset}. To display the
8887 list of supported target character sets, type
8888 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8890 @item set host-charset @var{charset}
8891 @kindex set host-charset
8892 Set the current host character set to @var{charset}.
8894 By default, @value{GDBN} uses a host character set appropriate to the
8895 system it is running on; you can override that default using the
8896 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8897 automatically determine the appropriate host character set. In this
8898 case, @value{GDBN} uses @samp{UTF-8}.
8900 @value{GDBN} can only use certain character sets as its host character
8901 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8902 @value{GDBN} will list the host character sets it supports.
8904 @item set charset @var{charset}
8906 Set the current host and target character sets to @var{charset}. As
8907 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8908 @value{GDBN} will list the names of the character sets that can be used
8909 for both host and target.
8912 @kindex show charset
8913 Show the names of the current host and target character sets.
8915 @item show host-charset
8916 @kindex show host-charset
8917 Show the name of the current host character set.
8919 @item show target-charset
8920 @kindex show target-charset
8921 Show the name of the current target character set.
8923 @item set target-wide-charset @var{charset}
8924 @kindex set target-wide-charset
8925 Set the current target's wide character set to @var{charset}. This is
8926 the character set used by the target's @code{wchar_t} type. To
8927 display the list of supported wide character sets, type
8928 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8930 @item show target-wide-charset
8931 @kindex show target-wide-charset
8932 Show the name of the current target's wide character set.
8935 Here is an example of @value{GDBN}'s character set support in action.
8936 Assume that the following source code has been placed in the file
8937 @file{charset-test.c}:
8943 = @{72, 101, 108, 108, 111, 44, 32, 119,
8944 111, 114, 108, 100, 33, 10, 0@};
8945 char ibm1047_hello[]
8946 = @{200, 133, 147, 147, 150, 107, 64, 166,
8947 150, 153, 147, 132, 90, 37, 0@};
8951 printf ("Hello, world!\n");
8955 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8956 containing the string @samp{Hello, world!} followed by a newline,
8957 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8959 We compile the program, and invoke the debugger on it:
8962 $ gcc -g charset-test.c -o charset-test
8963 $ gdb -nw charset-test
8964 GNU gdb 2001-12-19-cvs
8965 Copyright 2001 Free Software Foundation, Inc.
8970 We can use the @code{show charset} command to see what character sets
8971 @value{GDBN} is currently using to interpret and display characters and
8975 (@value{GDBP}) show charset
8976 The current host and target character set is `ISO-8859-1'.
8980 For the sake of printing this manual, let's use @sc{ascii} as our
8981 initial character set:
8983 (@value{GDBP}) set charset ASCII
8984 (@value{GDBP}) show charset
8985 The current host and target character set is `ASCII'.
8989 Let's assume that @sc{ascii} is indeed the correct character set for our
8990 host system --- in other words, let's assume that if @value{GDBN} prints
8991 characters using the @sc{ascii} character set, our terminal will display
8992 them properly. Since our current target character set is also
8993 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8996 (@value{GDBP}) print ascii_hello
8997 $1 = 0x401698 "Hello, world!\n"
8998 (@value{GDBP}) print ascii_hello[0]
9003 @value{GDBN} uses the target character set for character and string
9004 literals you use in expressions:
9007 (@value{GDBP}) print '+'
9012 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9015 @value{GDBN} relies on the user to tell it which character set the
9016 target program uses. If we print @code{ibm1047_hello} while our target
9017 character set is still @sc{ascii}, we get jibberish:
9020 (@value{GDBP}) print ibm1047_hello
9021 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9022 (@value{GDBP}) print ibm1047_hello[0]
9027 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9028 @value{GDBN} tells us the character sets it supports:
9031 (@value{GDBP}) set target-charset
9032 ASCII EBCDIC-US IBM1047 ISO-8859-1
9033 (@value{GDBP}) set target-charset
9036 We can select @sc{ibm1047} as our target character set, and examine the
9037 program's strings again. Now the @sc{ascii} string is wrong, but
9038 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9039 target character set, @sc{ibm1047}, to the host character set,
9040 @sc{ascii}, and they display correctly:
9043 (@value{GDBP}) set target-charset IBM1047
9044 (@value{GDBP}) show charset
9045 The current host character set is `ASCII'.
9046 The current target character set is `IBM1047'.
9047 (@value{GDBP}) print ascii_hello
9048 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9049 (@value{GDBP}) print ascii_hello[0]
9051 (@value{GDBP}) print ibm1047_hello
9052 $8 = 0x4016a8 "Hello, world!\n"
9053 (@value{GDBP}) print ibm1047_hello[0]
9058 As above, @value{GDBN} uses the target character set for character and
9059 string literals you use in expressions:
9062 (@value{GDBP}) print '+'
9067 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9070 @node Caching Remote Data
9071 @section Caching Data of Remote Targets
9072 @cindex caching data of remote targets
9074 @value{GDBN} caches data exchanged between the debugger and a
9075 remote target (@pxref{Remote Debugging}). Such caching generally improves
9076 performance, because it reduces the overhead of the remote protocol by
9077 bundling memory reads and writes into large chunks. Unfortunately, simply
9078 caching everything would lead to incorrect results, since @value{GDBN}
9079 does not necessarily know anything about volatile values, memory-mapped I/O
9080 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9081 memory can be changed @emph{while} a gdb command is executing.
9082 Therefore, by default, @value{GDBN} only caches data
9083 known to be on the stack@footnote{In non-stop mode, it is moderately
9084 rare for a running thread to modify the stack of a stopped thread
9085 in a way that would interfere with a backtrace, and caching of
9086 stack reads provides a significant speed up of remote backtraces.}.
9087 Other regions of memory can be explicitly marked as
9088 cacheable; see @pxref{Memory Region Attributes}.
9091 @kindex set remotecache
9092 @item set remotecache on
9093 @itemx set remotecache off
9094 This option no longer does anything; it exists for compatibility
9097 @kindex show remotecache
9098 @item show remotecache
9099 Show the current state of the obsolete remotecache flag.
9101 @kindex set stack-cache
9102 @item set stack-cache on
9103 @itemx set stack-cache off
9104 Enable or disable caching of stack accesses. When @code{ON}, use
9105 caching. By default, this option is @code{ON}.
9107 @kindex show stack-cache
9108 @item show stack-cache
9109 Show the current state of data caching for memory accesses.
9112 @item info dcache @r{[}line@r{]}
9113 Print the information about the data cache performance. The
9114 information displayed includes the dcache width and depth, and for
9115 each cache line, its number, address, and how many times it was
9116 referenced. This command is useful for debugging the data cache
9119 If a line number is specified, the contents of that line will be
9123 @node Searching Memory
9124 @section Search Memory
9125 @cindex searching memory
9127 Memory can be searched for a particular sequence of bytes with the
9128 @code{find} command.
9132 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9133 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9134 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9135 etc. The search begins at address @var{start_addr} and continues for either
9136 @var{len} bytes or through to @var{end_addr} inclusive.
9139 @var{s} and @var{n} are optional parameters.
9140 They may be specified in either order, apart or together.
9143 @item @var{s}, search query size
9144 The size of each search query value.
9150 halfwords (two bytes)
9154 giant words (eight bytes)
9157 All values are interpreted in the current language.
9158 This means, for example, that if the current source language is C/C@t{++}
9159 then searching for the string ``hello'' includes the trailing '\0'.
9161 If the value size is not specified, it is taken from the
9162 value's type in the current language.
9163 This is useful when one wants to specify the search
9164 pattern as a mixture of types.
9165 Note that this means, for example, that in the case of C-like languages
9166 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9167 which is typically four bytes.
9169 @item @var{n}, maximum number of finds
9170 The maximum number of matches to print. The default is to print all finds.
9173 You can use strings as search values. Quote them with double-quotes
9175 The string value is copied into the search pattern byte by byte,
9176 regardless of the endianness of the target and the size specification.
9178 The address of each match found is printed as well as a count of the
9179 number of matches found.
9181 The address of the last value found is stored in convenience variable
9183 A count of the number of matches is stored in @samp{$numfound}.
9185 For example, if stopped at the @code{printf} in this function:
9191 static char hello[] = "hello-hello";
9192 static struct @{ char c; short s; int i; @}
9193 __attribute__ ((packed)) mixed
9194 = @{ 'c', 0x1234, 0x87654321 @};
9195 printf ("%s\n", hello);
9200 you get during debugging:
9203 (gdb) find &hello[0], +sizeof(hello), "hello"
9204 0x804956d <hello.1620+6>
9206 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9207 0x8049567 <hello.1620>
9208 0x804956d <hello.1620+6>
9210 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9211 0x8049567 <hello.1620>
9213 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9214 0x8049560 <mixed.1625>
9216 (gdb) print $numfound
9219 $2 = (void *) 0x8049560
9222 @node Optimized Code
9223 @chapter Debugging Optimized Code
9224 @cindex optimized code, debugging
9225 @cindex debugging optimized code
9227 Almost all compilers support optimization. With optimization
9228 disabled, the compiler generates assembly code that corresponds
9229 directly to your source code, in a simplistic way. As the compiler
9230 applies more powerful optimizations, the generated assembly code
9231 diverges from your original source code. With help from debugging
9232 information generated by the compiler, @value{GDBN} can map from
9233 the running program back to constructs from your original source.
9235 @value{GDBN} is more accurate with optimization disabled. If you
9236 can recompile without optimization, it is easier to follow the
9237 progress of your program during debugging. But, there are many cases
9238 where you may need to debug an optimized version.
9240 When you debug a program compiled with @samp{-g -O}, remember that the
9241 optimizer has rearranged your code; the debugger shows you what is
9242 really there. Do not be too surprised when the execution path does not
9243 exactly match your source file! An extreme example: if you define a
9244 variable, but never use it, @value{GDBN} never sees that
9245 variable---because the compiler optimizes it out of existence.
9247 Some things do not work as well with @samp{-g -O} as with just
9248 @samp{-g}, particularly on machines with instruction scheduling. If in
9249 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9250 please report it to us as a bug (including a test case!).
9251 @xref{Variables}, for more information about debugging optimized code.
9254 * Inline Functions:: How @value{GDBN} presents inlining
9257 @node Inline Functions
9258 @section Inline Functions
9259 @cindex inline functions, debugging
9261 @dfn{Inlining} is an optimization that inserts a copy of the function
9262 body directly at each call site, instead of jumping to a shared
9263 routine. @value{GDBN} displays inlined functions just like
9264 non-inlined functions. They appear in backtraces. You can view their
9265 arguments and local variables, step into them with @code{step}, skip
9266 them with @code{next}, and escape from them with @code{finish}.
9267 You can check whether a function was inlined by using the
9268 @code{info frame} command.
9270 For @value{GDBN} to support inlined functions, the compiler must
9271 record information about inlining in the debug information ---
9272 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9273 other compilers do also. @value{GDBN} only supports inlined functions
9274 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9275 do not emit two required attributes (@samp{DW_AT_call_file} and
9276 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9277 function calls with earlier versions of @value{NGCC}. It instead
9278 displays the arguments and local variables of inlined functions as
9279 local variables in the caller.
9281 The body of an inlined function is directly included at its call site;
9282 unlike a non-inlined function, there are no instructions devoted to
9283 the call. @value{GDBN} still pretends that the call site and the
9284 start of the inlined function are different instructions. Stepping to
9285 the call site shows the call site, and then stepping again shows
9286 the first line of the inlined function, even though no additional
9287 instructions are executed.
9289 This makes source-level debugging much clearer; you can see both the
9290 context of the call and then the effect of the call. Only stepping by
9291 a single instruction using @code{stepi} or @code{nexti} does not do
9292 this; single instruction steps always show the inlined body.
9294 There are some ways that @value{GDBN} does not pretend that inlined
9295 function calls are the same as normal calls:
9299 You cannot set breakpoints on inlined functions. @value{GDBN}
9300 either reports that there is no symbol with that name, or else sets the
9301 breakpoint only on non-inlined copies of the function. This limitation
9302 will be removed in a future version of @value{GDBN}; until then,
9303 set a breakpoint by line number on the first line of the inlined
9307 Setting breakpoints at the call site of an inlined function may not
9308 work, because the call site does not contain any code. @value{GDBN}
9309 may incorrectly move the breakpoint to the next line of the enclosing
9310 function, after the call. This limitation will be removed in a future
9311 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9312 or inside the inlined function instead.
9315 @value{GDBN} cannot locate the return value of inlined calls after
9316 using the @code{finish} command. This is a limitation of compiler-generated
9317 debugging information; after @code{finish}, you can step to the next line
9318 and print a variable where your program stored the return value.
9324 @chapter C Preprocessor Macros
9326 Some languages, such as C and C@t{++}, provide a way to define and invoke
9327 ``preprocessor macros'' which expand into strings of tokens.
9328 @value{GDBN} can evaluate expressions containing macro invocations, show
9329 the result of macro expansion, and show a macro's definition, including
9330 where it was defined.
9332 You may need to compile your program specially to provide @value{GDBN}
9333 with information about preprocessor macros. Most compilers do not
9334 include macros in their debugging information, even when you compile
9335 with the @option{-g} flag. @xref{Compilation}.
9337 A program may define a macro at one point, remove that definition later,
9338 and then provide a different definition after that. Thus, at different
9339 points in the program, a macro may have different definitions, or have
9340 no definition at all. If there is a current stack frame, @value{GDBN}
9341 uses the macros in scope at that frame's source code line. Otherwise,
9342 @value{GDBN} uses the macros in scope at the current listing location;
9345 Whenever @value{GDBN} evaluates an expression, it always expands any
9346 macro invocations present in the expression. @value{GDBN} also provides
9347 the following commands for working with macros explicitly.
9351 @kindex macro expand
9352 @cindex macro expansion, showing the results of preprocessor
9353 @cindex preprocessor macro expansion, showing the results of
9354 @cindex expanding preprocessor macros
9355 @item macro expand @var{expression}
9356 @itemx macro exp @var{expression}
9357 Show the results of expanding all preprocessor macro invocations in
9358 @var{expression}. Since @value{GDBN} simply expands macros, but does
9359 not parse the result, @var{expression} need not be a valid expression;
9360 it can be any string of tokens.
9363 @item macro expand-once @var{expression}
9364 @itemx macro exp1 @var{expression}
9365 @cindex expand macro once
9366 @i{(This command is not yet implemented.)} Show the results of
9367 expanding those preprocessor macro invocations that appear explicitly in
9368 @var{expression}. Macro invocations appearing in that expansion are
9369 left unchanged. This command allows you to see the effect of a
9370 particular macro more clearly, without being confused by further
9371 expansions. Since @value{GDBN} simply expands macros, but does not
9372 parse the result, @var{expression} need not be a valid expression; it
9373 can be any string of tokens.
9376 @cindex macro definition, showing
9377 @cindex definition, showing a macro's
9378 @item info macro @var{macro}
9379 Show the definition of the macro named @var{macro}, and describe the
9380 source location or compiler command-line where that definition was established.
9382 @kindex macro define
9383 @cindex user-defined macros
9384 @cindex defining macros interactively
9385 @cindex macros, user-defined
9386 @item macro define @var{macro} @var{replacement-list}
9387 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9388 Introduce a definition for a preprocessor macro named @var{macro},
9389 invocations of which are replaced by the tokens given in
9390 @var{replacement-list}. The first form of this command defines an
9391 ``object-like'' macro, which takes no arguments; the second form
9392 defines a ``function-like'' macro, which takes the arguments given in
9395 A definition introduced by this command is in scope in every
9396 expression evaluated in @value{GDBN}, until it is removed with the
9397 @code{macro undef} command, described below. The definition overrides
9398 all definitions for @var{macro} present in the program being debugged,
9399 as well as any previous user-supplied definition.
9402 @item macro undef @var{macro}
9403 Remove any user-supplied definition for the macro named @var{macro}.
9404 This command only affects definitions provided with the @code{macro
9405 define} command, described above; it cannot remove definitions present
9406 in the program being debugged.
9410 List all the macros defined using the @code{macro define} command.
9413 @cindex macros, example of debugging with
9414 Here is a transcript showing the above commands in action. First, we
9415 show our source files:
9423 #define ADD(x) (M + x)
9428 printf ("Hello, world!\n");
9430 printf ("We're so creative.\n");
9432 printf ("Goodbye, world!\n");
9439 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9440 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9441 compiler includes information about preprocessor macros in the debugging
9445 $ gcc -gdwarf-2 -g3 sample.c -o sample
9449 Now, we start @value{GDBN} on our sample program:
9453 GNU gdb 2002-05-06-cvs
9454 Copyright 2002 Free Software Foundation, Inc.
9455 GDB is free software, @dots{}
9459 We can expand macros and examine their definitions, even when the
9460 program is not running. @value{GDBN} uses the current listing position
9461 to decide which macro definitions are in scope:
9464 (@value{GDBP}) list main
9467 5 #define ADD(x) (M + x)
9472 10 printf ("Hello, world!\n");
9474 12 printf ("We're so creative.\n");
9475 (@value{GDBP}) info macro ADD
9476 Defined at /home/jimb/gdb/macros/play/sample.c:5
9477 #define ADD(x) (M + x)
9478 (@value{GDBP}) info macro Q
9479 Defined at /home/jimb/gdb/macros/play/sample.h:1
9480 included at /home/jimb/gdb/macros/play/sample.c:2
9482 (@value{GDBP}) macro expand ADD(1)
9483 expands to: (42 + 1)
9484 (@value{GDBP}) macro expand-once ADD(1)
9485 expands to: once (M + 1)
9489 In the example above, note that @code{macro expand-once} expands only
9490 the macro invocation explicit in the original text --- the invocation of
9491 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9492 which was introduced by @code{ADD}.
9494 Once the program is running, @value{GDBN} uses the macro definitions in
9495 force at the source line of the current stack frame:
9498 (@value{GDBP}) break main
9499 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9501 Starting program: /home/jimb/gdb/macros/play/sample
9503 Breakpoint 1, main () at sample.c:10
9504 10 printf ("Hello, world!\n");
9508 At line 10, the definition of the macro @code{N} at line 9 is in force:
9511 (@value{GDBP}) info macro N
9512 Defined at /home/jimb/gdb/macros/play/sample.c:9
9514 (@value{GDBP}) macro expand N Q M
9516 (@value{GDBP}) print N Q M
9521 As we step over directives that remove @code{N}'s definition, and then
9522 give it a new definition, @value{GDBN} finds the definition (or lack
9523 thereof) in force at each point:
9528 12 printf ("We're so creative.\n");
9529 (@value{GDBP}) info macro N
9530 The symbol `N' has no definition as a C/C++ preprocessor macro
9531 at /home/jimb/gdb/macros/play/sample.c:12
9534 14 printf ("Goodbye, world!\n");
9535 (@value{GDBP}) info macro N
9536 Defined at /home/jimb/gdb/macros/play/sample.c:13
9538 (@value{GDBP}) macro expand N Q M
9539 expands to: 1729 < 42
9540 (@value{GDBP}) print N Q M
9545 In addition to source files, macros can be defined on the compilation command
9546 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9547 such a way, @value{GDBN} displays the location of their definition as line zero
9548 of the source file submitted to the compiler.
9551 (@value{GDBP}) info macro __STDC__
9552 Defined at /home/jimb/gdb/macros/play/sample.c:0
9559 @chapter Tracepoints
9560 @c This chapter is based on the documentation written by Michael
9561 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9564 In some applications, it is not feasible for the debugger to interrupt
9565 the program's execution long enough for the developer to learn
9566 anything helpful about its behavior. If the program's correctness
9567 depends on its real-time behavior, delays introduced by a debugger
9568 might cause the program to change its behavior drastically, or perhaps
9569 fail, even when the code itself is correct. It is useful to be able
9570 to observe the program's behavior without interrupting it.
9572 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9573 specify locations in the program, called @dfn{tracepoints}, and
9574 arbitrary expressions to evaluate when those tracepoints are reached.
9575 Later, using the @code{tfind} command, you can examine the values
9576 those expressions had when the program hit the tracepoints. The
9577 expressions may also denote objects in memory---structures or arrays,
9578 for example---whose values @value{GDBN} should record; while visiting
9579 a particular tracepoint, you may inspect those objects as if they were
9580 in memory at that moment. However, because @value{GDBN} records these
9581 values without interacting with you, it can do so quickly and
9582 unobtrusively, hopefully not disturbing the program's behavior.
9584 The tracepoint facility is currently available only for remote
9585 targets. @xref{Targets}. In addition, your remote target must know
9586 how to collect trace data. This functionality is implemented in the
9587 remote stub; however, none of the stubs distributed with @value{GDBN}
9588 support tracepoints as of this writing. The format of the remote
9589 packets used to implement tracepoints are described in @ref{Tracepoint
9592 It is also possible to get trace data from a file, in a manner reminiscent
9593 of corefiles; you specify the filename, and use @code{tfind} to search
9594 through the file. @xref{Trace Files}, for more details.
9596 This chapter describes the tracepoint commands and features.
9600 * Analyze Collected Data::
9601 * Tracepoint Variables::
9605 @node Set Tracepoints
9606 @section Commands to Set Tracepoints
9608 Before running such a @dfn{trace experiment}, an arbitrary number of
9609 tracepoints can be set. A tracepoint is actually a special type of
9610 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9611 standard breakpoint commands. For instance, as with breakpoints,
9612 tracepoint numbers are successive integers starting from one, and many
9613 of the commands associated with tracepoints take the tracepoint number
9614 as their argument, to identify which tracepoint to work on.
9616 For each tracepoint, you can specify, in advance, some arbitrary set
9617 of data that you want the target to collect in the trace buffer when
9618 it hits that tracepoint. The collected data can include registers,
9619 local variables, or global data. Later, you can use @value{GDBN}
9620 commands to examine the values these data had at the time the
9623 Tracepoints do not support every breakpoint feature. Ignore counts on
9624 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9625 commands when they are hit. Tracepoints may not be thread-specific
9628 @cindex fast tracepoints
9629 Some targets may support @dfn{fast tracepoints}, which are inserted in
9630 a different way (such as with a jump instead of a trap), that is
9631 faster but possibly restricted in where they may be installed.
9633 @cindex static tracepoints
9634 @cindex markers, static tracepoints
9635 @cindex probing markers, static tracepoints
9636 Regular and fast tracepoints are dynamic tracing facilities, meaning
9637 that they can be used to insert tracepoints at (almost) any location
9638 in the target. Some targets may also support controlling @dfn{static
9639 tracepoints} from @value{GDBN}. With static tracing, a set of
9640 instrumentation points, also known as @dfn{markers}, are embedded in
9641 the target program, and can be activated or deactivated by name or
9642 address. These are usually placed at locations which facilitate
9643 investigating what the target is actually doing. @value{GDBN}'s
9644 support for static tracing includes being able to list instrumentation
9645 points, and attach them with @value{GDBN} defined high level
9646 tracepoints that expose the whole range of convenience of
9647 @value{GDBN}'s tracepoints support. Namelly, support for collecting
9648 registers values and values of global or local (to the instrumentation
9649 point) variables; tracepoint conditions and trace state variables.
9650 The act of installing a @value{GDBN} static tracepoint on an
9651 instrumentation point, or marker, is referred to as @dfn{probing} a
9652 static tracepoint marker.
9654 @code{gdbserver} supports tracepoints on some target systems.
9655 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9657 This section describes commands to set tracepoints and associated
9658 conditions and actions.
9661 * Create and Delete Tracepoints::
9662 * Enable and Disable Tracepoints::
9663 * Tracepoint Passcounts::
9664 * Tracepoint Conditions::
9665 * Trace State Variables::
9666 * Tracepoint Actions::
9667 * Listing Tracepoints::
9668 * Listing Static Tracepoint Markers::
9669 * Starting and Stopping Trace Experiments::
9670 * Tracepoint Restrictions::
9673 @node Create and Delete Tracepoints
9674 @subsection Create and Delete Tracepoints
9677 @cindex set tracepoint
9679 @item trace @var{location}
9680 The @code{trace} command is very similar to the @code{break} command.
9681 Its argument @var{location} can be a source line, a function name, or
9682 an address in the target program. @xref{Specify Location}. The
9683 @code{trace} command defines a tracepoint, which is a point in the
9684 target program where the debugger will briefly stop, collect some
9685 data, and then allow the program to continue. Setting a tracepoint or
9686 changing its actions doesn't take effect until the next @code{tstart}
9687 command, and once a trace experiment is running, further changes will
9688 not have any effect until the next trace experiment starts.
9690 Here are some examples of using the @code{trace} command:
9693 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9695 (@value{GDBP}) @b{trace +2} // 2 lines forward
9697 (@value{GDBP}) @b{trace my_function} // first source line of function
9699 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9701 (@value{GDBP}) @b{trace *0x2117c4} // an address
9705 You can abbreviate @code{trace} as @code{tr}.
9707 @item trace @var{location} if @var{cond}
9708 Set a tracepoint with condition @var{cond}; evaluate the expression
9709 @var{cond} each time the tracepoint is reached, and collect data only
9710 if the value is nonzero---that is, if @var{cond} evaluates as true.
9711 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9712 information on tracepoint conditions.
9714 @item ftrace @var{location} [ if @var{cond} ]
9715 @cindex set fast tracepoint
9716 @cindex fast tracepoints, setting
9718 The @code{ftrace} command sets a fast tracepoint. For targets that
9719 support them, fast tracepoints will use a more efficient but possibly
9720 less general technique to trigger data collection, such as a jump
9721 instruction instead of a trap, or some sort of hardware support. It
9722 may not be possible to create a fast tracepoint at the desired
9723 location, in which case the command will exit with an explanatory
9726 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9729 @item strace @var{location} [ if @var{cond} ]
9730 @cindex set static tracepoint
9731 @cindex static tracepoints, setting
9732 @cindex probe static tracepoint marker
9734 The @code{strace} command sets a static tracepoint. For targets that
9735 support it, setting a static tracepoint probes a static
9736 instrumentation point, or marker, found at @var{location}. It may not
9737 be possible to set a static tracepoint at the desired location, in
9738 which case the command will exit with an explanatory message.
9740 @value{GDBN} handles arguments to @code{strace} exactly as for
9741 @code{trace}, with the addition that the user can also specify
9742 @code{-m @var{marker}} as @var{location}. This probes the marker
9743 identified by the @var{marker} string identifier. This identifier
9744 depends on the static tracepoint backend library your program is
9745 using. You can find all the marker identifiers in the @samp{ID} field
9746 of the @code{info static-tracepoint-markers} command output.
9747 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
9748 Markers}. For example, in the following small program using the UST
9754 trace_mark(ust, bar33, "str %s", "FOOBAZ");
9759 the marker id is composed of joining the first two arguments to the
9760 @code{trace_mark} call with a slash, which translates to:
9763 (@value{GDBP}) info static-tracepoint-markers
9764 Cnt Enb ID Address What
9765 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
9771 so you may probe the marker above with:
9774 (@value{GDBP}) strace -m ust/bar33
9777 Static tracepoints accept an extra collect action --- @code{collect
9778 $_sdata}. This collects arbitrary user data passed in the probe point
9779 call to the tracing library. In the UST example above, you'll see
9780 that the third argument to @code{trace_mark} is a printf-like format
9781 string. The user data is then the result of running that formating
9782 string against the following arguments. Note that @code{info
9783 static-tracepoint-markers} command output lists that format string in
9784 the @samp{Data:} field.
9786 You can inspect this data when analyzing the trace buffer, by printing
9787 the $_sdata variable like any other variable available to
9788 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
9791 @cindex last tracepoint number
9792 @cindex recent tracepoint number
9793 @cindex tracepoint number
9794 The convenience variable @code{$tpnum} records the tracepoint number
9795 of the most recently set tracepoint.
9797 @kindex delete tracepoint
9798 @cindex tracepoint deletion
9799 @item delete tracepoint @r{[}@var{num}@r{]}
9800 Permanently delete one or more tracepoints. With no argument, the
9801 default is to delete all tracepoints. Note that the regular
9802 @code{delete} command can remove tracepoints also.
9807 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9809 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9813 You can abbreviate this command as @code{del tr}.
9816 @node Enable and Disable Tracepoints
9817 @subsection Enable and Disable Tracepoints
9819 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9822 @kindex disable tracepoint
9823 @item disable tracepoint @r{[}@var{num}@r{]}
9824 Disable tracepoint @var{num}, or all tracepoints if no argument
9825 @var{num} is given. A disabled tracepoint will have no effect during
9826 the next trace experiment, but it is not forgotten. You can re-enable
9827 a disabled tracepoint using the @code{enable tracepoint} command.
9829 @kindex enable tracepoint
9830 @item enable tracepoint @r{[}@var{num}@r{]}
9831 Enable tracepoint @var{num}, or all tracepoints. The enabled
9832 tracepoints will become effective the next time a trace experiment is
9836 @node Tracepoint Passcounts
9837 @subsection Tracepoint Passcounts
9841 @cindex tracepoint pass count
9842 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9843 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9844 automatically stop a trace experiment. If a tracepoint's passcount is
9845 @var{n}, then the trace experiment will be automatically stopped on
9846 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9847 @var{num} is not specified, the @code{passcount} command sets the
9848 passcount of the most recently defined tracepoint. If no passcount is
9849 given, the trace experiment will run until stopped explicitly by the
9855 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9856 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9858 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9859 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9860 (@value{GDBP}) @b{trace foo}
9861 (@value{GDBP}) @b{pass 3}
9862 (@value{GDBP}) @b{trace bar}
9863 (@value{GDBP}) @b{pass 2}
9864 (@value{GDBP}) @b{trace baz}
9865 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9866 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9867 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9868 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9872 @node Tracepoint Conditions
9873 @subsection Tracepoint Conditions
9874 @cindex conditional tracepoints
9875 @cindex tracepoint conditions
9877 The simplest sort of tracepoint collects data every time your program
9878 reaches a specified place. You can also specify a @dfn{condition} for
9879 a tracepoint. A condition is just a Boolean expression in your
9880 programming language (@pxref{Expressions, ,Expressions}). A
9881 tracepoint with a condition evaluates the expression each time your
9882 program reaches it, and data collection happens only if the condition
9885 Tracepoint conditions can be specified when a tracepoint is set, by
9886 using @samp{if} in the arguments to the @code{trace} command.
9887 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9888 also be set or changed at any time with the @code{condition} command,
9889 just as with breakpoints.
9891 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9892 the conditional expression itself. Instead, @value{GDBN} encodes the
9893 expression into an agent expression (@pxref{Agent Expressions}
9894 suitable for execution on the target, independently of @value{GDBN}.
9895 Global variables become raw memory locations, locals become stack
9896 accesses, and so forth.
9898 For instance, suppose you have a function that is usually called
9899 frequently, but should not be called after an error has occurred. You
9900 could use the following tracepoint command to collect data about calls
9901 of that function that happen while the error code is propagating
9902 through the program; an unconditional tracepoint could end up
9903 collecting thousands of useless trace frames that you would have to
9907 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9910 @node Trace State Variables
9911 @subsection Trace State Variables
9912 @cindex trace state variables
9914 A @dfn{trace state variable} is a special type of variable that is
9915 created and managed by target-side code. The syntax is the same as
9916 that for GDB's convenience variables (a string prefixed with ``$''),
9917 but they are stored on the target. They must be created explicitly,
9918 using a @code{tvariable} command. They are always 64-bit signed
9921 Trace state variables are remembered by @value{GDBN}, and downloaded
9922 to the target along with tracepoint information when the trace
9923 experiment starts. There are no intrinsic limits on the number of
9924 trace state variables, beyond memory limitations of the target.
9926 @cindex convenience variables, and trace state variables
9927 Although trace state variables are managed by the target, you can use
9928 them in print commands and expressions as if they were convenience
9929 variables; @value{GDBN} will get the current value from the target
9930 while the trace experiment is running. Trace state variables share
9931 the same namespace as other ``$'' variables, which means that you
9932 cannot have trace state variables with names like @code{$23} or
9933 @code{$pc}, nor can you have a trace state variable and a convenience
9934 variable with the same name.
9938 @item tvariable $@var{name} [ = @var{expression} ]
9940 The @code{tvariable} command creates a new trace state variable named
9941 @code{$@var{name}}, and optionally gives it an initial value of
9942 @var{expression}. @var{expression} is evaluated when this command is
9943 entered; the result will be converted to an integer if possible,
9944 otherwise @value{GDBN} will report an error. A subsequent
9945 @code{tvariable} command specifying the same name does not create a
9946 variable, but instead assigns the supplied initial value to the
9947 existing variable of that name, overwriting any previous initial
9948 value. The default initial value is 0.
9950 @item info tvariables
9951 @kindex info tvariables
9952 List all the trace state variables along with their initial values.
9953 Their current values may also be displayed, if the trace experiment is
9956 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
9957 @kindex delete tvariable
9958 Delete the given trace state variables, or all of them if no arguments
9963 @node Tracepoint Actions
9964 @subsection Tracepoint Action Lists
9968 @cindex tracepoint actions
9969 @item actions @r{[}@var{num}@r{]}
9970 This command will prompt for a list of actions to be taken when the
9971 tracepoint is hit. If the tracepoint number @var{num} is not
9972 specified, this command sets the actions for the one that was most
9973 recently defined (so that you can define a tracepoint and then say
9974 @code{actions} without bothering about its number). You specify the
9975 actions themselves on the following lines, one action at a time, and
9976 terminate the actions list with a line containing just @code{end}. So
9977 far, the only defined actions are @code{collect}, @code{teval}, and
9978 @code{while-stepping}.
9980 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
9981 Commands, ,Breakpoint Command Lists}), except that only the defined
9982 actions are allowed; any other @value{GDBN} command is rejected.
9984 @cindex remove actions from a tracepoint
9985 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9986 and follow it immediately with @samp{end}.
9989 (@value{GDBP}) @b{collect @var{data}} // collect some data
9991 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9993 (@value{GDBP}) @b{end} // signals the end of actions.
9996 In the following example, the action list begins with @code{collect}
9997 commands indicating the things to be collected when the tracepoint is
9998 hit. Then, in order to single-step and collect additional data
9999 following the tracepoint, a @code{while-stepping} command is used,
10000 followed by the list of things to be collected after each step in a
10001 sequence of single steps. The @code{while-stepping} command is
10002 terminated by its own separate @code{end} command. Lastly, the action
10003 list is terminated by an @code{end} command.
10006 (@value{GDBP}) @b{trace foo}
10007 (@value{GDBP}) @b{actions}
10008 Enter actions for tracepoint 1, one per line:
10011 > while-stepping 12
10012 > collect $pc, arr[i]
10017 @kindex collect @r{(tracepoints)}
10018 @item collect @var{expr1}, @var{expr2}, @dots{}
10019 Collect values of the given expressions when the tracepoint is hit.
10020 This command accepts a comma-separated list of any valid expressions.
10021 In addition to global, static, or local variables, the following
10022 special arguments are supported:
10026 Collect all registers.
10029 Collect all function arguments.
10032 Collect all local variables.
10035 @vindex $_sdata@r{, collect}
10036 Collect static tracepoint marker specific data. Only available for
10037 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10038 Lists}. On the UST static tracepoints library backend, an
10039 instrumentation point resembles a @code{printf} function call. The
10040 tracing library is able to collect user specified data formatted to a
10041 character string using the format provided by the programmer that
10042 instrumented the program. Other backends have similar mechanisms.
10043 Here's an example of a UST marker call:
10046 const char master_name[] = "$your_name";
10047 trace_mark(channel1, marker1, "hello %s", master_name)
10050 In this case, collecting @code{$_sdata} collects the string
10051 @samp{hello $yourname}. When analyzing the trace buffer, you can
10052 inspect @samp{$_sdata} like any other variable available to
10056 You can give several consecutive @code{collect} commands, each one
10057 with a single argument, or one @code{collect} command with several
10058 arguments separated by commas; the effect is the same.
10060 The command @code{info scope} (@pxref{Symbols, info scope}) is
10061 particularly useful for figuring out what data to collect.
10063 @kindex teval @r{(tracepoints)}
10064 @item teval @var{expr1}, @var{expr2}, @dots{}
10065 Evaluate the given expressions when the tracepoint is hit. This
10066 command accepts a comma-separated list of expressions. The results
10067 are discarded, so this is mainly useful for assigning values to trace
10068 state variables (@pxref{Trace State Variables}) without adding those
10069 values to the trace buffer, as would be the case if the @code{collect}
10072 @kindex while-stepping @r{(tracepoints)}
10073 @item while-stepping @var{n}
10074 Perform @var{n} single-step instruction traces after the tracepoint,
10075 collecting new data after each step. The @code{while-stepping}
10076 command is followed by the list of what to collect while stepping
10077 (followed by its own @code{end} command):
10080 > while-stepping 12
10081 > collect $regs, myglobal
10087 Note that @code{$pc} is not automatically collected by
10088 @code{while-stepping}; you need to explicitly collect that register if
10089 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10092 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10093 @kindex set default-collect
10094 @cindex default collection action
10095 This variable is a list of expressions to collect at each tracepoint
10096 hit. It is effectively an additional @code{collect} action prepended
10097 to every tracepoint action list. The expressions are parsed
10098 individually for each tracepoint, so for instance a variable named
10099 @code{xyz} may be interpreted as a global for one tracepoint, and a
10100 local for another, as appropriate to the tracepoint's location.
10102 @item show default-collect
10103 @kindex show default-collect
10104 Show the list of expressions that are collected by default at each
10109 @node Listing Tracepoints
10110 @subsection Listing Tracepoints
10113 @kindex info tracepoints
10115 @cindex information about tracepoints
10116 @item info tracepoints @r{[}@var{num}@r{]}
10117 Display information about the tracepoint @var{num}. If you don't
10118 specify a tracepoint number, displays information about all the
10119 tracepoints defined so far. The format is similar to that used for
10120 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10121 command, simply restricting itself to tracepoints.
10123 A tracepoint's listing may include additional information specific to
10128 its passcount as given by the @code{passcount @var{n}} command
10132 (@value{GDBP}) @b{info trace}
10133 Num Type Disp Enb Address What
10134 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10136 collect globfoo, $regs
10145 This command can be abbreviated @code{info tp}.
10148 @node Listing Static Tracepoint Markers
10149 @subsection Listing Static Tracepoint Markers
10152 @kindex info static-tracepoint-markers
10153 @cindex information about static tracepoint markers
10154 @item info static-tracepoint-markers
10155 Display information about all static tracepoint markers defined in the
10158 For each marker, the following columns are printed:
10162 An incrementing counter, output to help readability. This is not a
10165 The marker ID, as reported by the target.
10166 @item Enabled or Disabled
10167 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10168 that are not enabled.
10170 Where the marker is in your program, as a memory address.
10172 Where the marker is in the source for your program, as a file and line
10173 number. If the debug information included in the program does not
10174 allow @value{GDBN} to locate the source of the marker, this column
10175 will be left blank.
10179 In addition, the following information may be printed for each marker:
10183 User data passed to the tracing library by the marker call. In the
10184 UST backend, this is the format string passed as argument to the
10186 @item Static tracepoints probing the marker
10187 The list of static tracepoints attached to the marker.
10191 (@value{GDBP}) info static-tracepoint-markers
10192 Cnt ID Enb Address What
10193 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10194 Data: number1 %d number2 %d
10195 Probed by static tracepoints: #2
10196 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10202 @node Starting and Stopping Trace Experiments
10203 @subsection Starting and Stopping Trace Experiments
10207 @cindex start a new trace experiment
10208 @cindex collected data discarded
10210 This command takes no arguments. It starts the trace experiment, and
10211 begins collecting data. This has the side effect of discarding all
10212 the data collected in the trace buffer during the previous trace
10216 @cindex stop a running trace experiment
10218 This command takes no arguments. It ends the trace experiment, and
10219 stops collecting data.
10221 @strong{Note}: a trace experiment and data collection may stop
10222 automatically if any tracepoint's passcount is reached
10223 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10226 @cindex status of trace data collection
10227 @cindex trace experiment, status of
10229 This command displays the status of the current trace data
10233 Here is an example of the commands we described so far:
10236 (@value{GDBP}) @b{trace gdb_c_test}
10237 (@value{GDBP}) @b{actions}
10238 Enter actions for tracepoint #1, one per line.
10239 > collect $regs,$locals,$args
10240 > while-stepping 11
10244 (@value{GDBP}) @b{tstart}
10245 [time passes @dots{}]
10246 (@value{GDBP}) @b{tstop}
10249 @cindex disconnected tracing
10250 You can choose to continue running the trace experiment even if
10251 @value{GDBN} disconnects from the target, voluntarily or
10252 involuntarily. For commands such as @code{detach}, the debugger will
10253 ask what you want to do with the trace. But for unexpected
10254 terminations (@value{GDBN} crash, network outage), it would be
10255 unfortunate to lose hard-won trace data, so the variable
10256 @code{disconnected-tracing} lets you decide whether the trace should
10257 continue running without @value{GDBN}.
10260 @item set disconnected-tracing on
10261 @itemx set disconnected-tracing off
10262 @kindex set disconnected-tracing
10263 Choose whether a tracing run should continue to run if @value{GDBN}
10264 has disconnected from the target. Note that @code{detach} or
10265 @code{quit} will ask you directly what to do about a running trace no
10266 matter what this variable's setting, so the variable is mainly useful
10267 for handling unexpected situations, such as loss of the network.
10269 @item show disconnected-tracing
10270 @kindex show disconnected-tracing
10271 Show the current choice for disconnected tracing.
10275 When you reconnect to the target, the trace experiment may or may not
10276 still be running; it might have filled the trace buffer in the
10277 meantime, or stopped for one of the other reasons. If it is running,
10278 it will continue after reconnection.
10280 Upon reconnection, the target will upload information about the
10281 tracepoints in effect. @value{GDBN} will then compare that
10282 information to the set of tracepoints currently defined, and attempt
10283 to match them up, allowing for the possibility that the numbers may
10284 have changed due to creation and deletion in the meantime. If one of
10285 the target's tracepoints does not match any in @value{GDBN}, the
10286 debugger will create a new tracepoint, so that you have a number with
10287 which to specify that tracepoint. This matching-up process is
10288 necessarily heuristic, and it may result in useless tracepoints being
10289 created; you may simply delete them if they are of no use.
10291 @cindex circular trace buffer
10292 If your target agent supports a @dfn{circular trace buffer}, then you
10293 can run a trace experiment indefinitely without filling the trace
10294 buffer; when space runs out, the agent deletes already-collected trace
10295 frames, oldest first, until there is enough room to continue
10296 collecting. This is especially useful if your tracepoints are being
10297 hit too often, and your trace gets terminated prematurely because the
10298 buffer is full. To ask for a circular trace buffer, simply set
10299 @samp{circular_trace_buffer} to on. You can set this at any time,
10300 including during tracing; if the agent can do it, it will change
10301 buffer handling on the fly, otherwise it will not take effect until
10305 @item set circular-trace-buffer on
10306 @itemx set circular-trace-buffer off
10307 @kindex set circular-trace-buffer
10308 Choose whether a tracing run should use a linear or circular buffer
10309 for trace data. A linear buffer will not lose any trace data, but may
10310 fill up prematurely, while a circular buffer will discard old trace
10311 data, but it will have always room for the latest tracepoint hits.
10313 @item show circular-trace-buffer
10314 @kindex show circular-trace-buffer
10315 Show the current choice for the trace buffer. Note that this may not
10316 match the agent's current buffer handling, nor is it guaranteed to
10317 match the setting that might have been in effect during a past run,
10318 for instance if you are looking at frames from a trace file.
10322 @node Tracepoint Restrictions
10323 @subsection Tracepoint Restrictions
10325 @cindex tracepoint restrictions
10326 There are a number of restrictions on the use of tracepoints. As
10327 described above, tracepoint data gathering occurs on the target
10328 without interaction from @value{GDBN}. Thus the full capabilities of
10329 the debugger are not available during data gathering, and then at data
10330 examination time, you will be limited by only having what was
10331 collected. The following items describe some common problems, but it
10332 is not exhaustive, and you may run into additional difficulties not
10338 Tracepoint expressions are intended to gather objects (lvalues). Thus
10339 the full flexibility of GDB's expression evaluator is not available.
10340 You cannot call functions, cast objects to aggregate types, access
10341 convenience variables or modify values (except by assignment to trace
10342 state variables). Some language features may implicitly call
10343 functions (for instance Objective-C fields with accessors), and therefore
10344 cannot be collected either.
10347 Collection of local variables, either individually or in bulk with
10348 @code{$locals} or @code{$args}, during @code{while-stepping} may
10349 behave erratically. The stepping action may enter a new scope (for
10350 instance by stepping into a function), or the location of the variable
10351 may change (for instance it is loaded into a register). The
10352 tracepoint data recorded uses the location information for the
10353 variables that is correct for the tracepoint location. When the
10354 tracepoint is created, it is not possible, in general, to determine
10355 where the steps of a @code{while-stepping} sequence will advance the
10356 program---particularly if a conditional branch is stepped.
10359 Collection of an incompletely-initialized or partially-destroyed object
10360 may result in something that @value{GDBN} cannot display, or displays
10361 in a misleading way.
10364 When @value{GDBN} displays a pointer to character it automatically
10365 dereferences the pointer to also display characters of the string
10366 being pointed to. However, collecting the pointer during tracing does
10367 not automatically collect the string. You need to explicitly
10368 dereference the pointer and provide size information if you want to
10369 collect not only the pointer, but the memory pointed to. For example,
10370 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10374 It is not possible to collect a complete stack backtrace at a
10375 tracepoint. Instead, you may collect the registers and a few hundred
10376 bytes from the stack pointer with something like @code{*$esp@@300}
10377 (adjust to use the name of the actual stack pointer register on your
10378 target architecture, and the amount of stack you wish to capture).
10379 Then the @code{backtrace} command will show a partial backtrace when
10380 using a trace frame. The number of stack frames that can be examined
10381 depends on the sizes of the frames in the collected stack. Note that
10382 if you ask for a block so large that it goes past the bottom of the
10383 stack, the target agent may report an error trying to read from an
10387 If you do not collect registers at a tracepoint, @value{GDBN} can
10388 infer that the value of @code{$pc} must be the same as the address of
10389 the tracepoint and use that when you are looking at a trace frame
10390 for that tracepoint. However, this cannot work if the tracepoint has
10391 multiple locations (for instance if it was set in a function that was
10392 inlined), or if it has a @code{while-stepping} loop. In those cases
10393 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10398 @node Analyze Collected Data
10399 @section Using the Collected Data
10401 After the tracepoint experiment ends, you use @value{GDBN} commands
10402 for examining the trace data. The basic idea is that each tracepoint
10403 collects a trace @dfn{snapshot} every time it is hit and another
10404 snapshot every time it single-steps. All these snapshots are
10405 consecutively numbered from zero and go into a buffer, and you can
10406 examine them later. The way you examine them is to @dfn{focus} on a
10407 specific trace snapshot. When the remote stub is focused on a trace
10408 snapshot, it will respond to all @value{GDBN} requests for memory and
10409 registers by reading from the buffer which belongs to that snapshot,
10410 rather than from @emph{real} memory or registers of the program being
10411 debugged. This means that @strong{all} @value{GDBN} commands
10412 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10413 behave as if we were currently debugging the program state as it was
10414 when the tracepoint occurred. Any requests for data that are not in
10415 the buffer will fail.
10418 * tfind:: How to select a trace snapshot
10419 * tdump:: How to display all data for a snapshot
10420 * save tracepoints:: How to save tracepoints for a future run
10424 @subsection @code{tfind @var{n}}
10427 @cindex select trace snapshot
10428 @cindex find trace snapshot
10429 The basic command for selecting a trace snapshot from the buffer is
10430 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10431 counting from zero. If no argument @var{n} is given, the next
10432 snapshot is selected.
10434 Here are the various forms of using the @code{tfind} command.
10438 Find the first snapshot in the buffer. This is a synonym for
10439 @code{tfind 0} (since 0 is the number of the first snapshot).
10442 Stop debugging trace snapshots, resume @emph{live} debugging.
10445 Same as @samp{tfind none}.
10448 No argument means find the next trace snapshot.
10451 Find the previous trace snapshot before the current one. This permits
10452 retracing earlier steps.
10454 @item tfind tracepoint @var{num}
10455 Find the next snapshot associated with tracepoint @var{num}. Search
10456 proceeds forward from the last examined trace snapshot. If no
10457 argument @var{num} is given, it means find the next snapshot collected
10458 for the same tracepoint as the current snapshot.
10460 @item tfind pc @var{addr}
10461 Find the next snapshot associated with the value @var{addr} of the
10462 program counter. Search proceeds forward from the last examined trace
10463 snapshot. If no argument @var{addr} is given, it means find the next
10464 snapshot with the same value of PC as the current snapshot.
10466 @item tfind outside @var{addr1}, @var{addr2}
10467 Find the next snapshot whose PC is outside the given range of
10468 addresses (exclusive).
10470 @item tfind range @var{addr1}, @var{addr2}
10471 Find the next snapshot whose PC is between @var{addr1} and
10472 @var{addr2} (inclusive).
10474 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10475 Find the next snapshot associated with the source line @var{n}. If
10476 the optional argument @var{file} is given, refer to line @var{n} in
10477 that source file. Search proceeds forward from the last examined
10478 trace snapshot. If no argument @var{n} is given, it means find the
10479 next line other than the one currently being examined; thus saying
10480 @code{tfind line} repeatedly can appear to have the same effect as
10481 stepping from line to line in a @emph{live} debugging session.
10484 The default arguments for the @code{tfind} commands are specifically
10485 designed to make it easy to scan through the trace buffer. For
10486 instance, @code{tfind} with no argument selects the next trace
10487 snapshot, and @code{tfind -} with no argument selects the previous
10488 trace snapshot. So, by giving one @code{tfind} command, and then
10489 simply hitting @key{RET} repeatedly you can examine all the trace
10490 snapshots in order. Or, by saying @code{tfind -} and then hitting
10491 @key{RET} repeatedly you can examine the snapshots in reverse order.
10492 The @code{tfind line} command with no argument selects the snapshot
10493 for the next source line executed. The @code{tfind pc} command with
10494 no argument selects the next snapshot with the same program counter
10495 (PC) as the current frame. The @code{tfind tracepoint} command with
10496 no argument selects the next trace snapshot collected by the same
10497 tracepoint as the current one.
10499 In addition to letting you scan through the trace buffer manually,
10500 these commands make it easy to construct @value{GDBN} scripts that
10501 scan through the trace buffer and print out whatever collected data
10502 you are interested in. Thus, if we want to examine the PC, FP, and SP
10503 registers from each trace frame in the buffer, we can say this:
10506 (@value{GDBP}) @b{tfind start}
10507 (@value{GDBP}) @b{while ($trace_frame != -1)}
10508 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10509 $trace_frame, $pc, $sp, $fp
10513 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10514 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10515 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10516 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10517 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10518 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10519 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10520 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10521 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10522 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10523 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10526 Or, if we want to examine the variable @code{X} at each source line in
10530 (@value{GDBP}) @b{tfind start}
10531 (@value{GDBP}) @b{while ($trace_frame != -1)}
10532 > printf "Frame %d, X == %d\n", $trace_frame, X
10542 @subsection @code{tdump}
10544 @cindex dump all data collected at tracepoint
10545 @cindex tracepoint data, display
10547 This command takes no arguments. It prints all the data collected at
10548 the current trace snapshot.
10551 (@value{GDBP}) @b{trace 444}
10552 (@value{GDBP}) @b{actions}
10553 Enter actions for tracepoint #2, one per line:
10554 > collect $regs, $locals, $args, gdb_long_test
10557 (@value{GDBP}) @b{tstart}
10559 (@value{GDBP}) @b{tfind line 444}
10560 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10562 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10564 (@value{GDBP}) @b{tdump}
10565 Data collected at tracepoint 2, trace frame 1:
10566 d0 0xc4aa0085 -995491707
10570 d4 0x71aea3d 119204413
10573 d7 0x380035 3670069
10574 a0 0x19e24a 1696330
10575 a1 0x3000668 50333288
10577 a3 0x322000 3284992
10578 a4 0x3000698 50333336
10579 a5 0x1ad3cc 1758156
10580 fp 0x30bf3c 0x30bf3c
10581 sp 0x30bf34 0x30bf34
10583 pc 0x20b2c8 0x20b2c8
10587 p = 0x20e5b4 "gdb-test"
10594 gdb_long_test = 17 '\021'
10599 @code{tdump} works by scanning the tracepoint's current collection
10600 actions and printing the value of each expression listed. So
10601 @code{tdump} can fail, if after a run, you change the tracepoint's
10602 actions to mention variables that were not collected during the run.
10604 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10605 uses the collected value of @code{$pc} to distinguish between trace
10606 frames that were collected at the tracepoint hit, and frames that were
10607 collected while stepping. This allows it to correctly choose whether
10608 to display the basic list of collections, or the collections from the
10609 body of the while-stepping loop. However, if @code{$pc} was not collected,
10610 then @code{tdump} will always attempt to dump using the basic collection
10611 list, and may fail if a while-stepping frame does not include all the
10612 same data that is collected at the tracepoint hit.
10613 @c This is getting pretty arcane, example would be good.
10615 @node save tracepoints
10616 @subsection @code{save tracepoints @var{filename}}
10617 @kindex save tracepoints
10618 @kindex save-tracepoints
10619 @cindex save tracepoints for future sessions
10621 This command saves all current tracepoint definitions together with
10622 their actions and passcounts, into a file @file{@var{filename}}
10623 suitable for use in a later debugging session. To read the saved
10624 tracepoint definitions, use the @code{source} command (@pxref{Command
10625 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10626 alias for @w{@code{save tracepoints}}
10628 @node Tracepoint Variables
10629 @section Convenience Variables for Tracepoints
10630 @cindex tracepoint variables
10631 @cindex convenience variables for tracepoints
10634 @vindex $trace_frame
10635 @item (int) $trace_frame
10636 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10637 snapshot is selected.
10639 @vindex $tracepoint
10640 @item (int) $tracepoint
10641 The tracepoint for the current trace snapshot.
10643 @vindex $trace_line
10644 @item (int) $trace_line
10645 The line number for the current trace snapshot.
10647 @vindex $trace_file
10648 @item (char []) $trace_file
10649 The source file for the current trace snapshot.
10651 @vindex $trace_func
10652 @item (char []) $trace_func
10653 The name of the function containing @code{$tracepoint}.
10656 Note: @code{$trace_file} is not suitable for use in @code{printf},
10657 use @code{output} instead.
10659 Here's a simple example of using these convenience variables for
10660 stepping through all the trace snapshots and printing some of their
10661 data. Note that these are not the same as trace state variables,
10662 which are managed by the target.
10665 (@value{GDBP}) @b{tfind start}
10667 (@value{GDBP}) @b{while $trace_frame != -1}
10668 > output $trace_file
10669 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10675 @section Using Trace Files
10676 @cindex trace files
10678 In some situations, the target running a trace experiment may no
10679 longer be available; perhaps it crashed, or the hardware was needed
10680 for a different activity. To handle these cases, you can arrange to
10681 dump the trace data into a file, and later use that file as a source
10682 of trace data, via the @code{target tfile} command.
10687 @item tsave [ -r ] @var{filename}
10688 Save the trace data to @var{filename}. By default, this command
10689 assumes that @var{filename} refers to the host filesystem, so if
10690 necessary @value{GDBN} will copy raw trace data up from the target and
10691 then save it. If the target supports it, you can also supply the
10692 optional argument @code{-r} (``remote'') to direct the target to save
10693 the data directly into @var{filename} in its own filesystem, which may be
10694 more efficient if the trace buffer is very large. (Note, however, that
10695 @code{target tfile} can only read from files accessible to the host.)
10697 @kindex target tfile
10699 @item target tfile @var{filename}
10700 Use the file named @var{filename} as a source of trace data. Commands
10701 that examine data work as they do with a live target, but it is not
10702 possible to run any new trace experiments. @code{tstatus} will report
10703 the state of the trace run at the moment the data was saved, as well
10704 as the current trace frame you are examining. @var{filename} must be
10705 on a filesystem accessible to the host.
10710 @chapter Debugging Programs That Use Overlays
10713 If your program is too large to fit completely in your target system's
10714 memory, you can sometimes use @dfn{overlays} to work around this
10715 problem. @value{GDBN} provides some support for debugging programs that
10719 * How Overlays Work:: A general explanation of overlays.
10720 * Overlay Commands:: Managing overlays in @value{GDBN}.
10721 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10722 mapped by asking the inferior.
10723 * Overlay Sample Program:: A sample program using overlays.
10726 @node How Overlays Work
10727 @section How Overlays Work
10728 @cindex mapped overlays
10729 @cindex unmapped overlays
10730 @cindex load address, overlay's
10731 @cindex mapped address
10732 @cindex overlay area
10734 Suppose you have a computer whose instruction address space is only 64
10735 kilobytes long, but which has much more memory which can be accessed by
10736 other means: special instructions, segment registers, or memory
10737 management hardware, for example. Suppose further that you want to
10738 adapt a program which is larger than 64 kilobytes to run on this system.
10740 One solution is to identify modules of your program which are relatively
10741 independent, and need not call each other directly; call these modules
10742 @dfn{overlays}. Separate the overlays from the main program, and place
10743 their machine code in the larger memory. Place your main program in
10744 instruction memory, but leave at least enough space there to hold the
10745 largest overlay as well.
10747 Now, to call a function located in an overlay, you must first copy that
10748 overlay's machine code from the large memory into the space set aside
10749 for it in the instruction memory, and then jump to its entry point
10752 @c NB: In the below the mapped area's size is greater or equal to the
10753 @c size of all overlays. This is intentional to remind the developer
10754 @c that overlays don't necessarily need to be the same size.
10758 Data Instruction Larger
10759 Address Space Address Space Address Space
10760 +-----------+ +-----------+ +-----------+
10762 +-----------+ +-----------+ +-----------+<-- overlay 1
10763 | program | | main | .----| overlay 1 | load address
10764 | variables | | program | | +-----------+
10765 | and heap | | | | | |
10766 +-----------+ | | | +-----------+<-- overlay 2
10767 | | +-----------+ | | | load address
10768 +-----------+ | | | .-| overlay 2 |
10770 mapped --->+-----------+ | | +-----------+
10771 address | | | | | |
10772 | overlay | <-' | | |
10773 | area | <---' +-----------+<-- overlay 3
10774 | | <---. | | load address
10775 +-----------+ `--| overlay 3 |
10782 @anchor{A code overlay}A code overlay
10786 The diagram (@pxref{A code overlay}) shows a system with separate data
10787 and instruction address spaces. To map an overlay, the program copies
10788 its code from the larger address space to the instruction address space.
10789 Since the overlays shown here all use the same mapped address, only one
10790 may be mapped at a time. For a system with a single address space for
10791 data and instructions, the diagram would be similar, except that the
10792 program variables and heap would share an address space with the main
10793 program and the overlay area.
10795 An overlay loaded into instruction memory and ready for use is called a
10796 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10797 instruction memory. An overlay not present (or only partially present)
10798 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10799 is its address in the larger memory. The mapped address is also called
10800 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10801 called the @dfn{load memory address}, or @dfn{LMA}.
10803 Unfortunately, overlays are not a completely transparent way to adapt a
10804 program to limited instruction memory. They introduce a new set of
10805 global constraints you must keep in mind as you design your program:
10810 Before calling or returning to a function in an overlay, your program
10811 must make sure that overlay is actually mapped. Otherwise, the call or
10812 return will transfer control to the right address, but in the wrong
10813 overlay, and your program will probably crash.
10816 If the process of mapping an overlay is expensive on your system, you
10817 will need to choose your overlays carefully to minimize their effect on
10818 your program's performance.
10821 The executable file you load onto your system must contain each
10822 overlay's instructions, appearing at the overlay's load address, not its
10823 mapped address. However, each overlay's instructions must be relocated
10824 and its symbols defined as if the overlay were at its mapped address.
10825 You can use GNU linker scripts to specify different load and relocation
10826 addresses for pieces of your program; see @ref{Overlay Description,,,
10827 ld.info, Using ld: the GNU linker}.
10830 The procedure for loading executable files onto your system must be able
10831 to load their contents into the larger address space as well as the
10832 instruction and data spaces.
10836 The overlay system described above is rather simple, and could be
10837 improved in many ways:
10842 If your system has suitable bank switch registers or memory management
10843 hardware, you could use those facilities to make an overlay's load area
10844 contents simply appear at their mapped address in instruction space.
10845 This would probably be faster than copying the overlay to its mapped
10846 area in the usual way.
10849 If your overlays are small enough, you could set aside more than one
10850 overlay area, and have more than one overlay mapped at a time.
10853 You can use overlays to manage data, as well as instructions. In
10854 general, data overlays are even less transparent to your design than
10855 code overlays: whereas code overlays only require care when you call or
10856 return to functions, data overlays require care every time you access
10857 the data. Also, if you change the contents of a data overlay, you
10858 must copy its contents back out to its load address before you can copy a
10859 different data overlay into the same mapped area.
10864 @node Overlay Commands
10865 @section Overlay Commands
10867 To use @value{GDBN}'s overlay support, each overlay in your program must
10868 correspond to a separate section of the executable file. The section's
10869 virtual memory address and load memory address must be the overlay's
10870 mapped and load addresses. Identifying overlays with sections allows
10871 @value{GDBN} to determine the appropriate address of a function or
10872 variable, depending on whether the overlay is mapped or not.
10874 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10875 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10880 Disable @value{GDBN}'s overlay support. When overlay support is
10881 disabled, @value{GDBN} assumes that all functions and variables are
10882 always present at their mapped addresses. By default, @value{GDBN}'s
10883 overlay support is disabled.
10885 @item overlay manual
10886 @cindex manual overlay debugging
10887 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10888 relies on you to tell it which overlays are mapped, and which are not,
10889 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10890 commands described below.
10892 @item overlay map-overlay @var{overlay}
10893 @itemx overlay map @var{overlay}
10894 @cindex map an overlay
10895 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10896 be the name of the object file section containing the overlay. When an
10897 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10898 functions and variables at their mapped addresses. @value{GDBN} assumes
10899 that any other overlays whose mapped ranges overlap that of
10900 @var{overlay} are now unmapped.
10902 @item overlay unmap-overlay @var{overlay}
10903 @itemx overlay unmap @var{overlay}
10904 @cindex unmap an overlay
10905 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10906 must be the name of the object file section containing the overlay.
10907 When an overlay is unmapped, @value{GDBN} assumes it can find the
10908 overlay's functions and variables at their load addresses.
10911 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10912 consults a data structure the overlay manager maintains in the inferior
10913 to see which overlays are mapped. For details, see @ref{Automatic
10914 Overlay Debugging}.
10916 @item overlay load-target
10917 @itemx overlay load
10918 @cindex reloading the overlay table
10919 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10920 re-reads the table @value{GDBN} automatically each time the inferior
10921 stops, so this command should only be necessary if you have changed the
10922 overlay mapping yourself using @value{GDBN}. This command is only
10923 useful when using automatic overlay debugging.
10925 @item overlay list-overlays
10926 @itemx overlay list
10927 @cindex listing mapped overlays
10928 Display a list of the overlays currently mapped, along with their mapped
10929 addresses, load addresses, and sizes.
10933 Normally, when @value{GDBN} prints a code address, it includes the name
10934 of the function the address falls in:
10937 (@value{GDBP}) print main
10938 $3 = @{int ()@} 0x11a0 <main>
10941 When overlay debugging is enabled, @value{GDBN} recognizes code in
10942 unmapped overlays, and prints the names of unmapped functions with
10943 asterisks around them. For example, if @code{foo} is a function in an
10944 unmapped overlay, @value{GDBN} prints it this way:
10947 (@value{GDBP}) overlay list
10948 No sections are mapped.
10949 (@value{GDBP}) print foo
10950 $5 = @{int (int)@} 0x100000 <*foo*>
10953 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10957 (@value{GDBP}) overlay list
10958 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10959 mapped at 0x1016 - 0x104a
10960 (@value{GDBP}) print foo
10961 $6 = @{int (int)@} 0x1016 <foo>
10964 When overlay debugging is enabled, @value{GDBN} can find the correct
10965 address for functions and variables in an overlay, whether or not the
10966 overlay is mapped. This allows most @value{GDBN} commands, like
10967 @code{break} and @code{disassemble}, to work normally, even on unmapped
10968 code. However, @value{GDBN}'s breakpoint support has some limitations:
10972 @cindex breakpoints in overlays
10973 @cindex overlays, setting breakpoints in
10974 You can set breakpoints in functions in unmapped overlays, as long as
10975 @value{GDBN} can write to the overlay at its load address.
10977 @value{GDBN} can not set hardware or simulator-based breakpoints in
10978 unmapped overlays. However, if you set a breakpoint at the end of your
10979 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10980 you are using manual overlay management), @value{GDBN} will re-set its
10981 breakpoints properly.
10985 @node Automatic Overlay Debugging
10986 @section Automatic Overlay Debugging
10987 @cindex automatic overlay debugging
10989 @value{GDBN} can automatically track which overlays are mapped and which
10990 are not, given some simple co-operation from the overlay manager in the
10991 inferior. If you enable automatic overlay debugging with the
10992 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
10993 looks in the inferior's memory for certain variables describing the
10994 current state of the overlays.
10996 Here are the variables your overlay manager must define to support
10997 @value{GDBN}'s automatic overlay debugging:
11001 @item @code{_ovly_table}:
11002 This variable must be an array of the following structures:
11007 /* The overlay's mapped address. */
11010 /* The size of the overlay, in bytes. */
11011 unsigned long size;
11013 /* The overlay's load address. */
11016 /* Non-zero if the overlay is currently mapped;
11018 unsigned long mapped;
11022 @item @code{_novlys}:
11023 This variable must be a four-byte signed integer, holding the total
11024 number of elements in @code{_ovly_table}.
11028 To decide whether a particular overlay is mapped or not, @value{GDBN}
11029 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11030 @code{lma} members equal the VMA and LMA of the overlay's section in the
11031 executable file. When @value{GDBN} finds a matching entry, it consults
11032 the entry's @code{mapped} member to determine whether the overlay is
11035 In addition, your overlay manager may define a function called
11036 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11037 will silently set a breakpoint there. If the overlay manager then
11038 calls this function whenever it has changed the overlay table, this
11039 will enable @value{GDBN} to accurately keep track of which overlays
11040 are in program memory, and update any breakpoints that may be set
11041 in overlays. This will allow breakpoints to work even if the
11042 overlays are kept in ROM or other non-writable memory while they
11043 are not being executed.
11045 @node Overlay Sample Program
11046 @section Overlay Sample Program
11047 @cindex overlay example program
11049 When linking a program which uses overlays, you must place the overlays
11050 at their load addresses, while relocating them to run at their mapped
11051 addresses. To do this, you must write a linker script (@pxref{Overlay
11052 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11053 since linker scripts are specific to a particular host system, target
11054 architecture, and target memory layout, this manual cannot provide
11055 portable sample code demonstrating @value{GDBN}'s overlay support.
11057 However, the @value{GDBN} source distribution does contain an overlaid
11058 program, with linker scripts for a few systems, as part of its test
11059 suite. The program consists of the following files from
11060 @file{gdb/testsuite/gdb.base}:
11064 The main program file.
11066 A simple overlay manager, used by @file{overlays.c}.
11071 Overlay modules, loaded and used by @file{overlays.c}.
11074 Linker scripts for linking the test program on the @code{d10v-elf}
11075 and @code{m32r-elf} targets.
11078 You can build the test program using the @code{d10v-elf} GCC
11079 cross-compiler like this:
11082 $ d10v-elf-gcc -g -c overlays.c
11083 $ d10v-elf-gcc -g -c ovlymgr.c
11084 $ d10v-elf-gcc -g -c foo.c
11085 $ d10v-elf-gcc -g -c bar.c
11086 $ d10v-elf-gcc -g -c baz.c
11087 $ d10v-elf-gcc -g -c grbx.c
11088 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11089 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11092 The build process is identical for any other architecture, except that
11093 you must substitute the appropriate compiler and linker script for the
11094 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11098 @chapter Using @value{GDBN} with Different Languages
11101 Although programming languages generally have common aspects, they are
11102 rarely expressed in the same manner. For instance, in ANSI C,
11103 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11104 Modula-2, it is accomplished by @code{p^}. Values can also be
11105 represented (and displayed) differently. Hex numbers in C appear as
11106 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11108 @cindex working language
11109 Language-specific information is built into @value{GDBN} for some languages,
11110 allowing you to express operations like the above in your program's
11111 native language, and allowing @value{GDBN} to output values in a manner
11112 consistent with the syntax of your program's native language. The
11113 language you use to build expressions is called the @dfn{working
11117 * Setting:: Switching between source languages
11118 * Show:: Displaying the language
11119 * Checks:: Type and range checks
11120 * Supported Languages:: Supported languages
11121 * Unsupported Languages:: Unsupported languages
11125 @section Switching Between Source Languages
11127 There are two ways to control the working language---either have @value{GDBN}
11128 set it automatically, or select it manually yourself. You can use the
11129 @code{set language} command for either purpose. On startup, @value{GDBN}
11130 defaults to setting the language automatically. The working language is
11131 used to determine how expressions you type are interpreted, how values
11134 In addition to the working language, every source file that
11135 @value{GDBN} knows about has its own working language. For some object
11136 file formats, the compiler might indicate which language a particular
11137 source file is in. However, most of the time @value{GDBN} infers the
11138 language from the name of the file. The language of a source file
11139 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11140 show each frame appropriately for its own language. There is no way to
11141 set the language of a source file from within @value{GDBN}, but you can
11142 set the language associated with a filename extension. @xref{Show, ,
11143 Displaying the Language}.
11145 This is most commonly a problem when you use a program, such
11146 as @code{cfront} or @code{f2c}, that generates C but is written in
11147 another language. In that case, make the
11148 program use @code{#line} directives in its C output; that way
11149 @value{GDBN} will know the correct language of the source code of the original
11150 program, and will display that source code, not the generated C code.
11153 * Filenames:: Filename extensions and languages.
11154 * Manually:: Setting the working language manually
11155 * Automatically:: Having @value{GDBN} infer the source language
11159 @subsection List of Filename Extensions and Languages
11161 If a source file name ends in one of the following extensions, then
11162 @value{GDBN} infers that its language is the one indicated.
11180 C@t{++} source file
11186 Objective-C source file
11190 Fortran source file
11193 Modula-2 source file
11197 Assembler source file. This actually behaves almost like C, but
11198 @value{GDBN} does not skip over function prologues when stepping.
11201 In addition, you may set the language associated with a filename
11202 extension. @xref{Show, , Displaying the Language}.
11205 @subsection Setting the Working Language
11207 If you allow @value{GDBN} to set the language automatically,
11208 expressions are interpreted the same way in your debugging session and
11211 @kindex set language
11212 If you wish, you may set the language manually. To do this, issue the
11213 command @samp{set language @var{lang}}, where @var{lang} is the name of
11214 a language, such as
11215 @code{c} or @code{modula-2}.
11216 For a list of the supported languages, type @samp{set language}.
11218 Setting the language manually prevents @value{GDBN} from updating the working
11219 language automatically. This can lead to confusion if you try
11220 to debug a program when the working language is not the same as the
11221 source language, when an expression is acceptable to both
11222 languages---but means different things. For instance, if the current
11223 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11231 might not have the effect you intended. In C, this means to add
11232 @code{b} and @code{c} and place the result in @code{a}. The result
11233 printed would be the value of @code{a}. In Modula-2, this means to compare
11234 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11236 @node Automatically
11237 @subsection Having @value{GDBN} Infer the Source Language
11239 To have @value{GDBN} set the working language automatically, use
11240 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11241 then infers the working language. That is, when your program stops in a
11242 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11243 working language to the language recorded for the function in that
11244 frame. If the language for a frame is unknown (that is, if the function
11245 or block corresponding to the frame was defined in a source file that
11246 does not have a recognized extension), the current working language is
11247 not changed, and @value{GDBN} issues a warning.
11249 This may not seem necessary for most programs, which are written
11250 entirely in one source language. However, program modules and libraries
11251 written in one source language can be used by a main program written in
11252 a different source language. Using @samp{set language auto} in this
11253 case frees you from having to set the working language manually.
11256 @section Displaying the Language
11258 The following commands help you find out which language is the
11259 working language, and also what language source files were written in.
11262 @item show language
11263 @kindex show language
11264 Display the current working language. This is the
11265 language you can use with commands such as @code{print} to
11266 build and compute expressions that may involve variables in your program.
11269 @kindex info frame@r{, show the source language}
11270 Display the source language for this frame. This language becomes the
11271 working language if you use an identifier from this frame.
11272 @xref{Frame Info, ,Information about a Frame}, to identify the other
11273 information listed here.
11276 @kindex info source@r{, show the source language}
11277 Display the source language of this source file.
11278 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11279 information listed here.
11282 In unusual circumstances, you may have source files with extensions
11283 not in the standard list. You can then set the extension associated
11284 with a language explicitly:
11287 @item set extension-language @var{ext} @var{language}
11288 @kindex set extension-language
11289 Tell @value{GDBN} that source files with extension @var{ext} are to be
11290 assumed as written in the source language @var{language}.
11292 @item info extensions
11293 @kindex info extensions
11294 List all the filename extensions and the associated languages.
11298 @section Type and Range Checking
11301 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11302 checking are included, but they do not yet have any effect. This
11303 section documents the intended facilities.
11305 @c FIXME remove warning when type/range code added
11307 Some languages are designed to guard you against making seemingly common
11308 errors through a series of compile- and run-time checks. These include
11309 checking the type of arguments to functions and operators, and making
11310 sure mathematical overflows are caught at run time. Checks such as
11311 these help to ensure a program's correctness once it has been compiled
11312 by eliminating type mismatches, and providing active checks for range
11313 errors when your program is running.
11315 @value{GDBN} can check for conditions like the above if you wish.
11316 Although @value{GDBN} does not check the statements in your program,
11317 it can check expressions entered directly into @value{GDBN} for
11318 evaluation via the @code{print} command, for example. As with the
11319 working language, @value{GDBN} can also decide whether or not to check
11320 automatically based on your program's source language.
11321 @xref{Supported Languages, ,Supported Languages}, for the default
11322 settings of supported languages.
11325 * Type Checking:: An overview of type checking
11326 * Range Checking:: An overview of range checking
11329 @cindex type checking
11330 @cindex checks, type
11331 @node Type Checking
11332 @subsection An Overview of Type Checking
11334 Some languages, such as Modula-2, are strongly typed, meaning that the
11335 arguments to operators and functions have to be of the correct type,
11336 otherwise an error occurs. These checks prevent type mismatch
11337 errors from ever causing any run-time problems. For example,
11345 The second example fails because the @code{CARDINAL} 1 is not
11346 type-compatible with the @code{REAL} 2.3.
11348 For the expressions you use in @value{GDBN} commands, you can tell the
11349 @value{GDBN} type checker to skip checking;
11350 to treat any mismatches as errors and abandon the expression;
11351 or to only issue warnings when type mismatches occur,
11352 but evaluate the expression anyway. When you choose the last of
11353 these, @value{GDBN} evaluates expressions like the second example above, but
11354 also issues a warning.
11356 Even if you turn type checking off, there may be other reasons
11357 related to type that prevent @value{GDBN} from evaluating an expression.
11358 For instance, @value{GDBN} does not know how to add an @code{int} and
11359 a @code{struct foo}. These particular type errors have nothing to do
11360 with the language in use, and usually arise from expressions, such as
11361 the one described above, which make little sense to evaluate anyway.
11363 Each language defines to what degree it is strict about type. For
11364 instance, both Modula-2 and C require the arguments to arithmetical
11365 operators to be numbers. In C, enumerated types and pointers can be
11366 represented as numbers, so that they are valid arguments to mathematical
11367 operators. @xref{Supported Languages, ,Supported Languages}, for further
11368 details on specific languages.
11370 @value{GDBN} provides some additional commands for controlling the type checker:
11372 @kindex set check type
11373 @kindex show check type
11375 @item set check type auto
11376 Set type checking on or off based on the current working language.
11377 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11380 @item set check type on
11381 @itemx set check type off
11382 Set type checking on or off, overriding the default setting for the
11383 current working language. Issue a warning if the setting does not
11384 match the language default. If any type mismatches occur in
11385 evaluating an expression while type checking is on, @value{GDBN} prints a
11386 message and aborts evaluation of the expression.
11388 @item set check type warn
11389 Cause the type checker to issue warnings, but to always attempt to
11390 evaluate the expression. Evaluating the expression may still
11391 be impossible for other reasons. For example, @value{GDBN} cannot add
11392 numbers and structures.
11395 Show the current setting of the type checker, and whether or not @value{GDBN}
11396 is setting it automatically.
11399 @cindex range checking
11400 @cindex checks, range
11401 @node Range Checking
11402 @subsection An Overview of Range Checking
11404 In some languages (such as Modula-2), it is an error to exceed the
11405 bounds of a type; this is enforced with run-time checks. Such range
11406 checking is meant to ensure program correctness by making sure
11407 computations do not overflow, or indices on an array element access do
11408 not exceed the bounds of the array.
11410 For expressions you use in @value{GDBN} commands, you can tell
11411 @value{GDBN} to treat range errors in one of three ways: ignore them,
11412 always treat them as errors and abandon the expression, or issue
11413 warnings but evaluate the expression anyway.
11415 A range error can result from numerical overflow, from exceeding an
11416 array index bound, or when you type a constant that is not a member
11417 of any type. Some languages, however, do not treat overflows as an
11418 error. In many implementations of C, mathematical overflow causes the
11419 result to ``wrap around'' to lower values---for example, if @var{m} is
11420 the largest integer value, and @var{s} is the smallest, then
11423 @var{m} + 1 @result{} @var{s}
11426 This, too, is specific to individual languages, and in some cases
11427 specific to individual compilers or machines. @xref{Supported Languages, ,
11428 Supported Languages}, for further details on specific languages.
11430 @value{GDBN} provides some additional commands for controlling the range checker:
11432 @kindex set check range
11433 @kindex show check range
11435 @item set check range auto
11436 Set range checking on or off based on the current working language.
11437 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11440 @item set check range on
11441 @itemx set check range off
11442 Set range checking on or off, overriding the default setting for the
11443 current working language. A warning is issued if the setting does not
11444 match the language default. If a range error occurs and range checking is on,
11445 then a message is printed and evaluation of the expression is aborted.
11447 @item set check range warn
11448 Output messages when the @value{GDBN} range checker detects a range error,
11449 but attempt to evaluate the expression anyway. Evaluating the
11450 expression may still be impossible for other reasons, such as accessing
11451 memory that the process does not own (a typical example from many Unix
11455 Show the current setting of the range checker, and whether or not it is
11456 being set automatically by @value{GDBN}.
11459 @node Supported Languages
11460 @section Supported Languages
11462 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, Pascal,
11463 assembly, Modula-2, and Ada.
11464 @c This is false ...
11465 Some @value{GDBN} features may be used in expressions regardless of the
11466 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11467 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11468 ,Expressions}) can be used with the constructs of any supported
11471 The following sections detail to what degree each source language is
11472 supported by @value{GDBN}. These sections are not meant to be language
11473 tutorials or references, but serve only as a reference guide to what the
11474 @value{GDBN} expression parser accepts, and what input and output
11475 formats should look like for different languages. There are many good
11476 books written on each of these languages; please look to these for a
11477 language reference or tutorial.
11480 * C:: C and C@t{++}
11482 * Objective-C:: Objective-C
11483 * Fortran:: Fortran
11485 * Modula-2:: Modula-2
11490 @subsection C and C@t{++}
11492 @cindex C and C@t{++}
11493 @cindex expressions in C or C@t{++}
11495 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11496 to both languages. Whenever this is the case, we discuss those languages
11500 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11501 @cindex @sc{gnu} C@t{++}
11502 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11503 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11504 effectively, you must compile your C@t{++} programs with a supported
11505 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11506 compiler (@code{aCC}).
11508 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11509 format; if it doesn't work on your system, try the stabs+ debugging
11510 format. You can select those formats explicitly with the @code{g++}
11511 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11512 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11513 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11516 * C Operators:: C and C@t{++} operators
11517 * C Constants:: C and C@t{++} constants
11518 * C Plus Plus Expressions:: C@t{++} expressions
11519 * C Defaults:: Default settings for C and C@t{++}
11520 * C Checks:: C and C@t{++} type and range checks
11521 * Debugging C:: @value{GDBN} and C
11522 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11523 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11527 @subsubsection C and C@t{++} Operators
11529 @cindex C and C@t{++} operators
11531 Operators must be defined on values of specific types. For instance,
11532 @code{+} is defined on numbers, but not on structures. Operators are
11533 often defined on groups of types.
11535 For the purposes of C and C@t{++}, the following definitions hold:
11540 @emph{Integral types} include @code{int} with any of its storage-class
11541 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11544 @emph{Floating-point types} include @code{float}, @code{double}, and
11545 @code{long double} (if supported by the target platform).
11548 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11551 @emph{Scalar types} include all of the above.
11556 The following operators are supported. They are listed here
11557 in order of increasing precedence:
11561 The comma or sequencing operator. Expressions in a comma-separated list
11562 are evaluated from left to right, with the result of the entire
11563 expression being the last expression evaluated.
11566 Assignment. The value of an assignment expression is the value
11567 assigned. Defined on scalar types.
11570 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11571 and translated to @w{@code{@var{a} = @var{a op b}}}.
11572 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11573 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11574 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11577 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11578 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11582 Logical @sc{or}. Defined on integral types.
11585 Logical @sc{and}. Defined on integral types.
11588 Bitwise @sc{or}. Defined on integral types.
11591 Bitwise exclusive-@sc{or}. Defined on integral types.
11594 Bitwise @sc{and}. Defined on integral types.
11597 Equality and inequality. Defined on scalar types. The value of these
11598 expressions is 0 for false and non-zero for true.
11600 @item <@r{, }>@r{, }<=@r{, }>=
11601 Less than, greater than, less than or equal, greater than or equal.
11602 Defined on scalar types. The value of these expressions is 0 for false
11603 and non-zero for true.
11606 left shift, and right shift. Defined on integral types.
11609 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11612 Addition and subtraction. Defined on integral types, floating-point types and
11615 @item *@r{, }/@r{, }%
11616 Multiplication, division, and modulus. Multiplication and division are
11617 defined on integral and floating-point types. Modulus is defined on
11621 Increment and decrement. When appearing before a variable, the
11622 operation is performed before the variable is used in an expression;
11623 when appearing after it, the variable's value is used before the
11624 operation takes place.
11627 Pointer dereferencing. Defined on pointer types. Same precedence as
11631 Address operator. Defined on variables. Same precedence as @code{++}.
11633 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11634 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11635 to examine the address
11636 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11640 Negative. Defined on integral and floating-point types. Same
11641 precedence as @code{++}.
11644 Logical negation. Defined on integral types. Same precedence as
11648 Bitwise complement operator. Defined on integral types. Same precedence as
11653 Structure member, and pointer-to-structure member. For convenience,
11654 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11655 pointer based on the stored type information.
11656 Defined on @code{struct} and @code{union} data.
11659 Dereferences of pointers to members.
11662 Array indexing. @code{@var{a}[@var{i}]} is defined as
11663 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11666 Function parameter list. Same precedence as @code{->}.
11669 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11670 and @code{class} types.
11673 Doubled colons also represent the @value{GDBN} scope operator
11674 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11678 If an operator is redefined in the user code, @value{GDBN} usually
11679 attempts to invoke the redefined version instead of using the operator's
11680 predefined meaning.
11683 @subsubsection C and C@t{++} Constants
11685 @cindex C and C@t{++} constants
11687 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11692 Integer constants are a sequence of digits. Octal constants are
11693 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11694 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11695 @samp{l}, specifying that the constant should be treated as a
11699 Floating point constants are a sequence of digits, followed by a decimal
11700 point, followed by a sequence of digits, and optionally followed by an
11701 exponent. An exponent is of the form:
11702 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11703 sequence of digits. The @samp{+} is optional for positive exponents.
11704 A floating-point constant may also end with a letter @samp{f} or
11705 @samp{F}, specifying that the constant should be treated as being of
11706 the @code{float} (as opposed to the default @code{double}) type; or with
11707 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11711 Enumerated constants consist of enumerated identifiers, or their
11712 integral equivalents.
11715 Character constants are a single character surrounded by single quotes
11716 (@code{'}), or a number---the ordinal value of the corresponding character
11717 (usually its @sc{ascii} value). Within quotes, the single character may
11718 be represented by a letter or by @dfn{escape sequences}, which are of
11719 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11720 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11721 @samp{@var{x}} is a predefined special character---for example,
11722 @samp{\n} for newline.
11725 String constants are a sequence of character constants surrounded by
11726 double quotes (@code{"}). Any valid character constant (as described
11727 above) may appear. Double quotes within the string must be preceded by
11728 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11732 Pointer constants are an integral value. You can also write pointers
11733 to constants using the C operator @samp{&}.
11736 Array constants are comma-separated lists surrounded by braces @samp{@{}
11737 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11738 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11739 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11742 @node C Plus Plus Expressions
11743 @subsubsection C@t{++} Expressions
11745 @cindex expressions in C@t{++}
11746 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11748 @cindex debugging C@t{++} programs
11749 @cindex C@t{++} compilers
11750 @cindex debug formats and C@t{++}
11751 @cindex @value{NGCC} and C@t{++}
11753 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11754 proper compiler and the proper debug format. Currently, @value{GDBN}
11755 works best when debugging C@t{++} code that is compiled with
11756 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11757 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11758 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11759 stabs+ as their default debug format, so you usually don't need to
11760 specify a debug format explicitly. Other compilers and/or debug formats
11761 are likely to work badly or not at all when using @value{GDBN} to debug
11767 @cindex member functions
11769 Member function calls are allowed; you can use expressions like
11772 count = aml->GetOriginal(x, y)
11775 @vindex this@r{, inside C@t{++} member functions}
11776 @cindex namespace in C@t{++}
11778 While a member function is active (in the selected stack frame), your
11779 expressions have the same namespace available as the member function;
11780 that is, @value{GDBN} allows implicit references to the class instance
11781 pointer @code{this} following the same rules as C@t{++}.
11783 @cindex call overloaded functions
11784 @cindex overloaded functions, calling
11785 @cindex type conversions in C@t{++}
11787 You can call overloaded functions; @value{GDBN} resolves the function
11788 call to the right definition, with some restrictions. @value{GDBN} does not
11789 perform overload resolution involving user-defined type conversions,
11790 calls to constructors, or instantiations of templates that do not exist
11791 in the program. It also cannot handle ellipsis argument lists or
11794 It does perform integral conversions and promotions, floating-point
11795 promotions, arithmetic conversions, pointer conversions, conversions of
11796 class objects to base classes, and standard conversions such as those of
11797 functions or arrays to pointers; it requires an exact match on the
11798 number of function arguments.
11800 Overload resolution is always performed, unless you have specified
11801 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11802 ,@value{GDBN} Features for C@t{++}}.
11804 You must specify @code{set overload-resolution off} in order to use an
11805 explicit function signature to call an overloaded function, as in
11807 p 'foo(char,int)'('x', 13)
11810 The @value{GDBN} command-completion facility can simplify this;
11811 see @ref{Completion, ,Command Completion}.
11813 @cindex reference declarations
11815 @value{GDBN} understands variables declared as C@t{++} references; you can use
11816 them in expressions just as you do in C@t{++} source---they are automatically
11819 In the parameter list shown when @value{GDBN} displays a frame, the values of
11820 reference variables are not displayed (unlike other variables); this
11821 avoids clutter, since references are often used for large structures.
11822 The @emph{address} of a reference variable is always shown, unless
11823 you have specified @samp{set print address off}.
11826 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11827 expressions can use it just as expressions in your program do. Since
11828 one scope may be defined in another, you can use @code{::} repeatedly if
11829 necessary, for example in an expression like
11830 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11831 resolving name scope by reference to source files, in both C and C@t{++}
11832 debugging (@pxref{Variables, ,Program Variables}).
11835 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11836 calling virtual functions correctly, printing out virtual bases of
11837 objects, calling functions in a base subobject, casting objects, and
11838 invoking user-defined operators.
11841 @subsubsection C and C@t{++} Defaults
11843 @cindex C and C@t{++} defaults
11845 If you allow @value{GDBN} to set type and range checking automatically, they
11846 both default to @code{off} whenever the working language changes to
11847 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11848 selects the working language.
11850 If you allow @value{GDBN} to set the language automatically, it
11851 recognizes source files whose names end with @file{.c}, @file{.C}, or
11852 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11853 these files, it sets the working language to C or C@t{++}.
11854 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11855 for further details.
11857 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11858 @c unimplemented. If (b) changes, it might make sense to let this node
11859 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11862 @subsubsection C and C@t{++} Type and Range Checks
11864 @cindex C and C@t{++} checks
11866 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11867 is not used. However, if you turn type checking on, @value{GDBN}
11868 considers two variables type equivalent if:
11872 The two variables are structured and have the same structure, union, or
11876 The two variables have the same type name, or types that have been
11877 declared equivalent through @code{typedef}.
11880 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11883 The two @code{struct}, @code{union}, or @code{enum} variables are
11884 declared in the same declaration. (Note: this may not be true for all C
11889 Range checking, if turned on, is done on mathematical operations. Array
11890 indices are not checked, since they are often used to index a pointer
11891 that is not itself an array.
11894 @subsubsection @value{GDBN} and C
11896 The @code{set print union} and @code{show print union} commands apply to
11897 the @code{union} type. When set to @samp{on}, any @code{union} that is
11898 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11899 appears as @samp{@{...@}}.
11901 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11902 with pointers and a memory allocation function. @xref{Expressions,
11905 @node Debugging C Plus Plus
11906 @subsubsection @value{GDBN} Features for C@t{++}
11908 @cindex commands for C@t{++}
11910 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11911 designed specifically for use with C@t{++}. Here is a summary:
11914 @cindex break in overloaded functions
11915 @item @r{breakpoint menus}
11916 When you want a breakpoint in a function whose name is overloaded,
11917 @value{GDBN} has the capability to display a menu of possible breakpoint
11918 locations to help you specify which function definition you want.
11919 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11921 @cindex overloading in C@t{++}
11922 @item rbreak @var{regex}
11923 Setting breakpoints using regular expressions is helpful for setting
11924 breakpoints on overloaded functions that are not members of any special
11926 @xref{Set Breaks, ,Setting Breakpoints}.
11928 @cindex C@t{++} exception handling
11931 Debug C@t{++} exception handling using these commands. @xref{Set
11932 Catchpoints, , Setting Catchpoints}.
11934 @cindex inheritance
11935 @item ptype @var{typename}
11936 Print inheritance relationships as well as other information for type
11938 @xref{Symbols, ,Examining the Symbol Table}.
11940 @cindex C@t{++} symbol display
11941 @item set print demangle
11942 @itemx show print demangle
11943 @itemx set print asm-demangle
11944 @itemx show print asm-demangle
11945 Control whether C@t{++} symbols display in their source form, both when
11946 displaying code as C@t{++} source and when displaying disassemblies.
11947 @xref{Print Settings, ,Print Settings}.
11949 @item set print object
11950 @itemx show print object
11951 Choose whether to print derived (actual) or declared types of objects.
11952 @xref{Print Settings, ,Print Settings}.
11954 @item set print vtbl
11955 @itemx show print vtbl
11956 Control the format for printing virtual function tables.
11957 @xref{Print Settings, ,Print Settings}.
11958 (The @code{vtbl} commands do not work on programs compiled with the HP
11959 ANSI C@t{++} compiler (@code{aCC}).)
11961 @kindex set overload-resolution
11962 @cindex overloaded functions, overload resolution
11963 @item set overload-resolution on
11964 Enable overload resolution for C@t{++} expression evaluation. The default
11965 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11966 and searches for a function whose signature matches the argument types,
11967 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11968 Expressions, ,C@t{++} Expressions}, for details).
11969 If it cannot find a match, it emits a message.
11971 @item set overload-resolution off
11972 Disable overload resolution for C@t{++} expression evaluation. For
11973 overloaded functions that are not class member functions, @value{GDBN}
11974 chooses the first function of the specified name that it finds in the
11975 symbol table, whether or not its arguments are of the correct type. For
11976 overloaded functions that are class member functions, @value{GDBN}
11977 searches for a function whose signature @emph{exactly} matches the
11980 @kindex show overload-resolution
11981 @item show overload-resolution
11982 Show the current setting of overload resolution.
11984 @item @r{Overloaded symbol names}
11985 You can specify a particular definition of an overloaded symbol, using
11986 the same notation that is used to declare such symbols in C@t{++}: type
11987 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
11988 also use the @value{GDBN} command-line word completion facilities to list the
11989 available choices, or to finish the type list for you.
11990 @xref{Completion,, Command Completion}, for details on how to do this.
11993 @node Decimal Floating Point
11994 @subsubsection Decimal Floating Point format
11995 @cindex decimal floating point format
11997 @value{GDBN} can examine, set and perform computations with numbers in
11998 decimal floating point format, which in the C language correspond to the
11999 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12000 specified by the extension to support decimal floating-point arithmetic.
12002 There are two encodings in use, depending on the architecture: BID (Binary
12003 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12004 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12007 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12008 to manipulate decimal floating point numbers, it is not possible to convert
12009 (using a cast, for example) integers wider than 32-bit to decimal float.
12011 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12012 point computations, error checking in decimal float operations ignores
12013 underflow, overflow and divide by zero exceptions.
12015 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12016 to inspect @code{_Decimal128} values stored in floating point registers.
12017 See @ref{PowerPC,,PowerPC} for more details.
12023 @value{GDBN} can be used to debug programs written in D and compiled with
12024 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12025 specific feature --- dynamic arrays.
12028 @subsection Objective-C
12030 @cindex Objective-C
12031 This section provides information about some commands and command
12032 options that are useful for debugging Objective-C code. See also
12033 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12034 few more commands specific to Objective-C support.
12037 * Method Names in Commands::
12038 * The Print Command with Objective-C::
12041 @node Method Names in Commands
12042 @subsubsection Method Names in Commands
12044 The following commands have been extended to accept Objective-C method
12045 names as line specifications:
12047 @kindex clear@r{, and Objective-C}
12048 @kindex break@r{, and Objective-C}
12049 @kindex info line@r{, and Objective-C}
12050 @kindex jump@r{, and Objective-C}
12051 @kindex list@r{, and Objective-C}
12055 @item @code{info line}
12060 A fully qualified Objective-C method name is specified as
12063 -[@var{Class} @var{methodName}]
12066 where the minus sign is used to indicate an instance method and a
12067 plus sign (not shown) is used to indicate a class method. The class
12068 name @var{Class} and method name @var{methodName} are enclosed in
12069 brackets, similar to the way messages are specified in Objective-C
12070 source code. For example, to set a breakpoint at the @code{create}
12071 instance method of class @code{Fruit} in the program currently being
12075 break -[Fruit create]
12078 To list ten program lines around the @code{initialize} class method,
12082 list +[NSText initialize]
12085 In the current version of @value{GDBN}, the plus or minus sign is
12086 required. In future versions of @value{GDBN}, the plus or minus
12087 sign will be optional, but you can use it to narrow the search. It
12088 is also possible to specify just a method name:
12094 You must specify the complete method name, including any colons. If
12095 your program's source files contain more than one @code{create} method,
12096 you'll be presented with a numbered list of classes that implement that
12097 method. Indicate your choice by number, or type @samp{0} to exit if
12100 As another example, to clear a breakpoint established at the
12101 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12104 clear -[NSWindow makeKeyAndOrderFront:]
12107 @node The Print Command with Objective-C
12108 @subsubsection The Print Command With Objective-C
12109 @cindex Objective-C, print objects
12110 @kindex print-object
12111 @kindex po @r{(@code{print-object})}
12113 The print command has also been extended to accept methods. For example:
12116 print -[@var{object} hash]
12119 @cindex print an Objective-C object description
12120 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12122 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12123 and print the result. Also, an additional command has been added,
12124 @code{print-object} or @code{po} for short, which is meant to print
12125 the description of an object. However, this command may only work
12126 with certain Objective-C libraries that have a particular hook
12127 function, @code{_NSPrintForDebugger}, defined.
12130 @subsection Fortran
12131 @cindex Fortran-specific support in @value{GDBN}
12133 @value{GDBN} can be used to debug programs written in Fortran, but it
12134 currently supports only the features of Fortran 77 language.
12136 @cindex trailing underscore, in Fortran symbols
12137 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12138 among them) append an underscore to the names of variables and
12139 functions. When you debug programs compiled by those compilers, you
12140 will need to refer to variables and functions with a trailing
12144 * Fortran Operators:: Fortran operators and expressions
12145 * Fortran Defaults:: Default settings for Fortran
12146 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12149 @node Fortran Operators
12150 @subsubsection Fortran Operators and Expressions
12152 @cindex Fortran operators and expressions
12154 Operators must be defined on values of specific types. For instance,
12155 @code{+} is defined on numbers, but not on characters or other non-
12156 arithmetic types. Operators are often defined on groups of types.
12160 The exponentiation operator. It raises the first operand to the power
12164 The range operator. Normally used in the form of array(low:high) to
12165 represent a section of array.
12168 The access component operator. Normally used to access elements in derived
12169 types. Also suitable for unions. As unions aren't part of regular Fortran,
12170 this can only happen when accessing a register that uses a gdbarch-defined
12174 @node Fortran Defaults
12175 @subsubsection Fortran Defaults
12177 @cindex Fortran Defaults
12179 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12180 default uses case-insensitive matches for Fortran symbols. You can
12181 change that with the @samp{set case-insensitive} command, see
12182 @ref{Symbols}, for the details.
12184 @node Special Fortran Commands
12185 @subsubsection Special Fortran Commands
12187 @cindex Special Fortran commands
12189 @value{GDBN} has some commands to support Fortran-specific features,
12190 such as displaying common blocks.
12193 @cindex @code{COMMON} blocks, Fortran
12194 @kindex info common
12195 @item info common @r{[}@var{common-name}@r{]}
12196 This command prints the values contained in the Fortran @code{COMMON}
12197 block whose name is @var{common-name}. With no argument, the names of
12198 all @code{COMMON} blocks visible at the current program location are
12205 @cindex Pascal support in @value{GDBN}, limitations
12206 Debugging Pascal programs which use sets, subranges, file variables, or
12207 nested functions does not currently work. @value{GDBN} does not support
12208 entering expressions, printing values, or similar features using Pascal
12211 The Pascal-specific command @code{set print pascal_static-members}
12212 controls whether static members of Pascal objects are displayed.
12213 @xref{Print Settings, pascal_static-members}.
12216 @subsection Modula-2
12218 @cindex Modula-2, @value{GDBN} support
12220 The extensions made to @value{GDBN} to support Modula-2 only support
12221 output from the @sc{gnu} Modula-2 compiler (which is currently being
12222 developed). Other Modula-2 compilers are not currently supported, and
12223 attempting to debug executables produced by them is most likely
12224 to give an error as @value{GDBN} reads in the executable's symbol
12227 @cindex expressions in Modula-2
12229 * M2 Operators:: Built-in operators
12230 * Built-In Func/Proc:: Built-in functions and procedures
12231 * M2 Constants:: Modula-2 constants
12232 * M2 Types:: Modula-2 types
12233 * M2 Defaults:: Default settings for Modula-2
12234 * Deviations:: Deviations from standard Modula-2
12235 * M2 Checks:: Modula-2 type and range checks
12236 * M2 Scope:: The scope operators @code{::} and @code{.}
12237 * GDB/M2:: @value{GDBN} and Modula-2
12241 @subsubsection Operators
12242 @cindex Modula-2 operators
12244 Operators must be defined on values of specific types. For instance,
12245 @code{+} is defined on numbers, but not on structures. Operators are
12246 often defined on groups of types. For the purposes of Modula-2, the
12247 following definitions hold:
12252 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12256 @emph{Character types} consist of @code{CHAR} and its subranges.
12259 @emph{Floating-point types} consist of @code{REAL}.
12262 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12266 @emph{Scalar types} consist of all of the above.
12269 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12272 @emph{Boolean types} consist of @code{BOOLEAN}.
12276 The following operators are supported, and appear in order of
12277 increasing precedence:
12281 Function argument or array index separator.
12284 Assignment. The value of @var{var} @code{:=} @var{value} is
12288 Less than, greater than on integral, floating-point, or enumerated
12292 Less than or equal to, greater than or equal to
12293 on integral, floating-point and enumerated types, or set inclusion on
12294 set types. Same precedence as @code{<}.
12296 @item =@r{, }<>@r{, }#
12297 Equality and two ways of expressing inequality, valid on scalar types.
12298 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12299 available for inequality, since @code{#} conflicts with the script
12303 Set membership. Defined on set types and the types of their members.
12304 Same precedence as @code{<}.
12307 Boolean disjunction. Defined on boolean types.
12310 Boolean conjunction. Defined on boolean types.
12313 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12316 Addition and subtraction on integral and floating-point types, or union
12317 and difference on set types.
12320 Multiplication on integral and floating-point types, or set intersection
12324 Division on floating-point types, or symmetric set difference on set
12325 types. Same precedence as @code{*}.
12328 Integer division and remainder. Defined on integral types. Same
12329 precedence as @code{*}.
12332 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12335 Pointer dereferencing. Defined on pointer types.
12338 Boolean negation. Defined on boolean types. Same precedence as
12342 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12343 precedence as @code{^}.
12346 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12349 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12353 @value{GDBN} and Modula-2 scope operators.
12357 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12358 treats the use of the operator @code{IN}, or the use of operators
12359 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12360 @code{<=}, and @code{>=} on sets as an error.
12364 @node Built-In Func/Proc
12365 @subsubsection Built-in Functions and Procedures
12366 @cindex Modula-2 built-ins
12368 Modula-2 also makes available several built-in procedures and functions.
12369 In describing these, the following metavariables are used:
12374 represents an @code{ARRAY} variable.
12377 represents a @code{CHAR} constant or variable.
12380 represents a variable or constant of integral type.
12383 represents an identifier that belongs to a set. Generally used in the
12384 same function with the metavariable @var{s}. The type of @var{s} should
12385 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12388 represents a variable or constant of integral or floating-point type.
12391 represents a variable or constant of floating-point type.
12397 represents a variable.
12400 represents a variable or constant of one of many types. See the
12401 explanation of the function for details.
12404 All Modula-2 built-in procedures also return a result, described below.
12408 Returns the absolute value of @var{n}.
12411 If @var{c} is a lower case letter, it returns its upper case
12412 equivalent, otherwise it returns its argument.
12415 Returns the character whose ordinal value is @var{i}.
12418 Decrements the value in the variable @var{v} by one. Returns the new value.
12420 @item DEC(@var{v},@var{i})
12421 Decrements the value in the variable @var{v} by @var{i}. Returns the
12424 @item EXCL(@var{m},@var{s})
12425 Removes the element @var{m} from the set @var{s}. Returns the new
12428 @item FLOAT(@var{i})
12429 Returns the floating point equivalent of the integer @var{i}.
12431 @item HIGH(@var{a})
12432 Returns the index of the last member of @var{a}.
12435 Increments the value in the variable @var{v} by one. Returns the new value.
12437 @item INC(@var{v},@var{i})
12438 Increments the value in the variable @var{v} by @var{i}. Returns the
12441 @item INCL(@var{m},@var{s})
12442 Adds the element @var{m} to the set @var{s} if it is not already
12443 there. Returns the new set.
12446 Returns the maximum value of the type @var{t}.
12449 Returns the minimum value of the type @var{t}.
12452 Returns boolean TRUE if @var{i} is an odd number.
12455 Returns the ordinal value of its argument. For example, the ordinal
12456 value of a character is its @sc{ascii} value (on machines supporting the
12457 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12458 integral, character and enumerated types.
12460 @item SIZE(@var{x})
12461 Returns the size of its argument. @var{x} can be a variable or a type.
12463 @item TRUNC(@var{r})
12464 Returns the integral part of @var{r}.
12466 @item TSIZE(@var{x})
12467 Returns the size of its argument. @var{x} can be a variable or a type.
12469 @item VAL(@var{t},@var{i})
12470 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12474 @emph{Warning:} Sets and their operations are not yet supported, so
12475 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12479 @cindex Modula-2 constants
12481 @subsubsection Constants
12483 @value{GDBN} allows you to express the constants of Modula-2 in the following
12489 Integer constants are simply a sequence of digits. When used in an
12490 expression, a constant is interpreted to be type-compatible with the
12491 rest of the expression. Hexadecimal integers are specified by a
12492 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12495 Floating point constants appear as a sequence of digits, followed by a
12496 decimal point and another sequence of digits. An optional exponent can
12497 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12498 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12499 digits of the floating point constant must be valid decimal (base 10)
12503 Character constants consist of a single character enclosed by a pair of
12504 like quotes, either single (@code{'}) or double (@code{"}). They may
12505 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12506 followed by a @samp{C}.
12509 String constants consist of a sequence of characters enclosed by a
12510 pair of like quotes, either single (@code{'}) or double (@code{"}).
12511 Escape sequences in the style of C are also allowed. @xref{C
12512 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12516 Enumerated constants consist of an enumerated identifier.
12519 Boolean constants consist of the identifiers @code{TRUE} and
12523 Pointer constants consist of integral values only.
12526 Set constants are not yet supported.
12530 @subsubsection Modula-2 Types
12531 @cindex Modula-2 types
12533 Currently @value{GDBN} can print the following data types in Modula-2
12534 syntax: array types, record types, set types, pointer types, procedure
12535 types, enumerated types, subrange types and base types. You can also
12536 print the contents of variables declared using these type.
12537 This section gives a number of simple source code examples together with
12538 sample @value{GDBN} sessions.
12540 The first example contains the following section of code:
12549 and you can request @value{GDBN} to interrogate the type and value of
12550 @code{r} and @code{s}.
12553 (@value{GDBP}) print s
12555 (@value{GDBP}) ptype s
12557 (@value{GDBP}) print r
12559 (@value{GDBP}) ptype r
12564 Likewise if your source code declares @code{s} as:
12568 s: SET ['A'..'Z'] ;
12572 then you may query the type of @code{s} by:
12575 (@value{GDBP}) ptype s
12576 type = SET ['A'..'Z']
12580 Note that at present you cannot interactively manipulate set
12581 expressions using the debugger.
12583 The following example shows how you might declare an array in Modula-2
12584 and how you can interact with @value{GDBN} to print its type and contents:
12588 s: ARRAY [-10..10] OF CHAR ;
12592 (@value{GDBP}) ptype s
12593 ARRAY [-10..10] OF CHAR
12596 Note that the array handling is not yet complete and although the type
12597 is printed correctly, expression handling still assumes that all
12598 arrays have a lower bound of zero and not @code{-10} as in the example
12601 Here are some more type related Modula-2 examples:
12605 colour = (blue, red, yellow, green) ;
12606 t = [blue..yellow] ;
12614 The @value{GDBN} interaction shows how you can query the data type
12615 and value of a variable.
12618 (@value{GDBP}) print s
12620 (@value{GDBP}) ptype t
12621 type = [blue..yellow]
12625 In this example a Modula-2 array is declared and its contents
12626 displayed. Observe that the contents are written in the same way as
12627 their @code{C} counterparts.
12631 s: ARRAY [1..5] OF CARDINAL ;
12637 (@value{GDBP}) print s
12638 $1 = @{1, 0, 0, 0, 0@}
12639 (@value{GDBP}) ptype s
12640 type = ARRAY [1..5] OF CARDINAL
12643 The Modula-2 language interface to @value{GDBN} also understands
12644 pointer types as shown in this example:
12648 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12655 and you can request that @value{GDBN} describes the type of @code{s}.
12658 (@value{GDBP}) ptype s
12659 type = POINTER TO ARRAY [1..5] OF CARDINAL
12662 @value{GDBN} handles compound types as we can see in this example.
12663 Here we combine array types, record types, pointer types and subrange
12674 myarray = ARRAY myrange OF CARDINAL ;
12675 myrange = [-2..2] ;
12677 s: POINTER TO ARRAY myrange OF foo ;
12681 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12685 (@value{GDBP}) ptype s
12686 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12689 f3 : ARRAY [-2..2] OF CARDINAL;
12694 @subsubsection Modula-2 Defaults
12695 @cindex Modula-2 defaults
12697 If type and range checking are set automatically by @value{GDBN}, they
12698 both default to @code{on} whenever the working language changes to
12699 Modula-2. This happens regardless of whether you or @value{GDBN}
12700 selected the working language.
12702 If you allow @value{GDBN} to set the language automatically, then entering
12703 code compiled from a file whose name ends with @file{.mod} sets the
12704 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12705 Infer the Source Language}, for further details.
12708 @subsubsection Deviations from Standard Modula-2
12709 @cindex Modula-2, deviations from
12711 A few changes have been made to make Modula-2 programs easier to debug.
12712 This is done primarily via loosening its type strictness:
12716 Unlike in standard Modula-2, pointer constants can be formed by
12717 integers. This allows you to modify pointer variables during
12718 debugging. (In standard Modula-2, the actual address contained in a
12719 pointer variable is hidden from you; it can only be modified
12720 through direct assignment to another pointer variable or expression that
12721 returned a pointer.)
12724 C escape sequences can be used in strings and characters to represent
12725 non-printable characters. @value{GDBN} prints out strings with these
12726 escape sequences embedded. Single non-printable characters are
12727 printed using the @samp{CHR(@var{nnn})} format.
12730 The assignment operator (@code{:=}) returns the value of its right-hand
12734 All built-in procedures both modify @emph{and} return their argument.
12738 @subsubsection Modula-2 Type and Range Checks
12739 @cindex Modula-2 checks
12742 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12745 @c FIXME remove warning when type/range checks added
12747 @value{GDBN} considers two Modula-2 variables type equivalent if:
12751 They are of types that have been declared equivalent via a @code{TYPE
12752 @var{t1} = @var{t2}} statement
12755 They have been declared on the same line. (Note: This is true of the
12756 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12759 As long as type checking is enabled, any attempt to combine variables
12760 whose types are not equivalent is an error.
12762 Range checking is done on all mathematical operations, assignment, array
12763 index bounds, and all built-in functions and procedures.
12766 @subsubsection The Scope Operators @code{::} and @code{.}
12768 @cindex @code{.}, Modula-2 scope operator
12769 @cindex colon, doubled as scope operator
12771 @vindex colon-colon@r{, in Modula-2}
12772 @c Info cannot handle :: but TeX can.
12775 @vindex ::@r{, in Modula-2}
12778 There are a few subtle differences between the Modula-2 scope operator
12779 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12784 @var{module} . @var{id}
12785 @var{scope} :: @var{id}
12789 where @var{scope} is the name of a module or a procedure,
12790 @var{module} the name of a module, and @var{id} is any declared
12791 identifier within your program, except another module.
12793 Using the @code{::} operator makes @value{GDBN} search the scope
12794 specified by @var{scope} for the identifier @var{id}. If it is not
12795 found in the specified scope, then @value{GDBN} searches all scopes
12796 enclosing the one specified by @var{scope}.
12798 Using the @code{.} operator makes @value{GDBN} search the current scope for
12799 the identifier specified by @var{id} that was imported from the
12800 definition module specified by @var{module}. With this operator, it is
12801 an error if the identifier @var{id} was not imported from definition
12802 module @var{module}, or if @var{id} is not an identifier in
12806 @subsubsection @value{GDBN} and Modula-2
12808 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12809 Five subcommands of @code{set print} and @code{show print} apply
12810 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12811 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12812 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12813 analogue in Modula-2.
12815 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12816 with any language, is not useful with Modula-2. Its
12817 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12818 created in Modula-2 as they can in C or C@t{++}. However, because an
12819 address can be specified by an integral constant, the construct
12820 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12822 @cindex @code{#} in Modula-2
12823 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12824 interpreted as the beginning of a comment. Use @code{<>} instead.
12830 The extensions made to @value{GDBN} for Ada only support
12831 output from the @sc{gnu} Ada (GNAT) compiler.
12832 Other Ada compilers are not currently supported, and
12833 attempting to debug executables produced by them is most likely
12837 @cindex expressions in Ada
12839 * Ada Mode Intro:: General remarks on the Ada syntax
12840 and semantics supported by Ada mode
12842 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12843 * Additions to Ada:: Extensions of the Ada expression syntax.
12844 * Stopping Before Main Program:: Debugging the program during elaboration.
12845 * Ada Tasks:: Listing and setting breakpoints in tasks.
12846 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12847 * Ada Glitches:: Known peculiarities of Ada mode.
12850 @node Ada Mode Intro
12851 @subsubsection Introduction
12852 @cindex Ada mode, general
12854 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12855 syntax, with some extensions.
12856 The philosophy behind the design of this subset is
12860 That @value{GDBN} should provide basic literals and access to operations for
12861 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12862 leaving more sophisticated computations to subprograms written into the
12863 program (which therefore may be called from @value{GDBN}).
12866 That type safety and strict adherence to Ada language restrictions
12867 are not particularly important to the @value{GDBN} user.
12870 That brevity is important to the @value{GDBN} user.
12873 Thus, for brevity, the debugger acts as if all names declared in
12874 user-written packages are directly visible, even if they are not visible
12875 according to Ada rules, thus making it unnecessary to fully qualify most
12876 names with their packages, regardless of context. Where this causes
12877 ambiguity, @value{GDBN} asks the user's intent.
12879 The debugger will start in Ada mode if it detects an Ada main program.
12880 As for other languages, it will enter Ada mode when stopped in a program that
12881 was translated from an Ada source file.
12883 While in Ada mode, you may use `@t{--}' for comments. This is useful
12884 mostly for documenting command files. The standard @value{GDBN} comment
12885 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12886 middle (to allow based literals).
12888 The debugger supports limited overloading. Given a subprogram call in which
12889 the function symbol has multiple definitions, it will use the number of
12890 actual parameters and some information about their types to attempt to narrow
12891 the set of definitions. It also makes very limited use of context, preferring
12892 procedures to functions in the context of the @code{call} command, and
12893 functions to procedures elsewhere.
12895 @node Omissions from Ada
12896 @subsubsection Omissions from Ada
12897 @cindex Ada, omissions from
12899 Here are the notable omissions from the subset:
12903 Only a subset of the attributes are supported:
12907 @t{'First}, @t{'Last}, and @t{'Length}
12908 on array objects (not on types and subtypes).
12911 @t{'Min} and @t{'Max}.
12914 @t{'Pos} and @t{'Val}.
12920 @t{'Range} on array objects (not subtypes), but only as the right
12921 operand of the membership (@code{in}) operator.
12924 @t{'Access}, @t{'Unchecked_Access}, and
12925 @t{'Unrestricted_Access} (a GNAT extension).
12933 @code{Characters.Latin_1} are not available and
12934 concatenation is not implemented. Thus, escape characters in strings are
12935 not currently available.
12938 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12939 equality of representations. They will generally work correctly
12940 for strings and arrays whose elements have integer or enumeration types.
12941 They may not work correctly for arrays whose element
12942 types have user-defined equality, for arrays of real values
12943 (in particular, IEEE-conformant floating point, because of negative
12944 zeroes and NaNs), and for arrays whose elements contain unused bits with
12945 indeterminate values.
12948 The other component-by-component array operations (@code{and}, @code{or},
12949 @code{xor}, @code{not}, and relational tests other than equality)
12950 are not implemented.
12953 @cindex array aggregates (Ada)
12954 @cindex record aggregates (Ada)
12955 @cindex aggregates (Ada)
12956 There is limited support for array and record aggregates. They are
12957 permitted only on the right sides of assignments, as in these examples:
12960 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12961 (@value{GDBP}) set An_Array := (1, others => 0)
12962 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12963 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12964 (@value{GDBP}) set A_Record := (1, "Peter", True);
12965 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12969 discriminant's value by assigning an aggregate has an
12970 undefined effect if that discriminant is used within the record.
12971 However, you can first modify discriminants by directly assigning to
12972 them (which normally would not be allowed in Ada), and then performing an
12973 aggregate assignment. For example, given a variable @code{A_Rec}
12974 declared to have a type such as:
12977 type Rec (Len : Small_Integer := 0) is record
12979 Vals : IntArray (1 .. Len);
12983 you can assign a value with a different size of @code{Vals} with two
12987 (@value{GDBP}) set A_Rec.Len := 4
12988 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
12991 As this example also illustrates, @value{GDBN} is very loose about the usual
12992 rules concerning aggregates. You may leave out some of the
12993 components of an array or record aggregate (such as the @code{Len}
12994 component in the assignment to @code{A_Rec} above); they will retain their
12995 original values upon assignment. You may freely use dynamic values as
12996 indices in component associations. You may even use overlapping or
12997 redundant component associations, although which component values are
12998 assigned in such cases is not defined.
13001 Calls to dispatching subprograms are not implemented.
13004 The overloading algorithm is much more limited (i.e., less selective)
13005 than that of real Ada. It makes only limited use of the context in
13006 which a subexpression appears to resolve its meaning, and it is much
13007 looser in its rules for allowing type matches. As a result, some
13008 function calls will be ambiguous, and the user will be asked to choose
13009 the proper resolution.
13012 The @code{new} operator is not implemented.
13015 Entry calls are not implemented.
13018 Aside from printing, arithmetic operations on the native VAX floating-point
13019 formats are not supported.
13022 It is not possible to slice a packed array.
13025 The names @code{True} and @code{False}, when not part of a qualified name,
13026 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13028 Should your program
13029 redefine these names in a package or procedure (at best a dubious practice),
13030 you will have to use fully qualified names to access their new definitions.
13033 @node Additions to Ada
13034 @subsubsection Additions to Ada
13035 @cindex Ada, deviations from
13037 As it does for other languages, @value{GDBN} makes certain generic
13038 extensions to Ada (@pxref{Expressions}):
13042 If the expression @var{E} is a variable residing in memory (typically
13043 a local variable or array element) and @var{N} is a positive integer,
13044 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13045 @var{N}-1 adjacent variables following it in memory as an array. In
13046 Ada, this operator is generally not necessary, since its prime use is
13047 in displaying parts of an array, and slicing will usually do this in
13048 Ada. However, there are occasional uses when debugging programs in
13049 which certain debugging information has been optimized away.
13052 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13053 appears in function or file @var{B}.'' When @var{B} is a file name,
13054 you must typically surround it in single quotes.
13057 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13058 @var{type} that appears at address @var{addr}.''
13061 A name starting with @samp{$} is a convenience variable
13062 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13065 In addition, @value{GDBN} provides a few other shortcuts and outright
13066 additions specific to Ada:
13070 The assignment statement is allowed as an expression, returning
13071 its right-hand operand as its value. Thus, you may enter
13074 (@value{GDBP}) set x := y + 3
13075 (@value{GDBP}) print A(tmp := y + 1)
13079 The semicolon is allowed as an ``operator,'' returning as its value
13080 the value of its right-hand operand.
13081 This allows, for example,
13082 complex conditional breaks:
13085 (@value{GDBP}) break f
13086 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13090 Rather than use catenation and symbolic character names to introduce special
13091 characters into strings, one may instead use a special bracket notation,
13092 which is also used to print strings. A sequence of characters of the form
13093 @samp{["@var{XX}"]} within a string or character literal denotes the
13094 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13095 sequence of characters @samp{["""]} also denotes a single quotation mark
13096 in strings. For example,
13098 "One line.["0a"]Next line.["0a"]"
13101 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13105 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13106 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13110 (@value{GDBP}) print 'max(x, y)
13114 When printing arrays, @value{GDBN} uses positional notation when the
13115 array has a lower bound of 1, and uses a modified named notation otherwise.
13116 For example, a one-dimensional array of three integers with a lower bound
13117 of 3 might print as
13124 That is, in contrast to valid Ada, only the first component has a @code{=>}
13128 You may abbreviate attributes in expressions with any unique,
13129 multi-character subsequence of
13130 their names (an exact match gets preference).
13131 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13132 in place of @t{a'length}.
13135 @cindex quoting Ada internal identifiers
13136 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13137 to lower case. The GNAT compiler uses upper-case characters for
13138 some of its internal identifiers, which are normally of no interest to users.
13139 For the rare occasions when you actually have to look at them,
13140 enclose them in angle brackets to avoid the lower-case mapping.
13143 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13147 Printing an object of class-wide type or dereferencing an
13148 access-to-class-wide value will display all the components of the object's
13149 specific type (as indicated by its run-time tag). Likewise, component
13150 selection on such a value will operate on the specific type of the
13155 @node Stopping Before Main Program
13156 @subsubsection Stopping at the Very Beginning
13158 @cindex breakpointing Ada elaboration code
13159 It is sometimes necessary to debug the program during elaboration, and
13160 before reaching the main procedure.
13161 As defined in the Ada Reference
13162 Manual, the elaboration code is invoked from a procedure called
13163 @code{adainit}. To run your program up to the beginning of
13164 elaboration, simply use the following two commands:
13165 @code{tbreak adainit} and @code{run}.
13168 @subsubsection Extensions for Ada Tasks
13169 @cindex Ada, tasking
13171 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13172 @value{GDBN} provides the following task-related commands:
13177 This command shows a list of current Ada tasks, as in the following example:
13184 (@value{GDBP}) info tasks
13185 ID TID P-ID Pri State Name
13186 1 8088000 0 15 Child Activation Wait main_task
13187 2 80a4000 1 15 Accept Statement b
13188 3 809a800 1 15 Child Activation Wait a
13189 * 4 80ae800 3 15 Runnable c
13194 In this listing, the asterisk before the last task indicates it to be the
13195 task currently being inspected.
13199 Represents @value{GDBN}'s internal task number.
13205 The parent's task ID (@value{GDBN}'s internal task number).
13208 The base priority of the task.
13211 Current state of the task.
13215 The task has been created but has not been activated. It cannot be
13219 The task is not blocked for any reason known to Ada. (It may be waiting
13220 for a mutex, though.) It is conceptually "executing" in normal mode.
13223 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13224 that were waiting on terminate alternatives have been awakened and have
13225 terminated themselves.
13227 @item Child Activation Wait
13228 The task is waiting for created tasks to complete activation.
13230 @item Accept Statement
13231 The task is waiting on an accept or selective wait statement.
13233 @item Waiting on entry call
13234 The task is waiting on an entry call.
13236 @item Async Select Wait
13237 The task is waiting to start the abortable part of an asynchronous
13241 The task is waiting on a select statement with only a delay
13244 @item Child Termination Wait
13245 The task is sleeping having completed a master within itself, and is
13246 waiting for the tasks dependent on that master to become terminated or
13247 waiting on a terminate Phase.
13249 @item Wait Child in Term Alt
13250 The task is sleeping waiting for tasks on terminate alternatives to
13251 finish terminating.
13253 @item Accepting RV with @var{taskno}
13254 The task is accepting a rendez-vous with the task @var{taskno}.
13258 Name of the task in the program.
13262 @kindex info task @var{taskno}
13263 @item info task @var{taskno}
13264 This command shows detailled informations on the specified task, as in
13265 the following example:
13270 (@value{GDBP}) info tasks
13271 ID TID P-ID Pri State Name
13272 1 8077880 0 15 Child Activation Wait main_task
13273 * 2 807c468 1 15 Runnable task_1
13274 (@value{GDBP}) info task 2
13275 Ada Task: 0x807c468
13278 Parent: 1 (main_task)
13284 @kindex task@r{ (Ada)}
13285 @cindex current Ada task ID
13286 This command prints the ID of the current task.
13292 (@value{GDBP}) info tasks
13293 ID TID P-ID Pri State Name
13294 1 8077870 0 15 Child Activation Wait main_task
13295 * 2 807c458 1 15 Runnable t
13296 (@value{GDBP}) task
13297 [Current task is 2]
13300 @item task @var{taskno}
13301 @cindex Ada task switching
13302 This command is like the @code{thread @var{threadno}}
13303 command (@pxref{Threads}). It switches the context of debugging
13304 from the current task to the given task.
13310 (@value{GDBP}) info tasks
13311 ID TID P-ID Pri State Name
13312 1 8077870 0 15 Child Activation Wait main_task
13313 * 2 807c458 1 15 Runnable t
13314 (@value{GDBP}) task 1
13315 [Switching to task 1]
13316 #0 0x8067726 in pthread_cond_wait ()
13318 #0 0x8067726 in pthread_cond_wait ()
13319 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13320 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13321 #3 0x806153e in system.tasking.stages.activate_tasks ()
13322 #4 0x804aacc in un () at un.adb:5
13325 @item break @var{linespec} task @var{taskno}
13326 @itemx break @var{linespec} task @var{taskno} if @dots{}
13327 @cindex breakpoints and tasks, in Ada
13328 @cindex task breakpoints, in Ada
13329 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13330 These commands are like the @code{break @dots{} thread @dots{}}
13331 command (@pxref{Thread Stops}).
13332 @var{linespec} specifies source lines, as described
13333 in @ref{Specify Location}.
13335 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13336 to specify that you only want @value{GDBN} to stop the program when a
13337 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13338 numeric task identifiers assigned by @value{GDBN}, shown in the first
13339 column of the @samp{info tasks} display.
13341 If you do not specify @samp{task @var{taskno}} when you set a
13342 breakpoint, the breakpoint applies to @emph{all} tasks of your
13345 You can use the @code{task} qualifier on conditional breakpoints as
13346 well; in this case, place @samp{task @var{taskno}} before the
13347 breakpoint condition (before the @code{if}).
13355 (@value{GDBP}) info tasks
13356 ID TID P-ID Pri State Name
13357 1 140022020 0 15 Child Activation Wait main_task
13358 2 140045060 1 15 Accept/Select Wait t2
13359 3 140044840 1 15 Runnable t1
13360 * 4 140056040 1 15 Runnable t3
13361 (@value{GDBP}) b 15 task 2
13362 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13363 (@value{GDBP}) cont
13368 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13370 (@value{GDBP}) info tasks
13371 ID TID P-ID Pri State Name
13372 1 140022020 0 15 Child Activation Wait main_task
13373 * 2 140045060 1 15 Runnable t2
13374 3 140044840 1 15 Runnable t1
13375 4 140056040 1 15 Delay Sleep t3
13379 @node Ada Tasks and Core Files
13380 @subsubsection Tasking Support when Debugging Core Files
13381 @cindex Ada tasking and core file debugging
13383 When inspecting a core file, as opposed to debugging a live program,
13384 tasking support may be limited or even unavailable, depending on
13385 the platform being used.
13386 For instance, on x86-linux, the list of tasks is available, but task
13387 switching is not supported. On Tru64, however, task switching will work
13390 On certain platforms, including Tru64, the debugger needs to perform some
13391 memory writes in order to provide Ada tasking support. When inspecting
13392 a core file, this means that the core file must be opened with read-write
13393 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13394 Under these circumstances, you should make a backup copy of the core
13395 file before inspecting it with @value{GDBN}.
13398 @subsubsection Known Peculiarities of Ada Mode
13399 @cindex Ada, problems
13401 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13402 we know of several problems with and limitations of Ada mode in
13404 some of which will be fixed with planned future releases of the debugger
13405 and the GNU Ada compiler.
13409 Currently, the debugger
13410 has insufficient information to determine whether certain pointers represent
13411 pointers to objects or the objects themselves.
13412 Thus, the user may have to tack an extra @code{.all} after an expression
13413 to get it printed properly.
13416 Static constants that the compiler chooses not to materialize as objects in
13417 storage are invisible to the debugger.
13420 Named parameter associations in function argument lists are ignored (the
13421 argument lists are treated as positional).
13424 Many useful library packages are currently invisible to the debugger.
13427 Fixed-point arithmetic, conversions, input, and output is carried out using
13428 floating-point arithmetic, and may give results that only approximate those on
13432 The GNAT compiler never generates the prefix @code{Standard} for any of
13433 the standard symbols defined by the Ada language. @value{GDBN} knows about
13434 this: it will strip the prefix from names when you use it, and will never
13435 look for a name you have so qualified among local symbols, nor match against
13436 symbols in other packages or subprograms. If you have
13437 defined entities anywhere in your program other than parameters and
13438 local variables whose simple names match names in @code{Standard},
13439 GNAT's lack of qualification here can cause confusion. When this happens,
13440 you can usually resolve the confusion
13441 by qualifying the problematic names with package
13442 @code{Standard} explicitly.
13445 Older versions of the compiler sometimes generate erroneous debugging
13446 information, resulting in the debugger incorrectly printing the value
13447 of affected entities. In some cases, the debugger is able to work
13448 around an issue automatically. In other cases, the debugger is able
13449 to work around the issue, but the work-around has to be specifically
13452 @kindex set ada trust-PAD-over-XVS
13453 @kindex show ada trust-PAD-over-XVS
13456 @item set ada trust-PAD-over-XVS on
13457 Configure GDB to strictly follow the GNAT encoding when computing the
13458 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13459 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13460 a complete description of the encoding used by the GNAT compiler).
13461 This is the default.
13463 @item set ada trust-PAD-over-XVS off
13464 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13465 sometimes prints the wrong value for certain entities, changing @code{ada
13466 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13467 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13468 @code{off}, but this incurs a slight performance penalty, so it is
13469 recommended to leave this setting to @code{on} unless necessary.
13473 @node Unsupported Languages
13474 @section Unsupported Languages
13476 @cindex unsupported languages
13477 @cindex minimal language
13478 In addition to the other fully-supported programming languages,
13479 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13480 It does not represent a real programming language, but provides a set
13481 of capabilities close to what the C or assembly languages provide.
13482 This should allow most simple operations to be performed while debugging
13483 an application that uses a language currently not supported by @value{GDBN}.
13485 If the language is set to @code{auto}, @value{GDBN} will automatically
13486 select this language if the current frame corresponds to an unsupported
13490 @chapter Examining the Symbol Table
13492 The commands described in this chapter allow you to inquire about the
13493 symbols (names of variables, functions and types) defined in your
13494 program. This information is inherent in the text of your program and
13495 does not change as your program executes. @value{GDBN} finds it in your
13496 program's symbol table, in the file indicated when you started @value{GDBN}
13497 (@pxref{File Options, ,Choosing Files}), or by one of the
13498 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13500 @cindex symbol names
13501 @cindex names of symbols
13502 @cindex quoting names
13503 Occasionally, you may need to refer to symbols that contain unusual
13504 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13505 most frequent case is in referring to static variables in other
13506 source files (@pxref{Variables,,Program Variables}). File names
13507 are recorded in object files as debugging symbols, but @value{GDBN} would
13508 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13509 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13510 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13517 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13520 @cindex case-insensitive symbol names
13521 @cindex case sensitivity in symbol names
13522 @kindex set case-sensitive
13523 @item set case-sensitive on
13524 @itemx set case-sensitive off
13525 @itemx set case-sensitive auto
13526 Normally, when @value{GDBN} looks up symbols, it matches their names
13527 with case sensitivity determined by the current source language.
13528 Occasionally, you may wish to control that. The command @code{set
13529 case-sensitive} lets you do that by specifying @code{on} for
13530 case-sensitive matches or @code{off} for case-insensitive ones. If
13531 you specify @code{auto}, case sensitivity is reset to the default
13532 suitable for the source language. The default is case-sensitive
13533 matches for all languages except for Fortran, for which the default is
13534 case-insensitive matches.
13536 @kindex show case-sensitive
13537 @item show case-sensitive
13538 This command shows the current setting of case sensitivity for symbols
13541 @kindex info address
13542 @cindex address of a symbol
13543 @item info address @var{symbol}
13544 Describe where the data for @var{symbol} is stored. For a register
13545 variable, this says which register it is kept in. For a non-register
13546 local variable, this prints the stack-frame offset at which the variable
13549 Note the contrast with @samp{print &@var{symbol}}, which does not work
13550 at all for a register variable, and for a stack local variable prints
13551 the exact address of the current instantiation of the variable.
13553 @kindex info symbol
13554 @cindex symbol from address
13555 @cindex closest symbol and offset for an address
13556 @item info symbol @var{addr}
13557 Print the name of a symbol which is stored at the address @var{addr}.
13558 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13559 nearest symbol and an offset from it:
13562 (@value{GDBP}) info symbol 0x54320
13563 _initialize_vx + 396 in section .text
13567 This is the opposite of the @code{info address} command. You can use
13568 it to find out the name of a variable or a function given its address.
13570 For dynamically linked executables, the name of executable or shared
13571 library containing the symbol is also printed:
13574 (@value{GDBP}) info symbol 0x400225
13575 _start + 5 in section .text of /tmp/a.out
13576 (@value{GDBP}) info symbol 0x2aaaac2811cf
13577 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13581 @item whatis [@var{arg}]
13582 Print the data type of @var{arg}, which can be either an expression or
13583 a data type. With no argument, print the data type of @code{$}, the
13584 last value in the value history. If @var{arg} is an expression, it is
13585 not actually evaluated, and any side-effecting operations (such as
13586 assignments or function calls) inside it do not take place. If
13587 @var{arg} is a type name, it may be the name of a type or typedef, or
13588 for C code it may have the form @samp{class @var{class-name}},
13589 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13590 @samp{enum @var{enum-tag}}.
13591 @xref{Expressions, ,Expressions}.
13594 @item ptype [@var{arg}]
13595 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13596 detailed description of the type, instead of just the name of the type.
13597 @xref{Expressions, ,Expressions}.
13599 For example, for this variable declaration:
13602 struct complex @{double real; double imag;@} v;
13606 the two commands give this output:
13610 (@value{GDBP}) whatis v
13611 type = struct complex
13612 (@value{GDBP}) ptype v
13613 type = struct complex @{
13621 As with @code{whatis}, using @code{ptype} without an argument refers to
13622 the type of @code{$}, the last value in the value history.
13624 @cindex incomplete type
13625 Sometimes, programs use opaque data types or incomplete specifications
13626 of complex data structure. If the debug information included in the
13627 program does not allow @value{GDBN} to display a full declaration of
13628 the data type, it will say @samp{<incomplete type>}. For example,
13629 given these declarations:
13633 struct foo *fooptr;
13637 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13640 (@value{GDBP}) ptype foo
13641 $1 = <incomplete type>
13645 ``Incomplete type'' is C terminology for data types that are not
13646 completely specified.
13649 @item info types @var{regexp}
13651 Print a brief description of all types whose names match the regular
13652 expression @var{regexp} (or all types in your program, if you supply
13653 no argument). Each complete typename is matched as though it were a
13654 complete line; thus, @samp{i type value} gives information on all
13655 types in your program whose names include the string @code{value}, but
13656 @samp{i type ^value$} gives information only on types whose complete
13657 name is @code{value}.
13659 This command differs from @code{ptype} in two ways: first, like
13660 @code{whatis}, it does not print a detailed description; second, it
13661 lists all source files where a type is defined.
13664 @cindex local variables
13665 @item info scope @var{location}
13666 List all the variables local to a particular scope. This command
13667 accepts a @var{location} argument---a function name, a source line, or
13668 an address preceded by a @samp{*}, and prints all the variables local
13669 to the scope defined by that location. (@xref{Specify Location}, for
13670 details about supported forms of @var{location}.) For example:
13673 (@value{GDBP}) @b{info scope command_line_handler}
13674 Scope for command_line_handler:
13675 Symbol rl is an argument at stack/frame offset 8, length 4.
13676 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13677 Symbol linelength is in static storage at address 0x150a1c, length 4.
13678 Symbol p is a local variable in register $esi, length 4.
13679 Symbol p1 is a local variable in register $ebx, length 4.
13680 Symbol nline is a local variable in register $edx, length 4.
13681 Symbol repeat is a local variable at frame offset -8, length 4.
13685 This command is especially useful for determining what data to collect
13686 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13689 @kindex info source
13691 Show information about the current source file---that is, the source file for
13692 the function containing the current point of execution:
13695 the name of the source file, and the directory containing it,
13697 the directory it was compiled in,
13699 its length, in lines,
13701 which programming language it is written in,
13703 whether the executable includes debugging information for that file, and
13704 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13706 whether the debugging information includes information about
13707 preprocessor macros.
13711 @kindex info sources
13713 Print the names of all source files in your program for which there is
13714 debugging information, organized into two lists: files whose symbols
13715 have already been read, and files whose symbols will be read when needed.
13717 @kindex info functions
13718 @item info functions
13719 Print the names and data types of all defined functions.
13721 @item info functions @var{regexp}
13722 Print the names and data types of all defined functions
13723 whose names contain a match for regular expression @var{regexp}.
13724 Thus, @samp{info fun step} finds all functions whose names
13725 include @code{step}; @samp{info fun ^step} finds those whose names
13726 start with @code{step}. If a function name contains characters
13727 that conflict with the regular expression language (e.g.@:
13728 @samp{operator*()}), they may be quoted with a backslash.
13730 @kindex info variables
13731 @item info variables
13732 Print the names and data types of all variables that are defined
13733 outside of functions (i.e.@: excluding local variables).
13735 @item info variables @var{regexp}
13736 Print the names and data types of all variables (except for local
13737 variables) whose names contain a match for regular expression
13740 @kindex info classes
13741 @cindex Objective-C, classes and selectors
13743 @itemx info classes @var{regexp}
13744 Display all Objective-C classes in your program, or
13745 (with the @var{regexp} argument) all those matching a particular regular
13748 @kindex info selectors
13749 @item info selectors
13750 @itemx info selectors @var{regexp}
13751 Display all Objective-C selectors in your program, or
13752 (with the @var{regexp} argument) all those matching a particular regular
13756 This was never implemented.
13757 @kindex info methods
13759 @itemx info methods @var{regexp}
13760 The @code{info methods} command permits the user to examine all defined
13761 methods within C@t{++} program, or (with the @var{regexp} argument) a
13762 specific set of methods found in the various C@t{++} classes. Many
13763 C@t{++} classes provide a large number of methods. Thus, the output
13764 from the @code{ptype} command can be overwhelming and hard to use. The
13765 @code{info-methods} command filters the methods, printing only those
13766 which match the regular-expression @var{regexp}.
13769 @cindex reloading symbols
13770 Some systems allow individual object files that make up your program to
13771 be replaced without stopping and restarting your program. For example,
13772 in VxWorks you can simply recompile a defective object file and keep on
13773 running. If you are running on one of these systems, you can allow
13774 @value{GDBN} to reload the symbols for automatically relinked modules:
13777 @kindex set symbol-reloading
13778 @item set symbol-reloading on
13779 Replace symbol definitions for the corresponding source file when an
13780 object file with a particular name is seen again.
13782 @item set symbol-reloading off
13783 Do not replace symbol definitions when encountering object files of the
13784 same name more than once. This is the default state; if you are not
13785 running on a system that permits automatic relinking of modules, you
13786 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
13787 may discard symbols when linking large programs, that may contain
13788 several modules (from different directories or libraries) with the same
13791 @kindex show symbol-reloading
13792 @item show symbol-reloading
13793 Show the current @code{on} or @code{off} setting.
13796 @cindex opaque data types
13797 @kindex set opaque-type-resolution
13798 @item set opaque-type-resolution on
13799 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
13800 declared as a pointer to a @code{struct}, @code{class}, or
13801 @code{union}---for example, @code{struct MyType *}---that is used in one
13802 source file although the full declaration of @code{struct MyType} is in
13803 another source file. The default is on.
13805 A change in the setting of this subcommand will not take effect until
13806 the next time symbols for a file are loaded.
13808 @item set opaque-type-resolution off
13809 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13810 is printed as follows:
13812 @{<no data fields>@}
13815 @kindex show opaque-type-resolution
13816 @item show opaque-type-resolution
13817 Show whether opaque types are resolved or not.
13819 @kindex maint print symbols
13820 @cindex symbol dump
13821 @kindex maint print psymbols
13822 @cindex partial symbol dump
13823 @item maint print symbols @var{filename}
13824 @itemx maint print psymbols @var{filename}
13825 @itemx maint print msymbols @var{filename}
13826 Write a dump of debugging symbol data into the file @var{filename}.
13827 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13828 symbols with debugging data are included. If you use @samp{maint print
13829 symbols}, @value{GDBN} includes all the symbols for which it has already
13830 collected full details: that is, @var{filename} reflects symbols for
13831 only those files whose symbols @value{GDBN} has read. You can use the
13832 command @code{info sources} to find out which files these are. If you
13833 use @samp{maint print psymbols} instead, the dump shows information about
13834 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13835 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13836 @samp{maint print msymbols} dumps just the minimal symbol information
13837 required for each object file from which @value{GDBN} has read some symbols.
13838 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13839 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13841 @kindex maint info symtabs
13842 @kindex maint info psymtabs
13843 @cindex listing @value{GDBN}'s internal symbol tables
13844 @cindex symbol tables, listing @value{GDBN}'s internal
13845 @cindex full symbol tables, listing @value{GDBN}'s internal
13846 @cindex partial symbol tables, listing @value{GDBN}'s internal
13847 @item maint info symtabs @r{[} @var{regexp} @r{]}
13848 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13850 List the @code{struct symtab} or @code{struct partial_symtab}
13851 structures whose names match @var{regexp}. If @var{regexp} is not
13852 given, list them all. The output includes expressions which you can
13853 copy into a @value{GDBN} debugging this one to examine a particular
13854 structure in more detail. For example:
13857 (@value{GDBP}) maint info psymtabs dwarf2read
13858 @{ objfile /home/gnu/build/gdb/gdb
13859 ((struct objfile *) 0x82e69d0)
13860 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13861 ((struct partial_symtab *) 0x8474b10)
13864 text addresses 0x814d3c8 -- 0x8158074
13865 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13866 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13867 dependencies (none)
13870 (@value{GDBP}) maint info symtabs
13874 We see that there is one partial symbol table whose filename contains
13875 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13876 and we see that @value{GDBN} has not read in any symtabs yet at all.
13877 If we set a breakpoint on a function, that will cause @value{GDBN} to
13878 read the symtab for the compilation unit containing that function:
13881 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13882 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13884 (@value{GDBP}) maint info symtabs
13885 @{ objfile /home/gnu/build/gdb/gdb
13886 ((struct objfile *) 0x82e69d0)
13887 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13888 ((struct symtab *) 0x86c1f38)
13891 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13892 linetable ((struct linetable *) 0x8370fa0)
13893 debugformat DWARF 2
13902 @chapter Altering Execution
13904 Once you think you have found an error in your program, you might want to
13905 find out for certain whether correcting the apparent error would lead to
13906 correct results in the rest of the run. You can find the answer by
13907 experiment, using the @value{GDBN} features for altering execution of the
13910 For example, you can store new values into variables or memory
13911 locations, give your program a signal, restart it at a different
13912 address, or even return prematurely from a function.
13915 * Assignment:: Assignment to variables
13916 * Jumping:: Continuing at a different address
13917 * Signaling:: Giving your program a signal
13918 * Returning:: Returning from a function
13919 * Calling:: Calling your program's functions
13920 * Patching:: Patching your program
13924 @section Assignment to Variables
13927 @cindex setting variables
13928 To alter the value of a variable, evaluate an assignment expression.
13929 @xref{Expressions, ,Expressions}. For example,
13936 stores the value 4 into the variable @code{x}, and then prints the
13937 value of the assignment expression (which is 4).
13938 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13939 information on operators in supported languages.
13941 @kindex set variable
13942 @cindex variables, setting
13943 If you are not interested in seeing the value of the assignment, use the
13944 @code{set} command instead of the @code{print} command. @code{set} is
13945 really the same as @code{print} except that the expression's value is
13946 not printed and is not put in the value history (@pxref{Value History,
13947 ,Value History}). The expression is evaluated only for its effects.
13949 If the beginning of the argument string of the @code{set} command
13950 appears identical to a @code{set} subcommand, use the @code{set
13951 variable} command instead of just @code{set}. This command is identical
13952 to @code{set} except for its lack of subcommands. For example, if your
13953 program has a variable @code{width}, you get an error if you try to set
13954 a new value with just @samp{set width=13}, because @value{GDBN} has the
13955 command @code{set width}:
13958 (@value{GDBP}) whatis width
13960 (@value{GDBP}) p width
13962 (@value{GDBP}) set width=47
13963 Invalid syntax in expression.
13967 The invalid expression, of course, is @samp{=47}. In
13968 order to actually set the program's variable @code{width}, use
13971 (@value{GDBP}) set var width=47
13974 Because the @code{set} command has many subcommands that can conflict
13975 with the names of program variables, it is a good idea to use the
13976 @code{set variable} command instead of just @code{set}. For example, if
13977 your program has a variable @code{g}, you run into problems if you try
13978 to set a new value with just @samp{set g=4}, because @value{GDBN} has
13979 the command @code{set gnutarget}, abbreviated @code{set g}:
13983 (@value{GDBP}) whatis g
13987 (@value{GDBP}) set g=4
13991 The program being debugged has been started already.
13992 Start it from the beginning? (y or n) y
13993 Starting program: /home/smith/cc_progs/a.out
13994 "/home/smith/cc_progs/a.out": can't open to read symbols:
13995 Invalid bfd target.
13996 (@value{GDBP}) show g
13997 The current BFD target is "=4".
14002 The program variable @code{g} did not change, and you silently set the
14003 @code{gnutarget} to an invalid value. In order to set the variable
14007 (@value{GDBP}) set var g=4
14010 @value{GDBN} allows more implicit conversions in assignments than C; you can
14011 freely store an integer value into a pointer variable or vice versa,
14012 and you can convert any structure to any other structure that is the
14013 same length or shorter.
14014 @comment FIXME: how do structs align/pad in these conversions?
14015 @comment /doc@cygnus.com 18dec1990
14017 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14018 construct to generate a value of specified type at a specified address
14019 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14020 to memory location @code{0x83040} as an integer (which implies a certain size
14021 and representation in memory), and
14024 set @{int@}0x83040 = 4
14028 stores the value 4 into that memory location.
14031 @section Continuing at a Different Address
14033 Ordinarily, when you continue your program, you do so at the place where
14034 it stopped, with the @code{continue} command. You can instead continue at
14035 an address of your own choosing, with the following commands:
14039 @item jump @var{linespec}
14040 @itemx jump @var{location}
14041 Resume execution at line @var{linespec} or at address given by
14042 @var{location}. Execution stops again immediately if there is a
14043 breakpoint there. @xref{Specify Location}, for a description of the
14044 different forms of @var{linespec} and @var{location}. It is common
14045 practice to use the @code{tbreak} command in conjunction with
14046 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14048 The @code{jump} command does not change the current stack frame, or
14049 the stack pointer, or the contents of any memory location or any
14050 register other than the program counter. If line @var{linespec} is in
14051 a different function from the one currently executing, the results may
14052 be bizarre if the two functions expect different patterns of arguments or
14053 of local variables. For this reason, the @code{jump} command requests
14054 confirmation if the specified line is not in the function currently
14055 executing. However, even bizarre results are predictable if you are
14056 well acquainted with the machine-language code of your program.
14059 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14060 On many systems, you can get much the same effect as the @code{jump}
14061 command by storing a new value into the register @code{$pc}. The
14062 difference is that this does not start your program running; it only
14063 changes the address of where it @emph{will} run when you continue. For
14071 makes the next @code{continue} command or stepping command execute at
14072 address @code{0x485}, rather than at the address where your program stopped.
14073 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14075 The most common occasion to use the @code{jump} command is to back
14076 up---perhaps with more breakpoints set---over a portion of a program
14077 that has already executed, in order to examine its execution in more
14082 @section Giving your Program a Signal
14083 @cindex deliver a signal to a program
14087 @item signal @var{signal}
14088 Resume execution where your program stopped, but immediately give it the
14089 signal @var{signal}. @var{signal} can be the name or the number of a
14090 signal. For example, on many systems @code{signal 2} and @code{signal
14091 SIGINT} are both ways of sending an interrupt signal.
14093 Alternatively, if @var{signal} is zero, continue execution without
14094 giving a signal. This is useful when your program stopped on account of
14095 a signal and would ordinary see the signal when resumed with the
14096 @code{continue} command; @samp{signal 0} causes it to resume without a
14099 @code{signal} does not repeat when you press @key{RET} a second time
14100 after executing the command.
14104 Invoking the @code{signal} command is not the same as invoking the
14105 @code{kill} utility from the shell. Sending a signal with @code{kill}
14106 causes @value{GDBN} to decide what to do with the signal depending on
14107 the signal handling tables (@pxref{Signals}). The @code{signal} command
14108 passes the signal directly to your program.
14112 @section Returning from a Function
14115 @cindex returning from a function
14118 @itemx return @var{expression}
14119 You can cancel execution of a function call with the @code{return}
14120 command. If you give an
14121 @var{expression} argument, its value is used as the function's return
14125 When you use @code{return}, @value{GDBN} discards the selected stack frame
14126 (and all frames within it). You can think of this as making the
14127 discarded frame return prematurely. If you wish to specify a value to
14128 be returned, give that value as the argument to @code{return}.
14130 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14131 Frame}), and any other frames inside of it, leaving its caller as the
14132 innermost remaining frame. That frame becomes selected. The
14133 specified value is stored in the registers used for returning values
14136 The @code{return} command does not resume execution; it leaves the
14137 program stopped in the state that would exist if the function had just
14138 returned. In contrast, the @code{finish} command (@pxref{Continuing
14139 and Stepping, ,Continuing and Stepping}) resumes execution until the
14140 selected stack frame returns naturally.
14142 @value{GDBN} needs to know how the @var{expression} argument should be set for
14143 the inferior. The concrete registers assignment depends on the OS ABI and the
14144 type being returned by the selected stack frame. For example it is common for
14145 OS ABI to return floating point values in FPU registers while integer values in
14146 CPU registers. Still some ABIs return even floating point values in CPU
14147 registers. Larger integer widths (such as @code{long long int}) also have
14148 specific placement rules. @value{GDBN} already knows the OS ABI from its
14149 current target so it needs to find out also the type being returned to make the
14150 assignment into the right register(s).
14152 Normally, the selected stack frame has debug info. @value{GDBN} will always
14153 use the debug info instead of the implicit type of @var{expression} when the
14154 debug info is available. For example, if you type @kbd{return -1}, and the
14155 function in the current stack frame is declared to return a @code{long long
14156 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14157 into a @code{long long int}:
14160 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14162 (@value{GDBP}) return -1
14163 Make func return now? (y or n) y
14164 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14165 43 printf ("result=%lld\n", func ());
14169 However, if the selected stack frame does not have a debug info, e.g., if the
14170 function was compiled without debug info, @value{GDBN} has to find out the type
14171 to return from user. Specifying a different type by mistake may set the value
14172 in different inferior registers than the caller code expects. For example,
14173 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14174 of a @code{long long int} result for a debug info less function (on 32-bit
14175 architectures). Therefore the user is required to specify the return type by
14176 an appropriate cast explicitly:
14179 Breakpoint 2, 0x0040050b in func ()
14180 (@value{GDBP}) return -1
14181 Return value type not available for selected stack frame.
14182 Please use an explicit cast of the value to return.
14183 (@value{GDBP}) return (long long int) -1
14184 Make selected stack frame return now? (y or n) y
14185 #0 0x00400526 in main ()
14190 @section Calling Program Functions
14193 @cindex calling functions
14194 @cindex inferior functions, calling
14195 @item print @var{expr}
14196 Evaluate the expression @var{expr} and display the resulting value.
14197 @var{expr} may include calls to functions in the program being
14201 @item call @var{expr}
14202 Evaluate the expression @var{expr} without displaying @code{void}
14205 You can use this variant of the @code{print} command if you want to
14206 execute a function from your program that does not return anything
14207 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14208 with @code{void} returned values that @value{GDBN} will otherwise
14209 print. If the result is not void, it is printed and saved in the
14213 It is possible for the function you call via the @code{print} or
14214 @code{call} command to generate a signal (e.g., if there's a bug in
14215 the function, or if you passed it incorrect arguments). What happens
14216 in that case is controlled by the @code{set unwindonsignal} command.
14218 Similarly, with a C@t{++} program it is possible for the function you
14219 call via the @code{print} or @code{call} command to generate an
14220 exception that is not handled due to the constraints of the dummy
14221 frame. In this case, any exception that is raised in the frame, but has
14222 an out-of-frame exception handler will not be found. GDB builds a
14223 dummy-frame for the inferior function call, and the unwinder cannot
14224 seek for exception handlers outside of this dummy-frame. What happens
14225 in that case is controlled by the
14226 @code{set unwind-on-terminating-exception} command.
14229 @item set unwindonsignal
14230 @kindex set unwindonsignal
14231 @cindex unwind stack in called functions
14232 @cindex call dummy stack unwinding
14233 Set unwinding of the stack if a signal is received while in a function
14234 that @value{GDBN} called in the program being debugged. If set to on,
14235 @value{GDBN} unwinds the stack it created for the call and restores
14236 the context to what it was before the call. If set to off (the
14237 default), @value{GDBN} stops in the frame where the signal was
14240 @item show unwindonsignal
14241 @kindex show unwindonsignal
14242 Show the current setting of stack unwinding in the functions called by
14245 @item set unwind-on-terminating-exception
14246 @kindex set unwind-on-terminating-exception
14247 @cindex unwind stack in called functions with unhandled exceptions
14248 @cindex call dummy stack unwinding on unhandled exception.
14249 Set unwinding of the stack if a C@t{++} exception is raised, but left
14250 unhandled while in a function that @value{GDBN} called in the program being
14251 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14252 it created for the call and restores the context to what it was before
14253 the call. If set to off, @value{GDBN} the exception is delivered to
14254 the default C@t{++} exception handler and the inferior terminated.
14256 @item show unwind-on-terminating-exception
14257 @kindex show unwind-on-terminating-exception
14258 Show the current setting of stack unwinding in the functions called by
14263 @cindex weak alias functions
14264 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14265 for another function. In such case, @value{GDBN} might not pick up
14266 the type information, including the types of the function arguments,
14267 which causes @value{GDBN} to call the inferior function incorrectly.
14268 As a result, the called function will function erroneously and may
14269 even crash. A solution to that is to use the name of the aliased
14273 @section Patching Programs
14275 @cindex patching binaries
14276 @cindex writing into executables
14277 @cindex writing into corefiles
14279 By default, @value{GDBN} opens the file containing your program's
14280 executable code (or the corefile) read-only. This prevents accidental
14281 alterations to machine code; but it also prevents you from intentionally
14282 patching your program's binary.
14284 If you'd like to be able to patch the binary, you can specify that
14285 explicitly with the @code{set write} command. For example, you might
14286 want to turn on internal debugging flags, or even to make emergency
14292 @itemx set write off
14293 If you specify @samp{set write on}, @value{GDBN} opens executable and
14294 core files for both reading and writing; if you specify @kbd{set write
14295 off} (the default), @value{GDBN} opens them read-only.
14297 If you have already loaded a file, you must load it again (using the
14298 @code{exec-file} or @code{core-file} command) after changing @code{set
14299 write}, for your new setting to take effect.
14303 Display whether executable files and core files are opened for writing
14304 as well as reading.
14308 @chapter @value{GDBN} Files
14310 @value{GDBN} needs to know the file name of the program to be debugged,
14311 both in order to read its symbol table and in order to start your
14312 program. To debug a core dump of a previous run, you must also tell
14313 @value{GDBN} the name of the core dump file.
14316 * Files:: Commands to specify files
14317 * Separate Debug Files:: Debugging information in separate files
14318 * Index Files:: Index files speed up GDB
14319 * Symbol Errors:: Errors reading symbol files
14320 * Data Files:: GDB data files
14324 @section Commands to Specify Files
14326 @cindex symbol table
14327 @cindex core dump file
14329 You may want to specify executable and core dump file names. The usual
14330 way to do this is at start-up time, using the arguments to
14331 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14332 Out of @value{GDBN}}).
14334 Occasionally it is necessary to change to a different file during a
14335 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14336 specify a file you want to use. Or you are debugging a remote target
14337 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14338 Program}). In these situations the @value{GDBN} commands to specify
14339 new files are useful.
14342 @cindex executable file
14344 @item file @var{filename}
14345 Use @var{filename} as the program to be debugged. It is read for its
14346 symbols and for the contents of pure memory. It is also the program
14347 executed when you use the @code{run} command. If you do not specify a
14348 directory and the file is not found in the @value{GDBN} working directory,
14349 @value{GDBN} uses the environment variable @code{PATH} as a list of
14350 directories to search, just as the shell does when looking for a program
14351 to run. You can change the value of this variable, for both @value{GDBN}
14352 and your program, using the @code{path} command.
14354 @cindex unlinked object files
14355 @cindex patching object files
14356 You can load unlinked object @file{.o} files into @value{GDBN} using
14357 the @code{file} command. You will not be able to ``run'' an object
14358 file, but you can disassemble functions and inspect variables. Also,
14359 if the underlying BFD functionality supports it, you could use
14360 @kbd{gdb -write} to patch object files using this technique. Note
14361 that @value{GDBN} can neither interpret nor modify relocations in this
14362 case, so branches and some initialized variables will appear to go to
14363 the wrong place. But this feature is still handy from time to time.
14366 @code{file} with no argument makes @value{GDBN} discard any information it
14367 has on both executable file and the symbol table.
14370 @item exec-file @r{[} @var{filename} @r{]}
14371 Specify that the program to be run (but not the symbol table) is found
14372 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14373 if necessary to locate your program. Omitting @var{filename} means to
14374 discard information on the executable file.
14376 @kindex symbol-file
14377 @item symbol-file @r{[} @var{filename} @r{]}
14378 Read symbol table information from file @var{filename}. @code{PATH} is
14379 searched when necessary. Use the @code{file} command to get both symbol
14380 table and program to run from the same file.
14382 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14383 program's symbol table.
14385 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14386 some breakpoints and auto-display expressions. This is because they may
14387 contain pointers to the internal data recording symbols and data types,
14388 which are part of the old symbol table data being discarded inside
14391 @code{symbol-file} does not repeat if you press @key{RET} again after
14394 When @value{GDBN} is configured for a particular environment, it
14395 understands debugging information in whatever format is the standard
14396 generated for that environment; you may use either a @sc{gnu} compiler, or
14397 other compilers that adhere to the local conventions.
14398 Best results are usually obtained from @sc{gnu} compilers; for example,
14399 using @code{@value{NGCC}} you can generate debugging information for
14402 For most kinds of object files, with the exception of old SVR3 systems
14403 using COFF, the @code{symbol-file} command does not normally read the
14404 symbol table in full right away. Instead, it scans the symbol table
14405 quickly to find which source files and which symbols are present. The
14406 details are read later, one source file at a time, as they are needed.
14408 The purpose of this two-stage reading strategy is to make @value{GDBN}
14409 start up faster. For the most part, it is invisible except for
14410 occasional pauses while the symbol table details for a particular source
14411 file are being read. (The @code{set verbose} command can turn these
14412 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14413 Warnings and Messages}.)
14415 We have not implemented the two-stage strategy for COFF yet. When the
14416 symbol table is stored in COFF format, @code{symbol-file} reads the
14417 symbol table data in full right away. Note that ``stabs-in-COFF''
14418 still does the two-stage strategy, since the debug info is actually
14422 @cindex reading symbols immediately
14423 @cindex symbols, reading immediately
14424 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14425 @itemx file @r{[} -readnow @r{]} @var{filename}
14426 You can override the @value{GDBN} two-stage strategy for reading symbol
14427 tables by using the @samp{-readnow} option with any of the commands that
14428 load symbol table information, if you want to be sure @value{GDBN} has the
14429 entire symbol table available.
14431 @c FIXME: for now no mention of directories, since this seems to be in
14432 @c flux. 13mar1992 status is that in theory GDB would look either in
14433 @c current dir or in same dir as myprog; but issues like competing
14434 @c GDB's, or clutter in system dirs, mean that in practice right now
14435 @c only current dir is used. FFish says maybe a special GDB hierarchy
14436 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14440 @item core-file @r{[}@var{filename}@r{]}
14442 Specify the whereabouts of a core dump file to be used as the ``contents
14443 of memory''. Traditionally, core files contain only some parts of the
14444 address space of the process that generated them; @value{GDBN} can access the
14445 executable file itself for other parts.
14447 @code{core-file} with no argument specifies that no core file is
14450 Note that the core file is ignored when your program is actually running
14451 under @value{GDBN}. So, if you have been running your program and you
14452 wish to debug a core file instead, you must kill the subprocess in which
14453 the program is running. To do this, use the @code{kill} command
14454 (@pxref{Kill Process, ,Killing the Child Process}).
14456 @kindex add-symbol-file
14457 @cindex dynamic linking
14458 @item add-symbol-file @var{filename} @var{address}
14459 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14460 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14461 The @code{add-symbol-file} command reads additional symbol table
14462 information from the file @var{filename}. You would use this command
14463 when @var{filename} has been dynamically loaded (by some other means)
14464 into the program that is running. @var{address} should be the memory
14465 address at which the file has been loaded; @value{GDBN} cannot figure
14466 this out for itself. You can additionally specify an arbitrary number
14467 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14468 section name and base address for that section. You can specify any
14469 @var{address} as an expression.
14471 The symbol table of the file @var{filename} is added to the symbol table
14472 originally read with the @code{symbol-file} command. You can use the
14473 @code{add-symbol-file} command any number of times; the new symbol data
14474 thus read keeps adding to the old. To discard all old symbol data
14475 instead, use the @code{symbol-file} command without any arguments.
14477 @cindex relocatable object files, reading symbols from
14478 @cindex object files, relocatable, reading symbols from
14479 @cindex reading symbols from relocatable object files
14480 @cindex symbols, reading from relocatable object files
14481 @cindex @file{.o} files, reading symbols from
14482 Although @var{filename} is typically a shared library file, an
14483 executable file, or some other object file which has been fully
14484 relocated for loading into a process, you can also load symbolic
14485 information from relocatable @file{.o} files, as long as:
14489 the file's symbolic information refers only to linker symbols defined in
14490 that file, not to symbols defined by other object files,
14492 every section the file's symbolic information refers to has actually
14493 been loaded into the inferior, as it appears in the file, and
14495 you can determine the address at which every section was loaded, and
14496 provide these to the @code{add-symbol-file} command.
14500 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14501 relocatable files into an already running program; such systems
14502 typically make the requirements above easy to meet. However, it's
14503 important to recognize that many native systems use complex link
14504 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14505 assembly, for example) that make the requirements difficult to meet. In
14506 general, one cannot assume that using @code{add-symbol-file} to read a
14507 relocatable object file's symbolic information will have the same effect
14508 as linking the relocatable object file into the program in the normal
14511 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14513 @kindex add-symbol-file-from-memory
14514 @cindex @code{syscall DSO}
14515 @cindex load symbols from memory
14516 @item add-symbol-file-from-memory @var{address}
14517 Load symbols from the given @var{address} in a dynamically loaded
14518 object file whose image is mapped directly into the inferior's memory.
14519 For example, the Linux kernel maps a @code{syscall DSO} into each
14520 process's address space; this DSO provides kernel-specific code for
14521 some system calls. The argument can be any expression whose
14522 evaluation yields the address of the file's shared object file header.
14523 For this command to work, you must have used @code{symbol-file} or
14524 @code{exec-file} commands in advance.
14526 @kindex add-shared-symbol-files
14528 @item add-shared-symbol-files @var{library-file}
14529 @itemx assf @var{library-file}
14530 The @code{add-shared-symbol-files} command can currently be used only
14531 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14532 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14533 @value{GDBN} automatically looks for shared libraries, however if
14534 @value{GDBN} does not find yours, you can invoke
14535 @code{add-shared-symbol-files}. It takes one argument: the shared
14536 library's file name. @code{assf} is a shorthand alias for
14537 @code{add-shared-symbol-files}.
14540 @item section @var{section} @var{addr}
14541 The @code{section} command changes the base address of the named
14542 @var{section} of the exec file to @var{addr}. This can be used if the
14543 exec file does not contain section addresses, (such as in the
14544 @code{a.out} format), or when the addresses specified in the file
14545 itself are wrong. Each section must be changed separately. The
14546 @code{info files} command, described below, lists all the sections and
14550 @kindex info target
14553 @code{info files} and @code{info target} are synonymous; both print the
14554 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14555 including the names of the executable and core dump files currently in
14556 use by @value{GDBN}, and the files from which symbols were loaded. The
14557 command @code{help target} lists all possible targets rather than
14560 @kindex maint info sections
14561 @item maint info sections
14562 Another command that can give you extra information about program sections
14563 is @code{maint info sections}. In addition to the section information
14564 displayed by @code{info files}, this command displays the flags and file
14565 offset of each section in the executable and core dump files. In addition,
14566 @code{maint info sections} provides the following command options (which
14567 may be arbitrarily combined):
14571 Display sections for all loaded object files, including shared libraries.
14572 @item @var{sections}
14573 Display info only for named @var{sections}.
14574 @item @var{section-flags}
14575 Display info only for sections for which @var{section-flags} are true.
14576 The section flags that @value{GDBN} currently knows about are:
14579 Section will have space allocated in the process when loaded.
14580 Set for all sections except those containing debug information.
14582 Section will be loaded from the file into the child process memory.
14583 Set for pre-initialized code and data, clear for @code{.bss} sections.
14585 Section needs to be relocated before loading.
14587 Section cannot be modified by the child process.
14589 Section contains executable code only.
14591 Section contains data only (no executable code).
14593 Section will reside in ROM.
14595 Section contains data for constructor/destructor lists.
14597 Section is not empty.
14599 An instruction to the linker to not output the section.
14600 @item COFF_SHARED_LIBRARY
14601 A notification to the linker that the section contains
14602 COFF shared library information.
14604 Section contains common symbols.
14607 @kindex set trust-readonly-sections
14608 @cindex read-only sections
14609 @item set trust-readonly-sections on
14610 Tell @value{GDBN} that readonly sections in your object file
14611 really are read-only (i.e.@: that their contents will not change).
14612 In that case, @value{GDBN} can fetch values from these sections
14613 out of the object file, rather than from the target program.
14614 For some targets (notably embedded ones), this can be a significant
14615 enhancement to debugging performance.
14617 The default is off.
14619 @item set trust-readonly-sections off
14620 Tell @value{GDBN} not to trust readonly sections. This means that
14621 the contents of the section might change while the program is running,
14622 and must therefore be fetched from the target when needed.
14624 @item show trust-readonly-sections
14625 Show the current setting of trusting readonly sections.
14628 All file-specifying commands allow both absolute and relative file names
14629 as arguments. @value{GDBN} always converts the file name to an absolute file
14630 name and remembers it that way.
14632 @cindex shared libraries
14633 @anchor{Shared Libraries}
14634 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14635 and IBM RS/6000 AIX shared libraries.
14637 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14638 shared libraries. @xref{Expat}.
14640 @value{GDBN} automatically loads symbol definitions from shared libraries
14641 when you use the @code{run} command, or when you examine a core file.
14642 (Before you issue the @code{run} command, @value{GDBN} does not understand
14643 references to a function in a shared library, however---unless you are
14644 debugging a core file).
14646 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14647 automatically loads the symbols at the time of the @code{shl_load} call.
14649 @c FIXME: some @value{GDBN} release may permit some refs to undef
14650 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14651 @c FIXME...lib; check this from time to time when updating manual
14653 There are times, however, when you may wish to not automatically load
14654 symbol definitions from shared libraries, such as when they are
14655 particularly large or there are many of them.
14657 To control the automatic loading of shared library symbols, use the
14661 @kindex set auto-solib-add
14662 @item set auto-solib-add @var{mode}
14663 If @var{mode} is @code{on}, symbols from all shared object libraries
14664 will be loaded automatically when the inferior begins execution, you
14665 attach to an independently started inferior, or when the dynamic linker
14666 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14667 is @code{off}, symbols must be loaded manually, using the
14668 @code{sharedlibrary} command. The default value is @code{on}.
14670 @cindex memory used for symbol tables
14671 If your program uses lots of shared libraries with debug info that
14672 takes large amounts of memory, you can decrease the @value{GDBN}
14673 memory footprint by preventing it from automatically loading the
14674 symbols from shared libraries. To that end, type @kbd{set
14675 auto-solib-add off} before running the inferior, then load each
14676 library whose debug symbols you do need with @kbd{sharedlibrary
14677 @var{regexp}}, where @var{regexp} is a regular expression that matches
14678 the libraries whose symbols you want to be loaded.
14680 @kindex show auto-solib-add
14681 @item show auto-solib-add
14682 Display the current autoloading mode.
14685 @cindex load shared library
14686 To explicitly load shared library symbols, use the @code{sharedlibrary}
14690 @kindex info sharedlibrary
14692 @item info share @var{regex}
14693 @itemx info sharedlibrary @var{regex}
14694 Print the names of the shared libraries which are currently loaded
14695 that match @var{regex}. If @var{regex} is omitted then print
14696 all shared libraries that are loaded.
14698 @kindex sharedlibrary
14700 @item sharedlibrary @var{regex}
14701 @itemx share @var{regex}
14702 Load shared object library symbols for files matching a
14703 Unix regular expression.
14704 As with files loaded automatically, it only loads shared libraries
14705 required by your program for a core file or after typing @code{run}. If
14706 @var{regex} is omitted all shared libraries required by your program are
14709 @item nosharedlibrary
14710 @kindex nosharedlibrary
14711 @cindex unload symbols from shared libraries
14712 Unload all shared object library symbols. This discards all symbols
14713 that have been loaded from all shared libraries. Symbols from shared
14714 libraries that were loaded by explicit user requests are not
14718 Sometimes you may wish that @value{GDBN} stops and gives you control
14719 when any of shared library events happen. Use the @code{set
14720 stop-on-solib-events} command for this:
14723 @item set stop-on-solib-events
14724 @kindex set stop-on-solib-events
14725 This command controls whether @value{GDBN} should give you control
14726 when the dynamic linker notifies it about some shared library event.
14727 The most common event of interest is loading or unloading of a new
14730 @item show stop-on-solib-events
14731 @kindex show stop-on-solib-events
14732 Show whether @value{GDBN} stops and gives you control when shared
14733 library events happen.
14736 Shared libraries are also supported in many cross or remote debugging
14737 configurations. @value{GDBN} needs to have access to the target's libraries;
14738 this can be accomplished either by providing copies of the libraries
14739 on the host system, or by asking @value{GDBN} to automatically retrieve the
14740 libraries from the target. If copies of the target libraries are
14741 provided, they need to be the same as the target libraries, although the
14742 copies on the target can be stripped as long as the copies on the host are
14745 @cindex where to look for shared libraries
14746 For remote debugging, you need to tell @value{GDBN} where the target
14747 libraries are, so that it can load the correct copies---otherwise, it
14748 may try to load the host's libraries. @value{GDBN} has two variables
14749 to specify the search directories for target libraries.
14752 @cindex prefix for shared library file names
14753 @cindex system root, alternate
14754 @kindex set solib-absolute-prefix
14755 @kindex set sysroot
14756 @item set sysroot @var{path}
14757 Use @var{path} as the system root for the program being debugged. Any
14758 absolute shared library paths will be prefixed with @var{path}; many
14759 runtime loaders store the absolute paths to the shared library in the
14760 target program's memory. If you use @code{set sysroot} to find shared
14761 libraries, they need to be laid out in the same way that they are on
14762 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
14765 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
14766 retrieve the target libraries from the remote system. This is only
14767 supported when using a remote target that supports the @code{remote get}
14768 command (@pxref{File Transfer,,Sending files to a remote system}).
14769 The part of @var{path} following the initial @file{remote:}
14770 (if present) is used as system root prefix on the remote file system.
14771 @footnote{If you want to specify a local system root using a directory
14772 that happens to be named @file{remote:}, you need to use some equivalent
14773 variant of the name like @file{./remote:}.}
14775 For targets with an MS-DOS based filesystem, such as MS-Windows and
14776 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
14777 absolute file name with @var{path}. But first, on Unix hosts,
14778 @value{GDBN} converts all backslash directory separators into forward
14779 slashes, because the backslash is not a directory separator on Unix:
14782 c:\foo\bar.dll @result{} c:/foo/bar.dll
14785 Then, @value{GDBN} attempts prefixing the target file name with
14786 @var{path}, and looks for the resulting file name in the host file
14790 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
14793 If that does not find the shared library, @value{GDBN} tries removing
14794 the @samp{:} character from the drive spec, both for convenience, and,
14795 for the case of the host file system not supporting file names with
14799 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
14802 This makes it possible to have a system root that mirrors a target
14803 with more than one drive. E.g., you may want to setup your local
14804 copies of the target system shared libraries like so (note @samp{c} vs
14808 @file{/path/to/sysroot/c/sys/bin/foo.dll}
14809 @file{/path/to/sysroot/c/sys/bin/bar.dll}
14810 @file{/path/to/sysroot/z/sys/bin/bar.dll}
14814 and point the system root at @file{/path/to/sysroot}, so that
14815 @value{GDBN} can find the correct copies of both
14816 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
14818 If that still does not find the shared library, @value{GDBN} tries
14819 removing the whole drive spec from the target file name:
14822 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
14825 This last lookup makes it possible to not care about the drive name,
14826 if you don't want or need to.
14828 The @code{set solib-absolute-prefix} command is an alias for @code{set
14831 @cindex default system root
14832 @cindex @samp{--with-sysroot}
14833 You can set the default system root by using the configure-time
14834 @samp{--with-sysroot} option. If the system root is inside
14835 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14836 @samp{--exec-prefix}), then the default system root will be updated
14837 automatically if the installed @value{GDBN} is moved to a new
14840 @kindex show sysroot
14842 Display the current shared library prefix.
14844 @kindex set solib-search-path
14845 @item set solib-search-path @var{path}
14846 If this variable is set, @var{path} is a colon-separated list of
14847 directories to search for shared libraries. @samp{solib-search-path}
14848 is used after @samp{sysroot} fails to locate the library, or if the
14849 path to the library is relative instead of absolute. If you want to
14850 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
14851 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
14852 finding your host's libraries. @samp{sysroot} is preferred; setting
14853 it to a nonexistent directory may interfere with automatic loading
14854 of shared library symbols.
14856 @kindex show solib-search-path
14857 @item show solib-search-path
14858 Display the current shared library search path.
14860 @cindex DOS file-name semantics of file names.
14861 @kindex set target-file-system-kind (unix|dos-based|auto)
14862 @kindex show target-file-system-kind
14863 @item set target-file-system-kind @var{kind}
14864 Set assumed file system kind for target reported file names.
14866 Shared library file names as reported by the target system may not
14867 make sense as is on the system @value{GDBN} is running on. For
14868 example, when remote debugging a target that has MS-DOS based file
14869 system semantics, from a Unix host, the target may be reporting to
14870 @value{GDBN} a list of loaded shared libraries with file names such as
14871 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
14872 drive letters, so the @samp{c:\} prefix is not normally understood as
14873 indicating an absolute file name, and neither is the backslash
14874 normally considered a directory separator character. In that case,
14875 the native file system would interpret this whole absolute file name
14876 as a relative file name with no directory components. This would make
14877 it impossible to point @value{GDBN} at a copy of the remote target's
14878 shared libraries on the host using @code{set sysroot}, and impractical
14879 with @code{set solib-search-path}. Setting
14880 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
14881 to interpret such file names similarly to how the target would, and to
14882 map them to file names valid on @value{GDBN}'s native file system
14883 semantics. The value of @var{kind} can be @code{"auto"}, in addition
14884 to one of the supported file system kinds. In that case, @value{GDBN}
14885 tries to determine the appropriate file system variant based on the
14886 current target's operating system (@pxref{ABI, ,Configuring the
14887 Current ABI}). The supported file system settings are:
14891 Instruct @value{GDBN} to assume the target file system is of Unix
14892 kind. Only file names starting the forward slash (@samp{/}) character
14893 are considered absolute, and the directory separator character is also
14897 Instruct @value{GDBN} to assume the target file system is DOS based.
14898 File names starting with either a forward slash, or a drive letter
14899 followed by a colon (e.g., @samp{c:}), are considered absolute, and
14900 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
14901 considered directory separators.
14904 Instruct @value{GDBN} to use the file system kind associated with the
14905 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
14906 This is the default.
14911 @node Separate Debug Files
14912 @section Debugging Information in Separate Files
14913 @cindex separate debugging information files
14914 @cindex debugging information in separate files
14915 @cindex @file{.debug} subdirectories
14916 @cindex debugging information directory, global
14917 @cindex global debugging information directory
14918 @cindex build ID, and separate debugging files
14919 @cindex @file{.build-id} directory
14921 @value{GDBN} allows you to put a program's debugging information in a
14922 file separate from the executable itself, in a way that allows
14923 @value{GDBN} to find and load the debugging information automatically.
14924 Since debugging information can be very large---sometimes larger
14925 than the executable code itself---some systems distribute debugging
14926 information for their executables in separate files, which users can
14927 install only when they need to debug a problem.
14929 @value{GDBN} supports two ways of specifying the separate debug info
14934 The executable contains a @dfn{debug link} that specifies the name of
14935 the separate debug info file. The separate debug file's name is
14936 usually @file{@var{executable}.debug}, where @var{executable} is the
14937 name of the corresponding executable file without leading directories
14938 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14939 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14940 checksum for the debug file, which @value{GDBN} uses to validate that
14941 the executable and the debug file came from the same build.
14944 The executable contains a @dfn{build ID}, a unique bit string that is
14945 also present in the corresponding debug info file. (This is supported
14946 only on some operating systems, notably those which use the ELF format
14947 for binary files and the @sc{gnu} Binutils.) For more details about
14948 this feature, see the description of the @option{--build-id}
14949 command-line option in @ref{Options, , Command Line Options, ld.info,
14950 The GNU Linker}. The debug info file's name is not specified
14951 explicitly by the build ID, but can be computed from the build ID, see
14955 Depending on the way the debug info file is specified, @value{GDBN}
14956 uses two different methods of looking for the debug file:
14960 For the ``debug link'' method, @value{GDBN} looks up the named file in
14961 the directory of the executable file, then in a subdirectory of that
14962 directory named @file{.debug}, and finally under the global debug
14963 directory, in a subdirectory whose name is identical to the leading
14964 directories of the executable's absolute file name.
14967 For the ``build ID'' method, @value{GDBN} looks in the
14968 @file{.build-id} subdirectory of the global debug directory for a file
14969 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
14970 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
14971 are the rest of the bit string. (Real build ID strings are 32 or more
14972 hex characters, not 10.)
14975 So, for example, suppose you ask @value{GDBN} to debug
14976 @file{/usr/bin/ls}, which has a debug link that specifies the
14977 file @file{ls.debug}, and a build ID whose value in hex is
14978 @code{abcdef1234}. If the global debug directory is
14979 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
14980 debug information files, in the indicated order:
14984 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
14986 @file{/usr/bin/ls.debug}
14988 @file{/usr/bin/.debug/ls.debug}
14990 @file{/usr/lib/debug/usr/bin/ls.debug}.
14993 You can set the global debugging info directory's name, and view the
14994 name @value{GDBN} is currently using.
14998 @kindex set debug-file-directory
14999 @item set debug-file-directory @var{directories}
15000 Set the directories which @value{GDBN} searches for separate debugging
15001 information files to @var{directory}. Multiple directory components can be set
15002 concatenating them by a directory separator.
15004 @kindex show debug-file-directory
15005 @item show debug-file-directory
15006 Show the directories @value{GDBN} searches for separate debugging
15011 @cindex @code{.gnu_debuglink} sections
15012 @cindex debug link sections
15013 A debug link is a special section of the executable file named
15014 @code{.gnu_debuglink}. The section must contain:
15018 A filename, with any leading directory components removed, followed by
15021 zero to three bytes of padding, as needed to reach the next four-byte
15022 boundary within the section, and
15024 a four-byte CRC checksum, stored in the same endianness used for the
15025 executable file itself. The checksum is computed on the debugging
15026 information file's full contents by the function given below, passing
15027 zero as the @var{crc} argument.
15030 Any executable file format can carry a debug link, as long as it can
15031 contain a section named @code{.gnu_debuglink} with the contents
15034 @cindex @code{.note.gnu.build-id} sections
15035 @cindex build ID sections
15036 The build ID is a special section in the executable file (and in other
15037 ELF binary files that @value{GDBN} may consider). This section is
15038 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15039 It contains unique identification for the built files---the ID remains
15040 the same across multiple builds of the same build tree. The default
15041 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15042 content for the build ID string. The same section with an identical
15043 value is present in the original built binary with symbols, in its
15044 stripped variant, and in the separate debugging information file.
15046 The debugging information file itself should be an ordinary
15047 executable, containing a full set of linker symbols, sections, and
15048 debugging information. The sections of the debugging information file
15049 should have the same names, addresses, and sizes as the original file,
15050 but they need not contain any data---much like a @code{.bss} section
15051 in an ordinary executable.
15053 The @sc{gnu} binary utilities (Binutils) package includes the
15054 @samp{objcopy} utility that can produce
15055 the separated executable / debugging information file pairs using the
15056 following commands:
15059 @kbd{objcopy --only-keep-debug foo foo.debug}
15064 These commands remove the debugging
15065 information from the executable file @file{foo} and place it in the file
15066 @file{foo.debug}. You can use the first, second or both methods to link the
15071 The debug link method needs the following additional command to also leave
15072 behind a debug link in @file{foo}:
15075 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15078 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15079 a version of the @code{strip} command such that the command @kbd{strip foo -f
15080 foo.debug} has the same functionality as the two @code{objcopy} commands and
15081 the @code{ln -s} command above, together.
15084 Build ID gets embedded into the main executable using @code{ld --build-id} or
15085 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15086 compatibility fixes for debug files separation are present in @sc{gnu} binary
15087 utilities (Binutils) package since version 2.18.
15092 @cindex CRC algorithm definition
15093 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15094 IEEE 802.3 using the polynomial:
15096 @c TexInfo requires naked braces for multi-digit exponents for Tex
15097 @c output, but this causes HTML output to barf. HTML has to be set using
15098 @c raw commands. So we end up having to specify this equation in 2
15103 <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>
15104 + <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
15110 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15111 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15115 The function is computed byte at a time, taking the least
15116 significant bit of each byte first. The initial pattern
15117 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15118 the final result is inverted to ensure trailing zeros also affect the
15121 @emph{Note:} This is the same CRC polynomial as used in handling the
15122 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15123 , @value{GDBN} Remote Serial Protocol}). However in the
15124 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15125 significant bit first, and the result is not inverted, so trailing
15126 zeros have no effect on the CRC value.
15128 To complete the description, we show below the code of the function
15129 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15130 initially supplied @code{crc} argument means that an initial call to
15131 this function passing in zero will start computing the CRC using
15134 @kindex gnu_debuglink_crc32
15137 gnu_debuglink_crc32 (unsigned long crc,
15138 unsigned char *buf, size_t len)
15140 static const unsigned long crc32_table[256] =
15142 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15143 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15144 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15145 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15146 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15147 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15148 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15149 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15150 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15151 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15152 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15153 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15154 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15155 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15156 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15157 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15158 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15159 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15160 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15161 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15162 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15163 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15164 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15165 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15166 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15167 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15168 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15169 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15170 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15171 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15172 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15173 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15174 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15175 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15176 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15177 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15178 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15179 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15180 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15181 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15182 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15183 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15184 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15185 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15186 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15187 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15188 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15189 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15190 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15191 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15192 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15195 unsigned char *end;
15197 crc = ~crc & 0xffffffff;
15198 for (end = buf + len; buf < end; ++buf)
15199 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15200 return ~crc & 0xffffffff;
15205 This computation does not apply to the ``build ID'' method.
15209 @section Index Files Speed Up @value{GDBN}
15210 @cindex index files
15211 @cindex @samp{.gdb_index} section
15213 When @value{GDBN} finds a symbol file, it scans the symbols in the
15214 file in order to construct an internal symbol table. This lets most
15215 @value{GDBN} operations work quickly---at the cost of a delay early
15216 on. For large programs, this delay can be quite lengthy, so
15217 @value{GDBN} provides a way to build an index, which speeds up
15220 The index is stored as a section in the symbol file. @value{GDBN} can
15221 write the index to a file, then you can put it into the symbol file
15222 using @command{objcopy}.
15224 To create an index file, use the @code{save gdb-index} command:
15227 @item save gdb-index @var{directory}
15228 @kindex save gdb-index
15229 Create an index file for each symbol file currently known by
15230 @value{GDBN}. Each file is named after its corresponding symbol file,
15231 with @samp{.gdb-index} appended, and is written into the given
15235 Once you have created an index file you can merge it into your symbol
15236 file, here named @file{symfile}, using @command{objcopy}:
15239 $ objcopy --add-section .gdb_index=symfile.gdb-index \
15240 --set-section-flags .gdb_index=readonly symfile symfile
15243 There are currently some limitation on indices. They only work when
15244 for DWARF debugging information, not stabs. And, they do not
15245 currently work for programs using Ada.
15248 @node Symbol Errors
15249 @section Errors Reading Symbol Files
15251 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15252 such as symbol types it does not recognize, or known bugs in compiler
15253 output. By default, @value{GDBN} does not notify you of such problems, since
15254 they are relatively common and primarily of interest to people
15255 debugging compilers. If you are interested in seeing information
15256 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15257 only one message about each such type of problem, no matter how many
15258 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15259 to see how many times the problems occur, with the @code{set
15260 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15263 The messages currently printed, and their meanings, include:
15266 @item inner block not inside outer block in @var{symbol}
15268 The symbol information shows where symbol scopes begin and end
15269 (such as at the start of a function or a block of statements). This
15270 error indicates that an inner scope block is not fully contained
15271 in its outer scope blocks.
15273 @value{GDBN} circumvents the problem by treating the inner block as if it had
15274 the same scope as the outer block. In the error message, @var{symbol}
15275 may be shown as ``@code{(don't know)}'' if the outer block is not a
15278 @item block at @var{address} out of order
15280 The symbol information for symbol scope blocks should occur in
15281 order of increasing addresses. This error indicates that it does not
15284 @value{GDBN} does not circumvent this problem, and has trouble
15285 locating symbols in the source file whose symbols it is reading. (You
15286 can often determine what source file is affected by specifying
15287 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15290 @item bad block start address patched
15292 The symbol information for a symbol scope block has a start address
15293 smaller than the address of the preceding source line. This is known
15294 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15296 @value{GDBN} circumvents the problem by treating the symbol scope block as
15297 starting on the previous source line.
15299 @item bad string table offset in symbol @var{n}
15302 Symbol number @var{n} contains a pointer into the string table which is
15303 larger than the size of the string table.
15305 @value{GDBN} circumvents the problem by considering the symbol to have the
15306 name @code{foo}, which may cause other problems if many symbols end up
15309 @item unknown symbol type @code{0x@var{nn}}
15311 The symbol information contains new data types that @value{GDBN} does
15312 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15313 uncomprehended information, in hexadecimal.
15315 @value{GDBN} circumvents the error by ignoring this symbol information.
15316 This usually allows you to debug your program, though certain symbols
15317 are not accessible. If you encounter such a problem and feel like
15318 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15319 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15320 and examine @code{*bufp} to see the symbol.
15322 @item stub type has NULL name
15324 @value{GDBN} could not find the full definition for a struct or class.
15326 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15327 The symbol information for a C@t{++} member function is missing some
15328 information that recent versions of the compiler should have output for
15331 @item info mismatch between compiler and debugger
15333 @value{GDBN} could not parse a type specification output by the compiler.
15338 @section GDB Data Files
15340 @cindex prefix for data files
15341 @value{GDBN} will sometimes read an auxiliary data file. These files
15342 are kept in a directory known as the @dfn{data directory}.
15344 You can set the data directory's name, and view the name @value{GDBN}
15345 is currently using.
15348 @kindex set data-directory
15349 @item set data-directory @var{directory}
15350 Set the directory which @value{GDBN} searches for auxiliary data files
15351 to @var{directory}.
15353 @kindex show data-directory
15354 @item show data-directory
15355 Show the directory @value{GDBN} searches for auxiliary data files.
15358 @cindex default data directory
15359 @cindex @samp{--with-gdb-datadir}
15360 You can set the default data directory by using the configure-time
15361 @samp{--with-gdb-datadir} option. If the data directory is inside
15362 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15363 @samp{--exec-prefix}), then the default data directory will be updated
15364 automatically if the installed @value{GDBN} is moved to a new
15368 @chapter Specifying a Debugging Target
15370 @cindex debugging target
15371 A @dfn{target} is the execution environment occupied by your program.
15373 Often, @value{GDBN} runs in the same host environment as your program;
15374 in that case, the debugging target is specified as a side effect when
15375 you use the @code{file} or @code{core} commands. When you need more
15376 flexibility---for example, running @value{GDBN} on a physically separate
15377 host, or controlling a standalone system over a serial port or a
15378 realtime system over a TCP/IP connection---you can use the @code{target}
15379 command to specify one of the target types configured for @value{GDBN}
15380 (@pxref{Target Commands, ,Commands for Managing Targets}).
15382 @cindex target architecture
15383 It is possible to build @value{GDBN} for several different @dfn{target
15384 architectures}. When @value{GDBN} is built like that, you can choose
15385 one of the available architectures with the @kbd{set architecture}
15389 @kindex set architecture
15390 @kindex show architecture
15391 @item set architecture @var{arch}
15392 This command sets the current target architecture to @var{arch}. The
15393 value of @var{arch} can be @code{"auto"}, in addition to one of the
15394 supported architectures.
15396 @item show architecture
15397 Show the current target architecture.
15399 @item set processor
15401 @kindex set processor
15402 @kindex show processor
15403 These are alias commands for, respectively, @code{set architecture}
15404 and @code{show architecture}.
15408 * Active Targets:: Active targets
15409 * Target Commands:: Commands for managing targets
15410 * Byte Order:: Choosing target byte order
15413 @node Active Targets
15414 @section Active Targets
15416 @cindex stacking targets
15417 @cindex active targets
15418 @cindex multiple targets
15420 There are multiple classes of targets such as: processes, executable files or
15421 recording sessions. Core files belong to the process class, making core file
15422 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
15423 on multiple active targets, one in each class. This allows you to (for
15424 example) start a process and inspect its activity, while still having access to
15425 the executable file after the process finishes. Or if you start process
15426 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
15427 presented a virtual layer of the recording target, while the process target
15428 remains stopped at the chronologically last point of the process execution.
15430 Use the @code{core-file} and @code{exec-file} commands to select a new core
15431 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
15432 specify as a target a process that is already running, use the @code{attach}
15433 command (@pxref{Attach, ,Debugging an Already-running Process}).
15435 @node Target Commands
15436 @section Commands for Managing Targets
15439 @item target @var{type} @var{parameters}
15440 Connects the @value{GDBN} host environment to a target machine or
15441 process. A target is typically a protocol for talking to debugging
15442 facilities. You use the argument @var{type} to specify the type or
15443 protocol of the target machine.
15445 Further @var{parameters} are interpreted by the target protocol, but
15446 typically include things like device names or host names to connect
15447 with, process numbers, and baud rates.
15449 The @code{target} command does not repeat if you press @key{RET} again
15450 after executing the command.
15452 @kindex help target
15454 Displays the names of all targets available. To display targets
15455 currently selected, use either @code{info target} or @code{info files}
15456 (@pxref{Files, ,Commands to Specify Files}).
15458 @item help target @var{name}
15459 Describe a particular target, including any parameters necessary to
15462 @kindex set gnutarget
15463 @item set gnutarget @var{args}
15464 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15465 knows whether it is reading an @dfn{executable},
15466 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15467 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15468 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15471 @emph{Warning:} To specify a file format with @code{set gnutarget},
15472 you must know the actual BFD name.
15476 @xref{Files, , Commands to Specify Files}.
15478 @kindex show gnutarget
15479 @item show gnutarget
15480 Use the @code{show gnutarget} command to display what file format
15481 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15482 @value{GDBN} will determine the file format for each file automatically,
15483 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15486 @cindex common targets
15487 Here are some common targets (available, or not, depending on the GDB
15492 @item target exec @var{program}
15493 @cindex executable file target
15494 An executable file. @samp{target exec @var{program}} is the same as
15495 @samp{exec-file @var{program}}.
15497 @item target core @var{filename}
15498 @cindex core dump file target
15499 A core dump file. @samp{target core @var{filename}} is the same as
15500 @samp{core-file @var{filename}}.
15502 @item target remote @var{medium}
15503 @cindex remote target
15504 A remote system connected to @value{GDBN} via a serial line or network
15505 connection. This command tells @value{GDBN} to use its own remote
15506 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15508 For example, if you have a board connected to @file{/dev/ttya} on the
15509 machine running @value{GDBN}, you could say:
15512 target remote /dev/ttya
15515 @code{target remote} supports the @code{load} command. This is only
15516 useful if you have some other way of getting the stub to the target
15517 system, and you can put it somewhere in memory where it won't get
15518 clobbered by the download.
15520 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15521 @cindex built-in simulator target
15522 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15530 works; however, you cannot assume that a specific memory map, device
15531 drivers, or even basic I/O is available, although some simulators do
15532 provide these. For info about any processor-specific simulator details,
15533 see the appropriate section in @ref{Embedded Processors, ,Embedded
15538 Some configurations may include these targets as well:
15542 @item target nrom @var{dev}
15543 @cindex NetROM ROM emulator target
15544 NetROM ROM emulator. This target only supports downloading.
15548 Different targets are available on different configurations of @value{GDBN};
15549 your configuration may have more or fewer targets.
15551 Many remote targets require you to download the executable's code once
15552 you've successfully established a connection. You may wish to control
15553 various aspects of this process.
15558 @kindex set hash@r{, for remote monitors}
15559 @cindex hash mark while downloading
15560 This command controls whether a hash mark @samp{#} is displayed while
15561 downloading a file to the remote monitor. If on, a hash mark is
15562 displayed after each S-record is successfully downloaded to the
15566 @kindex show hash@r{, for remote monitors}
15567 Show the current status of displaying the hash mark.
15569 @item set debug monitor
15570 @kindex set debug monitor
15571 @cindex display remote monitor communications
15572 Enable or disable display of communications messages between
15573 @value{GDBN} and the remote monitor.
15575 @item show debug monitor
15576 @kindex show debug monitor
15577 Show the current status of displaying communications between
15578 @value{GDBN} and the remote monitor.
15583 @kindex load @var{filename}
15584 @item load @var{filename}
15586 Depending on what remote debugging facilities are configured into
15587 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15588 is meant to make @var{filename} (an executable) available for debugging
15589 on the remote system---by downloading, or dynamic linking, for example.
15590 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15591 the @code{add-symbol-file} command.
15593 If your @value{GDBN} does not have a @code{load} command, attempting to
15594 execute it gets the error message ``@code{You can't do that when your
15595 target is @dots{}}''
15597 The file is loaded at whatever address is specified in the executable.
15598 For some object file formats, you can specify the load address when you
15599 link the program; for other formats, like a.out, the object file format
15600 specifies a fixed address.
15601 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15603 Depending on the remote side capabilities, @value{GDBN} may be able to
15604 load programs into flash memory.
15606 @code{load} does not repeat if you press @key{RET} again after using it.
15610 @section Choosing Target Byte Order
15612 @cindex choosing target byte order
15613 @cindex target byte order
15615 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15616 offer the ability to run either big-endian or little-endian byte
15617 orders. Usually the executable or symbol will include a bit to
15618 designate the endian-ness, and you will not need to worry about
15619 which to use. However, you may still find it useful to adjust
15620 @value{GDBN}'s idea of processor endian-ness manually.
15624 @item set endian big
15625 Instruct @value{GDBN} to assume the target is big-endian.
15627 @item set endian little
15628 Instruct @value{GDBN} to assume the target is little-endian.
15630 @item set endian auto
15631 Instruct @value{GDBN} to use the byte order associated with the
15635 Display @value{GDBN}'s current idea of the target byte order.
15639 Note that these commands merely adjust interpretation of symbolic
15640 data on the host, and that they have absolutely no effect on the
15644 @node Remote Debugging
15645 @chapter Debugging Remote Programs
15646 @cindex remote debugging
15648 If you are trying to debug a program running on a machine that cannot run
15649 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15650 For example, you might use remote debugging on an operating system kernel,
15651 or on a small system which does not have a general purpose operating system
15652 powerful enough to run a full-featured debugger.
15654 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15655 to make this work with particular debugging targets. In addition,
15656 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15657 but not specific to any particular target system) which you can use if you
15658 write the remote stubs---the code that runs on the remote system to
15659 communicate with @value{GDBN}.
15661 Other remote targets may be available in your
15662 configuration of @value{GDBN}; use @code{help target} to list them.
15665 * Connecting:: Connecting to a remote target
15666 * File Transfer:: Sending files to a remote system
15667 * Server:: Using the gdbserver program
15668 * Remote Configuration:: Remote configuration
15669 * Remote Stub:: Implementing a remote stub
15673 @section Connecting to a Remote Target
15675 On the @value{GDBN} host machine, you will need an unstripped copy of
15676 your program, since @value{GDBN} needs symbol and debugging information.
15677 Start up @value{GDBN} as usual, using the name of the local copy of your
15678 program as the first argument.
15680 @cindex @code{target remote}
15681 @value{GDBN} can communicate with the target over a serial line, or
15682 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15683 each case, @value{GDBN} uses the same protocol for debugging your
15684 program; only the medium carrying the debugging packets varies. The
15685 @code{target remote} command establishes a connection to the target.
15686 Its arguments indicate which medium to use:
15690 @item target remote @var{serial-device}
15691 @cindex serial line, @code{target remote}
15692 Use @var{serial-device} to communicate with the target. For example,
15693 to use a serial line connected to the device named @file{/dev/ttyb}:
15696 target remote /dev/ttyb
15699 If you're using a serial line, you may want to give @value{GDBN} the
15700 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15701 (@pxref{Remote Configuration, set remotebaud}) before the
15702 @code{target} command.
15704 @item target remote @code{@var{host}:@var{port}}
15705 @itemx target remote @code{tcp:@var{host}:@var{port}}
15706 @cindex @acronym{TCP} port, @code{target remote}
15707 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15708 The @var{host} may be either a host name or a numeric @acronym{IP}
15709 address; @var{port} must be a decimal number. The @var{host} could be
15710 the target machine itself, if it is directly connected to the net, or
15711 it might be a terminal server which in turn has a serial line to the
15714 For example, to connect to port 2828 on a terminal server named
15718 target remote manyfarms:2828
15721 If your remote target is actually running on the same machine as your
15722 debugger session (e.g.@: a simulator for your target running on the
15723 same host), you can omit the hostname. For example, to connect to
15724 port 1234 on your local machine:
15727 target remote :1234
15731 Note that the colon is still required here.
15733 @item target remote @code{udp:@var{host}:@var{port}}
15734 @cindex @acronym{UDP} port, @code{target remote}
15735 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15736 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15739 target remote udp:manyfarms:2828
15742 When using a @acronym{UDP} connection for remote debugging, you should
15743 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15744 can silently drop packets on busy or unreliable networks, which will
15745 cause havoc with your debugging session.
15747 @item target remote | @var{command}
15748 @cindex pipe, @code{target remote} to
15749 Run @var{command} in the background and communicate with it using a
15750 pipe. The @var{command} is a shell command, to be parsed and expanded
15751 by the system's command shell, @code{/bin/sh}; it should expect remote
15752 protocol packets on its standard input, and send replies on its
15753 standard output. You could use this to run a stand-alone simulator
15754 that speaks the remote debugging protocol, to make net connections
15755 using programs like @code{ssh}, or for other similar tricks.
15757 If @var{command} closes its standard output (perhaps by exiting),
15758 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15759 program has already exited, this will have no effect.)
15763 Once the connection has been established, you can use all the usual
15764 commands to examine and change data. The remote program is already
15765 running; you can use @kbd{step} and @kbd{continue}, and you do not
15766 need to use @kbd{run}.
15768 @cindex interrupting remote programs
15769 @cindex remote programs, interrupting
15770 Whenever @value{GDBN} is waiting for the remote program, if you type the
15771 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
15772 program. This may or may not succeed, depending in part on the hardware
15773 and the serial drivers the remote system uses. If you type the
15774 interrupt character once again, @value{GDBN} displays this prompt:
15777 Interrupted while waiting for the program.
15778 Give up (and stop debugging it)? (y or n)
15781 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
15782 (If you decide you want to try again later, you can use @samp{target
15783 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
15784 goes back to waiting.
15787 @kindex detach (remote)
15789 When you have finished debugging the remote program, you can use the
15790 @code{detach} command to release it from @value{GDBN} control.
15791 Detaching from the target normally resumes its execution, but the results
15792 will depend on your particular remote stub. After the @code{detach}
15793 command, @value{GDBN} is free to connect to another target.
15797 The @code{disconnect} command behaves like @code{detach}, except that
15798 the target is generally not resumed. It will wait for @value{GDBN}
15799 (this instance or another one) to connect and continue debugging. After
15800 the @code{disconnect} command, @value{GDBN} is again free to connect to
15803 @cindex send command to remote monitor
15804 @cindex extend @value{GDBN} for remote targets
15805 @cindex add new commands for external monitor
15807 @item monitor @var{cmd}
15808 This command allows you to send arbitrary commands directly to the
15809 remote monitor. Since @value{GDBN} doesn't care about the commands it
15810 sends like this, this command is the way to extend @value{GDBN}---you
15811 can add new commands that only the external monitor will understand
15815 @node File Transfer
15816 @section Sending files to a remote system
15817 @cindex remote target, file transfer
15818 @cindex file transfer
15819 @cindex sending files to remote systems
15821 Some remote targets offer the ability to transfer files over the same
15822 connection used to communicate with @value{GDBN}. This is convenient
15823 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
15824 running @code{gdbserver} over a network interface. For other targets,
15825 e.g.@: embedded devices with only a single serial port, this may be
15826 the only way to upload or download files.
15828 Not all remote targets support these commands.
15832 @item remote put @var{hostfile} @var{targetfile}
15833 Copy file @var{hostfile} from the host system (the machine running
15834 @value{GDBN}) to @var{targetfile} on the target system.
15837 @item remote get @var{targetfile} @var{hostfile}
15838 Copy file @var{targetfile} from the target system to @var{hostfile}
15839 on the host system.
15841 @kindex remote delete
15842 @item remote delete @var{targetfile}
15843 Delete @var{targetfile} from the target system.
15848 @section Using the @code{gdbserver} Program
15851 @cindex remote connection without stubs
15852 @code{gdbserver} is a control program for Unix-like systems, which
15853 allows you to connect your program with a remote @value{GDBN} via
15854 @code{target remote}---but without linking in the usual debugging stub.
15856 @code{gdbserver} is not a complete replacement for the debugging stubs,
15857 because it requires essentially the same operating-system facilities
15858 that @value{GDBN} itself does. In fact, a system that can run
15859 @code{gdbserver} to connect to a remote @value{GDBN} could also run
15860 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
15861 because it is a much smaller program than @value{GDBN} itself. It is
15862 also easier to port than all of @value{GDBN}, so you may be able to get
15863 started more quickly on a new system by using @code{gdbserver}.
15864 Finally, if you develop code for real-time systems, you may find that
15865 the tradeoffs involved in real-time operation make it more convenient to
15866 do as much development work as possible on another system, for example
15867 by cross-compiling. You can use @code{gdbserver} to make a similar
15868 choice for debugging.
15870 @value{GDBN} and @code{gdbserver} communicate via either a serial line
15871 or a TCP connection, using the standard @value{GDBN} remote serial
15875 @emph{Warning:} @code{gdbserver} does not have any built-in security.
15876 Do not run @code{gdbserver} connected to any public network; a
15877 @value{GDBN} connection to @code{gdbserver} provides access to the
15878 target system with the same privileges as the user running
15882 @subsection Running @code{gdbserver}
15883 @cindex arguments, to @code{gdbserver}
15885 Run @code{gdbserver} on the target system. You need a copy of the
15886 program you want to debug, including any libraries it requires.
15887 @code{gdbserver} does not need your program's symbol table, so you can
15888 strip the program if necessary to save space. @value{GDBN} on the host
15889 system does all the symbol handling.
15891 To use the server, you must tell it how to communicate with @value{GDBN};
15892 the name of your program; and the arguments for your program. The usual
15896 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
15899 @var{comm} is either a device name (to use a serial line) or a TCP
15900 hostname and portnumber. For example, to debug Emacs with the argument
15901 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
15905 target> gdbserver /dev/com1 emacs foo.txt
15908 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
15911 To use a TCP connection instead of a serial line:
15914 target> gdbserver host:2345 emacs foo.txt
15917 The only difference from the previous example is the first argument,
15918 specifying that you are communicating with the host @value{GDBN} via
15919 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
15920 expect a TCP connection from machine @samp{host} to local TCP port 2345.
15921 (Currently, the @samp{host} part is ignored.) You can choose any number
15922 you want for the port number as long as it does not conflict with any
15923 TCP ports already in use on the target system (for example, @code{23} is
15924 reserved for @code{telnet}).@footnote{If you choose a port number that
15925 conflicts with another service, @code{gdbserver} prints an error message
15926 and exits.} You must use the same port number with the host @value{GDBN}
15927 @code{target remote} command.
15929 @subsubsection Attaching to a Running Program
15931 On some targets, @code{gdbserver} can also attach to running programs.
15932 This is accomplished via the @code{--attach} argument. The syntax is:
15935 target> gdbserver --attach @var{comm} @var{pid}
15938 @var{pid} is the process ID of a currently running process. It isn't necessary
15939 to point @code{gdbserver} at a binary for the running process.
15942 @cindex attach to a program by name
15943 You can debug processes by name instead of process ID if your target has the
15944 @code{pidof} utility:
15947 target> gdbserver --attach @var{comm} `pidof @var{program}`
15950 In case more than one copy of @var{program} is running, or @var{program}
15951 has multiple threads, most versions of @code{pidof} support the
15952 @code{-s} option to only return the first process ID.
15954 @subsubsection Multi-Process Mode for @code{gdbserver}
15955 @cindex gdbserver, multiple processes
15956 @cindex multiple processes with gdbserver
15958 When you connect to @code{gdbserver} using @code{target remote},
15959 @code{gdbserver} debugs the specified program only once. When the
15960 program exits, or you detach from it, @value{GDBN} closes the connection
15961 and @code{gdbserver} exits.
15963 If you connect using @kbd{target extended-remote}, @code{gdbserver}
15964 enters multi-process mode. When the debugged program exits, or you
15965 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
15966 though no program is running. The @code{run} and @code{attach}
15967 commands instruct @code{gdbserver} to run or attach to a new program.
15968 The @code{run} command uses @code{set remote exec-file} (@pxref{set
15969 remote exec-file}) to select the program to run. Command line
15970 arguments are supported, except for wildcard expansion and I/O
15971 redirection (@pxref{Arguments}).
15973 To start @code{gdbserver} without supplying an initial command to run
15974 or process ID to attach, use the @option{--multi} command line option.
15975 Then you can connect using @kbd{target extended-remote} and start
15976 the program you want to debug.
15978 @code{gdbserver} does not automatically exit in multi-process mode.
15979 You can terminate it by using @code{monitor exit}
15980 (@pxref{Monitor Commands for gdbserver}).
15982 @subsubsection Other Command-Line Arguments for @code{gdbserver}
15984 The @option{--debug} option tells @code{gdbserver} to display extra
15985 status information about the debugging process. The
15986 @option{--remote-debug} option tells @code{gdbserver} to display
15987 remote protocol debug output. These options are intended for
15988 @code{gdbserver} development and for bug reports to the developers.
15990 The @option{--wrapper} option specifies a wrapper to launch programs
15991 for debugging. The option should be followed by the name of the
15992 wrapper, then any command-line arguments to pass to the wrapper, then
15993 @kbd{--} indicating the end of the wrapper arguments.
15995 @code{gdbserver} runs the specified wrapper program with a combined
15996 command line including the wrapper arguments, then the name of the
15997 program to debug, then any arguments to the program. The wrapper
15998 runs until it executes your program, and then @value{GDBN} gains control.
16000 You can use any program that eventually calls @code{execve} with
16001 its arguments as a wrapper. Several standard Unix utilities do
16002 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16003 with @code{exec "$@@"} will also work.
16005 For example, you can use @code{env} to pass an environment variable to
16006 the debugged program, without setting the variable in @code{gdbserver}'s
16010 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16013 @subsection Connecting to @code{gdbserver}
16015 Run @value{GDBN} on the host system.
16017 First make sure you have the necessary symbol files. Load symbols for
16018 your application using the @code{file} command before you connect. Use
16019 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16020 was compiled with the correct sysroot using @code{--with-sysroot}).
16022 The symbol file and target libraries must exactly match the executable
16023 and libraries on the target, with one exception: the files on the host
16024 system should not be stripped, even if the files on the target system
16025 are. Mismatched or missing files will lead to confusing results
16026 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16027 files may also prevent @code{gdbserver} from debugging multi-threaded
16030 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16031 For TCP connections, you must start up @code{gdbserver} prior to using
16032 the @code{target remote} command. Otherwise you may get an error whose
16033 text depends on the host system, but which usually looks something like
16034 @samp{Connection refused}. Don't use the @code{load}
16035 command in @value{GDBN} when using @code{gdbserver}, since the program is
16036 already on the target.
16038 @subsection Monitor Commands for @code{gdbserver}
16039 @cindex monitor commands, for @code{gdbserver}
16040 @anchor{Monitor Commands for gdbserver}
16042 During a @value{GDBN} session using @code{gdbserver}, you can use the
16043 @code{monitor} command to send special requests to @code{gdbserver}.
16044 Here are the available commands.
16048 List the available monitor commands.
16050 @item monitor set debug 0
16051 @itemx monitor set debug 1
16052 Disable or enable general debugging messages.
16054 @item monitor set remote-debug 0
16055 @itemx monitor set remote-debug 1
16056 Disable or enable specific debugging messages associated with the remote
16057 protocol (@pxref{Remote Protocol}).
16059 @item monitor set libthread-db-search-path [PATH]
16060 @cindex gdbserver, search path for @code{libthread_db}
16061 When this command is issued, @var{path} is a colon-separated list of
16062 directories to search for @code{libthread_db} (@pxref{Threads,,set
16063 libthread-db-search-path}). If you omit @var{path},
16064 @samp{libthread-db-search-path} will be reset to an empty list.
16067 Tell gdbserver to exit immediately. This command should be followed by
16068 @code{disconnect} to close the debugging session. @code{gdbserver} will
16069 detach from any attached processes and kill any processes it created.
16070 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16071 of a multi-process mode debug session.
16075 @subsection Tracepoints support in @code{gdbserver}
16076 @cindex tracepoints support in @code{gdbserver}
16078 On some targets, @code{gdbserver} supports tracepoints, fast
16079 tracepoints and static tracepoints.
16081 For fast or static tracepoints to work, a special library called the
16082 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16083 This library is built and distributed as an integral part of
16084 @code{gdbserver}. In addition, support for static tracepoints
16085 requires building the in-process agent library with static tracepoints
16086 support. At present, the UST (LTTng Userspace Tracer,
16087 @url{http://lttng.org/ust}) tracing engine is supported. This support
16088 is automatically available if UST development headers are found in the
16089 standard include path when @code{gdbserver} is built, or if
16090 @code{gdbserver} was explicitly configured using @option{--with-ust}
16091 to point at such headers. You can explicitly disable the support
16092 using @option{--with-ust=no}.
16094 There are several ways to load the in-process agent in your program:
16097 @item Specifying it as dependency at link time
16099 You can link your program dynamically with the in-process agent
16100 library. On most systems, this is accomplished by adding
16101 @code{-linproctrace} to the link command.
16103 @item Using the system's preloading mechanisms
16105 You can force loading the in-process agent at startup time by using
16106 your system's support for preloading shared libraries. Many Unixes
16107 support the concept of preloading user defined libraries. In most
16108 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16109 in the environment. See also the description of @code{gdbserver}'s
16110 @option{--wrapper} command line option.
16112 @item Using @value{GDBN} to force loading the agent at run time
16114 On some systems, you can force the inferior to load a shared library,
16115 by calling a dynamic loader function in the inferior that takes care
16116 of dynamically looking up and loading a shared library. On most Unix
16117 systems, the function is @code{dlopen}. You'll use the @code{call}
16118 command for that. For example:
16121 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16124 Note that on most Unix systems, for the @code{dlopen} function to be
16125 available, the program needs to be linked with @code{-ldl}.
16128 On systems that have a userspace dynamic loader, like most Unix
16129 systems, when you connect to @code{gdbserver} using @code{target
16130 remote}, you'll find that the program is stopped at the dynamic
16131 loader's entry point, and no shared library has been loaded in the
16132 program's address space yet, including the in-process agent. In that
16133 case, before being able to use any of the fast or static tracepoints
16134 features, you need to let the loader run and load the shared
16135 libraries. The simplest way to do that is to run the program to the
16136 main procedure. E.g., if debugging a C or C@t{++} program, start
16137 @code{gdbserver} like so:
16140 $ gdbserver :9999 myprogram
16143 Start GDB and connect to @code{gdbserver} like so, and run to main:
16147 (@value{GDBP}) target remote myhost:9999
16148 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16149 (@value{GDBP}) b main
16150 (@value{GDBP}) continue
16153 The in-process tracing agent library should now be loaded into the
16154 process; you can confirm it with the @code{info sharedlibrary}
16155 command, which will list @file{libinproctrace.so} as loaded in the
16156 process. You are now ready to install fast tracepoints, list static
16157 tracepoint markers, probe static tracepoints markers, and start
16160 @node Remote Configuration
16161 @section Remote Configuration
16164 @kindex show remote
16165 This section documents the configuration options available when
16166 debugging remote programs. For the options related to the File I/O
16167 extensions of the remote protocol, see @ref{system,
16168 system-call-allowed}.
16171 @item set remoteaddresssize @var{bits}
16172 @cindex address size for remote targets
16173 @cindex bits in remote address
16174 Set the maximum size of address in a memory packet to the specified
16175 number of bits. @value{GDBN} will mask off the address bits above
16176 that number, when it passes addresses to the remote target. The
16177 default value is the number of bits in the target's address.
16179 @item show remoteaddresssize
16180 Show the current value of remote address size in bits.
16182 @item set remotebaud @var{n}
16183 @cindex baud rate for remote targets
16184 Set the baud rate for the remote serial I/O to @var{n} baud. The
16185 value is used to set the speed of the serial port used for debugging
16188 @item show remotebaud
16189 Show the current speed of the remote connection.
16191 @item set remotebreak
16192 @cindex interrupt remote programs
16193 @cindex BREAK signal instead of Ctrl-C
16194 @anchor{set remotebreak}
16195 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16196 when you type @kbd{Ctrl-c} to interrupt the program running
16197 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16198 character instead. The default is off, since most remote systems
16199 expect to see @samp{Ctrl-C} as the interrupt signal.
16201 @item show remotebreak
16202 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16203 interrupt the remote program.
16205 @item set remoteflow on
16206 @itemx set remoteflow off
16207 @kindex set remoteflow
16208 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16209 on the serial port used to communicate to the remote target.
16211 @item show remoteflow
16212 @kindex show remoteflow
16213 Show the current setting of hardware flow control.
16215 @item set remotelogbase @var{base}
16216 Set the base (a.k.a.@: radix) of logging serial protocol
16217 communications to @var{base}. Supported values of @var{base} are:
16218 @code{ascii}, @code{octal}, and @code{hex}. The default is
16221 @item show remotelogbase
16222 Show the current setting of the radix for logging remote serial
16225 @item set remotelogfile @var{file}
16226 @cindex record serial communications on file
16227 Record remote serial communications on the named @var{file}. The
16228 default is not to record at all.
16230 @item show remotelogfile.
16231 Show the current setting of the file name on which to record the
16232 serial communications.
16234 @item set remotetimeout @var{num}
16235 @cindex timeout for serial communications
16236 @cindex remote timeout
16237 Set the timeout limit to wait for the remote target to respond to
16238 @var{num} seconds. The default is 2 seconds.
16240 @item show remotetimeout
16241 Show the current number of seconds to wait for the remote target
16244 @cindex limit hardware breakpoints and watchpoints
16245 @cindex remote target, limit break- and watchpoints
16246 @anchor{set remote hardware-watchpoint-limit}
16247 @anchor{set remote hardware-breakpoint-limit}
16248 @item set remote hardware-watchpoint-limit @var{limit}
16249 @itemx set remote hardware-breakpoint-limit @var{limit}
16250 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16251 watchpoints. A limit of -1, the default, is treated as unlimited.
16253 @item set remote exec-file @var{filename}
16254 @itemx show remote exec-file
16255 @anchor{set remote exec-file}
16256 @cindex executable file, for remote target
16257 Select the file used for @code{run} with @code{target
16258 extended-remote}. This should be set to a filename valid on the
16259 target system. If it is not set, the target will use a default
16260 filename (e.g.@: the last program run).
16262 @item set remote interrupt-sequence
16263 @cindex interrupt remote programs
16264 @cindex select Ctrl-C, BREAK or BREAK-g
16265 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16266 @samp{BREAK-g} as the
16267 sequence to the remote target in order to interrupt the execution.
16268 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16269 is high level of serial line for some certain time.
16270 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16271 It is @code{BREAK} signal followed by character @code{g}.
16273 @item show interrupt-sequence
16274 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16275 is sent by @value{GDBN} to interrupt the remote program.
16276 @code{BREAK-g} is BREAK signal followed by @code{g} and
16277 also known as Magic SysRq g.
16279 @item set remote interrupt-on-connect
16280 @cindex send interrupt-sequence on start
16281 Specify whether interrupt-sequence is sent to remote target when
16282 @value{GDBN} connects to it. This is mostly needed when you debug
16283 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16284 which is known as Magic SysRq g in order to connect @value{GDBN}.
16286 @item show interrupt-on-connect
16287 Show whether interrupt-sequence is sent
16288 to remote target when @value{GDBN} connects to it.
16292 @item set tcp auto-retry on
16293 @cindex auto-retry, for remote TCP target
16294 Enable auto-retry for remote TCP connections. This is useful if the remote
16295 debugging agent is launched in parallel with @value{GDBN}; there is a race
16296 condition because the agent may not become ready to accept the connection
16297 before @value{GDBN} attempts to connect. When auto-retry is
16298 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16299 to establish the connection using the timeout specified by
16300 @code{set tcp connect-timeout}.
16302 @item set tcp auto-retry off
16303 Do not auto-retry failed TCP connections.
16305 @item show tcp auto-retry
16306 Show the current auto-retry setting.
16308 @item set tcp connect-timeout @var{seconds}
16309 @cindex connection timeout, for remote TCP target
16310 @cindex timeout, for remote target connection
16311 Set the timeout for establishing a TCP connection to the remote target to
16312 @var{seconds}. The timeout affects both polling to retry failed connections
16313 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16314 that are merely slow to complete, and represents an approximate cumulative
16317 @item show tcp connect-timeout
16318 Show the current connection timeout setting.
16321 @cindex remote packets, enabling and disabling
16322 The @value{GDBN} remote protocol autodetects the packets supported by
16323 your debugging stub. If you need to override the autodetection, you
16324 can use these commands to enable or disable individual packets. Each
16325 packet can be set to @samp{on} (the remote target supports this
16326 packet), @samp{off} (the remote target does not support this packet),
16327 or @samp{auto} (detect remote target support for this packet). They
16328 all default to @samp{auto}. For more information about each packet,
16329 see @ref{Remote Protocol}.
16331 During normal use, you should not have to use any of these commands.
16332 If you do, that may be a bug in your remote debugging stub, or a bug
16333 in @value{GDBN}. You may want to report the problem to the
16334 @value{GDBN} developers.
16336 For each packet @var{name}, the command to enable or disable the
16337 packet is @code{set remote @var{name}-packet}. The available settings
16340 @multitable @columnfractions 0.28 0.32 0.25
16343 @tab Related Features
16345 @item @code{fetch-register}
16347 @tab @code{info registers}
16349 @item @code{set-register}
16353 @item @code{binary-download}
16355 @tab @code{load}, @code{set}
16357 @item @code{read-aux-vector}
16358 @tab @code{qXfer:auxv:read}
16359 @tab @code{info auxv}
16361 @item @code{symbol-lookup}
16362 @tab @code{qSymbol}
16363 @tab Detecting multiple threads
16365 @item @code{attach}
16366 @tab @code{vAttach}
16369 @item @code{verbose-resume}
16371 @tab Stepping or resuming multiple threads
16377 @item @code{software-breakpoint}
16381 @item @code{hardware-breakpoint}
16385 @item @code{write-watchpoint}
16389 @item @code{read-watchpoint}
16393 @item @code{access-watchpoint}
16397 @item @code{target-features}
16398 @tab @code{qXfer:features:read}
16399 @tab @code{set architecture}
16401 @item @code{library-info}
16402 @tab @code{qXfer:libraries:read}
16403 @tab @code{info sharedlibrary}
16405 @item @code{memory-map}
16406 @tab @code{qXfer:memory-map:read}
16407 @tab @code{info mem}
16409 @item @code{read-sdata-object}
16410 @tab @code{qXfer:sdata:read}
16411 @tab @code{print $_sdata}
16413 @item @code{read-spu-object}
16414 @tab @code{qXfer:spu:read}
16415 @tab @code{info spu}
16417 @item @code{write-spu-object}
16418 @tab @code{qXfer:spu:write}
16419 @tab @code{info spu}
16421 @item @code{read-siginfo-object}
16422 @tab @code{qXfer:siginfo:read}
16423 @tab @code{print $_siginfo}
16425 @item @code{write-siginfo-object}
16426 @tab @code{qXfer:siginfo:write}
16427 @tab @code{set $_siginfo}
16429 @item @code{threads}
16430 @tab @code{qXfer:threads:read}
16431 @tab @code{info threads}
16433 @item @code{get-thread-local-@*storage-address}
16434 @tab @code{qGetTLSAddr}
16435 @tab Displaying @code{__thread} variables
16437 @item @code{get-thread-information-block-address}
16438 @tab @code{qGetTIBAddr}
16439 @tab Display MS-Windows Thread Information Block.
16441 @item @code{search-memory}
16442 @tab @code{qSearch:memory}
16445 @item @code{supported-packets}
16446 @tab @code{qSupported}
16447 @tab Remote communications parameters
16449 @item @code{pass-signals}
16450 @tab @code{QPassSignals}
16451 @tab @code{handle @var{signal}}
16453 @item @code{hostio-close-packet}
16454 @tab @code{vFile:close}
16455 @tab @code{remote get}, @code{remote put}
16457 @item @code{hostio-open-packet}
16458 @tab @code{vFile:open}
16459 @tab @code{remote get}, @code{remote put}
16461 @item @code{hostio-pread-packet}
16462 @tab @code{vFile:pread}
16463 @tab @code{remote get}, @code{remote put}
16465 @item @code{hostio-pwrite-packet}
16466 @tab @code{vFile:pwrite}
16467 @tab @code{remote get}, @code{remote put}
16469 @item @code{hostio-unlink-packet}
16470 @tab @code{vFile:unlink}
16471 @tab @code{remote delete}
16473 @item @code{noack-packet}
16474 @tab @code{QStartNoAckMode}
16475 @tab Packet acknowledgment
16477 @item @code{osdata}
16478 @tab @code{qXfer:osdata:read}
16479 @tab @code{info os}
16481 @item @code{query-attached}
16482 @tab @code{qAttached}
16483 @tab Querying remote process attach state.
16487 @section Implementing a Remote Stub
16489 @cindex debugging stub, example
16490 @cindex remote stub, example
16491 @cindex stub example, remote debugging
16492 The stub files provided with @value{GDBN} implement the target side of the
16493 communication protocol, and the @value{GDBN} side is implemented in the
16494 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16495 these subroutines to communicate, and ignore the details. (If you're
16496 implementing your own stub file, you can still ignore the details: start
16497 with one of the existing stub files. @file{sparc-stub.c} is the best
16498 organized, and therefore the easiest to read.)
16500 @cindex remote serial debugging, overview
16501 To debug a program running on another machine (the debugging
16502 @dfn{target} machine), you must first arrange for all the usual
16503 prerequisites for the program to run by itself. For example, for a C
16508 A startup routine to set up the C runtime environment; these usually
16509 have a name like @file{crt0}. The startup routine may be supplied by
16510 your hardware supplier, or you may have to write your own.
16513 A C subroutine library to support your program's
16514 subroutine calls, notably managing input and output.
16517 A way of getting your program to the other machine---for example, a
16518 download program. These are often supplied by the hardware
16519 manufacturer, but you may have to write your own from hardware
16523 The next step is to arrange for your program to use a serial port to
16524 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16525 machine). In general terms, the scheme looks like this:
16529 @value{GDBN} already understands how to use this protocol; when everything
16530 else is set up, you can simply use the @samp{target remote} command
16531 (@pxref{Targets,,Specifying a Debugging Target}).
16533 @item On the target,
16534 you must link with your program a few special-purpose subroutines that
16535 implement the @value{GDBN} remote serial protocol. The file containing these
16536 subroutines is called a @dfn{debugging stub}.
16538 On certain remote targets, you can use an auxiliary program
16539 @code{gdbserver} instead of linking a stub into your program.
16540 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16543 The debugging stub is specific to the architecture of the remote
16544 machine; for example, use @file{sparc-stub.c} to debug programs on
16547 @cindex remote serial stub list
16548 These working remote stubs are distributed with @value{GDBN}:
16553 @cindex @file{i386-stub.c}
16556 For Intel 386 and compatible architectures.
16559 @cindex @file{m68k-stub.c}
16560 @cindex Motorola 680x0
16562 For Motorola 680x0 architectures.
16565 @cindex @file{sh-stub.c}
16568 For Renesas SH architectures.
16571 @cindex @file{sparc-stub.c}
16573 For @sc{sparc} architectures.
16575 @item sparcl-stub.c
16576 @cindex @file{sparcl-stub.c}
16579 For Fujitsu @sc{sparclite} architectures.
16583 The @file{README} file in the @value{GDBN} distribution may list other
16584 recently added stubs.
16587 * Stub Contents:: What the stub can do for you
16588 * Bootstrapping:: What you must do for the stub
16589 * Debug Session:: Putting it all together
16592 @node Stub Contents
16593 @subsection What the Stub Can Do for You
16595 @cindex remote serial stub
16596 The debugging stub for your architecture supplies these three
16600 @item set_debug_traps
16601 @findex set_debug_traps
16602 @cindex remote serial stub, initialization
16603 This routine arranges for @code{handle_exception} to run when your
16604 program stops. You must call this subroutine explicitly near the
16605 beginning of your program.
16607 @item handle_exception
16608 @findex handle_exception
16609 @cindex remote serial stub, main routine
16610 This is the central workhorse, but your program never calls it
16611 explicitly---the setup code arranges for @code{handle_exception} to
16612 run when a trap is triggered.
16614 @code{handle_exception} takes control when your program stops during
16615 execution (for example, on a breakpoint), and mediates communications
16616 with @value{GDBN} on the host machine. This is where the communications
16617 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16618 representative on the target machine. It begins by sending summary
16619 information on the state of your program, then continues to execute,
16620 retrieving and transmitting any information @value{GDBN} needs, until you
16621 execute a @value{GDBN} command that makes your program resume; at that point,
16622 @code{handle_exception} returns control to your own code on the target
16626 @cindex @code{breakpoint} subroutine, remote
16627 Use this auxiliary subroutine to make your program contain a
16628 breakpoint. Depending on the particular situation, this may be the only
16629 way for @value{GDBN} to get control. For instance, if your target
16630 machine has some sort of interrupt button, you won't need to call this;
16631 pressing the interrupt button transfers control to
16632 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16633 simply receiving characters on the serial port may also trigger a trap;
16634 again, in that situation, you don't need to call @code{breakpoint} from
16635 your own program---simply running @samp{target remote} from the host
16636 @value{GDBN} session gets control.
16638 Call @code{breakpoint} if none of these is true, or if you simply want
16639 to make certain your program stops at a predetermined point for the
16640 start of your debugging session.
16643 @node Bootstrapping
16644 @subsection What You Must Do for the Stub
16646 @cindex remote stub, support routines
16647 The debugging stubs that come with @value{GDBN} are set up for a particular
16648 chip architecture, but they have no information about the rest of your
16649 debugging target machine.
16651 First of all you need to tell the stub how to communicate with the
16655 @item int getDebugChar()
16656 @findex getDebugChar
16657 Write this subroutine to read a single character from the serial port.
16658 It may be identical to @code{getchar} for your target system; a
16659 different name is used to allow you to distinguish the two if you wish.
16661 @item void putDebugChar(int)
16662 @findex putDebugChar
16663 Write this subroutine to write a single character to the serial port.
16664 It may be identical to @code{putchar} for your target system; a
16665 different name is used to allow you to distinguish the two if you wish.
16668 @cindex control C, and remote debugging
16669 @cindex interrupting remote targets
16670 If you want @value{GDBN} to be able to stop your program while it is
16671 running, you need to use an interrupt-driven serial driver, and arrange
16672 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16673 character). That is the character which @value{GDBN} uses to tell the
16674 remote system to stop.
16676 Getting the debugging target to return the proper status to @value{GDBN}
16677 probably requires changes to the standard stub; one quick and dirty way
16678 is to just execute a breakpoint instruction (the ``dirty'' part is that
16679 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16681 Other routines you need to supply are:
16684 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16685 @findex exceptionHandler
16686 Write this function to install @var{exception_address} in the exception
16687 handling tables. You need to do this because the stub does not have any
16688 way of knowing what the exception handling tables on your target system
16689 are like (for example, the processor's table might be in @sc{rom},
16690 containing entries which point to a table in @sc{ram}).
16691 @var{exception_number} is the exception number which should be changed;
16692 its meaning is architecture-dependent (for example, different numbers
16693 might represent divide by zero, misaligned access, etc). When this
16694 exception occurs, control should be transferred directly to
16695 @var{exception_address}, and the processor state (stack, registers,
16696 and so on) should be just as it is when a processor exception occurs. So if
16697 you want to use a jump instruction to reach @var{exception_address}, it
16698 should be a simple jump, not a jump to subroutine.
16700 For the 386, @var{exception_address} should be installed as an interrupt
16701 gate so that interrupts are masked while the handler runs. The gate
16702 should be at privilege level 0 (the most privileged level). The
16703 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16704 help from @code{exceptionHandler}.
16706 @item void flush_i_cache()
16707 @findex flush_i_cache
16708 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16709 instruction cache, if any, on your target machine. If there is no
16710 instruction cache, this subroutine may be a no-op.
16712 On target machines that have instruction caches, @value{GDBN} requires this
16713 function to make certain that the state of your program is stable.
16717 You must also make sure this library routine is available:
16720 @item void *memset(void *, int, int)
16722 This is the standard library function @code{memset} that sets an area of
16723 memory to a known value. If you have one of the free versions of
16724 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16725 either obtain it from your hardware manufacturer, or write your own.
16728 If you do not use the GNU C compiler, you may need other standard
16729 library subroutines as well; this varies from one stub to another,
16730 but in general the stubs are likely to use any of the common library
16731 subroutines which @code{@value{NGCC}} generates as inline code.
16734 @node Debug Session
16735 @subsection Putting it All Together
16737 @cindex remote serial debugging summary
16738 In summary, when your program is ready to debug, you must follow these
16743 Make sure you have defined the supporting low-level routines
16744 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16746 @code{getDebugChar}, @code{putDebugChar},
16747 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16751 Insert these lines near the top of your program:
16759 For the 680x0 stub only, you need to provide a variable called
16760 @code{exceptionHook}. Normally you just use:
16763 void (*exceptionHook)() = 0;
16767 but if before calling @code{set_debug_traps}, you set it to point to a
16768 function in your program, that function is called when
16769 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
16770 error). The function indicated by @code{exceptionHook} is called with
16771 one parameter: an @code{int} which is the exception number.
16774 Compile and link together: your program, the @value{GDBN} debugging stub for
16775 your target architecture, and the supporting subroutines.
16778 Make sure you have a serial connection between your target machine and
16779 the @value{GDBN} host, and identify the serial port on the host.
16782 @c The "remote" target now provides a `load' command, so we should
16783 @c document that. FIXME.
16784 Download your program to your target machine (or get it there by
16785 whatever means the manufacturer provides), and start it.
16788 Start @value{GDBN} on the host, and connect to the target
16789 (@pxref{Connecting,,Connecting to a Remote Target}).
16793 @node Configurations
16794 @chapter Configuration-Specific Information
16796 While nearly all @value{GDBN} commands are available for all native and
16797 cross versions of the debugger, there are some exceptions. This chapter
16798 describes things that are only available in certain configurations.
16800 There are three major categories of configurations: native
16801 configurations, where the host and target are the same, embedded
16802 operating system configurations, which are usually the same for several
16803 different processor architectures, and bare embedded processors, which
16804 are quite different from each other.
16809 * Embedded Processors::
16816 This section describes details specific to particular native
16821 * BSD libkvm Interface:: Debugging BSD kernel memory images
16822 * SVR4 Process Information:: SVR4 process information
16823 * DJGPP Native:: Features specific to the DJGPP port
16824 * Cygwin Native:: Features specific to the Cygwin port
16825 * Hurd Native:: Features specific to @sc{gnu} Hurd
16826 * Neutrino:: Features specific to QNX Neutrino
16827 * Darwin:: Features specific to Darwin
16833 On HP-UX systems, if you refer to a function or variable name that
16834 begins with a dollar sign, @value{GDBN} searches for a user or system
16835 name first, before it searches for a convenience variable.
16838 @node BSD libkvm Interface
16839 @subsection BSD libkvm Interface
16842 @cindex kernel memory image
16843 @cindex kernel crash dump
16845 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
16846 interface that provides a uniform interface for accessing kernel virtual
16847 memory images, including live systems and crash dumps. @value{GDBN}
16848 uses this interface to allow you to debug live kernels and kernel crash
16849 dumps on many native BSD configurations. This is implemented as a
16850 special @code{kvm} debugging target. For debugging a live system, load
16851 the currently running kernel into @value{GDBN} and connect to the
16855 (@value{GDBP}) @b{target kvm}
16858 For debugging crash dumps, provide the file name of the crash dump as an
16862 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
16865 Once connected to the @code{kvm} target, the following commands are
16871 Set current context from the @dfn{Process Control Block} (PCB) address.
16874 Set current context from proc address. This command isn't available on
16875 modern FreeBSD systems.
16878 @node SVR4 Process Information
16879 @subsection SVR4 Process Information
16881 @cindex examine process image
16882 @cindex process info via @file{/proc}
16884 Many versions of SVR4 and compatible systems provide a facility called
16885 @samp{/proc} that can be used to examine the image of a running
16886 process using file-system subroutines. If @value{GDBN} is configured
16887 for an operating system with this facility, the command @code{info
16888 proc} is available to report information about the process running
16889 your program, or about any process running on your system. @code{info
16890 proc} works only on SVR4 systems that include the @code{procfs} code.
16891 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
16892 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
16898 @itemx info proc @var{process-id}
16899 Summarize available information about any running process. If a
16900 process ID is specified by @var{process-id}, display information about
16901 that process; otherwise display information about the program being
16902 debugged. The summary includes the debugged process ID, the command
16903 line used to invoke it, its current working directory, and its
16904 executable file's absolute file name.
16906 On some systems, @var{process-id} can be of the form
16907 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
16908 within a process. If the optional @var{pid} part is missing, it means
16909 a thread from the process being debugged (the leading @samp{/} still
16910 needs to be present, or else @value{GDBN} will interpret the number as
16911 a process ID rather than a thread ID).
16913 @item info proc mappings
16914 @cindex memory address space mappings
16915 Report the memory address space ranges accessible in the program, with
16916 information on whether the process has read, write, or execute access
16917 rights to each range. On @sc{gnu}/Linux systems, each memory range
16918 includes the object file which is mapped to that range, instead of the
16919 memory access rights to that range.
16921 @item info proc stat
16922 @itemx info proc status
16923 @cindex process detailed status information
16924 These subcommands are specific to @sc{gnu}/Linux systems. They show
16925 the process-related information, including the user ID and group ID;
16926 how many threads are there in the process; its virtual memory usage;
16927 the signals that are pending, blocked, and ignored; its TTY; its
16928 consumption of system and user time; its stack size; its @samp{nice}
16929 value; etc. For more information, see the @samp{proc} man page
16930 (type @kbd{man 5 proc} from your shell prompt).
16932 @item info proc all
16933 Show all the information about the process described under all of the
16934 above @code{info proc} subcommands.
16937 @comment These sub-options of 'info proc' were not included when
16938 @comment procfs.c was re-written. Keep their descriptions around
16939 @comment against the day when someone finds the time to put them back in.
16940 @kindex info proc times
16941 @item info proc times
16942 Starting time, user CPU time, and system CPU time for your program and
16945 @kindex info proc id
16947 Report on the process IDs related to your program: its own process ID,
16948 the ID of its parent, the process group ID, and the session ID.
16951 @item set procfs-trace
16952 @kindex set procfs-trace
16953 @cindex @code{procfs} API calls
16954 This command enables and disables tracing of @code{procfs} API calls.
16956 @item show procfs-trace
16957 @kindex show procfs-trace
16958 Show the current state of @code{procfs} API call tracing.
16960 @item set procfs-file @var{file}
16961 @kindex set procfs-file
16962 Tell @value{GDBN} to write @code{procfs} API trace to the named
16963 @var{file}. @value{GDBN} appends the trace info to the previous
16964 contents of the file. The default is to display the trace on the
16967 @item show procfs-file
16968 @kindex show procfs-file
16969 Show the file to which @code{procfs} API trace is written.
16971 @item proc-trace-entry
16972 @itemx proc-trace-exit
16973 @itemx proc-untrace-entry
16974 @itemx proc-untrace-exit
16975 @kindex proc-trace-entry
16976 @kindex proc-trace-exit
16977 @kindex proc-untrace-entry
16978 @kindex proc-untrace-exit
16979 These commands enable and disable tracing of entries into and exits
16980 from the @code{syscall} interface.
16983 @kindex info pidlist
16984 @cindex process list, QNX Neutrino
16985 For QNX Neutrino only, this command displays the list of all the
16986 processes and all the threads within each process.
16989 @kindex info meminfo
16990 @cindex mapinfo list, QNX Neutrino
16991 For QNX Neutrino only, this command displays the list of all mapinfos.
16995 @subsection Features for Debugging @sc{djgpp} Programs
16996 @cindex @sc{djgpp} debugging
16997 @cindex native @sc{djgpp} debugging
16998 @cindex MS-DOS-specific commands
17001 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17002 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17003 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17004 top of real-mode DOS systems and their emulations.
17006 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17007 defines a few commands specific to the @sc{djgpp} port. This
17008 subsection describes those commands.
17013 This is a prefix of @sc{djgpp}-specific commands which print
17014 information about the target system and important OS structures.
17017 @cindex MS-DOS system info
17018 @cindex free memory information (MS-DOS)
17019 @item info dos sysinfo
17020 This command displays assorted information about the underlying
17021 platform: the CPU type and features, the OS version and flavor, the
17022 DPMI version, and the available conventional and DPMI memory.
17027 @cindex segment descriptor tables
17028 @cindex descriptor tables display
17030 @itemx info dos ldt
17031 @itemx info dos idt
17032 These 3 commands display entries from, respectively, Global, Local,
17033 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17034 tables are data structures which store a descriptor for each segment
17035 that is currently in use. The segment's selector is an index into a
17036 descriptor table; the table entry for that index holds the
17037 descriptor's base address and limit, and its attributes and access
17040 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17041 segment (used for both data and the stack), and a DOS segment (which
17042 allows access to DOS/BIOS data structures and absolute addresses in
17043 conventional memory). However, the DPMI host will usually define
17044 additional segments in order to support the DPMI environment.
17046 @cindex garbled pointers
17047 These commands allow to display entries from the descriptor tables.
17048 Without an argument, all entries from the specified table are
17049 displayed. An argument, which should be an integer expression, means
17050 display a single entry whose index is given by the argument. For
17051 example, here's a convenient way to display information about the
17052 debugged program's data segment:
17055 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17056 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17060 This comes in handy when you want to see whether a pointer is outside
17061 the data segment's limit (i.e.@: @dfn{garbled}).
17063 @cindex page tables display (MS-DOS)
17065 @itemx info dos pte
17066 These two commands display entries from, respectively, the Page
17067 Directory and the Page Tables. Page Directories and Page Tables are
17068 data structures which control how virtual memory addresses are mapped
17069 into physical addresses. A Page Table includes an entry for every
17070 page of memory that is mapped into the program's address space; there
17071 may be several Page Tables, each one holding up to 4096 entries. A
17072 Page Directory has up to 4096 entries, one each for every Page Table
17073 that is currently in use.
17075 Without an argument, @kbd{info dos pde} displays the entire Page
17076 Directory, and @kbd{info dos pte} displays all the entries in all of
17077 the Page Tables. An argument, an integer expression, given to the
17078 @kbd{info dos pde} command means display only that entry from the Page
17079 Directory table. An argument given to the @kbd{info dos pte} command
17080 means display entries from a single Page Table, the one pointed to by
17081 the specified entry in the Page Directory.
17083 @cindex direct memory access (DMA) on MS-DOS
17084 These commands are useful when your program uses @dfn{DMA} (Direct
17085 Memory Access), which needs physical addresses to program the DMA
17088 These commands are supported only with some DPMI servers.
17090 @cindex physical address from linear address
17091 @item info dos address-pte @var{addr}
17092 This command displays the Page Table entry for a specified linear
17093 address. The argument @var{addr} is a linear address which should
17094 already have the appropriate segment's base address added to it,
17095 because this command accepts addresses which may belong to @emph{any}
17096 segment. For example, here's how to display the Page Table entry for
17097 the page where a variable @code{i} is stored:
17100 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17101 @exdent @code{Page Table entry for address 0x11a00d30:}
17102 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17106 This says that @code{i} is stored at offset @code{0xd30} from the page
17107 whose physical base address is @code{0x02698000}, and shows all the
17108 attributes of that page.
17110 Note that you must cast the addresses of variables to a @code{char *},
17111 since otherwise the value of @code{__djgpp_base_address}, the base
17112 address of all variables and functions in a @sc{djgpp} program, will
17113 be added using the rules of C pointer arithmetics: if @code{i} is
17114 declared an @code{int}, @value{GDBN} will add 4 times the value of
17115 @code{__djgpp_base_address} to the address of @code{i}.
17117 Here's another example, it displays the Page Table entry for the
17121 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17122 @exdent @code{Page Table entry for address 0x29110:}
17123 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17127 (The @code{+ 3} offset is because the transfer buffer's address is the
17128 3rd member of the @code{_go32_info_block} structure.) The output
17129 clearly shows that this DPMI server maps the addresses in conventional
17130 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17131 linear (@code{0x29110}) addresses are identical.
17133 This command is supported only with some DPMI servers.
17136 @cindex DOS serial data link, remote debugging
17137 In addition to native debugging, the DJGPP port supports remote
17138 debugging via a serial data link. The following commands are specific
17139 to remote serial debugging in the DJGPP port of @value{GDBN}.
17142 @kindex set com1base
17143 @kindex set com1irq
17144 @kindex set com2base
17145 @kindex set com2irq
17146 @kindex set com3base
17147 @kindex set com3irq
17148 @kindex set com4base
17149 @kindex set com4irq
17150 @item set com1base @var{addr}
17151 This command sets the base I/O port address of the @file{COM1} serial
17154 @item set com1irq @var{irq}
17155 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17156 for the @file{COM1} serial port.
17158 There are similar commands @samp{set com2base}, @samp{set com3irq},
17159 etc.@: for setting the port address and the @code{IRQ} lines for the
17162 @kindex show com1base
17163 @kindex show com1irq
17164 @kindex show com2base
17165 @kindex show com2irq
17166 @kindex show com3base
17167 @kindex show com3irq
17168 @kindex show com4base
17169 @kindex show com4irq
17170 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17171 display the current settings of the base address and the @code{IRQ}
17172 lines used by the COM ports.
17175 @kindex info serial
17176 @cindex DOS serial port status
17177 This command prints the status of the 4 DOS serial ports. For each
17178 port, it prints whether it's active or not, its I/O base address and
17179 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17180 counts of various errors encountered so far.
17184 @node Cygwin Native
17185 @subsection Features for Debugging MS Windows PE Executables
17186 @cindex MS Windows debugging
17187 @cindex native Cygwin debugging
17188 @cindex Cygwin-specific commands
17190 @value{GDBN} supports native debugging of MS Windows programs, including
17191 DLLs with and without symbolic debugging information.
17193 @cindex Ctrl-BREAK, MS-Windows
17194 @cindex interrupt debuggee on MS-Windows
17195 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17196 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17197 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17198 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17199 sequence, which can be used to interrupt the debuggee even if it
17202 There are various additional Cygwin-specific commands, described in
17203 this section. Working with DLLs that have no debugging symbols is
17204 described in @ref{Non-debug DLL Symbols}.
17209 This is a prefix of MS Windows-specific commands which print
17210 information about the target system and important OS structures.
17212 @item info w32 selector
17213 This command displays information returned by
17214 the Win32 API @code{GetThreadSelectorEntry} function.
17215 It takes an optional argument that is evaluated to
17216 a long value to give the information about this given selector.
17217 Without argument, this command displays information
17218 about the six segment registers.
17220 @item info w32 thread-information-block
17221 This command displays thread specific information stored in the
17222 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17223 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17227 This is a Cygwin-specific alias of @code{info shared}.
17229 @kindex dll-symbols
17231 This command loads symbols from a dll similarly to
17232 add-sym command but without the need to specify a base address.
17234 @kindex set cygwin-exceptions
17235 @cindex debugging the Cygwin DLL
17236 @cindex Cygwin DLL, debugging
17237 @item set cygwin-exceptions @var{mode}
17238 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17239 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17240 @value{GDBN} will delay recognition of exceptions, and may ignore some
17241 exceptions which seem to be caused by internal Cygwin DLL
17242 ``bookkeeping''. This option is meant primarily for debugging the
17243 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17244 @value{GDBN} users with false @code{SIGSEGV} signals.
17246 @kindex show cygwin-exceptions
17247 @item show cygwin-exceptions
17248 Displays whether @value{GDBN} will break on exceptions that happen
17249 inside the Cygwin DLL itself.
17251 @kindex set new-console
17252 @item set new-console @var{mode}
17253 If @var{mode} is @code{on} the debuggee will
17254 be started in a new console on next start.
17255 If @var{mode} is @code{off}, the debuggee will
17256 be started in the same console as the debugger.
17258 @kindex show new-console
17259 @item show new-console
17260 Displays whether a new console is used
17261 when the debuggee is started.
17263 @kindex set new-group
17264 @item set new-group @var{mode}
17265 This boolean value controls whether the debuggee should
17266 start a new group or stay in the same group as the debugger.
17267 This affects the way the Windows OS handles
17270 @kindex show new-group
17271 @item show new-group
17272 Displays current value of new-group boolean.
17274 @kindex set debugevents
17275 @item set debugevents
17276 This boolean value adds debug output concerning kernel events related
17277 to the debuggee seen by the debugger. This includes events that
17278 signal thread and process creation and exit, DLL loading and
17279 unloading, console interrupts, and debugging messages produced by the
17280 Windows @code{OutputDebugString} API call.
17282 @kindex set debugexec
17283 @item set debugexec
17284 This boolean value adds debug output concerning execute events
17285 (such as resume thread) seen by the debugger.
17287 @kindex set debugexceptions
17288 @item set debugexceptions
17289 This boolean value adds debug output concerning exceptions in the
17290 debuggee seen by the debugger.
17292 @kindex set debugmemory
17293 @item set debugmemory
17294 This boolean value adds debug output concerning debuggee memory reads
17295 and writes by the debugger.
17299 This boolean values specifies whether the debuggee is called
17300 via a shell or directly (default value is on).
17304 Displays if the debuggee will be started with a shell.
17309 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17312 @node Non-debug DLL Symbols
17313 @subsubsection Support for DLLs without Debugging Symbols
17314 @cindex DLLs with no debugging symbols
17315 @cindex Minimal symbols and DLLs
17317 Very often on windows, some of the DLLs that your program relies on do
17318 not include symbolic debugging information (for example,
17319 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17320 symbols in a DLL, it relies on the minimal amount of symbolic
17321 information contained in the DLL's export table. This section
17322 describes working with such symbols, known internally to @value{GDBN} as
17323 ``minimal symbols''.
17325 Note that before the debugged program has started execution, no DLLs
17326 will have been loaded. The easiest way around this problem is simply to
17327 start the program --- either by setting a breakpoint or letting the
17328 program run once to completion. It is also possible to force
17329 @value{GDBN} to load a particular DLL before starting the executable ---
17330 see the shared library information in @ref{Files}, or the
17331 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17332 explicitly loading symbols from a DLL with no debugging information will
17333 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17334 which may adversely affect symbol lookup performance.
17336 @subsubsection DLL Name Prefixes
17338 In keeping with the naming conventions used by the Microsoft debugging
17339 tools, DLL export symbols are made available with a prefix based on the
17340 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17341 also entered into the symbol table, so @code{CreateFileA} is often
17342 sufficient. In some cases there will be name clashes within a program
17343 (particularly if the executable itself includes full debugging symbols)
17344 necessitating the use of the fully qualified name when referring to the
17345 contents of the DLL. Use single-quotes around the name to avoid the
17346 exclamation mark (``!'') being interpreted as a language operator.
17348 Note that the internal name of the DLL may be all upper-case, even
17349 though the file name of the DLL is lower-case, or vice-versa. Since
17350 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17351 some confusion. If in doubt, try the @code{info functions} and
17352 @code{info variables} commands or even @code{maint print msymbols}
17353 (@pxref{Symbols}). Here's an example:
17356 (@value{GDBP}) info function CreateFileA
17357 All functions matching regular expression "CreateFileA":
17359 Non-debugging symbols:
17360 0x77e885f4 CreateFileA
17361 0x77e885f4 KERNEL32!CreateFileA
17365 (@value{GDBP}) info function !
17366 All functions matching regular expression "!":
17368 Non-debugging symbols:
17369 0x6100114c cygwin1!__assert
17370 0x61004034 cygwin1!_dll_crt0@@0
17371 0x61004240 cygwin1!dll_crt0(per_process *)
17375 @subsubsection Working with Minimal Symbols
17377 Symbols extracted from a DLL's export table do not contain very much
17378 type information. All that @value{GDBN} can do is guess whether a symbol
17379 refers to a function or variable depending on the linker section that
17380 contains the symbol. Also note that the actual contents of the memory
17381 contained in a DLL are not available unless the program is running. This
17382 means that you cannot examine the contents of a variable or disassemble
17383 a function within a DLL without a running program.
17385 Variables are generally treated as pointers and dereferenced
17386 automatically. For this reason, it is often necessary to prefix a
17387 variable name with the address-of operator (``&'') and provide explicit
17388 type information in the command. Here's an example of the type of
17392 (@value{GDBP}) print 'cygwin1!__argv'
17397 (@value{GDBP}) x 'cygwin1!__argv'
17398 0x10021610: "\230y\""
17401 And two possible solutions:
17404 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17405 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17409 (@value{GDBP}) x/2x &'cygwin1!__argv'
17410 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17411 (@value{GDBP}) x/x 0x10021608
17412 0x10021608: 0x0022fd98
17413 (@value{GDBP}) x/s 0x0022fd98
17414 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17417 Setting a break point within a DLL is possible even before the program
17418 starts execution. However, under these circumstances, @value{GDBN} can't
17419 examine the initial instructions of the function in order to skip the
17420 function's frame set-up code. You can work around this by using ``*&''
17421 to set the breakpoint at a raw memory address:
17424 (@value{GDBP}) break *&'python22!PyOS_Readline'
17425 Breakpoint 1 at 0x1e04eff0
17428 The author of these extensions is not entirely convinced that setting a
17429 break point within a shared DLL like @file{kernel32.dll} is completely
17433 @subsection Commands Specific to @sc{gnu} Hurd Systems
17434 @cindex @sc{gnu} Hurd debugging
17436 This subsection describes @value{GDBN} commands specific to the
17437 @sc{gnu} Hurd native debugging.
17442 @kindex set signals@r{, Hurd command}
17443 @kindex set sigs@r{, Hurd command}
17444 This command toggles the state of inferior signal interception by
17445 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17446 affected by this command. @code{sigs} is a shorthand alias for
17451 @kindex show signals@r{, Hurd command}
17452 @kindex show sigs@r{, Hurd command}
17453 Show the current state of intercepting inferior's signals.
17455 @item set signal-thread
17456 @itemx set sigthread
17457 @kindex set signal-thread
17458 @kindex set sigthread
17459 This command tells @value{GDBN} which thread is the @code{libc} signal
17460 thread. That thread is run when a signal is delivered to a running
17461 process. @code{set sigthread} is the shorthand alias of @code{set
17464 @item show signal-thread
17465 @itemx show sigthread
17466 @kindex show signal-thread
17467 @kindex show sigthread
17468 These two commands show which thread will run when the inferior is
17469 delivered a signal.
17472 @kindex set stopped@r{, Hurd command}
17473 This commands tells @value{GDBN} that the inferior process is stopped,
17474 as with the @code{SIGSTOP} signal. The stopped process can be
17475 continued by delivering a signal to it.
17478 @kindex show stopped@r{, Hurd command}
17479 This command shows whether @value{GDBN} thinks the debuggee is
17482 @item set exceptions
17483 @kindex set exceptions@r{, Hurd command}
17484 Use this command to turn off trapping of exceptions in the inferior.
17485 When exception trapping is off, neither breakpoints nor
17486 single-stepping will work. To restore the default, set exception
17489 @item show exceptions
17490 @kindex show exceptions@r{, Hurd command}
17491 Show the current state of trapping exceptions in the inferior.
17493 @item set task pause
17494 @kindex set task@r{, Hurd commands}
17495 @cindex task attributes (@sc{gnu} Hurd)
17496 @cindex pause current task (@sc{gnu} Hurd)
17497 This command toggles task suspension when @value{GDBN} has control.
17498 Setting it to on takes effect immediately, and the task is suspended
17499 whenever @value{GDBN} gets control. Setting it to off will take
17500 effect the next time the inferior is continued. If this option is set
17501 to off, you can use @code{set thread default pause on} or @code{set
17502 thread pause on} (see below) to pause individual threads.
17504 @item show task pause
17505 @kindex show task@r{, Hurd commands}
17506 Show the current state of task suspension.
17508 @item set task detach-suspend-count
17509 @cindex task suspend count
17510 @cindex detach from task, @sc{gnu} Hurd
17511 This command sets the suspend count the task will be left with when
17512 @value{GDBN} detaches from it.
17514 @item show task detach-suspend-count
17515 Show the suspend count the task will be left with when detaching.
17517 @item set task exception-port
17518 @itemx set task excp
17519 @cindex task exception port, @sc{gnu} Hurd
17520 This command sets the task exception port to which @value{GDBN} will
17521 forward exceptions. The argument should be the value of the @dfn{send
17522 rights} of the task. @code{set task excp} is a shorthand alias.
17524 @item set noninvasive
17525 @cindex noninvasive task options
17526 This command switches @value{GDBN} to a mode that is the least
17527 invasive as far as interfering with the inferior is concerned. This
17528 is the same as using @code{set task pause}, @code{set exceptions}, and
17529 @code{set signals} to values opposite to the defaults.
17531 @item info send-rights
17532 @itemx info receive-rights
17533 @itemx info port-rights
17534 @itemx info port-sets
17535 @itemx info dead-names
17538 @cindex send rights, @sc{gnu} Hurd
17539 @cindex receive rights, @sc{gnu} Hurd
17540 @cindex port rights, @sc{gnu} Hurd
17541 @cindex port sets, @sc{gnu} Hurd
17542 @cindex dead names, @sc{gnu} Hurd
17543 These commands display information about, respectively, send rights,
17544 receive rights, port rights, port sets, and dead names of a task.
17545 There are also shorthand aliases: @code{info ports} for @code{info
17546 port-rights} and @code{info psets} for @code{info port-sets}.
17548 @item set thread pause
17549 @kindex set thread@r{, Hurd command}
17550 @cindex thread properties, @sc{gnu} Hurd
17551 @cindex pause current thread (@sc{gnu} Hurd)
17552 This command toggles current thread suspension when @value{GDBN} has
17553 control. Setting it to on takes effect immediately, and the current
17554 thread is suspended whenever @value{GDBN} gets control. Setting it to
17555 off will take effect the next time the inferior is continued.
17556 Normally, this command has no effect, since when @value{GDBN} has
17557 control, the whole task is suspended. However, if you used @code{set
17558 task pause off} (see above), this command comes in handy to suspend
17559 only the current thread.
17561 @item show thread pause
17562 @kindex show thread@r{, Hurd command}
17563 This command shows the state of current thread suspension.
17565 @item set thread run
17566 This command sets whether the current thread is allowed to run.
17568 @item show thread run
17569 Show whether the current thread is allowed to run.
17571 @item set thread detach-suspend-count
17572 @cindex thread suspend count, @sc{gnu} Hurd
17573 @cindex detach from thread, @sc{gnu} Hurd
17574 This command sets the suspend count @value{GDBN} will leave on a
17575 thread when detaching. This number is relative to the suspend count
17576 found by @value{GDBN} when it notices the thread; use @code{set thread
17577 takeover-suspend-count} to force it to an absolute value.
17579 @item show thread detach-suspend-count
17580 Show the suspend count @value{GDBN} will leave on the thread when
17583 @item set thread exception-port
17584 @itemx set thread excp
17585 Set the thread exception port to which to forward exceptions. This
17586 overrides the port set by @code{set task exception-port} (see above).
17587 @code{set thread excp} is the shorthand alias.
17589 @item set thread takeover-suspend-count
17590 Normally, @value{GDBN}'s thread suspend counts are relative to the
17591 value @value{GDBN} finds when it notices each thread. This command
17592 changes the suspend counts to be absolute instead.
17594 @item set thread default
17595 @itemx show thread default
17596 @cindex thread default settings, @sc{gnu} Hurd
17597 Each of the above @code{set thread} commands has a @code{set thread
17598 default} counterpart (e.g., @code{set thread default pause}, @code{set
17599 thread default exception-port}, etc.). The @code{thread default}
17600 variety of commands sets the default thread properties for all
17601 threads; you can then change the properties of individual threads with
17602 the non-default commands.
17607 @subsection QNX Neutrino
17608 @cindex QNX Neutrino
17610 @value{GDBN} provides the following commands specific to the QNX
17614 @item set debug nto-debug
17615 @kindex set debug nto-debug
17616 When set to on, enables debugging messages specific to the QNX
17619 @item show debug nto-debug
17620 @kindex show debug nto-debug
17621 Show the current state of QNX Neutrino messages.
17628 @value{GDBN} provides the following commands specific to the Darwin target:
17631 @item set debug darwin @var{num}
17632 @kindex set debug darwin
17633 When set to a non zero value, enables debugging messages specific to
17634 the Darwin support. Higher values produce more verbose output.
17636 @item show debug darwin
17637 @kindex show debug darwin
17638 Show the current state of Darwin messages.
17640 @item set debug mach-o @var{num}
17641 @kindex set debug mach-o
17642 When set to a non zero value, enables debugging messages while
17643 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17644 file format used on Darwin for object and executable files.) Higher
17645 values produce more verbose output. This is a command to diagnose
17646 problems internal to @value{GDBN} and should not be needed in normal
17649 @item show debug mach-o
17650 @kindex show debug mach-o
17651 Show the current state of Mach-O file messages.
17653 @item set mach-exceptions on
17654 @itemx set mach-exceptions off
17655 @kindex set mach-exceptions
17656 On Darwin, faults are first reported as a Mach exception and are then
17657 mapped to a Posix signal. Use this command to turn on trapping of
17658 Mach exceptions in the inferior. This might be sometimes useful to
17659 better understand the cause of a fault. The default is off.
17661 @item show mach-exceptions
17662 @kindex show mach-exceptions
17663 Show the current state of exceptions trapping.
17668 @section Embedded Operating Systems
17670 This section describes configurations involving the debugging of
17671 embedded operating systems that are available for several different
17675 * VxWorks:: Using @value{GDBN} with VxWorks
17678 @value{GDBN} includes the ability to debug programs running on
17679 various real-time operating systems.
17682 @subsection Using @value{GDBN} with VxWorks
17688 @kindex target vxworks
17689 @item target vxworks @var{machinename}
17690 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17691 is the target system's machine name or IP address.
17695 On VxWorks, @code{load} links @var{filename} dynamically on the
17696 current target system as well as adding its symbols in @value{GDBN}.
17698 @value{GDBN} enables developers to spawn and debug tasks running on networked
17699 VxWorks targets from a Unix host. Already-running tasks spawned from
17700 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17701 both the Unix host and on the VxWorks target. The program
17702 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17703 installed with the name @code{vxgdb}, to distinguish it from a
17704 @value{GDBN} for debugging programs on the host itself.)
17707 @item VxWorks-timeout @var{args}
17708 @kindex vxworks-timeout
17709 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17710 This option is set by the user, and @var{args} represents the number of
17711 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17712 your VxWorks target is a slow software simulator or is on the far side
17713 of a thin network line.
17716 The following information on connecting to VxWorks was current when
17717 this manual was produced; newer releases of VxWorks may use revised
17720 @findex INCLUDE_RDB
17721 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17722 to include the remote debugging interface routines in the VxWorks
17723 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17724 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17725 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17726 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17727 information on configuring and remaking VxWorks, see the manufacturer's
17729 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17731 Once you have included @file{rdb.a} in your VxWorks system image and set
17732 your Unix execution search path to find @value{GDBN}, you are ready to
17733 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17734 @code{vxgdb}, depending on your installation).
17736 @value{GDBN} comes up showing the prompt:
17743 * VxWorks Connection:: Connecting to VxWorks
17744 * VxWorks Download:: VxWorks download
17745 * VxWorks Attach:: Running tasks
17748 @node VxWorks Connection
17749 @subsubsection Connecting to VxWorks
17751 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17752 network. To connect to a target whose host name is ``@code{tt}'', type:
17755 (vxgdb) target vxworks tt
17759 @value{GDBN} displays messages like these:
17762 Attaching remote machine across net...
17767 @value{GDBN} then attempts to read the symbol tables of any object modules
17768 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
17769 these files by searching the directories listed in the command search
17770 path (@pxref{Environment, ,Your Program's Environment}); if it fails
17771 to find an object file, it displays a message such as:
17774 prog.o: No such file or directory.
17777 When this happens, add the appropriate directory to the search path with
17778 the @value{GDBN} command @code{path}, and execute the @code{target}
17781 @node VxWorks Download
17782 @subsubsection VxWorks Download
17784 @cindex download to VxWorks
17785 If you have connected to the VxWorks target and you want to debug an
17786 object that has not yet been loaded, you can use the @value{GDBN}
17787 @code{load} command to download a file from Unix to VxWorks
17788 incrementally. The object file given as an argument to the @code{load}
17789 command is actually opened twice: first by the VxWorks target in order
17790 to download the code, then by @value{GDBN} in order to read the symbol
17791 table. This can lead to problems if the current working directories on
17792 the two systems differ. If both systems have NFS mounted the same
17793 filesystems, you can avoid these problems by using absolute paths.
17794 Otherwise, it is simplest to set the working directory on both systems
17795 to the directory in which the object file resides, and then to reference
17796 the file by its name, without any path. For instance, a program
17797 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
17798 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
17799 program, type this on VxWorks:
17802 -> cd "@var{vxpath}/vw/demo/rdb"
17806 Then, in @value{GDBN}, type:
17809 (vxgdb) cd @var{hostpath}/vw/demo/rdb
17810 (vxgdb) load prog.o
17813 @value{GDBN} displays a response similar to this:
17816 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
17819 You can also use the @code{load} command to reload an object module
17820 after editing and recompiling the corresponding source file. Note that
17821 this makes @value{GDBN} delete all currently-defined breakpoints,
17822 auto-displays, and convenience variables, and to clear the value
17823 history. (This is necessary in order to preserve the integrity of
17824 debugger's data structures that reference the target system's symbol
17827 @node VxWorks Attach
17828 @subsubsection Running Tasks
17830 @cindex running VxWorks tasks
17831 You can also attach to an existing task using the @code{attach} command as
17835 (vxgdb) attach @var{task}
17839 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
17840 or suspended when you attach to it. Running tasks are suspended at
17841 the time of attachment.
17843 @node Embedded Processors
17844 @section Embedded Processors
17846 This section goes into details specific to particular embedded
17849 @cindex send command to simulator
17850 Whenever a specific embedded processor has a simulator, @value{GDBN}
17851 allows to send an arbitrary command to the simulator.
17854 @item sim @var{command}
17855 @kindex sim@r{, a command}
17856 Send an arbitrary @var{command} string to the simulator. Consult the
17857 documentation for the specific simulator in use for information about
17858 acceptable commands.
17864 * M32R/D:: Renesas M32R/D
17865 * M68K:: Motorola M68K
17866 * MicroBlaze:: Xilinx MicroBlaze
17867 * MIPS Embedded:: MIPS Embedded
17868 * OpenRISC 1000:: OpenRisc 1000
17869 * PA:: HP PA Embedded
17870 * PowerPC Embedded:: PowerPC Embedded
17871 * Sparclet:: Tsqware Sparclet
17872 * Sparclite:: Fujitsu Sparclite
17873 * Z8000:: Zilog Z8000
17876 * Super-H:: Renesas Super-H
17885 @item target rdi @var{dev}
17886 ARM Angel monitor, via RDI library interface to ADP protocol. You may
17887 use this target to communicate with both boards running the Angel
17888 monitor, or with the EmbeddedICE JTAG debug device.
17891 @item target rdp @var{dev}
17896 @value{GDBN} provides the following ARM-specific commands:
17899 @item set arm disassembler
17901 This commands selects from a list of disassembly styles. The
17902 @code{"std"} style is the standard style.
17904 @item show arm disassembler
17906 Show the current disassembly style.
17908 @item set arm apcs32
17909 @cindex ARM 32-bit mode
17910 This command toggles ARM operation mode between 32-bit and 26-bit.
17912 @item show arm apcs32
17913 Display the current usage of the ARM 32-bit mode.
17915 @item set arm fpu @var{fputype}
17916 This command sets the ARM floating-point unit (FPU) type. The
17917 argument @var{fputype} can be one of these:
17921 Determine the FPU type by querying the OS ABI.
17923 Software FPU, with mixed-endian doubles on little-endian ARM
17926 GCC-compiled FPA co-processor.
17928 Software FPU with pure-endian doubles.
17934 Show the current type of the FPU.
17937 This command forces @value{GDBN} to use the specified ABI.
17940 Show the currently used ABI.
17942 @item set arm fallback-mode (arm|thumb|auto)
17943 @value{GDBN} uses the symbol table, when available, to determine
17944 whether instructions are ARM or Thumb. This command controls
17945 @value{GDBN}'s default behavior when the symbol table is not
17946 available. The default is @samp{auto}, which causes @value{GDBN} to
17947 use the current execution mode (from the @code{T} bit in the @code{CPSR}
17950 @item show arm fallback-mode
17951 Show the current fallback instruction mode.
17953 @item set arm force-mode (arm|thumb|auto)
17954 This command overrides use of the symbol table to determine whether
17955 instructions are ARM or Thumb. The default is @samp{auto}, which
17956 causes @value{GDBN} to use the symbol table and then the setting
17957 of @samp{set arm fallback-mode}.
17959 @item show arm force-mode
17960 Show the current forced instruction mode.
17962 @item set debug arm
17963 Toggle whether to display ARM-specific debugging messages from the ARM
17964 target support subsystem.
17966 @item show debug arm
17967 Show whether ARM-specific debugging messages are enabled.
17970 The following commands are available when an ARM target is debugged
17971 using the RDI interface:
17974 @item rdilogfile @r{[}@var{file}@r{]}
17976 @cindex ADP (Angel Debugger Protocol) logging
17977 Set the filename for the ADP (Angel Debugger Protocol) packet log.
17978 With an argument, sets the log file to the specified @var{file}. With
17979 no argument, show the current log file name. The default log file is
17982 @item rdilogenable @r{[}@var{arg}@r{]}
17983 @kindex rdilogenable
17984 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
17985 enables logging, with an argument 0 or @code{"no"} disables it. With
17986 no arguments displays the current setting. When logging is enabled,
17987 ADP packets exchanged between @value{GDBN} and the RDI target device
17988 are logged to a file.
17990 @item set rdiromatzero
17991 @kindex set rdiromatzero
17992 @cindex ROM at zero address, RDI
17993 Tell @value{GDBN} whether the target has ROM at address 0. If on,
17994 vector catching is disabled, so that zero address can be used. If off
17995 (the default), vector catching is enabled. For this command to take
17996 effect, it needs to be invoked prior to the @code{target rdi} command.
17998 @item show rdiromatzero
17999 @kindex show rdiromatzero
18000 Show the current setting of ROM at zero address.
18002 @item set rdiheartbeat
18003 @kindex set rdiheartbeat
18004 @cindex RDI heartbeat
18005 Enable or disable RDI heartbeat packets. It is not recommended to
18006 turn on this option, since it confuses ARM and EPI JTAG interface, as
18007 well as the Angel monitor.
18009 @item show rdiheartbeat
18010 @kindex show rdiheartbeat
18011 Show the setting of RDI heartbeat packets.
18015 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18016 The @value{GDBN} ARM simulator accepts the following optional arguments.
18019 @item --swi-support=@var{type}
18020 Tell the simulator which SWI interfaces to support.
18021 @var{type} may be a comma separated list of the following values.
18022 The default value is @code{all}.
18035 @subsection Renesas M32R/D and M32R/SDI
18038 @kindex target m32r
18039 @item target m32r @var{dev}
18040 Renesas M32R/D ROM monitor.
18042 @kindex target m32rsdi
18043 @item target m32rsdi @var{dev}
18044 Renesas M32R SDI server, connected via parallel port to the board.
18047 The following @value{GDBN} commands are specific to the M32R monitor:
18050 @item set download-path @var{path}
18051 @kindex set download-path
18052 @cindex find downloadable @sc{srec} files (M32R)
18053 Set the default path for finding downloadable @sc{srec} files.
18055 @item show download-path
18056 @kindex show download-path
18057 Show the default path for downloadable @sc{srec} files.
18059 @item set board-address @var{addr}
18060 @kindex set board-address
18061 @cindex M32-EVA target board address
18062 Set the IP address for the M32R-EVA target board.
18064 @item show board-address
18065 @kindex show board-address
18066 Show the current IP address of the target board.
18068 @item set server-address @var{addr}
18069 @kindex set server-address
18070 @cindex download server address (M32R)
18071 Set the IP address for the download server, which is the @value{GDBN}'s
18074 @item show server-address
18075 @kindex show server-address
18076 Display the IP address of the download server.
18078 @item upload @r{[}@var{file}@r{]}
18079 @kindex upload@r{, M32R}
18080 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18081 upload capability. If no @var{file} argument is given, the current
18082 executable file is uploaded.
18084 @item tload @r{[}@var{file}@r{]}
18085 @kindex tload@r{, M32R}
18086 Test the @code{upload} command.
18089 The following commands are available for M32R/SDI:
18094 @cindex reset SDI connection, M32R
18095 This command resets the SDI connection.
18099 This command shows the SDI connection status.
18102 @kindex debug_chaos
18103 @cindex M32R/Chaos debugging
18104 Instructs the remote that M32R/Chaos debugging is to be used.
18106 @item use_debug_dma
18107 @kindex use_debug_dma
18108 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18111 @kindex use_mon_code
18112 Instructs the remote to use the MON_CODE method of accessing memory.
18115 @kindex use_ib_break
18116 Instructs the remote to set breakpoints by IB break.
18118 @item use_dbt_break
18119 @kindex use_dbt_break
18120 Instructs the remote to set breakpoints by DBT.
18126 The Motorola m68k configuration includes ColdFire support, and a
18127 target command for the following ROM monitor.
18131 @kindex target dbug
18132 @item target dbug @var{dev}
18133 dBUG ROM monitor for Motorola ColdFire.
18138 @subsection MicroBlaze
18139 @cindex Xilinx MicroBlaze
18140 @cindex XMD, Xilinx Microprocessor Debugger
18142 The MicroBlaze is a soft-core processor supported on various Xilinx
18143 FPGAs, such as Spartan or Virtex series. Boards with these processors
18144 usually have JTAG ports which connect to a host system running the Xilinx
18145 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18146 This host system is used to download the configuration bitstream to
18147 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18148 communicates with the target board using the JTAG interface and
18149 presents a @code{gdbserver} interface to the board. By default
18150 @code{xmd} uses port @code{1234}. (While it is possible to change
18151 this default port, it requires the use of undocumented @code{xmd}
18152 commands. Contact Xilinx support if you need to do this.)
18154 Use these GDB commands to connect to the MicroBlaze target processor.
18157 @item target remote :1234
18158 Use this command to connect to the target if you are running @value{GDBN}
18159 on the same system as @code{xmd}.
18161 @item target remote @var{xmd-host}:1234
18162 Use this command to connect to the target if it is connected to @code{xmd}
18163 running on a different system named @var{xmd-host}.
18166 Use this command to download a program to the MicroBlaze target.
18168 @item set debug microblaze @var{n}
18169 Enable MicroBlaze-specific debugging messages if non-zero.
18171 @item show debug microblaze @var{n}
18172 Show MicroBlaze-specific debugging level.
18175 @node MIPS Embedded
18176 @subsection MIPS Embedded
18178 @cindex MIPS boards
18179 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18180 MIPS board attached to a serial line. This is available when
18181 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18184 Use these @value{GDBN} commands to specify the connection to your target board:
18187 @item target mips @var{port}
18188 @kindex target mips @var{port}
18189 To run a program on the board, start up @code{@value{GDBP}} with the
18190 name of your program as the argument. To connect to the board, use the
18191 command @samp{target mips @var{port}}, where @var{port} is the name of
18192 the serial port connected to the board. If the program has not already
18193 been downloaded to the board, you may use the @code{load} command to
18194 download it. You can then use all the usual @value{GDBN} commands.
18196 For example, this sequence connects to the target board through a serial
18197 port, and loads and runs a program called @var{prog} through the
18201 host$ @value{GDBP} @var{prog}
18202 @value{GDBN} is free software and @dots{}
18203 (@value{GDBP}) target mips /dev/ttyb
18204 (@value{GDBP}) load @var{prog}
18208 @item target mips @var{hostname}:@var{portnumber}
18209 On some @value{GDBN} host configurations, you can specify a TCP
18210 connection (for instance, to a serial line managed by a terminal
18211 concentrator) instead of a serial port, using the syntax
18212 @samp{@var{hostname}:@var{portnumber}}.
18214 @item target pmon @var{port}
18215 @kindex target pmon @var{port}
18218 @item target ddb @var{port}
18219 @kindex target ddb @var{port}
18220 NEC's DDB variant of PMON for Vr4300.
18222 @item target lsi @var{port}
18223 @kindex target lsi @var{port}
18224 LSI variant of PMON.
18226 @kindex target r3900
18227 @item target r3900 @var{dev}
18228 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18230 @kindex target array
18231 @item target array @var{dev}
18232 Array Tech LSI33K RAID controller board.
18238 @value{GDBN} also supports these special commands for MIPS targets:
18241 @item set mipsfpu double
18242 @itemx set mipsfpu single
18243 @itemx set mipsfpu none
18244 @itemx set mipsfpu auto
18245 @itemx show mipsfpu
18246 @kindex set mipsfpu
18247 @kindex show mipsfpu
18248 @cindex MIPS remote floating point
18249 @cindex floating point, MIPS remote
18250 If your target board does not support the MIPS floating point
18251 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18252 need this, you may wish to put the command in your @value{GDBN} init
18253 file). This tells @value{GDBN} how to find the return value of
18254 functions which return floating point values. It also allows
18255 @value{GDBN} to avoid saving the floating point registers when calling
18256 functions on the board. If you are using a floating point coprocessor
18257 with only single precision floating point support, as on the @sc{r4650}
18258 processor, use the command @samp{set mipsfpu single}. The default
18259 double precision floating point coprocessor may be selected using
18260 @samp{set mipsfpu double}.
18262 In previous versions the only choices were double precision or no
18263 floating point, so @samp{set mipsfpu on} will select double precision
18264 and @samp{set mipsfpu off} will select no floating point.
18266 As usual, you can inquire about the @code{mipsfpu} variable with
18267 @samp{show mipsfpu}.
18269 @item set timeout @var{seconds}
18270 @itemx set retransmit-timeout @var{seconds}
18271 @itemx show timeout
18272 @itemx show retransmit-timeout
18273 @cindex @code{timeout}, MIPS protocol
18274 @cindex @code{retransmit-timeout}, MIPS protocol
18275 @kindex set timeout
18276 @kindex show timeout
18277 @kindex set retransmit-timeout
18278 @kindex show retransmit-timeout
18279 You can control the timeout used while waiting for a packet, in the MIPS
18280 remote protocol, with the @code{set timeout @var{seconds}} command. The
18281 default is 5 seconds. Similarly, you can control the timeout used while
18282 waiting for an acknowledgment of a packet with the @code{set
18283 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18284 You can inspect both values with @code{show timeout} and @code{show
18285 retransmit-timeout}. (These commands are @emph{only} available when
18286 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18288 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18289 is waiting for your program to stop. In that case, @value{GDBN} waits
18290 forever because it has no way of knowing how long the program is going
18291 to run before stopping.
18293 @item set syn-garbage-limit @var{num}
18294 @kindex set syn-garbage-limit@r{, MIPS remote}
18295 @cindex synchronize with remote MIPS target
18296 Limit the maximum number of characters @value{GDBN} should ignore when
18297 it tries to synchronize with the remote target. The default is 10
18298 characters. Setting the limit to -1 means there's no limit.
18300 @item show syn-garbage-limit
18301 @kindex show syn-garbage-limit@r{, MIPS remote}
18302 Show the current limit on the number of characters to ignore when
18303 trying to synchronize with the remote system.
18305 @item set monitor-prompt @var{prompt}
18306 @kindex set monitor-prompt@r{, MIPS remote}
18307 @cindex remote monitor prompt
18308 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18309 remote monitor. The default depends on the target:
18319 @item show monitor-prompt
18320 @kindex show monitor-prompt@r{, MIPS remote}
18321 Show the current strings @value{GDBN} expects as the prompt from the
18324 @item set monitor-warnings
18325 @kindex set monitor-warnings@r{, MIPS remote}
18326 Enable or disable monitor warnings about hardware breakpoints. This
18327 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18328 display warning messages whose codes are returned by the @code{lsi}
18329 PMON monitor for breakpoint commands.
18331 @item show monitor-warnings
18332 @kindex show monitor-warnings@r{, MIPS remote}
18333 Show the current setting of printing monitor warnings.
18335 @item pmon @var{command}
18336 @kindex pmon@r{, MIPS remote}
18337 @cindex send PMON command
18338 This command allows sending an arbitrary @var{command} string to the
18339 monitor. The monitor must be in debug mode for this to work.
18342 @node OpenRISC 1000
18343 @subsection OpenRISC 1000
18344 @cindex OpenRISC 1000
18346 @cindex or1k boards
18347 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18348 about platform and commands.
18352 @kindex target jtag
18353 @item target jtag jtag://@var{host}:@var{port}
18355 Connects to remote JTAG server.
18356 JTAG remote server can be either an or1ksim or JTAG server,
18357 connected via parallel port to the board.
18359 Example: @code{target jtag jtag://localhost:9999}
18362 @item or1ksim @var{command}
18363 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18364 Simulator, proprietary commands can be executed.
18366 @kindex info or1k spr
18367 @item info or1k spr
18368 Displays spr groups.
18370 @item info or1k spr @var{group}
18371 @itemx info or1k spr @var{groupno}
18372 Displays register names in selected group.
18374 @item info or1k spr @var{group} @var{register}
18375 @itemx info or1k spr @var{register}
18376 @itemx info or1k spr @var{groupno} @var{registerno}
18377 @itemx info or1k spr @var{registerno}
18378 Shows information about specified spr register.
18381 @item spr @var{group} @var{register} @var{value}
18382 @itemx spr @var{register @var{value}}
18383 @itemx spr @var{groupno} @var{registerno @var{value}}
18384 @itemx spr @var{registerno @var{value}}
18385 Writes @var{value} to specified spr register.
18388 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18389 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18390 program execution and is thus much faster. Hardware breakpoints/watchpoint
18391 triggers can be set using:
18394 Load effective address/data
18396 Store effective address/data
18398 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18403 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18404 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18406 @code{htrace} commands:
18407 @cindex OpenRISC 1000 htrace
18410 @item hwatch @var{conditional}
18411 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18412 or Data. For example:
18414 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18416 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18420 Display information about current HW trace configuration.
18422 @item htrace trigger @var{conditional}
18423 Set starting criteria for HW trace.
18425 @item htrace qualifier @var{conditional}
18426 Set acquisition qualifier for HW trace.
18428 @item htrace stop @var{conditional}
18429 Set HW trace stopping criteria.
18431 @item htrace record [@var{data}]*
18432 Selects the data to be recorded, when qualifier is met and HW trace was
18435 @item htrace enable
18436 @itemx htrace disable
18437 Enables/disables the HW trace.
18439 @item htrace rewind [@var{filename}]
18440 Clears currently recorded trace data.
18442 If filename is specified, new trace file is made and any newly collected data
18443 will be written there.
18445 @item htrace print [@var{start} [@var{len}]]
18446 Prints trace buffer, using current record configuration.
18448 @item htrace mode continuous
18449 Set continuous trace mode.
18451 @item htrace mode suspend
18452 Set suspend trace mode.
18456 @node PowerPC Embedded
18457 @subsection PowerPC Embedded
18459 @value{GDBN} provides the following PowerPC-specific commands:
18462 @kindex set powerpc
18463 @item set powerpc soft-float
18464 @itemx show powerpc soft-float
18465 Force @value{GDBN} to use (or not use) a software floating point calling
18466 convention. By default, @value{GDBN} selects the calling convention based
18467 on the selected architecture and the provided executable file.
18469 @item set powerpc vector-abi
18470 @itemx show powerpc vector-abi
18471 Force @value{GDBN} to use the specified calling convention for vector
18472 arguments and return values. The valid options are @samp{auto};
18473 @samp{generic}, to avoid vector registers even if they are present;
18474 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18475 registers. By default, @value{GDBN} selects the calling convention
18476 based on the selected architecture and the provided executable file.
18478 @kindex target dink32
18479 @item target dink32 @var{dev}
18480 DINK32 ROM monitor.
18482 @kindex target ppcbug
18483 @item target ppcbug @var{dev}
18484 @kindex target ppcbug1
18485 @item target ppcbug1 @var{dev}
18486 PPCBUG ROM monitor for PowerPC.
18489 @item target sds @var{dev}
18490 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18493 @cindex SDS protocol
18494 The following commands specific to the SDS protocol are supported
18498 @item set sdstimeout @var{nsec}
18499 @kindex set sdstimeout
18500 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18501 default is 2 seconds.
18503 @item show sdstimeout
18504 @kindex show sdstimeout
18505 Show the current value of the SDS timeout.
18507 @item sds @var{command}
18508 @kindex sds@r{, a command}
18509 Send the specified @var{command} string to the SDS monitor.
18514 @subsection HP PA Embedded
18518 @kindex target op50n
18519 @item target op50n @var{dev}
18520 OP50N monitor, running on an OKI HPPA board.
18522 @kindex target w89k
18523 @item target w89k @var{dev}
18524 W89K monitor, running on a Winbond HPPA board.
18529 @subsection Tsqware Sparclet
18533 @value{GDBN} enables developers to debug tasks running on
18534 Sparclet targets from a Unix host.
18535 @value{GDBN} uses code that runs on
18536 both the Unix host and on the Sparclet target. The program
18537 @code{@value{GDBP}} is installed and executed on the Unix host.
18540 @item remotetimeout @var{args}
18541 @kindex remotetimeout
18542 @value{GDBN} supports the option @code{remotetimeout}.
18543 This option is set by the user, and @var{args} represents the number of
18544 seconds @value{GDBN} waits for responses.
18547 @cindex compiling, on Sparclet
18548 When compiling for debugging, include the options @samp{-g} to get debug
18549 information and @samp{-Ttext} to relocate the program to where you wish to
18550 load it on the target. You may also want to add the options @samp{-n} or
18551 @samp{-N} in order to reduce the size of the sections. Example:
18554 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18557 You can use @code{objdump} to verify that the addresses are what you intended:
18560 sparclet-aout-objdump --headers --syms prog
18563 @cindex running, on Sparclet
18565 your Unix execution search path to find @value{GDBN}, you are ready to
18566 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18567 (or @code{sparclet-aout-gdb}, depending on your installation).
18569 @value{GDBN} comes up showing the prompt:
18576 * Sparclet File:: Setting the file to debug
18577 * Sparclet Connection:: Connecting to Sparclet
18578 * Sparclet Download:: Sparclet download
18579 * Sparclet Execution:: Running and debugging
18582 @node Sparclet File
18583 @subsubsection Setting File to Debug
18585 The @value{GDBN} command @code{file} lets you choose with program to debug.
18588 (gdbslet) file prog
18592 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18593 @value{GDBN} locates
18594 the file by searching the directories listed in the command search
18596 If the file was compiled with debug information (option @samp{-g}), source
18597 files will be searched as well.
18598 @value{GDBN} locates
18599 the source files by searching the directories listed in the directory search
18600 path (@pxref{Environment, ,Your Program's Environment}).
18602 to find a file, it displays a message such as:
18605 prog: No such file or directory.
18608 When this happens, add the appropriate directories to the search paths with
18609 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18610 @code{target} command again.
18612 @node Sparclet Connection
18613 @subsubsection Connecting to Sparclet
18615 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18616 To connect to a target on serial port ``@code{ttya}'', type:
18619 (gdbslet) target sparclet /dev/ttya
18620 Remote target sparclet connected to /dev/ttya
18621 main () at ../prog.c:3
18625 @value{GDBN} displays messages like these:
18631 @node Sparclet Download
18632 @subsubsection Sparclet Download
18634 @cindex download to Sparclet
18635 Once connected to the Sparclet target,
18636 you can use the @value{GDBN}
18637 @code{load} command to download the file from the host to the target.
18638 The file name and load offset should be given as arguments to the @code{load}
18640 Since the file format is aout, the program must be loaded to the starting
18641 address. You can use @code{objdump} to find out what this value is. The load
18642 offset is an offset which is added to the VMA (virtual memory address)
18643 of each of the file's sections.
18644 For instance, if the program
18645 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18646 and bss at 0x12010170, in @value{GDBN}, type:
18649 (gdbslet) load prog 0x12010000
18650 Loading section .text, size 0xdb0 vma 0x12010000
18653 If the code is loaded at a different address then what the program was linked
18654 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18655 to tell @value{GDBN} where to map the symbol table.
18657 @node Sparclet Execution
18658 @subsubsection Running and Debugging
18660 @cindex running and debugging Sparclet programs
18661 You can now begin debugging the task using @value{GDBN}'s execution control
18662 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18663 manual for the list of commands.
18667 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18669 Starting program: prog
18670 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18671 3 char *symarg = 0;
18673 4 char *execarg = "hello!";
18678 @subsection Fujitsu Sparclite
18682 @kindex target sparclite
18683 @item target sparclite @var{dev}
18684 Fujitsu sparclite boards, used only for the purpose of loading.
18685 You must use an additional command to debug the program.
18686 For example: target remote @var{dev} using @value{GDBN} standard
18692 @subsection Zilog Z8000
18695 @cindex simulator, Z8000
18696 @cindex Zilog Z8000 simulator
18698 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
18701 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
18702 unsegmented variant of the Z8000 architecture) or the Z8001 (the
18703 segmented variant). The simulator recognizes which architecture is
18704 appropriate by inspecting the object code.
18707 @item target sim @var{args}
18709 @kindex target sim@r{, with Z8000}
18710 Debug programs on a simulated CPU. If the simulator supports setup
18711 options, specify them via @var{args}.
18715 After specifying this target, you can debug programs for the simulated
18716 CPU in the same style as programs for your host computer; use the
18717 @code{file} command to load a new program image, the @code{run} command
18718 to run your program, and so on.
18720 As well as making available all the usual machine registers
18721 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18722 additional items of information as specially named registers:
18727 Counts clock-ticks in the simulator.
18730 Counts instructions run in the simulator.
18733 Execution time in 60ths of a second.
18737 You can refer to these values in @value{GDBN} expressions with the usual
18738 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18739 conditional breakpoint that suspends only after at least 5000
18740 simulated clock ticks.
18743 @subsection Atmel AVR
18746 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18747 following AVR-specific commands:
18750 @item info io_registers
18751 @kindex info io_registers@r{, AVR}
18752 @cindex I/O registers (Atmel AVR)
18753 This command displays information about the AVR I/O registers. For
18754 each register, @value{GDBN} prints its number and value.
18761 When configured for debugging CRIS, @value{GDBN} provides the
18762 following CRIS-specific commands:
18765 @item set cris-version @var{ver}
18766 @cindex CRIS version
18767 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
18768 The CRIS version affects register names and sizes. This command is useful in
18769 case autodetection of the CRIS version fails.
18771 @item show cris-version
18772 Show the current CRIS version.
18774 @item set cris-dwarf2-cfi
18775 @cindex DWARF-2 CFI and CRIS
18776 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
18777 Change to @samp{off} when using @code{gcc-cris} whose version is below
18780 @item show cris-dwarf2-cfi
18781 Show the current state of using DWARF-2 CFI.
18783 @item set cris-mode @var{mode}
18785 Set the current CRIS mode to @var{mode}. It should only be changed when
18786 debugging in guru mode, in which case it should be set to
18787 @samp{guru} (the default is @samp{normal}).
18789 @item show cris-mode
18790 Show the current CRIS mode.
18794 @subsection Renesas Super-H
18797 For the Renesas Super-H processor, @value{GDBN} provides these
18802 @kindex regs@r{, Super-H}
18803 Show the values of all Super-H registers.
18805 @item set sh calling-convention @var{convention}
18806 @kindex set sh calling-convention
18807 Set the calling-convention used when calling functions from @value{GDBN}.
18808 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
18809 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
18810 convention. If the DWARF-2 information of the called function specifies
18811 that the function follows the Renesas calling convention, the function
18812 is called using the Renesas calling convention. If the calling convention
18813 is set to @samp{renesas}, the Renesas calling convention is always used,
18814 regardless of the DWARF-2 information. This can be used to override the
18815 default of @samp{gcc} if debug information is missing, or the compiler
18816 does not emit the DWARF-2 calling convention entry for a function.
18818 @item show sh calling-convention
18819 @kindex show sh calling-convention
18820 Show the current calling convention setting.
18825 @node Architectures
18826 @section Architectures
18828 This section describes characteristics of architectures that affect
18829 all uses of @value{GDBN} with the architecture, both native and cross.
18836 * HPPA:: HP PA architecture
18837 * SPU:: Cell Broadband Engine SPU architecture
18842 @subsection x86 Architecture-specific Issues
18845 @item set struct-convention @var{mode}
18846 @kindex set struct-convention
18847 @cindex struct return convention
18848 @cindex struct/union returned in registers
18849 Set the convention used by the inferior to return @code{struct}s and
18850 @code{union}s from functions to @var{mode}. Possible values of
18851 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
18852 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
18853 are returned on the stack, while @code{"reg"} means that a
18854 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
18855 be returned in a register.
18857 @item show struct-convention
18858 @kindex show struct-convention
18859 Show the current setting of the convention to return @code{struct}s
18868 @kindex set rstack_high_address
18869 @cindex AMD 29K register stack
18870 @cindex register stack, AMD29K
18871 @item set rstack_high_address @var{address}
18872 On AMD 29000 family processors, registers are saved in a separate
18873 @dfn{register stack}. There is no way for @value{GDBN} to determine the
18874 extent of this stack. Normally, @value{GDBN} just assumes that the
18875 stack is ``large enough''. This may result in @value{GDBN} referencing
18876 memory locations that do not exist. If necessary, you can get around
18877 this problem by specifying the ending address of the register stack with
18878 the @code{set rstack_high_address} command. The argument should be an
18879 address, which you probably want to precede with @samp{0x} to specify in
18882 @kindex show rstack_high_address
18883 @item show rstack_high_address
18884 Display the current limit of the register stack, on AMD 29000 family
18892 See the following section.
18897 @cindex stack on Alpha
18898 @cindex stack on MIPS
18899 @cindex Alpha stack
18901 Alpha- and MIPS-based computers use an unusual stack frame, which
18902 sometimes requires @value{GDBN} to search backward in the object code to
18903 find the beginning of a function.
18905 @cindex response time, MIPS debugging
18906 To improve response time (especially for embedded applications, where
18907 @value{GDBN} may be restricted to a slow serial line for this search)
18908 you may want to limit the size of this search, using one of these
18912 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
18913 @item set heuristic-fence-post @var{limit}
18914 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
18915 search for the beginning of a function. A value of @var{0} (the
18916 default) means there is no limit. However, except for @var{0}, the
18917 larger the limit the more bytes @code{heuristic-fence-post} must search
18918 and therefore the longer it takes to run. You should only need to use
18919 this command when debugging a stripped executable.
18921 @item show heuristic-fence-post
18922 Display the current limit.
18926 These commands are available @emph{only} when @value{GDBN} is configured
18927 for debugging programs on Alpha or MIPS processors.
18929 Several MIPS-specific commands are available when debugging MIPS
18933 @item set mips abi @var{arg}
18934 @kindex set mips abi
18935 @cindex set ABI for MIPS
18936 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
18937 values of @var{arg} are:
18941 The default ABI associated with the current binary (this is the
18952 @item show mips abi
18953 @kindex show mips abi
18954 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
18957 @itemx show mipsfpu
18958 @xref{MIPS Embedded, set mipsfpu}.
18960 @item set mips mask-address @var{arg}
18961 @kindex set mips mask-address
18962 @cindex MIPS addresses, masking
18963 This command determines whether the most-significant 32 bits of 64-bit
18964 MIPS addresses are masked off. The argument @var{arg} can be
18965 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
18966 setting, which lets @value{GDBN} determine the correct value.
18968 @item show mips mask-address
18969 @kindex show mips mask-address
18970 Show whether the upper 32 bits of MIPS addresses are masked off or
18973 @item set remote-mips64-transfers-32bit-regs
18974 @kindex set remote-mips64-transfers-32bit-regs
18975 This command controls compatibility with 64-bit MIPS targets that
18976 transfer data in 32-bit quantities. If you have an old MIPS 64 target
18977 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
18978 and 64 bits for other registers, set this option to @samp{on}.
18980 @item show remote-mips64-transfers-32bit-regs
18981 @kindex show remote-mips64-transfers-32bit-regs
18982 Show the current setting of compatibility with older MIPS 64 targets.
18984 @item set debug mips
18985 @kindex set debug mips
18986 This command turns on and off debugging messages for the MIPS-specific
18987 target code in @value{GDBN}.
18989 @item show debug mips
18990 @kindex show debug mips
18991 Show the current setting of MIPS debugging messages.
18997 @cindex HPPA support
18999 When @value{GDBN} is debugging the HP PA architecture, it provides the
19000 following special commands:
19003 @item set debug hppa
19004 @kindex set debug hppa
19005 This command determines whether HPPA architecture-specific debugging
19006 messages are to be displayed.
19008 @item show debug hppa
19009 Show whether HPPA debugging messages are displayed.
19011 @item maint print unwind @var{address}
19012 @kindex maint print unwind@r{, HPPA}
19013 This command displays the contents of the unwind table entry at the
19014 given @var{address}.
19020 @subsection Cell Broadband Engine SPU architecture
19021 @cindex Cell Broadband Engine
19024 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19025 it provides the following special commands:
19028 @item info spu event
19030 Display SPU event facility status. Shows current event mask
19031 and pending event status.
19033 @item info spu signal
19034 Display SPU signal notification facility status. Shows pending
19035 signal-control word and signal notification mode of both signal
19036 notification channels.
19038 @item info spu mailbox
19039 Display SPU mailbox facility status. Shows all pending entries,
19040 in order of processing, in each of the SPU Write Outbound,
19041 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19044 Display MFC DMA status. Shows all pending commands in the MFC
19045 DMA queue. For each entry, opcode, tag, class IDs, effective
19046 and local store addresses and transfer size are shown.
19048 @item info spu proxydma
19049 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19050 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19051 and local store addresses and transfer size are shown.
19055 When @value{GDBN} is debugging a combined PowerPC/SPU application
19056 on the Cell Broadband Engine, it provides in addition the following
19060 @item set spu stop-on-load @var{arg}
19062 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19063 will give control to the user when a new SPE thread enters its @code{main}
19064 function. The default is @code{off}.
19066 @item show spu stop-on-load
19068 Show whether to stop for new SPE threads.
19070 @item set spu auto-flush-cache @var{arg}
19071 Set whether to automatically flush the software-managed cache. When set to
19072 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19073 cache to be flushed whenever SPE execution stops. This provides a consistent
19074 view of PowerPC memory that is accessed via the cache. If an application
19075 does not use the software-managed cache, this option has no effect.
19077 @item show spu auto-flush-cache
19078 Show whether to automatically flush the software-managed cache.
19083 @subsection PowerPC
19084 @cindex PowerPC architecture
19086 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19087 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19088 numbers stored in the floating point registers. These values must be stored
19089 in two consecutive registers, always starting at an even register like
19090 @code{f0} or @code{f2}.
19092 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19093 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19094 @code{f2} and @code{f3} for @code{$dl1} and so on.
19096 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19097 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19100 @node Controlling GDB
19101 @chapter Controlling @value{GDBN}
19103 You can alter the way @value{GDBN} interacts with you by using the
19104 @code{set} command. For commands controlling how @value{GDBN} displays
19105 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19110 * Editing:: Command editing
19111 * Command History:: Command history
19112 * Screen Size:: Screen size
19113 * Numbers:: Numbers
19114 * ABI:: Configuring the current ABI
19115 * Messages/Warnings:: Optional warnings and messages
19116 * Debugging Output:: Optional messages about internal happenings
19117 * Other Misc Settings:: Other Miscellaneous Settings
19125 @value{GDBN} indicates its readiness to read a command by printing a string
19126 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19127 can change the prompt string with the @code{set prompt} command. For
19128 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19129 the prompt in one of the @value{GDBN} sessions so that you can always tell
19130 which one you are talking to.
19132 @emph{Note:} @code{set prompt} does not add a space for you after the
19133 prompt you set. This allows you to set a prompt which ends in a space
19134 or a prompt that does not.
19138 @item set prompt @var{newprompt}
19139 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19141 @kindex show prompt
19143 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19147 @section Command Editing
19149 @cindex command line editing
19151 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19152 @sc{gnu} library provides consistent behavior for programs which provide a
19153 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19154 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19155 substitution, and a storage and recall of command history across
19156 debugging sessions.
19158 You may control the behavior of command line editing in @value{GDBN} with the
19159 command @code{set}.
19162 @kindex set editing
19165 @itemx set editing on
19166 Enable command line editing (enabled by default).
19168 @item set editing off
19169 Disable command line editing.
19171 @kindex show editing
19173 Show whether command line editing is enabled.
19176 @xref{Command Line Editing}, for more details about the Readline
19177 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19178 encouraged to read that chapter.
19180 @node Command History
19181 @section Command History
19182 @cindex command history
19184 @value{GDBN} can keep track of the commands you type during your
19185 debugging sessions, so that you can be certain of precisely what
19186 happened. Use these commands to manage the @value{GDBN} command
19189 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19190 package, to provide the history facility. @xref{Using History
19191 Interactively}, for the detailed description of the History library.
19193 To issue a command to @value{GDBN} without affecting certain aspects of
19194 the state which is seen by users, prefix it with @samp{server }
19195 (@pxref{Server Prefix}). This
19196 means that this command will not affect the command history, nor will it
19197 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19198 pressed on a line by itself.
19200 @cindex @code{server}, command prefix
19201 The server prefix does not affect the recording of values into the value
19202 history; to print a value without recording it into the value history,
19203 use the @code{output} command instead of the @code{print} command.
19205 Here is the description of @value{GDBN} commands related to command
19209 @cindex history substitution
19210 @cindex history file
19211 @kindex set history filename
19212 @cindex @env{GDBHISTFILE}, environment variable
19213 @item set history filename @var{fname}
19214 Set the name of the @value{GDBN} command history file to @var{fname}.
19215 This is the file where @value{GDBN} reads an initial command history
19216 list, and where it writes the command history from this session when it
19217 exits. You can access this list through history expansion or through
19218 the history command editing characters listed below. This file defaults
19219 to the value of the environment variable @code{GDBHISTFILE}, or to
19220 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
19223 @cindex save command history
19224 @kindex set history save
19225 @item set history save
19226 @itemx set history save on
19227 Record command history in a file, whose name may be specified with the
19228 @code{set history filename} command. By default, this option is disabled.
19230 @item set history save off
19231 Stop recording command history in a file.
19233 @cindex history size
19234 @kindex set history size
19235 @cindex @env{HISTSIZE}, environment variable
19236 @item set history size @var{size}
19237 Set the number of commands which @value{GDBN} keeps in its history list.
19238 This defaults to the value of the environment variable
19239 @code{HISTSIZE}, or to 256 if this variable is not set.
19242 History expansion assigns special meaning to the character @kbd{!}.
19243 @xref{Event Designators}, for more details.
19245 @cindex history expansion, turn on/off
19246 Since @kbd{!} is also the logical not operator in C, history expansion
19247 is off by default. If you decide to enable history expansion with the
19248 @code{set history expansion on} command, you may sometimes need to
19249 follow @kbd{!} (when it is used as logical not, in an expression) with
19250 a space or a tab to prevent it from being expanded. The readline
19251 history facilities do not attempt substitution on the strings
19252 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19254 The commands to control history expansion are:
19257 @item set history expansion on
19258 @itemx set history expansion
19259 @kindex set history expansion
19260 Enable history expansion. History expansion is off by default.
19262 @item set history expansion off
19263 Disable history expansion.
19266 @kindex show history
19268 @itemx show history filename
19269 @itemx show history save
19270 @itemx show history size
19271 @itemx show history expansion
19272 These commands display the state of the @value{GDBN} history parameters.
19273 @code{show history} by itself displays all four states.
19278 @kindex show commands
19279 @cindex show last commands
19280 @cindex display command history
19281 @item show commands
19282 Display the last ten commands in the command history.
19284 @item show commands @var{n}
19285 Print ten commands centered on command number @var{n}.
19287 @item show commands +
19288 Print ten commands just after the commands last printed.
19292 @section Screen Size
19293 @cindex size of screen
19294 @cindex pauses in output
19296 Certain commands to @value{GDBN} may produce large amounts of
19297 information output to the screen. To help you read all of it,
19298 @value{GDBN} pauses and asks you for input at the end of each page of
19299 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19300 to discard the remaining output. Also, the screen width setting
19301 determines when to wrap lines of output. Depending on what is being
19302 printed, @value{GDBN} tries to break the line at a readable place,
19303 rather than simply letting it overflow onto the following line.
19305 Normally @value{GDBN} knows the size of the screen from the terminal
19306 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19307 together with the value of the @code{TERM} environment variable and the
19308 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19309 you can override it with the @code{set height} and @code{set
19316 @kindex show height
19317 @item set height @var{lpp}
19319 @itemx set width @var{cpl}
19321 These @code{set} commands specify a screen height of @var{lpp} lines and
19322 a screen width of @var{cpl} characters. The associated @code{show}
19323 commands display the current settings.
19325 If you specify a height of zero lines, @value{GDBN} does not pause during
19326 output no matter how long the output is. This is useful if output is to a
19327 file or to an editor buffer.
19329 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19330 from wrapping its output.
19332 @item set pagination on
19333 @itemx set pagination off
19334 @kindex set pagination
19335 Turn the output pagination on or off; the default is on. Turning
19336 pagination off is the alternative to @code{set height 0}. Note that
19337 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19338 Options, -batch}) also automatically disables pagination.
19340 @item show pagination
19341 @kindex show pagination
19342 Show the current pagination mode.
19347 @cindex number representation
19348 @cindex entering numbers
19350 You can always enter numbers in octal, decimal, or hexadecimal in
19351 @value{GDBN} by the usual conventions: octal numbers begin with
19352 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19353 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19354 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19355 10; likewise, the default display for numbers---when no particular
19356 format is specified---is base 10. You can change the default base for
19357 both input and output with the commands described below.
19360 @kindex set input-radix
19361 @item set input-radix @var{base}
19362 Set the default base for numeric input. Supported choices
19363 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19364 specified either unambiguously or using the current input radix; for
19368 set input-radix 012
19369 set input-radix 10.
19370 set input-radix 0xa
19374 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19375 leaves the input radix unchanged, no matter what it was, since
19376 @samp{10}, being without any leading or trailing signs of its base, is
19377 interpreted in the current radix. Thus, if the current radix is 16,
19378 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19381 @kindex set output-radix
19382 @item set output-radix @var{base}
19383 Set the default base for numeric display. Supported choices
19384 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19385 specified either unambiguously or using the current input radix.
19387 @kindex show input-radix
19388 @item show input-radix
19389 Display the current default base for numeric input.
19391 @kindex show output-radix
19392 @item show output-radix
19393 Display the current default base for numeric display.
19395 @item set radix @r{[}@var{base}@r{]}
19399 These commands set and show the default base for both input and output
19400 of numbers. @code{set radix} sets the radix of input and output to
19401 the same base; without an argument, it resets the radix back to its
19402 default value of 10.
19407 @section Configuring the Current ABI
19409 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19410 application automatically. However, sometimes you need to override its
19411 conclusions. Use these commands to manage @value{GDBN}'s view of the
19418 One @value{GDBN} configuration can debug binaries for multiple operating
19419 system targets, either via remote debugging or native emulation.
19420 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19421 but you can override its conclusion using the @code{set osabi} command.
19422 One example where this is useful is in debugging of binaries which use
19423 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19424 not have the same identifying marks that the standard C library for your
19429 Show the OS ABI currently in use.
19432 With no argument, show the list of registered available OS ABI's.
19434 @item set osabi @var{abi}
19435 Set the current OS ABI to @var{abi}.
19438 @cindex float promotion
19440 Generally, the way that an argument of type @code{float} is passed to a
19441 function depends on whether the function is prototyped. For a prototyped
19442 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19443 according to the architecture's convention for @code{float}. For unprototyped
19444 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19445 @code{double} and then passed.
19447 Unfortunately, some forms of debug information do not reliably indicate whether
19448 a function is prototyped. If @value{GDBN} calls a function that is not marked
19449 as prototyped, it consults @kbd{set coerce-float-to-double}.
19452 @kindex set coerce-float-to-double
19453 @item set coerce-float-to-double
19454 @itemx set coerce-float-to-double on
19455 Arguments of type @code{float} will be promoted to @code{double} when passed
19456 to an unprototyped function. This is the default setting.
19458 @item set coerce-float-to-double off
19459 Arguments of type @code{float} will be passed directly to unprototyped
19462 @kindex show coerce-float-to-double
19463 @item show coerce-float-to-double
19464 Show the current setting of promoting @code{float} to @code{double}.
19468 @kindex show cp-abi
19469 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19470 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19471 used to build your application. @value{GDBN} only fully supports
19472 programs with a single C@t{++} ABI; if your program contains code using
19473 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19474 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19475 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19476 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19477 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19478 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19483 Show the C@t{++} ABI currently in use.
19486 With no argument, show the list of supported C@t{++} ABI's.
19488 @item set cp-abi @var{abi}
19489 @itemx set cp-abi auto
19490 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19493 @node Messages/Warnings
19494 @section Optional Warnings and Messages
19496 @cindex verbose operation
19497 @cindex optional warnings
19498 By default, @value{GDBN} is silent about its inner workings. If you are
19499 running on a slow machine, you may want to use the @code{set verbose}
19500 command. This makes @value{GDBN} tell you when it does a lengthy
19501 internal operation, so you will not think it has crashed.
19503 Currently, the messages controlled by @code{set verbose} are those
19504 which announce that the symbol table for a source file is being read;
19505 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19508 @kindex set verbose
19509 @item set verbose on
19510 Enables @value{GDBN} output of certain informational messages.
19512 @item set verbose off
19513 Disables @value{GDBN} output of certain informational messages.
19515 @kindex show verbose
19517 Displays whether @code{set verbose} is on or off.
19520 By default, if @value{GDBN} encounters bugs in the symbol table of an
19521 object file, it is silent; but if you are debugging a compiler, you may
19522 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19527 @kindex set complaints
19528 @item set complaints @var{limit}
19529 Permits @value{GDBN} to output @var{limit} complaints about each type of
19530 unusual symbols before becoming silent about the problem. Set
19531 @var{limit} to zero to suppress all complaints; set it to a large number
19532 to prevent complaints from being suppressed.
19534 @kindex show complaints
19535 @item show complaints
19536 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19540 @anchor{confirmation requests}
19541 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19542 lot of stupid questions to confirm certain commands. For example, if
19543 you try to run a program which is already running:
19547 The program being debugged has been started already.
19548 Start it from the beginning? (y or n)
19551 If you are willing to unflinchingly face the consequences of your own
19552 commands, you can disable this ``feature'':
19556 @kindex set confirm
19558 @cindex confirmation
19559 @cindex stupid questions
19560 @item set confirm off
19561 Disables confirmation requests. Note that running @value{GDBN} with
19562 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19563 automatically disables confirmation requests.
19565 @item set confirm on
19566 Enables confirmation requests (the default).
19568 @kindex show confirm
19570 Displays state of confirmation requests.
19574 @cindex command tracing
19575 If you need to debug user-defined commands or sourced files you may find it
19576 useful to enable @dfn{command tracing}. In this mode each command will be
19577 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19578 quantity denoting the call depth of each command.
19581 @kindex set trace-commands
19582 @cindex command scripts, debugging
19583 @item set trace-commands on
19584 Enable command tracing.
19585 @item set trace-commands off
19586 Disable command tracing.
19587 @item show trace-commands
19588 Display the current state of command tracing.
19591 @node Debugging Output
19592 @section Optional Messages about Internal Happenings
19593 @cindex optional debugging messages
19595 @value{GDBN} has commands that enable optional debugging messages from
19596 various @value{GDBN} subsystems; normally these commands are of
19597 interest to @value{GDBN} maintainers, or when reporting a bug. This
19598 section documents those commands.
19601 @kindex set exec-done-display
19602 @item set exec-done-display
19603 Turns on or off the notification of asynchronous commands'
19604 completion. When on, @value{GDBN} will print a message when an
19605 asynchronous command finishes its execution. The default is off.
19606 @kindex show exec-done-display
19607 @item show exec-done-display
19608 Displays the current setting of asynchronous command completion
19611 @cindex gdbarch debugging info
19612 @cindex architecture debugging info
19613 @item set debug arch
19614 Turns on or off display of gdbarch debugging info. The default is off
19616 @item show debug arch
19617 Displays the current state of displaying gdbarch debugging info.
19618 @item set debug aix-thread
19619 @cindex AIX threads
19620 Display debugging messages about inner workings of the AIX thread
19622 @item show debug aix-thread
19623 Show the current state of AIX thread debugging info display.
19624 @item set debug dwarf2-die
19625 @cindex DWARF2 DIEs
19626 Dump DWARF2 DIEs after they are read in.
19627 The value is the number of nesting levels to print.
19628 A value of zero turns off the display.
19629 @item show debug dwarf2-die
19630 Show the current state of DWARF2 DIE debugging.
19631 @item set debug displaced
19632 @cindex displaced stepping debugging info
19633 Turns on or off display of @value{GDBN} debugging info for the
19634 displaced stepping support. The default is off.
19635 @item show debug displaced
19636 Displays the current state of displaying @value{GDBN} debugging info
19637 related to displaced stepping.
19638 @item set debug event
19639 @cindex event debugging info
19640 Turns on or off display of @value{GDBN} event debugging info. The
19642 @item show debug event
19643 Displays the current state of displaying @value{GDBN} event debugging
19645 @item set debug expression
19646 @cindex expression debugging info
19647 Turns on or off display of debugging info about @value{GDBN}
19648 expression parsing. The default is off.
19649 @item show debug expression
19650 Displays the current state of displaying debugging info about
19651 @value{GDBN} expression parsing.
19652 @item set debug frame
19653 @cindex frame debugging info
19654 Turns on or off display of @value{GDBN} frame debugging info. The
19656 @item show debug frame
19657 Displays the current state of displaying @value{GDBN} frame debugging
19659 @item set debug gnu-nat
19660 @cindex @sc{gnu}/Hurd debug messages
19661 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19662 @item show debug gnu-nat
19663 Show the current state of @sc{gnu}/Hurd debugging messages.
19664 @item set debug infrun
19665 @cindex inferior debugging info
19666 Turns on or off display of @value{GDBN} debugging info for running the inferior.
19667 The default is off. @file{infrun.c} contains GDB's runtime state machine used
19668 for implementing operations such as single-stepping the inferior.
19669 @item show debug infrun
19670 Displays the current state of @value{GDBN} inferior debugging.
19671 @item set debug lin-lwp
19672 @cindex @sc{gnu}/Linux LWP debug messages
19673 @cindex Linux lightweight processes
19674 Turns on or off debugging messages from the Linux LWP debug support.
19675 @item show debug lin-lwp
19676 Show the current state of Linux LWP debugging messages.
19677 @item set debug lin-lwp-async
19678 @cindex @sc{gnu}/Linux LWP async debug messages
19679 @cindex Linux lightweight processes
19680 Turns on or off debugging messages from the Linux LWP async debug support.
19681 @item show debug lin-lwp-async
19682 Show the current state of Linux LWP async debugging messages.
19683 @item set debug observer
19684 @cindex observer debugging info
19685 Turns on or off display of @value{GDBN} observer debugging. This
19686 includes info such as the notification of observable events.
19687 @item show debug observer
19688 Displays the current state of observer debugging.
19689 @item set debug overload
19690 @cindex C@t{++} overload debugging info
19691 Turns on or off display of @value{GDBN} C@t{++} overload debugging
19692 info. This includes info such as ranking of functions, etc. The default
19694 @item show debug overload
19695 Displays the current state of displaying @value{GDBN} C@t{++} overload
19697 @cindex expression parser, debugging info
19698 @cindex debug expression parser
19699 @item set debug parser
19700 Turns on or off the display of expression parser debugging output.
19701 Internally, this sets the @code{yydebug} variable in the expression
19702 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
19703 details. The default is off.
19704 @item show debug parser
19705 Show the current state of expression parser debugging.
19706 @cindex packets, reporting on stdout
19707 @cindex serial connections, debugging
19708 @cindex debug remote protocol
19709 @cindex remote protocol debugging
19710 @cindex display remote packets
19711 @item set debug remote
19712 Turns on or off display of reports on all packets sent back and forth across
19713 the serial line to the remote machine. The info is printed on the
19714 @value{GDBN} standard output stream. The default is off.
19715 @item show debug remote
19716 Displays the state of display of remote packets.
19717 @item set debug serial
19718 Turns on or off display of @value{GDBN} serial debugging info. The
19720 @item show debug serial
19721 Displays the current state of displaying @value{GDBN} serial debugging
19723 @item set debug solib-frv
19724 @cindex FR-V shared-library debugging
19725 Turns on or off debugging messages for FR-V shared-library code.
19726 @item show debug solib-frv
19727 Display the current state of FR-V shared-library code debugging
19729 @item set debug target
19730 @cindex target debugging info
19731 Turns on or off display of @value{GDBN} target debugging info. This info
19732 includes what is going on at the target level of GDB, as it happens. The
19733 default is 0. Set it to 1 to track events, and to 2 to also track the
19734 value of large memory transfers. Changes to this flag do not take effect
19735 until the next time you connect to a target or use the @code{run} command.
19736 @item show debug target
19737 Displays the current state of displaying @value{GDBN} target debugging
19739 @item set debug timestamp
19740 @cindex timestampping debugging info
19741 Turns on or off display of timestamps with @value{GDBN} debugging info.
19742 When enabled, seconds and microseconds are displayed before each debugging
19744 @item show debug timestamp
19745 Displays the current state of displaying timestamps with @value{GDBN}
19747 @item set debugvarobj
19748 @cindex variable object debugging info
19749 Turns on or off display of @value{GDBN} variable object debugging
19750 info. The default is off.
19751 @item show debugvarobj
19752 Displays the current state of displaying @value{GDBN} variable object
19754 @item set debug xml
19755 @cindex XML parser debugging
19756 Turns on or off debugging messages for built-in XML parsers.
19757 @item show debug xml
19758 Displays the current state of XML debugging messages.
19761 @node Other Misc Settings
19762 @section Other Miscellaneous Settings
19763 @cindex miscellaneous settings
19766 @kindex set interactive-mode
19767 @item set interactive-mode
19768 If @code{on}, forces @value{GDBN} to operate interactively.
19769 If @code{off}, forces @value{GDBN} to operate non-interactively,
19770 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
19771 based on whether the debugger was started in a terminal or not.
19773 In the vast majority of cases, the debugger should be able to guess
19774 correctly which mode should be used. But this setting can be useful
19775 in certain specific cases, such as running a MinGW @value{GDBN}
19776 inside a cygwin window.
19778 @kindex show interactive-mode
19779 @item show interactive-mode
19780 Displays whether the debugger is operating in interactive mode or not.
19783 @node Extending GDB
19784 @chapter Extending @value{GDBN}
19785 @cindex extending GDB
19787 @value{GDBN} provides two mechanisms for extension. The first is based
19788 on composition of @value{GDBN} commands, and the second is based on the
19789 Python scripting language.
19791 To facilitate the use of these extensions, @value{GDBN} is capable
19792 of evaluating the contents of a file. When doing so, @value{GDBN}
19793 can recognize which scripting language is being used by looking at
19794 the filename extension. Files with an unrecognized filename extension
19795 are always treated as a @value{GDBN} Command Files.
19796 @xref{Command Files,, Command files}.
19798 You can control how @value{GDBN} evaluates these files with the following
19802 @kindex set script-extension
19803 @kindex show script-extension
19804 @item set script-extension off
19805 All scripts are always evaluated as @value{GDBN} Command Files.
19807 @item set script-extension soft
19808 The debugger determines the scripting language based on filename
19809 extension. If this scripting language is supported, @value{GDBN}
19810 evaluates the script using that language. Otherwise, it evaluates
19811 the file as a @value{GDBN} Command File.
19813 @item set script-extension strict
19814 The debugger determines the scripting language based on filename
19815 extension, and evaluates the script using that language. If the
19816 language is not supported, then the evaluation fails.
19818 @item show script-extension
19819 Display the current value of the @code{script-extension} option.
19824 * Sequences:: Canned Sequences of Commands
19825 * Python:: Scripting @value{GDBN} using Python
19829 @section Canned Sequences of Commands
19831 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
19832 Command Lists}), @value{GDBN} provides two ways to store sequences of
19833 commands for execution as a unit: user-defined commands and command
19837 * Define:: How to define your own commands
19838 * Hooks:: Hooks for user-defined commands
19839 * Command Files:: How to write scripts of commands to be stored in a file
19840 * Output:: Commands for controlled output
19844 @subsection User-defined Commands
19846 @cindex user-defined command
19847 @cindex arguments, to user-defined commands
19848 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
19849 which you assign a new name as a command. This is done with the
19850 @code{define} command. User commands may accept up to 10 arguments
19851 separated by whitespace. Arguments are accessed within the user command
19852 via @code{$arg0@dots{}$arg9}. A trivial example:
19856 print $arg0 + $arg1 + $arg2
19861 To execute the command use:
19868 This defines the command @code{adder}, which prints the sum of
19869 its three arguments. Note the arguments are text substitutions, so they may
19870 reference variables, use complex expressions, or even perform inferior
19873 @cindex argument count in user-defined commands
19874 @cindex how many arguments (user-defined commands)
19875 In addition, @code{$argc} may be used to find out how many arguments have
19876 been passed. This expands to a number in the range 0@dots{}10.
19881 print $arg0 + $arg1
19884 print $arg0 + $arg1 + $arg2
19892 @item define @var{commandname}
19893 Define a command named @var{commandname}. If there is already a command
19894 by that name, you are asked to confirm that you want to redefine it.
19895 @var{commandname} may be a bare command name consisting of letters,
19896 numbers, dashes, and underscores. It may also start with any predefined
19897 prefix command. For example, @samp{define target my-target} creates
19898 a user-defined @samp{target my-target} command.
19900 The definition of the command is made up of other @value{GDBN} command lines,
19901 which are given following the @code{define} command. The end of these
19902 commands is marked by a line containing @code{end}.
19905 @kindex end@r{ (user-defined commands)}
19906 @item document @var{commandname}
19907 Document the user-defined command @var{commandname}, so that it can be
19908 accessed by @code{help}. The command @var{commandname} must already be
19909 defined. This command reads lines of documentation just as @code{define}
19910 reads the lines of the command definition, ending with @code{end}.
19911 After the @code{document} command is finished, @code{help} on command
19912 @var{commandname} displays the documentation you have written.
19914 You may use the @code{document} command again to change the
19915 documentation of a command. Redefining the command with @code{define}
19916 does not change the documentation.
19918 @kindex dont-repeat
19919 @cindex don't repeat command
19921 Used inside a user-defined command, this tells @value{GDBN} that this
19922 command should not be repeated when the user hits @key{RET}
19923 (@pxref{Command Syntax, repeat last command}).
19925 @kindex help user-defined
19926 @item help user-defined
19927 List all user-defined commands, with the first line of the documentation
19932 @itemx show user @var{commandname}
19933 Display the @value{GDBN} commands used to define @var{commandname} (but
19934 not its documentation). If no @var{commandname} is given, display the
19935 definitions for all user-defined commands.
19937 @cindex infinite recursion in user-defined commands
19938 @kindex show max-user-call-depth
19939 @kindex set max-user-call-depth
19940 @item show max-user-call-depth
19941 @itemx set max-user-call-depth
19942 The value of @code{max-user-call-depth} controls how many recursion
19943 levels are allowed in user-defined commands before @value{GDBN} suspects an
19944 infinite recursion and aborts the command.
19947 In addition to the above commands, user-defined commands frequently
19948 use control flow commands, described in @ref{Command Files}.
19950 When user-defined commands are executed, the
19951 commands of the definition are not printed. An error in any command
19952 stops execution of the user-defined command.
19954 If used interactively, commands that would ask for confirmation proceed
19955 without asking when used inside a user-defined command. Many @value{GDBN}
19956 commands that normally print messages to say what they are doing omit the
19957 messages when used in a user-defined command.
19960 @subsection User-defined Command Hooks
19961 @cindex command hooks
19962 @cindex hooks, for commands
19963 @cindex hooks, pre-command
19966 You may define @dfn{hooks}, which are a special kind of user-defined
19967 command. Whenever you run the command @samp{foo}, if the user-defined
19968 command @samp{hook-foo} exists, it is executed (with no arguments)
19969 before that command.
19971 @cindex hooks, post-command
19973 A hook may also be defined which is run after the command you executed.
19974 Whenever you run the command @samp{foo}, if the user-defined command
19975 @samp{hookpost-foo} exists, it is executed (with no arguments) after
19976 that command. Post-execution hooks may exist simultaneously with
19977 pre-execution hooks, for the same command.
19979 It is valid for a hook to call the command which it hooks. If this
19980 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
19982 @c It would be nice if hookpost could be passed a parameter indicating
19983 @c if the command it hooks executed properly or not. FIXME!
19985 @kindex stop@r{, a pseudo-command}
19986 In addition, a pseudo-command, @samp{stop} exists. Defining
19987 (@samp{hook-stop}) makes the associated commands execute every time
19988 execution stops in your program: before breakpoint commands are run,
19989 displays are printed, or the stack frame is printed.
19991 For example, to ignore @code{SIGALRM} signals while
19992 single-stepping, but treat them normally during normal execution,
19997 handle SIGALRM nopass
20001 handle SIGALRM pass
20004 define hook-continue
20005 handle SIGALRM pass
20009 As a further example, to hook at the beginning and end of the @code{echo}
20010 command, and to add extra text to the beginning and end of the message,
20018 define hookpost-echo
20022 (@value{GDBP}) echo Hello World
20023 <<<---Hello World--->>>
20028 You can define a hook for any single-word command in @value{GDBN}, but
20029 not for command aliases; you should define a hook for the basic command
20030 name, e.g.@: @code{backtrace} rather than @code{bt}.
20031 @c FIXME! So how does Joe User discover whether a command is an alias
20033 You can hook a multi-word command by adding @code{hook-} or
20034 @code{hookpost-} to the last word of the command, e.g.@:
20035 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20037 If an error occurs during the execution of your hook, execution of
20038 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20039 (before the command that you actually typed had a chance to run).
20041 If you try to define a hook which does not match any known command, you
20042 get a warning from the @code{define} command.
20044 @node Command Files
20045 @subsection Command Files
20047 @cindex command files
20048 @cindex scripting commands
20049 A command file for @value{GDBN} is a text file made of lines that are
20050 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20051 also be included. An empty line in a command file does nothing; it
20052 does not mean to repeat the last command, as it would from the
20055 You can request the execution of a command file with the @code{source}
20056 command. Note that the @code{source} command is also used to evaluate
20057 scripts that are not Command Files. The exact behavior can be configured
20058 using the @code{script-extension} setting.
20059 @xref{Extending GDB,, Extending GDB}.
20063 @cindex execute commands from a file
20064 @item source [-s] [-v] @var{filename}
20065 Execute the command file @var{filename}.
20068 The lines in a command file are generally executed sequentially,
20069 unless the order of execution is changed by one of the
20070 @emph{flow-control commands} described below. The commands are not
20071 printed as they are executed. An error in any command terminates
20072 execution of the command file and control is returned to the console.
20074 @value{GDBN} first searches for @var{filename} in the current directory.
20075 If the file is not found there, and @var{filename} does not specify a
20076 directory, then @value{GDBN} also looks for the file on the source search path
20077 (specified with the @samp{directory} command);
20078 except that @file{$cdir} is not searched because the compilation directory
20079 is not relevant to scripts.
20081 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20082 on the search path even if @var{filename} specifies a directory.
20083 The search is done by appending @var{filename} to each element of the
20084 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20085 and the search path contains @file{/home/user} then @value{GDBN} will
20086 look for the script @file{/home/user/mylib/myscript}.
20087 The search is also done if @var{filename} is an absolute path.
20088 For example, if @var{filename} is @file{/tmp/myscript} and
20089 the search path contains @file{/home/user} then @value{GDBN} will
20090 look for the script @file{/home/user/tmp/myscript}.
20091 For DOS-like systems, if @var{filename} contains a drive specification,
20092 it is stripped before concatenation. For example, if @var{filename} is
20093 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20094 will look for the script @file{c:/tmp/myscript}.
20096 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20097 each command as it is executed. The option must be given before
20098 @var{filename}, and is interpreted as part of the filename anywhere else.
20100 Commands that would ask for confirmation if used interactively proceed
20101 without asking when used in a command file. Many @value{GDBN} commands that
20102 normally print messages to say what they are doing omit the messages
20103 when called from command files.
20105 @value{GDBN} also accepts command input from standard input. In this
20106 mode, normal output goes to standard output and error output goes to
20107 standard error. Errors in a command file supplied on standard input do
20108 not terminate execution of the command file---execution continues with
20112 gdb < cmds > log 2>&1
20115 (The syntax above will vary depending on the shell used.) This example
20116 will execute commands from the file @file{cmds}. All output and errors
20117 would be directed to @file{log}.
20119 Since commands stored on command files tend to be more general than
20120 commands typed interactively, they frequently need to deal with
20121 complicated situations, such as different or unexpected values of
20122 variables and symbols, changes in how the program being debugged is
20123 built, etc. @value{GDBN} provides a set of flow-control commands to
20124 deal with these complexities. Using these commands, you can write
20125 complex scripts that loop over data structures, execute commands
20126 conditionally, etc.
20133 This command allows to include in your script conditionally executed
20134 commands. The @code{if} command takes a single argument, which is an
20135 expression to evaluate. It is followed by a series of commands that
20136 are executed only if the expression is true (its value is nonzero).
20137 There can then optionally be an @code{else} line, followed by a series
20138 of commands that are only executed if the expression was false. The
20139 end of the list is marked by a line containing @code{end}.
20143 This command allows to write loops. Its syntax is similar to
20144 @code{if}: the command takes a single argument, which is an expression
20145 to evaluate, and must be followed by the commands to execute, one per
20146 line, terminated by an @code{end}. These commands are called the
20147 @dfn{body} of the loop. The commands in the body of @code{while} are
20148 executed repeatedly as long as the expression evaluates to true.
20152 This command exits the @code{while} loop in whose body it is included.
20153 Execution of the script continues after that @code{while}s @code{end}
20156 @kindex loop_continue
20157 @item loop_continue
20158 This command skips the execution of the rest of the body of commands
20159 in the @code{while} loop in whose body it is included. Execution
20160 branches to the beginning of the @code{while} loop, where it evaluates
20161 the controlling expression.
20163 @kindex end@r{ (if/else/while commands)}
20165 Terminate the block of commands that are the body of @code{if},
20166 @code{else}, or @code{while} flow-control commands.
20171 @subsection Commands for Controlled Output
20173 During the execution of a command file or a user-defined command, normal
20174 @value{GDBN} output is suppressed; the only output that appears is what is
20175 explicitly printed by the commands in the definition. This section
20176 describes three commands useful for generating exactly the output you
20181 @item echo @var{text}
20182 @c I do not consider backslash-space a standard C escape sequence
20183 @c because it is not in ANSI.
20184 Print @var{text}. Nonprinting characters can be included in
20185 @var{text} using C escape sequences, such as @samp{\n} to print a
20186 newline. @strong{No newline is printed unless you specify one.}
20187 In addition to the standard C escape sequences, a backslash followed
20188 by a space stands for a space. This is useful for displaying a
20189 string with spaces at the beginning or the end, since leading and
20190 trailing spaces are otherwise trimmed from all arguments.
20191 To print @samp{@w{ }and foo =@w{ }}, use the command
20192 @samp{echo \@w{ }and foo = \@w{ }}.
20194 A backslash at the end of @var{text} can be used, as in C, to continue
20195 the command onto subsequent lines. For example,
20198 echo This is some text\n\
20199 which is continued\n\
20200 onto several lines.\n
20203 produces the same output as
20206 echo This is some text\n
20207 echo which is continued\n
20208 echo onto several lines.\n
20212 @item output @var{expression}
20213 Print the value of @var{expression} and nothing but that value: no
20214 newlines, no @samp{$@var{nn} = }. The value is not entered in the
20215 value history either. @xref{Expressions, ,Expressions}, for more information
20218 @item output/@var{fmt} @var{expression}
20219 Print the value of @var{expression} in format @var{fmt}. You can use
20220 the same formats as for @code{print}. @xref{Output Formats,,Output
20221 Formats}, for more information.
20224 @item printf @var{template}, @var{expressions}@dots{}
20225 Print the values of one or more @var{expressions} under the control of
20226 the string @var{template}. To print several values, make
20227 @var{expressions} be a comma-separated list of individual expressions,
20228 which may be either numbers or pointers. Their values are printed as
20229 specified by @var{template}, exactly as a C program would do by
20230 executing the code below:
20233 printf (@var{template}, @var{expressions}@dots{});
20236 As in @code{C} @code{printf}, ordinary characters in @var{template}
20237 are printed verbatim, while @dfn{conversion specification} introduced
20238 by the @samp{%} character cause subsequent @var{expressions} to be
20239 evaluated, their values converted and formatted according to type and
20240 style information encoded in the conversion specifications, and then
20243 For example, you can print two values in hex like this:
20246 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20249 @code{printf} supports all the standard @code{C} conversion
20250 specifications, including the flags and modifiers between the @samp{%}
20251 character and the conversion letter, with the following exceptions:
20255 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20258 The modifier @samp{*} is not supported for specifying precision or
20262 The @samp{'} flag (for separation of digits into groups according to
20263 @code{LC_NUMERIC'}) is not supported.
20266 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20270 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20273 The conversion letters @samp{a} and @samp{A} are not supported.
20277 Note that the @samp{ll} type modifier is supported only if the
20278 underlying @code{C} implementation used to build @value{GDBN} supports
20279 the @code{long long int} type, and the @samp{L} type modifier is
20280 supported only if @code{long double} type is available.
20282 As in @code{C}, @code{printf} supports simple backslash-escape
20283 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20284 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20285 single character. Octal and hexadecimal escape sequences are not
20288 Additionally, @code{printf} supports conversion specifications for DFP
20289 (@dfn{Decimal Floating Point}) types using the following length modifiers
20290 together with a floating point specifier.
20295 @samp{H} for printing @code{Decimal32} types.
20298 @samp{D} for printing @code{Decimal64} types.
20301 @samp{DD} for printing @code{Decimal128} types.
20304 If the underlying @code{C} implementation used to build @value{GDBN} has
20305 support for the three length modifiers for DFP types, other modifiers
20306 such as width and precision will also be available for @value{GDBN} to use.
20308 In case there is no such @code{C} support, no additional modifiers will be
20309 available and the value will be printed in the standard way.
20311 Here's an example of printing DFP types using the above conversion letters:
20313 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20317 @item eval @var{template}, @var{expressions}@dots{}
20318 Convert the values of one or more @var{expressions} under the control of
20319 the string @var{template} to a command line, and call it.
20324 @section Scripting @value{GDBN} using Python
20325 @cindex python scripting
20326 @cindex scripting with python
20328 You can script @value{GDBN} using the @uref{http://www.python.org/,
20329 Python programming language}. This feature is available only if
20330 @value{GDBN} was configured using @option{--with-python}.
20332 @cindex python directory
20333 Python scripts used by @value{GDBN} should be installed in
20334 @file{@var{data-directory}/python}, where @var{data-directory} is
20335 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}). This directory, known as the @dfn{python directory},
20336 is automatically added to the Python Search Path in order to allow
20337 the Python interpreter to locate all scripts installed at this location.
20340 * Python Commands:: Accessing Python from @value{GDBN}.
20341 * Python API:: Accessing @value{GDBN} from Python.
20342 * Auto-loading:: Automatically loading Python code.
20345 @node Python Commands
20346 @subsection Python Commands
20347 @cindex python commands
20348 @cindex commands to access python
20350 @value{GDBN} provides one command for accessing the Python interpreter,
20351 and one related setting:
20355 @item python @r{[}@var{code}@r{]}
20356 The @code{python} command can be used to evaluate Python code.
20358 If given an argument, the @code{python} command will evaluate the
20359 argument as a Python command. For example:
20362 (@value{GDBP}) python print 23
20366 If you do not provide an argument to @code{python}, it will act as a
20367 multi-line command, like @code{define}. In this case, the Python
20368 script is made up of subsequent command lines, given after the
20369 @code{python} command. This command list is terminated using a line
20370 containing @code{end}. For example:
20373 (@value{GDBP}) python
20375 End with a line saying just "end".
20381 @kindex maint set python print-stack
20382 @item maint set python print-stack
20383 By default, @value{GDBN} will print a stack trace when an error occurs
20384 in a Python script. This can be controlled using @code{maint set
20385 python print-stack}: if @code{on}, the default, then Python stack
20386 printing is enabled; if @code{off}, then Python stack printing is
20390 It is also possible to execute a Python script from the @value{GDBN}
20394 @item source @file{script-name}
20395 The script name must end with @samp{.py} and @value{GDBN} must be configured
20396 to recognize the script language based on filename extension using
20397 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20399 @item python execfile ("script-name")
20400 This method is based on the @code{execfile} Python built-in function,
20401 and thus is always available.
20405 @subsection Python API
20407 @cindex programming in python
20409 @cindex python stdout
20410 @cindex python pagination
20411 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20412 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20413 A Python program which outputs to one of these streams may have its
20414 output interrupted by the user (@pxref{Screen Size}). In this
20415 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20418 * Basic Python:: Basic Python Functions.
20419 * Exception Handling::
20420 * Values From Inferior::
20421 * Types In Python:: Python representation of types.
20422 * Pretty Printing API:: Pretty-printing values.
20423 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20424 * Disabling Pretty-Printers:: Disabling broken printers.
20425 * Inferiors In Python:: Python representation of inferiors (processes)
20426 * Threads In Python:: Accessing inferior threads from Python.
20427 * Commands In Python:: Implementing new commands in Python.
20428 * Parameters In Python:: Adding new @value{GDBN} parameters.
20429 * Functions In Python:: Writing new convenience functions.
20430 * Progspaces In Python:: Program spaces.
20431 * Objfiles In Python:: Object files.
20432 * Frames In Python:: Accessing inferior stack frames from Python.
20433 * Blocks In Python:: Accessing frame blocks from Python.
20434 * Symbols In Python:: Python representation of symbols.
20435 * Symbol Tables In Python:: Python representation of symbol tables.
20436 * Lazy Strings In Python:: Python representation of lazy strings.
20437 * Breakpoints In Python:: Manipulating breakpoints using Python.
20441 @subsubsection Basic Python
20443 @cindex python functions
20444 @cindex python module
20446 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20447 methods and classes added by @value{GDBN} are placed in this module.
20448 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20449 use in all scripts evaluated by the @code{python} command.
20451 @findex gdb.PYTHONDIR
20453 A string containing the python directory (@pxref{Python}).
20456 @findex gdb.execute
20457 @defun execute command [from_tty] [to_string]
20458 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20459 If a GDB exception happens while @var{command} runs, it is
20460 translated as described in @ref{Exception Handling,,Exception Handling}.
20462 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20463 command as having originated from the user invoking it interactively.
20464 It must be a boolean value. If omitted, it defaults to @code{False}.
20466 By default, any output produced by @var{command} is sent to
20467 @value{GDBN}'s standard output. If the @var{to_string} parameter is
20468 @code{True}, then output will be collected by @code{gdb.execute} and
20469 returned as a string. The default is @code{False}, in which case the
20470 return value is @code{None}.
20473 @findex gdb.breakpoints
20475 Return a sequence holding all of @value{GDBN}'s breakpoints.
20476 @xref{Breakpoints In Python}, for more information.
20479 @findex gdb.parameter
20480 @defun parameter parameter
20481 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20482 string naming the parameter to look up; @var{parameter} may contain
20483 spaces if the parameter has a multi-part name. For example,
20484 @samp{print object} is a valid parameter name.
20486 If the named parameter does not exist, this function throws a
20487 @code{RuntimeError}. Otherwise, the parameter's value is converted to
20488 a Python value of the appropriate type, and returned.
20491 @findex gdb.history
20492 @defun history number
20493 Return a value from @value{GDBN}'s value history (@pxref{Value
20494 History}). @var{number} indicates which history element to return.
20495 If @var{number} is negative, then @value{GDBN} will take its absolute value
20496 and count backward from the last element (i.e., the most recent element) to
20497 find the value to return. If @var{number} is zero, then @value{GDBN} will
20498 return the most recent element. If the element specified by @var{number}
20499 doesn't exist in the value history, a @code{RuntimeError} exception will be
20502 If no exception is raised, the return value is always an instance of
20503 @code{gdb.Value} (@pxref{Values From Inferior}).
20506 @findex gdb.parse_and_eval
20507 @defun parse_and_eval expression
20508 Parse @var{expression} as an expression in the current language,
20509 evaluate it, and return the result as a @code{gdb.Value}.
20510 @var{expression} must be a string.
20512 This function can be useful when implementing a new command
20513 (@pxref{Commands In Python}), as it provides a way to parse the
20514 command's argument as an expression. It is also useful simply to
20515 compute values, for example, it is the only way to get the value of a
20516 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20520 @defun write string
20521 Print a string to @value{GDBN}'s paginated standard output stream.
20522 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20523 call this function.
20528 Flush @value{GDBN}'s paginated standard output stream. Flushing
20529 @code{sys.stdout} or @code{sys.stderr} will automatically call this
20533 @findex gdb.target_charset
20534 @defun target_charset
20535 Return the name of the current target character set (@pxref{Character
20536 Sets}). This differs from @code{gdb.parameter('target-charset')} in
20537 that @samp{auto} is never returned.
20540 @findex gdb.target_wide_charset
20541 @defun target_wide_charset
20542 Return the name of the current target wide character set
20543 (@pxref{Character Sets}). This differs from
20544 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
20548 @node Exception Handling
20549 @subsubsection Exception Handling
20550 @cindex python exceptions
20551 @cindex exceptions, python
20553 When executing the @code{python} command, Python exceptions
20554 uncaught within the Python code are translated to calls to
20555 @value{GDBN} error-reporting mechanism. If the command that called
20556 @code{python} does not handle the error, @value{GDBN} will
20557 terminate it and print an error message containing the Python
20558 exception name, the associated value, and the Python call stack
20559 backtrace at the point where the exception was raised. Example:
20562 (@value{GDBP}) python print foo
20563 Traceback (most recent call last):
20564 File "<string>", line 1, in <module>
20565 NameError: name 'foo' is not defined
20568 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
20569 code are converted to Python @code{RuntimeError} exceptions. User
20570 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
20571 prompt) is translated to a Python @code{KeyboardInterrupt}
20572 exception. If you catch these exceptions in your Python code, your
20573 exception handler will see @code{RuntimeError} or
20574 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
20575 message as its value, and the Python call stack backtrace at the
20576 Python statement closest to where the @value{GDBN} error occured as the
20579 @findex gdb.GdbError
20580 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
20581 it is useful to be able to throw an exception that doesn't cause a
20582 traceback to be printed. For example, the user may have invoked the
20583 command incorrectly. Use the @code{gdb.GdbError} exception
20584 to handle this case. Example:
20588 >class HelloWorld (gdb.Command):
20589 > """Greet the whole world."""
20590 > def __init__ (self):
20591 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20592 > def invoke (self, args, from_tty):
20593 > argv = gdb.string_to_argv (args)
20594 > if len (argv) != 0:
20595 > raise gdb.GdbError ("hello-world takes no arguments")
20596 > print "Hello, World!"
20599 (gdb) hello-world 42
20600 hello-world takes no arguments
20603 @node Values From Inferior
20604 @subsubsection Values From Inferior
20605 @cindex values from inferior, with Python
20606 @cindex python, working with values from inferior
20608 @cindex @code{gdb.Value}
20609 @value{GDBN} provides values it obtains from the inferior program in
20610 an object of type @code{gdb.Value}. @value{GDBN} uses this object
20611 for its internal bookkeeping of the inferior's values, and for
20612 fetching values when necessary.
20614 Inferior values that are simple scalars can be used directly in
20615 Python expressions that are valid for the value's data type. Here's
20616 an example for an integer or floating-point value @code{some_val}:
20623 As result of this, @code{bar} will also be a @code{gdb.Value} object
20624 whose values are of the same type as those of @code{some_val}.
20626 Inferior values that are structures or instances of some class can
20627 be accessed using the Python @dfn{dictionary syntax}. For example, if
20628 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
20629 can access its @code{foo} element with:
20632 bar = some_val['foo']
20635 Again, @code{bar} will also be a @code{gdb.Value} object.
20637 A @code{gdb.Value} that represents a function can be executed via
20638 inferior function call. Any arguments provided to the call must match
20639 the function's prototype, and must be provided in the order specified
20642 For example, @code{some_val} is a @code{gdb.Value} instance
20643 representing a function that takes two integers as arguments. To
20644 execute this function, call it like so:
20647 result = some_val (10,20)
20650 Any values returned from a function call will be stored as a
20653 The following attributes are provided:
20656 @defivar Value address
20657 If this object is addressable, this read-only attribute holds a
20658 @code{gdb.Value} object representing the address. Otherwise,
20659 this attribute holds @code{None}.
20662 @cindex optimized out value in Python
20663 @defivar Value is_optimized_out
20664 This read-only boolean attribute is true if the compiler optimized out
20665 this value, thus it is not available for fetching from the inferior.
20668 @defivar Value type
20669 The type of this @code{gdb.Value}. The value of this attribute is a
20670 @code{gdb.Type} object.
20674 The following methods are provided:
20677 @defmethod Value cast type
20678 Return a new instance of @code{gdb.Value} that is the result of
20679 casting this instance to the type described by @var{type}, which must
20680 be a @code{gdb.Type} object. If the cast cannot be performed for some
20681 reason, this method throws an exception.
20684 @defmethod Value dereference
20685 For pointer data types, this method returns a new @code{gdb.Value} object
20686 whose contents is the object pointed to by the pointer. For example, if
20687 @code{foo} is a C pointer to an @code{int}, declared in your C program as
20694 then you can use the corresponding @code{gdb.Value} to access what
20695 @code{foo} points to like this:
20698 bar = foo.dereference ()
20701 The result @code{bar} will be a @code{gdb.Value} object holding the
20702 value pointed to by @code{foo}.
20705 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
20706 If this @code{gdb.Value} represents a string, then this method
20707 converts the contents to a Python string. Otherwise, this method will
20708 throw an exception.
20710 Strings are recognized in a language-specific way; whether a given
20711 @code{gdb.Value} represents a string is determined by the current
20714 For C-like languages, a value is a string if it is a pointer to or an
20715 array of characters or ints. The string is assumed to be terminated
20716 by a zero of the appropriate width. However if the optional length
20717 argument is given, the string will be converted to that given length,
20718 ignoring any embedded zeros that the string may contain.
20720 If the optional @var{encoding} argument is given, it must be a string
20721 naming the encoding of the string in the @code{gdb.Value}, such as
20722 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
20723 the same encodings as the corresponding argument to Python's
20724 @code{string.decode} method, and the Python codec machinery will be used
20725 to convert the string. If @var{encoding} is not given, or if
20726 @var{encoding} is the empty string, then either the @code{target-charset}
20727 (@pxref{Character Sets}) will be used, or a language-specific encoding
20728 will be used, if the current language is able to supply one.
20730 The optional @var{errors} argument is the same as the corresponding
20731 argument to Python's @code{string.decode} method.
20733 If the optional @var{length} argument is given, the string will be
20734 fetched and converted to the given length.
20737 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
20738 If this @code{gdb.Value} represents a string, then this method
20739 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
20740 In Python}). Otherwise, this method will throw an exception.
20742 If the optional @var{encoding} argument is given, it must be a string
20743 naming the encoding of the @code{gdb.LazyString}. Some examples are:
20744 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
20745 @var{encoding} argument is an encoding that @value{GDBN} does
20746 recognize, @value{GDBN} will raise an error.
20748 When a lazy string is printed, the @value{GDBN} encoding machinery is
20749 used to convert the string during printing. If the optional
20750 @var{encoding} argument is not provided, or is an empty string,
20751 @value{GDBN} will automatically select the encoding most suitable for
20752 the string type. For further information on encoding in @value{GDBN}
20753 please see @ref{Character Sets}.
20755 If the optional @var{length} argument is given, the string will be
20756 fetched and encoded to the length of characters specified. If
20757 the @var{length} argument is not provided, the string will be fetched
20758 and encoded until a null of appropriate width is found.
20762 @node Types In Python
20763 @subsubsection Types In Python
20764 @cindex types in Python
20765 @cindex Python, working with types
20768 @value{GDBN} represents types from the inferior using the class
20771 The following type-related functions are available in the @code{gdb}
20774 @findex gdb.lookup_type
20775 @defun lookup_type name [block]
20776 This function looks up a type by name. @var{name} is the name of the
20777 type to look up. It must be a string.
20779 If @var{block} is given, then @var{name} is looked up in that scope.
20780 Otherwise, it is searched for globally.
20782 Ordinarily, this function will return an instance of @code{gdb.Type}.
20783 If the named type cannot be found, it will throw an exception.
20786 An instance of @code{Type} has the following attributes:
20790 The type code for this type. The type code will be one of the
20791 @code{TYPE_CODE_} constants defined below.
20794 @defivar Type sizeof
20795 The size of this type, in target @code{char} units. Usually, a
20796 target's @code{char} type will be an 8-bit byte. However, on some
20797 unusual platforms, this type may have a different size.
20801 The tag name for this type. The tag name is the name after
20802 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
20803 languages have this concept. If this type has no tag name, then
20804 @code{None} is returned.
20808 The following methods are provided:
20811 @defmethod Type fields
20812 For structure and union types, this method returns the fields. Range
20813 types have two fields, the minimum and maximum values. Enum types
20814 have one field per enum constant. Function and method types have one
20815 field per parameter. The base types of C@t{++} classes are also
20816 represented as fields. If the type has no fields, or does not fit
20817 into one of these categories, an empty sequence will be returned.
20819 Each field is an object, with some pre-defined attributes:
20822 This attribute is not available for @code{static} fields (as in
20823 C@t{++} or Java). For non-@code{static} fields, the value is the bit
20824 position of the field.
20827 The name of the field, or @code{None} for anonymous fields.
20830 This is @code{True} if the field is artificial, usually meaning that
20831 it was provided by the compiler and not the user. This attribute is
20832 always provided, and is @code{False} if the field is not artificial.
20834 @item is_base_class
20835 This is @code{True} if the field represents a base class of a C@t{++}
20836 structure. This attribute is always provided, and is @code{False}
20837 if the field is not a base class of the type that is the argument of
20838 @code{fields}, or if that type was not a C@t{++} class.
20841 If the field is packed, or is a bitfield, then this will have a
20842 non-zero value, which is the size of the field in bits. Otherwise,
20843 this will be zero; in this case the field's size is given by its type.
20846 The type of the field. This is usually an instance of @code{Type},
20847 but it can be @code{None} in some situations.
20851 @defmethod Type const
20852 Return a new @code{gdb.Type} object which represents a
20853 @code{const}-qualified variant of this type.
20856 @defmethod Type volatile
20857 Return a new @code{gdb.Type} object which represents a
20858 @code{volatile}-qualified variant of this type.
20861 @defmethod Type unqualified
20862 Return a new @code{gdb.Type} object which represents an unqualified
20863 variant of this type. That is, the result is neither @code{const} nor
20867 @defmethod Type range
20868 Return a Python @code{Tuple} object that contains two elements: the
20869 low bound of the argument type and the high bound of that type. If
20870 the type does not have a range, @value{GDBN} will raise a
20871 @code{RuntimeError} exception.
20874 @defmethod Type reference
20875 Return a new @code{gdb.Type} object which represents a reference to this
20879 @defmethod Type pointer
20880 Return a new @code{gdb.Type} object which represents a pointer to this
20884 @defmethod Type strip_typedefs
20885 Return a new @code{gdb.Type} that represents the real type,
20886 after removing all layers of typedefs.
20889 @defmethod Type target
20890 Return a new @code{gdb.Type} object which represents the target type
20893 For a pointer type, the target type is the type of the pointed-to
20894 object. For an array type (meaning C-like arrays), the target type is
20895 the type of the elements of the array. For a function or method type,
20896 the target type is the type of the return value. For a complex type,
20897 the target type is the type of the elements. For a typedef, the
20898 target type is the aliased type.
20900 If the type does not have a target, this method will throw an
20904 @defmethod Type template_argument n [block]
20905 If this @code{gdb.Type} is an instantiation of a template, this will
20906 return a new @code{gdb.Type} which represents the type of the
20907 @var{n}th template argument.
20909 If this @code{gdb.Type} is not a template type, this will throw an
20910 exception. Ordinarily, only C@t{++} code will have template types.
20912 If @var{block} is given, then @var{name} is looked up in that scope.
20913 Otherwise, it is searched for globally.
20918 Each type has a code, which indicates what category this type falls
20919 into. The available type categories are represented by constants
20920 defined in the @code{gdb} module:
20923 @findex TYPE_CODE_PTR
20924 @findex gdb.TYPE_CODE_PTR
20925 @item TYPE_CODE_PTR
20926 The type is a pointer.
20928 @findex TYPE_CODE_ARRAY
20929 @findex gdb.TYPE_CODE_ARRAY
20930 @item TYPE_CODE_ARRAY
20931 The type is an array.
20933 @findex TYPE_CODE_STRUCT
20934 @findex gdb.TYPE_CODE_STRUCT
20935 @item TYPE_CODE_STRUCT
20936 The type is a structure.
20938 @findex TYPE_CODE_UNION
20939 @findex gdb.TYPE_CODE_UNION
20940 @item TYPE_CODE_UNION
20941 The type is a union.
20943 @findex TYPE_CODE_ENUM
20944 @findex gdb.TYPE_CODE_ENUM
20945 @item TYPE_CODE_ENUM
20946 The type is an enum.
20948 @findex TYPE_CODE_FLAGS
20949 @findex gdb.TYPE_CODE_FLAGS
20950 @item TYPE_CODE_FLAGS
20951 A bit flags type, used for things such as status registers.
20953 @findex TYPE_CODE_FUNC
20954 @findex gdb.TYPE_CODE_FUNC
20955 @item TYPE_CODE_FUNC
20956 The type is a function.
20958 @findex TYPE_CODE_INT
20959 @findex gdb.TYPE_CODE_INT
20960 @item TYPE_CODE_INT
20961 The type is an integer type.
20963 @findex TYPE_CODE_FLT
20964 @findex gdb.TYPE_CODE_FLT
20965 @item TYPE_CODE_FLT
20966 A floating point type.
20968 @findex TYPE_CODE_VOID
20969 @findex gdb.TYPE_CODE_VOID
20970 @item TYPE_CODE_VOID
20971 The special type @code{void}.
20973 @findex TYPE_CODE_SET
20974 @findex gdb.TYPE_CODE_SET
20975 @item TYPE_CODE_SET
20978 @findex TYPE_CODE_RANGE
20979 @findex gdb.TYPE_CODE_RANGE
20980 @item TYPE_CODE_RANGE
20981 A range type, that is, an integer type with bounds.
20983 @findex TYPE_CODE_STRING
20984 @findex gdb.TYPE_CODE_STRING
20985 @item TYPE_CODE_STRING
20986 A string type. Note that this is only used for certain languages with
20987 language-defined string types; C strings are not represented this way.
20989 @findex TYPE_CODE_BITSTRING
20990 @findex gdb.TYPE_CODE_BITSTRING
20991 @item TYPE_CODE_BITSTRING
20994 @findex TYPE_CODE_ERROR
20995 @findex gdb.TYPE_CODE_ERROR
20996 @item TYPE_CODE_ERROR
20997 An unknown or erroneous type.
20999 @findex TYPE_CODE_METHOD
21000 @findex gdb.TYPE_CODE_METHOD
21001 @item TYPE_CODE_METHOD
21002 A method type, as found in C@t{++} or Java.
21004 @findex TYPE_CODE_METHODPTR
21005 @findex gdb.TYPE_CODE_METHODPTR
21006 @item TYPE_CODE_METHODPTR
21007 A pointer-to-member-function.
21009 @findex TYPE_CODE_MEMBERPTR
21010 @findex gdb.TYPE_CODE_MEMBERPTR
21011 @item TYPE_CODE_MEMBERPTR
21012 A pointer-to-member.
21014 @findex TYPE_CODE_REF
21015 @findex gdb.TYPE_CODE_REF
21016 @item TYPE_CODE_REF
21019 @findex TYPE_CODE_CHAR
21020 @findex gdb.TYPE_CODE_CHAR
21021 @item TYPE_CODE_CHAR
21024 @findex TYPE_CODE_BOOL
21025 @findex gdb.TYPE_CODE_BOOL
21026 @item TYPE_CODE_BOOL
21029 @findex TYPE_CODE_COMPLEX
21030 @findex gdb.TYPE_CODE_COMPLEX
21031 @item TYPE_CODE_COMPLEX
21032 A complex float type.
21034 @findex TYPE_CODE_TYPEDEF
21035 @findex gdb.TYPE_CODE_TYPEDEF
21036 @item TYPE_CODE_TYPEDEF
21037 A typedef to some other type.
21039 @findex TYPE_CODE_NAMESPACE
21040 @findex gdb.TYPE_CODE_NAMESPACE
21041 @item TYPE_CODE_NAMESPACE
21042 A C@t{++} namespace.
21044 @findex TYPE_CODE_DECFLOAT
21045 @findex gdb.TYPE_CODE_DECFLOAT
21046 @item TYPE_CODE_DECFLOAT
21047 A decimal floating point type.
21049 @findex TYPE_CODE_INTERNAL_FUNCTION
21050 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
21051 @item TYPE_CODE_INTERNAL_FUNCTION
21052 A function internal to @value{GDBN}. This is the type used to represent
21053 convenience functions.
21056 @node Pretty Printing API
21057 @subsubsection Pretty Printing API
21059 An example output is provided (@pxref{Pretty Printing}).
21061 A pretty-printer is just an object that holds a value and implements a
21062 specific interface, defined here.
21064 @defop Operation {pretty printer} children (self)
21065 @value{GDBN} will call this method on a pretty-printer to compute the
21066 children of the pretty-printer's value.
21068 This method must return an object conforming to the Python iterator
21069 protocol. Each item returned by the iterator must be a tuple holding
21070 two elements. The first element is the ``name'' of the child; the
21071 second element is the child's value. The value can be any Python
21072 object which is convertible to a @value{GDBN} value.
21074 This method is optional. If it does not exist, @value{GDBN} will act
21075 as though the value has no children.
21078 @defop Operation {pretty printer} display_hint (self)
21079 The CLI may call this method and use its result to change the
21080 formatting of a value. The result will also be supplied to an MI
21081 consumer as a @samp{displayhint} attribute of the variable being
21084 This method is optional. If it does exist, this method must return a
21087 Some display hints are predefined by @value{GDBN}:
21091 Indicate that the object being printed is ``array-like''. The CLI
21092 uses this to respect parameters such as @code{set print elements} and
21093 @code{set print array}.
21096 Indicate that the object being printed is ``map-like'', and that the
21097 children of this value can be assumed to alternate between keys and
21101 Indicate that the object being printed is ``string-like''. If the
21102 printer's @code{to_string} method returns a Python string of some
21103 kind, then @value{GDBN} will call its internal language-specific
21104 string-printing function to format the string. For the CLI this means
21105 adding quotation marks, possibly escaping some characters, respecting
21106 @code{set print elements}, and the like.
21110 @defop Operation {pretty printer} to_string (self)
21111 @value{GDBN} will call this method to display the string
21112 representation of the value passed to the object's constructor.
21114 When printing from the CLI, if the @code{to_string} method exists,
21115 then @value{GDBN} will prepend its result to the values returned by
21116 @code{children}. Exactly how this formatting is done is dependent on
21117 the display hint, and may change as more hints are added. Also,
21118 depending on the print settings (@pxref{Print Settings}), the CLI may
21119 print just the result of @code{to_string} in a stack trace, omitting
21120 the result of @code{children}.
21122 If this method returns a string, it is printed verbatim.
21124 Otherwise, if this method returns an instance of @code{gdb.Value},
21125 then @value{GDBN} prints this value. This may result in a call to
21126 another pretty-printer.
21128 If instead the method returns a Python value which is convertible to a
21129 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
21130 the resulting value. Again, this may result in a call to another
21131 pretty-printer. Python scalars (integers, floats, and booleans) and
21132 strings are convertible to @code{gdb.Value}; other types are not.
21134 Finally, if this method returns @code{None} then no further operations
21135 are peformed in this method and nothing is printed.
21137 If the result is not one of these types, an exception is raised.
21140 @node Selecting Pretty-Printers
21141 @subsubsection Selecting Pretty-Printers
21143 The Python list @code{gdb.pretty_printers} contains an array of
21144 functions or callable objects that have been registered via addition
21145 as a pretty-printer.
21146 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
21147 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
21150 A function on one of these lists is passed a single @code{gdb.Value}
21151 argument and should return a pretty-printer object conforming to the
21152 interface definition above (@pxref{Pretty Printing API}). If a function
21153 cannot create a pretty-printer for the value, it should return
21156 @value{GDBN} first checks the @code{pretty_printers} attribute of each
21157 @code{gdb.Objfile} in the current program space and iteratively calls
21158 each enabled function (@pxref{Disabling Pretty-Printers})
21159 in the list for that @code{gdb.Objfile} until it receives
21160 a pretty-printer object.
21161 If no pretty-printer is found in the objfile lists, @value{GDBN} then
21162 searches the pretty-printer list of the current program space,
21163 calling each enabled function until an object is returned.
21164 After these lists have been exhausted, it tries the global
21165 @code{gdb.pretty_printers} list, again calling each enabled function until an
21166 object is returned.
21168 The order in which the objfiles are searched is not specified. For a
21169 given list, functions are always invoked from the head of the list,
21170 and iterated over sequentially until the end of the list, or a printer
21171 object is returned.
21173 Here is an example showing how a @code{std::string} printer might be
21177 class StdStringPrinter:
21178 "Print a std::string"
21180 def __init__ (self, val):
21183 def to_string (self):
21184 return self.val['_M_dataplus']['_M_p']
21186 def display_hint (self):
21190 And here is an example showing how a lookup function for the printer
21191 example above might be written.
21194 def str_lookup_function (val):
21196 lookup_tag = val.type.tag
21197 regex = re.compile ("^std::basic_string<char,.*>$")
21198 if lookup_tag == None:
21200 if regex.match (lookup_tag):
21201 return StdStringPrinter (val)
21206 The example lookup function extracts the value's type, and attempts to
21207 match it to a type that it can pretty-print. If it is a type the
21208 printer can pretty-print, it will return a printer object. If not, it
21209 returns @code{None}.
21211 We recommend that you put your core pretty-printers into a Python
21212 package. If your pretty-printers are for use with a library, we
21213 further recommend embedding a version number into the package name.
21214 This practice will enable @value{GDBN} to load multiple versions of
21215 your pretty-printers at the same time, because they will have
21218 You should write auto-loaded code (@pxref{Auto-loading}) such that it
21219 can be evaluated multiple times without changing its meaning. An
21220 ideal auto-load file will consist solely of @code{import}s of your
21221 printer modules, followed by a call to a register pretty-printers with
21222 the current objfile.
21224 Taken as a whole, this approach will scale nicely to multiple
21225 inferiors, each potentially using a different library version.
21226 Embedding a version number in the Python package name will ensure that
21227 @value{GDBN} is able to load both sets of printers simultaneously.
21228 Then, because the search for pretty-printers is done by objfile, and
21229 because your auto-loaded code took care to register your library's
21230 printers with a specific objfile, @value{GDBN} will find the correct
21231 printers for the specific version of the library used by each
21234 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
21235 this code might appear in @code{gdb.libstdcxx.v6}:
21238 def register_printers (objfile):
21239 objfile.pretty_printers.add (str_lookup_function)
21243 And then the corresponding contents of the auto-load file would be:
21246 import gdb.libstdcxx.v6
21247 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
21250 @node Disabling Pretty-Printers
21251 @subsubsection Disabling Pretty-Printers
21252 @cindex disabling pretty-printers
21254 For various reasons a pretty-printer may not work.
21255 For example, the underlying data structure may have changed and
21256 the pretty-printer is out of date.
21258 The consequences of a broken pretty-printer are severe enough that
21259 @value{GDBN} provides support for enabling and disabling individual
21260 printers. For example, if @code{print frame-arguments} is on,
21261 a backtrace can become highly illegible if any argument is printed
21262 with a broken printer.
21264 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21265 attribute to the registered function or callable object. If this attribute
21266 is present and its value is @code{False}, the printer is disabled, otherwise
21267 the printer is enabled.
21269 @node Inferiors In Python
21270 @subsubsection Inferiors In Python
21271 @cindex inferiors in python
21273 @findex gdb.Inferior
21274 Programs which are being run under @value{GDBN} are called inferiors
21275 (@pxref{Inferiors and Programs}). Python scripts can access
21276 information about and manipulate inferiors controlled by @value{GDBN}
21277 via objects of the @code{gdb.Inferior} class.
21279 The following inferior-related functions are available in the @code{gdb}
21283 Return a tuple containing all inferior objects.
21286 A @code{gdb.Inferior} object has the following attributes:
21289 @defivar Inferior num
21290 ID of inferior, as assigned by GDB.
21293 @defivar Inferior pid
21294 Process ID of the inferior, as assigned by the underlying operating
21298 @defivar Inferior was_attached
21299 Boolean signaling whether the inferior was created using `attach', or
21300 started by @value{GDBN} itself.
21304 A @code{gdb.Inferior} object has the following methods:
21307 @defmethod Inferior threads
21308 This method returns a tuple holding all the threads which are valid
21309 when it is called. If there are no valid threads, the method will
21310 return an empty tuple.
21313 @findex gdb.read_memory
21314 @defmethod Inferior read_memory address length
21315 Read @var{length} bytes of memory from the inferior, starting at
21316 @var{address}. Returns a buffer object, which behaves much like an array
21317 or a string. It can be modified and given to the @code{gdb.write_memory}
21321 @findex gdb.write_memory
21322 @defmethod Inferior write_memory address buffer @r{[}length@r{]}
21323 Write the contents of @var{buffer} to the inferior, starting at
21324 @var{address}. The @var{buffer} parameter must be a Python object
21325 which supports the buffer protocol, i.e., a string, an array or the
21326 object returned from @code{gdb.read_memory}. If given, @var{length}
21327 determines the number of bytes from @var{buffer} to be written.
21330 @findex gdb.search_memory
21331 @defmethod Inferior search_memory address length pattern
21332 Search a region of the inferior memory starting at @var{address} with
21333 the given @var{length} using the search pattern supplied in
21334 @var{pattern}. The @var{pattern} parameter must be a Python object
21335 which supports the buffer protocol, i.e., a string, an array or the
21336 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
21337 containing the address where the pattern was found, or @code{None} if
21338 the pattern could not be found.
21342 @node Threads In Python
21343 @subsubsection Threads In Python
21344 @cindex threads in python
21346 @findex gdb.InferiorThread
21347 Python scripts can access information about, and manipulate inferior threads
21348 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
21350 The following thread-related functions are available in the @code{gdb}
21353 @findex gdb.selected_thread
21354 @defun selected_thread
21355 This function returns the thread object for the selected thread. If there
21356 is no selected thread, this will return @code{None}.
21359 A @code{gdb.InferiorThread} object has the following attributes:
21362 @defivar InferiorThread num
21363 ID of the thread, as assigned by GDB.
21366 @defivar InferiorThread ptid
21367 ID of the thread, as assigned by the operating system. This attribute is a
21368 tuple containing three integers. The first is the Process ID (PID); the second
21369 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
21370 Either the LWPID or TID may be 0, which indicates that the operating system
21371 does not use that identifier.
21375 A @code{gdb.InferiorThread} object has the following methods:
21378 @defmethod InferiorThread switch
21379 This changes @value{GDBN}'s currently selected thread to the one represented
21383 @defmethod InferiorThread is_stopped
21384 Return a Boolean indicating whether the thread is stopped.
21387 @defmethod InferiorThread is_running
21388 Return a Boolean indicating whether the thread is running.
21391 @defmethod InferiorThread is_exited
21392 Return a Boolean indicating whether the thread is exited.
21396 @node Commands In Python
21397 @subsubsection Commands In Python
21399 @cindex commands in python
21400 @cindex python commands
21401 You can implement new @value{GDBN} CLI commands in Python. A CLI
21402 command is implemented using an instance of the @code{gdb.Command}
21403 class, most commonly using a subclass.
21405 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
21406 The object initializer for @code{Command} registers the new command
21407 with @value{GDBN}. This initializer is normally invoked from the
21408 subclass' own @code{__init__} method.
21410 @var{name} is the name of the command. If @var{name} consists of
21411 multiple words, then the initial words are looked for as prefix
21412 commands. In this case, if one of the prefix commands does not exist,
21413 an exception is raised.
21415 There is no support for multi-line commands.
21417 @var{command_class} should be one of the @samp{COMMAND_} constants
21418 defined below. This argument tells @value{GDBN} how to categorize the
21419 new command in the help system.
21421 @var{completer_class} is an optional argument. If given, it should be
21422 one of the @samp{COMPLETE_} constants defined below. This argument
21423 tells @value{GDBN} how to perform completion for this command. If not
21424 given, @value{GDBN} will attempt to complete using the object's
21425 @code{complete} method (see below); if no such method is found, an
21426 error will occur when completion is attempted.
21428 @var{prefix} is an optional argument. If @code{True}, then the new
21429 command is a prefix command; sub-commands of this command may be
21432 The help text for the new command is taken from the Python
21433 documentation string for the command's class, if there is one. If no
21434 documentation string is provided, the default value ``This command is
21435 not documented.'' is used.
21438 @cindex don't repeat Python command
21439 @defmethod Command dont_repeat
21440 By default, a @value{GDBN} command is repeated when the user enters a
21441 blank line at the command prompt. A command can suppress this
21442 behavior by invoking the @code{dont_repeat} method. This is similar
21443 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
21446 @defmethod Command invoke argument from_tty
21447 This method is called by @value{GDBN} when this command is invoked.
21449 @var{argument} is a string. It is the argument to the command, after
21450 leading and trailing whitespace has been stripped.
21452 @var{from_tty} is a boolean argument. When true, this means that the
21453 command was entered by the user at the terminal; when false it means
21454 that the command came from elsewhere.
21456 If this method throws an exception, it is turned into a @value{GDBN}
21457 @code{error} call. Otherwise, the return value is ignored.
21459 @findex gdb.string_to_argv
21460 To break @var{argument} up into an argv-like string use
21461 @code{gdb.string_to_argv}. This function behaves identically to
21462 @value{GDBN}'s internal argument lexer @code{buildargv}.
21463 It is recommended to use this for consistency.
21464 Arguments are separated by spaces and may be quoted.
21468 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
21469 ['1', '2 "3', '4 "5', "6 '7"]
21474 @cindex completion of Python commands
21475 @defmethod Command complete text word
21476 This method is called by @value{GDBN} when the user attempts
21477 completion on this command. All forms of completion are handled by
21478 this method, that is, the @key{TAB} and @key{M-?} key bindings
21479 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
21482 The arguments @var{text} and @var{word} are both strings. @var{text}
21483 holds the complete command line up to the cursor's location.
21484 @var{word} holds the last word of the command line; this is computed
21485 using a word-breaking heuristic.
21487 The @code{complete} method can return several values:
21490 If the return value is a sequence, the contents of the sequence are
21491 used as the completions. It is up to @code{complete} to ensure that the
21492 contents actually do complete the word. A zero-length sequence is
21493 allowed, it means that there were no completions available. Only
21494 string elements of the sequence are used; other elements in the
21495 sequence are ignored.
21498 If the return value is one of the @samp{COMPLETE_} constants defined
21499 below, then the corresponding @value{GDBN}-internal completion
21500 function is invoked, and its result is used.
21503 All other results are treated as though there were no available
21508 When a new command is registered, it must be declared as a member of
21509 some general class of commands. This is used to classify top-level
21510 commands in the on-line help system; note that prefix commands are not
21511 listed under their own category but rather that of their top-level
21512 command. The available classifications are represented by constants
21513 defined in the @code{gdb} module:
21516 @findex COMMAND_NONE
21517 @findex gdb.COMMAND_NONE
21519 The command does not belong to any particular class. A command in
21520 this category will not be displayed in any of the help categories.
21522 @findex COMMAND_RUNNING
21523 @findex gdb.COMMAND_RUNNING
21524 @item COMMAND_RUNNING
21525 The command is related to running the inferior. For example,
21526 @code{start}, @code{step}, and @code{continue} are in this category.
21527 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
21528 commands in this category.
21530 @findex COMMAND_DATA
21531 @findex gdb.COMMAND_DATA
21533 The command is related to data or variables. For example,
21534 @code{call}, @code{find}, and @code{print} are in this category. Type
21535 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
21538 @findex COMMAND_STACK
21539 @findex gdb.COMMAND_STACK
21540 @item COMMAND_STACK
21541 The command has to do with manipulation of the stack. For example,
21542 @code{backtrace}, @code{frame}, and @code{return} are in this
21543 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
21544 list of commands in this category.
21546 @findex COMMAND_FILES
21547 @findex gdb.COMMAND_FILES
21548 @item COMMAND_FILES
21549 This class is used for file-related commands. For example,
21550 @code{file}, @code{list} and @code{section} are in this category.
21551 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
21552 commands in this category.
21554 @findex COMMAND_SUPPORT
21555 @findex gdb.COMMAND_SUPPORT
21556 @item COMMAND_SUPPORT
21557 This should be used for ``support facilities'', generally meaning
21558 things that are useful to the user when interacting with @value{GDBN},
21559 but not related to the state of the inferior. For example,
21560 @code{help}, @code{make}, and @code{shell} are in this category. Type
21561 @kbd{help support} at the @value{GDBN} prompt to see a list of
21562 commands in this category.
21564 @findex COMMAND_STATUS
21565 @findex gdb.COMMAND_STATUS
21566 @item COMMAND_STATUS
21567 The command is an @samp{info}-related command, that is, related to the
21568 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
21569 and @code{show} are in this category. Type @kbd{help status} at the
21570 @value{GDBN} prompt to see a list of commands in this category.
21572 @findex COMMAND_BREAKPOINTS
21573 @findex gdb.COMMAND_BREAKPOINTS
21574 @item COMMAND_BREAKPOINTS
21575 The command has to do with breakpoints. For example, @code{break},
21576 @code{clear}, and @code{delete} are in this category. Type @kbd{help
21577 breakpoints} at the @value{GDBN} prompt to see a list of commands in
21580 @findex COMMAND_TRACEPOINTS
21581 @findex gdb.COMMAND_TRACEPOINTS
21582 @item COMMAND_TRACEPOINTS
21583 The command has to do with tracepoints. For example, @code{trace},
21584 @code{actions}, and @code{tfind} are in this category. Type
21585 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
21586 commands in this category.
21588 @findex COMMAND_OBSCURE
21589 @findex gdb.COMMAND_OBSCURE
21590 @item COMMAND_OBSCURE
21591 The command is only used in unusual circumstances, or is not of
21592 general interest to users. For example, @code{checkpoint},
21593 @code{fork}, and @code{stop} are in this category. Type @kbd{help
21594 obscure} at the @value{GDBN} prompt to see a list of commands in this
21597 @findex COMMAND_MAINTENANCE
21598 @findex gdb.COMMAND_MAINTENANCE
21599 @item COMMAND_MAINTENANCE
21600 The command is only useful to @value{GDBN} maintainers. The
21601 @code{maintenance} and @code{flushregs} commands are in this category.
21602 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
21603 commands in this category.
21606 A new command can use a predefined completion function, either by
21607 specifying it via an argument at initialization, or by returning it
21608 from the @code{complete} method. These predefined completion
21609 constants are all defined in the @code{gdb} module:
21612 @findex COMPLETE_NONE
21613 @findex gdb.COMPLETE_NONE
21614 @item COMPLETE_NONE
21615 This constant means that no completion should be done.
21617 @findex COMPLETE_FILENAME
21618 @findex gdb.COMPLETE_FILENAME
21619 @item COMPLETE_FILENAME
21620 This constant means that filename completion should be performed.
21622 @findex COMPLETE_LOCATION
21623 @findex gdb.COMPLETE_LOCATION
21624 @item COMPLETE_LOCATION
21625 This constant means that location completion should be done.
21626 @xref{Specify Location}.
21628 @findex COMPLETE_COMMAND
21629 @findex gdb.COMPLETE_COMMAND
21630 @item COMPLETE_COMMAND
21631 This constant means that completion should examine @value{GDBN}
21634 @findex COMPLETE_SYMBOL
21635 @findex gdb.COMPLETE_SYMBOL
21636 @item COMPLETE_SYMBOL
21637 This constant means that completion should be done using symbol names
21641 The following code snippet shows how a trivial CLI command can be
21642 implemented in Python:
21645 class HelloWorld (gdb.Command):
21646 """Greet the whole world."""
21648 def __init__ (self):
21649 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21651 def invoke (self, arg, from_tty):
21652 print "Hello, World!"
21657 The last line instantiates the class, and is necessary to trigger the
21658 registration of the command with @value{GDBN}. Depending on how the
21659 Python code is read into @value{GDBN}, you may need to import the
21660 @code{gdb} module explicitly.
21662 @node Parameters In Python
21663 @subsubsection Parameters In Python
21665 @cindex parameters in python
21666 @cindex python parameters
21667 @tindex gdb.Parameter
21669 You can implement new @value{GDBN} parameters using Python. A new
21670 parameter is implemented as an instance of the @code{gdb.Parameter}
21673 Parameters are exposed to the user via the @code{set} and
21674 @code{show} commands. @xref{Help}.
21676 There are many parameters that already exist and can be set in
21677 @value{GDBN}. Two examples are: @code{set follow fork} and
21678 @code{set charset}. Setting these parameters influences certain
21679 behavior in @value{GDBN}. Similarly, you can define parameters that
21680 can be used to influence behavior in custom Python scripts and commands.
21682 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
21683 The object initializer for @code{Parameter} registers the new
21684 parameter with @value{GDBN}. This initializer is normally invoked
21685 from the subclass' own @code{__init__} method.
21687 @var{name} is the name of the new parameter. If @var{name} consists
21688 of multiple words, then the initial words are looked for as prefix
21689 parameters. An example of this can be illustrated with the
21690 @code{set print} set of parameters. If @var{name} is
21691 @code{print foo}, then @code{print} will be searched as the prefix
21692 parameter. In this case the parameter can subsequently be accessed in
21693 @value{GDBN} as @code{set print foo}.
21695 If @var{name} consists of multiple words, and no prefix parameter group
21696 can be found, an exception is raised.
21698 @var{command-class} should be one of the @samp{COMMAND_} constants
21699 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
21700 categorize the new parameter in the help system.
21702 @var{parameter-class} should be one of the @samp{PARAM_} constants
21703 defined below. This argument tells @value{GDBN} the type of the new
21704 parameter; this information is used for input validation and
21707 If @var{parameter-class} is @code{PARAM_ENUM}, then
21708 @var{enum-sequence} must be a sequence of strings. These strings
21709 represent the possible values for the parameter.
21711 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
21712 of a fourth argument will cause an exception to be thrown.
21714 The help text for the new parameter is taken from the Python
21715 documentation string for the parameter's class, if there is one. If
21716 there is no documentation string, a default value is used.
21719 @defivar Parameter set_doc
21720 If this attribute exists, and is a string, then its value is used as
21721 the help text for this parameter's @code{set} command. The value is
21722 examined when @code{Parameter.__init__} is invoked; subsequent changes
21726 @defivar Parameter show_doc
21727 If this attribute exists, and is a string, then its value is used as
21728 the help text for this parameter's @code{show} command. The value is
21729 examined when @code{Parameter.__init__} is invoked; subsequent changes
21733 @defivar Parameter value
21734 The @code{value} attribute holds the underlying value of the
21735 parameter. It can be read and assigned to just as any other
21736 attribute. @value{GDBN} does validation when assignments are made.
21740 When a new parameter is defined, its type must be specified. The
21741 available types are represented by constants defined in the @code{gdb}
21745 @findex PARAM_BOOLEAN
21746 @findex gdb.PARAM_BOOLEAN
21747 @item PARAM_BOOLEAN
21748 The value is a plain boolean. The Python boolean values, @code{True}
21749 and @code{False} are the only valid values.
21751 @findex PARAM_AUTO_BOOLEAN
21752 @findex gdb.PARAM_AUTO_BOOLEAN
21753 @item PARAM_AUTO_BOOLEAN
21754 The value has three possible states: true, false, and @samp{auto}. In
21755 Python, true and false are represented using boolean constants, and
21756 @samp{auto} is represented using @code{None}.
21758 @findex PARAM_UINTEGER
21759 @findex gdb.PARAM_UINTEGER
21760 @item PARAM_UINTEGER
21761 The value is an unsigned integer. The value of 0 should be
21762 interpreted to mean ``unlimited''.
21764 @findex PARAM_INTEGER
21765 @findex gdb.PARAM_INTEGER
21766 @item PARAM_INTEGER
21767 The value is a signed integer. The value of 0 should be interpreted
21768 to mean ``unlimited''.
21770 @findex PARAM_STRING
21771 @findex gdb.PARAM_STRING
21773 The value is a string. When the user modifies the string, any escape
21774 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
21775 translated into corresponding characters and encoded into the current
21778 @findex PARAM_STRING_NOESCAPE
21779 @findex gdb.PARAM_STRING_NOESCAPE
21780 @item PARAM_STRING_NOESCAPE
21781 The value is a string. When the user modifies the string, escapes are
21782 passed through untranslated.
21784 @findex PARAM_OPTIONAL_FILENAME
21785 @findex gdb.PARAM_OPTIONAL_FILENAME
21786 @item PARAM_OPTIONAL_FILENAME
21787 The value is a either a filename (a string), or @code{None}.
21789 @findex PARAM_FILENAME
21790 @findex gdb.PARAM_FILENAME
21791 @item PARAM_FILENAME
21792 The value is a filename. This is just like
21793 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
21795 @findex PARAM_ZINTEGER
21796 @findex gdb.PARAM_ZINTEGER
21797 @item PARAM_ZINTEGER
21798 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
21799 is interpreted as itself.
21802 @findex gdb.PARAM_ENUM
21804 The value is a string, which must be one of a collection string
21805 constants provided when the parameter is created.
21808 @node Functions In Python
21809 @subsubsection Writing new convenience functions
21811 @cindex writing convenience functions
21812 @cindex convenience functions in python
21813 @cindex python convenience functions
21814 @tindex gdb.Function
21816 You can implement new convenience functions (@pxref{Convenience Vars})
21817 in Python. A convenience function is an instance of a subclass of the
21818 class @code{gdb.Function}.
21820 @defmethod Function __init__ name
21821 The initializer for @code{Function} registers the new function with
21822 @value{GDBN}. The argument @var{name} is the name of the function,
21823 a string. The function will be visible to the user as a convenience
21824 variable of type @code{internal function}, whose name is the same as
21825 the given @var{name}.
21827 The documentation for the new function is taken from the documentation
21828 string for the new class.
21831 @defmethod Function invoke @var{*args}
21832 When a convenience function is evaluated, its arguments are converted
21833 to instances of @code{gdb.Value}, and then the function's
21834 @code{invoke} method is called. Note that @value{GDBN} does not
21835 predetermine the arity of convenience functions. Instead, all
21836 available arguments are passed to @code{invoke}, following the
21837 standard Python calling convention. In particular, a convenience
21838 function can have default values for parameters without ill effect.
21840 The return value of this method is used as its value in the enclosing
21841 expression. If an ordinary Python value is returned, it is converted
21842 to a @code{gdb.Value} following the usual rules.
21845 The following code snippet shows how a trivial convenience function can
21846 be implemented in Python:
21849 class Greet (gdb.Function):
21850 """Return string to greet someone.
21851 Takes a name as argument."""
21853 def __init__ (self):
21854 super (Greet, self).__init__ ("greet")
21856 def invoke (self, name):
21857 return "Hello, %s!" % name.string ()
21862 The last line instantiates the class, and is necessary to trigger the
21863 registration of the function with @value{GDBN}. Depending on how the
21864 Python code is read into @value{GDBN}, you may need to import the
21865 @code{gdb} module explicitly.
21867 @node Progspaces In Python
21868 @subsubsection Program Spaces In Python
21870 @cindex progspaces in python
21871 @tindex gdb.Progspace
21873 A program space, or @dfn{progspace}, represents a symbolic view
21874 of an address space.
21875 It consists of all of the objfiles of the program.
21876 @xref{Objfiles In Python}.
21877 @xref{Inferiors and Programs, program spaces}, for more details
21878 about program spaces.
21880 The following progspace-related functions are available in the
21883 @findex gdb.current_progspace
21884 @defun current_progspace
21885 This function returns the program space of the currently selected inferior.
21886 @xref{Inferiors and Programs}.
21889 @findex gdb.progspaces
21891 Return a sequence of all the progspaces currently known to @value{GDBN}.
21894 Each progspace is represented by an instance of the @code{gdb.Progspace}
21897 @defivar Progspace filename
21898 The file name of the progspace as a string.
21901 @defivar Progspace pretty_printers
21902 The @code{pretty_printers} attribute is a list of functions. It is
21903 used to look up pretty-printers. A @code{Value} is passed to each
21904 function in order; if the function returns @code{None}, then the
21905 search continues. Otherwise, the return value should be an object
21906 which is used to format the value. @xref{Pretty Printing API}, for more
21910 @node Objfiles In Python
21911 @subsubsection Objfiles In Python
21913 @cindex objfiles in python
21914 @tindex gdb.Objfile
21916 @value{GDBN} loads symbols for an inferior from various
21917 symbol-containing files (@pxref{Files}). These include the primary
21918 executable file, any shared libraries used by the inferior, and any
21919 separate debug info files (@pxref{Separate Debug Files}).
21920 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
21922 The following objfile-related functions are available in the
21925 @findex gdb.current_objfile
21926 @defun current_objfile
21927 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
21928 sets the ``current objfile'' to the corresponding objfile. This
21929 function returns the current objfile. If there is no current objfile,
21930 this function returns @code{None}.
21933 @findex gdb.objfiles
21935 Return a sequence of all the objfiles current known to @value{GDBN}.
21936 @xref{Objfiles In Python}.
21939 Each objfile is represented by an instance of the @code{gdb.Objfile}
21942 @defivar Objfile filename
21943 The file name of the objfile as a string.
21946 @defivar Objfile pretty_printers
21947 The @code{pretty_printers} attribute is a list of functions. It is
21948 used to look up pretty-printers. A @code{Value} is passed to each
21949 function in order; if the function returns @code{None}, then the
21950 search continues. Otherwise, the return value should be an object
21951 which is used to format the value. @xref{Pretty Printing API}, for more
21955 @node Frames In Python
21956 @subsubsection Accessing inferior stack frames from Python.
21958 @cindex frames in python
21959 When the debugged program stops, @value{GDBN} is able to analyze its call
21960 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
21961 represents a frame in the stack. A @code{gdb.Frame} object is only valid
21962 while its corresponding frame exists in the inferior's stack. If you try
21963 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
21966 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
21970 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
21974 The following frame-related functions are available in the @code{gdb} module:
21976 @findex gdb.selected_frame
21977 @defun selected_frame
21978 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
21981 @defun frame_stop_reason_string reason
21982 Return a string explaining the reason why @value{GDBN} stopped unwinding
21983 frames, as expressed by the given @var{reason} code (an integer, see the
21984 @code{unwind_stop_reason} method further down in this section).
21987 A @code{gdb.Frame} object has the following methods:
21990 @defmethod Frame is_valid
21991 Returns true if the @code{gdb.Frame} object is valid, false if not.
21992 A frame object can become invalid if the frame it refers to doesn't
21993 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
21994 an exception if it is invalid at the time the method is called.
21997 @defmethod Frame name
21998 Returns the function name of the frame, or @code{None} if it can't be
22002 @defmethod Frame type
22003 Returns the type of the frame. The value can be one of
22004 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
22005 or @code{gdb.SENTINEL_FRAME}.
22008 @defmethod Frame unwind_stop_reason
22009 Return an integer representing the reason why it's not possible to find
22010 more frames toward the outermost frame. Use
22011 @code{gdb.frame_stop_reason_string} to convert the value returned by this
22012 function to a string.
22015 @defmethod Frame pc
22016 Returns the frame's resume address.
22019 @defmethod Frame block
22020 Return the frame's code block. @xref{Blocks In Python}.
22023 @defmethod Frame function
22024 Return the symbol for the function corresponding to this frame.
22025 @xref{Symbols In Python}.
22028 @defmethod Frame older
22029 Return the frame that called this frame.
22032 @defmethod Frame newer
22033 Return the frame called by this frame.
22036 @defmethod Frame find_sal
22037 Return the frame's symtab and line object.
22038 @xref{Symbol Tables In Python}.
22041 @defmethod Frame read_var variable @r{[}block@r{]}
22042 Return the value of @var{variable} in this frame. If the optional
22043 argument @var{block} is provided, search for the variable from that
22044 block; otherwise start at the frame's current block (which is
22045 determined by the frame's current program counter). @var{variable}
22046 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
22047 @code{gdb.Block} object.
22050 @defmethod Frame select
22051 Set this frame to be the selected frame. @xref{Stack, ,Examining the
22056 @node Blocks In Python
22057 @subsubsection Accessing frame blocks from Python.
22059 @cindex blocks in python
22062 Within each frame, @value{GDBN} maintains information on each block
22063 stored in that frame. These blocks are organized hierarchically, and
22064 are represented individually in Python as a @code{gdb.Block}.
22065 Please see @ref{Frames In Python}, for a more in-depth discussion on
22066 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
22067 detailed technical information on @value{GDBN}'s book-keeping of the
22070 The following block-related functions are available in the @code{gdb}
22073 @findex gdb.block_for_pc
22074 @defun block_for_pc pc
22075 Return the @code{gdb.Block} containing the given @var{pc} value. If the
22076 block cannot be found for the @var{pc} value specified, the function
22077 will return @code{None}.
22080 A @code{gdb.Block} object has the following attributes:
22083 @defivar Block start
22084 The start address of the block. This attribute is not writable.
22088 The end address of the block. This attribute is not writable.
22091 @defivar Block function
22092 The name of the block represented as a @code{gdb.Symbol}. If the
22093 block is not named, then this attribute holds @code{None}. This
22094 attribute is not writable.
22097 @defivar Block superblock
22098 The block containing this block. If this parent block does not exist,
22099 this attribute holds @code{None}. This attribute is not writable.
22103 @node Symbols In Python
22104 @subsubsection Python representation of Symbols.
22106 @cindex symbols in python
22109 @value{GDBN} represents every variable, function and type as an
22110 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
22111 Similarly, Python represents these symbols in @value{GDBN} with the
22112 @code{gdb.Symbol} object.
22114 The following symbol-related functions are available in the @code{gdb}
22117 @findex gdb.lookup_symbol
22118 @defun lookup_symbol name [block] [domain]
22119 This function searches for a symbol by name. The search scope can be
22120 restricted to the parameters defined in the optional domain and block
22123 @var{name} is the name of the symbol. It must be a string. The
22124 optional @var{block} argument restricts the search to symbols visible
22125 in that @var{block}. The @var{block} argument must be a
22126 @code{gdb.Block} object. The optional @var{domain} argument restricts
22127 the search to the domain type. The @var{domain} argument must be a
22128 domain constant defined in the @code{gdb} module and described later
22132 A @code{gdb.Symbol} object has the following attributes:
22135 @defivar Symbol symtab
22136 The symbol table in which the symbol appears. This attribute is
22137 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
22138 Python}. This attribute is not writable.
22141 @defivar Symbol name
22142 The name of the symbol as a string. This attribute is not writable.
22145 @defivar Symbol linkage_name
22146 The name of the symbol, as used by the linker (i.e., may be mangled).
22147 This attribute is not writable.
22150 @defivar Symbol print_name
22151 The name of the symbol in a form suitable for output. This is either
22152 @code{name} or @code{linkage_name}, depending on whether the user
22153 asked @value{GDBN} to display demangled or mangled names.
22156 @defivar Symbol addr_class
22157 The address class of the symbol. This classifies how to find the value
22158 of a symbol. Each address class is a constant defined in the
22159 @code{gdb} module and described later in this chapter.
22162 @defivar Symbol is_argument
22163 @code{True} if the symbol is an argument of a function.
22166 @defivar Symbol is_constant
22167 @code{True} if the symbol is a constant.
22170 @defivar Symbol is_function
22171 @code{True} if the symbol is a function or a method.
22174 @defivar Symbol is_variable
22175 @code{True} if the symbol is a variable.
22179 The available domain categories in @code{gdb.Symbol} are represented
22180 as constants in the @code{gdb} module:
22183 @findex SYMBOL_UNDEF_DOMAIN
22184 @findex gdb.SYMBOL_UNDEF_DOMAIN
22185 @item SYMBOL_UNDEF_DOMAIN
22186 This is used when a domain has not been discovered or none of the
22187 following domains apply. This usually indicates an error either
22188 in the symbol information or in @value{GDBN}'s handling of symbols.
22189 @findex SYMBOL_VAR_DOMAIN
22190 @findex gdb.SYMBOL_VAR_DOMAIN
22191 @item SYMBOL_VAR_DOMAIN
22192 This domain contains variables, function names, typedef names and enum
22194 @findex SYMBOL_STRUCT_DOMAIN
22195 @findex gdb.SYMBOL_STRUCT_DOMAIN
22196 @item SYMBOL_STRUCT_DOMAIN
22197 This domain holds struct, union and enum type names.
22198 @findex SYMBOL_LABEL_DOMAIN
22199 @findex gdb.SYMBOL_LABEL_DOMAIN
22200 @item SYMBOL_LABEL_DOMAIN
22201 This domain contains names of labels (for gotos).
22202 @findex SYMBOL_VARIABLES_DOMAIN
22203 @findex gdb.SYMBOL_VARIABLES_DOMAIN
22204 @item SYMBOL_VARIABLES_DOMAIN
22205 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
22206 contains everything minus functions and types.
22207 @findex SYMBOL_FUNCTIONS_DOMAIN
22208 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
22209 @item SYMBOL_FUNCTION_DOMAIN
22210 This domain contains all functions.
22211 @findex SYMBOL_TYPES_DOMAIN
22212 @findex gdb.SYMBOL_TYPES_DOMAIN
22213 @item SYMBOL_TYPES_DOMAIN
22214 This domain contains all types.
22217 The available address class categories in @code{gdb.Symbol} are represented
22218 as constants in the @code{gdb} module:
22221 @findex SYMBOL_LOC_UNDEF
22222 @findex gdb.SYMBOL_LOC_UNDEF
22223 @item SYMBOL_LOC_UNDEF
22224 If this is returned by address class, it indicates an error either in
22225 the symbol information or in @value{GDBN}'s handling of symbols.
22226 @findex SYMBOL_LOC_CONST
22227 @findex gdb.SYMBOL_LOC_CONST
22228 @item SYMBOL_LOC_CONST
22229 Value is constant int.
22230 @findex SYMBOL_LOC_STATIC
22231 @findex gdb.SYMBOL_LOC_STATIC
22232 @item SYMBOL_LOC_STATIC
22233 Value is at a fixed address.
22234 @findex SYMBOL_LOC_REGISTER
22235 @findex gdb.SYMBOL_LOC_REGISTER
22236 @item SYMBOL_LOC_REGISTER
22237 Value is in a register.
22238 @findex SYMBOL_LOC_ARG
22239 @findex gdb.SYMBOL_LOC_ARG
22240 @item SYMBOL_LOC_ARG
22241 Value is an argument. This value is at the offset stored within the
22242 symbol inside the frame's argument list.
22243 @findex SYMBOL_LOC_REF_ARG
22244 @findex gdb.SYMBOL_LOC_REF_ARG
22245 @item SYMBOL_LOC_REF_ARG
22246 Value address is stored in the frame's argument list. Just like
22247 @code{LOC_ARG} except that the value's address is stored at the
22248 offset, not the value itself.
22249 @findex SYMBOL_LOC_REGPARM_ADDR
22250 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
22251 @item SYMBOL_LOC_REGPARM_ADDR
22252 Value is a specified register. Just like @code{LOC_REGISTER} except
22253 the register holds the address of the argument instead of the argument
22255 @findex SYMBOL_LOC_LOCAL
22256 @findex gdb.SYMBOL_LOC_LOCAL
22257 @item SYMBOL_LOC_LOCAL
22258 Value is a local variable.
22259 @findex SYMBOL_LOC_TYPEDEF
22260 @findex gdb.SYMBOL_LOC_TYPEDEF
22261 @item SYMBOL_LOC_TYPEDEF
22262 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
22264 @findex SYMBOL_LOC_BLOCK
22265 @findex gdb.SYMBOL_LOC_BLOCK
22266 @item SYMBOL_LOC_BLOCK
22268 @findex SYMBOL_LOC_CONST_BYTES
22269 @findex gdb.SYMBOL_LOC_CONST_BYTES
22270 @item SYMBOL_LOC_CONST_BYTES
22271 Value is a byte-sequence.
22272 @findex SYMBOL_LOC_UNRESOLVED
22273 @findex gdb.SYMBOL_LOC_UNRESOLVED
22274 @item SYMBOL_LOC_UNRESOLVED
22275 Value is at a fixed address, but the address of the variable has to be
22276 determined from the minimal symbol table whenever the variable is
22278 @findex SYMBOL_LOC_OPTIMIZED_OUT
22279 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
22280 @item SYMBOL_LOC_OPTIMIZED_OUT
22281 The value does not actually exist in the program.
22282 @findex SYMBOL_LOC_COMPUTED
22283 @findex gdb.SYMBOL_LOC_COMPUTED
22284 @item SYMBOL_LOC_COMPUTED
22285 The value's address is a computed location.
22288 @node Symbol Tables In Python
22289 @subsubsection Symbol table representation in Python.
22291 @cindex symbol tables in python
22293 @tindex gdb.Symtab_and_line
22295 Access to symbol table data maintained by @value{GDBN} on the inferior
22296 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
22297 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
22298 from the @code{find_sal} method in @code{gdb.Frame} object.
22299 @xref{Frames In Python}.
22301 For more information on @value{GDBN}'s symbol table management, see
22302 @ref{Symbols, ,Examining the Symbol Table}, for more information.
22304 A @code{gdb.Symtab_and_line} object has the following attributes:
22307 @defivar Symtab_and_line symtab
22308 The symbol table object (@code{gdb.Symtab}) for this frame.
22309 This attribute is not writable.
22312 @defivar Symtab_and_line pc
22313 Indicates the current program counter address. This attribute is not
22317 @defivar Symtab_and_line line
22318 Indicates the current line number for this object. This
22319 attribute is not writable.
22323 A @code{gdb.Symtab} object has the following attributes:
22326 @defivar Symtab filename
22327 The symbol table's source filename. This attribute is not writable.
22330 @defivar Symtab objfile
22331 The symbol table's backing object file. @xref{Objfiles In Python}.
22332 This attribute is not writable.
22336 The following methods are provided:
22339 @defmethod Symtab fullname
22340 Return the symbol table's source absolute file name.
22344 @node Breakpoints In Python
22345 @subsubsection Manipulating breakpoints using Python
22347 @cindex breakpoints in python
22348 @tindex gdb.Breakpoint
22350 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
22353 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]}
22354 Create a new breakpoint. @var{spec} is a string naming the
22355 location of the breakpoint, or an expression that defines a
22356 watchpoint. The contents can be any location recognized by the
22357 @code{break} command, or in the case of a watchpoint, by the @code{watch}
22358 command. The optional @var{type} denotes the breakpoint to create
22359 from the types defined later in this chapter. This argument can be
22360 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
22361 defaults to @code{BP_BREAKPOINT}. The optional @var{wp_class}
22362 argument defines the class of watchpoint to create, if @var{type} is
22363 defined as @code{BP_WATCHPOINT}. If a watchpoint class is not
22364 provided, it is assumed to be a @var{WP_WRITE} class.
22367 The available watchpoint types represented by constants are defined in the
22372 @findex gdb.WP_READ
22374 Read only watchpoint.
22377 @findex gdb.WP_WRITE
22379 Write only watchpoint.
22382 @findex gdb.WP_ACCESS
22384 Read/Write watchpoint.
22387 @defmethod Breakpoint is_valid
22388 Return @code{True} if this @code{Breakpoint} object is valid,
22389 @code{False} otherwise. A @code{Breakpoint} object can become invalid
22390 if the user deletes the breakpoint. In this case, the object still
22391 exists, but the underlying breakpoint does not. In the cases of
22392 watchpoint scope, the watchpoint remains valid even if execution of the
22393 inferior leaves the scope of that watchpoint.
22396 @defivar Breakpoint enabled
22397 This attribute is @code{True} if the breakpoint is enabled, and
22398 @code{False} otherwise. This attribute is writable.
22401 @defivar Breakpoint silent
22402 This attribute is @code{True} if the breakpoint is silent, and
22403 @code{False} otherwise. This attribute is writable.
22405 Note that a breakpoint can also be silent if it has commands and the
22406 first command is @code{silent}. This is not reported by the
22407 @code{silent} attribute.
22410 @defivar Breakpoint thread
22411 If the breakpoint is thread-specific, this attribute holds the thread
22412 id. If the breakpoint is not thread-specific, this attribute is
22413 @code{None}. This attribute is writable.
22416 @defivar Breakpoint task
22417 If the breakpoint is Ada task-specific, this attribute holds the Ada task
22418 id. If the breakpoint is not task-specific (or the underlying
22419 language is not Ada), this attribute is @code{None}. This attribute
22423 @defivar Breakpoint ignore_count
22424 This attribute holds the ignore count for the breakpoint, an integer.
22425 This attribute is writable.
22428 @defivar Breakpoint number
22429 This attribute holds the breakpoint's number --- the identifier used by
22430 the user to manipulate the breakpoint. This attribute is not writable.
22433 @defivar Breakpoint type
22434 This attribute holds the breakpoint's type --- the identifier used to
22435 determine the actual breakpoint type or use-case. This attribute is not
22439 The available types are represented by constants defined in the @code{gdb}
22443 @findex BP_BREAKPOINT
22444 @findex gdb.BP_BREAKPOINT
22445 @item BP_BREAKPOINT
22446 Normal code breakpoint.
22448 @findex BP_WATCHPOINT
22449 @findex gdb.BP_WATCHPOINT
22450 @item BP_WATCHPOINT
22451 Watchpoint breakpoint.
22453 @findex BP_HARDWARE_WATCHPOINT
22454 @findex gdb.BP_HARDWARE_WATCHPOINT
22455 @item BP_HARDWARE_WATCHPOINT
22456 Hardware assisted watchpoint.
22458 @findex BP_READ_WATCHPOINT
22459 @findex gdb.BP_READ_WATCHPOINT
22460 @item BP_READ_WATCHPOINT
22461 Hardware assisted read watchpoint.
22463 @findex BP_ACCESS_WATCHPOINT
22464 @findex gdb.BP_ACCESS_WATCHPOINT
22465 @item BP_ACCESS_WATCHPOINT
22466 Hardware assisted access watchpoint.
22469 @defivar Breakpoint hit_count
22470 This attribute holds the hit count for the breakpoint, an integer.
22471 This attribute is writable, but currently it can only be set to zero.
22474 @defivar Breakpoint location
22475 This attribute holds the location of the breakpoint, as specified by
22476 the user. It is a string. If the breakpoint does not have a location
22477 (that is, it is a watchpoint) the attribute's value is @code{None}. This
22478 attribute is not writable.
22481 @defivar Breakpoint expression
22482 This attribute holds a breakpoint expression, as specified by
22483 the user. It is a string. If the breakpoint does not have an
22484 expression (the breakpoint is not a watchpoint) the attribute's value
22485 is @code{None}. This attribute is not writable.
22488 @defivar Breakpoint condition
22489 This attribute holds the condition of the breakpoint, as specified by
22490 the user. It is a string. If there is no condition, this attribute's
22491 value is @code{None}. This attribute is writable.
22494 @defivar Breakpoint commands
22495 This attribute holds the commands attached to the breakpoint. If
22496 there are commands, this attribute's value is a string holding all the
22497 commands, separated by newlines. If there are no commands, this
22498 attribute is @code{None}. This attribute is not writable.
22501 @node Lazy Strings In Python
22502 @subsubsection Python representation of lazy strings.
22504 @cindex lazy strings in python
22505 @tindex gdb.LazyString
22507 A @dfn{lazy string} is a string whose contents is not retrieved or
22508 encoded until it is needed.
22510 A @code{gdb.LazyString} is represented in @value{GDBN} as an
22511 @code{address} that points to a region of memory, an @code{encoding}
22512 that will be used to encode that region of memory, and a @code{length}
22513 to delimit the region of memory that represents the string. The
22514 difference between a @code{gdb.LazyString} and a string wrapped within
22515 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
22516 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
22517 retrieved and encoded during printing, while a @code{gdb.Value}
22518 wrapping a string is immediately retrieved and encoded on creation.
22520 A @code{gdb.LazyString} object has the following functions:
22522 @defmethod LazyString value
22523 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
22524 will point to the string in memory, but will lose all the delayed
22525 retrieval, encoding and handling that @value{GDBN} applies to a
22526 @code{gdb.LazyString}.
22529 @defivar LazyString address
22530 This attribute holds the address of the string. This attribute is not
22534 @defivar LazyString length
22535 This attribute holds the length of the string in characters. If the
22536 length is -1, then the string will be fetched and encoded up to the
22537 first null of appropriate width. This attribute is not writable.
22540 @defivar LazyString encoding
22541 This attribute holds the encoding that will be applied to the string
22542 when the string is printed by @value{GDBN}. If the encoding is not
22543 set, or contains an empty string, then @value{GDBN} will select the
22544 most appropriate encoding when the string is printed. This attribute
22548 @defivar LazyString type
22549 This attribute holds the type that is represented by the lazy string's
22550 type. For a lazy string this will always be a pointer type. To
22551 resolve this to the lazy string's character type, use the type's
22552 @code{target} method. @xref{Types In Python}. This attribute is not
22557 @subsection Auto-loading
22558 @cindex auto-loading, Python
22560 When a new object file is read (for example, due to the @code{file}
22561 command, or because the inferior has loaded a shared library),
22562 @value{GDBN} will look for Python support scripts in several ways:
22563 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
22566 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
22567 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
22568 * Which flavor to choose?::
22571 The auto-loading feature is useful for supplying application-specific
22572 debugging commands and scripts.
22574 Auto-loading can be enabled or disabled.
22577 @kindex maint set python auto-load
22578 @item maint set python auto-load [yes|no]
22579 Enable or disable the Python auto-loading feature.
22581 @kindex maint show python auto-load
22582 @item maint show python auto-load
22583 Show whether Python auto-loading is enabled or disabled.
22586 When reading an auto-loaded file, @value{GDBN} sets the
22587 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
22588 function (@pxref{Objfiles In Python}). This can be useful for
22589 registering objfile-specific pretty-printers.
22591 @node objfile-gdb.py file
22592 @subsubsection The @file{@var{objfile}-gdb.py} file
22593 @cindex @file{@var{objfile}-gdb.py}
22595 When a new object file is read, @value{GDBN} looks for
22596 a file named @file{@var{objfile}-gdb.py},
22597 where @var{objfile} is the object file's real name, formed by ensuring
22598 that the file name is absolute, following all symlinks, and resolving
22599 @code{.} and @code{..} components. If this file exists and is
22600 readable, @value{GDBN} will evaluate it as a Python script.
22602 If this file does not exist, and if the parameter
22603 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
22604 then @value{GDBN} will look for @var{real-name} in all of the
22605 directories mentioned in the value of @code{debug-file-directory}.
22607 Finally, if this file does not exist, then @value{GDBN} will look for
22608 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
22609 @var{data-directory} is @value{GDBN}'s data directory (available via
22610 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
22611 is the object file's real name, as described above.
22613 @value{GDBN} does not track which files it has already auto-loaded this way.
22614 @value{GDBN} will load the associated script every time the corresponding
22615 @var{objfile} is opened.
22616 So your @file{-gdb.py} file should be careful to avoid errors if it
22617 is evaluated more than once.
22619 @node .debug_gdb_scripts section
22620 @subsubsection The @code{.debug_gdb_scripts} section
22621 @cindex @code{.debug_gdb_scripts} section
22623 For systems using file formats like ELF and COFF,
22624 when @value{GDBN} loads a new object file
22625 it will look for a special section named @samp{.debug_gdb_scripts}.
22626 If this section exists, its contents is a list of names of scripts to load.
22628 @value{GDBN} will look for each specified script file first in the
22629 current directory and then along the source search path
22630 (@pxref{Source Path, ,Specifying Source Directories}),
22631 except that @file{$cdir} is not searched, since the compilation
22632 directory is not relevant to scripts.
22634 Entries can be placed in section @code{.debug_gdb_scripts} with,
22635 for example, this GCC macro:
22638 /* Note: The "MS" section flags are to remote duplicates. */
22639 #define DEFINE_GDB_SCRIPT(script_name) \
22641 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
22643 .asciz \"" script_name "\"\n\
22649 Then one can reference the macro in a header or source file like this:
22652 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
22655 The script name may include directories if desired.
22657 If the macro is put in a header, any application or library
22658 using this header will get a reference to the specified script.
22660 @node Which flavor to choose?
22661 @subsubsection Which flavor to choose?
22663 Given the multiple ways of auto-loading Python scripts, it might not always
22664 be clear which one to choose. This section provides some guidance.
22666 Benefits of the @file{-gdb.py} way:
22670 Can be used with file formats that don't support multiple sections.
22673 Ease of finding scripts for public libraries.
22675 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
22676 in the source search path.
22677 For publicly installed libraries, e.g., @file{libstdc++}, there typically
22678 isn't a source directory in which to find the script.
22681 Doesn't require source code additions.
22684 Benefits of the @code{.debug_gdb_scripts} way:
22688 Works with static linking.
22690 Scripts for libraries done the @file{-gdb.py} way require an objfile to
22691 trigger their loading. When an application is statically linked the only
22692 objfile available is the executable, and it is cumbersome to attach all the
22693 scripts from all the input libraries to the executable's @file{-gdb.py} script.
22696 Works with classes that are entirely inlined.
22698 Some classes can be entirely inlined, and thus there may not be an associated
22699 shared library to attach a @file{-gdb.py} script to.
22702 Scripts needn't be copied out of the source tree.
22704 In some circumstances, apps can be built out of large collections of internal
22705 libraries, and the build infrastructure necessary to install the
22706 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
22707 cumbersome. It may be easier to specify the scripts in the
22708 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
22709 top of the source tree to the source search path.
22713 @chapter Command Interpreters
22714 @cindex command interpreters
22716 @value{GDBN} supports multiple command interpreters, and some command
22717 infrastructure to allow users or user interface writers to switch
22718 between interpreters or run commands in other interpreters.
22720 @value{GDBN} currently supports two command interpreters, the console
22721 interpreter (sometimes called the command-line interpreter or @sc{cli})
22722 and the machine interface interpreter (or @sc{gdb/mi}). This manual
22723 describes both of these interfaces in great detail.
22725 By default, @value{GDBN} will start with the console interpreter.
22726 However, the user may choose to start @value{GDBN} with another
22727 interpreter by specifying the @option{-i} or @option{--interpreter}
22728 startup options. Defined interpreters include:
22732 @cindex console interpreter
22733 The traditional console or command-line interpreter. This is the most often
22734 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
22735 @value{GDBN} will use this interpreter.
22738 @cindex mi interpreter
22739 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
22740 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
22741 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
22745 @cindex mi2 interpreter
22746 The current @sc{gdb/mi} interface.
22749 @cindex mi1 interpreter
22750 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
22754 @cindex invoke another interpreter
22755 The interpreter being used by @value{GDBN} may not be dynamically
22756 switched at runtime. Although possible, this could lead to a very
22757 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
22758 enters the command "interpreter-set console" in a console view,
22759 @value{GDBN} would switch to using the console interpreter, rendering
22760 the IDE inoperable!
22762 @kindex interpreter-exec
22763 Although you may only choose a single interpreter at startup, you may execute
22764 commands in any interpreter from the current interpreter using the appropriate
22765 command. If you are running the console interpreter, simply use the
22766 @code{interpreter-exec} command:
22769 interpreter-exec mi "-data-list-register-names"
22772 @sc{gdb/mi} has a similar command, although it is only available in versions of
22773 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
22776 @chapter @value{GDBN} Text User Interface
22778 @cindex Text User Interface
22781 * TUI Overview:: TUI overview
22782 * TUI Keys:: TUI key bindings
22783 * TUI Single Key Mode:: TUI single key mode
22784 * TUI Commands:: TUI-specific commands
22785 * TUI Configuration:: TUI configuration variables
22788 The @value{GDBN} Text User Interface (TUI) is a terminal
22789 interface which uses the @code{curses} library to show the source
22790 file, the assembly output, the program registers and @value{GDBN}
22791 commands in separate text windows. The TUI mode is supported only
22792 on platforms where a suitable version of the @code{curses} library
22795 @pindex @value{GDBTUI}
22796 The TUI mode is enabled by default when you invoke @value{GDBN} as
22797 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
22798 You can also switch in and out of TUI mode while @value{GDBN} runs by
22799 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
22800 @xref{TUI Keys, ,TUI Key Bindings}.
22803 @section TUI Overview
22805 In TUI mode, @value{GDBN} can display several text windows:
22809 This window is the @value{GDBN} command window with the @value{GDBN}
22810 prompt and the @value{GDBN} output. The @value{GDBN} input is still
22811 managed using readline.
22814 The source window shows the source file of the program. The current
22815 line and active breakpoints are displayed in this window.
22818 The assembly window shows the disassembly output of the program.
22821 This window shows the processor registers. Registers are highlighted
22822 when their values change.
22825 The source and assembly windows show the current program position
22826 by highlighting the current line and marking it with a @samp{>} marker.
22827 Breakpoints are indicated with two markers. The first marker
22828 indicates the breakpoint type:
22832 Breakpoint which was hit at least once.
22835 Breakpoint which was never hit.
22838 Hardware breakpoint which was hit at least once.
22841 Hardware breakpoint which was never hit.
22844 The second marker indicates whether the breakpoint is enabled or not:
22848 Breakpoint is enabled.
22851 Breakpoint is disabled.
22854 The source, assembly and register windows are updated when the current
22855 thread changes, when the frame changes, or when the program counter
22858 These windows are not all visible at the same time. The command
22859 window is always visible. The others can be arranged in several
22870 source and assembly,
22873 source and registers, or
22876 assembly and registers.
22879 A status line above the command window shows the following information:
22883 Indicates the current @value{GDBN} target.
22884 (@pxref{Targets, ,Specifying a Debugging Target}).
22887 Gives the current process or thread number.
22888 When no process is being debugged, this field is set to @code{No process}.
22891 Gives the current function name for the selected frame.
22892 The name is demangled if demangling is turned on (@pxref{Print Settings}).
22893 When there is no symbol corresponding to the current program counter,
22894 the string @code{??} is displayed.
22897 Indicates the current line number for the selected frame.
22898 When the current line number is not known, the string @code{??} is displayed.
22901 Indicates the current program counter address.
22905 @section TUI Key Bindings
22906 @cindex TUI key bindings
22908 The TUI installs several key bindings in the readline keymaps
22909 (@pxref{Command Line Editing}). The following key bindings
22910 are installed for both TUI mode and the @value{GDBN} standard mode.
22919 Enter or leave the TUI mode. When leaving the TUI mode,
22920 the curses window management stops and @value{GDBN} operates using
22921 its standard mode, writing on the terminal directly. When reentering
22922 the TUI mode, control is given back to the curses windows.
22923 The screen is then refreshed.
22927 Use a TUI layout with only one window. The layout will
22928 either be @samp{source} or @samp{assembly}. When the TUI mode
22929 is not active, it will switch to the TUI mode.
22931 Think of this key binding as the Emacs @kbd{C-x 1} binding.
22935 Use a TUI layout with at least two windows. When the current
22936 layout already has two windows, the next layout with two windows is used.
22937 When a new layout is chosen, one window will always be common to the
22938 previous layout and the new one.
22940 Think of it as the Emacs @kbd{C-x 2} binding.
22944 Change the active window. The TUI associates several key bindings
22945 (like scrolling and arrow keys) with the active window. This command
22946 gives the focus to the next TUI window.
22948 Think of it as the Emacs @kbd{C-x o} binding.
22952 Switch in and out of the TUI SingleKey mode that binds single
22953 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
22956 The following key bindings only work in the TUI mode:
22961 Scroll the active window one page up.
22965 Scroll the active window one page down.
22969 Scroll the active window one line up.
22973 Scroll the active window one line down.
22977 Scroll the active window one column left.
22981 Scroll the active window one column right.
22985 Refresh the screen.
22988 Because the arrow keys scroll the active window in the TUI mode, they
22989 are not available for their normal use by readline unless the command
22990 window has the focus. When another window is active, you must use
22991 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
22992 and @kbd{C-f} to control the command window.
22994 @node TUI Single Key Mode
22995 @section TUI Single Key Mode
22996 @cindex TUI single key mode
22998 The TUI also provides a @dfn{SingleKey} mode, which binds several
22999 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
23000 switch into this mode, where the following key bindings are used:
23003 @kindex c @r{(SingleKey TUI key)}
23007 @kindex d @r{(SingleKey TUI key)}
23011 @kindex f @r{(SingleKey TUI key)}
23015 @kindex n @r{(SingleKey TUI key)}
23019 @kindex q @r{(SingleKey TUI key)}
23021 exit the SingleKey mode.
23023 @kindex r @r{(SingleKey TUI key)}
23027 @kindex s @r{(SingleKey TUI key)}
23031 @kindex u @r{(SingleKey TUI key)}
23035 @kindex v @r{(SingleKey TUI key)}
23039 @kindex w @r{(SingleKey TUI key)}
23044 Other keys temporarily switch to the @value{GDBN} command prompt.
23045 The key that was pressed is inserted in the editing buffer so that
23046 it is possible to type most @value{GDBN} commands without interaction
23047 with the TUI SingleKey mode. Once the command is entered the TUI
23048 SingleKey mode is restored. The only way to permanently leave
23049 this mode is by typing @kbd{q} or @kbd{C-x s}.
23053 @section TUI-specific Commands
23054 @cindex TUI commands
23056 The TUI has specific commands to control the text windows.
23057 These commands are always available, even when @value{GDBN} is not in
23058 the TUI mode. When @value{GDBN} is in the standard mode, most
23059 of these commands will automatically switch to the TUI mode.
23061 Note that if @value{GDBN}'s @code{stdout} is not connected to a
23062 terminal, or @value{GDBN} has been started with the machine interface
23063 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
23064 these commands will fail with an error, because it would not be
23065 possible or desirable to enable curses window management.
23070 List and give the size of all displayed windows.
23074 Display the next layout.
23077 Display the previous layout.
23080 Display the source window only.
23083 Display the assembly window only.
23086 Display the source and assembly window.
23089 Display the register window together with the source or assembly window.
23093 Make the next window active for scrolling.
23096 Make the previous window active for scrolling.
23099 Make the source window active for scrolling.
23102 Make the assembly window active for scrolling.
23105 Make the register window active for scrolling.
23108 Make the command window active for scrolling.
23112 Refresh the screen. This is similar to typing @kbd{C-L}.
23114 @item tui reg float
23116 Show the floating point registers in the register window.
23118 @item tui reg general
23119 Show the general registers in the register window.
23122 Show the next register group. The list of register groups as well as
23123 their order is target specific. The predefined register groups are the
23124 following: @code{general}, @code{float}, @code{system}, @code{vector},
23125 @code{all}, @code{save}, @code{restore}.
23127 @item tui reg system
23128 Show the system registers in the register window.
23132 Update the source window and the current execution point.
23134 @item winheight @var{name} +@var{count}
23135 @itemx winheight @var{name} -@var{count}
23137 Change the height of the window @var{name} by @var{count}
23138 lines. Positive counts increase the height, while negative counts
23141 @item tabset @var{nchars}
23143 Set the width of tab stops to be @var{nchars} characters.
23146 @node TUI Configuration
23147 @section TUI Configuration Variables
23148 @cindex TUI configuration variables
23150 Several configuration variables control the appearance of TUI windows.
23153 @item set tui border-kind @var{kind}
23154 @kindex set tui border-kind
23155 Select the border appearance for the source, assembly and register windows.
23156 The possible values are the following:
23159 Use a space character to draw the border.
23162 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
23165 Use the Alternate Character Set to draw the border. The border is
23166 drawn using character line graphics if the terminal supports them.
23169 @item set tui border-mode @var{mode}
23170 @kindex set tui border-mode
23171 @itemx set tui active-border-mode @var{mode}
23172 @kindex set tui active-border-mode
23173 Select the display attributes for the borders of the inactive windows
23174 or the active window. The @var{mode} can be one of the following:
23177 Use normal attributes to display the border.
23183 Use reverse video mode.
23186 Use half bright mode.
23188 @item half-standout
23189 Use half bright and standout mode.
23192 Use extra bright or bold mode.
23194 @item bold-standout
23195 Use extra bright or bold and standout mode.
23200 @chapter Using @value{GDBN} under @sc{gnu} Emacs
23203 @cindex @sc{gnu} Emacs
23204 A special interface allows you to use @sc{gnu} Emacs to view (and
23205 edit) the source files for the program you are debugging with
23208 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
23209 executable file you want to debug as an argument. This command starts
23210 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
23211 created Emacs buffer.
23212 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
23214 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
23219 All ``terminal'' input and output goes through an Emacs buffer, called
23222 This applies both to @value{GDBN} commands and their output, and to the input
23223 and output done by the program you are debugging.
23225 This is useful because it means that you can copy the text of previous
23226 commands and input them again; you can even use parts of the output
23229 All the facilities of Emacs' Shell mode are available for interacting
23230 with your program. In particular, you can send signals the usual
23231 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
23235 @value{GDBN} displays source code through Emacs.
23237 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
23238 source file for that frame and puts an arrow (@samp{=>}) at the
23239 left margin of the current line. Emacs uses a separate buffer for
23240 source display, and splits the screen to show both your @value{GDBN} session
23243 Explicit @value{GDBN} @code{list} or search commands still produce output as
23244 usual, but you probably have no reason to use them from Emacs.
23247 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
23248 a graphical mode, enabled by default, which provides further buffers
23249 that can control the execution and describe the state of your program.
23250 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
23252 If you specify an absolute file name when prompted for the @kbd{M-x
23253 gdb} argument, then Emacs sets your current working directory to where
23254 your program resides. If you only specify the file name, then Emacs
23255 sets your current working directory to to the directory associated
23256 with the previous buffer. In this case, @value{GDBN} may find your
23257 program by searching your environment's @code{PATH} variable, but on
23258 some operating systems it might not find the source. So, although the
23259 @value{GDBN} input and output session proceeds normally, the auxiliary
23260 buffer does not display the current source and line of execution.
23262 The initial working directory of @value{GDBN} is printed on the top
23263 line of the GUD buffer and this serves as a default for the commands
23264 that specify files for @value{GDBN} to operate on. @xref{Files,
23265 ,Commands to Specify Files}.
23267 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
23268 need to call @value{GDBN} by a different name (for example, if you
23269 keep several configurations around, with different names) you can
23270 customize the Emacs variable @code{gud-gdb-command-name} to run the
23273 In the GUD buffer, you can use these special Emacs commands in
23274 addition to the standard Shell mode commands:
23278 Describe the features of Emacs' GUD Mode.
23281 Execute to another source line, like the @value{GDBN} @code{step} command; also
23282 update the display window to show the current file and location.
23285 Execute to next source line in this function, skipping all function
23286 calls, like the @value{GDBN} @code{next} command. Then update the display window
23287 to show the current file and location.
23290 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
23291 display window accordingly.
23294 Execute until exit from the selected stack frame, like the @value{GDBN}
23295 @code{finish} command.
23298 Continue execution of your program, like the @value{GDBN} @code{continue}
23302 Go up the number of frames indicated by the numeric argument
23303 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
23304 like the @value{GDBN} @code{up} command.
23307 Go down the number of frames indicated by the numeric argument, like the
23308 @value{GDBN} @code{down} command.
23311 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
23312 tells @value{GDBN} to set a breakpoint on the source line point is on.
23314 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
23315 separate frame which shows a backtrace when the GUD buffer is current.
23316 Move point to any frame in the stack and type @key{RET} to make it
23317 become the current frame and display the associated source in the
23318 source buffer. Alternatively, click @kbd{Mouse-2} to make the
23319 selected frame become the current one. In graphical mode, the
23320 speedbar displays watch expressions.
23322 If you accidentally delete the source-display buffer, an easy way to get
23323 it back is to type the command @code{f} in the @value{GDBN} buffer, to
23324 request a frame display; when you run under Emacs, this recreates
23325 the source buffer if necessary to show you the context of the current
23328 The source files displayed in Emacs are in ordinary Emacs buffers
23329 which are visiting the source files in the usual way. You can edit
23330 the files with these buffers if you wish; but keep in mind that @value{GDBN}
23331 communicates with Emacs in terms of line numbers. If you add or
23332 delete lines from the text, the line numbers that @value{GDBN} knows cease
23333 to correspond properly with the code.
23335 A more detailed description of Emacs' interaction with @value{GDBN} is
23336 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
23339 @c The following dropped because Epoch is nonstandard. Reactivate
23340 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
23342 @kindex Emacs Epoch environment
23346 Version 18 of @sc{gnu} Emacs has a built-in window system
23347 called the @code{epoch}
23348 environment. Users of this environment can use a new command,
23349 @code{inspect} which performs identically to @code{print} except that
23350 each value is printed in its own window.
23355 @chapter The @sc{gdb/mi} Interface
23357 @unnumberedsec Function and Purpose
23359 @cindex @sc{gdb/mi}, its purpose
23360 @sc{gdb/mi} is a line based machine oriented text interface to
23361 @value{GDBN} and is activated by specifying using the
23362 @option{--interpreter} command line option (@pxref{Mode Options}). It
23363 is specifically intended to support the development of systems which
23364 use the debugger as just one small component of a larger system.
23366 This chapter is a specification of the @sc{gdb/mi} interface. It is written
23367 in the form of a reference manual.
23369 Note that @sc{gdb/mi} is still under construction, so some of the
23370 features described below are incomplete and subject to change
23371 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
23373 @unnumberedsec Notation and Terminology
23375 @cindex notational conventions, for @sc{gdb/mi}
23376 This chapter uses the following notation:
23380 @code{|} separates two alternatives.
23383 @code{[ @var{something} ]} indicates that @var{something} is optional:
23384 it may or may not be given.
23387 @code{( @var{group} )*} means that @var{group} inside the parentheses
23388 may repeat zero or more times.
23391 @code{( @var{group} )+} means that @var{group} inside the parentheses
23392 may repeat one or more times.
23395 @code{"@var{string}"} means a literal @var{string}.
23399 @heading Dependencies
23403 * GDB/MI General Design::
23404 * GDB/MI Command Syntax::
23405 * GDB/MI Compatibility with CLI::
23406 * GDB/MI Development and Front Ends::
23407 * GDB/MI Output Records::
23408 * GDB/MI Simple Examples::
23409 * GDB/MI Command Description Format::
23410 * GDB/MI Breakpoint Commands::
23411 * GDB/MI Program Context::
23412 * GDB/MI Thread Commands::
23413 * GDB/MI Program Execution::
23414 * GDB/MI Stack Manipulation::
23415 * GDB/MI Variable Objects::
23416 * GDB/MI Data Manipulation::
23417 * GDB/MI Tracepoint Commands::
23418 * GDB/MI Symbol Query::
23419 * GDB/MI File Commands::
23421 * GDB/MI Kod Commands::
23422 * GDB/MI Memory Overlay Commands::
23423 * GDB/MI Signal Handling Commands::
23425 * GDB/MI Target Manipulation::
23426 * GDB/MI File Transfer Commands::
23427 * GDB/MI Miscellaneous Commands::
23430 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23431 @node GDB/MI General Design
23432 @section @sc{gdb/mi} General Design
23433 @cindex GDB/MI General Design
23435 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
23436 parts---commands sent to @value{GDBN}, responses to those commands
23437 and notifications. Each command results in exactly one response,
23438 indicating either successful completion of the command, or an error.
23439 For the commands that do not resume the target, the response contains the
23440 requested information. For the commands that resume the target, the
23441 response only indicates whether the target was successfully resumed.
23442 Notifications is the mechanism for reporting changes in the state of the
23443 target, or in @value{GDBN} state, that cannot conveniently be associated with
23444 a command and reported as part of that command response.
23446 The important examples of notifications are:
23450 Exec notifications. These are used to report changes in
23451 target state---when a target is resumed, or stopped. It would not
23452 be feasible to include this information in response of resuming
23453 commands, because one resume commands can result in multiple events in
23454 different threads. Also, quite some time may pass before any event
23455 happens in the target, while a frontend needs to know whether the resuming
23456 command itself was successfully executed.
23459 Console output, and status notifications. Console output
23460 notifications are used to report output of CLI commands, as well as
23461 diagnostics for other commands. Status notifications are used to
23462 report the progress of a long-running operation. Naturally, including
23463 this information in command response would mean no output is produced
23464 until the command is finished, which is undesirable.
23467 General notifications. Commands may have various side effects on
23468 the @value{GDBN} or target state beyond their official purpose. For example,
23469 a command may change the selected thread. Although such changes can
23470 be included in command response, using notification allows for more
23471 orthogonal frontend design.
23475 There's no guarantee that whenever an MI command reports an error,
23476 @value{GDBN} or the target are in any specific state, and especially,
23477 the state is not reverted to the state before the MI command was
23478 processed. Therefore, whenever an MI command results in an error,
23479 we recommend that the frontend refreshes all the information shown in
23480 the user interface.
23484 * Context management::
23485 * Asynchronous and non-stop modes::
23489 @node Context management
23490 @subsection Context management
23492 In most cases when @value{GDBN} accesses the target, this access is
23493 done in context of a specific thread and frame (@pxref{Frames}).
23494 Often, even when accessing global data, the target requires that a thread
23495 be specified. The CLI interface maintains the selected thread and frame,
23496 and supplies them to target on each command. This is convenient,
23497 because a command line user would not want to specify that information
23498 explicitly on each command, and because user interacts with
23499 @value{GDBN} via a single terminal, so no confusion is possible as
23500 to what thread and frame are the current ones.
23502 In the case of MI, the concept of selected thread and frame is less
23503 useful. First, a frontend can easily remember this information
23504 itself. Second, a graphical frontend can have more than one window,
23505 each one used for debugging a different thread, and the frontend might
23506 want to access additional threads for internal purposes. This
23507 increases the risk that by relying on implicitly selected thread, the
23508 frontend may be operating on a wrong one. Therefore, each MI command
23509 should explicitly specify which thread and frame to operate on. To
23510 make it possible, each MI command accepts the @samp{--thread} and
23511 @samp{--frame} options, the value to each is @value{GDBN} identifier
23512 for thread and frame to operate on.
23514 Usually, each top-level window in a frontend allows the user to select
23515 a thread and a frame, and remembers the user selection for further
23516 operations. However, in some cases @value{GDBN} may suggest that the
23517 current thread be changed. For example, when stopping on a breakpoint
23518 it is reasonable to switch to the thread where breakpoint is hit. For
23519 another example, if the user issues the CLI @samp{thread} command via
23520 the frontend, it is desirable to change the frontend's selected thread to the
23521 one specified by user. @value{GDBN} communicates the suggestion to
23522 change current thread using the @samp{=thread-selected} notification.
23523 No such notification is available for the selected frame at the moment.
23525 Note that historically, MI shares the selected thread with CLI, so
23526 frontends used the @code{-thread-select} to execute commands in the
23527 right context. However, getting this to work right is cumbersome. The
23528 simplest way is for frontend to emit @code{-thread-select} command
23529 before every command. This doubles the number of commands that need
23530 to be sent. The alternative approach is to suppress @code{-thread-select}
23531 if the selected thread in @value{GDBN} is supposed to be identical to the
23532 thread the frontend wants to operate on. However, getting this
23533 optimization right can be tricky. In particular, if the frontend
23534 sends several commands to @value{GDBN}, and one of the commands changes the
23535 selected thread, then the behaviour of subsequent commands will
23536 change. So, a frontend should either wait for response from such
23537 problematic commands, or explicitly add @code{-thread-select} for
23538 all subsequent commands. No frontend is known to do this exactly
23539 right, so it is suggested to just always pass the @samp{--thread} and
23540 @samp{--frame} options.
23542 @node Asynchronous and non-stop modes
23543 @subsection Asynchronous command execution and non-stop mode
23545 On some targets, @value{GDBN} is capable of processing MI commands
23546 even while the target is running. This is called @dfn{asynchronous
23547 command execution} (@pxref{Background Execution}). The frontend may
23548 specify a preferrence for asynchronous execution using the
23549 @code{-gdb-set target-async 1} command, which should be emitted before
23550 either running the executable or attaching to the target. After the
23551 frontend has started the executable or attached to the target, it can
23552 find if asynchronous execution is enabled using the
23553 @code{-list-target-features} command.
23555 Even if @value{GDBN} can accept a command while target is running,
23556 many commands that access the target do not work when the target is
23557 running. Therefore, asynchronous command execution is most useful
23558 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
23559 it is possible to examine the state of one thread, while other threads
23562 When a given thread is running, MI commands that try to access the
23563 target in the context of that thread may not work, or may work only on
23564 some targets. In particular, commands that try to operate on thread's
23565 stack will not work, on any target. Commands that read memory, or
23566 modify breakpoints, may work or not work, depending on the target. Note
23567 that even commands that operate on global state, such as @code{print},
23568 @code{set}, and breakpoint commands, still access the target in the
23569 context of a specific thread, so frontend should try to find a
23570 stopped thread and perform the operation on that thread (using the
23571 @samp{--thread} option).
23573 Which commands will work in the context of a running thread is
23574 highly target dependent. However, the two commands
23575 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
23576 to find the state of a thread, will always work.
23578 @node Thread groups
23579 @subsection Thread groups
23580 @value{GDBN} may be used to debug several processes at the same time.
23581 On some platfroms, @value{GDBN} may support debugging of several
23582 hardware systems, each one having several cores with several different
23583 processes running on each core. This section describes the MI
23584 mechanism to support such debugging scenarios.
23586 The key observation is that regardless of the structure of the
23587 target, MI can have a global list of threads, because most commands that
23588 accept the @samp{--thread} option do not need to know what process that
23589 thread belongs to. Therefore, it is not necessary to introduce
23590 neither additional @samp{--process} option, nor an notion of the
23591 current process in the MI interface. The only strictly new feature
23592 that is required is the ability to find how the threads are grouped
23595 To allow the user to discover such grouping, and to support arbitrary
23596 hierarchy of machines/cores/processes, MI introduces the concept of a
23597 @dfn{thread group}. Thread group is a collection of threads and other
23598 thread groups. A thread group always has a string identifier, a type,
23599 and may have additional attributes specific to the type. A new
23600 command, @code{-list-thread-groups}, returns the list of top-level
23601 thread groups, which correspond to processes that @value{GDBN} is
23602 debugging at the moment. By passing an identifier of a thread group
23603 to the @code{-list-thread-groups} command, it is possible to obtain
23604 the members of specific thread group.
23606 To allow the user to easily discover processes, and other objects, he
23607 wishes to debug, a concept of @dfn{available thread group} is
23608 introduced. Available thread group is an thread group that
23609 @value{GDBN} is not debugging, but that can be attached to, using the
23610 @code{-target-attach} command. The list of available top-level thread
23611 groups can be obtained using @samp{-list-thread-groups --available}.
23612 In general, the content of a thread group may be only retrieved only
23613 after attaching to that thread group.
23615 Thread groups are related to inferiors (@pxref{Inferiors and
23616 Programs}). Each inferior corresponds to a thread group of a special
23617 type @samp{process}, and some additional operations are permitted on
23618 such thread groups.
23620 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23621 @node GDB/MI Command Syntax
23622 @section @sc{gdb/mi} Command Syntax
23625 * GDB/MI Input Syntax::
23626 * GDB/MI Output Syntax::
23629 @node GDB/MI Input Syntax
23630 @subsection @sc{gdb/mi} Input Syntax
23632 @cindex input syntax for @sc{gdb/mi}
23633 @cindex @sc{gdb/mi}, input syntax
23635 @item @var{command} @expansion{}
23636 @code{@var{cli-command} | @var{mi-command}}
23638 @item @var{cli-command} @expansion{}
23639 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
23640 @var{cli-command} is any existing @value{GDBN} CLI command.
23642 @item @var{mi-command} @expansion{}
23643 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
23644 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
23646 @item @var{token} @expansion{}
23647 "any sequence of digits"
23649 @item @var{option} @expansion{}
23650 @code{"-" @var{parameter} [ " " @var{parameter} ]}
23652 @item @var{parameter} @expansion{}
23653 @code{@var{non-blank-sequence} | @var{c-string}}
23655 @item @var{operation} @expansion{}
23656 @emph{any of the operations described in this chapter}
23658 @item @var{non-blank-sequence} @expansion{}
23659 @emph{anything, provided it doesn't contain special characters such as
23660 "-", @var{nl}, """ and of course " "}
23662 @item @var{c-string} @expansion{}
23663 @code{""" @var{seven-bit-iso-c-string-content} """}
23665 @item @var{nl} @expansion{}
23674 The CLI commands are still handled by the @sc{mi} interpreter; their
23675 output is described below.
23678 The @code{@var{token}}, when present, is passed back when the command
23682 Some @sc{mi} commands accept optional arguments as part of the parameter
23683 list. Each option is identified by a leading @samp{-} (dash) and may be
23684 followed by an optional argument parameter. Options occur first in the
23685 parameter list and can be delimited from normal parameters using
23686 @samp{--} (this is useful when some parameters begin with a dash).
23693 We want easy access to the existing CLI syntax (for debugging).
23696 We want it to be easy to spot a @sc{mi} operation.
23699 @node GDB/MI Output Syntax
23700 @subsection @sc{gdb/mi} Output Syntax
23702 @cindex output syntax of @sc{gdb/mi}
23703 @cindex @sc{gdb/mi}, output syntax
23704 The output from @sc{gdb/mi} consists of zero or more out-of-band records
23705 followed, optionally, by a single result record. This result record
23706 is for the most recent command. The sequence of output records is
23707 terminated by @samp{(gdb)}.
23709 If an input command was prefixed with a @code{@var{token}} then the
23710 corresponding output for that command will also be prefixed by that same
23714 @item @var{output} @expansion{}
23715 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
23717 @item @var{result-record} @expansion{}
23718 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
23720 @item @var{out-of-band-record} @expansion{}
23721 @code{@var{async-record} | @var{stream-record}}
23723 @item @var{async-record} @expansion{}
23724 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
23726 @item @var{exec-async-output} @expansion{}
23727 @code{[ @var{token} ] "*" @var{async-output}}
23729 @item @var{status-async-output} @expansion{}
23730 @code{[ @var{token} ] "+" @var{async-output}}
23732 @item @var{notify-async-output} @expansion{}
23733 @code{[ @var{token} ] "=" @var{async-output}}
23735 @item @var{async-output} @expansion{}
23736 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
23738 @item @var{result-class} @expansion{}
23739 @code{"done" | "running" | "connected" | "error" | "exit"}
23741 @item @var{async-class} @expansion{}
23742 @code{"stopped" | @var{others}} (where @var{others} will be added
23743 depending on the needs---this is still in development).
23745 @item @var{result} @expansion{}
23746 @code{ @var{variable} "=" @var{value}}
23748 @item @var{variable} @expansion{}
23749 @code{ @var{string} }
23751 @item @var{value} @expansion{}
23752 @code{ @var{const} | @var{tuple} | @var{list} }
23754 @item @var{const} @expansion{}
23755 @code{@var{c-string}}
23757 @item @var{tuple} @expansion{}
23758 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
23760 @item @var{list} @expansion{}
23761 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
23762 @var{result} ( "," @var{result} )* "]" }
23764 @item @var{stream-record} @expansion{}
23765 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
23767 @item @var{console-stream-output} @expansion{}
23768 @code{"~" @var{c-string}}
23770 @item @var{target-stream-output} @expansion{}
23771 @code{"@@" @var{c-string}}
23773 @item @var{log-stream-output} @expansion{}
23774 @code{"&" @var{c-string}}
23776 @item @var{nl} @expansion{}
23779 @item @var{token} @expansion{}
23780 @emph{any sequence of digits}.
23788 All output sequences end in a single line containing a period.
23791 The @code{@var{token}} is from the corresponding request. Note that
23792 for all async output, while the token is allowed by the grammar and
23793 may be output by future versions of @value{GDBN} for select async
23794 output messages, it is generally omitted. Frontends should treat
23795 all async output as reporting general changes in the state of the
23796 target and there should be no need to associate async output to any
23800 @cindex status output in @sc{gdb/mi}
23801 @var{status-async-output} contains on-going status information about the
23802 progress of a slow operation. It can be discarded. All status output is
23803 prefixed by @samp{+}.
23806 @cindex async output in @sc{gdb/mi}
23807 @var{exec-async-output} contains asynchronous state change on the target
23808 (stopped, started, disappeared). All async output is prefixed by
23812 @cindex notify output in @sc{gdb/mi}
23813 @var{notify-async-output} contains supplementary information that the
23814 client should handle (e.g., a new breakpoint information). All notify
23815 output is prefixed by @samp{=}.
23818 @cindex console output in @sc{gdb/mi}
23819 @var{console-stream-output} is output that should be displayed as is in the
23820 console. It is the textual response to a CLI command. All the console
23821 output is prefixed by @samp{~}.
23824 @cindex target output in @sc{gdb/mi}
23825 @var{target-stream-output} is the output produced by the target program.
23826 All the target output is prefixed by @samp{@@}.
23829 @cindex log output in @sc{gdb/mi}
23830 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
23831 instance messages that should be displayed as part of an error log. All
23832 the log output is prefixed by @samp{&}.
23835 @cindex list output in @sc{gdb/mi}
23836 New @sc{gdb/mi} commands should only output @var{lists} containing
23842 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
23843 details about the various output records.
23845 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23846 @node GDB/MI Compatibility with CLI
23847 @section @sc{gdb/mi} Compatibility with CLI
23849 @cindex compatibility, @sc{gdb/mi} and CLI
23850 @cindex @sc{gdb/mi}, compatibility with CLI
23852 For the developers convenience CLI commands can be entered directly,
23853 but there may be some unexpected behaviour. For example, commands
23854 that query the user will behave as if the user replied yes, breakpoint
23855 command lists are not executed and some CLI commands, such as
23856 @code{if}, @code{when} and @code{define}, prompt for further input with
23857 @samp{>}, which is not valid MI output.
23859 This feature may be removed at some stage in the future and it is
23860 recommended that front ends use the @code{-interpreter-exec} command
23861 (@pxref{-interpreter-exec}).
23863 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23864 @node GDB/MI Development and Front Ends
23865 @section @sc{gdb/mi} Development and Front Ends
23866 @cindex @sc{gdb/mi} development
23868 The application which takes the MI output and presents the state of the
23869 program being debugged to the user is called a @dfn{front end}.
23871 Although @sc{gdb/mi} is still incomplete, it is currently being used
23872 by a variety of front ends to @value{GDBN}. This makes it difficult
23873 to introduce new functionality without breaking existing usage. This
23874 section tries to minimize the problems by describing how the protocol
23877 Some changes in MI need not break a carefully designed front end, and
23878 for these the MI version will remain unchanged. The following is a
23879 list of changes that may occur within one level, so front ends should
23880 parse MI output in a way that can handle them:
23884 New MI commands may be added.
23887 New fields may be added to the output of any MI command.
23890 The range of values for fields with specified values, e.g.,
23891 @code{in_scope} (@pxref{-var-update}) may be extended.
23893 @c The format of field's content e.g type prefix, may change so parse it
23894 @c at your own risk. Yes, in general?
23896 @c The order of fields may change? Shouldn't really matter but it might
23897 @c resolve inconsistencies.
23900 If the changes are likely to break front ends, the MI version level
23901 will be increased by one. This will allow the front end to parse the
23902 output according to the MI version. Apart from mi0, new versions of
23903 @value{GDBN} will not support old versions of MI and it will be the
23904 responsibility of the front end to work with the new one.
23906 @c Starting with mi3, add a new command -mi-version that prints the MI
23909 The best way to avoid unexpected changes in MI that might break your front
23910 end is to make your project known to @value{GDBN} developers and
23911 follow development on @email{gdb@@sourceware.org} and
23912 @email{gdb-patches@@sourceware.org}.
23913 @cindex mailing lists
23915 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23916 @node GDB/MI Output Records
23917 @section @sc{gdb/mi} Output Records
23920 * GDB/MI Result Records::
23921 * GDB/MI Stream Records::
23922 * GDB/MI Async Records::
23923 * GDB/MI Frame Information::
23924 * GDB/MI Thread Information::
23927 @node GDB/MI Result Records
23928 @subsection @sc{gdb/mi} Result Records
23930 @cindex result records in @sc{gdb/mi}
23931 @cindex @sc{gdb/mi}, result records
23932 In addition to a number of out-of-band notifications, the response to a
23933 @sc{gdb/mi} command includes one of the following result indications:
23937 @item "^done" [ "," @var{results} ]
23938 The synchronous operation was successful, @code{@var{results}} are the return
23943 This result record is equivalent to @samp{^done}. Historically, it
23944 was output instead of @samp{^done} if the command has resumed the
23945 target. This behaviour is maintained for backward compatibility, but
23946 all frontends should treat @samp{^done} and @samp{^running}
23947 identically and rely on the @samp{*running} output record to determine
23948 which threads are resumed.
23952 @value{GDBN} has connected to a remote target.
23954 @item "^error" "," @var{c-string}
23956 The operation failed. The @code{@var{c-string}} contains the corresponding
23961 @value{GDBN} has terminated.
23965 @node GDB/MI Stream Records
23966 @subsection @sc{gdb/mi} Stream Records
23968 @cindex @sc{gdb/mi}, stream records
23969 @cindex stream records in @sc{gdb/mi}
23970 @value{GDBN} internally maintains a number of output streams: the console, the
23971 target, and the log. The output intended for each of these streams is
23972 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
23974 Each stream record begins with a unique @dfn{prefix character} which
23975 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
23976 Syntax}). In addition to the prefix, each stream record contains a
23977 @code{@var{string-output}}. This is either raw text (with an implicit new
23978 line) or a quoted C string (which does not contain an implicit newline).
23981 @item "~" @var{string-output}
23982 The console output stream contains text that should be displayed in the
23983 CLI console window. It contains the textual responses to CLI commands.
23985 @item "@@" @var{string-output}
23986 The target output stream contains any textual output from the running
23987 target. This is only present when GDB's event loop is truly
23988 asynchronous, which is currently only the case for remote targets.
23990 @item "&" @var{string-output}
23991 The log stream contains debugging messages being produced by @value{GDBN}'s
23995 @node GDB/MI Async Records
23996 @subsection @sc{gdb/mi} Async Records
23998 @cindex async records in @sc{gdb/mi}
23999 @cindex @sc{gdb/mi}, async records
24000 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
24001 additional changes that have occurred. Those changes can either be a
24002 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
24003 target activity (e.g., target stopped).
24005 The following is the list of possible async records:
24009 @item *running,thread-id="@var{thread}"
24010 The target is now running. The @var{thread} field tells which
24011 specific thread is now running, and can be @samp{all} if all threads
24012 are running. The frontend should assume that no interaction with a
24013 running thread is possible after this notification is produced.
24014 The frontend should not assume that this notification is output
24015 only once for any command. @value{GDBN} may emit this notification
24016 several times, either for different threads, because it cannot resume
24017 all threads together, or even for a single thread, if the thread must
24018 be stepped though some code before letting it run freely.
24020 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
24021 The target has stopped. The @var{reason} field can have one of the
24025 @item breakpoint-hit
24026 A breakpoint was reached.
24027 @item watchpoint-trigger
24028 A watchpoint was triggered.
24029 @item read-watchpoint-trigger
24030 A read watchpoint was triggered.
24031 @item access-watchpoint-trigger
24032 An access watchpoint was triggered.
24033 @item function-finished
24034 An -exec-finish or similar CLI command was accomplished.
24035 @item location-reached
24036 An -exec-until or similar CLI command was accomplished.
24037 @item watchpoint-scope
24038 A watchpoint has gone out of scope.
24039 @item end-stepping-range
24040 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
24041 similar CLI command was accomplished.
24042 @item exited-signalled
24043 The inferior exited because of a signal.
24045 The inferior exited.
24046 @item exited-normally
24047 The inferior exited normally.
24048 @item signal-received
24049 A signal was received by the inferior.
24052 The @var{id} field identifies the thread that directly caused the stop
24053 -- for example by hitting a breakpoint. Depending on whether all-stop
24054 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
24055 stop all threads, or only the thread that directly triggered the stop.
24056 If all threads are stopped, the @var{stopped} field will have the
24057 value of @code{"all"}. Otherwise, the value of the @var{stopped}
24058 field will be a list of thread identifiers. Presently, this list will
24059 always include a single thread, but frontend should be prepared to see
24060 several threads in the list. The @var{core} field reports the
24061 processor core on which the stop event has happened. This field may be absent
24062 if such information is not available.
24064 @item =thread-group-added,id="@var{id}"
24065 @itemx =thread-group-removed,id="@var{id}"
24066 A thread group was either added or removed. The @var{id} field
24067 contains the @value{GDBN} identifier of the thread group. When a thread
24068 group is added, it generally might not be associated with a running
24069 process. When a thread group is removed, its id becomes invalid and
24070 cannot be used in any way.
24072 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
24073 A thread group became associated with a running program,
24074 either because the program was just started or the thread group
24075 was attached to a program. The @var{id} field contains the
24076 @value{GDBN} identifier of the thread group. The @var{pid} field
24077 contains process identifier, specific to the operating system.
24079 @itemx =thread-group-exited,id="@var{id}"
24080 A thread group is no longer associated with a running program,
24081 either because the program has exited, or because it was detached
24082 from. The @var{id} field contains the @value{GDBN} identifier of the
24085 @item =thread-created,id="@var{id}",group-id="@var{gid}"
24086 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
24087 A thread either was created, or has exited. The @var{id} field
24088 contains the @value{GDBN} identifier of the thread. The @var{gid}
24089 field identifies the thread group this thread belongs to.
24091 @item =thread-selected,id="@var{id}"
24092 Informs that the selected thread was changed as result of the last
24093 command. This notification is not emitted as result of @code{-thread-select}
24094 command but is emitted whenever an MI command that is not documented
24095 to change the selected thread actually changes it. In particular,
24096 invoking, directly or indirectly (via user-defined command), the CLI
24097 @code{thread} command, will generate this notification.
24099 We suggest that in response to this notification, front ends
24100 highlight the selected thread and cause subsequent commands to apply to
24103 @item =library-loaded,...
24104 Reports that a new library file was loaded by the program. This
24105 notification has 4 fields---@var{id}, @var{target-name},
24106 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
24107 opaque identifier of the library. For remote debugging case,
24108 @var{target-name} and @var{host-name} fields give the name of the
24109 library file on the target, and on the host respectively. For native
24110 debugging, both those fields have the same value. The
24111 @var{symbols-loaded} field reports if the debug symbols for this
24112 library are loaded. The @var{thread-group} field, if present,
24113 specifies the id of the thread group in whose context the library was loaded.
24114 If the field is absent, it means the library was loaded in the context
24115 of all present thread groups.
24117 @item =library-unloaded,...
24118 Reports that a library was unloaded by the program. This notification
24119 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
24120 the same meaning as for the @code{=library-loaded} notification.
24121 The @var{thread-group} field, if present, specifies the id of the
24122 thread group in whose context the library was unloaded. If the field is
24123 absent, it means the library was unloaded in the context of all present
24128 @node GDB/MI Frame Information
24129 @subsection @sc{gdb/mi} Frame Information
24131 Response from many MI commands includes an information about stack
24132 frame. This information is a tuple that may have the following
24137 The level of the stack frame. The innermost frame has the level of
24138 zero. This field is always present.
24141 The name of the function corresponding to the frame. This field may
24142 be absent if @value{GDBN} is unable to determine the function name.
24145 The code address for the frame. This field is always present.
24148 The name of the source files that correspond to the frame's code
24149 address. This field may be absent.
24152 The source line corresponding to the frames' code address. This field
24156 The name of the binary file (either executable or shared library) the
24157 corresponds to the frame's code address. This field may be absent.
24161 @node GDB/MI Thread Information
24162 @subsection @sc{gdb/mi} Thread Information
24164 Whenever @value{GDBN} has to report an information about a thread, it
24165 uses a tuple with the following fields:
24169 The numeric id assigned to the thread by @value{GDBN}. This field is
24173 Target-specific string identifying the thread. This field is always present.
24176 Additional information about the thread provided by the target.
24177 It is supposed to be human-readable and not interpreted by the
24178 frontend. This field is optional.
24181 Either @samp{stopped} or @samp{running}, depending on whether the
24182 thread is presently running. This field is always present.
24185 The value of this field is an integer number of the processor core the
24186 thread was last seen on. This field is optional.
24190 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24191 @node GDB/MI Simple Examples
24192 @section Simple Examples of @sc{gdb/mi} Interaction
24193 @cindex @sc{gdb/mi}, simple examples
24195 This subsection presents several simple examples of interaction using
24196 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
24197 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
24198 the output received from @sc{gdb/mi}.
24200 Note the line breaks shown in the examples are here only for
24201 readability, they don't appear in the real output.
24203 @subheading Setting a Breakpoint
24205 Setting a breakpoint generates synchronous output which contains detailed
24206 information of the breakpoint.
24209 -> -break-insert main
24210 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24211 enabled="y",addr="0x08048564",func="main",file="myprog.c",
24212 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
24216 @subheading Program Execution
24218 Program execution generates asynchronous records and MI gives the
24219 reason that execution stopped.
24225 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24226 frame=@{addr="0x08048564",func="main",
24227 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
24228 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
24233 <- *stopped,reason="exited-normally"
24237 @subheading Quitting @value{GDBN}
24239 Quitting @value{GDBN} just prints the result class @samp{^exit}.
24247 Please note that @samp{^exit} is printed immediately, but it might
24248 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
24249 performs necessary cleanups, including killing programs being debugged
24250 or disconnecting from debug hardware, so the frontend should wait till
24251 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
24252 fails to exit in reasonable time.
24254 @subheading A Bad Command
24256 Here's what happens if you pass a non-existent command:
24260 <- ^error,msg="Undefined MI command: rubbish"
24265 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24266 @node GDB/MI Command Description Format
24267 @section @sc{gdb/mi} Command Description Format
24269 The remaining sections describe blocks of commands. Each block of
24270 commands is laid out in a fashion similar to this section.
24272 @subheading Motivation
24274 The motivation for this collection of commands.
24276 @subheading Introduction
24278 A brief introduction to this collection of commands as a whole.
24280 @subheading Commands
24282 For each command in the block, the following is described:
24284 @subsubheading Synopsis
24287 -command @var{args}@dots{}
24290 @subsubheading Result
24292 @subsubheading @value{GDBN} Command
24294 The corresponding @value{GDBN} CLI command(s), if any.
24296 @subsubheading Example
24298 Example(s) formatted for readability. Some of the described commands have
24299 not been implemented yet and these are labeled N.A.@: (not available).
24302 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24303 @node GDB/MI Breakpoint Commands
24304 @section @sc{gdb/mi} Breakpoint Commands
24306 @cindex breakpoint commands for @sc{gdb/mi}
24307 @cindex @sc{gdb/mi}, breakpoint commands
24308 This section documents @sc{gdb/mi} commands for manipulating
24311 @subheading The @code{-break-after} Command
24312 @findex -break-after
24314 @subsubheading Synopsis
24317 -break-after @var{number} @var{count}
24320 The breakpoint number @var{number} is not in effect until it has been
24321 hit @var{count} times. To see how this is reflected in the output of
24322 the @samp{-break-list} command, see the description of the
24323 @samp{-break-list} command below.
24325 @subsubheading @value{GDBN} Command
24327 The corresponding @value{GDBN} command is @samp{ignore}.
24329 @subsubheading Example
24334 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24335 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24336 fullname="/home/foo/hello.c",line="5",times="0"@}
24343 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24344 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24345 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24346 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24347 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24348 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24349 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24350 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24351 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24352 line="5",times="0",ignore="3"@}]@}
24357 @subheading The @code{-break-catch} Command
24358 @findex -break-catch
24361 @subheading The @code{-break-commands} Command
24362 @findex -break-commands
24364 @subsubheading Synopsis
24367 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
24370 Specifies the CLI commands that should be executed when breakpoint
24371 @var{number} is hit. The parameters @var{command1} to @var{commandN}
24372 are the commands. If no command is specified, any previously-set
24373 commands are cleared. @xref{Break Commands}. Typical use of this
24374 functionality is tracing a program, that is, printing of values of
24375 some variables whenever breakpoint is hit and then continuing.
24377 @subsubheading @value{GDBN} Command
24379 The corresponding @value{GDBN} command is @samp{commands}.
24381 @subsubheading Example
24386 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24387 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24388 fullname="/home/foo/hello.c",line="5",times="0"@}
24390 -break-commands 1 "print v" "continue"
24395 @subheading The @code{-break-condition} Command
24396 @findex -break-condition
24398 @subsubheading Synopsis
24401 -break-condition @var{number} @var{expr}
24404 Breakpoint @var{number} will stop the program only if the condition in
24405 @var{expr} is true. The condition becomes part of the
24406 @samp{-break-list} output (see the description of the @samp{-break-list}
24409 @subsubheading @value{GDBN} Command
24411 The corresponding @value{GDBN} command is @samp{condition}.
24413 @subsubheading Example
24417 -break-condition 1 1
24421 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24422 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24423 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24424 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24425 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24426 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24427 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24428 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24429 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24430 line="5",cond="1",times="0",ignore="3"@}]@}
24434 @subheading The @code{-break-delete} Command
24435 @findex -break-delete
24437 @subsubheading Synopsis
24440 -break-delete ( @var{breakpoint} )+
24443 Delete the breakpoint(s) whose number(s) are specified in the argument
24444 list. This is obviously reflected in the breakpoint list.
24446 @subsubheading @value{GDBN} Command
24448 The corresponding @value{GDBN} command is @samp{delete}.
24450 @subsubheading Example
24458 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24459 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24460 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24461 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24462 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24463 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24464 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24469 @subheading The @code{-break-disable} Command
24470 @findex -break-disable
24472 @subsubheading Synopsis
24475 -break-disable ( @var{breakpoint} )+
24478 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
24479 break list is now set to @samp{n} for the named @var{breakpoint}(s).
24481 @subsubheading @value{GDBN} Command
24483 The corresponding @value{GDBN} command is @samp{disable}.
24485 @subsubheading Example
24493 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24494 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24495 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24496 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24497 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24498 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24499 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24500 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
24501 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24502 line="5",times="0"@}]@}
24506 @subheading The @code{-break-enable} Command
24507 @findex -break-enable
24509 @subsubheading Synopsis
24512 -break-enable ( @var{breakpoint} )+
24515 Enable (previously disabled) @var{breakpoint}(s).
24517 @subsubheading @value{GDBN} Command
24519 The corresponding @value{GDBN} command is @samp{enable}.
24521 @subsubheading Example
24529 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24530 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24531 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24532 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24533 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24534 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24535 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24536 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24537 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24538 line="5",times="0"@}]@}
24542 @subheading The @code{-break-info} Command
24543 @findex -break-info
24545 @subsubheading Synopsis
24548 -break-info @var{breakpoint}
24552 Get information about a single breakpoint.
24554 @subsubheading @value{GDBN} Command
24556 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
24558 @subsubheading Example
24561 @subheading The @code{-break-insert} Command
24562 @findex -break-insert
24564 @subsubheading Synopsis
24567 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
24568 [ -c @var{condition} ] [ -i @var{ignore-count} ]
24569 [ -p @var{thread} ] [ @var{location} ]
24573 If specified, @var{location}, can be one of:
24580 @item filename:linenum
24581 @item filename:function
24585 The possible optional parameters of this command are:
24589 Insert a temporary breakpoint.
24591 Insert a hardware breakpoint.
24592 @item -c @var{condition}
24593 Make the breakpoint conditional on @var{condition}.
24594 @item -i @var{ignore-count}
24595 Initialize the @var{ignore-count}.
24597 If @var{location} cannot be parsed (for example if it
24598 refers to unknown files or functions), create a pending
24599 breakpoint. Without this flag, @value{GDBN} will report
24600 an error, and won't create a breakpoint, if @var{location}
24603 Create a disabled breakpoint.
24605 Create a tracepoint. @xref{Tracepoints}. When this parameter
24606 is used together with @samp{-h}, a fast tracepoint is created.
24609 @subsubheading Result
24611 The result is in the form:
24614 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
24615 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
24616 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
24617 times="@var{times}"@}
24621 where @var{number} is the @value{GDBN} number for this breakpoint,
24622 @var{funcname} is the name of the function where the breakpoint was
24623 inserted, @var{filename} is the name of the source file which contains
24624 this function, @var{lineno} is the source line number within that file
24625 and @var{times} the number of times that the breakpoint has been hit
24626 (always 0 for -break-insert but may be greater for -break-info or -break-list
24627 which use the same output).
24629 Note: this format is open to change.
24630 @c An out-of-band breakpoint instead of part of the result?
24632 @subsubheading @value{GDBN} Command
24634 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
24635 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
24637 @subsubheading Example
24642 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
24643 fullname="/home/foo/recursive2.c,line="4",times="0"@}
24645 -break-insert -t foo
24646 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
24647 fullname="/home/foo/recursive2.c,line="11",times="0"@}
24650 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24651 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24652 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24653 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24654 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24655 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24656 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24657 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24658 addr="0x0001072c", func="main",file="recursive2.c",
24659 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
24660 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
24661 addr="0x00010774",func="foo",file="recursive2.c",
24662 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
24664 -break-insert -r foo.*
24665 ~int foo(int, int);
24666 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
24667 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
24671 @subheading The @code{-break-list} Command
24672 @findex -break-list
24674 @subsubheading Synopsis
24680 Displays the list of inserted breakpoints, showing the following fields:
24684 number of the breakpoint
24686 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
24688 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
24691 is the breakpoint enabled or no: @samp{y} or @samp{n}
24693 memory location at which the breakpoint is set
24695 logical location of the breakpoint, expressed by function name, file
24698 number of times the breakpoint has been hit
24701 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
24702 @code{body} field is an empty list.
24704 @subsubheading @value{GDBN} Command
24706 The corresponding @value{GDBN} command is @samp{info break}.
24708 @subsubheading Example
24713 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24714 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24715 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24716 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24717 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24718 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24719 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24720 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24721 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
24722 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24723 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
24724 line="13",times="0"@}]@}
24728 Here's an example of the result when there are no breakpoints:
24733 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24734 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24735 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24736 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24737 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24738 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24739 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24744 @subheading The @code{-break-passcount} Command
24745 @findex -break-passcount
24747 @subsubheading Synopsis
24750 -break-passcount @var{tracepoint-number} @var{passcount}
24753 Set the passcount for tracepoint @var{tracepoint-number} to
24754 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
24755 is not a tracepoint, error is emitted. This corresponds to CLI
24756 command @samp{passcount}.
24758 @subheading The @code{-break-watch} Command
24759 @findex -break-watch
24761 @subsubheading Synopsis
24764 -break-watch [ -a | -r ]
24767 Create a watchpoint. With the @samp{-a} option it will create an
24768 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
24769 read from or on a write to the memory location. With the @samp{-r}
24770 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
24771 trigger only when the memory location is accessed for reading. Without
24772 either of the options, the watchpoint created is a regular watchpoint,
24773 i.e., it will trigger when the memory location is accessed for writing.
24774 @xref{Set Watchpoints, , Setting Watchpoints}.
24776 Note that @samp{-break-list} will report a single list of watchpoints and
24777 breakpoints inserted.
24779 @subsubheading @value{GDBN} Command
24781 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
24784 @subsubheading Example
24786 Setting a watchpoint on a variable in the @code{main} function:
24791 ^done,wpt=@{number="2",exp="x"@}
24796 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
24797 value=@{old="-268439212",new="55"@},
24798 frame=@{func="main",args=[],file="recursive2.c",
24799 fullname="/home/foo/bar/recursive2.c",line="5"@}
24803 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
24804 the program execution twice: first for the variable changing value, then
24805 for the watchpoint going out of scope.
24810 ^done,wpt=@{number="5",exp="C"@}
24815 *stopped,reason="watchpoint-trigger",
24816 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
24817 frame=@{func="callee4",args=[],
24818 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24819 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24824 *stopped,reason="watchpoint-scope",wpnum="5",
24825 frame=@{func="callee3",args=[@{name="strarg",
24826 value="0x11940 \"A string argument.\""@}],
24827 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24828 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24832 Listing breakpoints and watchpoints, at different points in the program
24833 execution. Note that once the watchpoint goes out of scope, it is
24839 ^done,wpt=@{number="2",exp="C"@}
24842 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24843 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24844 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24845 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24846 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24847 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24848 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24849 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24850 addr="0x00010734",func="callee4",
24851 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24852 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
24853 bkpt=@{number="2",type="watchpoint",disp="keep",
24854 enabled="y",addr="",what="C",times="0"@}]@}
24859 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
24860 value=@{old="-276895068",new="3"@},
24861 frame=@{func="callee4",args=[],
24862 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24863 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24866 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24867 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24868 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24869 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24870 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24871 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24872 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24873 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24874 addr="0x00010734",func="callee4",
24875 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24876 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
24877 bkpt=@{number="2",type="watchpoint",disp="keep",
24878 enabled="y",addr="",what="C",times="-5"@}]@}
24882 ^done,reason="watchpoint-scope",wpnum="2",
24883 frame=@{func="callee3",args=[@{name="strarg",
24884 value="0x11940 \"A string argument.\""@}],
24885 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24886 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24889 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24890 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24891 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24892 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24893 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24894 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24895 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24896 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24897 addr="0x00010734",func="callee4",
24898 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24899 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
24904 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24905 @node GDB/MI Program Context
24906 @section @sc{gdb/mi} Program Context
24908 @subheading The @code{-exec-arguments} Command
24909 @findex -exec-arguments
24912 @subsubheading Synopsis
24915 -exec-arguments @var{args}
24918 Set the inferior program arguments, to be used in the next
24921 @subsubheading @value{GDBN} Command
24923 The corresponding @value{GDBN} command is @samp{set args}.
24925 @subsubheading Example
24929 -exec-arguments -v word
24936 @subheading The @code{-exec-show-arguments} Command
24937 @findex -exec-show-arguments
24939 @subsubheading Synopsis
24942 -exec-show-arguments
24945 Print the arguments of the program.
24947 @subsubheading @value{GDBN} Command
24949 The corresponding @value{GDBN} command is @samp{show args}.
24951 @subsubheading Example
24956 @subheading The @code{-environment-cd} Command
24957 @findex -environment-cd
24959 @subsubheading Synopsis
24962 -environment-cd @var{pathdir}
24965 Set @value{GDBN}'s working directory.
24967 @subsubheading @value{GDBN} Command
24969 The corresponding @value{GDBN} command is @samp{cd}.
24971 @subsubheading Example
24975 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
24981 @subheading The @code{-environment-directory} Command
24982 @findex -environment-directory
24984 @subsubheading Synopsis
24987 -environment-directory [ -r ] [ @var{pathdir} ]+
24990 Add directories @var{pathdir} to beginning of search path for source files.
24991 If the @samp{-r} option is used, the search path is reset to the default
24992 search path. If directories @var{pathdir} are supplied in addition to the
24993 @samp{-r} option, the search path is first reset and then addition
24995 Multiple directories may be specified, separated by blanks. Specifying
24996 multiple directories in a single command
24997 results in the directories added to the beginning of the
24998 search path in the same order they were presented in the command.
24999 If blanks are needed as
25000 part of a directory name, double-quotes should be used around
25001 the name. In the command output, the path will show up separated
25002 by the system directory-separator character. The directory-separator
25003 character must not be used
25004 in any directory name.
25005 If no directories are specified, the current search path is displayed.
25007 @subsubheading @value{GDBN} Command
25009 The corresponding @value{GDBN} command is @samp{dir}.
25011 @subsubheading Example
25015 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
25016 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
25018 -environment-directory ""
25019 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
25021 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
25022 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
25024 -environment-directory -r
25025 ^done,source-path="$cdir:$cwd"
25030 @subheading The @code{-environment-path} Command
25031 @findex -environment-path
25033 @subsubheading Synopsis
25036 -environment-path [ -r ] [ @var{pathdir} ]+
25039 Add directories @var{pathdir} to beginning of search path for object files.
25040 If the @samp{-r} option is used, the search path is reset to the original
25041 search path that existed at gdb start-up. If directories @var{pathdir} are
25042 supplied in addition to the
25043 @samp{-r} option, the search path is first reset and then addition
25045 Multiple directories may be specified, separated by blanks. Specifying
25046 multiple directories in a single command
25047 results in the directories added to the beginning of the
25048 search path in the same order they were presented in the command.
25049 If blanks are needed as
25050 part of a directory name, double-quotes should be used around
25051 the name. In the command output, the path will show up separated
25052 by the system directory-separator character. The directory-separator
25053 character must not be used
25054 in any directory name.
25055 If no directories are specified, the current path is displayed.
25058 @subsubheading @value{GDBN} Command
25060 The corresponding @value{GDBN} command is @samp{path}.
25062 @subsubheading Example
25067 ^done,path="/usr/bin"
25069 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
25070 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
25072 -environment-path -r /usr/local/bin
25073 ^done,path="/usr/local/bin:/usr/bin"
25078 @subheading The @code{-environment-pwd} Command
25079 @findex -environment-pwd
25081 @subsubheading Synopsis
25087 Show the current working directory.
25089 @subsubheading @value{GDBN} Command
25091 The corresponding @value{GDBN} command is @samp{pwd}.
25093 @subsubheading Example
25098 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
25102 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25103 @node GDB/MI Thread Commands
25104 @section @sc{gdb/mi} Thread Commands
25107 @subheading The @code{-thread-info} Command
25108 @findex -thread-info
25110 @subsubheading Synopsis
25113 -thread-info [ @var{thread-id} ]
25116 Reports information about either a specific thread, if
25117 the @var{thread-id} parameter is present, or about all
25118 threads. When printing information about all threads,
25119 also reports the current thread.
25121 @subsubheading @value{GDBN} Command
25123 The @samp{info thread} command prints the same information
25126 @subsubheading Example
25131 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
25132 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
25133 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
25134 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
25135 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
25136 current-thread-id="1"
25140 The @samp{state} field may have the following values:
25144 The thread is stopped. Frame information is available for stopped
25148 The thread is running. There's no frame information for running
25153 @subheading The @code{-thread-list-ids} Command
25154 @findex -thread-list-ids
25156 @subsubheading Synopsis
25162 Produces a list of the currently known @value{GDBN} thread ids. At the
25163 end of the list it also prints the total number of such threads.
25165 This command is retained for historical reasons, the
25166 @code{-thread-info} command should be used instead.
25168 @subsubheading @value{GDBN} Command
25170 Part of @samp{info threads} supplies the same information.
25172 @subsubheading Example
25177 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25178 current-thread-id="1",number-of-threads="3"
25183 @subheading The @code{-thread-select} Command
25184 @findex -thread-select
25186 @subsubheading Synopsis
25189 -thread-select @var{threadnum}
25192 Make @var{threadnum} the current thread. It prints the number of the new
25193 current thread, and the topmost frame for that thread.
25195 This command is deprecated in favor of explicitly using the
25196 @samp{--thread} option to each command.
25198 @subsubheading @value{GDBN} Command
25200 The corresponding @value{GDBN} command is @samp{thread}.
25202 @subsubheading Example
25209 *stopped,reason="end-stepping-range",thread-id="2",line="187",
25210 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
25214 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25215 number-of-threads="3"
25218 ^done,new-thread-id="3",
25219 frame=@{level="0",func="vprintf",
25220 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
25221 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
25225 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25226 @node GDB/MI Program Execution
25227 @section @sc{gdb/mi} Program Execution
25229 These are the asynchronous commands which generate the out-of-band
25230 record @samp{*stopped}. Currently @value{GDBN} only really executes
25231 asynchronously with remote targets and this interaction is mimicked in
25234 @subheading The @code{-exec-continue} Command
25235 @findex -exec-continue
25237 @subsubheading Synopsis
25240 -exec-continue [--reverse] [--all|--thread-group N]
25243 Resumes the execution of the inferior program, which will continue
25244 to execute until it reaches a debugger stop event. If the
25245 @samp{--reverse} option is specified, execution resumes in reverse until
25246 it reaches a stop event. Stop events may include
25249 breakpoints or watchpoints
25251 signals or exceptions
25253 the end of the process (or its beginning under @samp{--reverse})
25255 the end or beginning of a replay log if one is being used.
25257 In all-stop mode (@pxref{All-Stop
25258 Mode}), may resume only one thread, or all threads, depending on the
25259 value of the @samp{scheduler-locking} variable. If @samp{--all} is
25260 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
25261 ignored in all-stop mode. If the @samp{--thread-group} options is
25262 specified, then all threads in that thread group are resumed.
25264 @subsubheading @value{GDBN} Command
25266 The corresponding @value{GDBN} corresponding is @samp{continue}.
25268 @subsubheading Example
25275 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
25276 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
25282 @subheading The @code{-exec-finish} Command
25283 @findex -exec-finish
25285 @subsubheading Synopsis
25288 -exec-finish [--reverse]
25291 Resumes the execution of the inferior program until the current
25292 function is exited. Displays the results returned by the function.
25293 If the @samp{--reverse} option is specified, resumes the reverse
25294 execution of the inferior program until the point where current
25295 function was called.
25297 @subsubheading @value{GDBN} Command
25299 The corresponding @value{GDBN} command is @samp{finish}.
25301 @subsubheading Example
25303 Function returning @code{void}.
25310 *stopped,reason="function-finished",frame=@{func="main",args=[],
25311 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
25315 Function returning other than @code{void}. The name of the internal
25316 @value{GDBN} variable storing the result is printed, together with the
25323 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
25324 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
25325 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25326 gdb-result-var="$1",return-value="0"
25331 @subheading The @code{-exec-interrupt} Command
25332 @findex -exec-interrupt
25334 @subsubheading Synopsis
25337 -exec-interrupt [--all|--thread-group N]
25340 Interrupts the background execution of the target. Note how the token
25341 associated with the stop message is the one for the execution command
25342 that has been interrupted. The token for the interrupt itself only
25343 appears in the @samp{^done} output. If the user is trying to
25344 interrupt a non-running program, an error message will be printed.
25346 Note that when asynchronous execution is enabled, this command is
25347 asynchronous just like other execution commands. That is, first the
25348 @samp{^done} response will be printed, and the target stop will be
25349 reported after that using the @samp{*stopped} notification.
25351 In non-stop mode, only the context thread is interrupted by default.
25352 All threads (in all inferiors) will be interrupted if the
25353 @samp{--all} option is specified. If the @samp{--thread-group}
25354 option is specified, all threads in that group will be interrupted.
25356 @subsubheading @value{GDBN} Command
25358 The corresponding @value{GDBN} command is @samp{interrupt}.
25360 @subsubheading Example
25371 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
25372 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
25373 fullname="/home/foo/bar/try.c",line="13"@}
25378 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
25382 @subheading The @code{-exec-jump} Command
25385 @subsubheading Synopsis
25388 -exec-jump @var{location}
25391 Resumes execution of the inferior program at the location specified by
25392 parameter. @xref{Specify Location}, for a description of the
25393 different forms of @var{location}.
25395 @subsubheading @value{GDBN} Command
25397 The corresponding @value{GDBN} command is @samp{jump}.
25399 @subsubheading Example
25402 -exec-jump foo.c:10
25403 *running,thread-id="all"
25408 @subheading The @code{-exec-next} Command
25411 @subsubheading Synopsis
25414 -exec-next [--reverse]
25417 Resumes execution of the inferior program, stopping when the beginning
25418 of the next source line is reached.
25420 If the @samp{--reverse} option is specified, resumes reverse execution
25421 of the inferior program, stopping at the beginning of the previous
25422 source line. If you issue this command on the first line of a
25423 function, it will take you back to the caller of that function, to the
25424 source line where the function was called.
25427 @subsubheading @value{GDBN} Command
25429 The corresponding @value{GDBN} command is @samp{next}.
25431 @subsubheading Example
25437 *stopped,reason="end-stepping-range",line="8",file="hello.c"
25442 @subheading The @code{-exec-next-instruction} Command
25443 @findex -exec-next-instruction
25445 @subsubheading Synopsis
25448 -exec-next-instruction [--reverse]
25451 Executes one machine instruction. If the instruction is a function
25452 call, continues until the function returns. If the program stops at an
25453 instruction in the middle of a source line, the address will be
25456 If the @samp{--reverse} option is specified, resumes reverse execution
25457 of the inferior program, stopping at the previous instruction. If the
25458 previously executed instruction was a return from another function,
25459 it will continue to execute in reverse until the call to that function
25460 (from the current stack frame) is reached.
25462 @subsubheading @value{GDBN} Command
25464 The corresponding @value{GDBN} command is @samp{nexti}.
25466 @subsubheading Example
25470 -exec-next-instruction
25474 *stopped,reason="end-stepping-range",
25475 addr="0x000100d4",line="5",file="hello.c"
25480 @subheading The @code{-exec-return} Command
25481 @findex -exec-return
25483 @subsubheading Synopsis
25489 Makes current function return immediately. Doesn't execute the inferior.
25490 Displays the new current frame.
25492 @subsubheading @value{GDBN} Command
25494 The corresponding @value{GDBN} command is @samp{return}.
25496 @subsubheading Example
25500 200-break-insert callee4
25501 200^done,bkpt=@{number="1",addr="0x00010734",
25502 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25507 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25508 frame=@{func="callee4",args=[],
25509 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25510 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25516 111^done,frame=@{level="0",func="callee3",
25517 args=[@{name="strarg",
25518 value="0x11940 \"A string argument.\""@}],
25519 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25520 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25525 @subheading The @code{-exec-run} Command
25528 @subsubheading Synopsis
25531 -exec-run [--all | --thread-group N]
25534 Starts execution of the inferior from the beginning. The inferior
25535 executes until either a breakpoint is encountered or the program
25536 exits. In the latter case the output will include an exit code, if
25537 the program has exited exceptionally.
25539 When no option is specified, the current inferior is started. If the
25540 @samp{--thread-group} option is specified, it should refer to a thread
25541 group of type @samp{process}, and that thread group will be started.
25542 If the @samp{--all} option is specified, then all inferiors will be started.
25544 @subsubheading @value{GDBN} Command
25546 The corresponding @value{GDBN} command is @samp{run}.
25548 @subsubheading Examples
25553 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
25558 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25559 frame=@{func="main",args=[],file="recursive2.c",
25560 fullname="/home/foo/bar/recursive2.c",line="4"@}
25565 Program exited normally:
25573 *stopped,reason="exited-normally"
25578 Program exited exceptionally:
25586 *stopped,reason="exited",exit-code="01"
25590 Another way the program can terminate is if it receives a signal such as
25591 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
25595 *stopped,reason="exited-signalled",signal-name="SIGINT",
25596 signal-meaning="Interrupt"
25600 @c @subheading -exec-signal
25603 @subheading The @code{-exec-step} Command
25606 @subsubheading Synopsis
25609 -exec-step [--reverse]
25612 Resumes execution of the inferior program, stopping when the beginning
25613 of the next source line is reached, if the next source line is not a
25614 function call. If it is, stop at the first instruction of the called
25615 function. If the @samp{--reverse} option is specified, resumes reverse
25616 execution of the inferior program, stopping at the beginning of the
25617 previously executed source line.
25619 @subsubheading @value{GDBN} Command
25621 The corresponding @value{GDBN} command is @samp{step}.
25623 @subsubheading Example
25625 Stepping into a function:
25631 *stopped,reason="end-stepping-range",
25632 frame=@{func="foo",args=[@{name="a",value="10"@},
25633 @{name="b",value="0"@}],file="recursive2.c",
25634 fullname="/home/foo/bar/recursive2.c",line="11"@}
25644 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
25649 @subheading The @code{-exec-step-instruction} Command
25650 @findex -exec-step-instruction
25652 @subsubheading Synopsis
25655 -exec-step-instruction [--reverse]
25658 Resumes the inferior which executes one machine instruction. If the
25659 @samp{--reverse} option is specified, resumes reverse execution of the
25660 inferior program, stopping at the previously executed instruction.
25661 The output, once @value{GDBN} has stopped, will vary depending on
25662 whether we have stopped in the middle of a source line or not. In the
25663 former case, the address at which the program stopped will be printed
25666 @subsubheading @value{GDBN} Command
25668 The corresponding @value{GDBN} command is @samp{stepi}.
25670 @subsubheading Example
25674 -exec-step-instruction
25678 *stopped,reason="end-stepping-range",
25679 frame=@{func="foo",args=[],file="try.c",
25680 fullname="/home/foo/bar/try.c",line="10"@}
25682 -exec-step-instruction
25686 *stopped,reason="end-stepping-range",
25687 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
25688 fullname="/home/foo/bar/try.c",line="10"@}
25693 @subheading The @code{-exec-until} Command
25694 @findex -exec-until
25696 @subsubheading Synopsis
25699 -exec-until [ @var{location} ]
25702 Executes the inferior until the @var{location} specified in the
25703 argument is reached. If there is no argument, the inferior executes
25704 until a source line greater than the current one is reached. The
25705 reason for stopping in this case will be @samp{location-reached}.
25707 @subsubheading @value{GDBN} Command
25709 The corresponding @value{GDBN} command is @samp{until}.
25711 @subsubheading Example
25715 -exec-until recursive2.c:6
25719 *stopped,reason="location-reached",frame=@{func="main",args=[],
25720 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
25725 @subheading -file-clear
25726 Is this going away????
25729 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25730 @node GDB/MI Stack Manipulation
25731 @section @sc{gdb/mi} Stack Manipulation Commands
25734 @subheading The @code{-stack-info-frame} Command
25735 @findex -stack-info-frame
25737 @subsubheading Synopsis
25743 Get info on the selected frame.
25745 @subsubheading @value{GDBN} Command
25747 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
25748 (without arguments).
25750 @subsubheading Example
25755 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
25756 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25757 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
25761 @subheading The @code{-stack-info-depth} Command
25762 @findex -stack-info-depth
25764 @subsubheading Synopsis
25767 -stack-info-depth [ @var{max-depth} ]
25770 Return the depth of the stack. If the integer argument @var{max-depth}
25771 is specified, do not count beyond @var{max-depth} frames.
25773 @subsubheading @value{GDBN} Command
25775 There's no equivalent @value{GDBN} command.
25777 @subsubheading Example
25779 For a stack with frame levels 0 through 11:
25786 -stack-info-depth 4
25789 -stack-info-depth 12
25792 -stack-info-depth 11
25795 -stack-info-depth 13
25800 @subheading The @code{-stack-list-arguments} Command
25801 @findex -stack-list-arguments
25803 @subsubheading Synopsis
25806 -stack-list-arguments @var{print-values}
25807 [ @var{low-frame} @var{high-frame} ]
25810 Display a list of the arguments for the frames between @var{low-frame}
25811 and @var{high-frame} (inclusive). If @var{low-frame} and
25812 @var{high-frame} are not provided, list the arguments for the whole
25813 call stack. If the two arguments are equal, show the single frame
25814 at the corresponding level. It is an error if @var{low-frame} is
25815 larger than the actual number of frames. On the other hand,
25816 @var{high-frame} may be larger than the actual number of frames, in
25817 which case only existing frames will be returned.
25819 If @var{print-values} is 0 or @code{--no-values}, print only the names of
25820 the variables; if it is 1 or @code{--all-values}, print also their
25821 values; and if it is 2 or @code{--simple-values}, print the name,
25822 type and value for simple data types, and the name and type for arrays,
25823 structures and unions.
25825 Use of this command to obtain arguments in a single frame is
25826 deprecated in favor of the @samp{-stack-list-variables} command.
25828 @subsubheading @value{GDBN} Command
25830 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
25831 @samp{gdb_get_args} command which partially overlaps with the
25832 functionality of @samp{-stack-list-arguments}.
25834 @subsubheading Example
25841 frame=@{level="0",addr="0x00010734",func="callee4",
25842 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25843 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
25844 frame=@{level="1",addr="0x0001076c",func="callee3",
25845 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25846 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
25847 frame=@{level="2",addr="0x0001078c",func="callee2",
25848 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25849 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
25850 frame=@{level="3",addr="0x000107b4",func="callee1",
25851 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25852 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
25853 frame=@{level="4",addr="0x000107e0",func="main",
25854 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25855 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
25857 -stack-list-arguments 0
25860 frame=@{level="0",args=[]@},
25861 frame=@{level="1",args=[name="strarg"]@},
25862 frame=@{level="2",args=[name="intarg",name="strarg"]@},
25863 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
25864 frame=@{level="4",args=[]@}]
25866 -stack-list-arguments 1
25869 frame=@{level="0",args=[]@},
25871 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25872 frame=@{level="2",args=[
25873 @{name="intarg",value="2"@},
25874 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25875 @{frame=@{level="3",args=[
25876 @{name="intarg",value="2"@},
25877 @{name="strarg",value="0x11940 \"A string argument.\""@},
25878 @{name="fltarg",value="3.5"@}]@},
25879 frame=@{level="4",args=[]@}]
25881 -stack-list-arguments 0 2 2
25882 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
25884 -stack-list-arguments 1 2 2
25885 ^done,stack-args=[frame=@{level="2",
25886 args=[@{name="intarg",value="2"@},
25887 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
25891 @c @subheading -stack-list-exception-handlers
25894 @subheading The @code{-stack-list-frames} Command
25895 @findex -stack-list-frames
25897 @subsubheading Synopsis
25900 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
25903 List the frames currently on the stack. For each frame it displays the
25908 The frame number, 0 being the topmost frame, i.e., the innermost function.
25910 The @code{$pc} value for that frame.
25914 File name of the source file where the function lives.
25916 Line number corresponding to the @code{$pc}.
25919 If invoked without arguments, this command prints a backtrace for the
25920 whole stack. If given two integer arguments, it shows the frames whose
25921 levels are between the two arguments (inclusive). If the two arguments
25922 are equal, it shows the single frame at the corresponding level. It is
25923 an error if @var{low-frame} is larger than the actual number of
25924 frames. On the other hand, @var{high-frame} may be larger than the
25925 actual number of frames, in which case only existing frames will be returned.
25927 @subsubheading @value{GDBN} Command
25929 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
25931 @subsubheading Example
25933 Full stack backtrace:
25939 [frame=@{level="0",addr="0x0001076c",func="foo",
25940 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
25941 frame=@{level="1",addr="0x000107a4",func="foo",
25942 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25943 frame=@{level="2",addr="0x000107a4",func="foo",
25944 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25945 frame=@{level="3",addr="0x000107a4",func="foo",
25946 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25947 frame=@{level="4",addr="0x000107a4",func="foo",
25948 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25949 frame=@{level="5",addr="0x000107a4",func="foo",
25950 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25951 frame=@{level="6",addr="0x000107a4",func="foo",
25952 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25953 frame=@{level="7",addr="0x000107a4",func="foo",
25954 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25955 frame=@{level="8",addr="0x000107a4",func="foo",
25956 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25957 frame=@{level="9",addr="0x000107a4",func="foo",
25958 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25959 frame=@{level="10",addr="0x000107a4",func="foo",
25960 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25961 frame=@{level="11",addr="0x00010738",func="main",
25962 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
25966 Show frames between @var{low_frame} and @var{high_frame}:
25970 -stack-list-frames 3 5
25972 [frame=@{level="3",addr="0x000107a4",func="foo",
25973 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25974 frame=@{level="4",addr="0x000107a4",func="foo",
25975 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25976 frame=@{level="5",addr="0x000107a4",func="foo",
25977 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
25981 Show a single frame:
25985 -stack-list-frames 3 3
25987 [frame=@{level="3",addr="0x000107a4",func="foo",
25988 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
25993 @subheading The @code{-stack-list-locals} Command
25994 @findex -stack-list-locals
25996 @subsubheading Synopsis
25999 -stack-list-locals @var{print-values}
26002 Display the local variable names for the selected frame. If
26003 @var{print-values} is 0 or @code{--no-values}, print only the names of
26004 the variables; if it is 1 or @code{--all-values}, print also their
26005 values; and if it is 2 or @code{--simple-values}, print the name,
26006 type and value for simple data types, and the name and type for arrays,
26007 structures and unions. In this last case, a frontend can immediately
26008 display the value of simple data types and create variable objects for
26009 other data types when the user wishes to explore their values in
26012 This command is deprecated in favor of the
26013 @samp{-stack-list-variables} command.
26015 @subsubheading @value{GDBN} Command
26017 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
26019 @subsubheading Example
26023 -stack-list-locals 0
26024 ^done,locals=[name="A",name="B",name="C"]
26026 -stack-list-locals --all-values
26027 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
26028 @{name="C",value="@{1, 2, 3@}"@}]
26029 -stack-list-locals --simple-values
26030 ^done,locals=[@{name="A",type="int",value="1"@},
26031 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
26035 @subheading The @code{-stack-list-variables} Command
26036 @findex -stack-list-variables
26038 @subsubheading Synopsis
26041 -stack-list-variables @var{print-values}
26044 Display the names of local variables and function arguments for the selected frame. If
26045 @var{print-values} is 0 or @code{--no-values}, print only the names of
26046 the variables; if it is 1 or @code{--all-values}, print also their
26047 values; and if it is 2 or @code{--simple-values}, print the name,
26048 type and value for simple data types, and the name and type for arrays,
26049 structures and unions.
26051 @subsubheading Example
26055 -stack-list-variables --thread 1 --frame 0 --all-values
26056 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
26061 @subheading The @code{-stack-select-frame} Command
26062 @findex -stack-select-frame
26064 @subsubheading Synopsis
26067 -stack-select-frame @var{framenum}
26070 Change the selected frame. Select a different frame @var{framenum} on
26073 This command in deprecated in favor of passing the @samp{--frame}
26074 option to every command.
26076 @subsubheading @value{GDBN} Command
26078 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
26079 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
26081 @subsubheading Example
26085 -stack-select-frame 2
26090 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26091 @node GDB/MI Variable Objects
26092 @section @sc{gdb/mi} Variable Objects
26096 @subheading Motivation for Variable Objects in @sc{gdb/mi}
26098 For the implementation of a variable debugger window (locals, watched
26099 expressions, etc.), we are proposing the adaptation of the existing code
26100 used by @code{Insight}.
26102 The two main reasons for that are:
26106 It has been proven in practice (it is already on its second generation).
26109 It will shorten development time (needless to say how important it is
26113 The original interface was designed to be used by Tcl code, so it was
26114 slightly changed so it could be used through @sc{gdb/mi}. This section
26115 describes the @sc{gdb/mi} operations that will be available and gives some
26116 hints about their use.
26118 @emph{Note}: In addition to the set of operations described here, we
26119 expect the @sc{gui} implementation of a variable window to require, at
26120 least, the following operations:
26123 @item @code{-gdb-show} @code{output-radix}
26124 @item @code{-stack-list-arguments}
26125 @item @code{-stack-list-locals}
26126 @item @code{-stack-select-frame}
26131 @subheading Introduction to Variable Objects
26133 @cindex variable objects in @sc{gdb/mi}
26135 Variable objects are "object-oriented" MI interface for examining and
26136 changing values of expressions. Unlike some other MI interfaces that
26137 work with expressions, variable objects are specifically designed for
26138 simple and efficient presentation in the frontend. A variable object
26139 is identified by string name. When a variable object is created, the
26140 frontend specifies the expression for that variable object. The
26141 expression can be a simple variable, or it can be an arbitrary complex
26142 expression, and can even involve CPU registers. After creating a
26143 variable object, the frontend can invoke other variable object
26144 operations---for example to obtain or change the value of a variable
26145 object, or to change display format.
26147 Variable objects have hierarchical tree structure. Any variable object
26148 that corresponds to a composite type, such as structure in C, has
26149 a number of child variable objects, for example corresponding to each
26150 element of a structure. A child variable object can itself have
26151 children, recursively. Recursion ends when we reach
26152 leaf variable objects, which always have built-in types. Child variable
26153 objects are created only by explicit request, so if a frontend
26154 is not interested in the children of a particular variable object, no
26155 child will be created.
26157 For a leaf variable object it is possible to obtain its value as a
26158 string, or set the value from a string. String value can be also
26159 obtained for a non-leaf variable object, but it's generally a string
26160 that only indicates the type of the object, and does not list its
26161 contents. Assignment to a non-leaf variable object is not allowed.
26163 A frontend does not need to read the values of all variable objects each time
26164 the program stops. Instead, MI provides an update command that lists all
26165 variable objects whose values has changed since the last update
26166 operation. This considerably reduces the amount of data that must
26167 be transferred to the frontend. As noted above, children variable
26168 objects are created on demand, and only leaf variable objects have a
26169 real value. As result, gdb will read target memory only for leaf
26170 variables that frontend has created.
26172 The automatic update is not always desirable. For example, a frontend
26173 might want to keep a value of some expression for future reference,
26174 and never update it. For another example, fetching memory is
26175 relatively slow for embedded targets, so a frontend might want
26176 to disable automatic update for the variables that are either not
26177 visible on the screen, or ``closed''. This is possible using so
26178 called ``frozen variable objects''. Such variable objects are never
26179 implicitly updated.
26181 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
26182 fixed variable object, the expression is parsed when the variable
26183 object is created, including associating identifiers to specific
26184 variables. The meaning of expression never changes. For a floating
26185 variable object the values of variables whose names appear in the
26186 expressions are re-evaluated every time in the context of the current
26187 frame. Consider this example:
26192 struct work_state state;
26199 If a fixed variable object for the @code{state} variable is created in
26200 this function, and we enter the recursive call, the the variable
26201 object will report the value of @code{state} in the top-level
26202 @code{do_work} invocation. On the other hand, a floating variable
26203 object will report the value of @code{state} in the current frame.
26205 If an expression specified when creating a fixed variable object
26206 refers to a local variable, the variable object becomes bound to the
26207 thread and frame in which the variable object is created. When such
26208 variable object is updated, @value{GDBN} makes sure that the
26209 thread/frame combination the variable object is bound to still exists,
26210 and re-evaluates the variable object in context of that thread/frame.
26212 The following is the complete set of @sc{gdb/mi} operations defined to
26213 access this functionality:
26215 @multitable @columnfractions .4 .6
26216 @item @strong{Operation}
26217 @tab @strong{Description}
26219 @item @code{-enable-pretty-printing}
26220 @tab enable Python-based pretty-printing
26221 @item @code{-var-create}
26222 @tab create a variable object
26223 @item @code{-var-delete}
26224 @tab delete the variable object and/or its children
26225 @item @code{-var-set-format}
26226 @tab set the display format of this variable
26227 @item @code{-var-show-format}
26228 @tab show the display format of this variable
26229 @item @code{-var-info-num-children}
26230 @tab tells how many children this object has
26231 @item @code{-var-list-children}
26232 @tab return a list of the object's children
26233 @item @code{-var-info-type}
26234 @tab show the type of this variable object
26235 @item @code{-var-info-expression}
26236 @tab print parent-relative expression that this variable object represents
26237 @item @code{-var-info-path-expression}
26238 @tab print full expression that this variable object represents
26239 @item @code{-var-show-attributes}
26240 @tab is this variable editable? does it exist here?
26241 @item @code{-var-evaluate-expression}
26242 @tab get the value of this variable
26243 @item @code{-var-assign}
26244 @tab set the value of this variable
26245 @item @code{-var-update}
26246 @tab update the variable and its children
26247 @item @code{-var-set-frozen}
26248 @tab set frozeness attribute
26249 @item @code{-var-set-update-range}
26250 @tab set range of children to display on update
26253 In the next subsection we describe each operation in detail and suggest
26254 how it can be used.
26256 @subheading Description And Use of Operations on Variable Objects
26258 @subheading The @code{-enable-pretty-printing} Command
26259 @findex -enable-pretty-printing
26262 -enable-pretty-printing
26265 @value{GDBN} allows Python-based visualizers to affect the output of the
26266 MI variable object commands. However, because there was no way to
26267 implement this in a fully backward-compatible way, a front end must
26268 request that this functionality be enabled.
26270 Once enabled, this feature cannot be disabled.
26272 Note that if Python support has not been compiled into @value{GDBN},
26273 this command will still succeed (and do nothing).
26275 This feature is currently (as of @value{GDBN} 7.0) experimental, and
26276 may work differently in future versions of @value{GDBN}.
26278 @subheading The @code{-var-create} Command
26279 @findex -var-create
26281 @subsubheading Synopsis
26284 -var-create @{@var{name} | "-"@}
26285 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
26288 This operation creates a variable object, which allows the monitoring of
26289 a variable, the result of an expression, a memory cell or a CPU
26292 The @var{name} parameter is the string by which the object can be
26293 referenced. It must be unique. If @samp{-} is specified, the varobj
26294 system will generate a string ``varNNNNNN'' automatically. It will be
26295 unique provided that one does not specify @var{name} of that format.
26296 The command fails if a duplicate name is found.
26298 The frame under which the expression should be evaluated can be
26299 specified by @var{frame-addr}. A @samp{*} indicates that the current
26300 frame should be used. A @samp{@@} indicates that a floating variable
26301 object must be created.
26303 @var{expression} is any expression valid on the current language set (must not
26304 begin with a @samp{*}), or one of the following:
26308 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
26311 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
26314 @samp{$@var{regname}} --- a CPU register name
26317 @cindex dynamic varobj
26318 A varobj's contents may be provided by a Python-based pretty-printer. In this
26319 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
26320 have slightly different semantics in some cases. If the
26321 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
26322 will never create a dynamic varobj. This ensures backward
26323 compatibility for existing clients.
26325 @subsubheading Result
26327 This operation returns attributes of the newly-created varobj. These
26332 The name of the varobj.
26335 The number of children of the varobj. This number is not necessarily
26336 reliable for a dynamic varobj. Instead, you must examine the
26337 @samp{has_more} attribute.
26340 The varobj's scalar value. For a varobj whose type is some sort of
26341 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
26342 will not be interesting.
26345 The varobj's type. This is a string representation of the type, as
26346 would be printed by the @value{GDBN} CLI.
26349 If a variable object is bound to a specific thread, then this is the
26350 thread's identifier.
26353 For a dynamic varobj, this indicates whether there appear to be any
26354 children available. For a non-dynamic varobj, this will be 0.
26357 This attribute will be present and have the value @samp{1} if the
26358 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26359 then this attribute will not be present.
26362 A dynamic varobj can supply a display hint to the front end. The
26363 value comes directly from the Python pretty-printer object's
26364 @code{display_hint} method. @xref{Pretty Printing API}.
26367 Typical output will look like this:
26370 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
26371 has_more="@var{has_more}"
26375 @subheading The @code{-var-delete} Command
26376 @findex -var-delete
26378 @subsubheading Synopsis
26381 -var-delete [ -c ] @var{name}
26384 Deletes a previously created variable object and all of its children.
26385 With the @samp{-c} option, just deletes the children.
26387 Returns an error if the object @var{name} is not found.
26390 @subheading The @code{-var-set-format} Command
26391 @findex -var-set-format
26393 @subsubheading Synopsis
26396 -var-set-format @var{name} @var{format-spec}
26399 Sets the output format for the value of the object @var{name} to be
26402 @anchor{-var-set-format}
26403 The syntax for the @var{format-spec} is as follows:
26406 @var{format-spec} @expansion{}
26407 @{binary | decimal | hexadecimal | octal | natural@}
26410 The natural format is the default format choosen automatically
26411 based on the variable type (like decimal for an @code{int}, hex
26412 for pointers, etc.).
26414 For a variable with children, the format is set only on the
26415 variable itself, and the children are not affected.
26417 @subheading The @code{-var-show-format} Command
26418 @findex -var-show-format
26420 @subsubheading Synopsis
26423 -var-show-format @var{name}
26426 Returns the format used to display the value of the object @var{name}.
26429 @var{format} @expansion{}
26434 @subheading The @code{-var-info-num-children} Command
26435 @findex -var-info-num-children
26437 @subsubheading Synopsis
26440 -var-info-num-children @var{name}
26443 Returns the number of children of a variable object @var{name}:
26449 Note that this number is not completely reliable for a dynamic varobj.
26450 It will return the current number of children, but more children may
26454 @subheading The @code{-var-list-children} Command
26455 @findex -var-list-children
26457 @subsubheading Synopsis
26460 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
26462 @anchor{-var-list-children}
26464 Return a list of the children of the specified variable object and
26465 create variable objects for them, if they do not already exist. With
26466 a single argument or if @var{print-values} has a value of 0 or
26467 @code{--no-values}, print only the names of the variables; if
26468 @var{print-values} is 1 or @code{--all-values}, also print their
26469 values; and if it is 2 or @code{--simple-values} print the name and
26470 value for simple data types and just the name for arrays, structures
26473 @var{from} and @var{to}, if specified, indicate the range of children
26474 to report. If @var{from} or @var{to} is less than zero, the range is
26475 reset and all children will be reported. Otherwise, children starting
26476 at @var{from} (zero-based) and up to and excluding @var{to} will be
26479 If a child range is requested, it will only affect the current call to
26480 @code{-var-list-children}, but not future calls to @code{-var-update}.
26481 For this, you must instead use @code{-var-set-update-range}. The
26482 intent of this approach is to enable a front end to implement any
26483 update approach it likes; for example, scrolling a view may cause the
26484 front end to request more children with @code{-var-list-children}, and
26485 then the front end could call @code{-var-set-update-range} with a
26486 different range to ensure that future updates are restricted to just
26489 For each child the following results are returned:
26494 Name of the variable object created for this child.
26497 The expression to be shown to the user by the front end to designate this child.
26498 For example this may be the name of a structure member.
26500 For a dynamic varobj, this value cannot be used to form an
26501 expression. There is no way to do this at all with a dynamic varobj.
26503 For C/C@t{++} structures there are several pseudo children returned to
26504 designate access qualifiers. For these pseudo children @var{exp} is
26505 @samp{public}, @samp{private}, or @samp{protected}. In this case the
26506 type and value are not present.
26508 A dynamic varobj will not report the access qualifying
26509 pseudo-children, regardless of the language. This information is not
26510 available at all with a dynamic varobj.
26513 Number of children this child has. For a dynamic varobj, this will be
26517 The type of the child.
26520 If values were requested, this is the value.
26523 If this variable object is associated with a thread, this is the thread id.
26524 Otherwise this result is not present.
26527 If the variable object is frozen, this variable will be present with a value of 1.
26530 The result may have its own attributes:
26534 A dynamic varobj can supply a display hint to the front end. The
26535 value comes directly from the Python pretty-printer object's
26536 @code{display_hint} method. @xref{Pretty Printing API}.
26539 This is an integer attribute which is nonzero if there are children
26540 remaining after the end of the selected range.
26543 @subsubheading Example
26547 -var-list-children n
26548 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26549 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
26551 -var-list-children --all-values n
26552 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26553 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
26557 @subheading The @code{-var-info-type} Command
26558 @findex -var-info-type
26560 @subsubheading Synopsis
26563 -var-info-type @var{name}
26566 Returns the type of the specified variable @var{name}. The type is
26567 returned as a string in the same format as it is output by the
26571 type=@var{typename}
26575 @subheading The @code{-var-info-expression} Command
26576 @findex -var-info-expression
26578 @subsubheading Synopsis
26581 -var-info-expression @var{name}
26584 Returns a string that is suitable for presenting this
26585 variable object in user interface. The string is generally
26586 not valid expression in the current language, and cannot be evaluated.
26588 For example, if @code{a} is an array, and variable object
26589 @code{A} was created for @code{a}, then we'll get this output:
26592 (gdb) -var-info-expression A.1
26593 ^done,lang="C",exp="1"
26597 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
26599 Note that the output of the @code{-var-list-children} command also
26600 includes those expressions, so the @code{-var-info-expression} command
26603 @subheading The @code{-var-info-path-expression} Command
26604 @findex -var-info-path-expression
26606 @subsubheading Synopsis
26609 -var-info-path-expression @var{name}
26612 Returns an expression that can be evaluated in the current
26613 context and will yield the same value that a variable object has.
26614 Compare this with the @code{-var-info-expression} command, which
26615 result can be used only for UI presentation. Typical use of
26616 the @code{-var-info-path-expression} command is creating a
26617 watchpoint from a variable object.
26619 This command is currently not valid for children of a dynamic varobj,
26620 and will give an error when invoked on one.
26622 For example, suppose @code{C} is a C@t{++} class, derived from class
26623 @code{Base}, and that the @code{Base} class has a member called
26624 @code{m_size}. Assume a variable @code{c} is has the type of
26625 @code{C} and a variable object @code{C} was created for variable
26626 @code{c}. Then, we'll get this output:
26628 (gdb) -var-info-path-expression C.Base.public.m_size
26629 ^done,path_expr=((Base)c).m_size)
26632 @subheading The @code{-var-show-attributes} Command
26633 @findex -var-show-attributes
26635 @subsubheading Synopsis
26638 -var-show-attributes @var{name}
26641 List attributes of the specified variable object @var{name}:
26644 status=@var{attr} [ ( ,@var{attr} )* ]
26648 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
26650 @subheading The @code{-var-evaluate-expression} Command
26651 @findex -var-evaluate-expression
26653 @subsubheading Synopsis
26656 -var-evaluate-expression [-f @var{format-spec}] @var{name}
26659 Evaluates the expression that is represented by the specified variable
26660 object and returns its value as a string. The format of the string
26661 can be specified with the @samp{-f} option. The possible values of
26662 this option are the same as for @code{-var-set-format}
26663 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
26664 the current display format will be used. The current display format
26665 can be changed using the @code{-var-set-format} command.
26671 Note that one must invoke @code{-var-list-children} for a variable
26672 before the value of a child variable can be evaluated.
26674 @subheading The @code{-var-assign} Command
26675 @findex -var-assign
26677 @subsubheading Synopsis
26680 -var-assign @var{name} @var{expression}
26683 Assigns the value of @var{expression} to the variable object specified
26684 by @var{name}. The object must be @samp{editable}. If the variable's
26685 value is altered by the assign, the variable will show up in any
26686 subsequent @code{-var-update} list.
26688 @subsubheading Example
26696 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
26700 @subheading The @code{-var-update} Command
26701 @findex -var-update
26703 @subsubheading Synopsis
26706 -var-update [@var{print-values}] @{@var{name} | "*"@}
26709 Reevaluate the expressions corresponding to the variable object
26710 @var{name} and all its direct and indirect children, and return the
26711 list of variable objects whose values have changed; @var{name} must
26712 be a root variable object. Here, ``changed'' means that the result of
26713 @code{-var-evaluate-expression} before and after the
26714 @code{-var-update} is different. If @samp{*} is used as the variable
26715 object names, all existing variable objects are updated, except
26716 for frozen ones (@pxref{-var-set-frozen}). The option
26717 @var{print-values} determines whether both names and values, or just
26718 names are printed. The possible values of this option are the same
26719 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
26720 recommended to use the @samp{--all-values} option, to reduce the
26721 number of MI commands needed on each program stop.
26723 With the @samp{*} parameter, if a variable object is bound to a
26724 currently running thread, it will not be updated, without any
26727 If @code{-var-set-update-range} was previously used on a varobj, then
26728 only the selected range of children will be reported.
26730 @code{-var-update} reports all the changed varobjs in a tuple named
26733 Each item in the change list is itself a tuple holding:
26737 The name of the varobj.
26740 If values were requested for this update, then this field will be
26741 present and will hold the value of the varobj.
26744 @anchor{-var-update}
26745 This field is a string which may take one of three values:
26749 The variable object's current value is valid.
26752 The variable object does not currently hold a valid value but it may
26753 hold one in the future if its associated expression comes back into
26757 The variable object no longer holds a valid value.
26758 This can occur when the executable file being debugged has changed,
26759 either through recompilation or by using the @value{GDBN} @code{file}
26760 command. The front end should normally choose to delete these variable
26764 In the future new values may be added to this list so the front should
26765 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
26768 This is only present if the varobj is still valid. If the type
26769 changed, then this will be the string @samp{true}; otherwise it will
26773 If the varobj's type changed, then this field will be present and will
26776 @item new_num_children
26777 For a dynamic varobj, if the number of children changed, or if the
26778 type changed, this will be the new number of children.
26780 The @samp{numchild} field in other varobj responses is generally not
26781 valid for a dynamic varobj -- it will show the number of children that
26782 @value{GDBN} knows about, but because dynamic varobjs lazily
26783 instantiate their children, this will not reflect the number of
26784 children which may be available.
26786 The @samp{new_num_children} attribute only reports changes to the
26787 number of children known by @value{GDBN}. This is the only way to
26788 detect whether an update has removed children (which necessarily can
26789 only happen at the end of the update range).
26792 The display hint, if any.
26795 This is an integer value, which will be 1 if there are more children
26796 available outside the varobj's update range.
26799 This attribute will be present and have the value @samp{1} if the
26800 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26801 then this attribute will not be present.
26804 If new children were added to a dynamic varobj within the selected
26805 update range (as set by @code{-var-set-update-range}), then they will
26806 be listed in this attribute.
26809 @subsubheading Example
26816 -var-update --all-values var1
26817 ^done,changelist=[@{name="var1",value="3",in_scope="true",
26818 type_changed="false"@}]
26822 @subheading The @code{-var-set-frozen} Command
26823 @findex -var-set-frozen
26824 @anchor{-var-set-frozen}
26826 @subsubheading Synopsis
26829 -var-set-frozen @var{name} @var{flag}
26832 Set the frozenness flag on the variable object @var{name}. The
26833 @var{flag} parameter should be either @samp{1} to make the variable
26834 frozen or @samp{0} to make it unfrozen. If a variable object is
26835 frozen, then neither itself, nor any of its children, are
26836 implicitly updated by @code{-var-update} of
26837 a parent variable or by @code{-var-update *}. Only
26838 @code{-var-update} of the variable itself will update its value and
26839 values of its children. After a variable object is unfrozen, it is
26840 implicitly updated by all subsequent @code{-var-update} operations.
26841 Unfreezing a variable does not update it, only subsequent
26842 @code{-var-update} does.
26844 @subsubheading Example
26848 -var-set-frozen V 1
26853 @subheading The @code{-var-set-update-range} command
26854 @findex -var-set-update-range
26855 @anchor{-var-set-update-range}
26857 @subsubheading Synopsis
26860 -var-set-update-range @var{name} @var{from} @var{to}
26863 Set the range of children to be returned by future invocations of
26864 @code{-var-update}.
26866 @var{from} and @var{to} indicate the range of children to report. If
26867 @var{from} or @var{to} is less than zero, the range is reset and all
26868 children will be reported. Otherwise, children starting at @var{from}
26869 (zero-based) and up to and excluding @var{to} will be reported.
26871 @subsubheading Example
26875 -var-set-update-range V 1 2
26879 @subheading The @code{-var-set-visualizer} command
26880 @findex -var-set-visualizer
26881 @anchor{-var-set-visualizer}
26883 @subsubheading Synopsis
26886 -var-set-visualizer @var{name} @var{visualizer}
26889 Set a visualizer for the variable object @var{name}.
26891 @var{visualizer} is the visualizer to use. The special value
26892 @samp{None} means to disable any visualizer in use.
26894 If not @samp{None}, @var{visualizer} must be a Python expression.
26895 This expression must evaluate to a callable object which accepts a
26896 single argument. @value{GDBN} will call this object with the value of
26897 the varobj @var{name} as an argument (this is done so that the same
26898 Python pretty-printing code can be used for both the CLI and MI).
26899 When called, this object must return an object which conforms to the
26900 pretty-printing interface (@pxref{Pretty Printing API}).
26902 The pre-defined function @code{gdb.default_visualizer} may be used to
26903 select a visualizer by following the built-in process
26904 (@pxref{Selecting Pretty-Printers}). This is done automatically when
26905 a varobj is created, and so ordinarily is not needed.
26907 This feature is only available if Python support is enabled. The MI
26908 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
26909 can be used to check this.
26911 @subsubheading Example
26913 Resetting the visualizer:
26917 -var-set-visualizer V None
26921 Reselecting the default (type-based) visualizer:
26925 -var-set-visualizer V gdb.default_visualizer
26929 Suppose @code{SomeClass} is a visualizer class. A lambda expression
26930 can be used to instantiate this class for a varobj:
26934 -var-set-visualizer V "lambda val: SomeClass()"
26938 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26939 @node GDB/MI Data Manipulation
26940 @section @sc{gdb/mi} Data Manipulation
26942 @cindex data manipulation, in @sc{gdb/mi}
26943 @cindex @sc{gdb/mi}, data manipulation
26944 This section describes the @sc{gdb/mi} commands that manipulate data:
26945 examine memory and registers, evaluate expressions, etc.
26947 @c REMOVED FROM THE INTERFACE.
26948 @c @subheading -data-assign
26949 @c Change the value of a program variable. Plenty of side effects.
26950 @c @subsubheading GDB Command
26952 @c @subsubheading Example
26955 @subheading The @code{-data-disassemble} Command
26956 @findex -data-disassemble
26958 @subsubheading Synopsis
26962 [ -s @var{start-addr} -e @var{end-addr} ]
26963 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
26971 @item @var{start-addr}
26972 is the beginning address (or @code{$pc})
26973 @item @var{end-addr}
26975 @item @var{filename}
26976 is the name of the file to disassemble
26977 @item @var{linenum}
26978 is the line number to disassemble around
26980 is the number of disassembly lines to be produced. If it is -1,
26981 the whole function will be disassembled, in case no @var{end-addr} is
26982 specified. If @var{end-addr} is specified as a non-zero value, and
26983 @var{lines} is lower than the number of disassembly lines between
26984 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
26985 displayed; if @var{lines} is higher than the number of lines between
26986 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
26989 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
26993 @subsubheading Result
26995 The output for each instruction is composed of four fields:
27004 Note that whatever included in the instruction field, is not manipulated
27005 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
27007 @subsubheading @value{GDBN} Command
27009 There's no direct mapping from this command to the CLI.
27011 @subsubheading Example
27013 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
27017 -data-disassemble -s $pc -e "$pc + 20" -- 0
27020 @{address="0x000107c0",func-name="main",offset="4",
27021 inst="mov 2, %o0"@},
27022 @{address="0x000107c4",func-name="main",offset="8",
27023 inst="sethi %hi(0x11800), %o2"@},
27024 @{address="0x000107c8",func-name="main",offset="12",
27025 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
27026 @{address="0x000107cc",func-name="main",offset="16",
27027 inst="sethi %hi(0x11800), %o2"@},
27028 @{address="0x000107d0",func-name="main",offset="20",
27029 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
27033 Disassemble the whole @code{main} function. Line 32 is part of
27037 -data-disassemble -f basics.c -l 32 -- 0
27039 @{address="0x000107bc",func-name="main",offset="0",
27040 inst="save %sp, -112, %sp"@},
27041 @{address="0x000107c0",func-name="main",offset="4",
27042 inst="mov 2, %o0"@},
27043 @{address="0x000107c4",func-name="main",offset="8",
27044 inst="sethi %hi(0x11800), %o2"@},
27046 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
27047 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
27051 Disassemble 3 instructions from the start of @code{main}:
27055 -data-disassemble -f basics.c -l 32 -n 3 -- 0
27057 @{address="0x000107bc",func-name="main",offset="0",
27058 inst="save %sp, -112, %sp"@},
27059 @{address="0x000107c0",func-name="main",offset="4",
27060 inst="mov 2, %o0"@},
27061 @{address="0x000107c4",func-name="main",offset="8",
27062 inst="sethi %hi(0x11800), %o2"@}]
27066 Disassemble 3 instructions from the start of @code{main} in mixed mode:
27070 -data-disassemble -f basics.c -l 32 -n 3 -- 1
27072 src_and_asm_line=@{line="31",
27073 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27074 testsuite/gdb.mi/basics.c",line_asm_insn=[
27075 @{address="0x000107bc",func-name="main",offset="0",
27076 inst="save %sp, -112, %sp"@}]@},
27077 src_and_asm_line=@{line="32",
27078 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27079 testsuite/gdb.mi/basics.c",line_asm_insn=[
27080 @{address="0x000107c0",func-name="main",offset="4",
27081 inst="mov 2, %o0"@},
27082 @{address="0x000107c4",func-name="main",offset="8",
27083 inst="sethi %hi(0x11800), %o2"@}]@}]
27088 @subheading The @code{-data-evaluate-expression} Command
27089 @findex -data-evaluate-expression
27091 @subsubheading Synopsis
27094 -data-evaluate-expression @var{expr}
27097 Evaluate @var{expr} as an expression. The expression could contain an
27098 inferior function call. The function call will execute synchronously.
27099 If the expression contains spaces, it must be enclosed in double quotes.
27101 @subsubheading @value{GDBN} Command
27103 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
27104 @samp{call}. In @code{gdbtk} only, there's a corresponding
27105 @samp{gdb_eval} command.
27107 @subsubheading Example
27109 In the following example, the numbers that precede the commands are the
27110 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
27111 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
27115 211-data-evaluate-expression A
27118 311-data-evaluate-expression &A
27119 311^done,value="0xefffeb7c"
27121 411-data-evaluate-expression A+3
27124 511-data-evaluate-expression "A + 3"
27130 @subheading The @code{-data-list-changed-registers} Command
27131 @findex -data-list-changed-registers
27133 @subsubheading Synopsis
27136 -data-list-changed-registers
27139 Display a list of the registers that have changed.
27141 @subsubheading @value{GDBN} Command
27143 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
27144 has the corresponding command @samp{gdb_changed_register_list}.
27146 @subsubheading Example
27148 On a PPC MBX board:
27156 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
27157 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
27160 -data-list-changed-registers
27161 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
27162 "10","11","13","14","15","16","17","18","19","20","21","22","23",
27163 "24","25","26","27","28","30","31","64","65","66","67","69"]
27168 @subheading The @code{-data-list-register-names} Command
27169 @findex -data-list-register-names
27171 @subsubheading Synopsis
27174 -data-list-register-names [ ( @var{regno} )+ ]
27177 Show a list of register names for the current target. If no arguments
27178 are given, it shows a list of the names of all the registers. If
27179 integer numbers are given as arguments, it will print a list of the
27180 names of the registers corresponding to the arguments. To ensure
27181 consistency between a register name and its number, the output list may
27182 include empty register names.
27184 @subsubheading @value{GDBN} Command
27186 @value{GDBN} does not have a command which corresponds to
27187 @samp{-data-list-register-names}. In @code{gdbtk} there is a
27188 corresponding command @samp{gdb_regnames}.
27190 @subsubheading Example
27192 For the PPC MBX board:
27195 -data-list-register-names
27196 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
27197 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
27198 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
27199 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
27200 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
27201 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
27202 "", "pc","ps","cr","lr","ctr","xer"]
27204 -data-list-register-names 1 2 3
27205 ^done,register-names=["r1","r2","r3"]
27209 @subheading The @code{-data-list-register-values} Command
27210 @findex -data-list-register-values
27212 @subsubheading Synopsis
27215 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
27218 Display the registers' contents. @var{fmt} is the format according to
27219 which the registers' contents are to be returned, followed by an optional
27220 list of numbers specifying the registers to display. A missing list of
27221 numbers indicates that the contents of all the registers must be returned.
27223 Allowed formats for @var{fmt} are:
27240 @subsubheading @value{GDBN} Command
27242 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
27243 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
27245 @subsubheading Example
27247 For a PPC MBX board (note: line breaks are for readability only, they
27248 don't appear in the actual output):
27252 -data-list-register-values r 64 65
27253 ^done,register-values=[@{number="64",value="0xfe00a300"@},
27254 @{number="65",value="0x00029002"@}]
27256 -data-list-register-values x
27257 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
27258 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
27259 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
27260 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
27261 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
27262 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
27263 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
27264 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
27265 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
27266 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
27267 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
27268 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
27269 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
27270 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
27271 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
27272 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
27273 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
27274 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
27275 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
27276 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
27277 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
27278 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
27279 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
27280 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
27281 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
27282 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
27283 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
27284 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
27285 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
27286 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
27287 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
27288 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
27289 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
27290 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
27291 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
27292 @{number="69",value="0x20002b03"@}]
27297 @subheading The @code{-data-read-memory} Command
27298 @findex -data-read-memory
27300 @subsubheading Synopsis
27303 -data-read-memory [ -o @var{byte-offset} ]
27304 @var{address} @var{word-format} @var{word-size}
27305 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
27312 @item @var{address}
27313 An expression specifying the address of the first memory word to be
27314 read. Complex expressions containing embedded white space should be
27315 quoted using the C convention.
27317 @item @var{word-format}
27318 The format to be used to print the memory words. The notation is the
27319 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
27322 @item @var{word-size}
27323 The size of each memory word in bytes.
27325 @item @var{nr-rows}
27326 The number of rows in the output table.
27328 @item @var{nr-cols}
27329 The number of columns in the output table.
27332 If present, indicates that each row should include an @sc{ascii} dump. The
27333 value of @var{aschar} is used as a padding character when a byte is not a
27334 member of the printable @sc{ascii} character set (printable @sc{ascii}
27335 characters are those whose code is between 32 and 126, inclusively).
27337 @item @var{byte-offset}
27338 An offset to add to the @var{address} before fetching memory.
27341 This command displays memory contents as a table of @var{nr-rows} by
27342 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
27343 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
27344 (returned as @samp{total-bytes}). Should less than the requested number
27345 of bytes be returned by the target, the missing words are identified
27346 using @samp{N/A}. The number of bytes read from the target is returned
27347 in @samp{nr-bytes} and the starting address used to read memory in
27350 The address of the next/previous row or page is available in
27351 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
27354 @subsubheading @value{GDBN} Command
27356 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
27357 @samp{gdb_get_mem} memory read command.
27359 @subsubheading Example
27361 Read six bytes of memory starting at @code{bytes+6} but then offset by
27362 @code{-6} bytes. Format as three rows of two columns. One byte per
27363 word. Display each word in hex.
27367 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
27368 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
27369 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
27370 prev-page="0x0000138a",memory=[
27371 @{addr="0x00001390",data=["0x00","0x01"]@},
27372 @{addr="0x00001392",data=["0x02","0x03"]@},
27373 @{addr="0x00001394",data=["0x04","0x05"]@}]
27377 Read two bytes of memory starting at address @code{shorts + 64} and
27378 display as a single word formatted in decimal.
27382 5-data-read-memory shorts+64 d 2 1 1
27383 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
27384 next-row="0x00001512",prev-row="0x0000150e",
27385 next-page="0x00001512",prev-page="0x0000150e",memory=[
27386 @{addr="0x00001510",data=["128"]@}]
27390 Read thirty two bytes of memory starting at @code{bytes+16} and format
27391 as eight rows of four columns. Include a string encoding with @samp{x}
27392 used as the non-printable character.
27396 4-data-read-memory bytes+16 x 1 8 4 x
27397 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
27398 next-row="0x000013c0",prev-row="0x0000139c",
27399 next-page="0x000013c0",prev-page="0x00001380",memory=[
27400 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
27401 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
27402 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
27403 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
27404 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
27405 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
27406 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
27407 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
27411 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27412 @node GDB/MI Tracepoint Commands
27413 @section @sc{gdb/mi} Tracepoint Commands
27415 The commands defined in this section implement MI support for
27416 tracepoints. For detailed introduction, see @ref{Tracepoints}.
27418 @subheading The @code{-trace-find} Command
27419 @findex -trace-find
27421 @subsubheading Synopsis
27424 -trace-find @var{mode} [@var{parameters}@dots{}]
27427 Find a trace frame using criteria defined by @var{mode} and
27428 @var{parameters}. The following table lists permissible
27429 modes and their parameters. For details of operation, see @ref{tfind}.
27434 No parameters are required. Stops examining trace frames.
27437 An integer is required as parameter. Selects tracepoint frame with
27440 @item tracepoint-number
27441 An integer is required as parameter. Finds next
27442 trace frame that corresponds to tracepoint with the specified number.
27445 An address is required as parameter. Finds
27446 next trace frame that corresponds to any tracepoint at the specified
27449 @item pc-inside-range
27450 Two addresses are required as parameters. Finds next trace
27451 frame that corresponds to a tracepoint at an address inside the
27452 specified range. Both bounds are considered to be inside the range.
27454 @item pc-outside-range
27455 Two addresses are required as parameters. Finds
27456 next trace frame that corresponds to a tracepoint at an address outside
27457 the specified range. Both bounds are considered to be inside the range.
27460 Line specification is required as parameter. @xref{Specify Location}.
27461 Finds next trace frame that corresponds to a tracepoint at
27462 the specified location.
27466 If @samp{none} was passed as @var{mode}, the response does not
27467 have fields. Otherwise, the response may have the following fields:
27471 This field has either @samp{0} or @samp{1} as the value, depending
27472 on whether a matching tracepoint was found.
27475 The index of the found traceframe. This field is present iff
27476 the @samp{found} field has value of @samp{1}.
27479 The index of the found tracepoint. This field is present iff
27480 the @samp{found} field has value of @samp{1}.
27483 The information about the frame corresponding to the found trace
27484 frame. This field is present only if a trace frame was found.
27485 @xref{GDB/MI Frame Information}, for description of this field.
27489 @subsubheading @value{GDBN} Command
27491 The corresponding @value{GDBN} command is @samp{tfind}.
27493 @subheading -trace-define-variable
27494 @findex -trace-define-variable
27496 @subsubheading Synopsis
27499 -trace-define-variable @var{name} [ @var{value} ]
27502 Create trace variable @var{name} if it does not exist. If
27503 @var{value} is specified, sets the initial value of the specified
27504 trace variable to that value. Note that the @var{name} should start
27505 with the @samp{$} character.
27507 @subsubheading @value{GDBN} Command
27509 The corresponding @value{GDBN} command is @samp{tvariable}.
27511 @subheading -trace-list-variables
27512 @findex -trace-list-variables
27514 @subsubheading Synopsis
27517 -trace-list-variables
27520 Return a table of all defined trace variables. Each element of the
27521 table has the following fields:
27525 The name of the trace variable. This field is always present.
27528 The initial value. This is a 64-bit signed integer. This
27529 field is always present.
27532 The value the trace variable has at the moment. This is a 64-bit
27533 signed integer. This field is absent iff current value is
27534 not defined, for example if the trace was never run, or is
27539 @subsubheading @value{GDBN} Command
27541 The corresponding @value{GDBN} command is @samp{tvariables}.
27543 @subsubheading Example
27547 -trace-list-variables
27548 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
27549 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
27550 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
27551 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
27552 body=[variable=@{name="$trace_timestamp",initial="0"@}
27553 variable=@{name="$foo",initial="10",current="15"@}]@}
27557 @subheading -trace-save
27558 @findex -trace-save
27560 @subsubheading Synopsis
27563 -trace-save [-r ] @var{filename}
27566 Saves the collected trace data to @var{filename}. Without the
27567 @samp{-r} option, the data is downloaded from the target and saved
27568 in a local file. With the @samp{-r} option the target is asked
27569 to perform the save.
27571 @subsubheading @value{GDBN} Command
27573 The corresponding @value{GDBN} command is @samp{tsave}.
27576 @subheading -trace-start
27577 @findex -trace-start
27579 @subsubheading Synopsis
27585 Starts a tracing experiments. The result of this command does not
27588 @subsubheading @value{GDBN} Command
27590 The corresponding @value{GDBN} command is @samp{tstart}.
27592 @subheading -trace-status
27593 @findex -trace-status
27595 @subsubheading Synopsis
27601 Obtains the status of a tracing experiment. The result may include
27602 the following fields:
27607 May have a value of either @samp{0}, when no tracing operations are
27608 supported, @samp{1}, when all tracing operations are supported, or
27609 @samp{file} when examining trace file. In the latter case, examining
27610 of trace frame is possible but new tracing experiement cannot be
27611 started. This field is always present.
27614 May have a value of either @samp{0} or @samp{1} depending on whether
27615 tracing experiement is in progress on target. This field is present
27616 if @samp{supported} field is not @samp{0}.
27619 Report the reason why the tracing was stopped last time. This field
27620 may be absent iff tracing was never stopped on target yet. The
27621 value of @samp{request} means the tracing was stopped as result of
27622 the @code{-trace-stop} command. The value of @samp{overflow} means
27623 the tracing buffer is full. The value of @samp{disconnection} means
27624 tracing was automatically stopped when @value{GDBN} has disconnected.
27625 The value of @samp{passcount} means tracing was stopped when a
27626 tracepoint was passed a maximal number of times for that tracepoint.
27627 This field is present if @samp{supported} field is not @samp{0}.
27629 @item stopping-tracepoint
27630 The number of tracepoint whose passcount as exceeded. This field is
27631 present iff the @samp{stop-reason} field has the value of
27635 @itemx frames-created
27636 The @samp{frames} field is a count of the total number of trace frames
27637 in the trace buffer, while @samp{frames-created} is the total created
27638 during the run, including ones that were discarded, such as when a
27639 circular trace buffer filled up. Both fields are optional.
27643 These fields tell the current size of the tracing buffer and the
27644 remaining space. These fields are optional.
27647 The value of the circular trace buffer flag. @code{1} means that the
27648 trace buffer is circular and old trace frames will be discarded if
27649 necessary to make room, @code{0} means that the trace buffer is linear
27653 The value of the disconnected tracing flag. @code{1} means that
27654 tracing will continue after @value{GDBN} disconnects, @code{0} means
27655 that the trace run will stop.
27659 @subsubheading @value{GDBN} Command
27661 The corresponding @value{GDBN} command is @samp{tstatus}.
27663 @subheading -trace-stop
27664 @findex -trace-stop
27666 @subsubheading Synopsis
27672 Stops a tracing experiment. The result of this command has the same
27673 fields as @code{-trace-status}, except that the @samp{supported} and
27674 @samp{running} fields are not output.
27676 @subsubheading @value{GDBN} Command
27678 The corresponding @value{GDBN} command is @samp{tstop}.
27681 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27682 @node GDB/MI Symbol Query
27683 @section @sc{gdb/mi} Symbol Query Commands
27687 @subheading The @code{-symbol-info-address} Command
27688 @findex -symbol-info-address
27690 @subsubheading Synopsis
27693 -symbol-info-address @var{symbol}
27696 Describe where @var{symbol} is stored.
27698 @subsubheading @value{GDBN} Command
27700 The corresponding @value{GDBN} command is @samp{info address}.
27702 @subsubheading Example
27706 @subheading The @code{-symbol-info-file} Command
27707 @findex -symbol-info-file
27709 @subsubheading Synopsis
27715 Show the file for the symbol.
27717 @subsubheading @value{GDBN} Command
27719 There's no equivalent @value{GDBN} command. @code{gdbtk} has
27720 @samp{gdb_find_file}.
27722 @subsubheading Example
27726 @subheading The @code{-symbol-info-function} Command
27727 @findex -symbol-info-function
27729 @subsubheading Synopsis
27732 -symbol-info-function
27735 Show which function the symbol lives in.
27737 @subsubheading @value{GDBN} Command
27739 @samp{gdb_get_function} in @code{gdbtk}.
27741 @subsubheading Example
27745 @subheading The @code{-symbol-info-line} Command
27746 @findex -symbol-info-line
27748 @subsubheading Synopsis
27754 Show the core addresses of the code for a source line.
27756 @subsubheading @value{GDBN} Command
27758 The corresponding @value{GDBN} command is @samp{info line}.
27759 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
27761 @subsubheading Example
27765 @subheading The @code{-symbol-info-symbol} Command
27766 @findex -symbol-info-symbol
27768 @subsubheading Synopsis
27771 -symbol-info-symbol @var{addr}
27774 Describe what symbol is at location @var{addr}.
27776 @subsubheading @value{GDBN} Command
27778 The corresponding @value{GDBN} command is @samp{info symbol}.
27780 @subsubheading Example
27784 @subheading The @code{-symbol-list-functions} Command
27785 @findex -symbol-list-functions
27787 @subsubheading Synopsis
27790 -symbol-list-functions
27793 List the functions in the executable.
27795 @subsubheading @value{GDBN} Command
27797 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
27798 @samp{gdb_search} in @code{gdbtk}.
27800 @subsubheading Example
27805 @subheading The @code{-symbol-list-lines} Command
27806 @findex -symbol-list-lines
27808 @subsubheading Synopsis
27811 -symbol-list-lines @var{filename}
27814 Print the list of lines that contain code and their associated program
27815 addresses for the given source filename. The entries are sorted in
27816 ascending PC order.
27818 @subsubheading @value{GDBN} Command
27820 There is no corresponding @value{GDBN} command.
27822 @subsubheading Example
27825 -symbol-list-lines basics.c
27826 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
27832 @subheading The @code{-symbol-list-types} Command
27833 @findex -symbol-list-types
27835 @subsubheading Synopsis
27841 List all the type names.
27843 @subsubheading @value{GDBN} Command
27845 The corresponding commands are @samp{info types} in @value{GDBN},
27846 @samp{gdb_search} in @code{gdbtk}.
27848 @subsubheading Example
27852 @subheading The @code{-symbol-list-variables} Command
27853 @findex -symbol-list-variables
27855 @subsubheading Synopsis
27858 -symbol-list-variables
27861 List all the global and static variable names.
27863 @subsubheading @value{GDBN} Command
27865 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
27867 @subsubheading Example
27871 @subheading The @code{-symbol-locate} Command
27872 @findex -symbol-locate
27874 @subsubheading Synopsis
27880 @subsubheading @value{GDBN} Command
27882 @samp{gdb_loc} in @code{gdbtk}.
27884 @subsubheading Example
27888 @subheading The @code{-symbol-type} Command
27889 @findex -symbol-type
27891 @subsubheading Synopsis
27894 -symbol-type @var{variable}
27897 Show type of @var{variable}.
27899 @subsubheading @value{GDBN} Command
27901 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
27902 @samp{gdb_obj_variable}.
27904 @subsubheading Example
27909 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27910 @node GDB/MI File Commands
27911 @section @sc{gdb/mi} File Commands
27913 This section describes the GDB/MI commands to specify executable file names
27914 and to read in and obtain symbol table information.
27916 @subheading The @code{-file-exec-and-symbols} Command
27917 @findex -file-exec-and-symbols
27919 @subsubheading Synopsis
27922 -file-exec-and-symbols @var{file}
27925 Specify the executable file to be debugged. This file is the one from
27926 which the symbol table is also read. If no file is specified, the
27927 command clears the executable and symbol information. If breakpoints
27928 are set when using this command with no arguments, @value{GDBN} will produce
27929 error messages. Otherwise, no output is produced, except a completion
27932 @subsubheading @value{GDBN} Command
27934 The corresponding @value{GDBN} command is @samp{file}.
27936 @subsubheading Example
27940 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27946 @subheading The @code{-file-exec-file} Command
27947 @findex -file-exec-file
27949 @subsubheading Synopsis
27952 -file-exec-file @var{file}
27955 Specify the executable file to be debugged. Unlike
27956 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
27957 from this file. If used without argument, @value{GDBN} clears the information
27958 about the executable file. No output is produced, except a completion
27961 @subsubheading @value{GDBN} Command
27963 The corresponding @value{GDBN} command is @samp{exec-file}.
27965 @subsubheading Example
27969 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27976 @subheading The @code{-file-list-exec-sections} Command
27977 @findex -file-list-exec-sections
27979 @subsubheading Synopsis
27982 -file-list-exec-sections
27985 List the sections of the current executable file.
27987 @subsubheading @value{GDBN} Command
27989 The @value{GDBN} command @samp{info file} shows, among the rest, the same
27990 information as this command. @code{gdbtk} has a corresponding command
27991 @samp{gdb_load_info}.
27993 @subsubheading Example
27998 @subheading The @code{-file-list-exec-source-file} Command
27999 @findex -file-list-exec-source-file
28001 @subsubheading Synopsis
28004 -file-list-exec-source-file
28007 List the line number, the current source file, and the absolute path
28008 to the current source file for the current executable. The macro
28009 information field has a value of @samp{1} or @samp{0} depending on
28010 whether or not the file includes preprocessor macro information.
28012 @subsubheading @value{GDBN} Command
28014 The @value{GDBN} equivalent is @samp{info source}
28016 @subsubheading Example
28020 123-file-list-exec-source-file
28021 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
28026 @subheading The @code{-file-list-exec-source-files} Command
28027 @findex -file-list-exec-source-files
28029 @subsubheading Synopsis
28032 -file-list-exec-source-files
28035 List the source files for the current executable.
28037 It will always output the filename, but only when @value{GDBN} can find
28038 the absolute file name of a source file, will it output the fullname.
28040 @subsubheading @value{GDBN} Command
28042 The @value{GDBN} equivalent is @samp{info sources}.
28043 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
28045 @subsubheading Example
28048 -file-list-exec-source-files
28050 @{file=foo.c,fullname=/home/foo.c@},
28051 @{file=/home/bar.c,fullname=/home/bar.c@},
28052 @{file=gdb_could_not_find_fullpath.c@}]
28057 @subheading The @code{-file-list-shared-libraries} Command
28058 @findex -file-list-shared-libraries
28060 @subsubheading Synopsis
28063 -file-list-shared-libraries
28066 List the shared libraries in the program.
28068 @subsubheading @value{GDBN} Command
28070 The corresponding @value{GDBN} command is @samp{info shared}.
28072 @subsubheading Example
28076 @subheading The @code{-file-list-symbol-files} Command
28077 @findex -file-list-symbol-files
28079 @subsubheading Synopsis
28082 -file-list-symbol-files
28087 @subsubheading @value{GDBN} Command
28089 The corresponding @value{GDBN} command is @samp{info file} (part of it).
28091 @subsubheading Example
28096 @subheading The @code{-file-symbol-file} Command
28097 @findex -file-symbol-file
28099 @subsubheading Synopsis
28102 -file-symbol-file @var{file}
28105 Read symbol table info from the specified @var{file} argument. When
28106 used without arguments, clears @value{GDBN}'s symbol table info. No output is
28107 produced, except for a completion notification.
28109 @subsubheading @value{GDBN} Command
28111 The corresponding @value{GDBN} command is @samp{symbol-file}.
28113 @subsubheading Example
28117 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28123 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28124 @node GDB/MI Memory Overlay Commands
28125 @section @sc{gdb/mi} Memory Overlay Commands
28127 The memory overlay commands are not implemented.
28129 @c @subheading -overlay-auto
28131 @c @subheading -overlay-list-mapping-state
28133 @c @subheading -overlay-list-overlays
28135 @c @subheading -overlay-map
28137 @c @subheading -overlay-off
28139 @c @subheading -overlay-on
28141 @c @subheading -overlay-unmap
28143 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28144 @node GDB/MI Signal Handling Commands
28145 @section @sc{gdb/mi} Signal Handling Commands
28147 Signal handling commands are not implemented.
28149 @c @subheading -signal-handle
28151 @c @subheading -signal-list-handle-actions
28153 @c @subheading -signal-list-signal-types
28157 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28158 @node GDB/MI Target Manipulation
28159 @section @sc{gdb/mi} Target Manipulation Commands
28162 @subheading The @code{-target-attach} Command
28163 @findex -target-attach
28165 @subsubheading Synopsis
28168 -target-attach @var{pid} | @var{gid} | @var{file}
28171 Attach to a process @var{pid} or a file @var{file} outside of
28172 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
28173 group, the id previously returned by
28174 @samp{-list-thread-groups --available} must be used.
28176 @subsubheading @value{GDBN} Command
28178 The corresponding @value{GDBN} command is @samp{attach}.
28180 @subsubheading Example
28184 =thread-created,id="1"
28185 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
28191 @subheading The @code{-target-compare-sections} Command
28192 @findex -target-compare-sections
28194 @subsubheading Synopsis
28197 -target-compare-sections [ @var{section} ]
28200 Compare data of section @var{section} on target to the exec file.
28201 Without the argument, all sections are compared.
28203 @subsubheading @value{GDBN} Command
28205 The @value{GDBN} equivalent is @samp{compare-sections}.
28207 @subsubheading Example
28212 @subheading The @code{-target-detach} Command
28213 @findex -target-detach
28215 @subsubheading Synopsis
28218 -target-detach [ @var{pid} | @var{gid} ]
28221 Detach from the remote target which normally resumes its execution.
28222 If either @var{pid} or @var{gid} is specified, detaches from either
28223 the specified process, or specified thread group. There's no output.
28225 @subsubheading @value{GDBN} Command
28227 The corresponding @value{GDBN} command is @samp{detach}.
28229 @subsubheading Example
28239 @subheading The @code{-target-disconnect} Command
28240 @findex -target-disconnect
28242 @subsubheading Synopsis
28248 Disconnect from the remote target. There's no output and the target is
28249 generally not resumed.
28251 @subsubheading @value{GDBN} Command
28253 The corresponding @value{GDBN} command is @samp{disconnect}.
28255 @subsubheading Example
28265 @subheading The @code{-target-download} Command
28266 @findex -target-download
28268 @subsubheading Synopsis
28274 Loads the executable onto the remote target.
28275 It prints out an update message every half second, which includes the fields:
28279 The name of the section.
28281 The size of what has been sent so far for that section.
28283 The size of the section.
28285 The total size of what was sent so far (the current and the previous sections).
28287 The size of the overall executable to download.
28291 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
28292 @sc{gdb/mi} Output Syntax}).
28294 In addition, it prints the name and size of the sections, as they are
28295 downloaded. These messages include the following fields:
28299 The name of the section.
28301 The size of the section.
28303 The size of the overall executable to download.
28307 At the end, a summary is printed.
28309 @subsubheading @value{GDBN} Command
28311 The corresponding @value{GDBN} command is @samp{load}.
28313 @subsubheading Example
28315 Note: each status message appears on a single line. Here the messages
28316 have been broken down so that they can fit onto a page.
28321 +download,@{section=".text",section-size="6668",total-size="9880"@}
28322 +download,@{section=".text",section-sent="512",section-size="6668",
28323 total-sent="512",total-size="9880"@}
28324 +download,@{section=".text",section-sent="1024",section-size="6668",
28325 total-sent="1024",total-size="9880"@}
28326 +download,@{section=".text",section-sent="1536",section-size="6668",
28327 total-sent="1536",total-size="9880"@}
28328 +download,@{section=".text",section-sent="2048",section-size="6668",
28329 total-sent="2048",total-size="9880"@}
28330 +download,@{section=".text",section-sent="2560",section-size="6668",
28331 total-sent="2560",total-size="9880"@}
28332 +download,@{section=".text",section-sent="3072",section-size="6668",
28333 total-sent="3072",total-size="9880"@}
28334 +download,@{section=".text",section-sent="3584",section-size="6668",
28335 total-sent="3584",total-size="9880"@}
28336 +download,@{section=".text",section-sent="4096",section-size="6668",
28337 total-sent="4096",total-size="9880"@}
28338 +download,@{section=".text",section-sent="4608",section-size="6668",
28339 total-sent="4608",total-size="9880"@}
28340 +download,@{section=".text",section-sent="5120",section-size="6668",
28341 total-sent="5120",total-size="9880"@}
28342 +download,@{section=".text",section-sent="5632",section-size="6668",
28343 total-sent="5632",total-size="9880"@}
28344 +download,@{section=".text",section-sent="6144",section-size="6668",
28345 total-sent="6144",total-size="9880"@}
28346 +download,@{section=".text",section-sent="6656",section-size="6668",
28347 total-sent="6656",total-size="9880"@}
28348 +download,@{section=".init",section-size="28",total-size="9880"@}
28349 +download,@{section=".fini",section-size="28",total-size="9880"@}
28350 +download,@{section=".data",section-size="3156",total-size="9880"@}
28351 +download,@{section=".data",section-sent="512",section-size="3156",
28352 total-sent="7236",total-size="9880"@}
28353 +download,@{section=".data",section-sent="1024",section-size="3156",
28354 total-sent="7748",total-size="9880"@}
28355 +download,@{section=".data",section-sent="1536",section-size="3156",
28356 total-sent="8260",total-size="9880"@}
28357 +download,@{section=".data",section-sent="2048",section-size="3156",
28358 total-sent="8772",total-size="9880"@}
28359 +download,@{section=".data",section-sent="2560",section-size="3156",
28360 total-sent="9284",total-size="9880"@}
28361 +download,@{section=".data",section-sent="3072",section-size="3156",
28362 total-sent="9796",total-size="9880"@}
28363 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
28370 @subheading The @code{-target-exec-status} Command
28371 @findex -target-exec-status
28373 @subsubheading Synopsis
28376 -target-exec-status
28379 Provide information on the state of the target (whether it is running or
28380 not, for instance).
28382 @subsubheading @value{GDBN} Command
28384 There's no equivalent @value{GDBN} command.
28386 @subsubheading Example
28390 @subheading The @code{-target-list-available-targets} Command
28391 @findex -target-list-available-targets
28393 @subsubheading Synopsis
28396 -target-list-available-targets
28399 List the possible targets to connect to.
28401 @subsubheading @value{GDBN} Command
28403 The corresponding @value{GDBN} command is @samp{help target}.
28405 @subsubheading Example
28409 @subheading The @code{-target-list-current-targets} Command
28410 @findex -target-list-current-targets
28412 @subsubheading Synopsis
28415 -target-list-current-targets
28418 Describe the current target.
28420 @subsubheading @value{GDBN} Command
28422 The corresponding information is printed by @samp{info file} (among
28425 @subsubheading Example
28429 @subheading The @code{-target-list-parameters} Command
28430 @findex -target-list-parameters
28432 @subsubheading Synopsis
28435 -target-list-parameters
28441 @subsubheading @value{GDBN} Command
28445 @subsubheading Example
28449 @subheading The @code{-target-select} Command
28450 @findex -target-select
28452 @subsubheading Synopsis
28455 -target-select @var{type} @var{parameters @dots{}}
28458 Connect @value{GDBN} to the remote target. This command takes two args:
28462 The type of target, for instance @samp{remote}, etc.
28463 @item @var{parameters}
28464 Device names, host names and the like. @xref{Target Commands, ,
28465 Commands for Managing Targets}, for more details.
28468 The output is a connection notification, followed by the address at
28469 which the target program is, in the following form:
28472 ^connected,addr="@var{address}",func="@var{function name}",
28473 args=[@var{arg list}]
28476 @subsubheading @value{GDBN} Command
28478 The corresponding @value{GDBN} command is @samp{target}.
28480 @subsubheading Example
28484 -target-select remote /dev/ttya
28485 ^connected,addr="0xfe00a300",func="??",args=[]
28489 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28490 @node GDB/MI File Transfer Commands
28491 @section @sc{gdb/mi} File Transfer Commands
28494 @subheading The @code{-target-file-put} Command
28495 @findex -target-file-put
28497 @subsubheading Synopsis
28500 -target-file-put @var{hostfile} @var{targetfile}
28503 Copy file @var{hostfile} from the host system (the machine running
28504 @value{GDBN}) to @var{targetfile} on the target system.
28506 @subsubheading @value{GDBN} Command
28508 The corresponding @value{GDBN} command is @samp{remote put}.
28510 @subsubheading Example
28514 -target-file-put localfile remotefile
28520 @subheading The @code{-target-file-get} Command
28521 @findex -target-file-get
28523 @subsubheading Synopsis
28526 -target-file-get @var{targetfile} @var{hostfile}
28529 Copy file @var{targetfile} from the target system to @var{hostfile}
28530 on the host system.
28532 @subsubheading @value{GDBN} Command
28534 The corresponding @value{GDBN} command is @samp{remote get}.
28536 @subsubheading Example
28540 -target-file-get remotefile localfile
28546 @subheading The @code{-target-file-delete} Command
28547 @findex -target-file-delete
28549 @subsubheading Synopsis
28552 -target-file-delete @var{targetfile}
28555 Delete @var{targetfile} from the target system.
28557 @subsubheading @value{GDBN} Command
28559 The corresponding @value{GDBN} command is @samp{remote delete}.
28561 @subsubheading Example
28565 -target-file-delete remotefile
28571 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28572 @node GDB/MI Miscellaneous Commands
28573 @section Miscellaneous @sc{gdb/mi} Commands
28575 @c @subheading -gdb-complete
28577 @subheading The @code{-gdb-exit} Command
28580 @subsubheading Synopsis
28586 Exit @value{GDBN} immediately.
28588 @subsubheading @value{GDBN} Command
28590 Approximately corresponds to @samp{quit}.
28592 @subsubheading Example
28602 @subheading The @code{-exec-abort} Command
28603 @findex -exec-abort
28605 @subsubheading Synopsis
28611 Kill the inferior running program.
28613 @subsubheading @value{GDBN} Command
28615 The corresponding @value{GDBN} command is @samp{kill}.
28617 @subsubheading Example
28622 @subheading The @code{-gdb-set} Command
28625 @subsubheading Synopsis
28631 Set an internal @value{GDBN} variable.
28632 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
28634 @subsubheading @value{GDBN} Command
28636 The corresponding @value{GDBN} command is @samp{set}.
28638 @subsubheading Example
28648 @subheading The @code{-gdb-show} Command
28651 @subsubheading Synopsis
28657 Show the current value of a @value{GDBN} variable.
28659 @subsubheading @value{GDBN} Command
28661 The corresponding @value{GDBN} command is @samp{show}.
28663 @subsubheading Example
28672 @c @subheading -gdb-source
28675 @subheading The @code{-gdb-version} Command
28676 @findex -gdb-version
28678 @subsubheading Synopsis
28684 Show version information for @value{GDBN}. Used mostly in testing.
28686 @subsubheading @value{GDBN} Command
28688 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
28689 default shows this information when you start an interactive session.
28691 @subsubheading Example
28693 @c This example modifies the actual output from GDB to avoid overfull
28699 ~Copyright 2000 Free Software Foundation, Inc.
28700 ~GDB is free software, covered by the GNU General Public License, and
28701 ~you are welcome to change it and/or distribute copies of it under
28702 ~ certain conditions.
28703 ~Type "show copying" to see the conditions.
28704 ~There is absolutely no warranty for GDB. Type "show warranty" for
28706 ~This GDB was configured as
28707 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
28712 @subheading The @code{-list-features} Command
28713 @findex -list-features
28715 Returns a list of particular features of the MI protocol that
28716 this version of gdb implements. A feature can be a command,
28717 or a new field in an output of some command, or even an
28718 important bugfix. While a frontend can sometimes detect presence
28719 of a feature at runtime, it is easier to perform detection at debugger
28722 The command returns a list of strings, with each string naming an
28723 available feature. Each returned string is just a name, it does not
28724 have any internal structure. The list of possible feature names
28730 (gdb) -list-features
28731 ^done,result=["feature1","feature2"]
28734 The current list of features is:
28737 @item frozen-varobjs
28738 Indicates presence of the @code{-var-set-frozen} command, as well
28739 as possible presense of the @code{frozen} field in the output
28740 of @code{-varobj-create}.
28741 @item pending-breakpoints
28742 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
28744 Indicates presence of Python scripting support, Python-based
28745 pretty-printing commands, and possible presence of the
28746 @samp{display_hint} field in the output of @code{-var-list-children}
28748 Indicates presence of the @code{-thread-info} command.
28752 @subheading The @code{-list-target-features} Command
28753 @findex -list-target-features
28755 Returns a list of particular features that are supported by the
28756 target. Those features affect the permitted MI commands, but
28757 unlike the features reported by the @code{-list-features} command, the
28758 features depend on which target GDB is using at the moment. Whenever
28759 a target can change, due to commands such as @code{-target-select},
28760 @code{-target-attach} or @code{-exec-run}, the list of target features
28761 may change, and the frontend should obtain it again.
28765 (gdb) -list-features
28766 ^done,result=["async"]
28769 The current list of features is:
28773 Indicates that the target is capable of asynchronous command
28774 execution, which means that @value{GDBN} will accept further commands
28775 while the target is running.
28779 @subheading The @code{-list-thread-groups} Command
28780 @findex -list-thread-groups
28782 @subheading Synopsis
28785 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
28788 Lists thread groups (@pxref{Thread groups}). When a single thread
28789 group is passed as the argument, lists the children of that group.
28790 When several thread group are passed, lists information about those
28791 thread groups. Without any parameters, lists information about all
28792 top-level thread groups.
28794 Normally, thread groups that are being debugged are reported.
28795 With the @samp{--available} option, @value{GDBN} reports thread groups
28796 available on the target.
28798 The output of this command may have either a @samp{threads} result or
28799 a @samp{groups} result. The @samp{thread} result has a list of tuples
28800 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
28801 Information}). The @samp{groups} result has a list of tuples as value,
28802 each tuple describing a thread group. If top-level groups are
28803 requested (that is, no parameter is passed), or when several groups
28804 are passed, the output always has a @samp{groups} result. The format
28805 of the @samp{group} result is described below.
28807 To reduce the number of roundtrips it's possible to list thread groups
28808 together with their children, by passing the @samp{--recurse} option
28809 and the recursion depth. Presently, only recursion depth of 1 is
28810 permitted. If this option is present, then every reported thread group
28811 will also include its children, either as @samp{group} or
28812 @samp{threads} field.
28814 In general, any combination of option and parameters is permitted, with
28815 the following caveats:
28819 When a single thread group is passed, the output will typically
28820 be the @samp{threads} result. Because threads may not contain
28821 anything, the @samp{recurse} option will be ignored.
28824 When the @samp{--available} option is passed, limited information may
28825 be available. In particular, the list of threads of a process might
28826 be inaccessible. Further, specifying specific thread groups might
28827 not give any performance advantage over listing all thread groups.
28828 The frontend should assume that @samp{-list-thread-groups --available}
28829 is always an expensive operation and cache the results.
28833 The @samp{groups} result is a list of tuples, where each tuple may
28834 have the following fields:
28838 Identifier of the thread group. This field is always present.
28839 The identifier is an opaque string; frontends should not try to
28840 convert it to an integer, even though it might look like one.
28843 The type of the thread group. At present, only @samp{process} is a
28847 The target-specific process identifier. This field is only present
28848 for thread groups of type @samp{process} and only if the process exists.
28851 The number of children this thread group has. This field may be
28852 absent for an available thread group.
28855 This field has a list of tuples as value, each tuple describing a
28856 thread. It may be present if the @samp{--recurse} option is
28857 specified, and it's actually possible to obtain the threads.
28860 This field is a list of integers, each identifying a core that one
28861 thread of the group is running on. This field may be absent if
28862 such information is not available.
28865 The name of the executable file that corresponds to this thread group.
28866 The field is only present for thread groups of type @samp{process},
28867 and only if there is a corresponding executable file.
28871 @subheading Example
28875 -list-thread-groups
28876 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
28877 -list-thread-groups 17
28878 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28879 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
28880 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28881 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
28882 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
28883 -list-thread-groups --available
28884 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
28885 -list-thread-groups --available --recurse 1
28886 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28887 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28888 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
28889 -list-thread-groups --available --recurse 1 17 18
28890 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28891 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28892 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
28896 @subheading The @code{-add-inferior} Command
28897 @findex -add-inferior
28899 @subheading Synopsis
28905 Creates a new inferior (@pxref{Inferiors and Programs}). The created
28906 inferior is not associated with any executable. Such association may
28907 be established with the @samp{-file-exec-and-symbols} command
28908 (@pxref{GDB/MI File Commands}). The command response has a single
28909 field, @samp{thread-group}, whose value is the identifier of the
28910 thread group corresponding to the new inferior.
28912 @subheading Example
28917 ^done,thread-group="i3"
28920 @subheading The @code{-interpreter-exec} Command
28921 @findex -interpreter-exec
28923 @subheading Synopsis
28926 -interpreter-exec @var{interpreter} @var{command}
28928 @anchor{-interpreter-exec}
28930 Execute the specified @var{command} in the given @var{interpreter}.
28932 @subheading @value{GDBN} Command
28934 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
28936 @subheading Example
28940 -interpreter-exec console "break main"
28941 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
28942 &"During symbol reading, bad structure-type format.\n"
28943 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
28948 @subheading The @code{-inferior-tty-set} Command
28949 @findex -inferior-tty-set
28951 @subheading Synopsis
28954 -inferior-tty-set /dev/pts/1
28957 Set terminal for future runs of the program being debugged.
28959 @subheading @value{GDBN} Command
28961 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
28963 @subheading Example
28967 -inferior-tty-set /dev/pts/1
28972 @subheading The @code{-inferior-tty-show} Command
28973 @findex -inferior-tty-show
28975 @subheading Synopsis
28981 Show terminal for future runs of program being debugged.
28983 @subheading @value{GDBN} Command
28985 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
28987 @subheading Example
28991 -inferior-tty-set /dev/pts/1
28995 ^done,inferior_tty_terminal="/dev/pts/1"
28999 @subheading The @code{-enable-timings} Command
29000 @findex -enable-timings
29002 @subheading Synopsis
29005 -enable-timings [yes | no]
29008 Toggle the printing of the wallclock, user and system times for an MI
29009 command as a field in its output. This command is to help frontend
29010 developers optimize the performance of their code. No argument is
29011 equivalent to @samp{yes}.
29013 @subheading @value{GDBN} Command
29017 @subheading Example
29025 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29026 addr="0x080484ed",func="main",file="myprog.c",
29027 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
29028 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
29036 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29037 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
29038 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
29039 fullname="/home/nickrob/myprog.c",line="73"@}
29044 @chapter @value{GDBN} Annotations
29046 This chapter describes annotations in @value{GDBN}. Annotations were
29047 designed to interface @value{GDBN} to graphical user interfaces or other
29048 similar programs which want to interact with @value{GDBN} at a
29049 relatively high level.
29051 The annotation mechanism has largely been superseded by @sc{gdb/mi}
29055 This is Edition @value{EDITION}, @value{DATE}.
29059 * Annotations Overview:: What annotations are; the general syntax.
29060 * Server Prefix:: Issuing a command without affecting user state.
29061 * Prompting:: Annotations marking @value{GDBN}'s need for input.
29062 * Errors:: Annotations for error messages.
29063 * Invalidation:: Some annotations describe things now invalid.
29064 * Annotations for Running::
29065 Whether the program is running, how it stopped, etc.
29066 * Source Annotations:: Annotations describing source code.
29069 @node Annotations Overview
29070 @section What is an Annotation?
29071 @cindex annotations
29073 Annotations start with a newline character, two @samp{control-z}
29074 characters, and the name of the annotation. If there is no additional
29075 information associated with this annotation, the name of the annotation
29076 is followed immediately by a newline. If there is additional
29077 information, the name of the annotation is followed by a space, the
29078 additional information, and a newline. The additional information
29079 cannot contain newline characters.
29081 Any output not beginning with a newline and two @samp{control-z}
29082 characters denotes literal output from @value{GDBN}. Currently there is
29083 no need for @value{GDBN} to output a newline followed by two
29084 @samp{control-z} characters, but if there was such a need, the
29085 annotations could be extended with an @samp{escape} annotation which
29086 means those three characters as output.
29088 The annotation @var{level}, which is specified using the
29089 @option{--annotate} command line option (@pxref{Mode Options}), controls
29090 how much information @value{GDBN} prints together with its prompt,
29091 values of expressions, source lines, and other types of output. Level 0
29092 is for no annotations, level 1 is for use when @value{GDBN} is run as a
29093 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
29094 for programs that control @value{GDBN}, and level 2 annotations have
29095 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
29096 Interface, annotate, GDB's Obsolete Annotations}).
29099 @kindex set annotate
29100 @item set annotate @var{level}
29101 The @value{GDBN} command @code{set annotate} sets the level of
29102 annotations to the specified @var{level}.
29104 @item show annotate
29105 @kindex show annotate
29106 Show the current annotation level.
29109 This chapter describes level 3 annotations.
29111 A simple example of starting up @value{GDBN} with annotations is:
29114 $ @kbd{gdb --annotate=3}
29116 Copyright 2003 Free Software Foundation, Inc.
29117 GDB is free software, covered by the GNU General Public License,
29118 and you are welcome to change it and/or distribute copies of it
29119 under certain conditions.
29120 Type "show copying" to see the conditions.
29121 There is absolutely no warranty for GDB. Type "show warranty"
29123 This GDB was configured as "i386-pc-linux-gnu"
29134 Here @samp{quit} is input to @value{GDBN}; the rest is output from
29135 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
29136 denotes a @samp{control-z} character) are annotations; the rest is
29137 output from @value{GDBN}.
29139 @node Server Prefix
29140 @section The Server Prefix
29141 @cindex server prefix
29143 If you prefix a command with @samp{server } then it will not affect
29144 the command history, nor will it affect @value{GDBN}'s notion of which
29145 command to repeat if @key{RET} is pressed on a line by itself. This
29146 means that commands can be run behind a user's back by a front-end in
29147 a transparent manner.
29149 The @code{server } prefix does not affect the recording of values into
29150 the value history; to print a value without recording it into the
29151 value history, use the @code{output} command instead of the
29152 @code{print} command.
29154 Using this prefix also disables confirmation requests
29155 (@pxref{confirmation requests}).
29158 @section Annotation for @value{GDBN} Input
29160 @cindex annotations for prompts
29161 When @value{GDBN} prompts for input, it annotates this fact so it is possible
29162 to know when to send output, when the output from a given command is
29165 Different kinds of input each have a different @dfn{input type}. Each
29166 input type has three annotations: a @code{pre-} annotation, which
29167 denotes the beginning of any prompt which is being output, a plain
29168 annotation, which denotes the end of the prompt, and then a @code{post-}
29169 annotation which denotes the end of any echo which may (or may not) be
29170 associated with the input. For example, the @code{prompt} input type
29171 features the following annotations:
29179 The input types are
29182 @findex pre-prompt annotation
29183 @findex prompt annotation
29184 @findex post-prompt annotation
29186 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
29188 @findex pre-commands annotation
29189 @findex commands annotation
29190 @findex post-commands annotation
29192 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
29193 command. The annotations are repeated for each command which is input.
29195 @findex pre-overload-choice annotation
29196 @findex overload-choice annotation
29197 @findex post-overload-choice annotation
29198 @item overload-choice
29199 When @value{GDBN} wants the user to select between various overloaded functions.
29201 @findex pre-query annotation
29202 @findex query annotation
29203 @findex post-query annotation
29205 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
29207 @findex pre-prompt-for-continue annotation
29208 @findex prompt-for-continue annotation
29209 @findex post-prompt-for-continue annotation
29210 @item prompt-for-continue
29211 When @value{GDBN} is asking the user to press return to continue. Note: Don't
29212 expect this to work well; instead use @code{set height 0} to disable
29213 prompting. This is because the counting of lines is buggy in the
29214 presence of annotations.
29219 @cindex annotations for errors, warnings and interrupts
29221 @findex quit annotation
29226 This annotation occurs right before @value{GDBN} responds to an interrupt.
29228 @findex error annotation
29233 This annotation occurs right before @value{GDBN} responds to an error.
29235 Quit and error annotations indicate that any annotations which @value{GDBN} was
29236 in the middle of may end abruptly. For example, if a
29237 @code{value-history-begin} annotation is followed by a @code{error}, one
29238 cannot expect to receive the matching @code{value-history-end}. One
29239 cannot expect not to receive it either, however; an error annotation
29240 does not necessarily mean that @value{GDBN} is immediately returning all the way
29243 @findex error-begin annotation
29244 A quit or error annotation may be preceded by
29250 Any output between that and the quit or error annotation is the error
29253 Warning messages are not yet annotated.
29254 @c If we want to change that, need to fix warning(), type_error(),
29255 @c range_error(), and possibly other places.
29258 @section Invalidation Notices
29260 @cindex annotations for invalidation messages
29261 The following annotations say that certain pieces of state may have
29265 @findex frames-invalid annotation
29266 @item ^Z^Zframes-invalid
29268 The frames (for example, output from the @code{backtrace} command) may
29271 @findex breakpoints-invalid annotation
29272 @item ^Z^Zbreakpoints-invalid
29274 The breakpoints may have changed. For example, the user just added or
29275 deleted a breakpoint.
29278 @node Annotations for Running
29279 @section Running the Program
29280 @cindex annotations for running programs
29282 @findex starting annotation
29283 @findex stopping annotation
29284 When the program starts executing due to a @value{GDBN} command such as
29285 @code{step} or @code{continue},
29291 is output. When the program stops,
29297 is output. Before the @code{stopped} annotation, a variety of
29298 annotations describe how the program stopped.
29301 @findex exited annotation
29302 @item ^Z^Zexited @var{exit-status}
29303 The program exited, and @var{exit-status} is the exit status (zero for
29304 successful exit, otherwise nonzero).
29306 @findex signalled annotation
29307 @findex signal-name annotation
29308 @findex signal-name-end annotation
29309 @findex signal-string annotation
29310 @findex signal-string-end annotation
29311 @item ^Z^Zsignalled
29312 The program exited with a signal. After the @code{^Z^Zsignalled}, the
29313 annotation continues:
29319 ^Z^Zsignal-name-end
29323 ^Z^Zsignal-string-end
29328 where @var{name} is the name of the signal, such as @code{SIGILL} or
29329 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
29330 as @code{Illegal Instruction} or @code{Segmentation fault}.
29331 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
29332 user's benefit and have no particular format.
29334 @findex signal annotation
29336 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
29337 just saying that the program received the signal, not that it was
29338 terminated with it.
29340 @findex breakpoint annotation
29341 @item ^Z^Zbreakpoint @var{number}
29342 The program hit breakpoint number @var{number}.
29344 @findex watchpoint annotation
29345 @item ^Z^Zwatchpoint @var{number}
29346 The program hit watchpoint number @var{number}.
29349 @node Source Annotations
29350 @section Displaying Source
29351 @cindex annotations for source display
29353 @findex source annotation
29354 The following annotation is used instead of displaying source code:
29357 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
29360 where @var{filename} is an absolute file name indicating which source
29361 file, @var{line} is the line number within that file (where 1 is the
29362 first line in the file), @var{character} is the character position
29363 within the file (where 0 is the first character in the file) (for most
29364 debug formats this will necessarily point to the beginning of a line),
29365 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
29366 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
29367 @var{addr} is the address in the target program associated with the
29368 source which is being displayed. @var{addr} is in the form @samp{0x}
29369 followed by one or more lowercase hex digits (note that this does not
29370 depend on the language).
29372 @node JIT Interface
29373 @chapter JIT Compilation Interface
29374 @cindex just-in-time compilation
29375 @cindex JIT compilation interface
29377 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
29378 interface. A JIT compiler is a program or library that generates native
29379 executable code at runtime and executes it, usually in order to achieve good
29380 performance while maintaining platform independence.
29382 Programs that use JIT compilation are normally difficult to debug because
29383 portions of their code are generated at runtime, instead of being loaded from
29384 object files, which is where @value{GDBN} normally finds the program's symbols
29385 and debug information. In order to debug programs that use JIT compilation,
29386 @value{GDBN} has an interface that allows the program to register in-memory
29387 symbol files with @value{GDBN} at runtime.
29389 If you are using @value{GDBN} to debug a program that uses this interface, then
29390 it should work transparently so long as you have not stripped the binary. If
29391 you are developing a JIT compiler, then the interface is documented in the rest
29392 of this chapter. At this time, the only known client of this interface is the
29395 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
29396 JIT compiler communicates with @value{GDBN} by writing data into a global
29397 variable and calling a fuction at a well-known symbol. When @value{GDBN}
29398 attaches, it reads a linked list of symbol files from the global variable to
29399 find existing code, and puts a breakpoint in the function so that it can find
29400 out about additional code.
29403 * Declarations:: Relevant C struct declarations
29404 * Registering Code:: Steps to register code
29405 * Unregistering Code:: Steps to unregister code
29409 @section JIT Declarations
29411 These are the relevant struct declarations that a C program should include to
29412 implement the interface:
29422 struct jit_code_entry
29424 struct jit_code_entry *next_entry;
29425 struct jit_code_entry *prev_entry;
29426 const char *symfile_addr;
29427 uint64_t symfile_size;
29430 struct jit_descriptor
29433 /* This type should be jit_actions_t, but we use uint32_t
29434 to be explicit about the bitwidth. */
29435 uint32_t action_flag;
29436 struct jit_code_entry *relevant_entry;
29437 struct jit_code_entry *first_entry;
29440 /* GDB puts a breakpoint in this function. */
29441 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
29443 /* Make sure to specify the version statically, because the
29444 debugger may check the version before we can set it. */
29445 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
29448 If the JIT is multi-threaded, then it is important that the JIT synchronize any
29449 modifications to this global data properly, which can easily be done by putting
29450 a global mutex around modifications to these structures.
29452 @node Registering Code
29453 @section Registering Code
29455 To register code with @value{GDBN}, the JIT should follow this protocol:
29459 Generate an object file in memory with symbols and other desired debug
29460 information. The file must include the virtual addresses of the sections.
29463 Create a code entry for the file, which gives the start and size of the symbol
29467 Add it to the linked list in the JIT descriptor.
29470 Point the relevant_entry field of the descriptor at the entry.
29473 Set @code{action_flag} to @code{JIT_REGISTER} and call
29474 @code{__jit_debug_register_code}.
29477 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
29478 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
29479 new code. However, the linked list must still be maintained in order to allow
29480 @value{GDBN} to attach to a running process and still find the symbol files.
29482 @node Unregistering Code
29483 @section Unregistering Code
29485 If code is freed, then the JIT should use the following protocol:
29489 Remove the code entry corresponding to the code from the linked list.
29492 Point the @code{relevant_entry} field of the descriptor at the code entry.
29495 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
29496 @code{__jit_debug_register_code}.
29499 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
29500 and the JIT will leak the memory used for the associated symbol files.
29503 @chapter Reporting Bugs in @value{GDBN}
29504 @cindex bugs in @value{GDBN}
29505 @cindex reporting bugs in @value{GDBN}
29507 Your bug reports play an essential role in making @value{GDBN} reliable.
29509 Reporting a bug may help you by bringing a solution to your problem, or it
29510 may not. But in any case the principal function of a bug report is to help
29511 the entire community by making the next version of @value{GDBN} work better. Bug
29512 reports are your contribution to the maintenance of @value{GDBN}.
29514 In order for a bug report to serve its purpose, you must include the
29515 information that enables us to fix the bug.
29518 * Bug Criteria:: Have you found a bug?
29519 * Bug Reporting:: How to report bugs
29523 @section Have You Found a Bug?
29524 @cindex bug criteria
29526 If you are not sure whether you have found a bug, here are some guidelines:
29529 @cindex fatal signal
29530 @cindex debugger crash
29531 @cindex crash of debugger
29533 If the debugger gets a fatal signal, for any input whatever, that is a
29534 @value{GDBN} bug. Reliable debuggers never crash.
29536 @cindex error on valid input
29538 If @value{GDBN} produces an error message for valid input, that is a
29539 bug. (Note that if you're cross debugging, the problem may also be
29540 somewhere in the connection to the target.)
29542 @cindex invalid input
29544 If @value{GDBN} does not produce an error message for invalid input,
29545 that is a bug. However, you should note that your idea of
29546 ``invalid input'' might be our idea of ``an extension'' or ``support
29547 for traditional practice''.
29550 If you are an experienced user of debugging tools, your suggestions
29551 for improvement of @value{GDBN} are welcome in any case.
29554 @node Bug Reporting
29555 @section How to Report Bugs
29556 @cindex bug reports
29557 @cindex @value{GDBN} bugs, reporting
29559 A number of companies and individuals offer support for @sc{gnu} products.
29560 If you obtained @value{GDBN} from a support organization, we recommend you
29561 contact that organization first.
29563 You can find contact information for many support companies and
29564 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
29566 @c should add a web page ref...
29569 @ifset BUGURL_DEFAULT
29570 In any event, we also recommend that you submit bug reports for
29571 @value{GDBN}. The preferred method is to submit them directly using
29572 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
29573 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
29576 @strong{Do not send bug reports to @samp{info-gdb}, or to
29577 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
29578 not want to receive bug reports. Those that do have arranged to receive
29581 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
29582 serves as a repeater. The mailing list and the newsgroup carry exactly
29583 the same messages. Often people think of posting bug reports to the
29584 newsgroup instead of mailing them. This appears to work, but it has one
29585 problem which can be crucial: a newsgroup posting often lacks a mail
29586 path back to the sender. Thus, if we need to ask for more information,
29587 we may be unable to reach you. For this reason, it is better to send
29588 bug reports to the mailing list.
29590 @ifclear BUGURL_DEFAULT
29591 In any event, we also recommend that you submit bug reports for
29592 @value{GDBN} to @value{BUGURL}.
29596 The fundamental principle of reporting bugs usefully is this:
29597 @strong{report all the facts}. If you are not sure whether to state a
29598 fact or leave it out, state it!
29600 Often people omit facts because they think they know what causes the
29601 problem and assume that some details do not matter. Thus, you might
29602 assume that the name of the variable you use in an example does not matter.
29603 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
29604 stray memory reference which happens to fetch from the location where that
29605 name is stored in memory; perhaps, if the name were different, the contents
29606 of that location would fool the debugger into doing the right thing despite
29607 the bug. Play it safe and give a specific, complete example. That is the
29608 easiest thing for you to do, and the most helpful.
29610 Keep in mind that the purpose of a bug report is to enable us to fix the
29611 bug. It may be that the bug has been reported previously, but neither
29612 you nor we can know that unless your bug report is complete and
29615 Sometimes people give a few sketchy facts and ask, ``Does this ring a
29616 bell?'' Those bug reports are useless, and we urge everyone to
29617 @emph{refuse to respond to them} except to chide the sender to report
29620 To enable us to fix the bug, you should include all these things:
29624 The version of @value{GDBN}. @value{GDBN} announces it if you start
29625 with no arguments; you can also print it at any time using @code{show
29628 Without this, we will not know whether there is any point in looking for
29629 the bug in the current version of @value{GDBN}.
29632 The type of machine you are using, and the operating system name and
29636 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
29637 ``@value{GCC}--2.8.1''.
29640 What compiler (and its version) was used to compile the program you are
29641 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
29642 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
29643 to get this information; for other compilers, see the documentation for
29647 The command arguments you gave the compiler to compile your example and
29648 observe the bug. For example, did you use @samp{-O}? To guarantee
29649 you will not omit something important, list them all. A copy of the
29650 Makefile (or the output from make) is sufficient.
29652 If we were to try to guess the arguments, we would probably guess wrong
29653 and then we might not encounter the bug.
29656 A complete input script, and all necessary source files, that will
29660 A description of what behavior you observe that you believe is
29661 incorrect. For example, ``It gets a fatal signal.''
29663 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
29664 will certainly notice it. But if the bug is incorrect output, we might
29665 not notice unless it is glaringly wrong. You might as well not give us
29666 a chance to make a mistake.
29668 Even if the problem you experience is a fatal signal, you should still
29669 say so explicitly. Suppose something strange is going on, such as, your
29670 copy of @value{GDBN} is out of synch, or you have encountered a bug in
29671 the C library on your system. (This has happened!) Your copy might
29672 crash and ours would not. If you told us to expect a crash, then when
29673 ours fails to crash, we would know that the bug was not happening for
29674 us. If you had not told us to expect a crash, then we would not be able
29675 to draw any conclusion from our observations.
29678 @cindex recording a session script
29679 To collect all this information, you can use a session recording program
29680 such as @command{script}, which is available on many Unix systems.
29681 Just run your @value{GDBN} session inside @command{script} and then
29682 include the @file{typescript} file with your bug report.
29684 Another way to record a @value{GDBN} session is to run @value{GDBN}
29685 inside Emacs and then save the entire buffer to a file.
29688 If you wish to suggest changes to the @value{GDBN} source, send us context
29689 diffs. If you even discuss something in the @value{GDBN} source, refer to
29690 it by context, not by line number.
29692 The line numbers in our development sources will not match those in your
29693 sources. Your line numbers would convey no useful information to us.
29697 Here are some things that are not necessary:
29701 A description of the envelope of the bug.
29703 Often people who encounter a bug spend a lot of time investigating
29704 which changes to the input file will make the bug go away and which
29705 changes will not affect it.
29707 This is often time consuming and not very useful, because the way we
29708 will find the bug is by running a single example under the debugger
29709 with breakpoints, not by pure deduction from a series of examples.
29710 We recommend that you save your time for something else.
29712 Of course, if you can find a simpler example to report @emph{instead}
29713 of the original one, that is a convenience for us. Errors in the
29714 output will be easier to spot, running under the debugger will take
29715 less time, and so on.
29717 However, simplification is not vital; if you do not want to do this,
29718 report the bug anyway and send us the entire test case you used.
29721 A patch for the bug.
29723 A patch for the bug does help us if it is a good one. But do not omit
29724 the necessary information, such as the test case, on the assumption that
29725 a patch is all we need. We might see problems with your patch and decide
29726 to fix the problem another way, or we might not understand it at all.
29728 Sometimes with a program as complicated as @value{GDBN} it is very hard to
29729 construct an example that will make the program follow a certain path
29730 through the code. If you do not send us the example, we will not be able
29731 to construct one, so we will not be able to verify that the bug is fixed.
29733 And if we cannot understand what bug you are trying to fix, or why your
29734 patch should be an improvement, we will not install it. A test case will
29735 help us to understand.
29738 A guess about what the bug is or what it depends on.
29740 Such guesses are usually wrong. Even we cannot guess right about such
29741 things without first using the debugger to find the facts.
29744 @c The readline documentation is distributed with the readline code
29745 @c and consists of the two following files:
29747 @c inc-hist.texinfo
29748 @c Use -I with makeinfo to point to the appropriate directory,
29749 @c environment var TEXINPUTS with TeX.
29750 @include rluser.texi
29751 @include inc-hist.texinfo
29754 @node Formatting Documentation
29755 @appendix Formatting Documentation
29757 @cindex @value{GDBN} reference card
29758 @cindex reference card
29759 The @value{GDBN} 4 release includes an already-formatted reference card, ready
29760 for printing with PostScript or Ghostscript, in the @file{gdb}
29761 subdirectory of the main source directory@footnote{In
29762 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
29763 release.}. If you can use PostScript or Ghostscript with your printer,
29764 you can print the reference card immediately with @file{refcard.ps}.
29766 The release also includes the source for the reference card. You
29767 can format it, using @TeX{}, by typing:
29773 The @value{GDBN} reference card is designed to print in @dfn{landscape}
29774 mode on US ``letter'' size paper;
29775 that is, on a sheet 11 inches wide by 8.5 inches
29776 high. You will need to specify this form of printing as an option to
29777 your @sc{dvi} output program.
29779 @cindex documentation
29781 All the documentation for @value{GDBN} comes as part of the machine-readable
29782 distribution. The documentation is written in Texinfo format, which is
29783 a documentation system that uses a single source file to produce both
29784 on-line information and a printed manual. You can use one of the Info
29785 formatting commands to create the on-line version of the documentation
29786 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
29788 @value{GDBN} includes an already formatted copy of the on-line Info
29789 version of this manual in the @file{gdb} subdirectory. The main Info
29790 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
29791 subordinate files matching @samp{gdb.info*} in the same directory. If
29792 necessary, you can print out these files, or read them with any editor;
29793 but they are easier to read using the @code{info} subsystem in @sc{gnu}
29794 Emacs or the standalone @code{info} program, available as part of the
29795 @sc{gnu} Texinfo distribution.
29797 If you want to format these Info files yourself, you need one of the
29798 Info formatting programs, such as @code{texinfo-format-buffer} or
29801 If you have @code{makeinfo} installed, and are in the top level
29802 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
29803 version @value{GDBVN}), you can make the Info file by typing:
29810 If you want to typeset and print copies of this manual, you need @TeX{},
29811 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
29812 Texinfo definitions file.
29814 @TeX{} is a typesetting program; it does not print files directly, but
29815 produces output files called @sc{dvi} files. To print a typeset
29816 document, you need a program to print @sc{dvi} files. If your system
29817 has @TeX{} installed, chances are it has such a program. The precise
29818 command to use depends on your system; @kbd{lpr -d} is common; another
29819 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
29820 require a file name without any extension or a @samp{.dvi} extension.
29822 @TeX{} also requires a macro definitions file called
29823 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
29824 written in Texinfo format. On its own, @TeX{} cannot either read or
29825 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
29826 and is located in the @file{gdb-@var{version-number}/texinfo}
29829 If you have @TeX{} and a @sc{dvi} printer program installed, you can
29830 typeset and print this manual. First switch to the @file{gdb}
29831 subdirectory of the main source directory (for example, to
29832 @file{gdb-@value{GDBVN}/gdb}) and type:
29838 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
29840 @node Installing GDB
29841 @appendix Installing @value{GDBN}
29842 @cindex installation
29845 * Requirements:: Requirements for building @value{GDBN}
29846 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
29847 * Separate Objdir:: Compiling @value{GDBN} in another directory
29848 * Config Names:: Specifying names for hosts and targets
29849 * Configure Options:: Summary of options for configure
29850 * System-wide configuration:: Having a system-wide init file
29854 @section Requirements for Building @value{GDBN}
29855 @cindex building @value{GDBN}, requirements for
29857 Building @value{GDBN} requires various tools and packages to be available.
29858 Other packages will be used only if they are found.
29860 @heading Tools/Packages Necessary for Building @value{GDBN}
29862 @item ISO C90 compiler
29863 @value{GDBN} is written in ISO C90. It should be buildable with any
29864 working C90 compiler, e.g.@: GCC.
29868 @heading Tools/Packages Optional for Building @value{GDBN}
29872 @value{GDBN} can use the Expat XML parsing library. This library may be
29873 included with your operating system distribution; if it is not, you
29874 can get the latest version from @url{http://expat.sourceforge.net}.
29875 The @file{configure} script will search for this library in several
29876 standard locations; if it is installed in an unusual path, you can
29877 use the @option{--with-libexpat-prefix} option to specify its location.
29883 Remote protocol memory maps (@pxref{Memory Map Format})
29885 Target descriptions (@pxref{Target Descriptions})
29887 Remote shared library lists (@pxref{Library List Format})
29889 MS-Windows shared libraries (@pxref{Shared Libraries})
29893 @cindex compressed debug sections
29894 @value{GDBN} will use the @samp{zlib} library, if available, to read
29895 compressed debug sections. Some linkers, such as GNU gold, are capable
29896 of producing binaries with compressed debug sections. If @value{GDBN}
29897 is compiled with @samp{zlib}, it will be able to read the debug
29898 information in such binaries.
29900 The @samp{zlib} library is likely included with your operating system
29901 distribution; if it is not, you can get the latest version from
29902 @url{http://zlib.net}.
29905 @value{GDBN}'s features related to character sets (@pxref{Character
29906 Sets}) require a functioning @code{iconv} implementation. If you are
29907 on a GNU system, then this is provided by the GNU C Library. Some
29908 other systems also provide a working @code{iconv}.
29910 On systems with @code{iconv}, you can install GNU Libiconv. If you
29911 have previously installed Libiconv, you can use the
29912 @option{--with-libiconv-prefix} option to configure.
29914 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
29915 arrange to build Libiconv if a directory named @file{libiconv} appears
29916 in the top-most source directory. If Libiconv is built this way, and
29917 if the operating system does not provide a suitable @code{iconv}
29918 implementation, then the just-built library will automatically be used
29919 by @value{GDBN}. One easy way to set this up is to download GNU
29920 Libiconv, unpack it, and then rename the directory holding the
29921 Libiconv source code to @samp{libiconv}.
29924 @node Running Configure
29925 @section Invoking the @value{GDBN} @file{configure} Script
29926 @cindex configuring @value{GDBN}
29927 @value{GDBN} comes with a @file{configure} script that automates the process
29928 of preparing @value{GDBN} for installation; you can then use @code{make} to
29929 build the @code{gdb} program.
29931 @c irrelevant in info file; it's as current as the code it lives with.
29932 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
29933 look at the @file{README} file in the sources; we may have improved the
29934 installation procedures since publishing this manual.}
29937 The @value{GDBN} distribution includes all the source code you need for
29938 @value{GDBN} in a single directory, whose name is usually composed by
29939 appending the version number to @samp{gdb}.
29941 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
29942 @file{gdb-@value{GDBVN}} directory. That directory contains:
29945 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
29946 script for configuring @value{GDBN} and all its supporting libraries
29948 @item gdb-@value{GDBVN}/gdb
29949 the source specific to @value{GDBN} itself
29951 @item gdb-@value{GDBVN}/bfd
29952 source for the Binary File Descriptor library
29954 @item gdb-@value{GDBVN}/include
29955 @sc{gnu} include files
29957 @item gdb-@value{GDBVN}/libiberty
29958 source for the @samp{-liberty} free software library
29960 @item gdb-@value{GDBVN}/opcodes
29961 source for the library of opcode tables and disassemblers
29963 @item gdb-@value{GDBVN}/readline
29964 source for the @sc{gnu} command-line interface
29966 @item gdb-@value{GDBVN}/glob
29967 source for the @sc{gnu} filename pattern-matching subroutine
29969 @item gdb-@value{GDBVN}/mmalloc
29970 source for the @sc{gnu} memory-mapped malloc package
29973 The simplest way to configure and build @value{GDBN} is to run @file{configure}
29974 from the @file{gdb-@var{version-number}} source directory, which in
29975 this example is the @file{gdb-@value{GDBVN}} directory.
29977 First switch to the @file{gdb-@var{version-number}} source directory
29978 if you are not already in it; then run @file{configure}. Pass the
29979 identifier for the platform on which @value{GDBN} will run as an
29985 cd gdb-@value{GDBVN}
29986 ./configure @var{host}
29991 where @var{host} is an identifier such as @samp{sun4} or
29992 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
29993 (You can often leave off @var{host}; @file{configure} tries to guess the
29994 correct value by examining your system.)
29996 Running @samp{configure @var{host}} and then running @code{make} builds the
29997 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
29998 libraries, then @code{gdb} itself. The configured source files, and the
29999 binaries, are left in the corresponding source directories.
30002 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
30003 system does not recognize this automatically when you run a different
30004 shell, you may need to run @code{sh} on it explicitly:
30007 sh configure @var{host}
30010 If you run @file{configure} from a directory that contains source
30011 directories for multiple libraries or programs, such as the
30012 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
30014 creates configuration files for every directory level underneath (unless
30015 you tell it not to, with the @samp{--norecursion} option).
30017 You should run the @file{configure} script from the top directory in the
30018 source tree, the @file{gdb-@var{version-number}} directory. If you run
30019 @file{configure} from one of the subdirectories, you will configure only
30020 that subdirectory. That is usually not what you want. In particular,
30021 if you run the first @file{configure} from the @file{gdb} subdirectory
30022 of the @file{gdb-@var{version-number}} directory, you will omit the
30023 configuration of @file{bfd}, @file{readline}, and other sibling
30024 directories of the @file{gdb} subdirectory. This leads to build errors
30025 about missing include files such as @file{bfd/bfd.h}.
30027 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
30028 However, you should make sure that the shell on your path (named by
30029 the @samp{SHELL} environment variable) is publicly readable. Remember
30030 that @value{GDBN} uses the shell to start your program---some systems refuse to
30031 let @value{GDBN} debug child processes whose programs are not readable.
30033 @node Separate Objdir
30034 @section Compiling @value{GDBN} in Another Directory
30036 If you want to run @value{GDBN} versions for several host or target machines,
30037 you need a different @code{gdb} compiled for each combination of
30038 host and target. @file{configure} is designed to make this easy by
30039 allowing you to generate each configuration in a separate subdirectory,
30040 rather than in the source directory. If your @code{make} program
30041 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
30042 @code{make} in each of these directories builds the @code{gdb}
30043 program specified there.
30045 To build @code{gdb} in a separate directory, run @file{configure}
30046 with the @samp{--srcdir} option to specify where to find the source.
30047 (You also need to specify a path to find @file{configure}
30048 itself from your working directory. If the path to @file{configure}
30049 would be the same as the argument to @samp{--srcdir}, you can leave out
30050 the @samp{--srcdir} option; it is assumed.)
30052 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
30053 separate directory for a Sun 4 like this:
30057 cd gdb-@value{GDBVN}
30060 ../gdb-@value{GDBVN}/configure sun4
30065 When @file{configure} builds a configuration using a remote source
30066 directory, it creates a tree for the binaries with the same structure
30067 (and using the same names) as the tree under the source directory. In
30068 the example, you'd find the Sun 4 library @file{libiberty.a} in the
30069 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
30070 @file{gdb-sun4/gdb}.
30072 Make sure that your path to the @file{configure} script has just one
30073 instance of @file{gdb} in it. If your path to @file{configure} looks
30074 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
30075 one subdirectory of @value{GDBN}, not the whole package. This leads to
30076 build errors about missing include files such as @file{bfd/bfd.h}.
30078 One popular reason to build several @value{GDBN} configurations in separate
30079 directories is to configure @value{GDBN} for cross-compiling (where
30080 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
30081 programs that run on another machine---the @dfn{target}).
30082 You specify a cross-debugging target by
30083 giving the @samp{--target=@var{target}} option to @file{configure}.
30085 When you run @code{make} to build a program or library, you must run
30086 it in a configured directory---whatever directory you were in when you
30087 called @file{configure} (or one of its subdirectories).
30089 The @code{Makefile} that @file{configure} generates in each source
30090 directory also runs recursively. If you type @code{make} in a source
30091 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
30092 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
30093 will build all the required libraries, and then build GDB.
30095 When you have multiple hosts or targets configured in separate
30096 directories, you can run @code{make} on them in parallel (for example,
30097 if they are NFS-mounted on each of the hosts); they will not interfere
30101 @section Specifying Names for Hosts and Targets
30103 The specifications used for hosts and targets in the @file{configure}
30104 script are based on a three-part naming scheme, but some short predefined
30105 aliases are also supported. The full naming scheme encodes three pieces
30106 of information in the following pattern:
30109 @var{architecture}-@var{vendor}-@var{os}
30112 For example, you can use the alias @code{sun4} as a @var{host} argument,
30113 or as the value for @var{target} in a @code{--target=@var{target}}
30114 option. The equivalent full name is @samp{sparc-sun-sunos4}.
30116 The @file{configure} script accompanying @value{GDBN} does not provide
30117 any query facility to list all supported host and target names or
30118 aliases. @file{configure} calls the Bourne shell script
30119 @code{config.sub} to map abbreviations to full names; you can read the
30120 script, if you wish, or you can use it to test your guesses on
30121 abbreviations---for example:
30124 % sh config.sub i386-linux
30126 % sh config.sub alpha-linux
30127 alpha-unknown-linux-gnu
30128 % sh config.sub hp9k700
30130 % sh config.sub sun4
30131 sparc-sun-sunos4.1.1
30132 % sh config.sub sun3
30133 m68k-sun-sunos4.1.1
30134 % sh config.sub i986v
30135 Invalid configuration `i986v': machine `i986v' not recognized
30139 @code{config.sub} is also distributed in the @value{GDBN} source
30140 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
30142 @node Configure Options
30143 @section @file{configure} Options
30145 Here is a summary of the @file{configure} options and arguments that
30146 are most often useful for building @value{GDBN}. @file{configure} also has
30147 several other options not listed here. @inforef{What Configure
30148 Does,,configure.info}, for a full explanation of @file{configure}.
30151 configure @r{[}--help@r{]}
30152 @r{[}--prefix=@var{dir}@r{]}
30153 @r{[}--exec-prefix=@var{dir}@r{]}
30154 @r{[}--srcdir=@var{dirname}@r{]}
30155 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
30156 @r{[}--target=@var{target}@r{]}
30161 You may introduce options with a single @samp{-} rather than
30162 @samp{--} if you prefer; but you may abbreviate option names if you use
30167 Display a quick summary of how to invoke @file{configure}.
30169 @item --prefix=@var{dir}
30170 Configure the source to install programs and files under directory
30173 @item --exec-prefix=@var{dir}
30174 Configure the source to install programs under directory
30177 @c avoid splitting the warning from the explanation:
30179 @item --srcdir=@var{dirname}
30180 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
30181 @code{make} that implements the @code{VPATH} feature.}@*
30182 Use this option to make configurations in directories separate from the
30183 @value{GDBN} source directories. Among other things, you can use this to
30184 build (or maintain) several configurations simultaneously, in separate
30185 directories. @file{configure} writes configuration-specific files in
30186 the current directory, but arranges for them to use the source in the
30187 directory @var{dirname}. @file{configure} creates directories under
30188 the working directory in parallel to the source directories below
30191 @item --norecursion
30192 Configure only the directory level where @file{configure} is executed; do not
30193 propagate configuration to subdirectories.
30195 @item --target=@var{target}
30196 Configure @value{GDBN} for cross-debugging programs running on the specified
30197 @var{target}. Without this option, @value{GDBN} is configured to debug
30198 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
30200 There is no convenient way to generate a list of all available targets.
30202 @item @var{host} @dots{}
30203 Configure @value{GDBN} to run on the specified @var{host}.
30205 There is no convenient way to generate a list of all available hosts.
30208 There are many other options available as well, but they are generally
30209 needed for special purposes only.
30211 @node System-wide configuration
30212 @section System-wide configuration and settings
30213 @cindex system-wide init file
30215 @value{GDBN} can be configured to have a system-wide init file;
30216 this file will be read and executed at startup (@pxref{Startup, , What
30217 @value{GDBN} does during startup}).
30219 Here is the corresponding configure option:
30222 @item --with-system-gdbinit=@var{file}
30223 Specify that the default location of the system-wide init file is
30227 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
30228 it may be subject to relocation. Two possible cases:
30232 If the default location of this init file contains @file{$prefix},
30233 it will be subject to relocation. Suppose that the configure options
30234 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
30235 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
30236 init file is looked for as @file{$install/etc/gdbinit} instead of
30237 @file{$prefix/etc/gdbinit}.
30240 By contrast, if the default location does not contain the prefix,
30241 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
30242 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
30243 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
30244 wherever @value{GDBN} is installed.
30247 @node Maintenance Commands
30248 @appendix Maintenance Commands
30249 @cindex maintenance commands
30250 @cindex internal commands
30252 In addition to commands intended for @value{GDBN} users, @value{GDBN}
30253 includes a number of commands intended for @value{GDBN} developers,
30254 that are not documented elsewhere in this manual. These commands are
30255 provided here for reference. (For commands that turn on debugging
30256 messages, see @ref{Debugging Output}.)
30259 @kindex maint agent
30260 @kindex maint agent-eval
30261 @item maint agent @var{expression}
30262 @itemx maint agent-eval @var{expression}
30263 Translate the given @var{expression} into remote agent bytecodes.
30264 This command is useful for debugging the Agent Expression mechanism
30265 (@pxref{Agent Expressions}). The @samp{agent} version produces an
30266 expression useful for data collection, such as by tracepoints, while
30267 @samp{maint agent-eval} produces an expression that evaluates directly
30268 to a result. For instance, a collection expression for @code{globa +
30269 globb} will include bytecodes to record four bytes of memory at each
30270 of the addresses of @code{globa} and @code{globb}, while discarding
30271 the result of the addition, while an evaluation expression will do the
30272 addition and return the sum.
30274 @kindex maint info breakpoints
30275 @item @anchor{maint info breakpoints}maint info breakpoints
30276 Using the same format as @samp{info breakpoints}, display both the
30277 breakpoints you've set explicitly, and those @value{GDBN} is using for
30278 internal purposes. Internal breakpoints are shown with negative
30279 breakpoint numbers. The type column identifies what kind of breakpoint
30284 Normal, explicitly set breakpoint.
30287 Normal, explicitly set watchpoint.
30290 Internal breakpoint, used to handle correctly stepping through
30291 @code{longjmp} calls.
30293 @item longjmp resume
30294 Internal breakpoint at the target of a @code{longjmp}.
30297 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
30300 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
30303 Shared library events.
30307 @kindex set displaced-stepping
30308 @kindex show displaced-stepping
30309 @cindex displaced stepping support
30310 @cindex out-of-line single-stepping
30311 @item set displaced-stepping
30312 @itemx show displaced-stepping
30313 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
30314 if the target supports it. Displaced stepping is a way to single-step
30315 over breakpoints without removing them from the inferior, by executing
30316 an out-of-line copy of the instruction that was originally at the
30317 breakpoint location. It is also known as out-of-line single-stepping.
30320 @item set displaced-stepping on
30321 If the target architecture supports it, @value{GDBN} will use
30322 displaced stepping to step over breakpoints.
30324 @item set displaced-stepping off
30325 @value{GDBN} will not use displaced stepping to step over breakpoints,
30326 even if such is supported by the target architecture.
30328 @cindex non-stop mode, and @samp{set displaced-stepping}
30329 @item set displaced-stepping auto
30330 This is the default mode. @value{GDBN} will use displaced stepping
30331 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
30332 architecture supports displaced stepping.
30335 @kindex maint check-symtabs
30336 @item maint check-symtabs
30337 Check the consistency of psymtabs and symtabs.
30339 @kindex maint cplus first_component
30340 @item maint cplus first_component @var{name}
30341 Print the first C@t{++} class/namespace component of @var{name}.
30343 @kindex maint cplus namespace
30344 @item maint cplus namespace
30345 Print the list of possible C@t{++} namespaces.
30347 @kindex maint demangle
30348 @item maint demangle @var{name}
30349 Demangle a C@t{++} or Objective-C mangled @var{name}.
30351 @kindex maint deprecate
30352 @kindex maint undeprecate
30353 @cindex deprecated commands
30354 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
30355 @itemx maint undeprecate @var{command}
30356 Deprecate or undeprecate the named @var{command}. Deprecated commands
30357 cause @value{GDBN} to issue a warning when you use them. The optional
30358 argument @var{replacement} says which newer command should be used in
30359 favor of the deprecated one; if it is given, @value{GDBN} will mention
30360 the replacement as part of the warning.
30362 @kindex maint dump-me
30363 @item maint dump-me
30364 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
30365 Cause a fatal signal in the debugger and force it to dump its core.
30366 This is supported only on systems which support aborting a program
30367 with the @code{SIGQUIT} signal.
30369 @kindex maint internal-error
30370 @kindex maint internal-warning
30371 @item maint internal-error @r{[}@var{message-text}@r{]}
30372 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
30373 Cause @value{GDBN} to call the internal function @code{internal_error}
30374 or @code{internal_warning} and hence behave as though an internal error
30375 or internal warning has been detected. In addition to reporting the
30376 internal problem, these functions give the user the opportunity to
30377 either quit @value{GDBN} or create a core file of the current
30378 @value{GDBN} session.
30380 These commands take an optional parameter @var{message-text} that is
30381 used as the text of the error or warning message.
30383 Here's an example of using @code{internal-error}:
30386 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
30387 @dots{}/maint.c:121: internal-error: testing, 1, 2
30388 A problem internal to GDB has been detected. Further
30389 debugging may prove unreliable.
30390 Quit this debugging session? (y or n) @kbd{n}
30391 Create a core file? (y or n) @kbd{n}
30395 @cindex @value{GDBN} internal error
30396 @cindex internal errors, control of @value{GDBN} behavior
30398 @kindex maint set internal-error
30399 @kindex maint show internal-error
30400 @kindex maint set internal-warning
30401 @kindex maint show internal-warning
30402 @item maint set internal-error @var{action} [ask|yes|no]
30403 @itemx maint show internal-error @var{action}
30404 @itemx maint set internal-warning @var{action} [ask|yes|no]
30405 @itemx maint show internal-warning @var{action}
30406 When @value{GDBN} reports an internal problem (error or warning) it
30407 gives the user the opportunity to both quit @value{GDBN} and create a
30408 core file of the current @value{GDBN} session. These commands let you
30409 override the default behaviour for each particular @var{action},
30410 described in the table below.
30414 You can specify that @value{GDBN} should always (yes) or never (no)
30415 quit. The default is to ask the user what to do.
30418 You can specify that @value{GDBN} should always (yes) or never (no)
30419 create a core file. The default is to ask the user what to do.
30422 @kindex maint packet
30423 @item maint packet @var{text}
30424 If @value{GDBN} is talking to an inferior via the serial protocol,
30425 then this command sends the string @var{text} to the inferior, and
30426 displays the response packet. @value{GDBN} supplies the initial
30427 @samp{$} character, the terminating @samp{#} character, and the
30430 @kindex maint print architecture
30431 @item maint print architecture @r{[}@var{file}@r{]}
30432 Print the entire architecture configuration. The optional argument
30433 @var{file} names the file where the output goes.
30435 @kindex maint print c-tdesc
30436 @item maint print c-tdesc
30437 Print the current target description (@pxref{Target Descriptions}) as
30438 a C source file. The created source file can be used in @value{GDBN}
30439 when an XML parser is not available to parse the description.
30441 @kindex maint print dummy-frames
30442 @item maint print dummy-frames
30443 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
30446 (@value{GDBP}) @kbd{b add}
30448 (@value{GDBP}) @kbd{print add(2,3)}
30449 Breakpoint 2, add (a=2, b=3) at @dots{}
30451 The program being debugged stopped while in a function called from GDB.
30453 (@value{GDBP}) @kbd{maint print dummy-frames}
30454 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
30455 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
30456 call_lo=0x01014000 call_hi=0x01014001
30460 Takes an optional file parameter.
30462 @kindex maint print registers
30463 @kindex maint print raw-registers
30464 @kindex maint print cooked-registers
30465 @kindex maint print register-groups
30466 @item maint print registers @r{[}@var{file}@r{]}
30467 @itemx maint print raw-registers @r{[}@var{file}@r{]}
30468 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
30469 @itemx maint print register-groups @r{[}@var{file}@r{]}
30470 Print @value{GDBN}'s internal register data structures.
30472 The command @code{maint print raw-registers} includes the contents of
30473 the raw register cache; the command @code{maint print cooked-registers}
30474 includes the (cooked) value of all registers, including registers which
30475 aren't available on the target nor visible to user; and the
30476 command @code{maint print register-groups} includes the groups that each
30477 register is a member of. @xref{Registers,, Registers, gdbint,
30478 @value{GDBN} Internals}.
30480 These commands take an optional parameter, a file name to which to
30481 write the information.
30483 @kindex maint print reggroups
30484 @item maint print reggroups @r{[}@var{file}@r{]}
30485 Print @value{GDBN}'s internal register group data structures. The
30486 optional argument @var{file} tells to what file to write the
30489 The register groups info looks like this:
30492 (@value{GDBP}) @kbd{maint print reggroups}
30505 This command forces @value{GDBN} to flush its internal register cache.
30507 @kindex maint print objfiles
30508 @cindex info for known object files
30509 @item maint print objfiles
30510 Print a dump of all known object files. For each object file, this
30511 command prints its name, address in memory, and all of its psymtabs
30514 @kindex maint print section-scripts
30515 @cindex info for known .debug_gdb_scripts-loaded scripts
30516 @item maint print section-scripts [@var{regexp}]
30517 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
30518 If @var{regexp} is specified, only print scripts loaded by object files
30519 matching @var{regexp}.
30520 For each script, this command prints its name as specified in the objfile,
30521 and the full path if known.
30522 @xref{.debug_gdb_scripts section}.
30524 @kindex maint print statistics
30525 @cindex bcache statistics
30526 @item maint print statistics
30527 This command prints, for each object file in the program, various data
30528 about that object file followed by the byte cache (@dfn{bcache})
30529 statistics for the object file. The objfile data includes the number
30530 of minimal, partial, full, and stabs symbols, the number of types
30531 defined by the objfile, the number of as yet unexpanded psym tables,
30532 the number of line tables and string tables, and the amount of memory
30533 used by the various tables. The bcache statistics include the counts,
30534 sizes, and counts of duplicates of all and unique objects, max,
30535 average, and median entry size, total memory used and its overhead and
30536 savings, and various measures of the hash table size and chain
30539 @kindex maint print target-stack
30540 @cindex target stack description
30541 @item maint print target-stack
30542 A @dfn{target} is an interface between the debugger and a particular
30543 kind of file or process. Targets can be stacked in @dfn{strata},
30544 so that more than one target can potentially respond to a request.
30545 In particular, memory accesses will walk down the stack of targets
30546 until they find a target that is interested in handling that particular
30549 This command prints a short description of each layer that was pushed on
30550 the @dfn{target stack}, starting from the top layer down to the bottom one.
30552 @kindex maint print type
30553 @cindex type chain of a data type
30554 @item maint print type @var{expr}
30555 Print the type chain for a type specified by @var{expr}. The argument
30556 can be either a type name or a symbol. If it is a symbol, the type of
30557 that symbol is described. The type chain produced by this command is
30558 a recursive definition of the data type as stored in @value{GDBN}'s
30559 data structures, including its flags and contained types.
30561 @kindex maint set dwarf2 always-disassemble
30562 @kindex maint show dwarf2 always-disassemble
30563 @item maint set dwarf2 always-disassemble
30564 @item maint show dwarf2 always-disassemble
30565 Control the behavior of @code{info address} when using DWARF debugging
30568 The default is @code{off}, which means that @value{GDBN} should try to
30569 describe a variable's location in an easily readable format. When
30570 @code{on}, @value{GDBN} will instead display the DWARF location
30571 expression in an assembly-like format. Note that some locations are
30572 too complex for @value{GDBN} to describe simply; in this case you will
30573 always see the disassembly form.
30575 Here is an example of the resulting disassembly:
30578 (gdb) info addr argc
30579 Symbol "argc" is a complex DWARF expression:
30583 For more information on these expressions, see
30584 @uref{http://www.dwarfstd.org/, the DWARF standard}.
30586 @kindex maint set dwarf2 max-cache-age
30587 @kindex maint show dwarf2 max-cache-age
30588 @item maint set dwarf2 max-cache-age
30589 @itemx maint show dwarf2 max-cache-age
30590 Control the DWARF 2 compilation unit cache.
30592 @cindex DWARF 2 compilation units cache
30593 In object files with inter-compilation-unit references, such as those
30594 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
30595 reader needs to frequently refer to previously read compilation units.
30596 This setting controls how long a compilation unit will remain in the
30597 cache if it is not referenced. A higher limit means that cached
30598 compilation units will be stored in memory longer, and more total
30599 memory will be used. Setting it to zero disables caching, which will
30600 slow down @value{GDBN} startup, but reduce memory consumption.
30602 @kindex maint set profile
30603 @kindex maint show profile
30604 @cindex profiling GDB
30605 @item maint set profile
30606 @itemx maint show profile
30607 Control profiling of @value{GDBN}.
30609 Profiling will be disabled until you use the @samp{maint set profile}
30610 command to enable it. When you enable profiling, the system will begin
30611 collecting timing and execution count data; when you disable profiling or
30612 exit @value{GDBN}, the results will be written to a log file. Remember that
30613 if you use profiling, @value{GDBN} will overwrite the profiling log file
30614 (often called @file{gmon.out}). If you have a record of important profiling
30615 data in a @file{gmon.out} file, be sure to move it to a safe location.
30617 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
30618 compiled with the @samp{-pg} compiler option.
30620 @kindex maint set show-debug-regs
30621 @kindex maint show show-debug-regs
30622 @cindex hardware debug registers
30623 @item maint set show-debug-regs
30624 @itemx maint show show-debug-regs
30625 Control whether to show variables that mirror the hardware debug
30626 registers. Use @code{ON} to enable, @code{OFF} to disable. If
30627 enabled, the debug registers values are shown when @value{GDBN} inserts or
30628 removes a hardware breakpoint or watchpoint, and when the inferior
30629 triggers a hardware-assisted breakpoint or watchpoint.
30631 @kindex maint set show-all-tib
30632 @kindex maint show show-all-tib
30633 @item maint set show-all-tib
30634 @itemx maint show show-all-tib
30635 Control whether to show all non zero areas within a 1k block starting
30636 at thread local base, when using the @samp{info w32 thread-information-block}
30639 @kindex maint space
30640 @cindex memory used by commands
30642 Control whether to display memory usage for each command. If set to a
30643 nonzero value, @value{GDBN} will display how much memory each command
30644 took, following the command's own output. This can also be requested
30645 by invoking @value{GDBN} with the @option{--statistics} command-line
30646 switch (@pxref{Mode Options}).
30649 @cindex time of command execution
30651 Control whether to display the execution time for each command. If
30652 set to a nonzero value, @value{GDBN} will display how much time it
30653 took to execute each command, following the command's own output.
30654 The time is not printed for the commands that run the target, since
30655 there's no mechanism currently to compute how much time was spend
30656 by @value{GDBN} and how much time was spend by the program been debugged.
30657 it's not possibly currently
30658 This can also be requested by invoking @value{GDBN} with the
30659 @option{--statistics} command-line switch (@pxref{Mode Options}).
30661 @kindex maint translate-address
30662 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
30663 Find the symbol stored at the location specified by the address
30664 @var{addr} and an optional section name @var{section}. If found,
30665 @value{GDBN} prints the name of the closest symbol and an offset from
30666 the symbol's location to the specified address. This is similar to
30667 the @code{info address} command (@pxref{Symbols}), except that this
30668 command also allows to find symbols in other sections.
30670 If section was not specified, the section in which the symbol was found
30671 is also printed. For dynamically linked executables, the name of
30672 executable or shared library containing the symbol is printed as well.
30676 The following command is useful for non-interactive invocations of
30677 @value{GDBN}, such as in the test suite.
30680 @item set watchdog @var{nsec}
30681 @kindex set watchdog
30682 @cindex watchdog timer
30683 @cindex timeout for commands
30684 Set the maximum number of seconds @value{GDBN} will wait for the
30685 target operation to finish. If this time expires, @value{GDBN}
30686 reports and error and the command is aborted.
30688 @item show watchdog
30689 Show the current setting of the target wait timeout.
30692 @node Remote Protocol
30693 @appendix @value{GDBN} Remote Serial Protocol
30698 * Stop Reply Packets::
30699 * General Query Packets::
30700 * Architecture-Specific Protocol Details::
30701 * Tracepoint Packets::
30702 * Host I/O Packets::
30704 * Notification Packets::
30705 * Remote Non-Stop::
30706 * Packet Acknowledgment::
30708 * File-I/O Remote Protocol Extension::
30709 * Library List Format::
30710 * Memory Map Format::
30711 * Thread List Format::
30717 There may be occasions when you need to know something about the
30718 protocol---for example, if there is only one serial port to your target
30719 machine, you might want your program to do something special if it
30720 recognizes a packet meant for @value{GDBN}.
30722 In the examples below, @samp{->} and @samp{<-} are used to indicate
30723 transmitted and received data, respectively.
30725 @cindex protocol, @value{GDBN} remote serial
30726 @cindex serial protocol, @value{GDBN} remote
30727 @cindex remote serial protocol
30728 All @value{GDBN} commands and responses (other than acknowledgments
30729 and notifications, see @ref{Notification Packets}) are sent as a
30730 @var{packet}. A @var{packet} is introduced with the character
30731 @samp{$}, the actual @var{packet-data}, and the terminating character
30732 @samp{#} followed by a two-digit @var{checksum}:
30735 @code{$}@var{packet-data}@code{#}@var{checksum}
30739 @cindex checksum, for @value{GDBN} remote
30741 The two-digit @var{checksum} is computed as the modulo 256 sum of all
30742 characters between the leading @samp{$} and the trailing @samp{#} (an
30743 eight bit unsigned checksum).
30745 Implementors should note that prior to @value{GDBN} 5.0 the protocol
30746 specification also included an optional two-digit @var{sequence-id}:
30749 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
30752 @cindex sequence-id, for @value{GDBN} remote
30754 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
30755 has never output @var{sequence-id}s. Stubs that handle packets added
30756 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
30758 When either the host or the target machine receives a packet, the first
30759 response expected is an acknowledgment: either @samp{+} (to indicate
30760 the package was received correctly) or @samp{-} (to request
30764 -> @code{$}@var{packet-data}@code{#}@var{checksum}
30769 The @samp{+}/@samp{-} acknowledgments can be disabled
30770 once a connection is established.
30771 @xref{Packet Acknowledgment}, for details.
30773 The host (@value{GDBN}) sends @var{command}s, and the target (the
30774 debugging stub incorporated in your program) sends a @var{response}. In
30775 the case of step and continue @var{command}s, the response is only sent
30776 when the operation has completed, and the target has again stopped all
30777 threads in all attached processes. This is the default all-stop mode
30778 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
30779 execution mode; see @ref{Remote Non-Stop}, for details.
30781 @var{packet-data} consists of a sequence of characters with the
30782 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
30785 @cindex remote protocol, field separator
30786 Fields within the packet should be separated using @samp{,} @samp{;} or
30787 @samp{:}. Except where otherwise noted all numbers are represented in
30788 @sc{hex} with leading zeros suppressed.
30790 Implementors should note that prior to @value{GDBN} 5.0, the character
30791 @samp{:} could not appear as the third character in a packet (as it
30792 would potentially conflict with the @var{sequence-id}).
30794 @cindex remote protocol, binary data
30795 @anchor{Binary Data}
30796 Binary data in most packets is encoded either as two hexadecimal
30797 digits per byte of binary data. This allowed the traditional remote
30798 protocol to work over connections which were only seven-bit clean.
30799 Some packets designed more recently assume an eight-bit clean
30800 connection, and use a more efficient encoding to send and receive
30803 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
30804 as an escape character. Any escaped byte is transmitted as the escape
30805 character followed by the original character XORed with @code{0x20}.
30806 For example, the byte @code{0x7d} would be transmitted as the two
30807 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
30808 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
30809 @samp{@}}) must always be escaped. Responses sent by the stub
30810 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
30811 is not interpreted as the start of a run-length encoded sequence
30814 Response @var{data} can be run-length encoded to save space.
30815 Run-length encoding replaces runs of identical characters with one
30816 instance of the repeated character, followed by a @samp{*} and a
30817 repeat count. The repeat count is itself sent encoded, to avoid
30818 binary characters in @var{data}: a value of @var{n} is sent as
30819 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
30820 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
30821 code 32) for a repeat count of 3. (This is because run-length
30822 encoding starts to win for counts 3 or more.) Thus, for example,
30823 @samp{0* } is a run-length encoding of ``0000'': the space character
30824 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
30827 The printable characters @samp{#} and @samp{$} or with a numeric value
30828 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
30829 seven repeats (@samp{$}) can be expanded using a repeat count of only
30830 five (@samp{"}). For example, @samp{00000000} can be encoded as
30833 The error response returned for some packets includes a two character
30834 error number. That number is not well defined.
30836 @cindex empty response, for unsupported packets
30837 For any @var{command} not supported by the stub, an empty response
30838 (@samp{$#00}) should be returned. That way it is possible to extend the
30839 protocol. A newer @value{GDBN} can tell if a packet is supported based
30842 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
30843 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
30849 The following table provides a complete list of all currently defined
30850 @var{command}s and their corresponding response @var{data}.
30851 @xref{File-I/O Remote Protocol Extension}, for details about the File
30852 I/O extension of the remote protocol.
30854 Each packet's description has a template showing the packet's overall
30855 syntax, followed by an explanation of the packet's meaning. We
30856 include spaces in some of the templates for clarity; these are not
30857 part of the packet's syntax. No @value{GDBN} packet uses spaces to
30858 separate its components. For example, a template like @samp{foo
30859 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
30860 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
30861 @var{baz}. @value{GDBN} does not transmit a space character between the
30862 @samp{foo} and the @var{bar}, or between the @var{bar} and the
30865 @cindex @var{thread-id}, in remote protocol
30866 @anchor{thread-id syntax}
30867 Several packets and replies include a @var{thread-id} field to identify
30868 a thread. Normally these are positive numbers with a target-specific
30869 interpretation, formatted as big-endian hex strings. A @var{thread-id}
30870 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
30873 In addition, the remote protocol supports a multiprocess feature in
30874 which the @var{thread-id} syntax is extended to optionally include both
30875 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
30876 The @var{pid} (process) and @var{tid} (thread) components each have the
30877 format described above: a positive number with target-specific
30878 interpretation formatted as a big-endian hex string, literal @samp{-1}
30879 to indicate all processes or threads (respectively), or @samp{0} to
30880 indicate an arbitrary process or thread. Specifying just a process, as
30881 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
30882 error to specify all processes but a specific thread, such as
30883 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
30884 for those packets and replies explicitly documented to include a process
30885 ID, rather than a @var{thread-id}.
30887 The multiprocess @var{thread-id} syntax extensions are only used if both
30888 @value{GDBN} and the stub report support for the @samp{multiprocess}
30889 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
30892 Note that all packet forms beginning with an upper- or lower-case
30893 letter, other than those described here, are reserved for future use.
30895 Here are the packet descriptions.
30900 @cindex @samp{!} packet
30901 @anchor{extended mode}
30902 Enable extended mode. In extended mode, the remote server is made
30903 persistent. The @samp{R} packet is used to restart the program being
30909 The remote target both supports and has enabled extended mode.
30913 @cindex @samp{?} packet
30914 Indicate the reason the target halted. The reply is the same as for
30915 step and continue. This packet has a special interpretation when the
30916 target is in non-stop mode; see @ref{Remote Non-Stop}.
30919 @xref{Stop Reply Packets}, for the reply specifications.
30921 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
30922 @cindex @samp{A} packet
30923 Initialized @code{argv[]} array passed into program. @var{arglen}
30924 specifies the number of bytes in the hex encoded byte stream
30925 @var{arg}. See @code{gdbserver} for more details.
30930 The arguments were set.
30936 @cindex @samp{b} packet
30937 (Don't use this packet; its behavior is not well-defined.)
30938 Change the serial line speed to @var{baud}.
30940 JTC: @emph{When does the transport layer state change? When it's
30941 received, or after the ACK is transmitted. In either case, there are
30942 problems if the command or the acknowledgment packet is dropped.}
30944 Stan: @emph{If people really wanted to add something like this, and get
30945 it working for the first time, they ought to modify ser-unix.c to send
30946 some kind of out-of-band message to a specially-setup stub and have the
30947 switch happen "in between" packets, so that from remote protocol's point
30948 of view, nothing actually happened.}
30950 @item B @var{addr},@var{mode}
30951 @cindex @samp{B} packet
30952 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
30953 breakpoint at @var{addr}.
30955 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
30956 (@pxref{insert breakpoint or watchpoint packet}).
30958 @cindex @samp{bc} packet
30961 Backward continue. Execute the target system in reverse. No parameter.
30962 @xref{Reverse Execution}, for more information.
30965 @xref{Stop Reply Packets}, for the reply specifications.
30967 @cindex @samp{bs} packet
30970 Backward single step. Execute one instruction in reverse. No parameter.
30971 @xref{Reverse Execution}, for more information.
30974 @xref{Stop Reply Packets}, for the reply specifications.
30976 @item c @r{[}@var{addr}@r{]}
30977 @cindex @samp{c} packet
30978 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
30979 resume at current address.
30982 @xref{Stop Reply Packets}, for the reply specifications.
30984 @item C @var{sig}@r{[};@var{addr}@r{]}
30985 @cindex @samp{C} packet
30986 Continue with signal @var{sig} (hex signal number). If
30987 @samp{;@var{addr}} is omitted, resume at same address.
30990 @xref{Stop Reply Packets}, for the reply specifications.
30993 @cindex @samp{d} packet
30996 Don't use this packet; instead, define a general set packet
30997 (@pxref{General Query Packets}).
31001 @cindex @samp{D} packet
31002 The first form of the packet is used to detach @value{GDBN} from the
31003 remote system. It is sent to the remote target
31004 before @value{GDBN} disconnects via the @code{detach} command.
31006 The second form, including a process ID, is used when multiprocess
31007 protocol extensions are enabled (@pxref{multiprocess extensions}), to
31008 detach only a specific process. The @var{pid} is specified as a
31009 big-endian hex string.
31019 @item F @var{RC},@var{EE},@var{CF};@var{XX}
31020 @cindex @samp{F} packet
31021 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
31022 This is part of the File-I/O protocol extension. @xref{File-I/O
31023 Remote Protocol Extension}, for the specification.
31026 @anchor{read registers packet}
31027 @cindex @samp{g} packet
31028 Read general registers.
31032 @item @var{XX@dots{}}
31033 Each byte of register data is described by two hex digits. The bytes
31034 with the register are transmitted in target byte order. The size of
31035 each register and their position within the @samp{g} packet are
31036 determined by the @value{GDBN} internal gdbarch functions
31037 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
31038 specification of several standard @samp{g} packets is specified below.
31043 @item G @var{XX@dots{}}
31044 @cindex @samp{G} packet
31045 Write general registers. @xref{read registers packet}, for a
31046 description of the @var{XX@dots{}} data.
31056 @item H @var{c} @var{thread-id}
31057 @cindex @samp{H} packet
31058 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
31059 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
31060 should be @samp{c} for step and continue operations, @samp{g} for other
31061 operations. The thread designator @var{thread-id} has the format and
31062 interpretation described in @ref{thread-id syntax}.
31073 @c 'H': How restrictive (or permissive) is the thread model. If a
31074 @c thread is selected and stopped, are other threads allowed
31075 @c to continue to execute? As I mentioned above, I think the
31076 @c semantics of each command when a thread is selected must be
31077 @c described. For example:
31079 @c 'g': If the stub supports threads and a specific thread is
31080 @c selected, returns the register block from that thread;
31081 @c otherwise returns current registers.
31083 @c 'G' If the stub supports threads and a specific thread is
31084 @c selected, sets the registers of the register block of
31085 @c that thread; otherwise sets current registers.
31087 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
31088 @anchor{cycle step packet}
31089 @cindex @samp{i} packet
31090 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
31091 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
31092 step starting at that address.
31095 @cindex @samp{I} packet
31096 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
31100 @cindex @samp{k} packet
31103 FIXME: @emph{There is no description of how to operate when a specific
31104 thread context has been selected (i.e.@: does 'k' kill only that
31107 @item m @var{addr},@var{length}
31108 @cindex @samp{m} packet
31109 Read @var{length} bytes of memory starting at address @var{addr}.
31110 Note that @var{addr} may not be aligned to any particular boundary.
31112 The stub need not use any particular size or alignment when gathering
31113 data from memory for the response; even if @var{addr} is word-aligned
31114 and @var{length} is a multiple of the word size, the stub is free to
31115 use byte accesses, or not. For this reason, this packet may not be
31116 suitable for accessing memory-mapped I/O devices.
31117 @cindex alignment of remote memory accesses
31118 @cindex size of remote memory accesses
31119 @cindex memory, alignment and size of remote accesses
31123 @item @var{XX@dots{}}
31124 Memory contents; each byte is transmitted as a two-digit hexadecimal
31125 number. The reply may contain fewer bytes than requested if the
31126 server was able to read only part of the region of memory.
31131 @item M @var{addr},@var{length}:@var{XX@dots{}}
31132 @cindex @samp{M} packet
31133 Write @var{length} bytes of memory starting at address @var{addr}.
31134 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
31135 hexadecimal number.
31142 for an error (this includes the case where only part of the data was
31147 @cindex @samp{p} packet
31148 Read the value of register @var{n}; @var{n} is in hex.
31149 @xref{read registers packet}, for a description of how the returned
31150 register value is encoded.
31154 @item @var{XX@dots{}}
31155 the register's value
31159 Indicating an unrecognized @var{query}.
31162 @item P @var{n@dots{}}=@var{r@dots{}}
31163 @anchor{write register packet}
31164 @cindex @samp{P} packet
31165 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
31166 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
31167 digits for each byte in the register (target byte order).
31177 @item q @var{name} @var{params}@dots{}
31178 @itemx Q @var{name} @var{params}@dots{}
31179 @cindex @samp{q} packet
31180 @cindex @samp{Q} packet
31181 General query (@samp{q}) and set (@samp{Q}). These packets are
31182 described fully in @ref{General Query Packets}.
31185 @cindex @samp{r} packet
31186 Reset the entire system.
31188 Don't use this packet; use the @samp{R} packet instead.
31191 @cindex @samp{R} packet
31192 Restart the program being debugged. @var{XX}, while needed, is ignored.
31193 This packet is only available in extended mode (@pxref{extended mode}).
31195 The @samp{R} packet has no reply.
31197 @item s @r{[}@var{addr}@r{]}
31198 @cindex @samp{s} packet
31199 Single step. @var{addr} is the address at which to resume. If
31200 @var{addr} is omitted, resume at same address.
31203 @xref{Stop Reply Packets}, for the reply specifications.
31205 @item S @var{sig}@r{[};@var{addr}@r{]}
31206 @anchor{step with signal packet}
31207 @cindex @samp{S} packet
31208 Step with signal. This is analogous to the @samp{C} packet, but
31209 requests a single-step, rather than a normal resumption of execution.
31212 @xref{Stop Reply Packets}, for the reply specifications.
31214 @item t @var{addr}:@var{PP},@var{MM}
31215 @cindex @samp{t} packet
31216 Search backwards starting at address @var{addr} for a match with pattern
31217 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
31218 @var{addr} must be at least 3 digits.
31220 @item T @var{thread-id}
31221 @cindex @samp{T} packet
31222 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
31227 thread is still alive
31233 Packets starting with @samp{v} are identified by a multi-letter name,
31234 up to the first @samp{;} or @samp{?} (or the end of the packet).
31236 @item vAttach;@var{pid}
31237 @cindex @samp{vAttach} packet
31238 Attach to a new process with the specified process ID @var{pid}.
31239 The process ID is a
31240 hexadecimal integer identifying the process. In all-stop mode, all
31241 threads in the attached process are stopped; in non-stop mode, it may be
31242 attached without being stopped if that is supported by the target.
31244 @c In non-stop mode, on a successful vAttach, the stub should set the
31245 @c current thread to a thread of the newly-attached process. After
31246 @c attaching, GDB queries for the attached process's thread ID with qC.
31247 @c Also note that, from a user perspective, whether or not the
31248 @c target is stopped on attach in non-stop mode depends on whether you
31249 @c use the foreground or background version of the attach command, not
31250 @c on what vAttach does; GDB does the right thing with respect to either
31251 @c stopping or restarting threads.
31253 This packet is only available in extended mode (@pxref{extended mode}).
31259 @item @r{Any stop packet}
31260 for success in all-stop mode (@pxref{Stop Reply Packets})
31262 for success in non-stop mode (@pxref{Remote Non-Stop})
31265 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
31266 @cindex @samp{vCont} packet
31267 Resume the inferior, specifying different actions for each thread.
31268 If an action is specified with no @var{thread-id}, then it is applied to any
31269 threads that don't have a specific action specified; if no default action is
31270 specified then other threads should remain stopped in all-stop mode and
31271 in their current state in non-stop mode.
31272 Specifying multiple
31273 default actions is an error; specifying no actions is also an error.
31274 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
31276 Currently supported actions are:
31282 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
31286 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
31291 The optional argument @var{addr} normally associated with the
31292 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
31293 not supported in @samp{vCont}.
31295 The @samp{t} action is only relevant in non-stop mode
31296 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
31297 A stop reply should be generated for any affected thread not already stopped.
31298 When a thread is stopped by means of a @samp{t} action,
31299 the corresponding stop reply should indicate that the thread has stopped with
31300 signal @samp{0}, regardless of whether the target uses some other signal
31301 as an implementation detail.
31304 @xref{Stop Reply Packets}, for the reply specifications.
31307 @cindex @samp{vCont?} packet
31308 Request a list of actions supported by the @samp{vCont} packet.
31312 @item vCont@r{[};@var{action}@dots{}@r{]}
31313 The @samp{vCont} packet is supported. Each @var{action} is a supported
31314 command in the @samp{vCont} packet.
31316 The @samp{vCont} packet is not supported.
31319 @item vFile:@var{operation}:@var{parameter}@dots{}
31320 @cindex @samp{vFile} packet
31321 Perform a file operation on the target system. For details,
31322 see @ref{Host I/O Packets}.
31324 @item vFlashErase:@var{addr},@var{length}
31325 @cindex @samp{vFlashErase} packet
31326 Direct the stub to erase @var{length} bytes of flash starting at
31327 @var{addr}. The region may enclose any number of flash blocks, but
31328 its start and end must fall on block boundaries, as indicated by the
31329 flash block size appearing in the memory map (@pxref{Memory Map
31330 Format}). @value{GDBN} groups flash memory programming operations
31331 together, and sends a @samp{vFlashDone} request after each group; the
31332 stub is allowed to delay erase operation until the @samp{vFlashDone}
31333 packet is received.
31335 The stub must support @samp{vCont} if it reports support for
31336 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
31337 this case @samp{vCont} actions can be specified to apply to all threads
31338 in a process by using the @samp{p@var{pid}.-1} form of the
31349 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
31350 @cindex @samp{vFlashWrite} packet
31351 Direct the stub to write data to flash address @var{addr}. The data
31352 is passed in binary form using the same encoding as for the @samp{X}
31353 packet (@pxref{Binary Data}). The memory ranges specified by
31354 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
31355 not overlap, and must appear in order of increasing addresses
31356 (although @samp{vFlashErase} packets for higher addresses may already
31357 have been received; the ordering is guaranteed only between
31358 @samp{vFlashWrite} packets). If a packet writes to an address that was
31359 neither erased by a preceding @samp{vFlashErase} packet nor by some other
31360 target-specific method, the results are unpredictable.
31368 for vFlashWrite addressing non-flash memory
31374 @cindex @samp{vFlashDone} packet
31375 Indicate to the stub that flash programming operation is finished.
31376 The stub is permitted to delay or batch the effects of a group of
31377 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
31378 @samp{vFlashDone} packet is received. The contents of the affected
31379 regions of flash memory are unpredictable until the @samp{vFlashDone}
31380 request is completed.
31382 @item vKill;@var{pid}
31383 @cindex @samp{vKill} packet
31384 Kill the process with the specified process ID. @var{pid} is a
31385 hexadecimal integer identifying the process. This packet is used in
31386 preference to @samp{k} when multiprocess protocol extensions are
31387 supported; see @ref{multiprocess extensions}.
31397 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
31398 @cindex @samp{vRun} packet
31399 Run the program @var{filename}, passing it each @var{argument} on its
31400 command line. The file and arguments are hex-encoded strings. If
31401 @var{filename} is an empty string, the stub may use a default program
31402 (e.g.@: the last program run). The program is created in the stopped
31405 @c FIXME: What about non-stop mode?
31407 This packet is only available in extended mode (@pxref{extended mode}).
31413 @item @r{Any stop packet}
31414 for success (@pxref{Stop Reply Packets})
31418 @anchor{vStopped packet}
31419 @cindex @samp{vStopped} packet
31421 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
31422 reply and prompt for the stub to report another one.
31426 @item @r{Any stop packet}
31427 if there is another unreported stop event (@pxref{Stop Reply Packets})
31429 if there are no unreported stop events
31432 @item X @var{addr},@var{length}:@var{XX@dots{}}
31434 @cindex @samp{X} packet
31435 Write data to memory, where the data is transmitted in binary.
31436 @var{addr} is address, @var{length} is number of bytes,
31437 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
31447 @item z @var{type},@var{addr},@var{kind}
31448 @itemx Z @var{type},@var{addr},@var{kind}
31449 @anchor{insert breakpoint or watchpoint packet}
31450 @cindex @samp{z} packet
31451 @cindex @samp{Z} packets
31452 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
31453 watchpoint starting at address @var{address} of kind @var{kind}.
31455 Each breakpoint and watchpoint packet @var{type} is documented
31458 @emph{Implementation notes: A remote target shall return an empty string
31459 for an unrecognized breakpoint or watchpoint packet @var{type}. A
31460 remote target shall support either both or neither of a given
31461 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
31462 avoid potential problems with duplicate packets, the operations should
31463 be implemented in an idempotent way.}
31465 @item z0,@var{addr},@var{kind}
31466 @itemx Z0,@var{addr},@var{kind}
31467 @cindex @samp{z0} packet
31468 @cindex @samp{Z0} packet
31469 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
31470 @var{addr} of type @var{kind}.
31472 A memory breakpoint is implemented by replacing the instruction at
31473 @var{addr} with a software breakpoint or trap instruction. The
31474 @var{kind} is target-specific and typically indicates the size of
31475 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
31476 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
31477 architectures have additional meanings for @var{kind};
31478 see @ref{Architecture-Specific Protocol Details}.
31480 @emph{Implementation note: It is possible for a target to copy or move
31481 code that contains memory breakpoints (e.g., when implementing
31482 overlays). The behavior of this packet, in the presence of such a
31483 target, is not defined.}
31495 @item z1,@var{addr},@var{kind}
31496 @itemx Z1,@var{addr},@var{kind}
31497 @cindex @samp{z1} packet
31498 @cindex @samp{Z1} packet
31499 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
31500 address @var{addr}.
31502 A hardware breakpoint is implemented using a mechanism that is not
31503 dependant on being able to modify the target's memory. @var{kind}
31504 has the same meaning as in @samp{Z0} packets.
31506 @emph{Implementation note: A hardware breakpoint is not affected by code
31519 @item z2,@var{addr},@var{kind}
31520 @itemx Z2,@var{addr},@var{kind}
31521 @cindex @samp{z2} packet
31522 @cindex @samp{Z2} packet
31523 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
31524 @var{kind} is interpreted as the number of bytes to watch.
31536 @item z3,@var{addr},@var{kind}
31537 @itemx Z3,@var{addr},@var{kind}
31538 @cindex @samp{z3} packet
31539 @cindex @samp{Z3} packet
31540 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
31541 @var{kind} is interpreted as the number of bytes to watch.
31553 @item z4,@var{addr},@var{kind}
31554 @itemx Z4,@var{addr},@var{kind}
31555 @cindex @samp{z4} packet
31556 @cindex @samp{Z4} packet
31557 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
31558 @var{kind} is interpreted as the number of bytes to watch.
31572 @node Stop Reply Packets
31573 @section Stop Reply Packets
31574 @cindex stop reply packets
31576 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
31577 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
31578 receive any of the below as a reply. Except for @samp{?}
31579 and @samp{vStopped}, that reply is only returned
31580 when the target halts. In the below the exact meaning of @dfn{signal
31581 number} is defined by the header @file{include/gdb/signals.h} in the
31582 @value{GDBN} source code.
31584 As in the description of request packets, we include spaces in the
31585 reply templates for clarity; these are not part of the reply packet's
31586 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
31592 The program received signal number @var{AA} (a two-digit hexadecimal
31593 number). This is equivalent to a @samp{T} response with no
31594 @var{n}:@var{r} pairs.
31596 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
31597 @cindex @samp{T} packet reply
31598 The program received signal number @var{AA} (a two-digit hexadecimal
31599 number). This is equivalent to an @samp{S} response, except that the
31600 @samp{@var{n}:@var{r}} pairs can carry values of important registers
31601 and other information directly in the stop reply packet, reducing
31602 round-trip latency. Single-step and breakpoint traps are reported
31603 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
31607 If @var{n} is a hexadecimal number, it is a register number, and the
31608 corresponding @var{r} gives that register's value. @var{r} is a
31609 series of bytes in target byte order, with each byte given by a
31610 two-digit hex number.
31613 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
31614 the stopped thread, as specified in @ref{thread-id syntax}.
31617 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
31618 the core on which the stop event was detected.
31621 If @var{n} is a recognized @dfn{stop reason}, it describes a more
31622 specific event that stopped the target. The currently defined stop
31623 reasons are listed below. @var{aa} should be @samp{05}, the trap
31624 signal. At most one stop reason should be present.
31627 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
31628 and go on to the next; this allows us to extend the protocol in the
31632 The currently defined stop reasons are:
31638 The packet indicates a watchpoint hit, and @var{r} is the data address, in
31641 @cindex shared library events, remote reply
31643 The packet indicates that the loaded libraries have changed.
31644 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
31645 list of loaded libraries. @var{r} is ignored.
31647 @cindex replay log events, remote reply
31649 The packet indicates that the target cannot continue replaying
31650 logged execution events, because it has reached the end (or the
31651 beginning when executing backward) of the log. The value of @var{r}
31652 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
31653 for more information.
31657 @itemx W @var{AA} ; process:@var{pid}
31658 The process exited, and @var{AA} is the exit status. This is only
31659 applicable to certain targets.
31661 The second form of the response, including the process ID of the exited
31662 process, can be used only when @value{GDBN} has reported support for
31663 multiprocess protocol extensions; see @ref{multiprocess extensions}.
31664 The @var{pid} is formatted as a big-endian hex string.
31667 @itemx X @var{AA} ; process:@var{pid}
31668 The process terminated with signal @var{AA}.
31670 The second form of the response, including the process ID of the
31671 terminated process, can be used only when @value{GDBN} has reported
31672 support for multiprocess protocol extensions; see @ref{multiprocess
31673 extensions}. The @var{pid} is formatted as a big-endian hex string.
31675 @item O @var{XX}@dots{}
31676 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
31677 written as the program's console output. This can happen at any time
31678 while the program is running and the debugger should continue to wait
31679 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
31681 @item F @var{call-id},@var{parameter}@dots{}
31682 @var{call-id} is the identifier which says which host system call should
31683 be called. This is just the name of the function. Translation into the
31684 correct system call is only applicable as it's defined in @value{GDBN}.
31685 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
31688 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
31689 this very system call.
31691 The target replies with this packet when it expects @value{GDBN} to
31692 call a host system call on behalf of the target. @value{GDBN} replies
31693 with an appropriate @samp{F} packet and keeps up waiting for the next
31694 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
31695 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
31696 Protocol Extension}, for more details.
31700 @node General Query Packets
31701 @section General Query Packets
31702 @cindex remote query requests
31704 Packets starting with @samp{q} are @dfn{general query packets};
31705 packets starting with @samp{Q} are @dfn{general set packets}. General
31706 query and set packets are a semi-unified form for retrieving and
31707 sending information to and from the stub.
31709 The initial letter of a query or set packet is followed by a name
31710 indicating what sort of thing the packet applies to. For example,
31711 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
31712 definitions with the stub. These packet names follow some
31717 The name must not contain commas, colons or semicolons.
31719 Most @value{GDBN} query and set packets have a leading upper case
31722 The names of custom vendor packets should use a company prefix, in
31723 lower case, followed by a period. For example, packets designed at
31724 the Acme Corporation might begin with @samp{qacme.foo} (for querying
31725 foos) or @samp{Qacme.bar} (for setting bars).
31728 The name of a query or set packet should be separated from any
31729 parameters by a @samp{:}; the parameters themselves should be
31730 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
31731 full packet name, and check for a separator or the end of the packet,
31732 in case two packet names share a common prefix. New packets should not begin
31733 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
31734 packets predate these conventions, and have arguments without any terminator
31735 for the packet name; we suspect they are in widespread use in places that
31736 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
31737 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
31740 Like the descriptions of the other packets, each description here
31741 has a template showing the packet's overall syntax, followed by an
31742 explanation of the packet's meaning. We include spaces in some of the
31743 templates for clarity; these are not part of the packet's syntax. No
31744 @value{GDBN} packet uses spaces to separate its components.
31746 Here are the currently defined query and set packets:
31750 @item QAllow:@var{op}:@var{val}@dots{}
31751 @cindex @samp{QAllow} packet
31752 Specify which operations @value{GDBN} expects to request of the
31753 target, as a semicolon-separated list of operation name and value
31754 pairs. Possible values for @var{op} include @samp{WriteReg},
31755 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
31756 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
31757 indicating that @value{GDBN} will not request the operation, or 1,
31758 indicating that it may. (The target can then use this to set up its
31759 own internals optimally, for instance if the debugger never expects to
31760 insert breakpoints, it may not need to install its own trap handler.)
31763 @cindex current thread, remote request
31764 @cindex @samp{qC} packet
31765 Return the current thread ID.
31769 @item QC @var{thread-id}
31770 Where @var{thread-id} is a thread ID as documented in
31771 @ref{thread-id syntax}.
31772 @item @r{(anything else)}
31773 Any other reply implies the old thread ID.
31776 @item qCRC:@var{addr},@var{length}
31777 @cindex CRC of memory block, remote request
31778 @cindex @samp{qCRC} packet
31779 Compute the CRC checksum of a block of memory using CRC-32 defined in
31780 IEEE 802.3. The CRC is computed byte at a time, taking the most
31781 significant bit of each byte first. The initial pattern code
31782 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
31784 @emph{Note:} This is the same CRC used in validating separate debug
31785 files (@pxref{Separate Debug Files, , Debugging Information in Separate
31786 Files}). However the algorithm is slightly different. When validating
31787 separate debug files, the CRC is computed taking the @emph{least}
31788 significant bit of each byte first, and the final result is inverted to
31789 detect trailing zeros.
31794 An error (such as memory fault)
31795 @item C @var{crc32}
31796 The specified memory region's checksum is @var{crc32}.
31800 @itemx qsThreadInfo
31801 @cindex list active threads, remote request
31802 @cindex @samp{qfThreadInfo} packet
31803 @cindex @samp{qsThreadInfo} packet
31804 Obtain a list of all active thread IDs from the target (OS). Since there
31805 may be too many active threads to fit into one reply packet, this query
31806 works iteratively: it may require more than one query/reply sequence to
31807 obtain the entire list of threads. The first query of the sequence will
31808 be the @samp{qfThreadInfo} query; subsequent queries in the
31809 sequence will be the @samp{qsThreadInfo} query.
31811 NOTE: This packet replaces the @samp{qL} query (see below).
31815 @item m @var{thread-id}
31817 @item m @var{thread-id},@var{thread-id}@dots{}
31818 a comma-separated list of thread IDs
31820 (lower case letter @samp{L}) denotes end of list.
31823 In response to each query, the target will reply with a list of one or
31824 more thread IDs, separated by commas.
31825 @value{GDBN} will respond to each reply with a request for more thread
31826 ids (using the @samp{qs} form of the query), until the target responds
31827 with @samp{l} (lower-case ell, for @dfn{last}).
31828 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
31831 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
31832 @cindex get thread-local storage address, remote request
31833 @cindex @samp{qGetTLSAddr} packet
31834 Fetch the address associated with thread local storage specified
31835 by @var{thread-id}, @var{offset}, and @var{lm}.
31837 @var{thread-id} is the thread ID associated with the
31838 thread for which to fetch the TLS address. @xref{thread-id syntax}.
31840 @var{offset} is the (big endian, hex encoded) offset associated with the
31841 thread local variable. (This offset is obtained from the debug
31842 information associated with the variable.)
31844 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
31845 the load module associated with the thread local storage. For example,
31846 a @sc{gnu}/Linux system will pass the link map address of the shared
31847 object associated with the thread local storage under consideration.
31848 Other operating environments may choose to represent the load module
31849 differently, so the precise meaning of this parameter will vary.
31853 @item @var{XX}@dots{}
31854 Hex encoded (big endian) bytes representing the address of the thread
31855 local storage requested.
31858 An error occurred. @var{nn} are hex digits.
31861 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
31864 @item qGetTIBAddr:@var{thread-id}
31865 @cindex get thread information block address
31866 @cindex @samp{qGetTIBAddr} packet
31867 Fetch address of the Windows OS specific Thread Information Block.
31869 @var{thread-id} is the thread ID associated with the thread.
31873 @item @var{XX}@dots{}
31874 Hex encoded (big endian) bytes representing the linear address of the
31875 thread information block.
31878 An error occured. This means that either the thread was not found, or the
31879 address could not be retrieved.
31882 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
31885 @item qL @var{startflag} @var{threadcount} @var{nextthread}
31886 Obtain thread information from RTOS. Where: @var{startflag} (one hex
31887 digit) is one to indicate the first query and zero to indicate a
31888 subsequent query; @var{threadcount} (two hex digits) is the maximum
31889 number of threads the response packet can contain; and @var{nextthread}
31890 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
31891 returned in the response as @var{argthread}.
31893 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
31897 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
31898 Where: @var{count} (two hex digits) is the number of threads being
31899 returned; @var{done} (one hex digit) is zero to indicate more threads
31900 and one indicates no further threads; @var{argthreadid} (eight hex
31901 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
31902 is a sequence of thread IDs from the target. @var{threadid} (eight hex
31903 digits). See @code{remote.c:parse_threadlist_response()}.
31907 @cindex section offsets, remote request
31908 @cindex @samp{qOffsets} packet
31909 Get section offsets that the target used when relocating the downloaded
31914 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
31915 Relocate the @code{Text} section by @var{xxx} from its original address.
31916 Relocate the @code{Data} section by @var{yyy} from its original address.
31917 If the object file format provides segment information (e.g.@: @sc{elf}
31918 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
31919 segments by the supplied offsets.
31921 @emph{Note: while a @code{Bss} offset may be included in the response,
31922 @value{GDBN} ignores this and instead applies the @code{Data} offset
31923 to the @code{Bss} section.}
31925 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
31926 Relocate the first segment of the object file, which conventionally
31927 contains program code, to a starting address of @var{xxx}. If
31928 @samp{DataSeg} is specified, relocate the second segment, which
31929 conventionally contains modifiable data, to a starting address of
31930 @var{yyy}. @value{GDBN} will report an error if the object file
31931 does not contain segment information, or does not contain at least
31932 as many segments as mentioned in the reply. Extra segments are
31933 kept at fixed offsets relative to the last relocated segment.
31936 @item qP @var{mode} @var{thread-id}
31937 @cindex thread information, remote request
31938 @cindex @samp{qP} packet
31939 Returns information on @var{thread-id}. Where: @var{mode} is a hex
31940 encoded 32 bit mode; @var{thread-id} is a thread ID
31941 (@pxref{thread-id syntax}).
31943 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
31946 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
31950 @cindex non-stop mode, remote request
31951 @cindex @samp{QNonStop} packet
31953 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
31954 @xref{Remote Non-Stop}, for more information.
31959 The request succeeded.
31962 An error occurred. @var{nn} are hex digits.
31965 An empty reply indicates that @samp{QNonStop} is not supported by
31969 This packet is not probed by default; the remote stub must request it,
31970 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31971 Use of this packet is controlled by the @code{set non-stop} command;
31972 @pxref{Non-Stop Mode}.
31974 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
31975 @cindex pass signals to inferior, remote request
31976 @cindex @samp{QPassSignals} packet
31977 @anchor{QPassSignals}
31978 Each listed @var{signal} should be passed directly to the inferior process.
31979 Signals are numbered identically to continue packets and stop replies
31980 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
31981 strictly greater than the previous item. These signals do not need to stop
31982 the inferior, or be reported to @value{GDBN}. All other signals should be
31983 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
31984 combine; any earlier @samp{QPassSignals} list is completely replaced by the
31985 new list. This packet improves performance when using @samp{handle
31986 @var{signal} nostop noprint pass}.
31991 The request succeeded.
31994 An error occurred. @var{nn} are hex digits.
31997 An empty reply indicates that @samp{QPassSignals} is not supported by
32001 Use of this packet is controlled by the @code{set remote pass-signals}
32002 command (@pxref{Remote Configuration, set remote pass-signals}).
32003 This packet is not probed by default; the remote stub must request it,
32004 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32006 @item qRcmd,@var{command}
32007 @cindex execute remote command, remote request
32008 @cindex @samp{qRcmd} packet
32009 @var{command} (hex encoded) is passed to the local interpreter for
32010 execution. Invalid commands should be reported using the output
32011 string. Before the final result packet, the target may also respond
32012 with a number of intermediate @samp{O@var{output}} console output
32013 packets. @emph{Implementors should note that providing access to a
32014 stubs's interpreter may have security implications}.
32019 A command response with no output.
32021 A command response with the hex encoded output string @var{OUTPUT}.
32023 Indicate a badly formed request.
32025 An empty reply indicates that @samp{qRcmd} is not recognized.
32028 (Note that the @code{qRcmd} packet's name is separated from the
32029 command by a @samp{,}, not a @samp{:}, contrary to the naming
32030 conventions above. Please don't use this packet as a model for new
32033 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
32034 @cindex searching memory, in remote debugging
32035 @cindex @samp{qSearch:memory} packet
32036 @anchor{qSearch memory}
32037 Search @var{length} bytes at @var{address} for @var{search-pattern}.
32038 @var{address} and @var{length} are encoded in hex.
32039 @var{search-pattern} is a sequence of bytes, hex encoded.
32044 The pattern was not found.
32046 The pattern was found at @var{address}.
32048 A badly formed request or an error was encountered while searching memory.
32050 An empty reply indicates that @samp{qSearch:memory} is not recognized.
32053 @item QStartNoAckMode
32054 @cindex @samp{QStartNoAckMode} packet
32055 @anchor{QStartNoAckMode}
32056 Request that the remote stub disable the normal @samp{+}/@samp{-}
32057 protocol acknowledgments (@pxref{Packet Acknowledgment}).
32062 The stub has switched to no-acknowledgment mode.
32063 @value{GDBN} acknowledges this reponse,
32064 but neither the stub nor @value{GDBN} shall send or expect further
32065 @samp{+}/@samp{-} acknowledgments in the current connection.
32067 An empty reply indicates that the stub does not support no-acknowledgment mode.
32070 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
32071 @cindex supported packets, remote query
32072 @cindex features of the remote protocol
32073 @cindex @samp{qSupported} packet
32074 @anchor{qSupported}
32075 Tell the remote stub about features supported by @value{GDBN}, and
32076 query the stub for features it supports. This packet allows
32077 @value{GDBN} and the remote stub to take advantage of each others'
32078 features. @samp{qSupported} also consolidates multiple feature probes
32079 at startup, to improve @value{GDBN} performance---a single larger
32080 packet performs better than multiple smaller probe packets on
32081 high-latency links. Some features may enable behavior which must not
32082 be on by default, e.g.@: because it would confuse older clients or
32083 stubs. Other features may describe packets which could be
32084 automatically probed for, but are not. These features must be
32085 reported before @value{GDBN} will use them. This ``default
32086 unsupported'' behavior is not appropriate for all packets, but it
32087 helps to keep the initial connection time under control with new
32088 versions of @value{GDBN} which support increasing numbers of packets.
32092 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
32093 The stub supports or does not support each returned @var{stubfeature},
32094 depending on the form of each @var{stubfeature} (see below for the
32097 An empty reply indicates that @samp{qSupported} is not recognized,
32098 or that no features needed to be reported to @value{GDBN}.
32101 The allowed forms for each feature (either a @var{gdbfeature} in the
32102 @samp{qSupported} packet, or a @var{stubfeature} in the response)
32106 @item @var{name}=@var{value}
32107 The remote protocol feature @var{name} is supported, and associated
32108 with the specified @var{value}. The format of @var{value} depends
32109 on the feature, but it must not include a semicolon.
32111 The remote protocol feature @var{name} is supported, and does not
32112 need an associated value.
32114 The remote protocol feature @var{name} is not supported.
32116 The remote protocol feature @var{name} may be supported, and
32117 @value{GDBN} should auto-detect support in some other way when it is
32118 needed. This form will not be used for @var{gdbfeature} notifications,
32119 but may be used for @var{stubfeature} responses.
32122 Whenever the stub receives a @samp{qSupported} request, the
32123 supplied set of @value{GDBN} features should override any previous
32124 request. This allows @value{GDBN} to put the stub in a known
32125 state, even if the stub had previously been communicating with
32126 a different version of @value{GDBN}.
32128 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
32133 This feature indicates whether @value{GDBN} supports multiprocess
32134 extensions to the remote protocol. @value{GDBN} does not use such
32135 extensions unless the stub also reports that it supports them by
32136 including @samp{multiprocess+} in its @samp{qSupported} reply.
32137 @xref{multiprocess extensions}, for details.
32140 This feature indicates that @value{GDBN} supports the XML target
32141 description. If the stub sees @samp{xmlRegisters=} with target
32142 specific strings separated by a comma, it will report register
32146 This feature indicates whether @value{GDBN} supports the
32147 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
32148 instruction reply packet}).
32151 Stubs should ignore any unknown values for
32152 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
32153 packet supports receiving packets of unlimited length (earlier
32154 versions of @value{GDBN} may reject overly long responses). Additional values
32155 for @var{gdbfeature} may be defined in the future to let the stub take
32156 advantage of new features in @value{GDBN}, e.g.@: incompatible
32157 improvements in the remote protocol---the @samp{multiprocess} feature is
32158 an example of such a feature. The stub's reply should be independent
32159 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
32160 describes all the features it supports, and then the stub replies with
32161 all the features it supports.
32163 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
32164 responses, as long as each response uses one of the standard forms.
32166 Some features are flags. A stub which supports a flag feature
32167 should respond with a @samp{+} form response. Other features
32168 require values, and the stub should respond with an @samp{=}
32171 Each feature has a default value, which @value{GDBN} will use if
32172 @samp{qSupported} is not available or if the feature is not mentioned
32173 in the @samp{qSupported} response. The default values are fixed; a
32174 stub is free to omit any feature responses that match the defaults.
32176 Not all features can be probed, but for those which can, the probing
32177 mechanism is useful: in some cases, a stub's internal
32178 architecture may not allow the protocol layer to know some information
32179 about the underlying target in advance. This is especially common in
32180 stubs which may be configured for multiple targets.
32182 These are the currently defined stub features and their properties:
32184 @multitable @columnfractions 0.35 0.2 0.12 0.2
32185 @c NOTE: The first row should be @headitem, but we do not yet require
32186 @c a new enough version of Texinfo (4.7) to use @headitem.
32188 @tab Value Required
32192 @item @samp{PacketSize}
32197 @item @samp{qXfer:auxv:read}
32202 @item @samp{qXfer:features:read}
32207 @item @samp{qXfer:libraries:read}
32212 @item @samp{qXfer:memory-map:read}
32217 @item @samp{qXfer:sdata:read}
32222 @item @samp{qXfer:spu:read}
32227 @item @samp{qXfer:spu:write}
32232 @item @samp{qXfer:siginfo:read}
32237 @item @samp{qXfer:siginfo:write}
32242 @item @samp{qXfer:threads:read}
32248 @item @samp{QNonStop}
32253 @item @samp{QPassSignals}
32258 @item @samp{QStartNoAckMode}
32263 @item @samp{multiprocess}
32268 @item @samp{ConditionalTracepoints}
32273 @item @samp{ReverseContinue}
32278 @item @samp{ReverseStep}
32283 @item @samp{TracepointSource}
32288 @item @samp{QAllow}
32295 These are the currently defined stub features, in more detail:
32298 @cindex packet size, remote protocol
32299 @item PacketSize=@var{bytes}
32300 The remote stub can accept packets up to at least @var{bytes} in
32301 length. @value{GDBN} will send packets up to this size for bulk
32302 transfers, and will never send larger packets. This is a limit on the
32303 data characters in the packet, including the frame and checksum.
32304 There is no trailing NUL byte in a remote protocol packet; if the stub
32305 stores packets in a NUL-terminated format, it should allow an extra
32306 byte in its buffer for the NUL. If this stub feature is not supported,
32307 @value{GDBN} guesses based on the size of the @samp{g} packet response.
32309 @item qXfer:auxv:read
32310 The remote stub understands the @samp{qXfer:auxv:read} packet
32311 (@pxref{qXfer auxiliary vector read}).
32313 @item qXfer:features:read
32314 The remote stub understands the @samp{qXfer:features:read} packet
32315 (@pxref{qXfer target description read}).
32317 @item qXfer:libraries:read
32318 The remote stub understands the @samp{qXfer:libraries:read} packet
32319 (@pxref{qXfer library list read}).
32321 @item qXfer:memory-map:read
32322 The remote stub understands the @samp{qXfer:memory-map:read} packet
32323 (@pxref{qXfer memory map read}).
32325 @item qXfer:sdata:read
32326 The remote stub understands the @samp{qXfer:sdata:read} packet
32327 (@pxref{qXfer sdata read}).
32329 @item qXfer:spu:read
32330 The remote stub understands the @samp{qXfer:spu:read} packet
32331 (@pxref{qXfer spu read}).
32333 @item qXfer:spu:write
32334 The remote stub understands the @samp{qXfer:spu:write} packet
32335 (@pxref{qXfer spu write}).
32337 @item qXfer:siginfo:read
32338 The remote stub understands the @samp{qXfer:siginfo:read} packet
32339 (@pxref{qXfer siginfo read}).
32341 @item qXfer:siginfo:write
32342 The remote stub understands the @samp{qXfer:siginfo:write} packet
32343 (@pxref{qXfer siginfo write}).
32345 @item qXfer:threads:read
32346 The remote stub understands the @samp{qXfer:threads:read} packet
32347 (@pxref{qXfer threads read}).
32350 The remote stub understands the @samp{QNonStop} packet
32351 (@pxref{QNonStop}).
32354 The remote stub understands the @samp{QPassSignals} packet
32355 (@pxref{QPassSignals}).
32357 @item QStartNoAckMode
32358 The remote stub understands the @samp{QStartNoAckMode} packet and
32359 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
32362 @anchor{multiprocess extensions}
32363 @cindex multiprocess extensions, in remote protocol
32364 The remote stub understands the multiprocess extensions to the remote
32365 protocol syntax. The multiprocess extensions affect the syntax of
32366 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
32367 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
32368 replies. Note that reporting this feature indicates support for the
32369 syntactic extensions only, not that the stub necessarily supports
32370 debugging of more than one process at a time. The stub must not use
32371 multiprocess extensions in packet replies unless @value{GDBN} has also
32372 indicated it supports them in its @samp{qSupported} request.
32374 @item qXfer:osdata:read
32375 The remote stub understands the @samp{qXfer:osdata:read} packet
32376 ((@pxref{qXfer osdata read}).
32378 @item ConditionalTracepoints
32379 The remote stub accepts and implements conditional expressions defined
32380 for tracepoints (@pxref{Tracepoint Conditions}).
32382 @item ReverseContinue
32383 The remote stub accepts and implements the reverse continue packet
32387 The remote stub accepts and implements the reverse step packet
32390 @item TracepointSource
32391 The remote stub understands the @samp{QTDPsrc} packet that supplies
32392 the source form of tracepoint definitions.
32395 The remote stub understands the @samp{QAllow} packet.
32397 @item StaticTracepoint
32398 @cindex static tracepoints, in remote protocol
32399 The remote stub supports static tracepoints.
32404 @cindex symbol lookup, remote request
32405 @cindex @samp{qSymbol} packet
32406 Notify the target that @value{GDBN} is prepared to serve symbol lookup
32407 requests. Accept requests from the target for the values of symbols.
32412 The target does not need to look up any (more) symbols.
32413 @item qSymbol:@var{sym_name}
32414 The target requests the value of symbol @var{sym_name} (hex encoded).
32415 @value{GDBN} may provide the value by using the
32416 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
32420 @item qSymbol:@var{sym_value}:@var{sym_name}
32421 Set the value of @var{sym_name} to @var{sym_value}.
32423 @var{sym_name} (hex encoded) is the name of a symbol whose value the
32424 target has previously requested.
32426 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
32427 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
32433 The target does not need to look up any (more) symbols.
32434 @item qSymbol:@var{sym_name}
32435 The target requests the value of a new symbol @var{sym_name} (hex
32436 encoded). @value{GDBN} will continue to supply the values of symbols
32437 (if available), until the target ceases to request them.
32442 @item QTDisconnected
32449 @xref{Tracepoint Packets}.
32451 @item qThreadExtraInfo,@var{thread-id}
32452 @cindex thread attributes info, remote request
32453 @cindex @samp{qThreadExtraInfo} packet
32454 Obtain a printable string description of a thread's attributes from
32455 the target OS. @var{thread-id} is a thread ID;
32456 see @ref{thread-id syntax}. This
32457 string may contain anything that the target OS thinks is interesting
32458 for @value{GDBN} to tell the user about the thread. The string is
32459 displayed in @value{GDBN}'s @code{info threads} display. Some
32460 examples of possible thread extra info strings are @samp{Runnable}, or
32461 @samp{Blocked on Mutex}.
32465 @item @var{XX}@dots{}
32466 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
32467 comprising the printable string containing the extra information about
32468 the thread's attributes.
32471 (Note that the @code{qThreadExtraInfo} packet's name is separated from
32472 the command by a @samp{,}, not a @samp{:}, contrary to the naming
32473 conventions above. Please don't use this packet as a model for new
32488 @xref{Tracepoint Packets}.
32490 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
32491 @cindex read special object, remote request
32492 @cindex @samp{qXfer} packet
32493 @anchor{qXfer read}
32494 Read uninterpreted bytes from the target's special data area
32495 identified by the keyword @var{object}. Request @var{length} bytes
32496 starting at @var{offset} bytes into the data. The content and
32497 encoding of @var{annex} is specific to @var{object}; it can supply
32498 additional details about what data to access.
32500 Here are the specific requests of this form defined so far. All
32501 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
32502 formats, listed below.
32505 @item qXfer:auxv:read::@var{offset},@var{length}
32506 @anchor{qXfer auxiliary vector read}
32507 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
32508 auxiliary vector}. Note @var{annex} must be empty.
32510 This packet is not probed by default; the remote stub must request it,
32511 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32513 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
32514 @anchor{qXfer target description read}
32515 Access the @dfn{target description}. @xref{Target Descriptions}. The
32516 annex specifies which XML document to access. The main description is
32517 always loaded from the @samp{target.xml} annex.
32519 This packet is not probed by default; the remote stub must request it,
32520 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32522 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
32523 @anchor{qXfer library list read}
32524 Access the target's list of loaded libraries. @xref{Library List Format}.
32525 The annex part of the generic @samp{qXfer} packet must be empty
32526 (@pxref{qXfer read}).
32528 Targets which maintain a list of libraries in the program's memory do
32529 not need to implement this packet; it is designed for platforms where
32530 the operating system manages the list of loaded libraries.
32532 This packet is not probed by default; the remote stub must request it,
32533 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32535 @item qXfer:memory-map:read::@var{offset},@var{length}
32536 @anchor{qXfer memory map read}
32537 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
32538 annex part of the generic @samp{qXfer} packet must be empty
32539 (@pxref{qXfer read}).
32541 This packet is not probed by default; the remote stub must request it,
32542 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32544 @item qXfer:sdata:read::@var{offset},@var{length}
32545 @anchor{qXfer sdata read}
32547 Read contents of the extra collected static tracepoint marker
32548 information. The annex part of the generic @samp{qXfer} packet must
32549 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
32552 This packet is not probed by default; the remote stub must request it,
32553 by supplying an appropriate @samp{qSupported} response
32554 (@pxref{qSupported}).
32556 @item qXfer:siginfo:read::@var{offset},@var{length}
32557 @anchor{qXfer siginfo read}
32558 Read contents of the extra signal information on the target
32559 system. The annex part of the generic @samp{qXfer} packet must be
32560 empty (@pxref{qXfer read}).
32562 This packet is not probed by default; the remote stub must request it,
32563 by supplying an appropriate @samp{qSupported} response
32564 (@pxref{qSupported}).
32566 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
32567 @anchor{qXfer spu read}
32568 Read contents of an @code{spufs} file on the target system. The
32569 annex specifies which file to read; it must be of the form
32570 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32571 in the target process, and @var{name} identifes the @code{spufs} file
32572 in that context to be accessed.
32574 This packet is not probed by default; the remote stub must request it,
32575 by supplying an appropriate @samp{qSupported} response
32576 (@pxref{qSupported}).
32578 @item qXfer:threads:read::@var{offset},@var{length}
32579 @anchor{qXfer threads read}
32580 Access the list of threads on target. @xref{Thread List Format}. The
32581 annex part of the generic @samp{qXfer} packet must be empty
32582 (@pxref{qXfer read}).
32584 This packet is not probed by default; the remote stub must request it,
32585 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32587 @item qXfer:osdata:read::@var{offset},@var{length}
32588 @anchor{qXfer osdata read}
32589 Access the target's @dfn{operating system information}.
32590 @xref{Operating System Information}.
32597 Data @var{data} (@pxref{Binary Data}) has been read from the
32598 target. There may be more data at a higher address (although
32599 it is permitted to return @samp{m} even for the last valid
32600 block of data, as long as at least one byte of data was read).
32601 @var{data} may have fewer bytes than the @var{length} in the
32605 Data @var{data} (@pxref{Binary Data}) has been read from the target.
32606 There is no more data to be read. @var{data} may have fewer bytes
32607 than the @var{length} in the request.
32610 The @var{offset} in the request is at the end of the data.
32611 There is no more data to be read.
32614 The request was malformed, or @var{annex} was invalid.
32617 The offset was invalid, or there was an error encountered reading the data.
32618 @var{nn} is a hex-encoded @code{errno} value.
32621 An empty reply indicates the @var{object} string was not recognized by
32622 the stub, or that the object does not support reading.
32625 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
32626 @cindex write data into object, remote request
32627 @anchor{qXfer write}
32628 Write uninterpreted bytes into the target's special data area
32629 identified by the keyword @var{object}, starting at @var{offset} bytes
32630 into the data. @var{data}@dots{} is the binary-encoded data
32631 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
32632 is specific to @var{object}; it can supply additional details about what data
32635 Here are the specific requests of this form defined so far. All
32636 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
32637 formats, listed below.
32640 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
32641 @anchor{qXfer siginfo write}
32642 Write @var{data} to the extra signal information on the target system.
32643 The annex part of the generic @samp{qXfer} packet must be
32644 empty (@pxref{qXfer write}).
32646 This packet is not probed by default; the remote stub must request it,
32647 by supplying an appropriate @samp{qSupported} response
32648 (@pxref{qSupported}).
32650 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
32651 @anchor{qXfer spu write}
32652 Write @var{data} to an @code{spufs} file on the target system. The
32653 annex specifies which file to write; it must be of the form
32654 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32655 in the target process, and @var{name} identifes the @code{spufs} file
32656 in that context to be accessed.
32658 This packet is not probed by default; the remote stub must request it,
32659 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32665 @var{nn} (hex encoded) is the number of bytes written.
32666 This may be fewer bytes than supplied in the request.
32669 The request was malformed, or @var{annex} was invalid.
32672 The offset was invalid, or there was an error encountered writing the data.
32673 @var{nn} is a hex-encoded @code{errno} value.
32676 An empty reply indicates the @var{object} string was not
32677 recognized by the stub, or that the object does not support writing.
32680 @item qXfer:@var{object}:@var{operation}:@dots{}
32681 Requests of this form may be added in the future. When a stub does
32682 not recognize the @var{object} keyword, or its support for
32683 @var{object} does not recognize the @var{operation} keyword, the stub
32684 must respond with an empty packet.
32686 @item qAttached:@var{pid}
32687 @cindex query attached, remote request
32688 @cindex @samp{qAttached} packet
32689 Return an indication of whether the remote server attached to an
32690 existing process or created a new process. When the multiprocess
32691 protocol extensions are supported (@pxref{multiprocess extensions}),
32692 @var{pid} is an integer in hexadecimal format identifying the target
32693 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
32694 the query packet will be simplified as @samp{qAttached}.
32696 This query is used, for example, to know whether the remote process
32697 should be detached or killed when a @value{GDBN} session is ended with
32698 the @code{quit} command.
32703 The remote server attached to an existing process.
32705 The remote server created a new process.
32707 A badly formed request or an error was encountered.
32712 @node Architecture-Specific Protocol Details
32713 @section Architecture-Specific Protocol Details
32715 This section describes how the remote protocol is applied to specific
32716 target architectures. Also see @ref{Standard Target Features}, for
32717 details of XML target descriptions for each architecture.
32721 @subsubsection Breakpoint Kinds
32723 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
32728 16-bit Thumb mode breakpoint.
32731 32-bit Thumb mode (Thumb-2) breakpoint.
32734 32-bit ARM mode breakpoint.
32740 @subsubsection Register Packet Format
32742 The following @code{g}/@code{G} packets have previously been defined.
32743 In the below, some thirty-two bit registers are transferred as
32744 sixty-four bits. Those registers should be zero/sign extended (which?)
32745 to fill the space allocated. Register bytes are transferred in target
32746 byte order. The two nibbles within a register byte are transferred
32747 most-significant - least-significant.
32753 All registers are transferred as thirty-two bit quantities in the order:
32754 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
32755 registers; fsr; fir; fp.
32759 All registers are transferred as sixty-four bit quantities (including
32760 thirty-two bit registers such as @code{sr}). The ordering is the same
32765 @node Tracepoint Packets
32766 @section Tracepoint Packets
32767 @cindex tracepoint packets
32768 @cindex packets, tracepoint
32770 Here we describe the packets @value{GDBN} uses to implement
32771 tracepoints (@pxref{Tracepoints}).
32775 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
32776 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
32777 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
32778 the tracepoint is disabled. @var{step} is the tracepoint's step
32779 count, and @var{pass} is its pass count. If an @samp{F} is present,
32780 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
32781 the number of bytes that the target should copy elsewhere to make room
32782 for the tracepoint. If an @samp{X} is present, it introduces a
32783 tracepoint condition, which consists of a hexadecimal length, followed
32784 by a comma and hex-encoded bytes, in a manner similar to action
32785 encodings as described below. If the trailing @samp{-} is present,
32786 further @samp{QTDP} packets will follow to specify this tracepoint's
32792 The packet was understood and carried out.
32794 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
32796 The packet was not recognized.
32799 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
32800 Define actions to be taken when a tracepoint is hit. @var{n} and
32801 @var{addr} must be the same as in the initial @samp{QTDP} packet for
32802 this tracepoint. This packet may only be sent immediately after
32803 another @samp{QTDP} packet that ended with a @samp{-}. If the
32804 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
32805 specifying more actions for this tracepoint.
32807 In the series of action packets for a given tracepoint, at most one
32808 can have an @samp{S} before its first @var{action}. If such a packet
32809 is sent, it and the following packets define ``while-stepping''
32810 actions. Any prior packets define ordinary actions --- that is, those
32811 taken when the tracepoint is first hit. If no action packet has an
32812 @samp{S}, then all the packets in the series specify ordinary
32813 tracepoint actions.
32815 The @samp{@var{action}@dots{}} portion of the packet is a series of
32816 actions, concatenated without separators. Each action has one of the
32822 Collect the registers whose bits are set in @var{mask}. @var{mask} is
32823 a hexadecimal number whose @var{i}'th bit is set if register number
32824 @var{i} should be collected. (The least significant bit is numbered
32825 zero.) Note that @var{mask} may be any number of digits long; it may
32826 not fit in a 32-bit word.
32828 @item M @var{basereg},@var{offset},@var{len}
32829 Collect @var{len} bytes of memory starting at the address in register
32830 number @var{basereg}, plus @var{offset}. If @var{basereg} is
32831 @samp{-1}, then the range has a fixed address: @var{offset} is the
32832 address of the lowest byte to collect. The @var{basereg},
32833 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
32834 values (the @samp{-1} value for @var{basereg} is a special case).
32836 @item X @var{len},@var{expr}
32837 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
32838 it directs. @var{expr} is an agent expression, as described in
32839 @ref{Agent Expressions}. Each byte of the expression is encoded as a
32840 two-digit hex number in the packet; @var{len} is the number of bytes
32841 in the expression (and thus one-half the number of hex digits in the
32846 Any number of actions may be packed together in a single @samp{QTDP}
32847 packet, as long as the packet does not exceed the maximum packet
32848 length (400 bytes, for many stubs). There may be only one @samp{R}
32849 action per tracepoint, and it must precede any @samp{M} or @samp{X}
32850 actions. Any registers referred to by @samp{M} and @samp{X} actions
32851 must be collected by a preceding @samp{R} action. (The
32852 ``while-stepping'' actions are treated as if they were attached to a
32853 separate tracepoint, as far as these restrictions are concerned.)
32858 The packet was understood and carried out.
32860 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
32862 The packet was not recognized.
32865 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
32866 @cindex @samp{QTDPsrc} packet
32867 Specify a source string of tracepoint @var{n} at address @var{addr}.
32868 This is useful to get accurate reproduction of the tracepoints
32869 originally downloaded at the beginning of the trace run. @var{type}
32870 is the name of the tracepoint part, such as @samp{cond} for the
32871 tracepoint's conditional expression (see below for a list of types), while
32872 @var{bytes} is the string, encoded in hexadecimal.
32874 @var{start} is the offset of the @var{bytes} within the overall source
32875 string, while @var{slen} is the total length of the source string.
32876 This is intended for handling source strings that are longer than will
32877 fit in a single packet.
32878 @c Add detailed example when this info is moved into a dedicated
32879 @c tracepoint descriptions section.
32881 The available string types are @samp{at} for the location,
32882 @samp{cond} for the conditional, and @samp{cmd} for an action command.
32883 @value{GDBN} sends a separate packet for each command in the action
32884 list, in the same order in which the commands are stored in the list.
32886 The target does not need to do anything with source strings except
32887 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
32890 Although this packet is optional, and @value{GDBN} will only send it
32891 if the target replies with @samp{TracepointSource} @xref{General
32892 Query Packets}, it makes both disconnected tracing and trace files
32893 much easier to use. Otherwise the user must be careful that the
32894 tracepoints in effect while looking at trace frames are identical to
32895 the ones in effect during the trace run; even a small discrepancy
32896 could cause @samp{tdump} not to work, or a particular trace frame not
32899 @item QTDV:@var{n}:@var{value}
32900 @cindex define trace state variable, remote request
32901 @cindex @samp{QTDV} packet
32902 Create a new trace state variable, number @var{n}, with an initial
32903 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
32904 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
32905 the option of not using this packet for initial values of zero; the
32906 target should simply create the trace state variables as they are
32907 mentioned in expressions.
32909 @item QTFrame:@var{n}
32910 Select the @var{n}'th tracepoint frame from the buffer, and use the
32911 register and memory contents recorded there to answer subsequent
32912 request packets from @value{GDBN}.
32914 A successful reply from the stub indicates that the stub has found the
32915 requested frame. The response is a series of parts, concatenated
32916 without separators, describing the frame we selected. Each part has
32917 one of the following forms:
32921 The selected frame is number @var{n} in the trace frame buffer;
32922 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
32923 was no frame matching the criteria in the request packet.
32926 The selected trace frame records a hit of tracepoint number @var{t};
32927 @var{t} is a hexadecimal number.
32931 @item QTFrame:pc:@var{addr}
32932 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32933 currently selected frame whose PC is @var{addr};
32934 @var{addr} is a hexadecimal number.
32936 @item QTFrame:tdp:@var{t}
32937 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32938 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
32939 is a hexadecimal number.
32941 @item QTFrame:range:@var{start}:@var{end}
32942 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32943 currently selected frame whose PC is between @var{start} (inclusive)
32944 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
32947 @item QTFrame:outside:@var{start}:@var{end}
32948 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
32949 frame @emph{outside} the given range of addresses (exclusive).
32952 Begin the tracepoint experiment. Begin collecting data from
32953 tracepoint hits in the trace frame buffer. This packet supports the
32954 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
32955 instruction reply packet}).
32958 End the tracepoint experiment. Stop collecting trace frames.
32961 Clear the table of tracepoints, and empty the trace frame buffer.
32963 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
32964 Establish the given ranges of memory as ``transparent''. The stub
32965 will answer requests for these ranges from memory's current contents,
32966 if they were not collected as part of the tracepoint hit.
32968 @value{GDBN} uses this to mark read-only regions of memory, like those
32969 containing program code. Since these areas never change, they should
32970 still have the same contents they did when the tracepoint was hit, so
32971 there's no reason for the stub to refuse to provide their contents.
32973 @item QTDisconnected:@var{value}
32974 Set the choice to what to do with the tracing run when @value{GDBN}
32975 disconnects from the target. A @var{value} of 1 directs the target to
32976 continue the tracing run, while 0 tells the target to stop tracing if
32977 @value{GDBN} is no longer in the picture.
32980 Ask the stub if there is a trace experiment running right now.
32982 The reply has the form:
32986 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
32987 @var{running} is a single digit @code{1} if the trace is presently
32988 running, or @code{0} if not. It is followed by semicolon-separated
32989 optional fields that an agent may use to report additional status.
32993 If the trace is not running, the agent may report any of several
32994 explanations as one of the optional fields:
32999 No trace has been run yet.
33002 The trace was stopped by a user-originated stop command.
33005 The trace stopped because the trace buffer filled up.
33007 @item tdisconnected:0
33008 The trace stopped because @value{GDBN} disconnected from the target.
33010 @item tpasscount:@var{tpnum}
33011 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
33013 @item terror:@var{text}:@var{tpnum}
33014 The trace stopped because tracepoint @var{tpnum} had an error. The
33015 string @var{text} is available to describe the nature of the error
33016 (for instance, a divide by zero in the condition expression).
33017 @var{text} is hex encoded.
33020 The trace stopped for some other reason.
33024 Additional optional fields supply statistical and other information.
33025 Although not required, they are extremely useful for users monitoring
33026 the progress of a trace run. If a trace has stopped, and these
33027 numbers are reported, they must reflect the state of the just-stopped
33032 @item tframes:@var{n}
33033 The number of trace frames in the buffer.
33035 @item tcreated:@var{n}
33036 The total number of trace frames created during the run. This may
33037 be larger than the trace frame count, if the buffer is circular.
33039 @item tsize:@var{n}
33040 The total size of the trace buffer, in bytes.
33042 @item tfree:@var{n}
33043 The number of bytes still unused in the buffer.
33045 @item circular:@var{n}
33046 The value of the circular trace buffer flag. @code{1} means that the
33047 trace buffer is circular and old trace frames will be discarded if
33048 necessary to make room, @code{0} means that the trace buffer is linear
33051 @item disconn:@var{n}
33052 The value of the disconnected tracing flag. @code{1} means that
33053 tracing will continue after @value{GDBN} disconnects, @code{0} means
33054 that the trace run will stop.
33058 @item qTV:@var{var}
33059 @cindex trace state variable value, remote request
33060 @cindex @samp{qTV} packet
33061 Ask the stub for the value of the trace state variable number @var{var}.
33066 The value of the variable is @var{value}. This will be the current
33067 value of the variable if the user is examining a running target, or a
33068 saved value if the variable was collected in the trace frame that the
33069 user is looking at. Note that multiple requests may result in
33070 different reply values, such as when requesting values while the
33071 program is running.
33074 The value of the variable is unknown. This would occur, for example,
33075 if the user is examining a trace frame in which the requested variable
33081 These packets request data about tracepoints that are being used by
33082 the target. @value{GDBN} sends @code{qTfP} to get the first piece
33083 of data, and multiple @code{qTsP} to get additional pieces. Replies
33084 to these packets generally take the form of the @code{QTDP} packets
33085 that define tracepoints. (FIXME add detailed syntax)
33089 These packets request data about trace state variables that are on the
33090 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
33091 and multiple @code{qTsV} to get additional variables. Replies to
33092 these packets follow the syntax of the @code{QTDV} packets that define
33093 trace state variables.
33097 These packets request data about static tracepoint markers that exist
33098 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
33099 first piece of data, and multiple @code{qTsSTM} to get additional
33100 pieces. Replies to these packets take the following form:
33104 @item m @var{address}:@var{id}:@var{extra}
33106 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
33107 a comma-separated list of markers
33109 (lower case letter @samp{L}) denotes end of list.
33111 An error occurred. @var{nn} are hex digits.
33113 An empty reply indicates that the request is not supported by the
33117 @var{address} is encoded in hex.
33118 @var{id} and @var{extra} are strings encoded in hex.
33120 In response to each query, the target will reply with a list of one or
33121 more markers, separated by commas. @value{GDBN} will respond to each
33122 reply with a request for more markers (using the @samp{qs} form of the
33123 query), until the target responds with @samp{l} (lower-case ell, for
33126 @item qTSTMat:@var{address}
33127 This packets requests data about static tracepoint markers in the
33128 target program at @var{address}. Replies to this packet follow the
33129 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
33130 tracepoint markers.
33132 @item QTSave:@var{filename}
33133 This packet directs the target to save trace data to the file name
33134 @var{filename} in the target's filesystem. @var{filename} is encoded
33135 as a hex string; the interpretation of the file name (relative vs
33136 absolute, wild cards, etc) is up to the target.
33138 @item qTBuffer:@var{offset},@var{len}
33139 Return up to @var{len} bytes of the current contents of trace buffer,
33140 starting at @var{offset}. The trace buffer is treated as if it were
33141 a contiguous collection of traceframes, as per the trace file format.
33142 The reply consists as many hex-encoded bytes as the target can deliver
33143 in a packet; it is not an error to return fewer than were asked for.
33144 A reply consisting of just @code{l} indicates that no bytes are
33147 @item QTBuffer:circular:@var{value}
33148 This packet directs the target to use a circular trace buffer if
33149 @var{value} is 1, or a linear buffer if the value is 0.
33153 @subsection Relocate instruction reply packet
33154 When installing fast tracepoints in memory, the target may need to
33155 relocate the instruction currently at the tracepoint address to a
33156 different address in memory. For most instructions, a simple copy is
33157 enough, but, for example, call instructions that implicitly push the
33158 return address on the stack, and relative branches or other
33159 PC-relative instructions require offset adjustment, so that the effect
33160 of executing the instruction at a different address is the same as if
33161 it had executed in the original location.
33163 In response to several of the tracepoint packets, the target may also
33164 respond with a number of intermediate @samp{qRelocInsn} request
33165 packets before the final result packet, to have @value{GDBN} handle
33166 this relocation operation. If a packet supports this mechanism, its
33167 documentation will explicitly say so. See for example the above
33168 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
33169 format of the request is:
33172 @item qRelocInsn:@var{from};@var{to}
33174 This requests @value{GDBN} to copy instruction at address @var{from}
33175 to address @var{to}, possibly adjusted so that executing the
33176 instruction at @var{to} has the same effect as executing it at
33177 @var{from}. @value{GDBN} writes the adjusted instruction to target
33178 memory starting at @var{to}.
33183 @item qRelocInsn:@var{adjusted_size}
33184 Informs the stub the relocation is complete. @var{adjusted_size} is
33185 the length in bytes of resulting relocated instruction sequence.
33187 A badly formed request was detected, or an error was encountered while
33188 relocating the instruction.
33191 @node Host I/O Packets
33192 @section Host I/O Packets
33193 @cindex Host I/O, remote protocol
33194 @cindex file transfer, remote protocol
33196 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
33197 operations on the far side of a remote link. For example, Host I/O is
33198 used to upload and download files to a remote target with its own
33199 filesystem. Host I/O uses the same constant values and data structure
33200 layout as the target-initiated File-I/O protocol. However, the
33201 Host I/O packets are structured differently. The target-initiated
33202 protocol relies on target memory to store parameters and buffers.
33203 Host I/O requests are initiated by @value{GDBN}, and the
33204 target's memory is not involved. @xref{File-I/O Remote Protocol
33205 Extension}, for more details on the target-initiated protocol.
33207 The Host I/O request packets all encode a single operation along with
33208 its arguments. They have this format:
33212 @item vFile:@var{operation}: @var{parameter}@dots{}
33213 @var{operation} is the name of the particular request; the target
33214 should compare the entire packet name up to the second colon when checking
33215 for a supported operation. The format of @var{parameter} depends on
33216 the operation. Numbers are always passed in hexadecimal. Negative
33217 numbers have an explicit minus sign (i.e.@: two's complement is not
33218 used). Strings (e.g.@: filenames) are encoded as a series of
33219 hexadecimal bytes. The last argument to a system call may be a
33220 buffer of escaped binary data (@pxref{Binary Data}).
33224 The valid responses to Host I/O packets are:
33228 @item F @var{result} [, @var{errno}] [; @var{attachment}]
33229 @var{result} is the integer value returned by this operation, usually
33230 non-negative for success and -1 for errors. If an error has occured,
33231 @var{errno} will be included in the result. @var{errno} will have a
33232 value defined by the File-I/O protocol (@pxref{Errno Values}). For
33233 operations which return data, @var{attachment} supplies the data as a
33234 binary buffer. Binary buffers in response packets are escaped in the
33235 normal way (@pxref{Binary Data}). See the individual packet
33236 documentation for the interpretation of @var{result} and
33240 An empty response indicates that this operation is not recognized.
33244 These are the supported Host I/O operations:
33247 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
33248 Open a file at @var{pathname} and return a file descriptor for it, or
33249 return -1 if an error occurs. @var{pathname} is a string,
33250 @var{flags} is an integer indicating a mask of open flags
33251 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
33252 of mode bits to use if the file is created (@pxref{mode_t Values}).
33253 @xref{open}, for details of the open flags and mode values.
33255 @item vFile:close: @var{fd}
33256 Close the open file corresponding to @var{fd} and return 0, or
33257 -1 if an error occurs.
33259 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
33260 Read data from the open file corresponding to @var{fd}. Up to
33261 @var{count} bytes will be read from the file, starting at @var{offset}
33262 relative to the start of the file. The target may read fewer bytes;
33263 common reasons include packet size limits and an end-of-file
33264 condition. The number of bytes read is returned. Zero should only be
33265 returned for a successful read at the end of the file, or if
33266 @var{count} was zero.
33268 The data read should be returned as a binary attachment on success.
33269 If zero bytes were read, the response should include an empty binary
33270 attachment (i.e.@: a trailing semicolon). The return value is the
33271 number of target bytes read; the binary attachment may be longer if
33272 some characters were escaped.
33274 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
33275 Write @var{data} (a binary buffer) to the open file corresponding
33276 to @var{fd}. Start the write at @var{offset} from the start of the
33277 file. Unlike many @code{write} system calls, there is no
33278 separate @var{count} argument; the length of @var{data} in the
33279 packet is used. @samp{vFile:write} returns the number of bytes written,
33280 which may be shorter than the length of @var{data}, or -1 if an
33283 @item vFile:unlink: @var{pathname}
33284 Delete the file at @var{pathname} on the target. Return 0,
33285 or -1 if an error occurs. @var{pathname} is a string.
33290 @section Interrupts
33291 @cindex interrupts (remote protocol)
33293 When a program on the remote target is running, @value{GDBN} may
33294 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
33295 a @code{BREAK} followed by @code{g},
33296 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
33298 The precise meaning of @code{BREAK} is defined by the transport
33299 mechanism and may, in fact, be undefined. @value{GDBN} does not
33300 currently define a @code{BREAK} mechanism for any of the network
33301 interfaces except for TCP, in which case @value{GDBN} sends the
33302 @code{telnet} BREAK sequence.
33304 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
33305 transport mechanisms. It is represented by sending the single byte
33306 @code{0x03} without any of the usual packet overhead described in
33307 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
33308 transmitted as part of a packet, it is considered to be packet data
33309 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
33310 (@pxref{X packet}), used for binary downloads, may include an unescaped
33311 @code{0x03} as part of its packet.
33313 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
33314 When Linux kernel receives this sequence from serial port,
33315 it stops execution and connects to gdb.
33317 Stubs are not required to recognize these interrupt mechanisms and the
33318 precise meaning associated with receipt of the interrupt is
33319 implementation defined. If the target supports debugging of multiple
33320 threads and/or processes, it should attempt to interrupt all
33321 currently-executing threads and processes.
33322 If the stub is successful at interrupting the
33323 running program, it should send one of the stop
33324 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
33325 of successfully stopping the program in all-stop mode, and a stop reply
33326 for each stopped thread in non-stop mode.
33327 Interrupts received while the
33328 program is stopped are discarded.
33330 @node Notification Packets
33331 @section Notification Packets
33332 @cindex notification packets
33333 @cindex packets, notification
33335 The @value{GDBN} remote serial protocol includes @dfn{notifications},
33336 packets that require no acknowledgment. Both the GDB and the stub
33337 may send notifications (although the only notifications defined at
33338 present are sent by the stub). Notifications carry information
33339 without incurring the round-trip latency of an acknowledgment, and so
33340 are useful for low-impact communications where occasional packet loss
33343 A notification packet has the form @samp{% @var{data} #
33344 @var{checksum}}, where @var{data} is the content of the notification,
33345 and @var{checksum} is a checksum of @var{data}, computed and formatted
33346 as for ordinary @value{GDBN} packets. A notification's @var{data}
33347 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
33348 receiving a notification, the recipient sends no @samp{+} or @samp{-}
33349 to acknowledge the notification's receipt or to report its corruption.
33351 Every notification's @var{data} begins with a name, which contains no
33352 colon characters, followed by a colon character.
33354 Recipients should silently ignore corrupted notifications and
33355 notifications they do not understand. Recipients should restart
33356 timeout periods on receipt of a well-formed notification, whether or
33357 not they understand it.
33359 Senders should only send the notifications described here when this
33360 protocol description specifies that they are permitted. In the
33361 future, we may extend the protocol to permit existing notifications in
33362 new contexts; this rule helps older senders avoid confusing newer
33365 (Older versions of @value{GDBN} ignore bytes received until they see
33366 the @samp{$} byte that begins an ordinary packet, so new stubs may
33367 transmit notifications without fear of confusing older clients. There
33368 are no notifications defined for @value{GDBN} to send at the moment, but we
33369 assume that most older stubs would ignore them, as well.)
33371 The following notification packets from the stub to @value{GDBN} are
33375 @item Stop: @var{reply}
33376 Report an asynchronous stop event in non-stop mode.
33377 The @var{reply} has the form of a stop reply, as
33378 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
33379 for information on how these notifications are acknowledged by
33383 @node Remote Non-Stop
33384 @section Remote Protocol Support for Non-Stop Mode
33386 @value{GDBN}'s remote protocol supports non-stop debugging of
33387 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
33388 supports non-stop mode, it should report that to @value{GDBN} by including
33389 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
33391 @value{GDBN} typically sends a @samp{QNonStop} packet only when
33392 establishing a new connection with the stub. Entering non-stop mode
33393 does not alter the state of any currently-running threads, but targets
33394 must stop all threads in any already-attached processes when entering
33395 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
33396 probe the target state after a mode change.
33398 In non-stop mode, when an attached process encounters an event that
33399 would otherwise be reported with a stop reply, it uses the
33400 asynchronous notification mechanism (@pxref{Notification Packets}) to
33401 inform @value{GDBN}. In contrast to all-stop mode, where all threads
33402 in all processes are stopped when a stop reply is sent, in non-stop
33403 mode only the thread reporting the stop event is stopped. That is,
33404 when reporting a @samp{S} or @samp{T} response to indicate completion
33405 of a step operation, hitting a breakpoint, or a fault, only the
33406 affected thread is stopped; any other still-running threads continue
33407 to run. When reporting a @samp{W} or @samp{X} response, all running
33408 threads belonging to other attached processes continue to run.
33410 Only one stop reply notification at a time may be pending; if
33411 additional stop events occur before @value{GDBN} has acknowledged the
33412 previous notification, they must be queued by the stub for later
33413 synchronous transmission in response to @samp{vStopped} packets from
33414 @value{GDBN}. Because the notification mechanism is unreliable,
33415 the stub is permitted to resend a stop reply notification
33416 if it believes @value{GDBN} may not have received it. @value{GDBN}
33417 ignores additional stop reply notifications received before it has
33418 finished processing a previous notification and the stub has completed
33419 sending any queued stop events.
33421 Otherwise, @value{GDBN} must be prepared to receive a stop reply
33422 notification at any time. Specifically, they may appear when
33423 @value{GDBN} is not otherwise reading input from the stub, or when
33424 @value{GDBN} is expecting to read a normal synchronous response or a
33425 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
33426 Notification packets are distinct from any other communication from
33427 the stub so there is no ambiguity.
33429 After receiving a stop reply notification, @value{GDBN} shall
33430 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
33431 as a regular, synchronous request to the stub. Such acknowledgment
33432 is not required to happen immediately, as @value{GDBN} is permitted to
33433 send other, unrelated packets to the stub first, which the stub should
33436 Upon receiving a @samp{vStopped} packet, if the stub has other queued
33437 stop events to report to @value{GDBN}, it shall respond by sending a
33438 normal stop reply response. @value{GDBN} shall then send another
33439 @samp{vStopped} packet to solicit further responses; again, it is
33440 permitted to send other, unrelated packets as well which the stub
33441 should process normally.
33443 If the stub receives a @samp{vStopped} packet and there are no
33444 additional stop events to report, the stub shall return an @samp{OK}
33445 response. At this point, if further stop events occur, the stub shall
33446 send a new stop reply notification, @value{GDBN} shall accept the
33447 notification, and the process shall be repeated.
33449 In non-stop mode, the target shall respond to the @samp{?} packet as
33450 follows. First, any incomplete stop reply notification/@samp{vStopped}
33451 sequence in progress is abandoned. The target must begin a new
33452 sequence reporting stop events for all stopped threads, whether or not
33453 it has previously reported those events to @value{GDBN}. The first
33454 stop reply is sent as a synchronous reply to the @samp{?} packet, and
33455 subsequent stop replies are sent as responses to @samp{vStopped} packets
33456 using the mechanism described above. The target must not send
33457 asynchronous stop reply notifications until the sequence is complete.
33458 If all threads are running when the target receives the @samp{?} packet,
33459 or if the target is not attached to any process, it shall respond
33462 @node Packet Acknowledgment
33463 @section Packet Acknowledgment
33465 @cindex acknowledgment, for @value{GDBN} remote
33466 @cindex packet acknowledgment, for @value{GDBN} remote
33467 By default, when either the host or the target machine receives a packet,
33468 the first response expected is an acknowledgment: either @samp{+} (to indicate
33469 the package was received correctly) or @samp{-} (to request retransmission).
33470 This mechanism allows the @value{GDBN} remote protocol to operate over
33471 unreliable transport mechanisms, such as a serial line.
33473 In cases where the transport mechanism is itself reliable (such as a pipe or
33474 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
33475 It may be desirable to disable them in that case to reduce communication
33476 overhead, or for other reasons. This can be accomplished by means of the
33477 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
33479 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
33480 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
33481 and response format still includes the normal checksum, as described in
33482 @ref{Overview}, but the checksum may be ignored by the receiver.
33484 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
33485 no-acknowledgment mode, it should report that to @value{GDBN}
33486 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
33487 @pxref{qSupported}.
33488 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
33489 disabled via the @code{set remote noack-packet off} command
33490 (@pxref{Remote Configuration}),
33491 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
33492 Only then may the stub actually turn off packet acknowledgments.
33493 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
33494 response, which can be safely ignored by the stub.
33496 Note that @code{set remote noack-packet} command only affects negotiation
33497 between @value{GDBN} and the stub when subsequent connections are made;
33498 it does not affect the protocol acknowledgment state for any current
33500 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
33501 new connection is established,
33502 there is also no protocol request to re-enable the acknowledgments
33503 for the current connection, once disabled.
33508 Example sequence of a target being re-started. Notice how the restart
33509 does not get any direct output:
33514 @emph{target restarts}
33517 <- @code{T001:1234123412341234}
33521 Example sequence of a target being stepped by a single instruction:
33524 -> @code{G1445@dots{}}
33529 <- @code{T001:1234123412341234}
33533 <- @code{1455@dots{}}
33537 @node File-I/O Remote Protocol Extension
33538 @section File-I/O Remote Protocol Extension
33539 @cindex File-I/O remote protocol extension
33542 * File-I/O Overview::
33543 * Protocol Basics::
33544 * The F Request Packet::
33545 * The F Reply Packet::
33546 * The Ctrl-C Message::
33548 * List of Supported Calls::
33549 * Protocol-specific Representation of Datatypes::
33551 * File-I/O Examples::
33554 @node File-I/O Overview
33555 @subsection File-I/O Overview
33556 @cindex file-i/o overview
33558 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
33559 target to use the host's file system and console I/O to perform various
33560 system calls. System calls on the target system are translated into a
33561 remote protocol packet to the host system, which then performs the needed
33562 actions and returns a response packet to the target system.
33563 This simulates file system operations even on targets that lack file systems.
33565 The protocol is defined to be independent of both the host and target systems.
33566 It uses its own internal representation of datatypes and values. Both
33567 @value{GDBN} and the target's @value{GDBN} stub are responsible for
33568 translating the system-dependent value representations into the internal
33569 protocol representations when data is transmitted.
33571 The communication is synchronous. A system call is possible only when
33572 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
33573 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
33574 the target is stopped to allow deterministic access to the target's
33575 memory. Therefore File-I/O is not interruptible by target signals. On
33576 the other hand, it is possible to interrupt File-I/O by a user interrupt
33577 (@samp{Ctrl-C}) within @value{GDBN}.
33579 The target's request to perform a host system call does not finish
33580 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
33581 after finishing the system call, the target returns to continuing the
33582 previous activity (continue, step). No additional continue or step
33583 request from @value{GDBN} is required.
33586 (@value{GDBP}) continue
33587 <- target requests 'system call X'
33588 target is stopped, @value{GDBN} executes system call
33589 -> @value{GDBN} returns result
33590 ... target continues, @value{GDBN} returns to wait for the target
33591 <- target hits breakpoint and sends a Txx packet
33594 The protocol only supports I/O on the console and to regular files on
33595 the host file system. Character or block special devices, pipes,
33596 named pipes, sockets or any other communication method on the host
33597 system are not supported by this protocol.
33599 File I/O is not supported in non-stop mode.
33601 @node Protocol Basics
33602 @subsection Protocol Basics
33603 @cindex protocol basics, file-i/o
33605 The File-I/O protocol uses the @code{F} packet as the request as well
33606 as reply packet. Since a File-I/O system call can only occur when
33607 @value{GDBN} is waiting for a response from the continuing or stepping target,
33608 the File-I/O request is a reply that @value{GDBN} has to expect as a result
33609 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
33610 This @code{F} packet contains all information needed to allow @value{GDBN}
33611 to call the appropriate host system call:
33615 A unique identifier for the requested system call.
33618 All parameters to the system call. Pointers are given as addresses
33619 in the target memory address space. Pointers to strings are given as
33620 pointer/length pair. Numerical values are given as they are.
33621 Numerical control flags are given in a protocol-specific representation.
33625 At this point, @value{GDBN} has to perform the following actions.
33629 If the parameters include pointer values to data needed as input to a
33630 system call, @value{GDBN} requests this data from the target with a
33631 standard @code{m} packet request. This additional communication has to be
33632 expected by the target implementation and is handled as any other @code{m}
33636 @value{GDBN} translates all value from protocol representation to host
33637 representation as needed. Datatypes are coerced into the host types.
33640 @value{GDBN} calls the system call.
33643 It then coerces datatypes back to protocol representation.
33646 If the system call is expected to return data in buffer space specified
33647 by pointer parameters to the call, the data is transmitted to the
33648 target using a @code{M} or @code{X} packet. This packet has to be expected
33649 by the target implementation and is handled as any other @code{M} or @code{X}
33654 Eventually @value{GDBN} replies with another @code{F} packet which contains all
33655 necessary information for the target to continue. This at least contains
33662 @code{errno}, if has been changed by the system call.
33669 After having done the needed type and value coercion, the target continues
33670 the latest continue or step action.
33672 @node The F Request Packet
33673 @subsection The @code{F} Request Packet
33674 @cindex file-i/o request packet
33675 @cindex @code{F} request packet
33677 The @code{F} request packet has the following format:
33680 @item F@var{call-id},@var{parameter@dots{}}
33682 @var{call-id} is the identifier to indicate the host system call to be called.
33683 This is just the name of the function.
33685 @var{parameter@dots{}} are the parameters to the system call.
33686 Parameters are hexadecimal integer values, either the actual values in case
33687 of scalar datatypes, pointers to target buffer space in case of compound
33688 datatypes and unspecified memory areas, or pointer/length pairs in case
33689 of string parameters. These are appended to the @var{call-id} as a
33690 comma-delimited list. All values are transmitted in ASCII
33691 string representation, pointer/length pairs separated by a slash.
33697 @node The F Reply Packet
33698 @subsection The @code{F} Reply Packet
33699 @cindex file-i/o reply packet
33700 @cindex @code{F} reply packet
33702 The @code{F} reply packet has the following format:
33706 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
33708 @var{retcode} is the return code of the system call as hexadecimal value.
33710 @var{errno} is the @code{errno} set by the call, in protocol-specific
33712 This parameter can be omitted if the call was successful.
33714 @var{Ctrl-C flag} is only sent if the user requested a break. In this
33715 case, @var{errno} must be sent as well, even if the call was successful.
33716 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
33723 or, if the call was interrupted before the host call has been performed:
33730 assuming 4 is the protocol-specific representation of @code{EINTR}.
33735 @node The Ctrl-C Message
33736 @subsection The @samp{Ctrl-C} Message
33737 @cindex ctrl-c message, in file-i/o protocol
33739 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
33740 reply packet (@pxref{The F Reply Packet}),
33741 the target should behave as if it had
33742 gotten a break message. The meaning for the target is ``system call
33743 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
33744 (as with a break message) and return to @value{GDBN} with a @code{T02}
33747 It's important for the target to know in which
33748 state the system call was interrupted. There are two possible cases:
33752 The system call hasn't been performed on the host yet.
33755 The system call on the host has been finished.
33759 These two states can be distinguished by the target by the value of the
33760 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
33761 call hasn't been performed. This is equivalent to the @code{EINTR} handling
33762 on POSIX systems. In any other case, the target may presume that the
33763 system call has been finished --- successfully or not --- and should behave
33764 as if the break message arrived right after the system call.
33766 @value{GDBN} must behave reliably. If the system call has not been called
33767 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
33768 @code{errno} in the packet. If the system call on the host has been finished
33769 before the user requests a break, the full action must be finished by
33770 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
33771 The @code{F} packet may only be sent when either nothing has happened
33772 or the full action has been completed.
33775 @subsection Console I/O
33776 @cindex console i/o as part of file-i/o
33778 By default and if not explicitly closed by the target system, the file
33779 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
33780 on the @value{GDBN} console is handled as any other file output operation
33781 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
33782 by @value{GDBN} so that after the target read request from file descriptor
33783 0 all following typing is buffered until either one of the following
33788 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
33790 system call is treated as finished.
33793 The user presses @key{RET}. This is treated as end of input with a trailing
33797 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
33798 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
33802 If the user has typed more characters than fit in the buffer given to
33803 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
33804 either another @code{read(0, @dots{})} is requested by the target, or debugging
33805 is stopped at the user's request.
33808 @node List of Supported Calls
33809 @subsection List of Supported Calls
33810 @cindex list of supported file-i/o calls
33827 @unnumberedsubsubsec open
33828 @cindex open, file-i/o system call
33833 int open(const char *pathname, int flags);
33834 int open(const char *pathname, int flags, mode_t mode);
33838 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
33841 @var{flags} is the bitwise @code{OR} of the following values:
33845 If the file does not exist it will be created. The host
33846 rules apply as far as file ownership and time stamps
33850 When used with @code{O_CREAT}, if the file already exists it is
33851 an error and open() fails.
33854 If the file already exists and the open mode allows
33855 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
33856 truncated to zero length.
33859 The file is opened in append mode.
33862 The file is opened for reading only.
33865 The file is opened for writing only.
33868 The file is opened for reading and writing.
33872 Other bits are silently ignored.
33876 @var{mode} is the bitwise @code{OR} of the following values:
33880 User has read permission.
33883 User has write permission.
33886 Group has read permission.
33889 Group has write permission.
33892 Others have read permission.
33895 Others have write permission.
33899 Other bits are silently ignored.
33902 @item Return value:
33903 @code{open} returns the new file descriptor or -1 if an error
33910 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
33913 @var{pathname} refers to a directory.
33916 The requested access is not allowed.
33919 @var{pathname} was too long.
33922 A directory component in @var{pathname} does not exist.
33925 @var{pathname} refers to a device, pipe, named pipe or socket.
33928 @var{pathname} refers to a file on a read-only filesystem and
33929 write access was requested.
33932 @var{pathname} is an invalid pointer value.
33935 No space on device to create the file.
33938 The process already has the maximum number of files open.
33941 The limit on the total number of files open on the system
33945 The call was interrupted by the user.
33951 @unnumberedsubsubsec close
33952 @cindex close, file-i/o system call
33961 @samp{Fclose,@var{fd}}
33963 @item Return value:
33964 @code{close} returns zero on success, or -1 if an error occurred.
33970 @var{fd} isn't a valid open file descriptor.
33973 The call was interrupted by the user.
33979 @unnumberedsubsubsec read
33980 @cindex read, file-i/o system call
33985 int read(int fd, void *buf, unsigned int count);
33989 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
33991 @item Return value:
33992 On success, the number of bytes read is returned.
33993 Zero indicates end of file. If count is zero, read
33994 returns zero as well. On error, -1 is returned.
34000 @var{fd} is not a valid file descriptor or is not open for
34004 @var{bufptr} is an invalid pointer value.
34007 The call was interrupted by the user.
34013 @unnumberedsubsubsec write
34014 @cindex write, file-i/o system call
34019 int write(int fd, const void *buf, unsigned int count);
34023 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
34025 @item Return value:
34026 On success, the number of bytes written are returned.
34027 Zero indicates nothing was written. On error, -1
34034 @var{fd} is not a valid file descriptor or is not open for
34038 @var{bufptr} is an invalid pointer value.
34041 An attempt was made to write a file that exceeds the
34042 host-specific maximum file size allowed.
34045 No space on device to write the data.
34048 The call was interrupted by the user.
34054 @unnumberedsubsubsec lseek
34055 @cindex lseek, file-i/o system call
34060 long lseek (int fd, long offset, int flag);
34064 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
34066 @var{flag} is one of:
34070 The offset is set to @var{offset} bytes.
34073 The offset is set to its current location plus @var{offset}
34077 The offset is set to the size of the file plus @var{offset}
34081 @item Return value:
34082 On success, the resulting unsigned offset in bytes from
34083 the beginning of the file is returned. Otherwise, a
34084 value of -1 is returned.
34090 @var{fd} is not a valid open file descriptor.
34093 @var{fd} is associated with the @value{GDBN} console.
34096 @var{flag} is not a proper value.
34099 The call was interrupted by the user.
34105 @unnumberedsubsubsec rename
34106 @cindex rename, file-i/o system call
34111 int rename(const char *oldpath, const char *newpath);
34115 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
34117 @item Return value:
34118 On success, zero is returned. On error, -1 is returned.
34124 @var{newpath} is an existing directory, but @var{oldpath} is not a
34128 @var{newpath} is a non-empty directory.
34131 @var{oldpath} or @var{newpath} is a directory that is in use by some
34135 An attempt was made to make a directory a subdirectory
34139 A component used as a directory in @var{oldpath} or new
34140 path is not a directory. Or @var{oldpath} is a directory
34141 and @var{newpath} exists but is not a directory.
34144 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
34147 No access to the file or the path of the file.
34151 @var{oldpath} or @var{newpath} was too long.
34154 A directory component in @var{oldpath} or @var{newpath} does not exist.
34157 The file is on a read-only filesystem.
34160 The device containing the file has no room for the new
34164 The call was interrupted by the user.
34170 @unnumberedsubsubsec unlink
34171 @cindex unlink, file-i/o system call
34176 int unlink(const char *pathname);
34180 @samp{Funlink,@var{pathnameptr}/@var{len}}
34182 @item Return value:
34183 On success, zero is returned. On error, -1 is returned.
34189 No access to the file or the path of the file.
34192 The system does not allow unlinking of directories.
34195 The file @var{pathname} cannot be unlinked because it's
34196 being used by another process.
34199 @var{pathnameptr} is an invalid pointer value.
34202 @var{pathname} was too long.
34205 A directory component in @var{pathname} does not exist.
34208 A component of the path is not a directory.
34211 The file is on a read-only filesystem.
34214 The call was interrupted by the user.
34220 @unnumberedsubsubsec stat/fstat
34221 @cindex fstat, file-i/o system call
34222 @cindex stat, file-i/o system call
34227 int stat(const char *pathname, struct stat *buf);
34228 int fstat(int fd, struct stat *buf);
34232 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
34233 @samp{Ffstat,@var{fd},@var{bufptr}}
34235 @item Return value:
34236 On success, zero is returned. On error, -1 is returned.
34242 @var{fd} is not a valid open file.
34245 A directory component in @var{pathname} does not exist or the
34246 path is an empty string.
34249 A component of the path is not a directory.
34252 @var{pathnameptr} is an invalid pointer value.
34255 No access to the file or the path of the file.
34258 @var{pathname} was too long.
34261 The call was interrupted by the user.
34267 @unnumberedsubsubsec gettimeofday
34268 @cindex gettimeofday, file-i/o system call
34273 int gettimeofday(struct timeval *tv, void *tz);
34277 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
34279 @item Return value:
34280 On success, 0 is returned, -1 otherwise.
34286 @var{tz} is a non-NULL pointer.
34289 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
34295 @unnumberedsubsubsec isatty
34296 @cindex isatty, file-i/o system call
34301 int isatty(int fd);
34305 @samp{Fisatty,@var{fd}}
34307 @item Return value:
34308 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
34314 The call was interrupted by the user.
34319 Note that the @code{isatty} call is treated as a special case: it returns
34320 1 to the target if the file descriptor is attached
34321 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
34322 would require implementing @code{ioctl} and would be more complex than
34327 @unnumberedsubsubsec system
34328 @cindex system, file-i/o system call
34333 int system(const char *command);
34337 @samp{Fsystem,@var{commandptr}/@var{len}}
34339 @item Return value:
34340 If @var{len} is zero, the return value indicates whether a shell is
34341 available. A zero return value indicates a shell is not available.
34342 For non-zero @var{len}, the value returned is -1 on error and the
34343 return status of the command otherwise. Only the exit status of the
34344 command is returned, which is extracted from the host's @code{system}
34345 return value by calling @code{WEXITSTATUS(retval)}. In case
34346 @file{/bin/sh} could not be executed, 127 is returned.
34352 The call was interrupted by the user.
34357 @value{GDBN} takes over the full task of calling the necessary host calls
34358 to perform the @code{system} call. The return value of @code{system} on
34359 the host is simplified before it's returned
34360 to the target. Any termination signal information from the child process
34361 is discarded, and the return value consists
34362 entirely of the exit status of the called command.
34364 Due to security concerns, the @code{system} call is by default refused
34365 by @value{GDBN}. The user has to allow this call explicitly with the
34366 @code{set remote system-call-allowed 1} command.
34369 @item set remote system-call-allowed
34370 @kindex set remote system-call-allowed
34371 Control whether to allow the @code{system} calls in the File I/O
34372 protocol for the remote target. The default is zero (disabled).
34374 @item show remote system-call-allowed
34375 @kindex show remote system-call-allowed
34376 Show whether the @code{system} calls are allowed in the File I/O
34380 @node Protocol-specific Representation of Datatypes
34381 @subsection Protocol-specific Representation of Datatypes
34382 @cindex protocol-specific representation of datatypes, in file-i/o protocol
34385 * Integral Datatypes::
34387 * Memory Transfer::
34392 @node Integral Datatypes
34393 @unnumberedsubsubsec Integral Datatypes
34394 @cindex integral datatypes, in file-i/o protocol
34396 The integral datatypes used in the system calls are @code{int},
34397 @code{unsigned int}, @code{long}, @code{unsigned long},
34398 @code{mode_t}, and @code{time_t}.
34400 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
34401 implemented as 32 bit values in this protocol.
34403 @code{long} and @code{unsigned long} are implemented as 64 bit types.
34405 @xref{Limits}, for corresponding MIN and MAX values (similar to those
34406 in @file{limits.h}) to allow range checking on host and target.
34408 @code{time_t} datatypes are defined as seconds since the Epoch.
34410 All integral datatypes transferred as part of a memory read or write of a
34411 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
34414 @node Pointer Values
34415 @unnumberedsubsubsec Pointer Values
34416 @cindex pointer values, in file-i/o protocol
34418 Pointers to target data are transmitted as they are. An exception
34419 is made for pointers to buffers for which the length isn't
34420 transmitted as part of the function call, namely strings. Strings
34421 are transmitted as a pointer/length pair, both as hex values, e.g.@:
34428 which is a pointer to data of length 18 bytes at position 0x1aaf.
34429 The length is defined as the full string length in bytes, including
34430 the trailing null byte. For example, the string @code{"hello world"}
34431 at address 0x123456 is transmitted as
34437 @node Memory Transfer
34438 @unnumberedsubsubsec Memory Transfer
34439 @cindex memory transfer, in file-i/o protocol
34441 Structured data which is transferred using a memory read or write (for
34442 example, a @code{struct stat}) is expected to be in a protocol-specific format
34443 with all scalar multibyte datatypes being big endian. Translation to
34444 this representation needs to be done both by the target before the @code{F}
34445 packet is sent, and by @value{GDBN} before
34446 it transfers memory to the target. Transferred pointers to structured
34447 data should point to the already-coerced data at any time.
34451 @unnumberedsubsubsec struct stat
34452 @cindex struct stat, in file-i/o protocol
34454 The buffer of type @code{struct stat} used by the target and @value{GDBN}
34455 is defined as follows:
34459 unsigned int st_dev; /* device */
34460 unsigned int st_ino; /* inode */
34461 mode_t st_mode; /* protection */
34462 unsigned int st_nlink; /* number of hard links */
34463 unsigned int st_uid; /* user ID of owner */
34464 unsigned int st_gid; /* group ID of owner */
34465 unsigned int st_rdev; /* device type (if inode device) */
34466 unsigned long st_size; /* total size, in bytes */
34467 unsigned long st_blksize; /* blocksize for filesystem I/O */
34468 unsigned long st_blocks; /* number of blocks allocated */
34469 time_t st_atime; /* time of last access */
34470 time_t st_mtime; /* time of last modification */
34471 time_t st_ctime; /* time of last change */
34475 The integral datatypes conform to the definitions given in the
34476 appropriate section (see @ref{Integral Datatypes}, for details) so this
34477 structure is of size 64 bytes.
34479 The values of several fields have a restricted meaning and/or
34485 A value of 0 represents a file, 1 the console.
34488 No valid meaning for the target. Transmitted unchanged.
34491 Valid mode bits are described in @ref{Constants}. Any other
34492 bits have currently no meaning for the target.
34497 No valid meaning for the target. Transmitted unchanged.
34502 These values have a host and file system dependent
34503 accuracy. Especially on Windows hosts, the file system may not
34504 support exact timing values.
34507 The target gets a @code{struct stat} of the above representation and is
34508 responsible for coercing it to the target representation before
34511 Note that due to size differences between the host, target, and protocol
34512 representations of @code{struct stat} members, these members could eventually
34513 get truncated on the target.
34515 @node struct timeval
34516 @unnumberedsubsubsec struct timeval
34517 @cindex struct timeval, in file-i/o protocol
34519 The buffer of type @code{struct timeval} used by the File-I/O protocol
34520 is defined as follows:
34524 time_t tv_sec; /* second */
34525 long tv_usec; /* microsecond */
34529 The integral datatypes conform to the definitions given in the
34530 appropriate section (see @ref{Integral Datatypes}, for details) so this
34531 structure is of size 8 bytes.
34534 @subsection Constants
34535 @cindex constants, in file-i/o protocol
34537 The following values are used for the constants inside of the
34538 protocol. @value{GDBN} and target are responsible for translating these
34539 values before and after the call as needed.
34550 @unnumberedsubsubsec Open Flags
34551 @cindex open flags, in file-i/o protocol
34553 All values are given in hexadecimal representation.
34565 @node mode_t Values
34566 @unnumberedsubsubsec mode_t Values
34567 @cindex mode_t values, in file-i/o protocol
34569 All values are given in octal representation.
34586 @unnumberedsubsubsec Errno Values
34587 @cindex errno values, in file-i/o protocol
34589 All values are given in decimal representation.
34614 @code{EUNKNOWN} is used as a fallback error value if a host system returns
34615 any error value not in the list of supported error numbers.
34618 @unnumberedsubsubsec Lseek Flags
34619 @cindex lseek flags, in file-i/o protocol
34628 @unnumberedsubsubsec Limits
34629 @cindex limits, in file-i/o protocol
34631 All values are given in decimal representation.
34634 INT_MIN -2147483648
34636 UINT_MAX 4294967295
34637 LONG_MIN -9223372036854775808
34638 LONG_MAX 9223372036854775807
34639 ULONG_MAX 18446744073709551615
34642 @node File-I/O Examples
34643 @subsection File-I/O Examples
34644 @cindex file-i/o examples
34646 Example sequence of a write call, file descriptor 3, buffer is at target
34647 address 0x1234, 6 bytes should be written:
34650 <- @code{Fwrite,3,1234,6}
34651 @emph{request memory read from target}
34654 @emph{return "6 bytes written"}
34658 Example sequence of a read call, file descriptor 3, buffer is at target
34659 address 0x1234, 6 bytes should be read:
34662 <- @code{Fread,3,1234,6}
34663 @emph{request memory write to target}
34664 -> @code{X1234,6:XXXXXX}
34665 @emph{return "6 bytes read"}
34669 Example sequence of a read call, call fails on the host due to invalid
34670 file descriptor (@code{EBADF}):
34673 <- @code{Fread,3,1234,6}
34677 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
34681 <- @code{Fread,3,1234,6}
34686 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
34690 <- @code{Fread,3,1234,6}
34691 -> @code{X1234,6:XXXXXX}
34695 @node Library List Format
34696 @section Library List Format
34697 @cindex library list format, remote protocol
34699 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
34700 same process as your application to manage libraries. In this case,
34701 @value{GDBN} can use the loader's symbol table and normal memory
34702 operations to maintain a list of shared libraries. On other
34703 platforms, the operating system manages loaded libraries.
34704 @value{GDBN} can not retrieve the list of currently loaded libraries
34705 through memory operations, so it uses the @samp{qXfer:libraries:read}
34706 packet (@pxref{qXfer library list read}) instead. The remote stub
34707 queries the target's operating system and reports which libraries
34710 The @samp{qXfer:libraries:read} packet returns an XML document which
34711 lists loaded libraries and their offsets. Each library has an
34712 associated name and one or more segment or section base addresses,
34713 which report where the library was loaded in memory.
34715 For the common case of libraries that are fully linked binaries, the
34716 library should have a list of segments. If the target supports
34717 dynamic linking of a relocatable object file, its library XML element
34718 should instead include a list of allocated sections. The segment or
34719 section bases are start addresses, not relocation offsets; they do not
34720 depend on the library's link-time base addresses.
34722 @value{GDBN} must be linked with the Expat library to support XML
34723 library lists. @xref{Expat}.
34725 A simple memory map, with one loaded library relocated by a single
34726 offset, looks like this:
34730 <library name="/lib/libc.so.6">
34731 <segment address="0x10000000"/>
34736 Another simple memory map, with one loaded library with three
34737 allocated sections (.text, .data, .bss), looks like this:
34741 <library name="sharedlib.o">
34742 <section address="0x10000000"/>
34743 <section address="0x20000000"/>
34744 <section address="0x30000000"/>
34749 The format of a library list is described by this DTD:
34752 <!-- library-list: Root element with versioning -->
34753 <!ELEMENT library-list (library)*>
34754 <!ATTLIST library-list version CDATA #FIXED "1.0">
34755 <!ELEMENT library (segment*, section*)>
34756 <!ATTLIST library name CDATA #REQUIRED>
34757 <!ELEMENT segment EMPTY>
34758 <!ATTLIST segment address CDATA #REQUIRED>
34759 <!ELEMENT section EMPTY>
34760 <!ATTLIST section address CDATA #REQUIRED>
34763 In addition, segments and section descriptors cannot be mixed within a
34764 single library element, and you must supply at least one segment or
34765 section for each library.
34767 @node Memory Map Format
34768 @section Memory Map Format
34769 @cindex memory map format
34771 To be able to write into flash memory, @value{GDBN} needs to obtain a
34772 memory map from the target. This section describes the format of the
34775 The memory map is obtained using the @samp{qXfer:memory-map:read}
34776 (@pxref{qXfer memory map read}) packet and is an XML document that
34777 lists memory regions.
34779 @value{GDBN} must be linked with the Expat library to support XML
34780 memory maps. @xref{Expat}.
34782 The top-level structure of the document is shown below:
34785 <?xml version="1.0"?>
34786 <!DOCTYPE memory-map
34787 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
34788 "http://sourceware.org/gdb/gdb-memory-map.dtd">
34794 Each region can be either:
34799 A region of RAM starting at @var{addr} and extending for @var{length}
34803 <memory type="ram" start="@var{addr}" length="@var{length}"/>
34808 A region of read-only memory:
34811 <memory type="rom" start="@var{addr}" length="@var{length}"/>
34816 A region of flash memory, with erasure blocks @var{blocksize}
34820 <memory type="flash" start="@var{addr}" length="@var{length}">
34821 <property name="blocksize">@var{blocksize}</property>
34827 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
34828 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
34829 packets to write to addresses in such ranges.
34831 The formal DTD for memory map format is given below:
34834 <!-- ................................................... -->
34835 <!-- Memory Map XML DTD ................................ -->
34836 <!-- File: memory-map.dtd .............................. -->
34837 <!-- .................................... .............. -->
34838 <!-- memory-map.dtd -->
34839 <!-- memory-map: Root element with versioning -->
34840 <!ELEMENT memory-map (memory | property)>
34841 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
34842 <!ELEMENT memory (property)>
34843 <!-- memory: Specifies a memory region,
34844 and its type, or device. -->
34845 <!ATTLIST memory type CDATA #REQUIRED
34846 start CDATA #REQUIRED
34847 length CDATA #REQUIRED
34848 device CDATA #IMPLIED>
34849 <!-- property: Generic attribute tag -->
34850 <!ELEMENT property (#PCDATA | property)*>
34851 <!ATTLIST property name CDATA #REQUIRED>
34854 @node Thread List Format
34855 @section Thread List Format
34856 @cindex thread list format
34858 To efficiently update the list of threads and their attributes,
34859 @value{GDBN} issues the @samp{qXfer:threads:read} packet
34860 (@pxref{qXfer threads read}) and obtains the XML document with
34861 the following structure:
34864 <?xml version="1.0"?>
34866 <thread id="id" core="0">
34867 ... description ...
34872 Each @samp{thread} element must have the @samp{id} attribute that
34873 identifies the thread (@pxref{thread-id syntax}). The
34874 @samp{core} attribute, if present, specifies which processor core
34875 the thread was last executing on. The content of the of @samp{thread}
34876 element is interpreted as human-readable auxilliary information.
34878 @include agentexpr.texi
34880 @node Trace File Format
34881 @appendix Trace File Format
34882 @cindex trace file format
34884 The trace file comes in three parts: a header, a textual description
34885 section, and a trace frame section with binary data.
34887 The header has the form @code{\x7fTRACE0\n}. The first byte is
34888 @code{0x7f} so as to indicate that the file contains binary data,
34889 while the @code{0} is a version number that may have different values
34892 The description section consists of multiple lines of @sc{ascii} text
34893 separated by newline characters (@code{0xa}). The lines may include a
34894 variety of optional descriptive or context-setting information, such
34895 as tracepoint definitions or register set size. @value{GDBN} will
34896 ignore any line that it does not recognize. An empty line marks the end
34899 @c FIXME add some specific types of data
34901 The trace frame section consists of a number of consecutive frames.
34902 Each frame begins with a two-byte tracepoint number, followed by a
34903 four-byte size giving the amount of data in the frame. The data in
34904 the frame consists of a number of blocks, each introduced by a
34905 character indicating its type (at least register, memory, and trace
34906 state variable). The data in this section is raw binary, not a
34907 hexadecimal or other encoding; its endianness matches the target's
34910 @c FIXME bi-arch may require endianness/arch info in description section
34913 @item R @var{bytes}
34914 Register block. The number and ordering of bytes matches that of a
34915 @code{g} packet in the remote protocol. Note that these are the
34916 actual bytes, in target order and @value{GDBN} register order, not a
34917 hexadecimal encoding.
34919 @item M @var{address} @var{length} @var{bytes}...
34920 Memory block. This is a contiguous block of memory, at the 8-byte
34921 address @var{address}, with a 2-byte length @var{length}, followed by
34922 @var{length} bytes.
34924 @item V @var{number} @var{value}
34925 Trace state variable block. This records the 8-byte signed value
34926 @var{value} of trace state variable numbered @var{number}.
34930 Future enhancements of the trace file format may include additional types
34933 @node Target Descriptions
34934 @appendix Target Descriptions
34935 @cindex target descriptions
34937 @strong{Warning:} target descriptions are still under active development,
34938 and the contents and format may change between @value{GDBN} releases.
34939 The format is expected to stabilize in the future.
34941 One of the challenges of using @value{GDBN} to debug embedded systems
34942 is that there are so many minor variants of each processor
34943 architecture in use. It is common practice for vendors to start with
34944 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
34945 and then make changes to adapt it to a particular market niche. Some
34946 architectures have hundreds of variants, available from dozens of
34947 vendors. This leads to a number of problems:
34951 With so many different customized processors, it is difficult for
34952 the @value{GDBN} maintainers to keep up with the changes.
34954 Since individual variants may have short lifetimes or limited
34955 audiences, it may not be worthwhile to carry information about every
34956 variant in the @value{GDBN} source tree.
34958 When @value{GDBN} does support the architecture of the embedded system
34959 at hand, the task of finding the correct architecture name to give the
34960 @command{set architecture} command can be error-prone.
34963 To address these problems, the @value{GDBN} remote protocol allows a
34964 target system to not only identify itself to @value{GDBN}, but to
34965 actually describe its own features. This lets @value{GDBN} support
34966 processor variants it has never seen before --- to the extent that the
34967 descriptions are accurate, and that @value{GDBN} understands them.
34969 @value{GDBN} must be linked with the Expat library to support XML
34970 target descriptions. @xref{Expat}.
34973 * Retrieving Descriptions:: How descriptions are fetched from a target.
34974 * Target Description Format:: The contents of a target description.
34975 * Predefined Target Types:: Standard types available for target
34977 * Standard Target Features:: Features @value{GDBN} knows about.
34980 @node Retrieving Descriptions
34981 @section Retrieving Descriptions
34983 Target descriptions can be read from the target automatically, or
34984 specified by the user manually. The default behavior is to read the
34985 description from the target. @value{GDBN} retrieves it via the remote
34986 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
34987 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
34988 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
34989 XML document, of the form described in @ref{Target Description
34992 Alternatively, you can specify a file to read for the target description.
34993 If a file is set, the target will not be queried. The commands to
34994 specify a file are:
34997 @cindex set tdesc filename
34998 @item set tdesc filename @var{path}
34999 Read the target description from @var{path}.
35001 @cindex unset tdesc filename
35002 @item unset tdesc filename
35003 Do not read the XML target description from a file. @value{GDBN}
35004 will use the description supplied by the current target.
35006 @cindex show tdesc filename
35007 @item show tdesc filename
35008 Show the filename to read for a target description, if any.
35012 @node Target Description Format
35013 @section Target Description Format
35014 @cindex target descriptions, XML format
35016 A target description annex is an @uref{http://www.w3.org/XML/, XML}
35017 document which complies with the Document Type Definition provided in
35018 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
35019 means you can use generally available tools like @command{xmllint} to
35020 check that your feature descriptions are well-formed and valid.
35021 However, to help people unfamiliar with XML write descriptions for
35022 their targets, we also describe the grammar here.
35024 Target descriptions can identify the architecture of the remote target
35025 and (for some architectures) provide information about custom register
35026 sets. They can also identify the OS ABI of the remote target.
35027 @value{GDBN} can use this information to autoconfigure for your
35028 target, or to warn you if you connect to an unsupported target.
35030 Here is a simple target description:
35033 <target version="1.0">
35034 <architecture>i386:x86-64</architecture>
35039 This minimal description only says that the target uses
35040 the x86-64 architecture.
35042 A target description has the following overall form, with [ ] marking
35043 optional elements and @dots{} marking repeatable elements. The elements
35044 are explained further below.
35047 <?xml version="1.0"?>
35048 <!DOCTYPE target SYSTEM "gdb-target.dtd">
35049 <target version="1.0">
35050 @r{[}@var{architecture}@r{]}
35051 @r{[}@var{osabi}@r{]}
35052 @r{[}@var{compatible}@r{]}
35053 @r{[}@var{feature}@dots{}@r{]}
35058 The description is generally insensitive to whitespace and line
35059 breaks, under the usual common-sense rules. The XML version
35060 declaration and document type declaration can generally be omitted
35061 (@value{GDBN} does not require them), but specifying them may be
35062 useful for XML validation tools. The @samp{version} attribute for
35063 @samp{<target>} may also be omitted, but we recommend
35064 including it; if future versions of @value{GDBN} use an incompatible
35065 revision of @file{gdb-target.dtd}, they will detect and report
35066 the version mismatch.
35068 @subsection Inclusion
35069 @cindex target descriptions, inclusion
35072 @cindex <xi:include>
35075 It can sometimes be valuable to split a target description up into
35076 several different annexes, either for organizational purposes, or to
35077 share files between different possible target descriptions. You can
35078 divide a description into multiple files by replacing any element of
35079 the target description with an inclusion directive of the form:
35082 <xi:include href="@var{document}"/>
35086 When @value{GDBN} encounters an element of this form, it will retrieve
35087 the named XML @var{document}, and replace the inclusion directive with
35088 the contents of that document. If the current description was read
35089 using @samp{qXfer}, then so will be the included document;
35090 @var{document} will be interpreted as the name of an annex. If the
35091 current description was read from a file, @value{GDBN} will look for
35092 @var{document} as a file in the same directory where it found the
35093 original description.
35095 @subsection Architecture
35096 @cindex <architecture>
35098 An @samp{<architecture>} element has this form:
35101 <architecture>@var{arch}</architecture>
35104 @var{arch} is one of the architectures from the set accepted by
35105 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35108 @cindex @code{<osabi>}
35110 This optional field was introduced in @value{GDBN} version 7.0.
35111 Previous versions of @value{GDBN} ignore it.
35113 An @samp{<osabi>} element has this form:
35116 <osabi>@var{abi-name}</osabi>
35119 @var{abi-name} is an OS ABI name from the same selection accepted by
35120 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
35122 @subsection Compatible Architecture
35123 @cindex @code{<compatible>}
35125 This optional field was introduced in @value{GDBN} version 7.0.
35126 Previous versions of @value{GDBN} ignore it.
35128 A @samp{<compatible>} element has this form:
35131 <compatible>@var{arch}</compatible>
35134 @var{arch} is one of the architectures from the set accepted by
35135 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35137 A @samp{<compatible>} element is used to specify that the target
35138 is able to run binaries in some other than the main target architecture
35139 given by the @samp{<architecture>} element. For example, on the
35140 Cell Broadband Engine, the main architecture is @code{powerpc:common}
35141 or @code{powerpc:common64}, but the system is able to run binaries
35142 in the @code{spu} architecture as well. The way to describe this
35143 capability with @samp{<compatible>} is as follows:
35146 <architecture>powerpc:common</architecture>
35147 <compatible>spu</compatible>
35150 @subsection Features
35153 Each @samp{<feature>} describes some logical portion of the target
35154 system. Features are currently used to describe available CPU
35155 registers and the types of their contents. A @samp{<feature>} element
35159 <feature name="@var{name}">
35160 @r{[}@var{type}@dots{}@r{]}
35166 Each feature's name should be unique within the description. The name
35167 of a feature does not matter unless @value{GDBN} has some special
35168 knowledge of the contents of that feature; if it does, the feature
35169 should have its standard name. @xref{Standard Target Features}.
35173 Any register's value is a collection of bits which @value{GDBN} must
35174 interpret. The default interpretation is a two's complement integer,
35175 but other types can be requested by name in the register description.
35176 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
35177 Target Types}), and the description can define additional composite types.
35179 Each type element must have an @samp{id} attribute, which gives
35180 a unique (within the containing @samp{<feature>}) name to the type.
35181 Types must be defined before they are used.
35184 Some targets offer vector registers, which can be treated as arrays
35185 of scalar elements. These types are written as @samp{<vector>} elements,
35186 specifying the array element type, @var{type}, and the number of elements,
35190 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
35194 If a register's value is usefully viewed in multiple ways, define it
35195 with a union type containing the useful representations. The
35196 @samp{<union>} element contains one or more @samp{<field>} elements,
35197 each of which has a @var{name} and a @var{type}:
35200 <union id="@var{id}">
35201 <field name="@var{name}" type="@var{type}"/>
35207 If a register's value is composed from several separate values, define
35208 it with a structure type. There are two forms of the @samp{<struct>}
35209 element; a @samp{<struct>} element must either contain only bitfields
35210 or contain no bitfields. If the structure contains only bitfields,
35211 its total size in bytes must be specified, each bitfield must have an
35212 explicit start and end, and bitfields are automatically assigned an
35213 integer type. The field's @var{start} should be less than or
35214 equal to its @var{end}, and zero represents the least significant bit.
35217 <struct id="@var{id}" size="@var{size}">
35218 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
35223 If the structure contains no bitfields, then each field has an
35224 explicit type, and no implicit padding is added.
35227 <struct id="@var{id}">
35228 <field name="@var{name}" type="@var{type}"/>
35234 If a register's value is a series of single-bit flags, define it with
35235 a flags type. The @samp{<flags>} element has an explicit @var{size}
35236 and contains one or more @samp{<field>} elements. Each field has a
35237 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
35241 <flags id="@var{id}" size="@var{size}">
35242 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
35247 @subsection Registers
35250 Each register is represented as an element with this form:
35253 <reg name="@var{name}"
35254 bitsize="@var{size}"
35255 @r{[}regnum="@var{num}"@r{]}
35256 @r{[}save-restore="@var{save-restore}"@r{]}
35257 @r{[}type="@var{type}"@r{]}
35258 @r{[}group="@var{group}"@r{]}/>
35262 The components are as follows:
35267 The register's name; it must be unique within the target description.
35270 The register's size, in bits.
35273 The register's number. If omitted, a register's number is one greater
35274 than that of the previous register (either in the current feature or in
35275 a preceeding feature); the first register in the target description
35276 defaults to zero. This register number is used to read or write
35277 the register; e.g.@: it is used in the remote @code{p} and @code{P}
35278 packets, and registers appear in the @code{g} and @code{G} packets
35279 in order of increasing register number.
35282 Whether the register should be preserved across inferior function
35283 calls; this must be either @code{yes} or @code{no}. The default is
35284 @code{yes}, which is appropriate for most registers except for
35285 some system control registers; this is not related to the target's
35289 The type of the register. @var{type} may be a predefined type, a type
35290 defined in the current feature, or one of the special types @code{int}
35291 and @code{float}. @code{int} is an integer type of the correct size
35292 for @var{bitsize}, and @code{float} is a floating point type (in the
35293 architecture's normal floating point format) of the correct size for
35294 @var{bitsize}. The default is @code{int}.
35297 The register group to which this register belongs. @var{group} must
35298 be either @code{general}, @code{float}, or @code{vector}. If no
35299 @var{group} is specified, @value{GDBN} will not display the register
35300 in @code{info registers}.
35304 @node Predefined Target Types
35305 @section Predefined Target Types
35306 @cindex target descriptions, predefined types
35308 Type definitions in the self-description can build up composite types
35309 from basic building blocks, but can not define fundamental types. Instead,
35310 standard identifiers are provided by @value{GDBN} for the fundamental
35311 types. The currently supported types are:
35320 Signed integer types holding the specified number of bits.
35327 Unsigned integer types holding the specified number of bits.
35331 Pointers to unspecified code and data. The program counter and
35332 any dedicated return address register may be marked as code
35333 pointers; printing a code pointer converts it into a symbolic
35334 address. The stack pointer and any dedicated address registers
35335 may be marked as data pointers.
35338 Single precision IEEE floating point.
35341 Double precision IEEE floating point.
35344 The 12-byte extended precision format used by ARM FPA registers.
35347 The 10-byte extended precision format used by x87 registers.
35350 32bit @sc{eflags} register used by x86.
35353 32bit @sc{mxcsr} register used by x86.
35357 @node Standard Target Features
35358 @section Standard Target Features
35359 @cindex target descriptions, standard features
35361 A target description must contain either no registers or all the
35362 target's registers. If the description contains no registers, then
35363 @value{GDBN} will assume a default register layout, selected based on
35364 the architecture. If the description contains any registers, the
35365 default layout will not be used; the standard registers must be
35366 described in the target description, in such a way that @value{GDBN}
35367 can recognize them.
35369 This is accomplished by giving specific names to feature elements
35370 which contain standard registers. @value{GDBN} will look for features
35371 with those names and verify that they contain the expected registers;
35372 if any known feature is missing required registers, or if any required
35373 feature is missing, @value{GDBN} will reject the target
35374 description. You can add additional registers to any of the
35375 standard features --- @value{GDBN} will display them just as if
35376 they were added to an unrecognized feature.
35378 This section lists the known features and their expected contents.
35379 Sample XML documents for these features are included in the
35380 @value{GDBN} source tree, in the directory @file{gdb/features}.
35382 Names recognized by @value{GDBN} should include the name of the
35383 company or organization which selected the name, and the overall
35384 architecture to which the feature applies; so e.g.@: the feature
35385 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
35387 The names of registers are not case sensitive for the purpose
35388 of recognizing standard features, but @value{GDBN} will only display
35389 registers using the capitalization used in the description.
35396 * PowerPC Features::
35401 @subsection ARM Features
35402 @cindex target descriptions, ARM features
35404 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
35405 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
35406 @samp{lr}, @samp{pc}, and @samp{cpsr}.
35408 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
35409 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
35411 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
35412 it should contain at least registers @samp{wR0} through @samp{wR15} and
35413 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
35414 @samp{wCSSF}, and @samp{wCASF} registers are optional.
35416 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
35417 should contain at least registers @samp{d0} through @samp{d15}. If
35418 they are present, @samp{d16} through @samp{d31} should also be included.
35419 @value{GDBN} will synthesize the single-precision registers from
35420 halves of the double-precision registers.
35422 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
35423 need to contain registers; it instructs @value{GDBN} to display the
35424 VFP double-precision registers as vectors and to synthesize the
35425 quad-precision registers from pairs of double-precision registers.
35426 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
35427 be present and include 32 double-precision registers.
35429 @node i386 Features
35430 @subsection i386 Features
35431 @cindex target descriptions, i386 features
35433 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
35434 targets. It should describe the following registers:
35438 @samp{eax} through @samp{edi} plus @samp{eip} for i386
35440 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
35442 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
35443 @samp{fs}, @samp{gs}
35445 @samp{st0} through @samp{st7}
35447 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
35448 @samp{foseg}, @samp{fooff} and @samp{fop}
35451 The register sets may be different, depending on the target.
35453 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
35454 describe registers:
35458 @samp{xmm0} through @samp{xmm7} for i386
35460 @samp{xmm0} through @samp{xmm15} for amd64
35465 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
35466 @samp{org.gnu.gdb.i386.sse} feature. It should
35467 describe the upper 128 bits of @sc{ymm} registers:
35471 @samp{ymm0h} through @samp{ymm7h} for i386
35473 @samp{ymm0h} through @samp{ymm15h} for amd64
35477 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
35478 describe a single register, @samp{orig_eax}.
35480 @node MIPS Features
35481 @subsection MIPS Features
35482 @cindex target descriptions, MIPS features
35484 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
35485 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
35486 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
35489 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
35490 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
35491 registers. They may be 32-bit or 64-bit depending on the target.
35493 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
35494 it may be optional in a future version of @value{GDBN}. It should
35495 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
35496 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
35498 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
35499 contain a single register, @samp{restart}, which is used by the
35500 Linux kernel to control restartable syscalls.
35502 @node M68K Features
35503 @subsection M68K Features
35504 @cindex target descriptions, M68K features
35507 @item @samp{org.gnu.gdb.m68k.core}
35508 @itemx @samp{org.gnu.gdb.coldfire.core}
35509 @itemx @samp{org.gnu.gdb.fido.core}
35510 One of those features must be always present.
35511 The feature that is present determines which flavor of m68k is
35512 used. The feature that is present should contain registers
35513 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
35514 @samp{sp}, @samp{ps} and @samp{pc}.
35516 @item @samp{org.gnu.gdb.coldfire.fp}
35517 This feature is optional. If present, it should contain registers
35518 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
35522 @node PowerPC Features
35523 @subsection PowerPC Features
35524 @cindex target descriptions, PowerPC features
35526 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
35527 targets. It should contain registers @samp{r0} through @samp{r31},
35528 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
35529 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
35531 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
35532 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
35534 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
35535 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
35538 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
35539 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
35540 will combine these registers with the floating point registers
35541 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
35542 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
35543 through @samp{vs63}, the set of vector registers for POWER7.
35545 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
35546 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
35547 @samp{spefscr}. SPE targets should provide 32-bit registers in
35548 @samp{org.gnu.gdb.power.core} and provide the upper halves in
35549 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
35550 these to present registers @samp{ev0} through @samp{ev31} to the
35553 @node Operating System Information
35554 @appendix Operating System Information
35555 @cindex operating system information
35561 Users of @value{GDBN} often wish to obtain information about the state of
35562 the operating system running on the target---for example the list of
35563 processes, or the list of open files. This section describes the
35564 mechanism that makes it possible. This mechanism is similar to the
35565 target features mechanism (@pxref{Target Descriptions}), but focuses
35566 on a different aspect of target.
35568 Operating system information is retrived from the target via the
35569 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
35570 read}). The object name in the request should be @samp{osdata}, and
35571 the @var{annex} identifies the data to be fetched.
35574 @appendixsection Process list
35575 @cindex operating system information, process list
35577 When requesting the process list, the @var{annex} field in the
35578 @samp{qXfer} request should be @samp{processes}. The returned data is
35579 an XML document. The formal syntax of this document is defined in
35580 @file{gdb/features/osdata.dtd}.
35582 An example document is:
35585 <?xml version="1.0"?>
35586 <!DOCTYPE target SYSTEM "osdata.dtd">
35587 <osdata type="processes">
35589 <column name="pid">1</column>
35590 <column name="user">root</column>
35591 <column name="command">/sbin/init</column>
35592 <column name="cores">1,2,3</column>
35597 Each item should include a column whose name is @samp{pid}. The value
35598 of that column should identify the process on the target. The
35599 @samp{user} and @samp{command} columns are optional, and will be
35600 displayed by @value{GDBN}. The @samp{cores} column, if present,
35601 should contain a comma-separated list of cores that this process
35602 is running on. Target may provide additional columns,
35603 which @value{GDBN} currently ignores.
35607 @node GNU Free Documentation License
35608 @appendix GNU Free Documentation License
35617 % I think something like @colophon should be in texinfo. In the
35619 \long\def\colophon{\hbox to0pt{}\vfill
35620 \centerline{The body of this manual is set in}
35621 \centerline{\fontname\tenrm,}
35622 \centerline{with headings in {\bf\fontname\tenbf}}
35623 \centerline{and examples in {\tt\fontname\tentt}.}
35624 \centerline{{\it\fontname\tenit\/},}
35625 \centerline{{\bf\fontname\tenbf}, and}
35626 \centerline{{\sl\fontname\tensl\/}}
35627 \centerline{are used for emphasis.}\vfill}
35629 % Blame: doc@cygnus.com, 1991.