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 1.1 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++}.
218 Support for Modula-2 is partial. For information on Modula-2, see
219 @ref{Modula-2,,Modula-2}.
222 Debugging Pascal programs which use sets, subranges, file variables, or
223 nested functions does not currently work. @value{GDBN} does not support
224 entering expressions, printing values, or similar features using Pascal
228 @value{GDBN} can be used to debug programs written in Fortran, although
229 it may be necessary to refer to some variables with a trailing
232 @value{GDBN} can be used to debug programs written in Objective-C,
233 using either the Apple/NeXT or the GNU Objective-C runtime.
236 * Free Software:: Freely redistributable software
237 * Contributors:: Contributors to GDB
241 @unnumberedsec Free Software
243 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
244 General Public License
245 (GPL). The GPL gives you the freedom to copy or adapt a licensed
246 program---but every person getting a copy also gets with it the
247 freedom to modify that copy (which means that they must get access to
248 the source code), and the freedom to distribute further copies.
249 Typical software companies use copyrights to limit your freedoms; the
250 Free Software Foundation uses the GPL to preserve these freedoms.
252 Fundamentally, the General Public License is a license which says that
253 you have these freedoms and that you cannot take these freedoms away
256 @unnumberedsec Free Software Needs Free Documentation
258 The biggest deficiency in the free software community today is not in
259 the software---it is the lack of good free documentation that we can
260 include with the free software. Many of our most important
261 programs do not come with free reference manuals and free introductory
262 texts. Documentation is an essential part of any software package;
263 when an important free software package does not come with a free
264 manual and a free tutorial, that is a major gap. We have many such
267 Consider Perl, for instance. The tutorial manuals that people
268 normally use are non-free. How did this come about? Because the
269 authors of those manuals published them with restrictive terms---no
270 copying, no modification, source files not available---which exclude
271 them from the free software world.
273 That wasn't the first time this sort of thing happened, and it was far
274 from the last. Many times we have heard a GNU user eagerly describe a
275 manual that he is writing, his intended contribution to the community,
276 only to learn that he had ruined everything by signing a publication
277 contract to make it non-free.
279 Free documentation, like free software, is a matter of freedom, not
280 price. The problem with the non-free manual is not that publishers
281 charge a price for printed copies---that in itself is fine. (The Free
282 Software Foundation sells printed copies of manuals, too.) The
283 problem is the restrictions on the use of the manual. Free manuals
284 are available in source code form, and give you permission to copy and
285 modify. Non-free manuals do not allow this.
287 The criteria of freedom for a free manual are roughly the same as for
288 free software. Redistribution (including the normal kinds of
289 commercial redistribution) must be permitted, so that the manual can
290 accompany every copy of the program, both on-line and on paper.
292 Permission for modification of the technical content is crucial too.
293 When people modify the software, adding or changing features, if they
294 are conscientious they will change the manual too---so they can
295 provide accurate and clear documentation for the modified program. A
296 manual that leaves you no choice but to write a new manual to document
297 a changed version of the program is not really available to our
300 Some kinds of limits on the way modification is handled are
301 acceptable. For example, requirements to preserve the original
302 author's copyright notice, the distribution terms, or the list of
303 authors, are ok. It is also no problem to require modified versions
304 to include notice that they were modified. Even entire sections that
305 may not be deleted or changed are acceptable, as long as they deal
306 with nontechnical topics (like this one). These kinds of restrictions
307 are acceptable because they don't obstruct the community's normal use
310 However, it must be possible to modify all the @emph{technical}
311 content of the manual, and then distribute the result in all the usual
312 media, through all the usual channels. Otherwise, the restrictions
313 obstruct the use of the manual, it is not free, and we need another
314 manual to replace it.
316 Please spread the word about this issue. Our community continues to
317 lose manuals to proprietary publishing. If we spread the word that
318 free software needs free reference manuals and free tutorials, perhaps
319 the next person who wants to contribute by writing documentation will
320 realize, before it is too late, that only free manuals contribute to
321 the free software community.
323 If you are writing documentation, please insist on publishing it under
324 the GNU Free Documentation License or another free documentation
325 license. Remember that this decision requires your approval---you
326 don't have to let the publisher decide. Some commercial publishers
327 will use a free license if you insist, but they will not propose the
328 option; it is up to you to raise the issue and say firmly that this is
329 what you want. If the publisher you are dealing with refuses, please
330 try other publishers. If you're not sure whether a proposed license
331 is free, write to @email{licensing@@gnu.org}.
333 You can encourage commercial publishers to sell more free, copylefted
334 manuals and tutorials by buying them, and particularly by buying
335 copies from the publishers that paid for their writing or for major
336 improvements. Meanwhile, try to avoid buying non-free documentation
337 at all. Check the distribution terms of a manual before you buy it,
338 and insist that whoever seeks your business must respect your freedom.
339 Check the history of the book, and try to reward the publishers that
340 have paid or pay the authors to work on it.
342 The Free Software Foundation maintains a list of free documentation
343 published by other publishers, at
344 @url{http://www.fsf.org/doc/other-free-books.html}.
347 @unnumberedsec Contributors to @value{GDBN}
349 Richard Stallman was the original author of @value{GDBN}, and of many
350 other @sc{gnu} programs. Many others have contributed to its
351 development. This section attempts to credit major contributors. One
352 of the virtues of free software is that everyone is free to contribute
353 to it; with regret, we cannot actually acknowledge everyone here. The
354 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
355 blow-by-blow account.
357 Changes much prior to version 2.0 are lost in the mists of time.
360 @emph{Plea:} Additions to this section are particularly welcome. If you
361 or your friends (or enemies, to be evenhanded) have been unfairly
362 omitted from this list, we would like to add your names!
365 So that they may not regard their many labors as thankless, we
366 particularly thank those who shepherded @value{GDBN} through major
368 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
369 Jim Blandy (release 4.18);
370 Jason Molenda (release 4.17);
371 Stan Shebs (release 4.14);
372 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
373 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
374 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
375 Jim Kingdon (releases 3.5, 3.4, and 3.3);
376 and Randy Smith (releases 3.2, 3.1, and 3.0).
378 Richard Stallman, assisted at various times by Peter TerMaat, Chris
379 Hanson, and Richard Mlynarik, handled releases through 2.8.
381 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
382 in @value{GDBN}, with significant additional contributions from Per
383 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
384 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
385 much general update work leading to release 3.0).
387 @value{GDBN} uses the BFD subroutine library to examine multiple
388 object-file formats; BFD was a joint project of David V.
389 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
391 David Johnson wrote the original COFF support; Pace Willison did
392 the original support for encapsulated COFF.
394 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
396 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
397 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
399 Jean-Daniel Fekete contributed Sun 386i support.
400 Chris Hanson improved the HP9000 support.
401 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
402 David Johnson contributed Encore Umax support.
403 Jyrki Kuoppala contributed Altos 3068 support.
404 Jeff Law contributed HP PA and SOM support.
405 Keith Packard contributed NS32K support.
406 Doug Rabson contributed Acorn Risc Machine support.
407 Bob Rusk contributed Harris Nighthawk CX-UX support.
408 Chris Smith contributed Convex support (and Fortran debugging).
409 Jonathan Stone contributed Pyramid support.
410 Michael Tiemann contributed SPARC support.
411 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
412 Pace Willison contributed Intel 386 support.
413 Jay Vosburgh contributed Symmetry support.
414 Marko Mlinar contributed OpenRISC 1000 support.
416 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
418 Rich Schaefer and Peter Schauer helped with support of SunOS shared
421 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
422 about several machine instruction sets.
424 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
425 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
426 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
427 and RDI targets, respectively.
429 Brian Fox is the author of the readline libraries providing
430 command-line editing and command history.
432 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
433 Modula-2 support, and contributed the Languages chapter of this manual.
435 Fred Fish wrote most of the support for Unix System Vr4.
436 He also enhanced the command-completion support to cover C@t{++} overloaded
439 Hitachi America (now Renesas America), Ltd. sponsored the support for
440 H8/300, H8/500, and Super-H processors.
442 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
444 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
447 Toshiba sponsored the support for the TX39 Mips processor.
449 Matsushita sponsored the support for the MN10200 and MN10300 processors.
451 Fujitsu sponsored the support for SPARClite and FR30 processors.
453 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
456 Michael Snyder added support for tracepoints.
458 Stu Grossman wrote gdbserver.
460 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
461 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
463 The following people at the Hewlett-Packard Company contributed
464 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
465 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
466 compiler, and the Text User Interface (nee Terminal User Interface):
467 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
468 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
469 provided HP-specific information in this manual.
471 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
472 Robert Hoehne made significant contributions to the DJGPP port.
474 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
475 development since 1991. Cygnus engineers who have worked on @value{GDBN}
476 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
477 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
478 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
479 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
480 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
481 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
482 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
483 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
484 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
485 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
486 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
487 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
488 Zuhn have made contributions both large and small.
490 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
491 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
493 Jim Blandy added support for preprocessor macros, while working for Red
496 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
497 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
498 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
499 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
500 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
501 with the migration of old architectures to this new framework.
503 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
504 unwinder framework, this consisting of a fresh new design featuring
505 frame IDs, independent frame sniffers, and the sentinel frame. Mark
506 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
507 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
508 trad unwinders. The architecture-specific changes, each involving a
509 complete rewrite of the architecture's frame code, were carried out by
510 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
511 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
512 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
513 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
516 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
517 Tensilica, Inc.@: contributed support for Xtensa processors. Others
518 who have worked on the Xtensa port of @value{GDBN} in the past include
519 Steve Tjiang, John Newlin, and Scott Foehner.
521 Michael Eager and staff of Xilinx, Inc., contributed support for the
522 Xilinx MicroBlaze architecture.
525 @chapter A Sample @value{GDBN} Session
527 You can use this manual at your leisure to read all about @value{GDBN}.
528 However, a handful of commands are enough to get started using the
529 debugger. This chapter illustrates those commands.
532 In this sample session, we emphasize user input like this: @b{input},
533 to make it easier to pick out from the surrounding output.
536 @c FIXME: this example may not be appropriate for some configs, where
537 @c FIXME...primary interest is in remote use.
539 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
540 processor) exhibits the following bug: sometimes, when we change its
541 quote strings from the default, the commands used to capture one macro
542 definition within another stop working. In the following short @code{m4}
543 session, we define a macro @code{foo} which expands to @code{0000}; we
544 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
545 same thing. However, when we change the open quote string to
546 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
547 procedure fails to define a new synonym @code{baz}:
556 @b{define(bar,defn(`foo'))}
560 @b{changequote(<QUOTE>,<UNQUOTE>)}
562 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
565 m4: End of input: 0: fatal error: EOF in string
569 Let us use @value{GDBN} to try to see what is going on.
572 $ @b{@value{GDBP} m4}
573 @c FIXME: this falsifies the exact text played out, to permit smallbook
574 @c FIXME... format to come out better.
575 @value{GDBN} is free software and you are welcome to distribute copies
576 of it under certain conditions; type "show copying" to see
578 There is absolutely no warranty for @value{GDBN}; type "show warranty"
581 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
586 @value{GDBN} reads only enough symbol data to know where to find the
587 rest when needed; as a result, the first prompt comes up very quickly.
588 We now tell @value{GDBN} to use a narrower display width than usual, so
589 that examples fit in this manual.
592 (@value{GDBP}) @b{set width 70}
596 We need to see how the @code{m4} built-in @code{changequote} works.
597 Having looked at the source, we know the relevant subroutine is
598 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
599 @code{break} command.
602 (@value{GDBP}) @b{break m4_changequote}
603 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
607 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
608 control; as long as control does not reach the @code{m4_changequote}
609 subroutine, the program runs as usual:
612 (@value{GDBP}) @b{run}
613 Starting program: /work/Editorial/gdb/gnu/m4/m4
621 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
622 suspends execution of @code{m4}, displaying information about the
623 context where it stops.
626 @b{changequote(<QUOTE>,<UNQUOTE>)}
628 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
630 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
634 Now we use the command @code{n} (@code{next}) to advance execution to
635 the next line of the current function.
639 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
644 @code{set_quotes} looks like a promising subroutine. We can go into it
645 by using the command @code{s} (@code{step}) instead of @code{next}.
646 @code{step} goes to the next line to be executed in @emph{any}
647 subroutine, so it steps into @code{set_quotes}.
651 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
653 530 if (lquote != def_lquote)
657 The display that shows the subroutine where @code{m4} is now
658 suspended (and its arguments) is called a stack frame display. It
659 shows a summary of the stack. We can use the @code{backtrace}
660 command (which can also be spelled @code{bt}), to see where we are
661 in the stack as a whole: the @code{backtrace} command displays a
662 stack frame for each active subroutine.
665 (@value{GDBP}) @b{bt}
666 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
668 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
670 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
671 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
673 #4 0x79dc in expand_input () at macro.c:40
674 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
678 We step through a few more lines to see what happens. The first two
679 times, we can use @samp{s}; the next two times we use @code{n} to avoid
680 falling into the @code{xstrdup} subroutine.
684 0x3b5c 532 if (rquote != def_rquote)
686 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
687 def_lquote : xstrdup(lq);
689 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
692 538 len_lquote = strlen(rquote);
696 The last line displayed looks a little odd; we can examine the variables
697 @code{lquote} and @code{rquote} to see if they are in fact the new left
698 and right quotes we specified. We use the command @code{p}
699 (@code{print}) to see their values.
702 (@value{GDBP}) @b{p lquote}
703 $1 = 0x35d40 "<QUOTE>"
704 (@value{GDBP}) @b{p rquote}
705 $2 = 0x35d50 "<UNQUOTE>"
709 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
710 To look at some context, we can display ten lines of source
711 surrounding the current line with the @code{l} (@code{list}) command.
717 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
719 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
722 538 len_lquote = strlen(rquote);
723 539 len_rquote = strlen(lquote);
730 Let us step past the two lines that set @code{len_lquote} and
731 @code{len_rquote}, and then examine the values of those variables.
735 539 len_rquote = strlen(lquote);
738 (@value{GDBP}) @b{p len_lquote}
740 (@value{GDBP}) @b{p len_rquote}
745 That certainly looks wrong, assuming @code{len_lquote} and
746 @code{len_rquote} are meant to be the lengths of @code{lquote} and
747 @code{rquote} respectively. We can set them to better values using
748 the @code{p} command, since it can print the value of
749 any expression---and that expression can include subroutine calls and
753 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
755 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
760 Is that enough to fix the problem of using the new quotes with the
761 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
762 executing with the @code{c} (@code{continue}) command, and then try the
763 example that caused trouble initially:
769 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
776 Success! The new quotes now work just as well as the default ones. The
777 problem seems to have been just the two typos defining the wrong
778 lengths. We allow @code{m4} exit by giving it an EOF as input:
782 Program exited normally.
786 The message @samp{Program exited normally.} is from @value{GDBN}; it
787 indicates @code{m4} has finished executing. We can end our @value{GDBN}
788 session with the @value{GDBN} @code{quit} command.
791 (@value{GDBP}) @b{quit}
795 @chapter Getting In and Out of @value{GDBN}
797 This chapter discusses how to start @value{GDBN}, and how to get out of it.
801 type @samp{@value{GDBP}} to start @value{GDBN}.
803 type @kbd{quit} or @kbd{Ctrl-d} to exit.
807 * Invoking GDB:: How to start @value{GDBN}
808 * Quitting GDB:: How to quit @value{GDBN}
809 * Shell Commands:: How to use shell commands inside @value{GDBN}
810 * Logging Output:: How to log @value{GDBN}'s output to a file
814 @section Invoking @value{GDBN}
816 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
817 @value{GDBN} reads commands from the terminal until you tell it to exit.
819 You can also run @code{@value{GDBP}} with a variety of arguments and options,
820 to specify more of your debugging environment at the outset.
822 The command-line options described here are designed
823 to cover a variety of situations; in some environments, some of these
824 options may effectively be unavailable.
826 The most usual way to start @value{GDBN} is with one argument,
827 specifying an executable program:
830 @value{GDBP} @var{program}
834 You can also start with both an executable program and a core file
838 @value{GDBP} @var{program} @var{core}
841 You can, instead, specify a process ID as a second argument, if you want
842 to debug a running process:
845 @value{GDBP} @var{program} 1234
849 would attach @value{GDBN} to process @code{1234} (unless you also have a file
850 named @file{1234}; @value{GDBN} does check for a core file first).
852 Taking advantage of the second command-line argument requires a fairly
853 complete operating system; when you use @value{GDBN} as a remote
854 debugger attached to a bare board, there may not be any notion of
855 ``process'', and there is often no way to get a core dump. @value{GDBN}
856 will warn you if it is unable to attach or to read core dumps.
858 You can optionally have @code{@value{GDBP}} pass any arguments after the
859 executable file to the inferior using @code{--args}. This option stops
862 @value{GDBP} --args gcc -O2 -c foo.c
864 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
865 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
867 You can run @code{@value{GDBP}} without printing the front material, which describes
868 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
875 You can further control how @value{GDBN} starts up by using command-line
876 options. @value{GDBN} itself can remind you of the options available.
886 to display all available options and briefly describe their use
887 (@samp{@value{GDBP} -h} is a shorter equivalent).
889 All options and command line arguments you give are processed
890 in sequential order. The order makes a difference when the
891 @samp{-x} option is used.
895 * File Options:: Choosing files
896 * Mode Options:: Choosing modes
897 * Startup:: What @value{GDBN} does during startup
901 @subsection Choosing Files
903 When @value{GDBN} starts, it reads any arguments other than options as
904 specifying an executable file and core file (or process ID). This is
905 the same as if the arguments were specified by the @samp{-se} and
906 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
907 first argument that does not have an associated option flag as
908 equivalent to the @samp{-se} option followed by that argument; and the
909 second argument that does not have an associated option flag, if any, as
910 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
911 If the second argument begins with a decimal digit, @value{GDBN} will
912 first attempt to attach to it as a process, and if that fails, attempt
913 to open it as a corefile. If you have a corefile whose name begins with
914 a digit, you can prevent @value{GDBN} from treating it as a pid by
915 prefixing it with @file{./}, e.g.@: @file{./12345}.
917 If @value{GDBN} has not been configured to included core file support,
918 such as for most embedded targets, then it will complain about a second
919 argument and ignore it.
921 Many options have both long and short forms; both are shown in the
922 following list. @value{GDBN} also recognizes the long forms if you truncate
923 them, so long as enough of the option is present to be unambiguous.
924 (If you prefer, you can flag option arguments with @samp{--} rather
925 than @samp{-}, though we illustrate the more usual convention.)
927 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
928 @c way, both those who look for -foo and --foo in the index, will find
932 @item -symbols @var{file}
934 @cindex @code{--symbols}
936 Read symbol table from file @var{file}.
938 @item -exec @var{file}
940 @cindex @code{--exec}
942 Use file @var{file} as the executable file to execute when appropriate,
943 and for examining pure data in conjunction with a core dump.
947 Read symbol table from file @var{file} and use it as the executable
950 @item -core @var{file}
952 @cindex @code{--core}
954 Use file @var{file} as a core dump to examine.
956 @item -pid @var{number}
957 @itemx -p @var{number}
960 Connect to process ID @var{number}, as with the @code{attach} command.
962 @item -command @var{file}
964 @cindex @code{--command}
966 Execute commands from file @var{file}. The contents of this file is
967 evaluated exactly as the @code{source} command would.
968 @xref{Command Files,, Command files}.
970 @item -eval-command @var{command}
971 @itemx -ex @var{command}
972 @cindex @code{--eval-command}
974 Execute a single @value{GDBN} command.
976 This option may be used multiple times to call multiple commands. It may
977 also be interleaved with @samp{-command} as required.
980 @value{GDBP} -ex 'target sim' -ex 'load' \
981 -x setbreakpoints -ex 'run' a.out
984 @item -directory @var{directory}
985 @itemx -d @var{directory}
986 @cindex @code{--directory}
988 Add @var{directory} to the path to search for source and script files.
992 @cindex @code{--readnow}
994 Read each symbol file's entire symbol table immediately, rather than
995 the default, which is to read it incrementally as it is needed.
996 This makes startup slower, but makes future operations faster.
1001 @subsection Choosing Modes
1003 You can run @value{GDBN} in various alternative modes---for example, in
1004 batch mode or quiet mode.
1011 Do not execute commands found in any initialization files. Normally,
1012 @value{GDBN} executes the commands in these files after all the command
1013 options and arguments have been processed. @xref{Command Files,,Command
1019 @cindex @code{--quiet}
1020 @cindex @code{--silent}
1022 ``Quiet''. Do not print the introductory and copyright messages. These
1023 messages are also suppressed in batch mode.
1026 @cindex @code{--batch}
1027 Run in batch mode. Exit with status @code{0} after processing all the
1028 command files specified with @samp{-x} (and all commands from
1029 initialization files, if not inhibited with @samp{-n}). Exit with
1030 nonzero status if an error occurs in executing the @value{GDBN} commands
1031 in the command files. Batch mode also disables pagination;
1032 @pxref{Screen Size} and acts as if @kbd{set confirm off} were in
1033 effect (@pxref{Messages/Warnings}).
1035 Batch mode may be useful for running @value{GDBN} as a filter, for
1036 example to download and run a program on another computer; in order to
1037 make this more useful, the message
1040 Program exited normally.
1044 (which is ordinarily issued whenever a program running under
1045 @value{GDBN} control terminates) is not issued when running in batch
1049 @cindex @code{--batch-silent}
1050 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1051 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1052 unaffected). This is much quieter than @samp{-silent} and would be useless
1053 for an interactive session.
1055 This is particularly useful when using targets that give @samp{Loading section}
1056 messages, for example.
1058 Note that targets that give their output via @value{GDBN}, as opposed to
1059 writing directly to @code{stdout}, will also be made silent.
1061 @item -return-child-result
1062 @cindex @code{--return-child-result}
1063 The return code from @value{GDBN} will be the return code from the child
1064 process (the process being debugged), with the following exceptions:
1068 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1069 internal error. In this case the exit code is the same as it would have been
1070 without @samp{-return-child-result}.
1072 The user quits with an explicit value. E.g., @samp{quit 1}.
1074 The child process never runs, or is not allowed to terminate, in which case
1075 the exit code will be -1.
1078 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1079 when @value{GDBN} is being used as a remote program loader or simulator
1084 @cindex @code{--nowindows}
1086 ``No windows''. If @value{GDBN} comes with a graphical user interface
1087 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1088 interface. If no GUI is available, this option has no effect.
1092 @cindex @code{--windows}
1094 If @value{GDBN} includes a GUI, then this option requires it to be
1097 @item -cd @var{directory}
1099 Run @value{GDBN} using @var{directory} as its working directory,
1100 instead of the current directory.
1104 @cindex @code{--fullname}
1106 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1107 subprocess. It tells @value{GDBN} to output the full file name and line
1108 number in a standard, recognizable fashion each time a stack frame is
1109 displayed (which includes each time your program stops). This
1110 recognizable format looks like two @samp{\032} characters, followed by
1111 the file name, line number and character position separated by colons,
1112 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1113 @samp{\032} characters as a signal to display the source code for the
1117 @cindex @code{--epoch}
1118 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1119 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1120 routines so as to allow Epoch to display values of expressions in a
1123 @item -annotate @var{level}
1124 @cindex @code{--annotate}
1125 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1126 effect is identical to using @samp{set annotate @var{level}}
1127 (@pxref{Annotations}). The annotation @var{level} controls how much
1128 information @value{GDBN} prints together with its prompt, values of
1129 expressions, source lines, and other types of output. Level 0 is the
1130 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1131 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1132 that control @value{GDBN}, and level 2 has been deprecated.
1134 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1138 @cindex @code{--args}
1139 Change interpretation of command line so that arguments following the
1140 executable file are passed as command line arguments to the inferior.
1141 This option stops option processing.
1143 @item -baud @var{bps}
1145 @cindex @code{--baud}
1147 Set the line speed (baud rate or bits per second) of any serial
1148 interface used by @value{GDBN} for remote debugging.
1150 @item -l @var{timeout}
1152 Set the timeout (in seconds) of any communication used by @value{GDBN}
1153 for remote debugging.
1155 @item -tty @var{device}
1156 @itemx -t @var{device}
1157 @cindex @code{--tty}
1159 Run using @var{device} for your program's standard input and output.
1160 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1162 @c resolve the situation of these eventually
1164 @cindex @code{--tui}
1165 Activate the @dfn{Text User Interface} when starting. The Text User
1166 Interface manages several text windows on the terminal, showing
1167 source, assembly, registers and @value{GDBN} command outputs
1168 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1169 Text User Interface can be enabled by invoking the program
1170 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1171 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1174 @c @cindex @code{--xdb}
1175 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1176 @c For information, see the file @file{xdb_trans.html}, which is usually
1177 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1180 @item -interpreter @var{interp}
1181 @cindex @code{--interpreter}
1182 Use the interpreter @var{interp} for interface with the controlling
1183 program or device. This option is meant to be set by programs which
1184 communicate with @value{GDBN} using it as a back end.
1185 @xref{Interpreters, , Command Interpreters}.
1187 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1188 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1189 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1190 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1191 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1192 @sc{gdb/mi} interfaces are no longer supported.
1195 @cindex @code{--write}
1196 Open the executable and core files for both reading and writing. This
1197 is equivalent to the @samp{set write on} command inside @value{GDBN}
1201 @cindex @code{--statistics}
1202 This option causes @value{GDBN} to print statistics about time and
1203 memory usage after it completes each command and returns to the prompt.
1206 @cindex @code{--version}
1207 This option causes @value{GDBN} to print its version number and
1208 no-warranty blurb, and exit.
1213 @subsection What @value{GDBN} Does During Startup
1214 @cindex @value{GDBN} startup
1216 Here's the description of what @value{GDBN} does during session startup:
1220 Sets up the command interpreter as specified by the command line
1221 (@pxref{Mode Options, interpreter}).
1225 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1226 used when building @value{GDBN}; @pxref{System-wide configuration,
1227 ,System-wide configuration and settings}) and executes all the commands in
1231 Reads the init file (if any) in your home directory@footnote{On
1232 DOS/Windows systems, the home directory is the one pointed to by the
1233 @code{HOME} environment variable.} and executes all the commands in
1237 Processes command line options and operands.
1240 Reads and executes the commands from init file (if any) in the current
1241 working directory. This is only done if the current directory is
1242 different from your home directory. Thus, you can have more than one
1243 init file, one generic in your home directory, and another, specific
1244 to the program you are debugging, in the directory where you invoke
1248 Reads command files specified by the @samp{-x} option. @xref{Command
1249 Files}, for more details about @value{GDBN} command files.
1252 Reads the command history recorded in the @dfn{history file}.
1253 @xref{Command History}, for more details about the command history and the
1254 files where @value{GDBN} records it.
1257 Init files use the same syntax as @dfn{command files} (@pxref{Command
1258 Files}) and are processed by @value{GDBN} in the same way. The init
1259 file in your home directory can set options (such as @samp{set
1260 complaints}) that affect subsequent processing of command line options
1261 and operands. Init files are not executed if you use the @samp{-nx}
1262 option (@pxref{Mode Options, ,Choosing Modes}).
1264 To display the list of init files loaded by gdb at startup, you
1265 can use @kbd{gdb --help}.
1267 @cindex init file name
1268 @cindex @file{.gdbinit}
1269 @cindex @file{gdb.ini}
1270 The @value{GDBN} init files are normally called @file{.gdbinit}.
1271 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1272 the limitations of file names imposed by DOS filesystems. The Windows
1273 ports of @value{GDBN} use the standard name, but if they find a
1274 @file{gdb.ini} file, they warn you about that and suggest to rename
1275 the file to the standard name.
1279 @section Quitting @value{GDBN}
1280 @cindex exiting @value{GDBN}
1281 @cindex leaving @value{GDBN}
1284 @kindex quit @r{[}@var{expression}@r{]}
1285 @kindex q @r{(@code{quit})}
1286 @item quit @r{[}@var{expression}@r{]}
1288 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1289 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1290 do not supply @var{expression}, @value{GDBN} will terminate normally;
1291 otherwise it will terminate using the result of @var{expression} as the
1296 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1297 terminates the action of any @value{GDBN} command that is in progress and
1298 returns to @value{GDBN} command level. It is safe to type the interrupt
1299 character at any time because @value{GDBN} does not allow it to take effect
1300 until a time when it is safe.
1302 If you have been using @value{GDBN} to control an attached process or
1303 device, you can release it with the @code{detach} command
1304 (@pxref{Attach, ,Debugging an Already-running Process}).
1306 @node Shell Commands
1307 @section Shell Commands
1309 If you need to execute occasional shell commands during your
1310 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1311 just use the @code{shell} command.
1315 @cindex shell escape
1316 @item shell @var{command string}
1317 Invoke a standard shell to execute @var{command string}.
1318 If it exists, the environment variable @code{SHELL} determines which
1319 shell to run. Otherwise @value{GDBN} uses the default shell
1320 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1323 The utility @code{make} is often needed in development environments.
1324 You do not have to use the @code{shell} command for this purpose in
1329 @cindex calling make
1330 @item make @var{make-args}
1331 Execute the @code{make} program with the specified
1332 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1335 @node Logging Output
1336 @section Logging Output
1337 @cindex logging @value{GDBN} output
1338 @cindex save @value{GDBN} output to a file
1340 You may want to save the output of @value{GDBN} commands to a file.
1341 There are several commands to control @value{GDBN}'s logging.
1345 @item set logging on
1347 @item set logging off
1349 @cindex logging file name
1350 @item set logging file @var{file}
1351 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1352 @item set logging overwrite [on|off]
1353 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1354 you want @code{set logging on} to overwrite the logfile instead.
1355 @item set logging redirect [on|off]
1356 By default, @value{GDBN} output will go to both the terminal and the logfile.
1357 Set @code{redirect} if you want output to go only to the log file.
1358 @kindex show logging
1360 Show the current values of the logging settings.
1364 @chapter @value{GDBN} Commands
1366 You can abbreviate a @value{GDBN} command to the first few letters of the command
1367 name, if that abbreviation is unambiguous; and you can repeat certain
1368 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1369 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1370 show you the alternatives available, if there is more than one possibility).
1373 * Command Syntax:: How to give commands to @value{GDBN}
1374 * Completion:: Command completion
1375 * Help:: How to ask @value{GDBN} for help
1378 @node Command Syntax
1379 @section Command Syntax
1381 A @value{GDBN} command is a single line of input. There is no limit on
1382 how long it can be. It starts with a command name, which is followed by
1383 arguments whose meaning depends on the command name. For example, the
1384 command @code{step} accepts an argument which is the number of times to
1385 step, as in @samp{step 5}. You can also use the @code{step} command
1386 with no arguments. Some commands do not allow any arguments.
1388 @cindex abbreviation
1389 @value{GDBN} command names may always be truncated if that abbreviation is
1390 unambiguous. Other possible command abbreviations are listed in the
1391 documentation for individual commands. In some cases, even ambiguous
1392 abbreviations are allowed; for example, @code{s} is specially defined as
1393 equivalent to @code{step} even though there are other commands whose
1394 names start with @code{s}. You can test abbreviations by using them as
1395 arguments to the @code{help} command.
1397 @cindex repeating commands
1398 @kindex RET @r{(repeat last command)}
1399 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1400 repeat the previous command. Certain commands (for example, @code{run})
1401 will not repeat this way; these are commands whose unintentional
1402 repetition might cause trouble and which you are unlikely to want to
1403 repeat. User-defined commands can disable this feature; see
1404 @ref{Define, dont-repeat}.
1406 The @code{list} and @code{x} commands, when you repeat them with
1407 @key{RET}, construct new arguments rather than repeating
1408 exactly as typed. This permits easy scanning of source or memory.
1410 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1411 output, in a way similar to the common utility @code{more}
1412 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1413 @key{RET} too many in this situation, @value{GDBN} disables command
1414 repetition after any command that generates this sort of display.
1416 @kindex # @r{(a comment)}
1418 Any text from a @kbd{#} to the end of the line is a comment; it does
1419 nothing. This is useful mainly in command files (@pxref{Command
1420 Files,,Command Files}).
1422 @cindex repeating command sequences
1423 @kindex Ctrl-o @r{(operate-and-get-next)}
1424 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1425 commands. This command accepts the current line, like @key{RET}, and
1426 then fetches the next line relative to the current line from the history
1430 @section Command Completion
1433 @cindex word completion
1434 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1435 only one possibility; it can also show you what the valid possibilities
1436 are for the next word in a command, at any time. This works for @value{GDBN}
1437 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1439 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1440 of a word. If there is only one possibility, @value{GDBN} fills in the
1441 word, and waits for you to finish the command (or press @key{RET} to
1442 enter it). For example, if you type
1444 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1445 @c complete accuracy in these examples; space introduced for clarity.
1446 @c If texinfo enhancements make it unnecessary, it would be nice to
1447 @c replace " @key" by "@key" in the following...
1449 (@value{GDBP}) info bre @key{TAB}
1453 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1454 the only @code{info} subcommand beginning with @samp{bre}:
1457 (@value{GDBP}) info breakpoints
1461 You can either press @key{RET} at this point, to run the @code{info
1462 breakpoints} command, or backspace and enter something else, if
1463 @samp{breakpoints} does not look like the command you expected. (If you
1464 were sure you wanted @code{info breakpoints} in the first place, you
1465 might as well just type @key{RET} immediately after @samp{info bre},
1466 to exploit command abbreviations rather than command completion).
1468 If there is more than one possibility for the next word when you press
1469 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1470 characters and try again, or just press @key{TAB} a second time;
1471 @value{GDBN} displays all the possible completions for that word. For
1472 example, you might want to set a breakpoint on a subroutine whose name
1473 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1474 just sounds the bell. Typing @key{TAB} again displays all the
1475 function names in your program that begin with those characters, for
1479 (@value{GDBP}) b make_ @key{TAB}
1480 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1481 make_a_section_from_file make_environ
1482 make_abs_section make_function_type
1483 make_blockvector make_pointer_type
1484 make_cleanup make_reference_type
1485 make_command make_symbol_completion_list
1486 (@value{GDBP}) b make_
1490 After displaying the available possibilities, @value{GDBN} copies your
1491 partial input (@samp{b make_} in the example) so you can finish the
1494 If you just want to see the list of alternatives in the first place, you
1495 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1496 means @kbd{@key{META} ?}. You can type this either by holding down a
1497 key designated as the @key{META} shift on your keyboard (if there is
1498 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1500 @cindex quotes in commands
1501 @cindex completion of quoted strings
1502 Sometimes the string you need, while logically a ``word'', may contain
1503 parentheses or other characters that @value{GDBN} normally excludes from
1504 its notion of a word. To permit word completion to work in this
1505 situation, you may enclose words in @code{'} (single quote marks) in
1506 @value{GDBN} commands.
1508 The most likely situation where you might need this is in typing the
1509 name of a C@t{++} function. This is because C@t{++} allows function
1510 overloading (multiple definitions of the same function, distinguished
1511 by argument type). For example, when you want to set a breakpoint you
1512 may need to distinguish whether you mean the version of @code{name}
1513 that takes an @code{int} parameter, @code{name(int)}, or the version
1514 that takes a @code{float} parameter, @code{name(float)}. To use the
1515 word-completion facilities in this situation, type a single quote
1516 @code{'} at the beginning of the function name. This alerts
1517 @value{GDBN} that it may need to consider more information than usual
1518 when you press @key{TAB} or @kbd{M-?} to request word completion:
1521 (@value{GDBP}) b 'bubble( @kbd{M-?}
1522 bubble(double,double) bubble(int,int)
1523 (@value{GDBP}) b 'bubble(
1526 In some cases, @value{GDBN} can tell that completing a name requires using
1527 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1528 completing as much as it can) if you do not type the quote in the first
1532 (@value{GDBP}) b bub @key{TAB}
1533 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1534 (@value{GDBP}) b 'bubble(
1538 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1539 you have not yet started typing the argument list when you ask for
1540 completion on an overloaded symbol.
1542 For more information about overloaded functions, see @ref{C Plus Plus
1543 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1544 overload-resolution off} to disable overload resolution;
1545 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1547 @cindex completion of structure field names
1548 @cindex structure field name completion
1549 @cindex completion of union field names
1550 @cindex union field name completion
1551 When completing in an expression which looks up a field in a
1552 structure, @value{GDBN} also tries@footnote{The completer can be
1553 confused by certain kinds of invalid expressions. Also, it only
1554 examines the static type of the expression, not the dynamic type.} to
1555 limit completions to the field names available in the type of the
1559 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1560 magic to_delete to_fputs to_put to_rewind
1561 to_data to_flush to_isatty to_read to_write
1565 This is because the @code{gdb_stdout} is a variable of the type
1566 @code{struct ui_file} that is defined in @value{GDBN} sources as
1573 ui_file_flush_ftype *to_flush;
1574 ui_file_write_ftype *to_write;
1575 ui_file_fputs_ftype *to_fputs;
1576 ui_file_read_ftype *to_read;
1577 ui_file_delete_ftype *to_delete;
1578 ui_file_isatty_ftype *to_isatty;
1579 ui_file_rewind_ftype *to_rewind;
1580 ui_file_put_ftype *to_put;
1587 @section Getting Help
1588 @cindex online documentation
1591 You can always ask @value{GDBN} itself for information on its commands,
1592 using the command @code{help}.
1595 @kindex h @r{(@code{help})}
1598 You can use @code{help} (abbreviated @code{h}) with no arguments to
1599 display a short list of named classes of commands:
1603 List of classes of commands:
1605 aliases -- Aliases of other commands
1606 breakpoints -- Making program stop at certain points
1607 data -- Examining data
1608 files -- Specifying and examining files
1609 internals -- Maintenance commands
1610 obscure -- Obscure features
1611 running -- Running the program
1612 stack -- Examining the stack
1613 status -- Status inquiries
1614 support -- Support facilities
1615 tracepoints -- Tracing of program execution without
1616 stopping the program
1617 user-defined -- User-defined commands
1619 Type "help" followed by a class name for a list of
1620 commands in that class.
1621 Type "help" followed by command name for full
1623 Command name abbreviations are allowed if unambiguous.
1626 @c the above line break eliminates huge line overfull...
1628 @item help @var{class}
1629 Using one of the general help classes as an argument, you can get a
1630 list of the individual commands in that class. For example, here is the
1631 help display for the class @code{status}:
1634 (@value{GDBP}) help status
1639 @c Line break in "show" line falsifies real output, but needed
1640 @c to fit in smallbook page size.
1641 info -- Generic command for showing things
1642 about the program being debugged
1643 show -- Generic command for showing things
1646 Type "help" followed by command name for full
1648 Command name abbreviations are allowed if unambiguous.
1652 @item help @var{command}
1653 With a command name as @code{help} argument, @value{GDBN} displays a
1654 short paragraph on how to use that command.
1657 @item apropos @var{args}
1658 The @code{apropos} command searches through all of the @value{GDBN}
1659 commands, and their documentation, for the regular expression specified in
1660 @var{args}. It prints out all matches found. For example:
1671 set symbol-reloading -- Set dynamic symbol table reloading
1672 multiple times in one run
1673 show symbol-reloading -- Show dynamic symbol table reloading
1674 multiple times in one run
1679 @item complete @var{args}
1680 The @code{complete @var{args}} command lists all the possible completions
1681 for the beginning of a command. Use @var{args} to specify the beginning of the
1682 command you want completed. For example:
1688 @noindent results in:
1699 @noindent This is intended for use by @sc{gnu} Emacs.
1702 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1703 and @code{show} to inquire about the state of your program, or the state
1704 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1705 manual introduces each of them in the appropriate context. The listings
1706 under @code{info} and under @code{show} in the Index point to
1707 all the sub-commands. @xref{Index}.
1712 @kindex i @r{(@code{info})}
1714 This command (abbreviated @code{i}) is for describing the state of your
1715 program. For example, you can show the arguments passed to a function
1716 with @code{info args}, list the registers currently in use with @code{info
1717 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1718 You can get a complete list of the @code{info} sub-commands with
1719 @w{@code{help info}}.
1723 You can assign the result of an expression to an environment variable with
1724 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1725 @code{set prompt $}.
1729 In contrast to @code{info}, @code{show} is for describing the state of
1730 @value{GDBN} itself.
1731 You can change most of the things you can @code{show}, by using the
1732 related command @code{set}; for example, you can control what number
1733 system is used for displays with @code{set radix}, or simply inquire
1734 which is currently in use with @code{show radix}.
1737 To display all the settable parameters and their current
1738 values, you can use @code{show} with no arguments; you may also use
1739 @code{info set}. Both commands produce the same display.
1740 @c FIXME: "info set" violates the rule that "info" is for state of
1741 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1742 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1746 Here are three miscellaneous @code{show} subcommands, all of which are
1747 exceptional in lacking corresponding @code{set} commands:
1750 @kindex show version
1751 @cindex @value{GDBN} version number
1753 Show what version of @value{GDBN} is running. You should include this
1754 information in @value{GDBN} bug-reports. If multiple versions of
1755 @value{GDBN} are in use at your site, you may need to determine which
1756 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1757 commands are introduced, and old ones may wither away. Also, many
1758 system vendors ship variant versions of @value{GDBN}, and there are
1759 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1760 The version number is the same as the one announced when you start
1763 @kindex show copying
1764 @kindex info copying
1765 @cindex display @value{GDBN} copyright
1768 Display information about permission for copying @value{GDBN}.
1770 @kindex show warranty
1771 @kindex info warranty
1773 @itemx info warranty
1774 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1775 if your version of @value{GDBN} comes with one.
1780 @chapter Running Programs Under @value{GDBN}
1782 When you run a program under @value{GDBN}, you must first generate
1783 debugging information when you compile it.
1785 You may start @value{GDBN} with its arguments, if any, in an environment
1786 of your choice. If you are doing native debugging, you may redirect
1787 your program's input and output, debug an already running process, or
1788 kill a child process.
1791 * Compilation:: Compiling for debugging
1792 * Starting:: Starting your program
1793 * Arguments:: Your program's arguments
1794 * Environment:: Your program's environment
1796 * Working Directory:: Your program's working directory
1797 * Input/Output:: Your program's input and output
1798 * Attach:: Debugging an already-running process
1799 * Kill Process:: Killing the child process
1801 * Inferiors and Programs:: Debugging multiple inferiors and programs
1802 * Threads:: Debugging programs with multiple threads
1803 * Forks:: Debugging forks
1804 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1808 @section Compiling for Debugging
1810 In order to debug a program effectively, you need to generate
1811 debugging information when you compile it. This debugging information
1812 is stored in the object file; it describes the data type of each
1813 variable or function and the correspondence between source line numbers
1814 and addresses in the executable code.
1816 To request debugging information, specify the @samp{-g} option when you run
1819 Programs that are to be shipped to your customers are compiled with
1820 optimizations, using the @samp{-O} compiler option. However, some
1821 compilers are unable to handle the @samp{-g} and @samp{-O} options
1822 together. Using those compilers, you cannot generate optimized
1823 executables containing debugging information.
1825 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1826 without @samp{-O}, making it possible to debug optimized code. We
1827 recommend that you @emph{always} use @samp{-g} whenever you compile a
1828 program. You may think your program is correct, but there is no sense
1829 in pushing your luck. For more information, see @ref{Optimized Code}.
1831 Older versions of the @sc{gnu} C compiler permitted a variant option
1832 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1833 format; if your @sc{gnu} C compiler has this option, do not use it.
1835 @value{GDBN} knows about preprocessor macros and can show you their
1836 expansion (@pxref{Macros}). Most compilers do not include information
1837 about preprocessor macros in the debugging information if you specify
1838 the @option{-g} flag alone, because this information is rather large.
1839 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1840 provides macro information if you specify the options
1841 @option{-gdwarf-2} and @option{-g3}; the former option requests
1842 debugging information in the Dwarf 2 format, and the latter requests
1843 ``extra information''. In the future, we hope to find more compact
1844 ways to represent macro information, so that it can be included with
1849 @section Starting your Program
1855 @kindex r @r{(@code{run})}
1858 Use the @code{run} command to start your program under @value{GDBN}.
1859 You must first specify the program name (except on VxWorks) with an
1860 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1861 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1862 (@pxref{Files, ,Commands to Specify Files}).
1866 If you are running your program in an execution environment that
1867 supports processes, @code{run} creates an inferior process and makes
1868 that process run your program. In some environments without processes,
1869 @code{run} jumps to the start of your program. Other targets,
1870 like @samp{remote}, are always running. If you get an error
1871 message like this one:
1874 The "remote" target does not support "run".
1875 Try "help target" or "continue".
1879 then use @code{continue} to run your program. You may need @code{load}
1880 first (@pxref{load}).
1882 The execution of a program is affected by certain information it
1883 receives from its superior. @value{GDBN} provides ways to specify this
1884 information, which you must do @emph{before} starting your program. (You
1885 can change it after starting your program, but such changes only affect
1886 your program the next time you start it.) This information may be
1887 divided into four categories:
1890 @item The @emph{arguments.}
1891 Specify the arguments to give your program as the arguments of the
1892 @code{run} command. If a shell is available on your target, the shell
1893 is used to pass the arguments, so that you may use normal conventions
1894 (such as wildcard expansion or variable substitution) in describing
1896 In Unix systems, you can control which shell is used with the
1897 @code{SHELL} environment variable.
1898 @xref{Arguments, ,Your Program's Arguments}.
1900 @item The @emph{environment.}
1901 Your program normally inherits its environment from @value{GDBN}, but you can
1902 use the @value{GDBN} commands @code{set environment} and @code{unset
1903 environment} to change parts of the environment that affect
1904 your program. @xref{Environment, ,Your Program's Environment}.
1906 @item The @emph{working directory.}
1907 Your program inherits its working directory from @value{GDBN}. You can set
1908 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1909 @xref{Working Directory, ,Your Program's Working Directory}.
1911 @item The @emph{standard input and output.}
1912 Your program normally uses the same device for standard input and
1913 standard output as @value{GDBN} is using. You can redirect input and output
1914 in the @code{run} command line, or you can use the @code{tty} command to
1915 set a different device for your program.
1916 @xref{Input/Output, ,Your Program's Input and Output}.
1919 @emph{Warning:} While input and output redirection work, you cannot use
1920 pipes to pass the output of the program you are debugging to another
1921 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1925 When you issue the @code{run} command, your program begins to execute
1926 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1927 of how to arrange for your program to stop. Once your program has
1928 stopped, you may call functions in your program, using the @code{print}
1929 or @code{call} commands. @xref{Data, ,Examining Data}.
1931 If the modification time of your symbol file has changed since the last
1932 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1933 table, and reads it again. When it does this, @value{GDBN} tries to retain
1934 your current breakpoints.
1939 @cindex run to main procedure
1940 The name of the main procedure can vary from language to language.
1941 With C or C@t{++}, the main procedure name is always @code{main}, but
1942 other languages such as Ada do not require a specific name for their
1943 main procedure. The debugger provides a convenient way to start the
1944 execution of the program and to stop at the beginning of the main
1945 procedure, depending on the language used.
1947 The @samp{start} command does the equivalent of setting a temporary
1948 breakpoint at the beginning of the main procedure and then invoking
1949 the @samp{run} command.
1951 @cindex elaboration phase
1952 Some programs contain an @dfn{elaboration} phase where some startup code is
1953 executed before the main procedure is called. This depends on the
1954 languages used to write your program. In C@t{++}, for instance,
1955 constructors for static and global objects are executed before
1956 @code{main} is called. It is therefore possible that the debugger stops
1957 before reaching the main procedure. However, the temporary breakpoint
1958 will remain to halt execution.
1960 Specify the arguments to give to your program as arguments to the
1961 @samp{start} command. These arguments will be given verbatim to the
1962 underlying @samp{run} command. Note that the same arguments will be
1963 reused if no argument is provided during subsequent calls to
1964 @samp{start} or @samp{run}.
1966 It is sometimes necessary to debug the program during elaboration. In
1967 these cases, using the @code{start} command would stop the execution of
1968 your program too late, as the program would have already completed the
1969 elaboration phase. Under these circumstances, insert breakpoints in your
1970 elaboration code before running your program.
1972 @kindex set exec-wrapper
1973 @item set exec-wrapper @var{wrapper}
1974 @itemx show exec-wrapper
1975 @itemx unset exec-wrapper
1976 When @samp{exec-wrapper} is set, the specified wrapper is used to
1977 launch programs for debugging. @value{GDBN} starts your program
1978 with a shell command of the form @kbd{exec @var{wrapper}
1979 @var{program}}. Quoting is added to @var{program} and its
1980 arguments, but not to @var{wrapper}, so you should add quotes if
1981 appropriate for your shell. The wrapper runs until it executes
1982 your program, and then @value{GDBN} takes control.
1984 You can use any program that eventually calls @code{execve} with
1985 its arguments as a wrapper. Several standard Unix utilities do
1986 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1987 with @code{exec "$@@"} will also work.
1989 For example, you can use @code{env} to pass an environment variable to
1990 the debugged program, without setting the variable in your shell's
1994 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
1998 This command is available when debugging locally on most targets, excluding
1999 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2001 @kindex set disable-randomization
2002 @item set disable-randomization
2003 @itemx set disable-randomization on
2004 This option (enabled by default in @value{GDBN}) will turn off the native
2005 randomization of the virtual address space of the started program. This option
2006 is useful for multiple debugging sessions to make the execution better
2007 reproducible and memory addresses reusable across debugging sessions.
2009 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2013 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2016 @item set disable-randomization off
2017 Leave the behavior of the started executable unchanged. Some bugs rear their
2018 ugly heads only when the program is loaded at certain addresses. If your bug
2019 disappears when you run the program under @value{GDBN}, that might be because
2020 @value{GDBN} by default disables the address randomization on platforms, such
2021 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2022 disable-randomization off} to try to reproduce such elusive bugs.
2024 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2025 It protects the programs against some kinds of security attacks. In these
2026 cases the attacker needs to know the exact location of a concrete executable
2027 code. Randomizing its location makes it impossible to inject jumps misusing
2028 a code at its expected addresses.
2030 Prelinking shared libraries provides a startup performance advantage but it
2031 makes addresses in these libraries predictable for privileged processes by
2032 having just unprivileged access at the target system. Reading the shared
2033 library binary gives enough information for assembling the malicious code
2034 misusing it. Still even a prelinked shared library can get loaded at a new
2035 random address just requiring the regular relocation process during the
2036 startup. Shared libraries not already prelinked are always loaded at
2037 a randomly chosen address.
2039 Position independent executables (PIE) contain position independent code
2040 similar to the shared libraries and therefore such executables get loaded at
2041 a randomly chosen address upon startup. PIE executables always load even
2042 already prelinked shared libraries at a random address. You can build such
2043 executable using @command{gcc -fPIE -pie}.
2045 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2046 (as long as the randomization is enabled).
2048 @item show disable-randomization
2049 Show the current setting of the explicit disable of the native randomization of
2050 the virtual address space of the started program.
2055 @section Your Program's Arguments
2057 @cindex arguments (to your program)
2058 The arguments to your program can be specified by the arguments of the
2060 They are passed to a shell, which expands wildcard characters and
2061 performs redirection of I/O, and thence to your program. Your
2062 @code{SHELL} environment variable (if it exists) specifies what shell
2063 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2064 the default shell (@file{/bin/sh} on Unix).
2066 On non-Unix systems, the program is usually invoked directly by
2067 @value{GDBN}, which emulates I/O redirection via the appropriate system
2068 calls, and the wildcard characters are expanded by the startup code of
2069 the program, not by the shell.
2071 @code{run} with no arguments uses the same arguments used by the previous
2072 @code{run}, or those set by the @code{set args} command.
2077 Specify the arguments to be used the next time your program is run. If
2078 @code{set args} has no arguments, @code{run} executes your program
2079 with no arguments. Once you have run your program with arguments,
2080 using @code{set args} before the next @code{run} is the only way to run
2081 it again without arguments.
2085 Show the arguments to give your program when it is started.
2089 @section Your Program's Environment
2091 @cindex environment (of your program)
2092 The @dfn{environment} consists of a set of environment variables and
2093 their values. Environment variables conventionally record such things as
2094 your user name, your home directory, your terminal type, and your search
2095 path for programs to run. Usually you set up environment variables with
2096 the shell and they are inherited by all the other programs you run. When
2097 debugging, it can be useful to try running your program with a modified
2098 environment without having to start @value{GDBN} over again.
2102 @item path @var{directory}
2103 Add @var{directory} to the front of the @code{PATH} environment variable
2104 (the search path for executables) that will be passed to your program.
2105 The value of @code{PATH} used by @value{GDBN} does not change.
2106 You may specify several directory names, separated by whitespace or by a
2107 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2108 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2109 is moved to the front, so it is searched sooner.
2111 You can use the string @samp{$cwd} to refer to whatever is the current
2112 working directory at the time @value{GDBN} searches the path. If you
2113 use @samp{.} instead, it refers to the directory where you executed the
2114 @code{path} command. @value{GDBN} replaces @samp{.} in the
2115 @var{directory} argument (with the current path) before adding
2116 @var{directory} to the search path.
2117 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2118 @c document that, since repeating it would be a no-op.
2122 Display the list of search paths for executables (the @code{PATH}
2123 environment variable).
2125 @kindex show environment
2126 @item show environment @r{[}@var{varname}@r{]}
2127 Print the value of environment variable @var{varname} to be given to
2128 your program when it starts. If you do not supply @var{varname},
2129 print the names and values of all environment variables to be given to
2130 your program. You can abbreviate @code{environment} as @code{env}.
2132 @kindex set environment
2133 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2134 Set environment variable @var{varname} to @var{value}. The value
2135 changes for your program only, not for @value{GDBN} itself. @var{value} may
2136 be any string; the values of environment variables are just strings, and
2137 any interpretation is supplied by your program itself. The @var{value}
2138 parameter is optional; if it is eliminated, the variable is set to a
2140 @c "any string" here does not include leading, trailing
2141 @c blanks. Gnu asks: does anyone care?
2143 For example, this command:
2150 tells the debugged program, when subsequently run, that its user is named
2151 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2152 are not actually required.)
2154 @kindex unset environment
2155 @item unset environment @var{varname}
2156 Remove variable @var{varname} from the environment to be passed to your
2157 program. This is different from @samp{set env @var{varname} =};
2158 @code{unset environment} removes the variable from the environment,
2159 rather than assigning it an empty value.
2162 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2164 by your @code{SHELL} environment variable if it exists (or
2165 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2166 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2167 @file{.bashrc} for BASH---any variables you set in that file affect
2168 your program. You may wish to move setting of environment variables to
2169 files that are only run when you sign on, such as @file{.login} or
2172 @node Working Directory
2173 @section Your Program's Working Directory
2175 @cindex working directory (of your program)
2176 Each time you start your program with @code{run}, it inherits its
2177 working directory from the current working directory of @value{GDBN}.
2178 The @value{GDBN} working directory is initially whatever it inherited
2179 from its parent process (typically the shell), but you can specify a new
2180 working directory in @value{GDBN} with the @code{cd} command.
2182 The @value{GDBN} working directory also serves as a default for the commands
2183 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2188 @cindex change working directory
2189 @item cd @var{directory}
2190 Set the @value{GDBN} working directory to @var{directory}.
2194 Print the @value{GDBN} working directory.
2197 It is generally impossible to find the current working directory of
2198 the process being debugged (since a program can change its directory
2199 during its run). If you work on a system where @value{GDBN} is
2200 configured with the @file{/proc} support, you can use the @code{info
2201 proc} command (@pxref{SVR4 Process Information}) to find out the
2202 current working directory of the debuggee.
2205 @section Your Program's Input and Output
2210 By default, the program you run under @value{GDBN} does input and output to
2211 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2212 to its own terminal modes to interact with you, but it records the terminal
2213 modes your program was using and switches back to them when you continue
2214 running your program.
2217 @kindex info terminal
2219 Displays information recorded by @value{GDBN} about the terminal modes your
2223 You can redirect your program's input and/or output using shell
2224 redirection with the @code{run} command. For example,
2231 starts your program, diverting its output to the file @file{outfile}.
2234 @cindex controlling terminal
2235 Another way to specify where your program should do input and output is
2236 with the @code{tty} command. This command accepts a file name as
2237 argument, and causes this file to be the default for future @code{run}
2238 commands. It also resets the controlling terminal for the child
2239 process, for future @code{run} commands. For example,
2246 directs that processes started with subsequent @code{run} commands
2247 default to do input and output on the terminal @file{/dev/ttyb} and have
2248 that as their controlling terminal.
2250 An explicit redirection in @code{run} overrides the @code{tty} command's
2251 effect on the input/output device, but not its effect on the controlling
2254 When you use the @code{tty} command or redirect input in the @code{run}
2255 command, only the input @emph{for your program} is affected. The input
2256 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2257 for @code{set inferior-tty}.
2259 @cindex inferior tty
2260 @cindex set inferior controlling terminal
2261 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2262 display the name of the terminal that will be used for future runs of your
2266 @item set inferior-tty /dev/ttyb
2267 @kindex set inferior-tty
2268 Set the tty for the program being debugged to /dev/ttyb.
2270 @item show inferior-tty
2271 @kindex show inferior-tty
2272 Show the current tty for the program being debugged.
2276 @section Debugging an Already-running Process
2281 @item attach @var{process-id}
2282 This command attaches to a running process---one that was started
2283 outside @value{GDBN}. (@code{info files} shows your active
2284 targets.) The command takes as argument a process ID. The usual way to
2285 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2286 or with the @samp{jobs -l} shell command.
2288 @code{attach} does not repeat if you press @key{RET} a second time after
2289 executing the command.
2292 To use @code{attach}, your program must be running in an environment
2293 which supports processes; for example, @code{attach} does not work for
2294 programs on bare-board targets that lack an operating system. You must
2295 also have permission to send the process a signal.
2297 When you use @code{attach}, the debugger finds the program running in
2298 the process first by looking in the current working directory, then (if
2299 the program is not found) by using the source file search path
2300 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2301 the @code{file} command to load the program. @xref{Files, ,Commands to
2304 The first thing @value{GDBN} does after arranging to debug the specified
2305 process is to stop it. You can examine and modify an attached process
2306 with all the @value{GDBN} commands that are ordinarily available when
2307 you start processes with @code{run}. You can insert breakpoints; you
2308 can step and continue; you can modify storage. If you would rather the
2309 process continue running, you may use the @code{continue} command after
2310 attaching @value{GDBN} to the process.
2315 When you have finished debugging the attached process, you can use the
2316 @code{detach} command to release it from @value{GDBN} control. Detaching
2317 the process continues its execution. After the @code{detach} command,
2318 that process and @value{GDBN} become completely independent once more, and you
2319 are ready to @code{attach} another process or start one with @code{run}.
2320 @code{detach} does not repeat if you press @key{RET} again after
2321 executing the command.
2324 If you exit @value{GDBN} while you have an attached process, you detach
2325 that process. If you use the @code{run} command, you kill that process.
2326 By default, @value{GDBN} asks for confirmation if you try to do either of these
2327 things; you can control whether or not you need to confirm by using the
2328 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2332 @section Killing the Child Process
2337 Kill the child process in which your program is running under @value{GDBN}.
2340 This command is useful if you wish to debug a core dump instead of a
2341 running process. @value{GDBN} ignores any core dump file while your program
2344 On some operating systems, a program cannot be executed outside @value{GDBN}
2345 while you have breakpoints set on it inside @value{GDBN}. You can use the
2346 @code{kill} command in this situation to permit running your program
2347 outside the debugger.
2349 The @code{kill} command is also useful if you wish to recompile and
2350 relink your program, since on many systems it is impossible to modify an
2351 executable file while it is running in a process. In this case, when you
2352 next type @code{run}, @value{GDBN} notices that the file has changed, and
2353 reads the symbol table again (while trying to preserve your current
2354 breakpoint settings).
2356 @node Inferiors and Programs
2357 @section Debugging Multiple Inferiors and Programs
2359 @value{GDBN} lets you run and debug multiple programs in a single
2360 session. In addition, @value{GDBN} on some systems may let you run
2361 several programs simultaneously (otherwise you have to exit from one
2362 before starting another). In the most general case, you can have
2363 multiple threads of execution in each of multiple processes, launched
2364 from multiple executables.
2367 @value{GDBN} represents the state of each program execution with an
2368 object called an @dfn{inferior}. An inferior typically corresponds to
2369 a process, but is more general and applies also to targets that do not
2370 have processes. Inferiors may be created before a process runs, and
2371 may be retained after a process exits. Inferiors have unique
2372 identifiers that are different from process ids. Usually each
2373 inferior will also have its own distinct address space, although some
2374 embedded targets may have several inferiors running in different parts
2375 of a single address space. Each inferior may in turn have multiple
2376 threads running in it.
2378 To find out what inferiors exist at any moment, use @w{@code{info
2382 @kindex info inferiors
2383 @item info inferiors
2384 Print a list of all inferiors currently being managed by @value{GDBN}.
2386 @value{GDBN} displays for each inferior (in this order):
2390 the inferior number assigned by @value{GDBN}
2393 the target system's inferior identifier
2396 the name of the executable the inferior is running.
2401 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2402 indicates the current inferior.
2406 @c end table here to get a little more width for example
2409 (@value{GDBP}) info inferiors
2410 Num Description Executable
2411 2 process 2307 hello
2412 * 1 process 3401 goodbye
2415 To switch focus between inferiors, use the @code{inferior} command:
2418 @kindex inferior @var{infno}
2419 @item inferior @var{infno}
2420 Make inferior number @var{infno} the current inferior. The argument
2421 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2422 in the first field of the @samp{info inferiors} display.
2426 You can get multiple executables into a debugging session via the
2427 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2428 systems @value{GDBN} can add inferiors to the debug session
2429 automatically by following calls to @code{fork} and @code{exec}. To
2430 remove inferiors from the debugging session use the
2431 @w{@code{remove-inferior}} command.
2434 @kindex add-inferior
2435 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2436 Adds @var{n} inferiors to be run using @var{executable} as the
2437 executable. @var{n} defaults to 1. If no executable is specified,
2438 the inferiors begins empty, with no program. You can still assign or
2439 change the program assigned to the inferior at any time by using the
2440 @code{file} command with the executable name as its argument.
2442 @kindex clone-inferior
2443 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2444 Adds @var{n} inferiors ready to execute the same program as inferior
2445 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2446 number of the current inferior. This is a convenient command when you
2447 want to run another instance of the inferior you are debugging.
2450 (@value{GDBP}) info inferiors
2451 Num Description Executable
2452 * 1 process 29964 helloworld
2453 (@value{GDBP}) clone-inferior
2456 (@value{GDBP}) info inferiors
2457 Num Description Executable
2459 * 1 process 29964 helloworld
2462 You can now simply switch focus to inferior 2 and run it.
2464 @kindex remove-inferior
2465 @item remove-inferior @var{infno}
2466 Removes the inferior @var{infno}. It is not possible to remove an
2467 inferior that is running with this command. For those, use the
2468 @code{kill} or @code{detach} command first.
2472 To quit debugging one of the running inferiors that is not the current
2473 inferior, you can either detach from it by using the @w{@code{detach
2474 inferior}} command (allowing it to run independently), or kill it
2475 using the @w{@code{kill inferior}} command:
2478 @kindex detach inferior @var{infno}
2479 @item detach inferior @var{infno}
2480 Detach from the inferior identified by @value{GDBN} inferior number
2481 @var{infno}, and remove it from the inferior list.
2483 @kindex kill inferior @var{infno}
2484 @item kill inferior @var{infno}
2485 Kill the inferior identified by @value{GDBN} inferior number
2486 @var{infno}, and remove it from the inferior list.
2489 After the successful completion of a command such as @code{detach},
2490 @code{detach inferior}, @code{kill} or @code{kill inferior}, or after
2491 a normal process exit, the inferior is still valid and listed with
2492 @code{info inferiors}, ready to be restarted.
2495 To be notified when inferiors are started or exit under @value{GDBN}'s
2496 control use @w{@code{set print inferior-events}}:
2499 @kindex set print inferior-events
2500 @cindex print messages on inferior start and exit
2501 @item set print inferior-events
2502 @itemx set print inferior-events on
2503 @itemx set print inferior-events off
2504 The @code{set print inferior-events} command allows you to enable or
2505 disable printing of messages when @value{GDBN} notices that new
2506 inferiors have started or that inferiors have exited or have been
2507 detached. By default, these messages will not be printed.
2509 @kindex show print inferior-events
2510 @item show print inferior-events
2511 Show whether messages will be printed when @value{GDBN} detects that
2512 inferiors have started, exited or have been detached.
2515 Many commands will work the same with multiple programs as with a
2516 single program: e.g., @code{print myglobal} will simply display the
2517 value of @code{myglobal} in the current inferior.
2520 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2521 get more info about the relationship of inferiors, programs, address
2522 spaces in a debug session. You can do that with the @w{@code{maint
2523 info program-spaces}} command.
2526 @kindex maint info program-spaces
2527 @item maint info program-spaces
2528 Print a list of all program spaces currently being managed by
2531 @value{GDBN} displays for each program space (in this order):
2535 the program space number assigned by @value{GDBN}
2538 the name of the executable loaded into the program space, with e.g.,
2539 the @code{file} command.
2544 An asterisk @samp{*} preceding the @value{GDBN} program space number
2545 indicates the current program space.
2547 In addition, below each program space line, @value{GDBN} prints extra
2548 information that isn't suitable to display in tabular form. For
2549 example, the list of inferiors bound to the program space.
2552 (@value{GDBP}) maint info program-spaces
2555 Bound inferiors: ID 1 (process 21561)
2559 Here we can see that no inferior is running the program @code{hello},
2560 while @code{process 21561} is running the program @code{goodbye}. On
2561 some targets, it is possible that multiple inferiors are bound to the
2562 same program space. The most common example is that of debugging both
2563 the parent and child processes of a @code{vfork} call. For example,
2566 (@value{GDBP}) maint info program-spaces
2569 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2572 Here, both inferior 2 and inferior 1 are running in the same program
2573 space as a result of inferior 1 having executed a @code{vfork} call.
2577 @section Debugging Programs with Multiple Threads
2579 @cindex threads of execution
2580 @cindex multiple threads
2581 @cindex switching threads
2582 In some operating systems, such as HP-UX and Solaris, a single program
2583 may have more than one @dfn{thread} of execution. The precise semantics
2584 of threads differ from one operating system to another, but in general
2585 the threads of a single program are akin to multiple processes---except
2586 that they share one address space (that is, they can all examine and
2587 modify the same variables). On the other hand, each thread has its own
2588 registers and execution stack, and perhaps private memory.
2590 @value{GDBN} provides these facilities for debugging multi-thread
2594 @item automatic notification of new threads
2595 @item @samp{thread @var{threadno}}, a command to switch among threads
2596 @item @samp{info threads}, a command to inquire about existing threads
2597 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2598 a command to apply a command to a list of threads
2599 @item thread-specific breakpoints
2600 @item @samp{set print thread-events}, which controls printing of
2601 messages on thread start and exit.
2602 @item @samp{set libthread-db-search-path @var{path}}, which lets
2603 the user specify which @code{libthread_db} to use if the default choice
2604 isn't compatible with the program.
2608 @emph{Warning:} These facilities are not yet available on every
2609 @value{GDBN} configuration where the operating system supports threads.
2610 If your @value{GDBN} does not support threads, these commands have no
2611 effect. For example, a system without thread support shows no output
2612 from @samp{info threads}, and always rejects the @code{thread} command,
2616 (@value{GDBP}) info threads
2617 (@value{GDBP}) thread 1
2618 Thread ID 1 not known. Use the "info threads" command to
2619 see the IDs of currently known threads.
2621 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2622 @c doesn't support threads"?
2625 @cindex focus of debugging
2626 @cindex current thread
2627 The @value{GDBN} thread debugging facility allows you to observe all
2628 threads while your program runs---but whenever @value{GDBN} takes
2629 control, one thread in particular is always the focus of debugging.
2630 This thread is called the @dfn{current thread}. Debugging commands show
2631 program information from the perspective of the current thread.
2633 @cindex @code{New} @var{systag} message
2634 @cindex thread identifier (system)
2635 @c FIXME-implementors!! It would be more helpful if the [New...] message
2636 @c included GDB's numeric thread handle, so you could just go to that
2637 @c thread without first checking `info threads'.
2638 Whenever @value{GDBN} detects a new thread in your program, it displays
2639 the target system's identification for the thread with a message in the
2640 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2641 whose form varies depending on the particular system. For example, on
2642 @sc{gnu}/Linux, you might see
2645 [New Thread 46912507313328 (LWP 25582)]
2649 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2650 the @var{systag} is simply something like @samp{process 368}, with no
2653 @c FIXME!! (1) Does the [New...] message appear even for the very first
2654 @c thread of a program, or does it only appear for the
2655 @c second---i.e.@: when it becomes obvious we have a multithread
2657 @c (2) *Is* there necessarily a first thread always? Or do some
2658 @c multithread systems permit starting a program with multiple
2659 @c threads ab initio?
2661 @cindex thread number
2662 @cindex thread identifier (GDB)
2663 For debugging purposes, @value{GDBN} associates its own thread
2664 number---always a single integer---with each thread in your program.
2667 @kindex info threads
2669 Display a summary of all threads currently in your
2670 program. @value{GDBN} displays for each thread (in this order):
2674 the thread number assigned by @value{GDBN}
2677 the target system's thread identifier (@var{systag})
2680 the current stack frame summary for that thread
2684 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2685 indicates the current thread.
2689 @c end table here to get a little more width for example
2692 (@value{GDBP}) info threads
2693 3 process 35 thread 27 0x34e5 in sigpause ()
2694 2 process 35 thread 23 0x34e5 in sigpause ()
2695 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2701 @cindex debugging multithreaded programs (on HP-UX)
2702 @cindex thread identifier (GDB), on HP-UX
2703 For debugging purposes, @value{GDBN} associates its own thread
2704 number---a small integer assigned in thread-creation order---with each
2705 thread in your program.
2707 @cindex @code{New} @var{systag} message, on HP-UX
2708 @cindex thread identifier (system), on HP-UX
2709 @c FIXME-implementors!! It would be more helpful if the [New...] message
2710 @c included GDB's numeric thread handle, so you could just go to that
2711 @c thread without first checking `info threads'.
2712 Whenever @value{GDBN} detects a new thread in your program, it displays
2713 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2714 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2715 whose form varies depending on the particular system. For example, on
2719 [New thread 2 (system thread 26594)]
2723 when @value{GDBN} notices a new thread.
2726 @kindex info threads (HP-UX)
2728 Display a summary of all threads currently in your
2729 program. @value{GDBN} displays for each thread (in this order):
2732 @item the thread number assigned by @value{GDBN}
2734 @item the target system's thread identifier (@var{systag})
2736 @item the current stack frame summary for that thread
2740 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2741 indicates the current thread.
2745 @c end table here to get a little more width for example
2748 (@value{GDBP}) info threads
2749 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2751 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2752 from /usr/lib/libc.2
2753 1 system thread 27905 0x7b003498 in _brk () \@*
2754 from /usr/lib/libc.2
2757 On Solaris, you can display more information about user threads with a
2758 Solaris-specific command:
2761 @item maint info sol-threads
2762 @kindex maint info sol-threads
2763 @cindex thread info (Solaris)
2764 Display info on Solaris user threads.
2768 @kindex thread @var{threadno}
2769 @item thread @var{threadno}
2770 Make thread number @var{threadno} the current thread. The command
2771 argument @var{threadno} is the internal @value{GDBN} thread number, as
2772 shown in the first field of the @samp{info threads} display.
2773 @value{GDBN} responds by displaying the system identifier of the thread
2774 you selected, and its current stack frame summary:
2777 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2778 (@value{GDBP}) thread 2
2779 [Switching to process 35 thread 23]
2780 0x34e5 in sigpause ()
2784 As with the @samp{[New @dots{}]} message, the form of the text after
2785 @samp{Switching to} depends on your system's conventions for identifying
2788 @kindex thread apply
2789 @cindex apply command to several threads
2790 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2791 The @code{thread apply} command allows you to apply the named
2792 @var{command} to one or more threads. Specify the numbers of the
2793 threads that you want affected with the command argument
2794 @var{threadno}. It can be a single thread number, one of the numbers
2795 shown in the first field of the @samp{info threads} display; or it
2796 could be a range of thread numbers, as in @code{2-4}. To apply a
2797 command to all threads, type @kbd{thread apply all @var{command}}.
2799 @kindex set print thread-events
2800 @cindex print messages on thread start and exit
2801 @item set print thread-events
2802 @itemx set print thread-events on
2803 @itemx set print thread-events off
2804 The @code{set print thread-events} command allows you to enable or
2805 disable printing of messages when @value{GDBN} notices that new threads have
2806 started or that threads have exited. By default, these messages will
2807 be printed if detection of these events is supported by the target.
2808 Note that these messages cannot be disabled on all targets.
2810 @kindex show print thread-events
2811 @item show print thread-events
2812 Show whether messages will be printed when @value{GDBN} detects that threads
2813 have started and exited.
2816 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2817 more information about how @value{GDBN} behaves when you stop and start
2818 programs with multiple threads.
2820 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2821 watchpoints in programs with multiple threads.
2824 @kindex set libthread-db-search-path
2825 @cindex search path for @code{libthread_db}
2826 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2827 If this variable is set, @var{path} is a colon-separated list of
2828 directories @value{GDBN} will use to search for @code{libthread_db}.
2829 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2832 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2833 @code{libthread_db} library to obtain information about threads in the
2834 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2835 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2836 with default system shared library directories, and finally the directory
2837 from which @code{libpthread} was loaded in the inferior process.
2839 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2840 @value{GDBN} attempts to initialize it with the current inferior process.
2841 If this initialization fails (which could happen because of a version
2842 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2843 will unload @code{libthread_db}, and continue with the next directory.
2844 If none of @code{libthread_db} libraries initialize successfully,
2845 @value{GDBN} will issue a warning and thread debugging will be disabled.
2847 Setting @code{libthread-db-search-path} is currently implemented
2848 only on some platforms.
2850 @kindex show libthread-db-search-path
2851 @item show libthread-db-search-path
2852 Display current libthread_db search path.
2856 @section Debugging Forks
2858 @cindex fork, debugging programs which call
2859 @cindex multiple processes
2860 @cindex processes, multiple
2861 On most systems, @value{GDBN} has no special support for debugging
2862 programs which create additional processes using the @code{fork}
2863 function. When a program forks, @value{GDBN} will continue to debug the
2864 parent process and the child process will run unimpeded. If you have
2865 set a breakpoint in any code which the child then executes, the child
2866 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2867 will cause it to terminate.
2869 However, if you want to debug the child process there is a workaround
2870 which isn't too painful. Put a call to @code{sleep} in the code which
2871 the child process executes after the fork. It may be useful to sleep
2872 only if a certain environment variable is set, or a certain file exists,
2873 so that the delay need not occur when you don't want to run @value{GDBN}
2874 on the child. While the child is sleeping, use the @code{ps} program to
2875 get its process ID. Then tell @value{GDBN} (a new invocation of
2876 @value{GDBN} if you are also debugging the parent process) to attach to
2877 the child process (@pxref{Attach}). From that point on you can debug
2878 the child process just like any other process which you attached to.
2880 On some systems, @value{GDBN} provides support for debugging programs that
2881 create additional processes using the @code{fork} or @code{vfork} functions.
2882 Currently, the only platforms with this feature are HP-UX (11.x and later
2883 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2885 By default, when a program forks, @value{GDBN} will continue to debug
2886 the parent process and the child process will run unimpeded.
2888 If you want to follow the child process instead of the parent process,
2889 use the command @w{@code{set follow-fork-mode}}.
2892 @kindex set follow-fork-mode
2893 @item set follow-fork-mode @var{mode}
2894 Set the debugger response to a program call of @code{fork} or
2895 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2896 process. The @var{mode} argument can be:
2900 The original process is debugged after a fork. The child process runs
2901 unimpeded. This is the default.
2904 The new process is debugged after a fork. The parent process runs
2909 @kindex show follow-fork-mode
2910 @item show follow-fork-mode
2911 Display the current debugger response to a @code{fork} or @code{vfork} call.
2914 @cindex debugging multiple processes
2915 On Linux, if you want to debug both the parent and child processes, use the
2916 command @w{@code{set detach-on-fork}}.
2919 @kindex set detach-on-fork
2920 @item set detach-on-fork @var{mode}
2921 Tells gdb whether to detach one of the processes after a fork, or
2922 retain debugger control over them both.
2926 The child process (or parent process, depending on the value of
2927 @code{follow-fork-mode}) will be detached and allowed to run
2928 independently. This is the default.
2931 Both processes will be held under the control of @value{GDBN}.
2932 One process (child or parent, depending on the value of
2933 @code{follow-fork-mode}) is debugged as usual, while the other
2938 @kindex show detach-on-fork
2939 @item show detach-on-fork
2940 Show whether detach-on-fork mode is on/off.
2943 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2944 will retain control of all forked processes (including nested forks).
2945 You can list the forked processes under the control of @value{GDBN} by
2946 using the @w{@code{info inferiors}} command, and switch from one fork
2947 to another by using the @code{inferior} command (@pxref{Inferiors and
2948 Programs, ,Debugging Multiple Inferiors and Programs}).
2950 To quit debugging one of the forked processes, you can either detach
2951 from it by using the @w{@code{detach inferior}} command (allowing it
2952 to run independently), or kill it using the @w{@code{kill inferior}}
2953 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2956 If you ask to debug a child process and a @code{vfork} is followed by an
2957 @code{exec}, @value{GDBN} executes the new target up to the first
2958 breakpoint in the new target. If you have a breakpoint set on
2959 @code{main} in your original program, the breakpoint will also be set on
2960 the child process's @code{main}.
2962 On some systems, when a child process is spawned by @code{vfork}, you
2963 cannot debug the child or parent until an @code{exec} call completes.
2965 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2966 call executes, the new target restarts. To restart the parent
2967 process, use the @code{file} command with the parent executable name
2968 as its argument. By default, after an @code{exec} call executes,
2969 @value{GDBN} discards the symbols of the previous executable image.
2970 You can change this behaviour with the @w{@code{set follow-exec-mode}}
2974 @kindex set follow-exec-mode
2975 @item set follow-exec-mode @var{mode}
2977 Set debugger response to a program call of @code{exec}. An
2978 @code{exec} call replaces the program image of a process.
2980 @code{follow-exec-mode} can be:
2984 @value{GDBN} creates a new inferior and rebinds the process to this
2985 new inferior. The program the process was running before the
2986 @code{exec} call can be restarted afterwards by restarting the
2992 (@value{GDBP}) info inferiors
2994 Id Description Executable
2997 process 12020 is executing new program: prog2
2998 Program exited normally.
2999 (@value{GDBP}) info inferiors
3000 Id Description Executable
3006 @value{GDBN} keeps the process bound to the same inferior. The new
3007 executable image replaces the previous executable loaded in the
3008 inferior. Restarting the inferior after the @code{exec} call, with
3009 e.g., the @code{run} command, restarts the executable the process was
3010 running after the @code{exec} call. This is the default mode.
3015 (@value{GDBP}) info inferiors
3016 Id Description Executable
3019 process 12020 is executing new program: prog2
3020 Program exited normally.
3021 (@value{GDBP}) info inferiors
3022 Id Description Executable
3029 You can use the @code{catch} command to make @value{GDBN} stop whenever
3030 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3031 Catchpoints, ,Setting Catchpoints}.
3033 @node Checkpoint/Restart
3034 @section Setting a @emph{Bookmark} to Return to Later
3039 @cindex snapshot of a process
3040 @cindex rewind program state
3042 On certain operating systems@footnote{Currently, only
3043 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3044 program's state, called a @dfn{checkpoint}, and come back to it
3047 Returning to a checkpoint effectively undoes everything that has
3048 happened in the program since the @code{checkpoint} was saved. This
3049 includes changes in memory, registers, and even (within some limits)
3050 system state. Effectively, it is like going back in time to the
3051 moment when the checkpoint was saved.
3053 Thus, if you're stepping thru a program and you think you're
3054 getting close to the point where things go wrong, you can save
3055 a checkpoint. Then, if you accidentally go too far and miss
3056 the critical statement, instead of having to restart your program
3057 from the beginning, you can just go back to the checkpoint and
3058 start again from there.
3060 This can be especially useful if it takes a lot of time or
3061 steps to reach the point where you think the bug occurs.
3063 To use the @code{checkpoint}/@code{restart} method of debugging:
3068 Save a snapshot of the debugged program's current execution state.
3069 The @code{checkpoint} command takes no arguments, but each checkpoint
3070 is assigned a small integer id, similar to a breakpoint id.
3072 @kindex info checkpoints
3073 @item info checkpoints
3074 List the checkpoints that have been saved in the current debugging
3075 session. For each checkpoint, the following information will be
3082 @item Source line, or label
3085 @kindex restart @var{checkpoint-id}
3086 @item restart @var{checkpoint-id}
3087 Restore the program state that was saved as checkpoint number
3088 @var{checkpoint-id}. All program variables, registers, stack frames
3089 etc.@: will be returned to the values that they had when the checkpoint
3090 was saved. In essence, gdb will ``wind back the clock'' to the point
3091 in time when the checkpoint was saved.
3093 Note that breakpoints, @value{GDBN} variables, command history etc.
3094 are not affected by restoring a checkpoint. In general, a checkpoint
3095 only restores things that reside in the program being debugged, not in
3098 @kindex delete checkpoint @var{checkpoint-id}
3099 @item delete checkpoint @var{checkpoint-id}
3100 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3104 Returning to a previously saved checkpoint will restore the user state
3105 of the program being debugged, plus a significant subset of the system
3106 (OS) state, including file pointers. It won't ``un-write'' data from
3107 a file, but it will rewind the file pointer to the previous location,
3108 so that the previously written data can be overwritten. For files
3109 opened in read mode, the pointer will also be restored so that the
3110 previously read data can be read again.
3112 Of course, characters that have been sent to a printer (or other
3113 external device) cannot be ``snatched back'', and characters received
3114 from eg.@: a serial device can be removed from internal program buffers,
3115 but they cannot be ``pushed back'' into the serial pipeline, ready to
3116 be received again. Similarly, the actual contents of files that have
3117 been changed cannot be restored (at this time).
3119 However, within those constraints, you actually can ``rewind'' your
3120 program to a previously saved point in time, and begin debugging it
3121 again --- and you can change the course of events so as to debug a
3122 different execution path this time.
3124 @cindex checkpoints and process id
3125 Finally, there is one bit of internal program state that will be
3126 different when you return to a checkpoint --- the program's process
3127 id. Each checkpoint will have a unique process id (or @var{pid}),
3128 and each will be different from the program's original @var{pid}.
3129 If your program has saved a local copy of its process id, this could
3130 potentially pose a problem.
3132 @subsection A Non-obvious Benefit of Using Checkpoints
3134 On some systems such as @sc{gnu}/Linux, address space randomization
3135 is performed on new processes for security reasons. This makes it
3136 difficult or impossible to set a breakpoint, or watchpoint, on an
3137 absolute address if you have to restart the program, since the
3138 absolute location of a symbol will change from one execution to the
3141 A checkpoint, however, is an @emph{identical} copy of a process.
3142 Therefore if you create a checkpoint at (eg.@:) the start of main,
3143 and simply return to that checkpoint instead of restarting the
3144 process, you can avoid the effects of address randomization and
3145 your symbols will all stay in the same place.
3148 @chapter Stopping and Continuing
3150 The principal purposes of using a debugger are so that you can stop your
3151 program before it terminates; or so that, if your program runs into
3152 trouble, you can investigate and find out why.
3154 Inside @value{GDBN}, your program may stop for any of several reasons,
3155 such as a signal, a breakpoint, or reaching a new line after a
3156 @value{GDBN} command such as @code{step}. You may then examine and
3157 change variables, set new breakpoints or remove old ones, and then
3158 continue execution. Usually, the messages shown by @value{GDBN} provide
3159 ample explanation of the status of your program---but you can also
3160 explicitly request this information at any time.
3163 @kindex info program
3165 Display information about the status of your program: whether it is
3166 running or not, what process it is, and why it stopped.
3170 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3171 * Continuing and Stepping:: Resuming execution
3173 * Thread Stops:: Stopping and starting multi-thread programs
3177 @section Breakpoints, Watchpoints, and Catchpoints
3180 A @dfn{breakpoint} makes your program stop whenever a certain point in
3181 the program is reached. For each breakpoint, you can add conditions to
3182 control in finer detail whether your program stops. You can set
3183 breakpoints with the @code{break} command and its variants (@pxref{Set
3184 Breaks, ,Setting Breakpoints}), to specify the place where your program
3185 should stop by line number, function name or exact address in the
3188 On some systems, you can set breakpoints in shared libraries before
3189 the executable is run. There is a minor limitation on HP-UX systems:
3190 you must wait until the executable is run in order to set breakpoints
3191 in shared library routines that are not called directly by the program
3192 (for example, routines that are arguments in a @code{pthread_create}
3196 @cindex data breakpoints
3197 @cindex memory tracing
3198 @cindex breakpoint on memory address
3199 @cindex breakpoint on variable modification
3200 A @dfn{watchpoint} is a special breakpoint that stops your program
3201 when the value of an expression changes. The expression may be a value
3202 of a variable, or it could involve values of one or more variables
3203 combined by operators, such as @samp{a + b}. This is sometimes called
3204 @dfn{data breakpoints}. You must use a different command to set
3205 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3206 from that, you can manage a watchpoint like any other breakpoint: you
3207 enable, disable, and delete both breakpoints and watchpoints using the
3210 You can arrange to have values from your program displayed automatically
3211 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3215 @cindex breakpoint on events
3216 A @dfn{catchpoint} is another special breakpoint that stops your program
3217 when a certain kind of event occurs, such as the throwing of a C@t{++}
3218 exception or the loading of a library. As with watchpoints, you use a
3219 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3220 Catchpoints}), but aside from that, you can manage a catchpoint like any
3221 other breakpoint. (To stop when your program receives a signal, use the
3222 @code{handle} command; see @ref{Signals, ,Signals}.)
3224 @cindex breakpoint numbers
3225 @cindex numbers for breakpoints
3226 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3227 catchpoint when you create it; these numbers are successive integers
3228 starting with one. In many of the commands for controlling various
3229 features of breakpoints you use the breakpoint number to say which
3230 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3231 @dfn{disabled}; if disabled, it has no effect on your program until you
3234 @cindex breakpoint ranges
3235 @cindex ranges of breakpoints
3236 Some @value{GDBN} commands accept a range of breakpoints on which to
3237 operate. A breakpoint range is either a single breakpoint number, like
3238 @samp{5}, or two such numbers, in increasing order, separated by a
3239 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3240 all breakpoints in that range are operated on.
3243 * Set Breaks:: Setting breakpoints
3244 * Set Watchpoints:: Setting watchpoints
3245 * Set Catchpoints:: Setting catchpoints
3246 * Delete Breaks:: Deleting breakpoints
3247 * Disabling:: Disabling breakpoints
3248 * Conditions:: Break conditions
3249 * Break Commands:: Breakpoint command lists
3250 * Save Breakpoints:: How to save breakpoints in a file
3251 * Error in Breakpoints:: ``Cannot insert breakpoints''
3252 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3256 @subsection Setting Breakpoints
3258 @c FIXME LMB what does GDB do if no code on line of breakpt?
3259 @c consider in particular declaration with/without initialization.
3261 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3264 @kindex b @r{(@code{break})}
3265 @vindex $bpnum@r{, convenience variable}
3266 @cindex latest breakpoint
3267 Breakpoints are set with the @code{break} command (abbreviated
3268 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3269 number of the breakpoint you've set most recently; see @ref{Convenience
3270 Vars,, Convenience Variables}, for a discussion of what you can do with
3271 convenience variables.
3274 @item break @var{location}
3275 Set a breakpoint at the given @var{location}, which can specify a
3276 function name, a line number, or an address of an instruction.
3277 (@xref{Specify Location}, for a list of all the possible ways to
3278 specify a @var{location}.) The breakpoint will stop your program just
3279 before it executes any of the code in the specified @var{location}.
3281 When using source languages that permit overloading of symbols, such as
3282 C@t{++}, a function name may refer to more than one possible place to break.
3283 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3286 It is also possible to insert a breakpoint that will stop the program
3287 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3288 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3291 When called without any arguments, @code{break} sets a breakpoint at
3292 the next instruction to be executed in the selected stack frame
3293 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3294 innermost, this makes your program stop as soon as control
3295 returns to that frame. This is similar to the effect of a
3296 @code{finish} command in the frame inside the selected frame---except
3297 that @code{finish} does not leave an active breakpoint. If you use
3298 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3299 the next time it reaches the current location; this may be useful
3302 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3303 least one instruction has been executed. If it did not do this, you
3304 would be unable to proceed past a breakpoint without first disabling the
3305 breakpoint. This rule applies whether or not the breakpoint already
3306 existed when your program stopped.
3308 @item break @dots{} if @var{cond}
3309 Set a breakpoint with condition @var{cond}; evaluate the expression
3310 @var{cond} each time the breakpoint is reached, and stop only if the
3311 value is nonzero---that is, if @var{cond} evaluates as true.
3312 @samp{@dots{}} stands for one of the possible arguments described
3313 above (or no argument) specifying where to break. @xref{Conditions,
3314 ,Break Conditions}, for more information on breakpoint conditions.
3317 @item tbreak @var{args}
3318 Set a breakpoint enabled only for one stop. @var{args} are the
3319 same as for the @code{break} command, and the breakpoint is set in the same
3320 way, but the breakpoint is automatically deleted after the first time your
3321 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3324 @cindex hardware breakpoints
3325 @item hbreak @var{args}
3326 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3327 @code{break} command and the breakpoint is set in the same way, but the
3328 breakpoint requires hardware support and some target hardware may not
3329 have this support. The main purpose of this is EPROM/ROM code
3330 debugging, so you can set a breakpoint at an instruction without
3331 changing the instruction. This can be used with the new trap-generation
3332 provided by SPARClite DSU and most x86-based targets. These targets
3333 will generate traps when a program accesses some data or instruction
3334 address that is assigned to the debug registers. However the hardware
3335 breakpoint registers can take a limited number of breakpoints. For
3336 example, on the DSU, only two data breakpoints can be set at a time, and
3337 @value{GDBN} will reject this command if more than two are used. Delete
3338 or disable unused hardware breakpoints before setting new ones
3339 (@pxref{Disabling, ,Disabling Breakpoints}).
3340 @xref{Conditions, ,Break Conditions}.
3341 For remote targets, you can restrict the number of hardware
3342 breakpoints @value{GDBN} will use, see @ref{set remote
3343 hardware-breakpoint-limit}.
3346 @item thbreak @var{args}
3347 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3348 are the same as for the @code{hbreak} command and the breakpoint is set in
3349 the same way. However, like the @code{tbreak} command,
3350 the breakpoint is automatically deleted after the
3351 first time your program stops there. Also, like the @code{hbreak}
3352 command, the breakpoint requires hardware support and some target hardware
3353 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3354 See also @ref{Conditions, ,Break Conditions}.
3357 @cindex regular expression
3358 @cindex breakpoints at functions matching a regexp
3359 @cindex set breakpoints in many functions
3360 @item rbreak @var{regex}
3361 Set breakpoints on all functions matching the regular expression
3362 @var{regex}. This command sets an unconditional breakpoint on all
3363 matches, printing a list of all breakpoints it set. Once these
3364 breakpoints are set, they are treated just like the breakpoints set with
3365 the @code{break} command. You can delete them, disable them, or make
3366 them conditional the same way as any other breakpoint.
3368 The syntax of the regular expression is the standard one used with tools
3369 like @file{grep}. Note that this is different from the syntax used by
3370 shells, so for instance @code{foo*} matches all functions that include
3371 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3372 @code{.*} leading and trailing the regular expression you supply, so to
3373 match only functions that begin with @code{foo}, use @code{^foo}.
3375 @cindex non-member C@t{++} functions, set breakpoint in
3376 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3377 breakpoints on overloaded functions that are not members of any special
3380 @cindex set breakpoints on all functions
3381 The @code{rbreak} command can be used to set breakpoints in
3382 @strong{all} the functions in a program, like this:
3385 (@value{GDBP}) rbreak .
3388 @item rbreak @var{file}:@var{regex}
3389 If @code{rbreak} is called with a filename qualification, it limits
3390 the search for functions matching the given regular expression to the
3391 specified @var{file}. This can be used, for example, to set breakpoints on
3392 every function in a given file:
3395 (@value{GDBP}) rbreak file.c:.
3398 The colon separating the filename qualifier from the regex may
3399 optionally be surrounded by spaces.
3401 @kindex info breakpoints
3402 @cindex @code{$_} and @code{info breakpoints}
3403 @item info breakpoints @r{[}@var{n}@r{]}
3404 @itemx info break @r{[}@var{n}@r{]}
3405 Print a table of all breakpoints, watchpoints, and catchpoints set and
3406 not deleted. Optional argument @var{n} means print information only
3407 about the specified breakpoint (or watchpoint or catchpoint). For
3408 each breakpoint, following columns are printed:
3411 @item Breakpoint Numbers
3413 Breakpoint, watchpoint, or catchpoint.
3415 Whether the breakpoint is marked to be disabled or deleted when hit.
3416 @item Enabled or Disabled
3417 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3418 that are not enabled.
3420 Where the breakpoint is in your program, as a memory address. For a
3421 pending breakpoint whose address is not yet known, this field will
3422 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3423 library that has the symbol or line referred by breakpoint is loaded.
3424 See below for details. A breakpoint with several locations will
3425 have @samp{<MULTIPLE>} in this field---see below for details.
3427 Where the breakpoint is in the source for your program, as a file and
3428 line number. For a pending breakpoint, the original string passed to
3429 the breakpoint command will be listed as it cannot be resolved until
3430 the appropriate shared library is loaded in the future.
3434 If a breakpoint is conditional, @code{info break} shows the condition on
3435 the line following the affected breakpoint; breakpoint commands, if any,
3436 are listed after that. A pending breakpoint is allowed to have a condition
3437 specified for it. The condition is not parsed for validity until a shared
3438 library is loaded that allows the pending breakpoint to resolve to a
3442 @code{info break} with a breakpoint
3443 number @var{n} as argument lists only that breakpoint. The
3444 convenience variable @code{$_} and the default examining-address for
3445 the @code{x} command are set to the address of the last breakpoint
3446 listed (@pxref{Memory, ,Examining Memory}).
3449 @code{info break} displays a count of the number of times the breakpoint
3450 has been hit. This is especially useful in conjunction with the
3451 @code{ignore} command. You can ignore a large number of breakpoint
3452 hits, look at the breakpoint info to see how many times the breakpoint
3453 was hit, and then run again, ignoring one less than that number. This
3454 will get you quickly to the last hit of that breakpoint.
3457 @value{GDBN} allows you to set any number of breakpoints at the same place in
3458 your program. There is nothing silly or meaningless about this. When
3459 the breakpoints are conditional, this is even useful
3460 (@pxref{Conditions, ,Break Conditions}).
3462 @cindex multiple locations, breakpoints
3463 @cindex breakpoints, multiple locations
3464 It is possible that a breakpoint corresponds to several locations
3465 in your program. Examples of this situation are:
3469 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3470 instances of the function body, used in different cases.
3473 For a C@t{++} template function, a given line in the function can
3474 correspond to any number of instantiations.
3477 For an inlined function, a given source line can correspond to
3478 several places where that function is inlined.
3481 In all those cases, @value{GDBN} will insert a breakpoint at all
3482 the relevant locations@footnote{
3483 As of this writing, multiple-location breakpoints work only if there's
3484 line number information for all the locations. This means that they
3485 will generally not work in system libraries, unless you have debug
3486 info with line numbers for them.}.
3488 A breakpoint with multiple locations is displayed in the breakpoint
3489 table using several rows---one header row, followed by one row for
3490 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3491 address column. The rows for individual locations contain the actual
3492 addresses for locations, and show the functions to which those
3493 locations belong. The number column for a location is of the form
3494 @var{breakpoint-number}.@var{location-number}.
3499 Num Type Disp Enb Address What
3500 1 breakpoint keep y <MULTIPLE>
3502 breakpoint already hit 1 time
3503 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3504 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3507 Each location can be individually enabled or disabled by passing
3508 @var{breakpoint-number}.@var{location-number} as argument to the
3509 @code{enable} and @code{disable} commands. Note that you cannot
3510 delete the individual locations from the list, you can only delete the
3511 entire list of locations that belong to their parent breakpoint (with
3512 the @kbd{delete @var{num}} command, where @var{num} is the number of
3513 the parent breakpoint, 1 in the above example). Disabling or enabling
3514 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3515 that belong to that breakpoint.
3517 @cindex pending breakpoints
3518 It's quite common to have a breakpoint inside a shared library.
3519 Shared libraries can be loaded and unloaded explicitly,
3520 and possibly repeatedly, as the program is executed. To support
3521 this use case, @value{GDBN} updates breakpoint locations whenever
3522 any shared library is loaded or unloaded. Typically, you would
3523 set a breakpoint in a shared library at the beginning of your
3524 debugging session, when the library is not loaded, and when the
3525 symbols from the library are not available. When you try to set
3526 breakpoint, @value{GDBN} will ask you if you want to set
3527 a so called @dfn{pending breakpoint}---breakpoint whose address
3528 is not yet resolved.
3530 After the program is run, whenever a new shared library is loaded,
3531 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3532 shared library contains the symbol or line referred to by some
3533 pending breakpoint, that breakpoint is resolved and becomes an
3534 ordinary breakpoint. When a library is unloaded, all breakpoints
3535 that refer to its symbols or source lines become pending again.
3537 This logic works for breakpoints with multiple locations, too. For
3538 example, if you have a breakpoint in a C@t{++} template function, and
3539 a newly loaded shared library has an instantiation of that template,
3540 a new location is added to the list of locations for the breakpoint.
3542 Except for having unresolved address, pending breakpoints do not
3543 differ from regular breakpoints. You can set conditions or commands,
3544 enable and disable them and perform other breakpoint operations.
3546 @value{GDBN} provides some additional commands for controlling what
3547 happens when the @samp{break} command cannot resolve breakpoint
3548 address specification to an address:
3550 @kindex set breakpoint pending
3551 @kindex show breakpoint pending
3553 @item set breakpoint pending auto
3554 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3555 location, it queries you whether a pending breakpoint should be created.
3557 @item set breakpoint pending on
3558 This indicates that an unrecognized breakpoint location should automatically
3559 result in a pending breakpoint being created.
3561 @item set breakpoint pending off
3562 This indicates that pending breakpoints are not to be created. Any
3563 unrecognized breakpoint location results in an error. This setting does
3564 not affect any pending breakpoints previously created.
3566 @item show breakpoint pending
3567 Show the current behavior setting for creating pending breakpoints.
3570 The settings above only affect the @code{break} command and its
3571 variants. Once breakpoint is set, it will be automatically updated
3572 as shared libraries are loaded and unloaded.
3574 @cindex automatic hardware breakpoints
3575 For some targets, @value{GDBN} can automatically decide if hardware or
3576 software breakpoints should be used, depending on whether the
3577 breakpoint address is read-only or read-write. This applies to
3578 breakpoints set with the @code{break} command as well as to internal
3579 breakpoints set by commands like @code{next} and @code{finish}. For
3580 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3583 You can control this automatic behaviour with the following commands::
3585 @kindex set breakpoint auto-hw
3586 @kindex show breakpoint auto-hw
3588 @item set breakpoint auto-hw on
3589 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3590 will try to use the target memory map to decide if software or hardware
3591 breakpoint must be used.
3593 @item set breakpoint auto-hw off
3594 This indicates @value{GDBN} should not automatically select breakpoint
3595 type. If the target provides a memory map, @value{GDBN} will warn when
3596 trying to set software breakpoint at a read-only address.
3599 @value{GDBN} normally implements breakpoints by replacing the program code
3600 at the breakpoint address with a special instruction, which, when
3601 executed, given control to the debugger. By default, the program
3602 code is so modified only when the program is resumed. As soon as
3603 the program stops, @value{GDBN} restores the original instructions. This
3604 behaviour guards against leaving breakpoints inserted in the
3605 target should gdb abrubptly disconnect. However, with slow remote
3606 targets, inserting and removing breakpoint can reduce the performance.
3607 This behavior can be controlled with the following commands::
3609 @kindex set breakpoint always-inserted
3610 @kindex show breakpoint always-inserted
3612 @item set breakpoint always-inserted off
3613 All breakpoints, including newly added by the user, are inserted in
3614 the target only when the target is resumed. All breakpoints are
3615 removed from the target when it stops.
3617 @item set breakpoint always-inserted on
3618 Causes all breakpoints to be inserted in the target at all times. If
3619 the user adds a new breakpoint, or changes an existing breakpoint, the
3620 breakpoints in the target are updated immediately. A breakpoint is
3621 removed from the target only when breakpoint itself is removed.
3623 @cindex non-stop mode, and @code{breakpoint always-inserted}
3624 @item set breakpoint always-inserted auto
3625 This is the default mode. If @value{GDBN} is controlling the inferior
3626 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3627 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3628 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3629 @code{breakpoint always-inserted} mode is off.
3632 @cindex negative breakpoint numbers
3633 @cindex internal @value{GDBN} breakpoints
3634 @value{GDBN} itself sometimes sets breakpoints in your program for
3635 special purposes, such as proper handling of @code{longjmp} (in C
3636 programs). These internal breakpoints are assigned negative numbers,
3637 starting with @code{-1}; @samp{info breakpoints} does not display them.
3638 You can see these breakpoints with the @value{GDBN} maintenance command
3639 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3642 @node Set Watchpoints
3643 @subsection Setting Watchpoints
3645 @cindex setting watchpoints
3646 You can use a watchpoint to stop execution whenever the value of an
3647 expression changes, without having to predict a particular place where
3648 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3649 The expression may be as simple as the value of a single variable, or
3650 as complex as many variables combined by operators. Examples include:
3654 A reference to the value of a single variable.
3657 An address cast to an appropriate data type. For example,
3658 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3659 address (assuming an @code{int} occupies 4 bytes).
3662 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3663 expression can use any operators valid in the program's native
3664 language (@pxref{Languages}).
3667 You can set a watchpoint on an expression even if the expression can
3668 not be evaluated yet. For instance, you can set a watchpoint on
3669 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3670 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3671 the expression produces a valid value. If the expression becomes
3672 valid in some other way than changing a variable (e.g.@: if the memory
3673 pointed to by @samp{*global_ptr} becomes readable as the result of a
3674 @code{malloc} call), @value{GDBN} may not stop until the next time
3675 the expression changes.
3677 @cindex software watchpoints
3678 @cindex hardware watchpoints
3679 Depending on your system, watchpoints may be implemented in software or
3680 hardware. @value{GDBN} does software watchpointing by single-stepping your
3681 program and testing the variable's value each time, which is hundreds of
3682 times slower than normal execution. (But this may still be worth it, to
3683 catch errors where you have no clue what part of your program is the
3686 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3687 x86-based targets, @value{GDBN} includes support for hardware
3688 watchpoints, which do not slow down the running of your program.
3692 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3693 Set a watchpoint for an expression. @value{GDBN} will break when the
3694 expression @var{expr} is written into by the program and its value
3695 changes. The simplest (and the most popular) use of this command is
3696 to watch the value of a single variable:
3699 (@value{GDBP}) watch foo
3702 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3703 clause, @value{GDBN} breaks only when the thread identified by
3704 @var{threadnum} changes the value of @var{expr}. If any other threads
3705 change the value of @var{expr}, @value{GDBN} will not break. Note
3706 that watchpoints restricted to a single thread in this way only work
3707 with Hardware Watchpoints.
3710 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3711 Set a watchpoint that will break when the value of @var{expr} is read
3715 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3716 Set a watchpoint that will break when @var{expr} is either read from
3717 or written into by the program.
3719 @kindex info watchpoints @r{[}@var{n}@r{]}
3720 @item info watchpoints
3721 This command prints a list of watchpoints, using the same format as
3722 @code{info break} (@pxref{Set Breaks}).
3725 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3726 watchpoints execute very quickly, and the debugger reports a change in
3727 value at the exact instruction where the change occurs. If @value{GDBN}
3728 cannot set a hardware watchpoint, it sets a software watchpoint, which
3729 executes more slowly and reports the change in value at the next
3730 @emph{statement}, not the instruction, after the change occurs.
3732 @cindex use only software watchpoints
3733 You can force @value{GDBN} to use only software watchpoints with the
3734 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3735 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3736 the underlying system supports them. (Note that hardware-assisted
3737 watchpoints that were set @emph{before} setting
3738 @code{can-use-hw-watchpoints} to zero will still use the hardware
3739 mechanism of watching expression values.)
3742 @item set can-use-hw-watchpoints
3743 @kindex set can-use-hw-watchpoints
3744 Set whether or not to use hardware watchpoints.
3746 @item show can-use-hw-watchpoints
3747 @kindex show can-use-hw-watchpoints
3748 Show the current mode of using hardware watchpoints.
3751 For remote targets, you can restrict the number of hardware
3752 watchpoints @value{GDBN} will use, see @ref{set remote
3753 hardware-breakpoint-limit}.
3755 When you issue the @code{watch} command, @value{GDBN} reports
3758 Hardware watchpoint @var{num}: @var{expr}
3762 if it was able to set a hardware watchpoint.
3764 Currently, the @code{awatch} and @code{rwatch} commands can only set
3765 hardware watchpoints, because accesses to data that don't change the
3766 value of the watched expression cannot be detected without examining
3767 every instruction as it is being executed, and @value{GDBN} does not do
3768 that currently. If @value{GDBN} finds that it is unable to set a
3769 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3770 will print a message like this:
3773 Expression cannot be implemented with read/access watchpoint.
3776 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3777 data type of the watched expression is wider than what a hardware
3778 watchpoint on the target machine can handle. For example, some systems
3779 can only watch regions that are up to 4 bytes wide; on such systems you
3780 cannot set hardware watchpoints for an expression that yields a
3781 double-precision floating-point number (which is typically 8 bytes
3782 wide). As a work-around, it might be possible to break the large region
3783 into a series of smaller ones and watch them with separate watchpoints.
3785 If you set too many hardware watchpoints, @value{GDBN} might be unable
3786 to insert all of them when you resume the execution of your program.
3787 Since the precise number of active watchpoints is unknown until such
3788 time as the program is about to be resumed, @value{GDBN} might not be
3789 able to warn you about this when you set the watchpoints, and the
3790 warning will be printed only when the program is resumed:
3793 Hardware watchpoint @var{num}: Could not insert watchpoint
3797 If this happens, delete or disable some of the watchpoints.
3799 Watching complex expressions that reference many variables can also
3800 exhaust the resources available for hardware-assisted watchpoints.
3801 That's because @value{GDBN} needs to watch every variable in the
3802 expression with separately allocated resources.
3804 If you call a function interactively using @code{print} or @code{call},
3805 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3806 kind of breakpoint or the call completes.
3808 @value{GDBN} automatically deletes watchpoints that watch local
3809 (automatic) variables, or expressions that involve such variables, when
3810 they go out of scope, that is, when the execution leaves the block in
3811 which these variables were defined. In particular, when the program
3812 being debugged terminates, @emph{all} local variables go out of scope,
3813 and so only watchpoints that watch global variables remain set. If you
3814 rerun the program, you will need to set all such watchpoints again. One
3815 way of doing that would be to set a code breakpoint at the entry to the
3816 @code{main} function and when it breaks, set all the watchpoints.
3818 @cindex watchpoints and threads
3819 @cindex threads and watchpoints
3820 In multi-threaded programs, watchpoints will detect changes to the
3821 watched expression from every thread.
3824 @emph{Warning:} In multi-threaded programs, software watchpoints
3825 have only limited usefulness. If @value{GDBN} creates a software
3826 watchpoint, it can only watch the value of an expression @emph{in a
3827 single thread}. If you are confident that the expression can only
3828 change due to the current thread's activity (and if you are also
3829 confident that no other thread can become current), then you can use
3830 software watchpoints as usual. However, @value{GDBN} may not notice
3831 when a non-current thread's activity changes the expression. (Hardware
3832 watchpoints, in contrast, watch an expression in all threads.)
3835 @xref{set remote hardware-watchpoint-limit}.
3837 @node Set Catchpoints
3838 @subsection Setting Catchpoints
3839 @cindex catchpoints, setting
3840 @cindex exception handlers
3841 @cindex event handling
3843 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3844 kinds of program events, such as C@t{++} exceptions or the loading of a
3845 shared library. Use the @code{catch} command to set a catchpoint.
3849 @item catch @var{event}
3850 Stop when @var{event} occurs. @var{event} can be any of the following:
3853 @cindex stop on C@t{++} exceptions
3854 The throwing of a C@t{++} exception.
3857 The catching of a C@t{++} exception.
3860 @cindex Ada exception catching
3861 @cindex catch Ada exceptions
3862 An Ada exception being raised. If an exception name is specified
3863 at the end of the command (eg @code{catch exception Program_Error}),
3864 the debugger will stop only when this specific exception is raised.
3865 Otherwise, the debugger stops execution when any Ada exception is raised.
3867 When inserting an exception catchpoint on a user-defined exception whose
3868 name is identical to one of the exceptions defined by the language, the
3869 fully qualified name must be used as the exception name. Otherwise,
3870 @value{GDBN} will assume that it should stop on the pre-defined exception
3871 rather than the user-defined one. For instance, assuming an exception
3872 called @code{Constraint_Error} is defined in package @code{Pck}, then
3873 the command to use to catch such exceptions is @kbd{catch exception
3874 Pck.Constraint_Error}.
3876 @item exception unhandled
3877 An exception that was raised but is not handled by the program.
3880 A failed Ada assertion.
3883 @cindex break on fork/exec
3884 A call to @code{exec}. This is currently only available for HP-UX
3888 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3889 @cindex break on a system call.
3890 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3891 syscall is a mechanism for application programs to request a service
3892 from the operating system (OS) or one of the OS system services.
3893 @value{GDBN} can catch some or all of the syscalls issued by the
3894 debuggee, and show the related information for each syscall. If no
3895 argument is specified, calls to and returns from all system calls
3898 @var{name} can be any system call name that is valid for the
3899 underlying OS. Just what syscalls are valid depends on the OS. On
3900 GNU and Unix systems, you can find the full list of valid syscall
3901 names on @file{/usr/include/asm/unistd.h}.
3903 @c For MS-Windows, the syscall names and the corresponding numbers
3904 @c can be found, e.g., on this URL:
3905 @c http://www.metasploit.com/users/opcode/syscalls.html
3906 @c but we don't support Windows syscalls yet.
3908 Normally, @value{GDBN} knows in advance which syscalls are valid for
3909 each OS, so you can use the @value{GDBN} command-line completion
3910 facilities (@pxref{Completion,, command completion}) to list the
3913 You may also specify the system call numerically. A syscall's
3914 number is the value passed to the OS's syscall dispatcher to
3915 identify the requested service. When you specify the syscall by its
3916 name, @value{GDBN} uses its database of syscalls to convert the name
3917 into the corresponding numeric code, but using the number directly
3918 may be useful if @value{GDBN}'s database does not have the complete
3919 list of syscalls on your system (e.g., because @value{GDBN} lags
3920 behind the OS upgrades).
3922 The example below illustrates how this command works if you don't provide
3926 (@value{GDBP}) catch syscall
3927 Catchpoint 1 (syscall)
3929 Starting program: /tmp/catch-syscall
3931 Catchpoint 1 (call to syscall 'close'), \
3932 0xffffe424 in __kernel_vsyscall ()
3936 Catchpoint 1 (returned from syscall 'close'), \
3937 0xffffe424 in __kernel_vsyscall ()
3941 Here is an example of catching a system call by name:
3944 (@value{GDBP}) catch syscall chroot
3945 Catchpoint 1 (syscall 'chroot' [61])
3947 Starting program: /tmp/catch-syscall
3949 Catchpoint 1 (call to syscall 'chroot'), \
3950 0xffffe424 in __kernel_vsyscall ()
3954 Catchpoint 1 (returned from syscall 'chroot'), \
3955 0xffffe424 in __kernel_vsyscall ()
3959 An example of specifying a system call numerically. In the case
3960 below, the syscall number has a corresponding entry in the XML
3961 file, so @value{GDBN} finds its name and prints it:
3964 (@value{GDBP}) catch syscall 252
3965 Catchpoint 1 (syscall(s) 'exit_group')
3967 Starting program: /tmp/catch-syscall
3969 Catchpoint 1 (call to syscall 'exit_group'), \
3970 0xffffe424 in __kernel_vsyscall ()
3974 Program exited normally.
3978 However, there can be situations when there is no corresponding name
3979 in XML file for that syscall number. In this case, @value{GDBN} prints
3980 a warning message saying that it was not able to find the syscall name,
3981 but the catchpoint will be set anyway. See the example below:
3984 (@value{GDBP}) catch syscall 764
3985 warning: The number '764' does not represent a known syscall.
3986 Catchpoint 2 (syscall 764)
3990 If you configure @value{GDBN} using the @samp{--without-expat} option,
3991 it will not be able to display syscall names. Also, if your
3992 architecture does not have an XML file describing its system calls,
3993 you will not be able to see the syscall names. It is important to
3994 notice that these two features are used for accessing the syscall
3995 name database. In either case, you will see a warning like this:
3998 (@value{GDBP}) catch syscall
3999 warning: Could not open "syscalls/i386-linux.xml"
4000 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4001 GDB will not be able to display syscall names.
4002 Catchpoint 1 (syscall)
4006 Of course, the file name will change depending on your architecture and system.
4008 Still using the example above, you can also try to catch a syscall by its
4009 number. In this case, you would see something like:
4012 (@value{GDBP}) catch syscall 252
4013 Catchpoint 1 (syscall(s) 252)
4016 Again, in this case @value{GDBN} would not be able to display syscall's names.
4019 A call to @code{fork}. This is currently only available for HP-UX
4023 A call to @code{vfork}. This is currently only available for HP-UX
4028 @item tcatch @var{event}
4029 Set a catchpoint that is enabled only for one stop. The catchpoint is
4030 automatically deleted after the first time the event is caught.
4034 Use the @code{info break} command to list the current catchpoints.
4036 There are currently some limitations to C@t{++} exception handling
4037 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4041 If you call a function interactively, @value{GDBN} normally returns
4042 control to you when the function has finished executing. If the call
4043 raises an exception, however, the call may bypass the mechanism that
4044 returns control to you and cause your program either to abort or to
4045 simply continue running until it hits a breakpoint, catches a signal
4046 that @value{GDBN} is listening for, or exits. This is the case even if
4047 you set a catchpoint for the exception; catchpoints on exceptions are
4048 disabled within interactive calls.
4051 You cannot raise an exception interactively.
4054 You cannot install an exception handler interactively.
4057 @cindex raise exceptions
4058 Sometimes @code{catch} is not the best way to debug exception handling:
4059 if you need to know exactly where an exception is raised, it is better to
4060 stop @emph{before} the exception handler is called, since that way you
4061 can see the stack before any unwinding takes place. If you set a
4062 breakpoint in an exception handler instead, it may not be easy to find
4063 out where the exception was raised.
4065 To stop just before an exception handler is called, you need some
4066 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4067 raised by calling a library function named @code{__raise_exception}
4068 which has the following ANSI C interface:
4071 /* @var{addr} is where the exception identifier is stored.
4072 @var{id} is the exception identifier. */
4073 void __raise_exception (void **addr, void *id);
4077 To make the debugger catch all exceptions before any stack
4078 unwinding takes place, set a breakpoint on @code{__raise_exception}
4079 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4081 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4082 that depends on the value of @var{id}, you can stop your program when
4083 a specific exception is raised. You can use multiple conditional
4084 breakpoints to stop your program when any of a number of exceptions are
4089 @subsection Deleting Breakpoints
4091 @cindex clearing breakpoints, watchpoints, catchpoints
4092 @cindex deleting breakpoints, watchpoints, catchpoints
4093 It is often necessary to eliminate a breakpoint, watchpoint, or
4094 catchpoint once it has done its job and you no longer want your program
4095 to stop there. This is called @dfn{deleting} the breakpoint. A
4096 breakpoint that has been deleted no longer exists; it is forgotten.
4098 With the @code{clear} command you can delete breakpoints according to
4099 where they are in your program. With the @code{delete} command you can
4100 delete individual breakpoints, watchpoints, or catchpoints by specifying
4101 their breakpoint numbers.
4103 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4104 automatically ignores breakpoints on the first instruction to be executed
4105 when you continue execution without changing the execution address.
4110 Delete any breakpoints at the next instruction to be executed in the
4111 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4112 the innermost frame is selected, this is a good way to delete a
4113 breakpoint where your program just stopped.
4115 @item clear @var{location}
4116 Delete any breakpoints set at the specified @var{location}.
4117 @xref{Specify Location}, for the various forms of @var{location}; the
4118 most useful ones are listed below:
4121 @item clear @var{function}
4122 @itemx clear @var{filename}:@var{function}
4123 Delete any breakpoints set at entry to the named @var{function}.
4125 @item clear @var{linenum}
4126 @itemx clear @var{filename}:@var{linenum}
4127 Delete any breakpoints set at or within the code of the specified
4128 @var{linenum} of the specified @var{filename}.
4131 @cindex delete breakpoints
4133 @kindex d @r{(@code{delete})}
4134 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4135 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4136 ranges specified as arguments. If no argument is specified, delete all
4137 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4138 confirm off}). You can abbreviate this command as @code{d}.
4142 @subsection Disabling Breakpoints
4144 @cindex enable/disable a breakpoint
4145 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4146 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4147 it had been deleted, but remembers the information on the breakpoint so
4148 that you can @dfn{enable} it again later.
4150 You disable and enable breakpoints, watchpoints, and catchpoints with
4151 the @code{enable} and @code{disable} commands, optionally specifying
4152 one or more breakpoint numbers as arguments. Use @code{info break} to
4153 print a list of all breakpoints, watchpoints, and catchpoints if you
4154 do not know which numbers to use.
4156 Disabling and enabling a breakpoint that has multiple locations
4157 affects all of its locations.
4159 A breakpoint, watchpoint, or catchpoint can have any of four different
4160 states of enablement:
4164 Enabled. The breakpoint stops your program. A breakpoint set
4165 with the @code{break} command starts out in this state.
4167 Disabled. The breakpoint has no effect on your program.
4169 Enabled once. The breakpoint stops your program, but then becomes
4172 Enabled for deletion. The breakpoint stops your program, but
4173 immediately after it does so it is deleted permanently. A breakpoint
4174 set with the @code{tbreak} command starts out in this state.
4177 You can use the following commands to enable or disable breakpoints,
4178 watchpoints, and catchpoints:
4182 @kindex dis @r{(@code{disable})}
4183 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4184 Disable the specified breakpoints---or all breakpoints, if none are
4185 listed. A disabled breakpoint has no effect but is not forgotten. All
4186 options such as ignore-counts, conditions and commands are remembered in
4187 case the breakpoint is enabled again later. You may abbreviate
4188 @code{disable} as @code{dis}.
4191 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4192 Enable the specified breakpoints (or all defined breakpoints). They
4193 become effective once again in stopping your program.
4195 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4196 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4197 of these breakpoints immediately after stopping your program.
4199 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4200 Enable the specified breakpoints to work once, then die. @value{GDBN}
4201 deletes any of these breakpoints as soon as your program stops there.
4202 Breakpoints set by the @code{tbreak} command start out in this state.
4205 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4206 @c confusing: tbreak is also initially enabled.
4207 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4208 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4209 subsequently, they become disabled or enabled only when you use one of
4210 the commands above. (The command @code{until} can set and delete a
4211 breakpoint of its own, but it does not change the state of your other
4212 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4216 @subsection Break Conditions
4217 @cindex conditional breakpoints
4218 @cindex breakpoint conditions
4220 @c FIXME what is scope of break condition expr? Context where wanted?
4221 @c in particular for a watchpoint?
4222 The simplest sort of breakpoint breaks every time your program reaches a
4223 specified place. You can also specify a @dfn{condition} for a
4224 breakpoint. A condition is just a Boolean expression in your
4225 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4226 a condition evaluates the expression each time your program reaches it,
4227 and your program stops only if the condition is @emph{true}.
4229 This is the converse of using assertions for program validation; in that
4230 situation, you want to stop when the assertion is violated---that is,
4231 when the condition is false. In C, if you want to test an assertion expressed
4232 by the condition @var{assert}, you should set the condition
4233 @samp{! @var{assert}} on the appropriate breakpoint.
4235 Conditions are also accepted for watchpoints; you may not need them,
4236 since a watchpoint is inspecting the value of an expression anyhow---but
4237 it might be simpler, say, to just set a watchpoint on a variable name,
4238 and specify a condition that tests whether the new value is an interesting
4241 Break conditions can have side effects, and may even call functions in
4242 your program. This can be useful, for example, to activate functions
4243 that log program progress, or to use your own print functions to
4244 format special data structures. The effects are completely predictable
4245 unless there is another enabled breakpoint at the same address. (In
4246 that case, @value{GDBN} might see the other breakpoint first and stop your
4247 program without checking the condition of this one.) Note that
4248 breakpoint commands are usually more convenient and flexible than break
4250 purpose of performing side effects when a breakpoint is reached
4251 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4253 Break conditions can be specified when a breakpoint is set, by using
4254 @samp{if} in the arguments to the @code{break} command. @xref{Set
4255 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4256 with the @code{condition} command.
4258 You can also use the @code{if} keyword with the @code{watch} command.
4259 The @code{catch} command does not recognize the @code{if} keyword;
4260 @code{condition} is the only way to impose a further condition on a
4265 @item condition @var{bnum} @var{expression}
4266 Specify @var{expression} as the break condition for breakpoint,
4267 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4268 breakpoint @var{bnum} stops your program only if the value of
4269 @var{expression} is true (nonzero, in C). When you use
4270 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4271 syntactic correctness, and to determine whether symbols in it have
4272 referents in the context of your breakpoint. If @var{expression} uses
4273 symbols not referenced in the context of the breakpoint, @value{GDBN}
4274 prints an error message:
4277 No symbol "foo" in current context.
4282 not actually evaluate @var{expression} at the time the @code{condition}
4283 command (or a command that sets a breakpoint with a condition, like
4284 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4286 @item condition @var{bnum}
4287 Remove the condition from breakpoint number @var{bnum}. It becomes
4288 an ordinary unconditional breakpoint.
4291 @cindex ignore count (of breakpoint)
4292 A special case of a breakpoint condition is to stop only when the
4293 breakpoint has been reached a certain number of times. This is so
4294 useful that there is a special way to do it, using the @dfn{ignore
4295 count} of the breakpoint. Every breakpoint has an ignore count, which
4296 is an integer. Most of the time, the ignore count is zero, and
4297 therefore has no effect. But if your program reaches a breakpoint whose
4298 ignore count is positive, then instead of stopping, it just decrements
4299 the ignore count by one and continues. As a result, if the ignore count
4300 value is @var{n}, the breakpoint does not stop the next @var{n} times
4301 your program reaches it.
4305 @item ignore @var{bnum} @var{count}
4306 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4307 The next @var{count} times the breakpoint is reached, your program's
4308 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4311 To make the breakpoint stop the next time it is reached, specify
4314 When you use @code{continue} to resume execution of your program from a
4315 breakpoint, you can specify an ignore count directly as an argument to
4316 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4317 Stepping,,Continuing and Stepping}.
4319 If a breakpoint has a positive ignore count and a condition, the
4320 condition is not checked. Once the ignore count reaches zero,
4321 @value{GDBN} resumes checking the condition.
4323 You could achieve the effect of the ignore count with a condition such
4324 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4325 is decremented each time. @xref{Convenience Vars, ,Convenience
4329 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4332 @node Break Commands
4333 @subsection Breakpoint Command Lists
4335 @cindex breakpoint commands
4336 You can give any breakpoint (or watchpoint or catchpoint) a series of
4337 commands to execute when your program stops due to that breakpoint. For
4338 example, you might want to print the values of certain expressions, or
4339 enable other breakpoints.
4343 @kindex end@r{ (breakpoint commands)}
4344 @item commands @r{[}@var{range}@dots{}@r{]}
4345 @itemx @dots{} @var{command-list} @dots{}
4347 Specify a list of commands for the given breakpoints. The commands
4348 themselves appear on the following lines. Type a line containing just
4349 @code{end} to terminate the commands.
4351 To remove all commands from a breakpoint, type @code{commands} and
4352 follow it immediately with @code{end}; that is, give no commands.
4354 With no argument, @code{commands} refers to the last breakpoint,
4355 watchpoint, or catchpoint set (not to the breakpoint most recently
4356 encountered). If the most recent breakpoints were set with a single
4357 command, then the @code{commands} will apply to all the breakpoints
4358 set by that command. This applies to breakpoints set by
4359 @code{rbreak}, and also applies when a single @code{break} command
4360 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4364 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4365 disabled within a @var{command-list}.
4367 You can use breakpoint commands to start your program up again. Simply
4368 use the @code{continue} command, or @code{step}, or any other command
4369 that resumes execution.
4371 Any other commands in the command list, after a command that resumes
4372 execution, are ignored. This is because any time you resume execution
4373 (even with a simple @code{next} or @code{step}), you may encounter
4374 another breakpoint---which could have its own command list, leading to
4375 ambiguities about which list to execute.
4378 If the first command you specify in a command list is @code{silent}, the
4379 usual message about stopping at a breakpoint is not printed. This may
4380 be desirable for breakpoints that are to print a specific message and
4381 then continue. If none of the remaining commands print anything, you
4382 see no sign that the breakpoint was reached. @code{silent} is
4383 meaningful only at the beginning of a breakpoint command list.
4385 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4386 print precisely controlled output, and are often useful in silent
4387 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4389 For example, here is how you could use breakpoint commands to print the
4390 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4396 printf "x is %d\n",x
4401 One application for breakpoint commands is to compensate for one bug so
4402 you can test for another. Put a breakpoint just after the erroneous line
4403 of code, give it a condition to detect the case in which something
4404 erroneous has been done, and give it commands to assign correct values
4405 to any variables that need them. End with the @code{continue} command
4406 so that your program does not stop, and start with the @code{silent}
4407 command so that no output is produced. Here is an example:
4418 @node Save Breakpoints
4419 @subsection How to save breakpoints to a file
4421 To save breakpoint definitions to a file use the @w{@code{save
4422 breakpoints}} command.
4425 @kindex save breakpoints
4426 @cindex save breakpoints to a file for future sessions
4427 @item save breakpoints [@var{filename}]
4428 This command saves all current breakpoint definitions together with
4429 their commands and ignore counts, into a file @file{@var{filename}}
4430 suitable for use in a later debugging session. This includes all
4431 types of breakpoints (breakpoints, watchpoints, catchpoints,
4432 tracepoints). To read the saved breakpoint definitions, use the
4433 @code{source} command (@pxref{Command Files}). Note that watchpoints
4434 with expressions involving local variables may fail to be recreated
4435 because it may not be possible to access the context where the
4436 watchpoint is valid anymore. Because the saved breakpoint definitions
4437 are simply a sequence of @value{GDBN} commands that recreate the
4438 breakpoints, you can edit the file in your favorite editing program,
4439 and remove the breakpoint definitions you're not interested in, or
4440 that can no longer be recreated.
4443 @c @ifclear BARETARGET
4444 @node Error in Breakpoints
4445 @subsection ``Cannot insert breakpoints''
4447 If you request too many active hardware-assisted breakpoints and
4448 watchpoints, you will see this error message:
4450 @c FIXME: the precise wording of this message may change; the relevant
4451 @c source change is not committed yet (Sep 3, 1999).
4453 Stopped; cannot insert breakpoints.
4454 You may have requested too many hardware breakpoints and watchpoints.
4458 This message is printed when you attempt to resume the program, since
4459 only then @value{GDBN} knows exactly how many hardware breakpoints and
4460 watchpoints it needs to insert.
4462 When this message is printed, you need to disable or remove some of the
4463 hardware-assisted breakpoints and watchpoints, and then continue.
4465 @node Breakpoint-related Warnings
4466 @subsection ``Breakpoint address adjusted...''
4467 @cindex breakpoint address adjusted
4469 Some processor architectures place constraints on the addresses at
4470 which breakpoints may be placed. For architectures thus constrained,
4471 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4472 with the constraints dictated by the architecture.
4474 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4475 a VLIW architecture in which a number of RISC-like instructions may be
4476 bundled together for parallel execution. The FR-V architecture
4477 constrains the location of a breakpoint instruction within such a
4478 bundle to the instruction with the lowest address. @value{GDBN}
4479 honors this constraint by adjusting a breakpoint's address to the
4480 first in the bundle.
4482 It is not uncommon for optimized code to have bundles which contain
4483 instructions from different source statements, thus it may happen that
4484 a breakpoint's address will be adjusted from one source statement to
4485 another. Since this adjustment may significantly alter @value{GDBN}'s
4486 breakpoint related behavior from what the user expects, a warning is
4487 printed when the breakpoint is first set and also when the breakpoint
4490 A warning like the one below is printed when setting a breakpoint
4491 that's been subject to address adjustment:
4494 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4497 Such warnings are printed both for user settable and @value{GDBN}'s
4498 internal breakpoints. If you see one of these warnings, you should
4499 verify that a breakpoint set at the adjusted address will have the
4500 desired affect. If not, the breakpoint in question may be removed and
4501 other breakpoints may be set which will have the desired behavior.
4502 E.g., it may be sufficient to place the breakpoint at a later
4503 instruction. A conditional breakpoint may also be useful in some
4504 cases to prevent the breakpoint from triggering too often.
4506 @value{GDBN} will also issue a warning when stopping at one of these
4507 adjusted breakpoints:
4510 warning: Breakpoint 1 address previously adjusted from 0x00010414
4514 When this warning is encountered, it may be too late to take remedial
4515 action except in cases where the breakpoint is hit earlier or more
4516 frequently than expected.
4518 @node Continuing and Stepping
4519 @section Continuing and Stepping
4523 @cindex resuming execution
4524 @dfn{Continuing} means resuming program execution until your program
4525 completes normally. In contrast, @dfn{stepping} means executing just
4526 one more ``step'' of your program, where ``step'' may mean either one
4527 line of source code, or one machine instruction (depending on what
4528 particular command you use). Either when continuing or when stepping,
4529 your program may stop even sooner, due to a breakpoint or a signal. (If
4530 it stops due to a signal, you may want to use @code{handle}, or use
4531 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4535 @kindex c @r{(@code{continue})}
4536 @kindex fg @r{(resume foreground execution)}
4537 @item continue @r{[}@var{ignore-count}@r{]}
4538 @itemx c @r{[}@var{ignore-count}@r{]}
4539 @itemx fg @r{[}@var{ignore-count}@r{]}
4540 Resume program execution, at the address where your program last stopped;
4541 any breakpoints set at that address are bypassed. The optional argument
4542 @var{ignore-count} allows you to specify a further number of times to
4543 ignore a breakpoint at this location; its effect is like that of
4544 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4546 The argument @var{ignore-count} is meaningful only when your program
4547 stopped due to a breakpoint. At other times, the argument to
4548 @code{continue} is ignored.
4550 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4551 debugged program is deemed to be the foreground program) are provided
4552 purely for convenience, and have exactly the same behavior as
4556 To resume execution at a different place, you can use @code{return}
4557 (@pxref{Returning, ,Returning from a Function}) to go back to the
4558 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4559 Different Address}) to go to an arbitrary location in your program.
4561 A typical technique for using stepping is to set a breakpoint
4562 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4563 beginning of the function or the section of your program where a problem
4564 is believed to lie, run your program until it stops at that breakpoint,
4565 and then step through the suspect area, examining the variables that are
4566 interesting, until you see the problem happen.
4570 @kindex s @r{(@code{step})}
4572 Continue running your program until control reaches a different source
4573 line, then stop it and return control to @value{GDBN}. This command is
4574 abbreviated @code{s}.
4577 @c "without debugging information" is imprecise; actually "without line
4578 @c numbers in the debugging information". (gcc -g1 has debugging info but
4579 @c not line numbers). But it seems complex to try to make that
4580 @c distinction here.
4581 @emph{Warning:} If you use the @code{step} command while control is
4582 within a function that was compiled without debugging information,
4583 execution proceeds until control reaches a function that does have
4584 debugging information. Likewise, it will not step into a function which
4585 is compiled without debugging information. To step through functions
4586 without debugging information, use the @code{stepi} command, described
4590 The @code{step} command only stops at the first instruction of a source
4591 line. This prevents the multiple stops that could otherwise occur in
4592 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4593 to stop if a function that has debugging information is called within
4594 the line. In other words, @code{step} @emph{steps inside} any functions
4595 called within the line.
4597 Also, the @code{step} command only enters a function if there is line
4598 number information for the function. Otherwise it acts like the
4599 @code{next} command. This avoids problems when using @code{cc -gl}
4600 on MIPS machines. Previously, @code{step} entered subroutines if there
4601 was any debugging information about the routine.
4603 @item step @var{count}
4604 Continue running as in @code{step}, but do so @var{count} times. If a
4605 breakpoint is reached, or a signal not related to stepping occurs before
4606 @var{count} steps, stepping stops right away.
4609 @kindex n @r{(@code{next})}
4610 @item next @r{[}@var{count}@r{]}
4611 Continue to the next source line in the current (innermost) stack frame.
4612 This is similar to @code{step}, but function calls that appear within
4613 the line of code are executed without stopping. Execution stops when
4614 control reaches a different line of code at the original stack level
4615 that was executing when you gave the @code{next} command. This command
4616 is abbreviated @code{n}.
4618 An argument @var{count} is a repeat count, as for @code{step}.
4621 @c FIX ME!! Do we delete this, or is there a way it fits in with
4622 @c the following paragraph? --- Vctoria
4624 @c @code{next} within a function that lacks debugging information acts like
4625 @c @code{step}, but any function calls appearing within the code of the
4626 @c function are executed without stopping.
4628 The @code{next} command only stops at the first instruction of a
4629 source line. This prevents multiple stops that could otherwise occur in
4630 @code{switch} statements, @code{for} loops, etc.
4632 @kindex set step-mode
4634 @cindex functions without line info, and stepping
4635 @cindex stepping into functions with no line info
4636 @itemx set step-mode on
4637 The @code{set step-mode on} command causes the @code{step} command to
4638 stop at the first instruction of a function which contains no debug line
4639 information rather than stepping over it.
4641 This is useful in cases where you may be interested in inspecting the
4642 machine instructions of a function which has no symbolic info and do not
4643 want @value{GDBN} to automatically skip over this function.
4645 @item set step-mode off
4646 Causes the @code{step} command to step over any functions which contains no
4647 debug information. This is the default.
4649 @item show step-mode
4650 Show whether @value{GDBN} will stop in or step over functions without
4651 source line debug information.
4654 @kindex fin @r{(@code{finish})}
4656 Continue running until just after function in the selected stack frame
4657 returns. Print the returned value (if any). This command can be
4658 abbreviated as @code{fin}.
4660 Contrast this with the @code{return} command (@pxref{Returning,
4661 ,Returning from a Function}).
4664 @kindex u @r{(@code{until})}
4665 @cindex run until specified location
4668 Continue running until a source line past the current line, in the
4669 current stack frame, is reached. This command is used to avoid single
4670 stepping through a loop more than once. It is like the @code{next}
4671 command, except that when @code{until} encounters a jump, it
4672 automatically continues execution until the program counter is greater
4673 than the address of the jump.
4675 This means that when you reach the end of a loop after single stepping
4676 though it, @code{until} makes your program continue execution until it
4677 exits the loop. In contrast, a @code{next} command at the end of a loop
4678 simply steps back to the beginning of the loop, which forces you to step
4679 through the next iteration.
4681 @code{until} always stops your program if it attempts to exit the current
4684 @code{until} may produce somewhat counterintuitive results if the order
4685 of machine code does not match the order of the source lines. For
4686 example, in the following excerpt from a debugging session, the @code{f}
4687 (@code{frame}) command shows that execution is stopped at line
4688 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4692 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4694 (@value{GDBP}) until
4695 195 for ( ; argc > 0; NEXTARG) @{
4698 This happened because, for execution efficiency, the compiler had
4699 generated code for the loop closure test at the end, rather than the
4700 start, of the loop---even though the test in a C @code{for}-loop is
4701 written before the body of the loop. The @code{until} command appeared
4702 to step back to the beginning of the loop when it advanced to this
4703 expression; however, it has not really gone to an earlier
4704 statement---not in terms of the actual machine code.
4706 @code{until} with no argument works by means of single
4707 instruction stepping, and hence is slower than @code{until} with an
4710 @item until @var{location}
4711 @itemx u @var{location}
4712 Continue running your program until either the specified location is
4713 reached, or the current stack frame returns. @var{location} is any of
4714 the forms described in @ref{Specify Location}.
4715 This form of the command uses temporary breakpoints, and
4716 hence is quicker than @code{until} without an argument. The specified
4717 location is actually reached only if it is in the current frame. This
4718 implies that @code{until} can be used to skip over recursive function
4719 invocations. For instance in the code below, if the current location is
4720 line @code{96}, issuing @code{until 99} will execute the program up to
4721 line @code{99} in the same invocation of factorial, i.e., after the inner
4722 invocations have returned.
4725 94 int factorial (int value)
4727 96 if (value > 1) @{
4728 97 value *= factorial (value - 1);
4735 @kindex advance @var{location}
4736 @itemx advance @var{location}
4737 Continue running the program up to the given @var{location}. An argument is
4738 required, which should be of one of the forms described in
4739 @ref{Specify Location}.
4740 Execution will also stop upon exit from the current stack
4741 frame. This command is similar to @code{until}, but @code{advance} will
4742 not skip over recursive function calls, and the target location doesn't
4743 have to be in the same frame as the current one.
4747 @kindex si @r{(@code{stepi})}
4749 @itemx stepi @var{arg}
4751 Execute one machine instruction, then stop and return to the debugger.
4753 It is often useful to do @samp{display/i $pc} when stepping by machine
4754 instructions. This makes @value{GDBN} automatically display the next
4755 instruction to be executed, each time your program stops. @xref{Auto
4756 Display,, Automatic Display}.
4758 An argument is a repeat count, as in @code{step}.
4762 @kindex ni @r{(@code{nexti})}
4764 @itemx nexti @var{arg}
4766 Execute one machine instruction, but if it is a function call,
4767 proceed until the function returns.
4769 An argument is a repeat count, as in @code{next}.
4776 A signal is an asynchronous event that can happen in a program. The
4777 operating system defines the possible kinds of signals, and gives each
4778 kind a name and a number. For example, in Unix @code{SIGINT} is the
4779 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4780 @code{SIGSEGV} is the signal a program gets from referencing a place in
4781 memory far away from all the areas in use; @code{SIGALRM} occurs when
4782 the alarm clock timer goes off (which happens only if your program has
4783 requested an alarm).
4785 @cindex fatal signals
4786 Some signals, including @code{SIGALRM}, are a normal part of the
4787 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4788 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4789 program has not specified in advance some other way to handle the signal.
4790 @code{SIGINT} does not indicate an error in your program, but it is normally
4791 fatal so it can carry out the purpose of the interrupt: to kill the program.
4793 @value{GDBN} has the ability to detect any occurrence of a signal in your
4794 program. You can tell @value{GDBN} in advance what to do for each kind of
4797 @cindex handling signals
4798 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4799 @code{SIGALRM} be silently passed to your program
4800 (so as not to interfere with their role in the program's functioning)
4801 but to stop your program immediately whenever an error signal happens.
4802 You can change these settings with the @code{handle} command.
4805 @kindex info signals
4809 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4810 handle each one. You can use this to see the signal numbers of all
4811 the defined types of signals.
4813 @item info signals @var{sig}
4814 Similar, but print information only about the specified signal number.
4816 @code{info handle} is an alias for @code{info signals}.
4819 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4820 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4821 can be the number of a signal or its name (with or without the
4822 @samp{SIG} at the beginning); a list of signal numbers of the form
4823 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4824 known signals. Optional arguments @var{keywords}, described below,
4825 say what change to make.
4829 The keywords allowed by the @code{handle} command can be abbreviated.
4830 Their full names are:
4834 @value{GDBN} should not stop your program when this signal happens. It may
4835 still print a message telling you that the signal has come in.
4838 @value{GDBN} should stop your program when this signal happens. This implies
4839 the @code{print} keyword as well.
4842 @value{GDBN} should print a message when this signal happens.
4845 @value{GDBN} should not mention the occurrence of the signal at all. This
4846 implies the @code{nostop} keyword as well.
4850 @value{GDBN} should allow your program to see this signal; your program
4851 can handle the signal, or else it may terminate if the signal is fatal
4852 and not handled. @code{pass} and @code{noignore} are synonyms.
4856 @value{GDBN} should not allow your program to see this signal.
4857 @code{nopass} and @code{ignore} are synonyms.
4861 When a signal stops your program, the signal is not visible to the
4863 continue. Your program sees the signal then, if @code{pass} is in
4864 effect for the signal in question @emph{at that time}. In other words,
4865 after @value{GDBN} reports a signal, you can use the @code{handle}
4866 command with @code{pass} or @code{nopass} to control whether your
4867 program sees that signal when you continue.
4869 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4870 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4871 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4874 You can also use the @code{signal} command to prevent your program from
4875 seeing a signal, or cause it to see a signal it normally would not see,
4876 or to give it any signal at any time. For example, if your program stopped
4877 due to some sort of memory reference error, you might store correct
4878 values into the erroneous variables and continue, hoping to see more
4879 execution; but your program would probably terminate immediately as
4880 a result of the fatal signal once it saw the signal. To prevent this,
4881 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4884 @cindex extra signal information
4885 @anchor{extra signal information}
4887 On some targets, @value{GDBN} can inspect extra signal information
4888 associated with the intercepted signal, before it is actually
4889 delivered to the program being debugged. This information is exported
4890 by the convenience variable @code{$_siginfo}, and consists of data
4891 that is passed by the kernel to the signal handler at the time of the
4892 receipt of a signal. The data type of the information itself is
4893 target dependent. You can see the data type using the @code{ptype
4894 $_siginfo} command. On Unix systems, it typically corresponds to the
4895 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4898 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4899 referenced address that raised a segmentation fault.
4903 (@value{GDBP}) continue
4904 Program received signal SIGSEGV, Segmentation fault.
4905 0x0000000000400766 in main ()
4907 (@value{GDBP}) ptype $_siginfo
4914 struct @{...@} _kill;
4915 struct @{...@} _timer;
4917 struct @{...@} _sigchld;
4918 struct @{...@} _sigfault;
4919 struct @{...@} _sigpoll;
4922 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4926 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4927 $1 = (void *) 0x7ffff7ff7000
4931 Depending on target support, @code{$_siginfo} may also be writable.
4934 @section Stopping and Starting Multi-thread Programs
4936 @cindex stopped threads
4937 @cindex threads, stopped
4939 @cindex continuing threads
4940 @cindex threads, continuing
4942 @value{GDBN} supports debugging programs with multiple threads
4943 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4944 are two modes of controlling execution of your program within the
4945 debugger. In the default mode, referred to as @dfn{all-stop mode},
4946 when any thread in your program stops (for example, at a breakpoint
4947 or while being stepped), all other threads in the program are also stopped by
4948 @value{GDBN}. On some targets, @value{GDBN} also supports
4949 @dfn{non-stop mode}, in which other threads can continue to run freely while
4950 you examine the stopped thread in the debugger.
4953 * All-Stop Mode:: All threads stop when GDB takes control
4954 * Non-Stop Mode:: Other threads continue to execute
4955 * Background Execution:: Running your program asynchronously
4956 * Thread-Specific Breakpoints:: Controlling breakpoints
4957 * Interrupted System Calls:: GDB may interfere with system calls
4961 @subsection All-Stop Mode
4963 @cindex all-stop mode
4965 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4966 @emph{all} threads of execution stop, not just the current thread. This
4967 allows you to examine the overall state of the program, including
4968 switching between threads, without worrying that things may change
4971 Conversely, whenever you restart the program, @emph{all} threads start
4972 executing. @emph{This is true even when single-stepping} with commands
4973 like @code{step} or @code{next}.
4975 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4976 Since thread scheduling is up to your debugging target's operating
4977 system (not controlled by @value{GDBN}), other threads may
4978 execute more than one statement while the current thread completes a
4979 single step. Moreover, in general other threads stop in the middle of a
4980 statement, rather than at a clean statement boundary, when the program
4983 You might even find your program stopped in another thread after
4984 continuing or even single-stepping. This happens whenever some other
4985 thread runs into a breakpoint, a signal, or an exception before the
4986 first thread completes whatever you requested.
4988 @cindex automatic thread selection
4989 @cindex switching threads automatically
4990 @cindex threads, automatic switching
4991 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4992 signal, it automatically selects the thread where that breakpoint or
4993 signal happened. @value{GDBN} alerts you to the context switch with a
4994 message such as @samp{[Switching to Thread @var{n}]} to identify the
4997 On some OSes, you can modify @value{GDBN}'s default behavior by
4998 locking the OS scheduler to allow only a single thread to run.
5001 @item set scheduler-locking @var{mode}
5002 @cindex scheduler locking mode
5003 @cindex lock scheduler
5004 Set the scheduler locking mode. If it is @code{off}, then there is no
5005 locking and any thread may run at any time. If @code{on}, then only the
5006 current thread may run when the inferior is resumed. The @code{step}
5007 mode optimizes for single-stepping; it prevents other threads
5008 from preempting the current thread while you are stepping, so that
5009 the focus of debugging does not change unexpectedly.
5010 Other threads only rarely (or never) get a chance to run
5011 when you step. They are more likely to run when you @samp{next} over a
5012 function call, and they are completely free to run when you use commands
5013 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5014 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5015 the current thread away from the thread that you are debugging.
5017 @item show scheduler-locking
5018 Display the current scheduler locking mode.
5021 @cindex resume threads of multiple processes simultaneously
5022 By default, when you issue one of the execution commands such as
5023 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5024 threads of the current inferior to run. For example, if @value{GDBN}
5025 is attached to two inferiors, each with two threads, the
5026 @code{continue} command resumes only the two threads of the current
5027 inferior. This is useful, for example, when you debug a program that
5028 forks and you want to hold the parent stopped (so that, for instance,
5029 it doesn't run to exit), while you debug the child. In other
5030 situations, you may not be interested in inspecting the current state
5031 of any of the processes @value{GDBN} is attached to, and you may want
5032 to resume them all until some breakpoint is hit. In the latter case,
5033 you can instruct @value{GDBN} to allow all threads of all the
5034 inferiors to run with the @w{@code{set schedule-multiple}} command.
5037 @kindex set schedule-multiple
5038 @item set schedule-multiple
5039 Set the mode for allowing threads of multiple processes to be resumed
5040 when an execution command is issued. When @code{on}, all threads of
5041 all processes are allowed to run. When @code{off}, only the threads
5042 of the current process are resumed. The default is @code{off}. The
5043 @code{scheduler-locking} mode takes precedence when set to @code{on},
5044 or while you are stepping and set to @code{step}.
5046 @item show schedule-multiple
5047 Display the current mode for resuming the execution of threads of
5052 @subsection Non-Stop Mode
5054 @cindex non-stop mode
5056 @c This section is really only a place-holder, and needs to be expanded
5057 @c with more details.
5059 For some multi-threaded targets, @value{GDBN} supports an optional
5060 mode of operation in which you can examine stopped program threads in
5061 the debugger while other threads continue to execute freely. This
5062 minimizes intrusion when debugging live systems, such as programs
5063 where some threads have real-time constraints or must continue to
5064 respond to external events. This is referred to as @dfn{non-stop} mode.
5066 In non-stop mode, when a thread stops to report a debugging event,
5067 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5068 threads as well, in contrast to the all-stop mode behavior. Additionally,
5069 execution commands such as @code{continue} and @code{step} apply by default
5070 only to the current thread in non-stop mode, rather than all threads as
5071 in all-stop mode. This allows you to control threads explicitly in
5072 ways that are not possible in all-stop mode --- for example, stepping
5073 one thread while allowing others to run freely, stepping
5074 one thread while holding all others stopped, or stepping several threads
5075 independently and simultaneously.
5077 To enter non-stop mode, use this sequence of commands before you run
5078 or attach to your program:
5081 # Enable the async interface.
5084 # If using the CLI, pagination breaks non-stop.
5087 # Finally, turn it on!
5091 You can use these commands to manipulate the non-stop mode setting:
5094 @kindex set non-stop
5095 @item set non-stop on
5096 Enable selection of non-stop mode.
5097 @item set non-stop off
5098 Disable selection of non-stop mode.
5099 @kindex show non-stop
5101 Show the current non-stop enablement setting.
5104 Note these commands only reflect whether non-stop mode is enabled,
5105 not whether the currently-executing program is being run in non-stop mode.
5106 In particular, the @code{set non-stop} preference is only consulted when
5107 @value{GDBN} starts or connects to the target program, and it is generally
5108 not possible to switch modes once debugging has started. Furthermore,
5109 since not all targets support non-stop mode, even when you have enabled
5110 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5113 In non-stop mode, all execution commands apply only to the current thread
5114 by default. That is, @code{continue} only continues one thread.
5115 To continue all threads, issue @code{continue -a} or @code{c -a}.
5117 You can use @value{GDBN}'s background execution commands
5118 (@pxref{Background Execution}) to run some threads in the background
5119 while you continue to examine or step others from @value{GDBN}.
5120 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5121 always executed asynchronously in non-stop mode.
5123 Suspending execution is done with the @code{interrupt} command when
5124 running in the background, or @kbd{Ctrl-c} during foreground execution.
5125 In all-stop mode, this stops the whole process;
5126 but in non-stop mode the interrupt applies only to the current thread.
5127 To stop the whole program, use @code{interrupt -a}.
5129 Other execution commands do not currently support the @code{-a} option.
5131 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5132 that thread current, as it does in all-stop mode. This is because the
5133 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5134 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5135 changed to a different thread just as you entered a command to operate on the
5136 previously current thread.
5138 @node Background Execution
5139 @subsection Background Execution
5141 @cindex foreground execution
5142 @cindex background execution
5143 @cindex asynchronous execution
5144 @cindex execution, foreground, background and asynchronous
5146 @value{GDBN}'s execution commands have two variants: the normal
5147 foreground (synchronous) behavior, and a background
5148 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5149 the program to report that some thread has stopped before prompting for
5150 another command. In background execution, @value{GDBN} immediately gives
5151 a command prompt so that you can issue other commands while your program runs.
5153 You need to explicitly enable asynchronous mode before you can use
5154 background execution commands. You can use these commands to
5155 manipulate the asynchronous mode setting:
5158 @kindex set target-async
5159 @item set target-async on
5160 Enable asynchronous mode.
5161 @item set target-async off
5162 Disable asynchronous mode.
5163 @kindex show target-async
5164 @item show target-async
5165 Show the current target-async setting.
5168 If the target doesn't support async mode, @value{GDBN} issues an error
5169 message if you attempt to use the background execution commands.
5171 To specify background execution, add a @code{&} to the command. For example,
5172 the background form of the @code{continue} command is @code{continue&}, or
5173 just @code{c&}. The execution commands that accept background execution
5179 @xref{Starting, , Starting your Program}.
5183 @xref{Attach, , Debugging an Already-running Process}.
5187 @xref{Continuing and Stepping, step}.
5191 @xref{Continuing and Stepping, stepi}.
5195 @xref{Continuing and Stepping, next}.
5199 @xref{Continuing and Stepping, nexti}.
5203 @xref{Continuing and Stepping, continue}.
5207 @xref{Continuing and Stepping, finish}.
5211 @xref{Continuing and Stepping, until}.
5215 Background execution is especially useful in conjunction with non-stop
5216 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5217 However, you can also use these commands in the normal all-stop mode with
5218 the restriction that you cannot issue another execution command until the
5219 previous one finishes. Examples of commands that are valid in all-stop
5220 mode while the program is running include @code{help} and @code{info break}.
5222 You can interrupt your program while it is running in the background by
5223 using the @code{interrupt} command.
5230 Suspend execution of the running program. In all-stop mode,
5231 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5232 only the current thread. To stop the whole program in non-stop mode,
5233 use @code{interrupt -a}.
5236 @node Thread-Specific Breakpoints
5237 @subsection Thread-Specific Breakpoints
5239 When your program has multiple threads (@pxref{Threads,, Debugging
5240 Programs with Multiple Threads}), you can choose whether to set
5241 breakpoints on all threads, or on a particular thread.
5244 @cindex breakpoints and threads
5245 @cindex thread breakpoints
5246 @kindex break @dots{} thread @var{threadno}
5247 @item break @var{linespec} thread @var{threadno}
5248 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5249 @var{linespec} specifies source lines; there are several ways of
5250 writing them (@pxref{Specify Location}), but the effect is always to
5251 specify some source line.
5253 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5254 to specify that you only want @value{GDBN} to stop the program when a
5255 particular thread reaches this breakpoint. @var{threadno} is one of the
5256 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5257 column of the @samp{info threads} display.
5259 If you do not specify @samp{thread @var{threadno}} when you set a
5260 breakpoint, the breakpoint applies to @emph{all} threads of your
5263 You can use the @code{thread} qualifier on conditional breakpoints as
5264 well; in this case, place @samp{thread @var{threadno}} before or
5265 after the breakpoint condition, like this:
5268 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5273 @node Interrupted System Calls
5274 @subsection Interrupted System Calls
5276 @cindex thread breakpoints and system calls
5277 @cindex system calls and thread breakpoints
5278 @cindex premature return from system calls
5279 There is an unfortunate side effect when using @value{GDBN} to debug
5280 multi-threaded programs. If one thread stops for a
5281 breakpoint, or for some other reason, and another thread is blocked in a
5282 system call, then the system call may return prematurely. This is a
5283 consequence of the interaction between multiple threads and the signals
5284 that @value{GDBN} uses to implement breakpoints and other events that
5287 To handle this problem, your program should check the return value of
5288 each system call and react appropriately. This is good programming
5291 For example, do not write code like this:
5297 The call to @code{sleep} will return early if a different thread stops
5298 at a breakpoint or for some other reason.
5300 Instead, write this:
5305 unslept = sleep (unslept);
5308 A system call is allowed to return early, so the system is still
5309 conforming to its specification. But @value{GDBN} does cause your
5310 multi-threaded program to behave differently than it would without
5313 Also, @value{GDBN} uses internal breakpoints in the thread library to
5314 monitor certain events such as thread creation and thread destruction.
5315 When such an event happens, a system call in another thread may return
5316 prematurely, even though your program does not appear to stop.
5319 @node Reverse Execution
5320 @chapter Running programs backward
5321 @cindex reverse execution
5322 @cindex running programs backward
5324 When you are debugging a program, it is not unusual to realize that
5325 you have gone too far, and some event of interest has already happened.
5326 If the target environment supports it, @value{GDBN} can allow you to
5327 ``rewind'' the program by running it backward.
5329 A target environment that supports reverse execution should be able
5330 to ``undo'' the changes in machine state that have taken place as the
5331 program was executing normally. Variables, registers etc.@: should
5332 revert to their previous values. Obviously this requires a great
5333 deal of sophistication on the part of the target environment; not
5334 all target environments can support reverse execution.
5336 When a program is executed in reverse, the instructions that
5337 have most recently been executed are ``un-executed'', in reverse
5338 order. The program counter runs backward, following the previous
5339 thread of execution in reverse. As each instruction is ``un-executed'',
5340 the values of memory and/or registers that were changed by that
5341 instruction are reverted to their previous states. After executing
5342 a piece of source code in reverse, all side effects of that code
5343 should be ``undone'', and all variables should be returned to their
5344 prior values@footnote{
5345 Note that some side effects are easier to undo than others. For instance,
5346 memory and registers are relatively easy, but device I/O is hard. Some
5347 targets may be able undo things like device I/O, and some may not.
5349 The contract between @value{GDBN} and the reverse executing target
5350 requires only that the target do something reasonable when
5351 @value{GDBN} tells it to execute backwards, and then report the
5352 results back to @value{GDBN}. Whatever the target reports back to
5353 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5354 assumes that the memory and registers that the target reports are in a
5355 consistant state, but @value{GDBN} accepts whatever it is given.
5358 If you are debugging in a target environment that supports
5359 reverse execution, @value{GDBN} provides the following commands.
5362 @kindex reverse-continue
5363 @kindex rc @r{(@code{reverse-continue})}
5364 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5365 @itemx rc @r{[}@var{ignore-count}@r{]}
5366 Beginning at the point where your program last stopped, start executing
5367 in reverse. Reverse execution will stop for breakpoints and synchronous
5368 exceptions (signals), just like normal execution. Behavior of
5369 asynchronous signals depends on the target environment.
5371 @kindex reverse-step
5372 @kindex rs @r{(@code{step})}
5373 @item reverse-step @r{[}@var{count}@r{]}
5374 Run the program backward until control reaches the start of a
5375 different source line; then stop it, and return control to @value{GDBN}.
5377 Like the @code{step} command, @code{reverse-step} will only stop
5378 at the beginning of a source line. It ``un-executes'' the previously
5379 executed source line. If the previous source line included calls to
5380 debuggable functions, @code{reverse-step} will step (backward) into
5381 the called function, stopping at the beginning of the @emph{last}
5382 statement in the called function (typically a return statement).
5384 Also, as with the @code{step} command, if non-debuggable functions are
5385 called, @code{reverse-step} will run thru them backward without stopping.
5387 @kindex reverse-stepi
5388 @kindex rsi @r{(@code{reverse-stepi})}
5389 @item reverse-stepi @r{[}@var{count}@r{]}
5390 Reverse-execute one machine instruction. Note that the instruction
5391 to be reverse-executed is @emph{not} the one pointed to by the program
5392 counter, but the instruction executed prior to that one. For instance,
5393 if the last instruction was a jump, @code{reverse-stepi} will take you
5394 back from the destination of the jump to the jump instruction itself.
5396 @kindex reverse-next
5397 @kindex rn @r{(@code{reverse-next})}
5398 @item reverse-next @r{[}@var{count}@r{]}
5399 Run backward to the beginning of the previous line executed in
5400 the current (innermost) stack frame. If the line contains function
5401 calls, they will be ``un-executed'' without stopping. Starting from
5402 the first line of a function, @code{reverse-next} will take you back
5403 to the caller of that function, @emph{before} the function was called,
5404 just as the normal @code{next} command would take you from the last
5405 line of a function back to its return to its caller
5406 @footnote{Unless the code is too heavily optimized.}.
5408 @kindex reverse-nexti
5409 @kindex rni @r{(@code{reverse-nexti})}
5410 @item reverse-nexti @r{[}@var{count}@r{]}
5411 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5412 in reverse, except that called functions are ``un-executed'' atomically.
5413 That is, if the previously executed instruction was a return from
5414 another function, @code{reverse-nexti} will continue to execute
5415 in reverse until the call to that function (from the current stack
5418 @kindex reverse-finish
5419 @item reverse-finish
5420 Just as the @code{finish} command takes you to the point where the
5421 current function returns, @code{reverse-finish} takes you to the point
5422 where it was called. Instead of ending up at the end of the current
5423 function invocation, you end up at the beginning.
5425 @kindex set exec-direction
5426 @item set exec-direction
5427 Set the direction of target execution.
5428 @itemx set exec-direction reverse
5429 @cindex execute forward or backward in time
5430 @value{GDBN} will perform all execution commands in reverse, until the
5431 exec-direction mode is changed to ``forward''. Affected commands include
5432 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5433 command cannot be used in reverse mode.
5434 @item set exec-direction forward
5435 @value{GDBN} will perform all execution commands in the normal fashion.
5436 This is the default.
5440 @node Process Record and Replay
5441 @chapter Recording Inferior's Execution and Replaying It
5442 @cindex process record and replay
5443 @cindex recording inferior's execution and replaying it
5445 On some platforms, @value{GDBN} provides a special @dfn{process record
5446 and replay} target that can record a log of the process execution, and
5447 replay it later with both forward and reverse execution commands.
5450 When this target is in use, if the execution log includes the record
5451 for the next instruction, @value{GDBN} will debug in @dfn{replay
5452 mode}. In the replay mode, the inferior does not really execute code
5453 instructions. Instead, all the events that normally happen during
5454 code execution are taken from the execution log. While code is not
5455 really executed in replay mode, the values of registers (including the
5456 program counter register) and the memory of the inferior are still
5457 changed as they normally would. Their contents are taken from the
5461 If the record for the next instruction is not in the execution log,
5462 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5463 inferior executes normally, and @value{GDBN} records the execution log
5466 The process record and replay target supports reverse execution
5467 (@pxref{Reverse Execution}), even if the platform on which the
5468 inferior runs does not. However, the reverse execution is limited in
5469 this case by the range of the instructions recorded in the execution
5470 log. In other words, reverse execution on platforms that don't
5471 support it directly can only be done in the replay mode.
5473 When debugging in the reverse direction, @value{GDBN} will work in
5474 replay mode as long as the execution log includes the record for the
5475 previous instruction; otherwise, it will work in record mode, if the
5476 platform supports reverse execution, or stop if not.
5478 For architecture environments that support process record and replay,
5479 @value{GDBN} provides the following commands:
5482 @kindex target record
5486 This command starts the process record and replay target. The process
5487 record and replay target can only debug a process that is already
5488 running. Therefore, you need first to start the process with the
5489 @kbd{run} or @kbd{start} commands, and then start the recording with
5490 the @kbd{target record} command.
5492 Both @code{record} and @code{rec} are aliases of @code{target record}.
5494 @cindex displaced stepping, and process record and replay
5495 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5496 will be automatically disabled when process record and replay target
5497 is started. That's because the process record and replay target
5498 doesn't support displaced stepping.
5500 @cindex non-stop mode, and process record and replay
5501 @cindex asynchronous execution, and process record and replay
5502 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5503 the asynchronous execution mode (@pxref{Background Execution}), the
5504 process record and replay target cannot be started because it doesn't
5505 support these two modes.
5510 Stop the process record and replay target. When process record and
5511 replay target stops, the entire execution log will be deleted and the
5512 inferior will either be terminated, or will remain in its final state.
5514 When you stop the process record and replay target in record mode (at
5515 the end of the execution log), the inferior will be stopped at the
5516 next instruction that would have been recorded. In other words, if
5517 you record for a while and then stop recording, the inferior process
5518 will be left in the same state as if the recording never happened.
5520 On the other hand, if the process record and replay target is stopped
5521 while in replay mode (that is, not at the end of the execution log,
5522 but at some earlier point), the inferior process will become ``live''
5523 at that earlier state, and it will then be possible to continue the
5524 usual ``live'' debugging of the process from that state.
5526 When the inferior process exits, or @value{GDBN} detaches from it,
5527 process record and replay target will automatically stop itself.
5529 @kindex set record insn-number-max
5530 @item set record insn-number-max @var{limit}
5531 Set the limit of instructions to be recorded. Default value is 200000.
5533 If @var{limit} is a positive number, then @value{GDBN} will start
5534 deleting instructions from the log once the number of the record
5535 instructions becomes greater than @var{limit}. For every new recorded
5536 instruction, @value{GDBN} will delete the earliest recorded
5537 instruction to keep the number of recorded instructions at the limit.
5538 (Since deleting recorded instructions loses information, @value{GDBN}
5539 lets you control what happens when the limit is reached, by means of
5540 the @code{stop-at-limit} option, described below.)
5542 If @var{limit} is zero, @value{GDBN} will never delete recorded
5543 instructions from the execution log. The number of recorded
5544 instructions is unlimited in this case.
5546 @kindex show record insn-number-max
5547 @item show record insn-number-max
5548 Show the limit of instructions to be recorded.
5550 @kindex set record stop-at-limit
5551 @item set record stop-at-limit
5552 Control the behavior when the number of recorded instructions reaches
5553 the limit. If ON (the default), @value{GDBN} will stop when the limit
5554 is reached for the first time and ask you whether you want to stop the
5555 inferior or continue running it and recording the execution log. If
5556 you decide to continue recording, each new recorded instruction will
5557 cause the oldest one to be deleted.
5559 If this option is OFF, @value{GDBN} will automatically delete the
5560 oldest record to make room for each new one, without asking.
5562 @kindex show record stop-at-limit
5563 @item show record stop-at-limit
5564 Show the current setting of @code{stop-at-limit}.
5568 Show various statistics about the state of process record and its
5569 in-memory execution log buffer, including:
5573 Whether in record mode or replay mode.
5575 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5577 Highest recorded instruction number.
5579 Current instruction about to be replayed (if in replay mode).
5581 Number of instructions contained in the execution log.
5583 Maximum number of instructions that may be contained in the execution log.
5586 @kindex record delete
5589 When record target runs in replay mode (``in the past''), delete the
5590 subsequent execution log and begin to record a new execution log starting
5591 from the current address. This means you will abandon the previously
5592 recorded ``future'' and begin recording a new ``future''.
5597 @chapter Examining the Stack
5599 When your program has stopped, the first thing you need to know is where it
5600 stopped and how it got there.
5603 Each time your program performs a function call, information about the call
5605 That information includes the location of the call in your program,
5606 the arguments of the call,
5607 and the local variables of the function being called.
5608 The information is saved in a block of data called a @dfn{stack frame}.
5609 The stack frames are allocated in a region of memory called the @dfn{call
5612 When your program stops, the @value{GDBN} commands for examining the
5613 stack allow you to see all of this information.
5615 @cindex selected frame
5616 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5617 @value{GDBN} commands refer implicitly to the selected frame. In
5618 particular, whenever you ask @value{GDBN} for the value of a variable in
5619 your program, the value is found in the selected frame. There are
5620 special @value{GDBN} commands to select whichever frame you are
5621 interested in. @xref{Selection, ,Selecting a Frame}.
5623 When your program stops, @value{GDBN} automatically selects the
5624 currently executing frame and describes it briefly, similar to the
5625 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5628 * Frames:: Stack frames
5629 * Backtrace:: Backtraces
5630 * Selection:: Selecting a frame
5631 * Frame Info:: Information on a frame
5636 @section Stack Frames
5638 @cindex frame, definition
5640 The call stack is divided up into contiguous pieces called @dfn{stack
5641 frames}, or @dfn{frames} for short; each frame is the data associated
5642 with one call to one function. The frame contains the arguments given
5643 to the function, the function's local variables, and the address at
5644 which the function is executing.
5646 @cindex initial frame
5647 @cindex outermost frame
5648 @cindex innermost frame
5649 When your program is started, the stack has only one frame, that of the
5650 function @code{main}. This is called the @dfn{initial} frame or the
5651 @dfn{outermost} frame. Each time a function is called, a new frame is
5652 made. Each time a function returns, the frame for that function invocation
5653 is eliminated. If a function is recursive, there can be many frames for
5654 the same function. The frame for the function in which execution is
5655 actually occurring is called the @dfn{innermost} frame. This is the most
5656 recently created of all the stack frames that still exist.
5658 @cindex frame pointer
5659 Inside your program, stack frames are identified by their addresses. A
5660 stack frame consists of many bytes, each of which has its own address; each
5661 kind of computer has a convention for choosing one byte whose
5662 address serves as the address of the frame. Usually this address is kept
5663 in a register called the @dfn{frame pointer register}
5664 (@pxref{Registers, $fp}) while execution is going on in that frame.
5666 @cindex frame number
5667 @value{GDBN} assigns numbers to all existing stack frames, starting with
5668 zero for the innermost frame, one for the frame that called it,
5669 and so on upward. These numbers do not really exist in your program;
5670 they are assigned by @value{GDBN} to give you a way of designating stack
5671 frames in @value{GDBN} commands.
5673 @c The -fomit-frame-pointer below perennially causes hbox overflow
5674 @c underflow problems.
5675 @cindex frameless execution
5676 Some compilers provide a way to compile functions so that they operate
5677 without stack frames. (For example, the @value{NGCC} option
5679 @samp{-fomit-frame-pointer}
5681 generates functions without a frame.)
5682 This is occasionally done with heavily used library functions to save
5683 the frame setup time. @value{GDBN} has limited facilities for dealing
5684 with these function invocations. If the innermost function invocation
5685 has no stack frame, @value{GDBN} nevertheless regards it as though
5686 it had a separate frame, which is numbered zero as usual, allowing
5687 correct tracing of the function call chain. However, @value{GDBN} has
5688 no provision for frameless functions elsewhere in the stack.
5691 @kindex frame@r{, command}
5692 @cindex current stack frame
5693 @item frame @var{args}
5694 The @code{frame} command allows you to move from one stack frame to another,
5695 and to print the stack frame you select. @var{args} may be either the
5696 address of the frame or the stack frame number. Without an argument,
5697 @code{frame} prints the current stack frame.
5699 @kindex select-frame
5700 @cindex selecting frame silently
5702 The @code{select-frame} command allows you to move from one stack frame
5703 to another without printing the frame. This is the silent version of
5711 @cindex call stack traces
5712 A backtrace is a summary of how your program got where it is. It shows one
5713 line per frame, for many frames, starting with the currently executing
5714 frame (frame zero), followed by its caller (frame one), and on up the
5719 @kindex bt @r{(@code{backtrace})}
5722 Print a backtrace of the entire stack: one line per frame for all
5723 frames in the stack.
5725 You can stop the backtrace at any time by typing the system interrupt
5726 character, normally @kbd{Ctrl-c}.
5728 @item backtrace @var{n}
5730 Similar, but print only the innermost @var{n} frames.
5732 @item backtrace -@var{n}
5734 Similar, but print only the outermost @var{n} frames.
5736 @item backtrace full
5738 @itemx bt full @var{n}
5739 @itemx bt full -@var{n}
5740 Print the values of the local variables also. @var{n} specifies the
5741 number of frames to print, as described above.
5746 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5747 are additional aliases for @code{backtrace}.
5749 @cindex multiple threads, backtrace
5750 In a multi-threaded program, @value{GDBN} by default shows the
5751 backtrace only for the current thread. To display the backtrace for
5752 several or all of the threads, use the command @code{thread apply}
5753 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5754 apply all backtrace}, @value{GDBN} will display the backtrace for all
5755 the threads; this is handy when you debug a core dump of a
5756 multi-threaded program.
5758 Each line in the backtrace shows the frame number and the function name.
5759 The program counter value is also shown---unless you use @code{set
5760 print address off}. The backtrace also shows the source file name and
5761 line number, as well as the arguments to the function. The program
5762 counter value is omitted if it is at the beginning of the code for that
5765 Here is an example of a backtrace. It was made with the command
5766 @samp{bt 3}, so it shows the innermost three frames.
5770 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5772 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5773 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5775 (More stack frames follow...)
5780 The display for frame zero does not begin with a program counter
5781 value, indicating that your program has stopped at the beginning of the
5782 code for line @code{993} of @code{builtin.c}.
5785 The value of parameter @code{data} in frame 1 has been replaced by
5786 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5787 only if it is a scalar (integer, pointer, enumeration, etc). See command
5788 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5789 on how to configure the way function parameter values are printed.
5791 @cindex value optimized out, in backtrace
5792 @cindex function call arguments, optimized out
5793 If your program was compiled with optimizations, some compilers will
5794 optimize away arguments passed to functions if those arguments are
5795 never used after the call. Such optimizations generate code that
5796 passes arguments through registers, but doesn't store those arguments
5797 in the stack frame. @value{GDBN} has no way of displaying such
5798 arguments in stack frames other than the innermost one. Here's what
5799 such a backtrace might look like:
5803 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5805 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5806 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5808 (More stack frames follow...)
5813 The values of arguments that were not saved in their stack frames are
5814 shown as @samp{<value optimized out>}.
5816 If you need to display the values of such optimized-out arguments,
5817 either deduce that from other variables whose values depend on the one
5818 you are interested in, or recompile without optimizations.
5820 @cindex backtrace beyond @code{main} function
5821 @cindex program entry point
5822 @cindex startup code, and backtrace
5823 Most programs have a standard user entry point---a place where system
5824 libraries and startup code transition into user code. For C this is
5825 @code{main}@footnote{
5826 Note that embedded programs (the so-called ``free-standing''
5827 environment) are not required to have a @code{main} function as the
5828 entry point. They could even have multiple entry points.}.
5829 When @value{GDBN} finds the entry function in a backtrace
5830 it will terminate the backtrace, to avoid tracing into highly
5831 system-specific (and generally uninteresting) code.
5833 If you need to examine the startup code, or limit the number of levels
5834 in a backtrace, you can change this behavior:
5837 @item set backtrace past-main
5838 @itemx set backtrace past-main on
5839 @kindex set backtrace
5840 Backtraces will continue past the user entry point.
5842 @item set backtrace past-main off
5843 Backtraces will stop when they encounter the user entry point. This is the
5846 @item show backtrace past-main
5847 @kindex show backtrace
5848 Display the current user entry point backtrace policy.
5850 @item set backtrace past-entry
5851 @itemx set backtrace past-entry on
5852 Backtraces will continue past the internal entry point of an application.
5853 This entry point is encoded by the linker when the application is built,
5854 and is likely before the user entry point @code{main} (or equivalent) is called.
5856 @item set backtrace past-entry off
5857 Backtraces will stop when they encounter the internal entry point of an
5858 application. This is the default.
5860 @item show backtrace past-entry
5861 Display the current internal entry point backtrace policy.
5863 @item set backtrace limit @var{n}
5864 @itemx set backtrace limit 0
5865 @cindex backtrace limit
5866 Limit the backtrace to @var{n} levels. A value of zero means
5869 @item show backtrace limit
5870 Display the current limit on backtrace levels.
5874 @section Selecting a Frame
5876 Most commands for examining the stack and other data in your program work on
5877 whichever stack frame is selected at the moment. Here are the commands for
5878 selecting a stack frame; all of them finish by printing a brief description
5879 of the stack frame just selected.
5882 @kindex frame@r{, selecting}
5883 @kindex f @r{(@code{frame})}
5886 Select frame number @var{n}. Recall that frame zero is the innermost
5887 (currently executing) frame, frame one is the frame that called the
5888 innermost one, and so on. The highest-numbered frame is the one for
5891 @item frame @var{addr}
5893 Select the frame at address @var{addr}. This is useful mainly if the
5894 chaining of stack frames has been damaged by a bug, making it
5895 impossible for @value{GDBN} to assign numbers properly to all frames. In
5896 addition, this can be useful when your program has multiple stacks and
5897 switches between them.
5899 On the SPARC architecture, @code{frame} needs two addresses to
5900 select an arbitrary frame: a frame pointer and a stack pointer.
5902 On the MIPS and Alpha architecture, it needs two addresses: a stack
5903 pointer and a program counter.
5905 On the 29k architecture, it needs three addresses: a register stack
5906 pointer, a program counter, and a memory stack pointer.
5910 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5911 advances toward the outermost frame, to higher frame numbers, to frames
5912 that have existed longer. @var{n} defaults to one.
5915 @kindex do @r{(@code{down})}
5917 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5918 advances toward the innermost frame, to lower frame numbers, to frames
5919 that were created more recently. @var{n} defaults to one. You may
5920 abbreviate @code{down} as @code{do}.
5923 All of these commands end by printing two lines of output describing the
5924 frame. The first line shows the frame number, the function name, the
5925 arguments, and the source file and line number of execution in that
5926 frame. The second line shows the text of that source line.
5934 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5936 10 read_input_file (argv[i]);
5940 After such a printout, the @code{list} command with no arguments
5941 prints ten lines centered on the point of execution in the frame.
5942 You can also edit the program at the point of execution with your favorite
5943 editing program by typing @code{edit}.
5944 @xref{List, ,Printing Source Lines},
5948 @kindex down-silently
5950 @item up-silently @var{n}
5951 @itemx down-silently @var{n}
5952 These two commands are variants of @code{up} and @code{down},
5953 respectively; they differ in that they do their work silently, without
5954 causing display of the new frame. They are intended primarily for use
5955 in @value{GDBN} command scripts, where the output might be unnecessary and
5960 @section Information About a Frame
5962 There are several other commands to print information about the selected
5968 When used without any argument, this command does not change which
5969 frame is selected, but prints a brief description of the currently
5970 selected stack frame. It can be abbreviated @code{f}. With an
5971 argument, this command is used to select a stack frame.
5972 @xref{Selection, ,Selecting a Frame}.
5975 @kindex info f @r{(@code{info frame})}
5978 This command prints a verbose description of the selected stack frame,
5983 the address of the frame
5985 the address of the next frame down (called by this frame)
5987 the address of the next frame up (caller of this frame)
5989 the language in which the source code corresponding to this frame is written
5991 the address of the frame's arguments
5993 the address of the frame's local variables
5995 the program counter saved in it (the address of execution in the caller frame)
5997 which registers were saved in the frame
6000 @noindent The verbose description is useful when
6001 something has gone wrong that has made the stack format fail to fit
6002 the usual conventions.
6004 @item info frame @var{addr}
6005 @itemx info f @var{addr}
6006 Print a verbose description of the frame at address @var{addr}, without
6007 selecting that frame. The selected frame remains unchanged by this
6008 command. This requires the same kind of address (more than one for some
6009 architectures) that you specify in the @code{frame} command.
6010 @xref{Selection, ,Selecting a Frame}.
6014 Print the arguments of the selected frame, each on a separate line.
6018 Print the local variables of the selected frame, each on a separate
6019 line. These are all variables (declared either static or automatic)
6020 accessible at the point of execution of the selected frame.
6023 @cindex catch exceptions, list active handlers
6024 @cindex exception handlers, how to list
6026 Print a list of all the exception handlers that are active in the
6027 current stack frame at the current point of execution. To see other
6028 exception handlers, visit the associated frame (using the @code{up},
6029 @code{down}, or @code{frame} commands); then type @code{info catch}.
6030 @xref{Set Catchpoints, , Setting Catchpoints}.
6036 @chapter Examining Source Files
6038 @value{GDBN} can print parts of your program's source, since the debugging
6039 information recorded in the program tells @value{GDBN} what source files were
6040 used to build it. When your program stops, @value{GDBN} spontaneously prints
6041 the line where it stopped. Likewise, when you select a stack frame
6042 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6043 execution in that frame has stopped. You can print other portions of
6044 source files by explicit command.
6046 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6047 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6048 @value{GDBN} under @sc{gnu} Emacs}.
6051 * List:: Printing source lines
6052 * Specify Location:: How to specify code locations
6053 * Edit:: Editing source files
6054 * Search:: Searching source files
6055 * Source Path:: Specifying source directories
6056 * Machine Code:: Source and machine code
6060 @section Printing Source Lines
6063 @kindex l @r{(@code{list})}
6064 To print lines from a source file, use the @code{list} command
6065 (abbreviated @code{l}). By default, ten lines are printed.
6066 There are several ways to specify what part of the file you want to
6067 print; see @ref{Specify Location}, for the full list.
6069 Here are the forms of the @code{list} command most commonly used:
6072 @item list @var{linenum}
6073 Print lines centered around line number @var{linenum} in the
6074 current source file.
6076 @item list @var{function}
6077 Print lines centered around the beginning of function
6081 Print more lines. If the last lines printed were printed with a
6082 @code{list} command, this prints lines following the last lines
6083 printed; however, if the last line printed was a solitary line printed
6084 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6085 Stack}), this prints lines centered around that line.
6088 Print lines just before the lines last printed.
6091 @cindex @code{list}, how many lines to display
6092 By default, @value{GDBN} prints ten source lines with any of these forms of
6093 the @code{list} command. You can change this using @code{set listsize}:
6096 @kindex set listsize
6097 @item set listsize @var{count}
6098 Make the @code{list} command display @var{count} source lines (unless
6099 the @code{list} argument explicitly specifies some other number).
6101 @kindex show listsize
6103 Display the number of lines that @code{list} prints.
6106 Repeating a @code{list} command with @key{RET} discards the argument,
6107 so it is equivalent to typing just @code{list}. This is more useful
6108 than listing the same lines again. An exception is made for an
6109 argument of @samp{-}; that argument is preserved in repetition so that
6110 each repetition moves up in the source file.
6112 In general, the @code{list} command expects you to supply zero, one or two
6113 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6114 of writing them (@pxref{Specify Location}), but the effect is always
6115 to specify some source line.
6117 Here is a complete description of the possible arguments for @code{list}:
6120 @item list @var{linespec}
6121 Print lines centered around the line specified by @var{linespec}.
6123 @item list @var{first},@var{last}
6124 Print lines from @var{first} to @var{last}. Both arguments are
6125 linespecs. When a @code{list} command has two linespecs, and the
6126 source file of the second linespec is omitted, this refers to
6127 the same source file as the first linespec.
6129 @item list ,@var{last}
6130 Print lines ending with @var{last}.
6132 @item list @var{first},
6133 Print lines starting with @var{first}.
6136 Print lines just after the lines last printed.
6139 Print lines just before the lines last printed.
6142 As described in the preceding table.
6145 @node Specify Location
6146 @section Specifying a Location
6147 @cindex specifying location
6150 Several @value{GDBN} commands accept arguments that specify a location
6151 of your program's code. Since @value{GDBN} is a source-level
6152 debugger, a location usually specifies some line in the source code;
6153 for that reason, locations are also known as @dfn{linespecs}.
6155 Here are all the different ways of specifying a code location that
6156 @value{GDBN} understands:
6160 Specifies the line number @var{linenum} of the current source file.
6163 @itemx +@var{offset}
6164 Specifies the line @var{offset} lines before or after the @dfn{current
6165 line}. For the @code{list} command, the current line is the last one
6166 printed; for the breakpoint commands, this is the line at which
6167 execution stopped in the currently selected @dfn{stack frame}
6168 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6169 used as the second of the two linespecs in a @code{list} command,
6170 this specifies the line @var{offset} lines up or down from the first
6173 @item @var{filename}:@var{linenum}
6174 Specifies the line @var{linenum} in the source file @var{filename}.
6176 @item @var{function}
6177 Specifies the line that begins the body of the function @var{function}.
6178 For example, in C, this is the line with the open brace.
6180 @item @var{filename}:@var{function}
6181 Specifies the line that begins the body of the function @var{function}
6182 in the file @var{filename}. You only need the file name with a
6183 function name to avoid ambiguity when there are identically named
6184 functions in different source files.
6186 @item *@var{address}
6187 Specifies the program address @var{address}. For line-oriented
6188 commands, such as @code{list} and @code{edit}, this specifies a source
6189 line that contains @var{address}. For @code{break} and other
6190 breakpoint oriented commands, this can be used to set breakpoints in
6191 parts of your program which do not have debugging information or
6194 Here @var{address} may be any expression valid in the current working
6195 language (@pxref{Languages, working language}) that specifies a code
6196 address. In addition, as a convenience, @value{GDBN} extends the
6197 semantics of expressions used in locations to cover the situations
6198 that frequently happen during debugging. Here are the various forms
6202 @item @var{expression}
6203 Any expression valid in the current working language.
6205 @item @var{funcaddr}
6206 An address of a function or procedure derived from its name. In C,
6207 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6208 simply the function's name @var{function} (and actually a special case
6209 of a valid expression). In Pascal and Modula-2, this is
6210 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6211 (although the Pascal form also works).
6213 This form specifies the address of the function's first instruction,
6214 before the stack frame and arguments have been set up.
6216 @item '@var{filename}'::@var{funcaddr}
6217 Like @var{funcaddr} above, but also specifies the name of the source
6218 file explicitly. This is useful if the name of the function does not
6219 specify the function unambiguously, e.g., if there are several
6220 functions with identical names in different source files.
6227 @section Editing Source Files
6228 @cindex editing source files
6231 @kindex e @r{(@code{edit})}
6232 To edit the lines in a source file, use the @code{edit} command.
6233 The editing program of your choice
6234 is invoked with the current line set to
6235 the active line in the program.
6236 Alternatively, there are several ways to specify what part of the file you
6237 want to print if you want to see other parts of the program:
6240 @item edit @var{location}
6241 Edit the source file specified by @code{location}. Editing starts at
6242 that @var{location}, e.g., at the specified source line of the
6243 specified file. @xref{Specify Location}, for all the possible forms
6244 of the @var{location} argument; here are the forms of the @code{edit}
6245 command most commonly used:
6248 @item edit @var{number}
6249 Edit the current source file with @var{number} as the active line number.
6251 @item edit @var{function}
6252 Edit the file containing @var{function} at the beginning of its definition.
6257 @subsection Choosing your Editor
6258 You can customize @value{GDBN} to use any editor you want
6260 The only restriction is that your editor (say @code{ex}), recognizes the
6261 following command-line syntax:
6263 ex +@var{number} file
6265 The optional numeric value +@var{number} specifies the number of the line in
6266 the file where to start editing.}.
6267 By default, it is @file{@value{EDITOR}}, but you can change this
6268 by setting the environment variable @code{EDITOR} before using
6269 @value{GDBN}. For example, to configure @value{GDBN} to use the
6270 @code{vi} editor, you could use these commands with the @code{sh} shell:
6276 or in the @code{csh} shell,
6278 setenv EDITOR /usr/bin/vi
6283 @section Searching Source Files
6284 @cindex searching source files
6286 There are two commands for searching through the current source file for a
6291 @kindex forward-search
6292 @item forward-search @var{regexp}
6293 @itemx search @var{regexp}
6294 The command @samp{forward-search @var{regexp}} checks each line,
6295 starting with the one following the last line listed, for a match for
6296 @var{regexp}. It lists the line that is found. You can use the
6297 synonym @samp{search @var{regexp}} or abbreviate the command name as
6300 @kindex reverse-search
6301 @item reverse-search @var{regexp}
6302 The command @samp{reverse-search @var{regexp}} checks each line, starting
6303 with the one before the last line listed and going backward, for a match
6304 for @var{regexp}. It lists the line that is found. You can abbreviate
6305 this command as @code{rev}.
6309 @section Specifying Source Directories
6312 @cindex directories for source files
6313 Executable programs sometimes do not record the directories of the source
6314 files from which they were compiled, just the names. Even when they do,
6315 the directories could be moved between the compilation and your debugging
6316 session. @value{GDBN} has a list of directories to search for source files;
6317 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6318 it tries all the directories in the list, in the order they are present
6319 in the list, until it finds a file with the desired name.
6321 For example, suppose an executable references the file
6322 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6323 @file{/mnt/cross}. The file is first looked up literally; if this
6324 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6325 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6326 message is printed. @value{GDBN} does not look up the parts of the
6327 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6328 Likewise, the subdirectories of the source path are not searched: if
6329 the source path is @file{/mnt/cross}, and the binary refers to
6330 @file{foo.c}, @value{GDBN} would not find it under
6331 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6333 Plain file names, relative file names with leading directories, file
6334 names containing dots, etc.@: are all treated as described above; for
6335 instance, if the source path is @file{/mnt/cross}, and the source file
6336 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6337 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6338 that---@file{/mnt/cross/foo.c}.
6340 Note that the executable search path is @emph{not} used to locate the
6343 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6344 any information it has cached about where source files are found and where
6345 each line is in the file.
6349 When you start @value{GDBN}, its source path includes only @samp{cdir}
6350 and @samp{cwd}, in that order.
6351 To add other directories, use the @code{directory} command.
6353 The search path is used to find both program source files and @value{GDBN}
6354 script files (read using the @samp{-command} option and @samp{source} command).
6356 In addition to the source path, @value{GDBN} provides a set of commands
6357 that manage a list of source path substitution rules. A @dfn{substitution
6358 rule} specifies how to rewrite source directories stored in the program's
6359 debug information in case the sources were moved to a different
6360 directory between compilation and debugging. A rule is made of
6361 two strings, the first specifying what needs to be rewritten in
6362 the path, and the second specifying how it should be rewritten.
6363 In @ref{set substitute-path}, we name these two parts @var{from} and
6364 @var{to} respectively. @value{GDBN} does a simple string replacement
6365 of @var{from} with @var{to} at the start of the directory part of the
6366 source file name, and uses that result instead of the original file
6367 name to look up the sources.
6369 Using the previous example, suppose the @file{foo-1.0} tree has been
6370 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6371 @value{GDBN} to replace @file{/usr/src} in all source path names with
6372 @file{/mnt/cross}. The first lookup will then be
6373 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6374 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6375 substitution rule, use the @code{set substitute-path} command
6376 (@pxref{set substitute-path}).
6378 To avoid unexpected substitution results, a rule is applied only if the
6379 @var{from} part of the directory name ends at a directory separator.
6380 For instance, a rule substituting @file{/usr/source} into
6381 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6382 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6383 is applied only at the beginning of the directory name, this rule will
6384 not be applied to @file{/root/usr/source/baz.c} either.
6386 In many cases, you can achieve the same result using the @code{directory}
6387 command. However, @code{set substitute-path} can be more efficient in
6388 the case where the sources are organized in a complex tree with multiple
6389 subdirectories. With the @code{directory} command, you need to add each
6390 subdirectory of your project. If you moved the entire tree while
6391 preserving its internal organization, then @code{set substitute-path}
6392 allows you to direct the debugger to all the sources with one single
6395 @code{set substitute-path} is also more than just a shortcut command.
6396 The source path is only used if the file at the original location no
6397 longer exists. On the other hand, @code{set substitute-path} modifies
6398 the debugger behavior to look at the rewritten location instead. So, if
6399 for any reason a source file that is not relevant to your executable is
6400 located at the original location, a substitution rule is the only
6401 method available to point @value{GDBN} at the new location.
6403 @cindex @samp{--with-relocated-sources}
6404 @cindex default source path substitution
6405 You can configure a default source path substitution rule by
6406 configuring @value{GDBN} with the
6407 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6408 should be the name of a directory under @value{GDBN}'s configured
6409 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6410 directory names in debug information under @var{dir} will be adjusted
6411 automatically if the installed @value{GDBN} is moved to a new
6412 location. This is useful if @value{GDBN}, libraries or executables
6413 with debug information and corresponding source code are being moved
6417 @item directory @var{dirname} @dots{}
6418 @item dir @var{dirname} @dots{}
6419 Add directory @var{dirname} to the front of the source path. Several
6420 directory names may be given to this command, separated by @samp{:}
6421 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6422 part of absolute file names) or
6423 whitespace. You may specify a directory that is already in the source
6424 path; this moves it forward, so @value{GDBN} searches it sooner.
6428 @vindex $cdir@r{, convenience variable}
6429 @vindex $cwd@r{, convenience variable}
6430 @cindex compilation directory
6431 @cindex current directory
6432 @cindex working directory
6433 @cindex directory, current
6434 @cindex directory, compilation
6435 You can use the string @samp{$cdir} to refer to the compilation
6436 directory (if one is recorded), and @samp{$cwd} to refer to the current
6437 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6438 tracks the current working directory as it changes during your @value{GDBN}
6439 session, while the latter is immediately expanded to the current
6440 directory at the time you add an entry to the source path.
6443 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6445 @c RET-repeat for @code{directory} is explicitly disabled, but since
6446 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6448 @item show directories
6449 @kindex show directories
6450 Print the source path: show which directories it contains.
6452 @anchor{set substitute-path}
6453 @item set substitute-path @var{from} @var{to}
6454 @kindex set substitute-path
6455 Define a source path substitution rule, and add it at the end of the
6456 current list of existing substitution rules. If a rule with the same
6457 @var{from} was already defined, then the old rule is also deleted.
6459 For example, if the file @file{/foo/bar/baz.c} was moved to
6460 @file{/mnt/cross/baz.c}, then the command
6463 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6467 will tell @value{GDBN} to replace @samp{/usr/src} with
6468 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6469 @file{baz.c} even though it was moved.
6471 In the case when more than one substitution rule have been defined,
6472 the rules are evaluated one by one in the order where they have been
6473 defined. The first one matching, if any, is selected to perform
6476 For instance, if we had entered the following commands:
6479 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6480 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6484 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6485 @file{/mnt/include/defs.h} by using the first rule. However, it would
6486 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6487 @file{/mnt/src/lib/foo.c}.
6490 @item unset substitute-path [path]
6491 @kindex unset substitute-path
6492 If a path is specified, search the current list of substitution rules
6493 for a rule that would rewrite that path. Delete that rule if found.
6494 A warning is emitted by the debugger if no rule could be found.
6496 If no path is specified, then all substitution rules are deleted.
6498 @item show substitute-path [path]
6499 @kindex show substitute-path
6500 If a path is specified, then print the source path substitution rule
6501 which would rewrite that path, if any.
6503 If no path is specified, then print all existing source path substitution
6508 If your source path is cluttered with directories that are no longer of
6509 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6510 versions of source. You can correct the situation as follows:
6514 Use @code{directory} with no argument to reset the source path to its default value.
6517 Use @code{directory} with suitable arguments to reinstall the
6518 directories you want in the source path. You can add all the
6519 directories in one command.
6523 @section Source and Machine Code
6524 @cindex source line and its code address
6526 You can use the command @code{info line} to map source lines to program
6527 addresses (and vice versa), and the command @code{disassemble} to display
6528 a range of addresses as machine instructions. You can use the command
6529 @code{set disassemble-next-line} to set whether to disassemble next
6530 source line when execution stops. When run under @sc{gnu} Emacs
6531 mode, the @code{info line} command causes the arrow to point to the
6532 line specified. Also, @code{info line} prints addresses in symbolic form as
6537 @item info line @var{linespec}
6538 Print the starting and ending addresses of the compiled code for
6539 source line @var{linespec}. You can specify source lines in any of
6540 the ways documented in @ref{Specify Location}.
6543 For example, we can use @code{info line} to discover the location of
6544 the object code for the first line of function
6545 @code{m4_changequote}:
6547 @c FIXME: I think this example should also show the addresses in
6548 @c symbolic form, as they usually would be displayed.
6550 (@value{GDBP}) info line m4_changequote
6551 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6555 @cindex code address and its source line
6556 We can also inquire (using @code{*@var{addr}} as the form for
6557 @var{linespec}) what source line covers a particular address:
6559 (@value{GDBP}) info line *0x63ff
6560 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6563 @cindex @code{$_} and @code{info line}
6564 @cindex @code{x} command, default address
6565 @kindex x@r{(examine), and} info line
6566 After @code{info line}, the default address for the @code{x} command
6567 is changed to the starting address of the line, so that @samp{x/i} is
6568 sufficient to begin examining the machine code (@pxref{Memory,
6569 ,Examining Memory}). Also, this address is saved as the value of the
6570 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6575 @cindex assembly instructions
6576 @cindex instructions, assembly
6577 @cindex machine instructions
6578 @cindex listing machine instructions
6580 @itemx disassemble /m
6581 @itemx disassemble /r
6582 This specialized command dumps a range of memory as machine
6583 instructions. It can also print mixed source+disassembly by specifying
6584 the @code{/m} modifier and print the raw instructions in hex as well as
6585 in symbolic form by specifying the @code{/r}.
6586 The default memory range is the function surrounding the
6587 program counter of the selected frame. A single argument to this
6588 command is a program counter value; @value{GDBN} dumps the function
6589 surrounding this value. When two arguments are given, they should
6590 be separated by a comma, possibly surrounded by whitespace. The
6591 arguments specify a range of addresses (first inclusive, second exclusive)
6592 to dump. In that case, the name of the function is also printed (since
6593 there could be several functions in the given range).
6595 The argument(s) can be any expression yielding a numeric value, such as
6596 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6598 If the range of memory being disassembled contains current program counter,
6599 the instruction at that location is shown with a @code{=>} marker.
6602 The following example shows the disassembly of a range of addresses of
6603 HP PA-RISC 2.0 code:
6606 (@value{GDBP}) disas 0x32c4, 0x32e4
6607 Dump of assembler code from 0x32c4 to 0x32e4:
6608 0x32c4 <main+204>: addil 0,dp
6609 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6610 0x32cc <main+212>: ldil 0x3000,r31
6611 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6612 0x32d4 <main+220>: ldo 0(r31),rp
6613 0x32d8 <main+224>: addil -0x800,dp
6614 0x32dc <main+228>: ldo 0x588(r1),r26
6615 0x32e0 <main+232>: ldil 0x3000,r31
6616 End of assembler dump.
6619 Here is an example showing mixed source+assembly for Intel x86, when the
6620 program is stopped just after function prologue:
6623 (@value{GDBP}) disas /m main
6624 Dump of assembler code for function main:
6626 0x08048330 <+0>: push %ebp
6627 0x08048331 <+1>: mov %esp,%ebp
6628 0x08048333 <+3>: sub $0x8,%esp
6629 0x08048336 <+6>: and $0xfffffff0,%esp
6630 0x08048339 <+9>: sub $0x10,%esp
6632 6 printf ("Hello.\n");
6633 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6634 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6638 0x08048348 <+24>: mov $0x0,%eax
6639 0x0804834d <+29>: leave
6640 0x0804834e <+30>: ret
6642 End of assembler dump.
6645 Some architectures have more than one commonly-used set of instruction
6646 mnemonics or other syntax.
6648 For programs that were dynamically linked and use shared libraries,
6649 instructions that call functions or branch to locations in the shared
6650 libraries might show a seemingly bogus location---it's actually a
6651 location of the relocation table. On some architectures, @value{GDBN}
6652 might be able to resolve these to actual function names.
6655 @kindex set disassembly-flavor
6656 @cindex Intel disassembly flavor
6657 @cindex AT&T disassembly flavor
6658 @item set disassembly-flavor @var{instruction-set}
6659 Select the instruction set to use when disassembling the
6660 program via the @code{disassemble} or @code{x/i} commands.
6662 Currently this command is only defined for the Intel x86 family. You
6663 can set @var{instruction-set} to either @code{intel} or @code{att}.
6664 The default is @code{att}, the AT&T flavor used by default by Unix
6665 assemblers for x86-based targets.
6667 @kindex show disassembly-flavor
6668 @item show disassembly-flavor
6669 Show the current setting of the disassembly flavor.
6673 @kindex set disassemble-next-line
6674 @kindex show disassemble-next-line
6675 @item set disassemble-next-line
6676 @itemx show disassemble-next-line
6677 Control whether or not @value{GDBN} will disassemble the next source
6678 line or instruction when execution stops. If ON, @value{GDBN} will
6679 display disassembly of the next source line when execution of the
6680 program being debugged stops. This is @emph{in addition} to
6681 displaying the source line itself, which @value{GDBN} always does if
6682 possible. If the next source line cannot be displayed for some reason
6683 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6684 info in the debug info), @value{GDBN} will display disassembly of the
6685 next @emph{instruction} instead of showing the next source line. If
6686 AUTO, @value{GDBN} will display disassembly of next instruction only
6687 if the source line cannot be displayed. This setting causes
6688 @value{GDBN} to display some feedback when you step through a function
6689 with no line info or whose source file is unavailable. The default is
6690 OFF, which means never display the disassembly of the next line or
6696 @chapter Examining Data
6698 @cindex printing data
6699 @cindex examining data
6702 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6703 @c document because it is nonstandard... Under Epoch it displays in a
6704 @c different window or something like that.
6705 The usual way to examine data in your program is with the @code{print}
6706 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6707 evaluates and prints the value of an expression of the language your
6708 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6709 Different Languages}). It may also print the expression using a
6710 Python-based pretty-printer (@pxref{Pretty Printing}).
6713 @item print @var{expr}
6714 @itemx print /@var{f} @var{expr}
6715 @var{expr} is an expression (in the source language). By default the
6716 value of @var{expr} is printed in a format appropriate to its data type;
6717 you can choose a different format by specifying @samp{/@var{f}}, where
6718 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6722 @itemx print /@var{f}
6723 @cindex reprint the last value
6724 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6725 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6726 conveniently inspect the same value in an alternative format.
6729 A more low-level way of examining data is with the @code{x} command.
6730 It examines data in memory at a specified address and prints it in a
6731 specified format. @xref{Memory, ,Examining Memory}.
6733 If you are interested in information about types, or about how the
6734 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6735 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6739 * Expressions:: Expressions
6740 * Ambiguous Expressions:: Ambiguous Expressions
6741 * Variables:: Program variables
6742 * Arrays:: Artificial arrays
6743 * Output Formats:: Output formats
6744 * Memory:: Examining memory
6745 * Auto Display:: Automatic display
6746 * Print Settings:: Print settings
6747 * Pretty Printing:: Python pretty printing
6748 * Value History:: Value history
6749 * Convenience Vars:: Convenience variables
6750 * Registers:: Registers
6751 * Floating Point Hardware:: Floating point hardware
6752 * Vector Unit:: Vector Unit
6753 * OS Information:: Auxiliary data provided by operating system
6754 * Memory Region Attributes:: Memory region attributes
6755 * Dump/Restore Files:: Copy between memory and a file
6756 * Core File Generation:: Cause a program dump its core
6757 * Character Sets:: Debugging programs that use a different
6758 character set than GDB does
6759 * Caching Remote Data:: Data caching for remote targets
6760 * Searching Memory:: Searching memory for a sequence of bytes
6764 @section Expressions
6767 @code{print} and many other @value{GDBN} commands accept an expression and
6768 compute its value. Any kind of constant, variable or operator defined
6769 by the programming language you are using is valid in an expression in
6770 @value{GDBN}. This includes conditional expressions, function calls,
6771 casts, and string constants. It also includes preprocessor macros, if
6772 you compiled your program to include this information; see
6775 @cindex arrays in expressions
6776 @value{GDBN} supports array constants in expressions input by
6777 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6778 you can use the command @code{print @{1, 2, 3@}} to create an array
6779 of three integers. If you pass an array to a function or assign it
6780 to a program variable, @value{GDBN} copies the array to memory that
6781 is @code{malloc}ed in the target program.
6783 Because C is so widespread, most of the expressions shown in examples in
6784 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6785 Languages}, for information on how to use expressions in other
6788 In this section, we discuss operators that you can use in @value{GDBN}
6789 expressions regardless of your programming language.
6791 @cindex casts, in expressions
6792 Casts are supported in all languages, not just in C, because it is so
6793 useful to cast a number into a pointer in order to examine a structure
6794 at that address in memory.
6795 @c FIXME: casts supported---Mod2 true?
6797 @value{GDBN} supports these operators, in addition to those common
6798 to programming languages:
6802 @samp{@@} is a binary operator for treating parts of memory as arrays.
6803 @xref{Arrays, ,Artificial Arrays}, for more information.
6806 @samp{::} allows you to specify a variable in terms of the file or
6807 function where it is defined. @xref{Variables, ,Program Variables}.
6809 @cindex @{@var{type}@}
6810 @cindex type casting memory
6811 @cindex memory, viewing as typed object
6812 @cindex casts, to view memory
6813 @item @{@var{type}@} @var{addr}
6814 Refers to an object of type @var{type} stored at address @var{addr} in
6815 memory. @var{addr} may be any expression whose value is an integer or
6816 pointer (but parentheses are required around binary operators, just as in
6817 a cast). This construct is allowed regardless of what kind of data is
6818 normally supposed to reside at @var{addr}.
6821 @node Ambiguous Expressions
6822 @section Ambiguous Expressions
6823 @cindex ambiguous expressions
6825 Expressions can sometimes contain some ambiguous elements. For instance,
6826 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6827 a single function name to be defined several times, for application in
6828 different contexts. This is called @dfn{overloading}. Another example
6829 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6830 templates and is typically instantiated several times, resulting in
6831 the same function name being defined in different contexts.
6833 In some cases and depending on the language, it is possible to adjust
6834 the expression to remove the ambiguity. For instance in C@t{++}, you
6835 can specify the signature of the function you want to break on, as in
6836 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6837 qualified name of your function often makes the expression unambiguous
6840 When an ambiguity that needs to be resolved is detected, the debugger
6841 has the capability to display a menu of numbered choices for each
6842 possibility, and then waits for the selection with the prompt @samp{>}.
6843 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6844 aborts the current command. If the command in which the expression was
6845 used allows more than one choice to be selected, the next option in the
6846 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6849 For example, the following session excerpt shows an attempt to set a
6850 breakpoint at the overloaded symbol @code{String::after}.
6851 We choose three particular definitions of that function name:
6853 @c FIXME! This is likely to change to show arg type lists, at least
6856 (@value{GDBP}) b String::after
6859 [2] file:String.cc; line number:867
6860 [3] file:String.cc; line number:860
6861 [4] file:String.cc; line number:875
6862 [5] file:String.cc; line number:853
6863 [6] file:String.cc; line number:846
6864 [7] file:String.cc; line number:735
6866 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6867 Breakpoint 2 at 0xb344: file String.cc, line 875.
6868 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6869 Multiple breakpoints were set.
6870 Use the "delete" command to delete unwanted
6877 @kindex set multiple-symbols
6878 @item set multiple-symbols @var{mode}
6879 @cindex multiple-symbols menu
6881 This option allows you to adjust the debugger behavior when an expression
6884 By default, @var{mode} is set to @code{all}. If the command with which
6885 the expression is used allows more than one choice, then @value{GDBN}
6886 automatically selects all possible choices. For instance, inserting
6887 a breakpoint on a function using an ambiguous name results in a breakpoint
6888 inserted on each possible match. However, if a unique choice must be made,
6889 then @value{GDBN} uses the menu to help you disambiguate the expression.
6890 For instance, printing the address of an overloaded function will result
6891 in the use of the menu.
6893 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6894 when an ambiguity is detected.
6896 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6897 an error due to the ambiguity and the command is aborted.
6899 @kindex show multiple-symbols
6900 @item show multiple-symbols
6901 Show the current value of the @code{multiple-symbols} setting.
6905 @section Program Variables
6907 The most common kind of expression to use is the name of a variable
6910 Variables in expressions are understood in the selected stack frame
6911 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6915 global (or file-static)
6922 visible according to the scope rules of the
6923 programming language from the point of execution in that frame
6926 @noindent This means that in the function
6941 you can examine and use the variable @code{a} whenever your program is
6942 executing within the function @code{foo}, but you can only use or
6943 examine the variable @code{b} while your program is executing inside
6944 the block where @code{b} is declared.
6946 @cindex variable name conflict
6947 There is an exception: you can refer to a variable or function whose
6948 scope is a single source file even if the current execution point is not
6949 in this file. But it is possible to have more than one such variable or
6950 function with the same name (in different source files). If that
6951 happens, referring to that name has unpredictable effects. If you wish,
6952 you can specify a static variable in a particular function or file,
6953 using the colon-colon (@code{::}) notation:
6955 @cindex colon-colon, context for variables/functions
6957 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6958 @cindex @code{::}, context for variables/functions
6961 @var{file}::@var{variable}
6962 @var{function}::@var{variable}
6966 Here @var{file} or @var{function} is the name of the context for the
6967 static @var{variable}. In the case of file names, you can use quotes to
6968 make sure @value{GDBN} parses the file name as a single word---for example,
6969 to print a global value of @code{x} defined in @file{f2.c}:
6972 (@value{GDBP}) p 'f2.c'::x
6975 @cindex C@t{++} scope resolution
6976 This use of @samp{::} is very rarely in conflict with the very similar
6977 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6978 scope resolution operator in @value{GDBN} expressions.
6979 @c FIXME: Um, so what happens in one of those rare cases where it's in
6982 @cindex wrong values
6983 @cindex variable values, wrong
6984 @cindex function entry/exit, wrong values of variables
6985 @cindex optimized code, wrong values of variables
6987 @emph{Warning:} Occasionally, a local variable may appear to have the
6988 wrong value at certain points in a function---just after entry to a new
6989 scope, and just before exit.
6991 You may see this problem when you are stepping by machine instructions.
6992 This is because, on most machines, it takes more than one instruction to
6993 set up a stack frame (including local variable definitions); if you are
6994 stepping by machine instructions, variables may appear to have the wrong
6995 values until the stack frame is completely built. On exit, it usually
6996 also takes more than one machine instruction to destroy a stack frame;
6997 after you begin stepping through that group of instructions, local
6998 variable definitions may be gone.
7000 This may also happen when the compiler does significant optimizations.
7001 To be sure of always seeing accurate values, turn off all optimization
7004 @cindex ``No symbol "foo" in current context''
7005 Another possible effect of compiler optimizations is to optimize
7006 unused variables out of existence, or assign variables to registers (as
7007 opposed to memory addresses). Depending on the support for such cases
7008 offered by the debug info format used by the compiler, @value{GDBN}
7009 might not be able to display values for such local variables. If that
7010 happens, @value{GDBN} will print a message like this:
7013 No symbol "foo" in current context.
7016 To solve such problems, either recompile without optimizations, or use a
7017 different debug info format, if the compiler supports several such
7018 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7019 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7020 produces debug info in a format that is superior to formats such as
7021 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7022 an effective form for debug info. @xref{Debugging Options,,Options
7023 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7024 Compiler Collection (GCC)}.
7025 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7026 that are best suited to C@t{++} programs.
7028 If you ask to print an object whose contents are unknown to
7029 @value{GDBN}, e.g., because its data type is not completely specified
7030 by the debug information, @value{GDBN} will say @samp{<incomplete
7031 type>}. @xref{Symbols, incomplete type}, for more about this.
7033 Strings are identified as arrays of @code{char} values without specified
7034 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7035 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7036 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7037 defines literal string type @code{"char"} as @code{char} without a sign.
7042 signed char var1[] = "A";
7045 You get during debugging
7050 $2 = @{65 'A', 0 '\0'@}
7054 @section Artificial Arrays
7056 @cindex artificial array
7058 @kindex @@@r{, referencing memory as an array}
7059 It is often useful to print out several successive objects of the
7060 same type in memory; a section of an array, or an array of
7061 dynamically determined size for which only a pointer exists in the
7064 You can do this by referring to a contiguous span of memory as an
7065 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7066 operand of @samp{@@} should be the first element of the desired array
7067 and be an individual object. The right operand should be the desired length
7068 of the array. The result is an array value whose elements are all of
7069 the type of the left argument. The first element is actually the left
7070 argument; the second element comes from bytes of memory immediately
7071 following those that hold the first element, and so on. Here is an
7072 example. If a program says
7075 int *array = (int *) malloc (len * sizeof (int));
7079 you can print the contents of @code{array} with
7085 The left operand of @samp{@@} must reside in memory. Array values made
7086 with @samp{@@} in this way behave just like other arrays in terms of
7087 subscripting, and are coerced to pointers when used in expressions.
7088 Artificial arrays most often appear in expressions via the value history
7089 (@pxref{Value History, ,Value History}), after printing one out.
7091 Another way to create an artificial array is to use a cast.
7092 This re-interprets a value as if it were an array.
7093 The value need not be in memory:
7095 (@value{GDBP}) p/x (short[2])0x12345678
7096 $1 = @{0x1234, 0x5678@}
7099 As a convenience, if you leave the array length out (as in
7100 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7101 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7103 (@value{GDBP}) p/x (short[])0x12345678
7104 $2 = @{0x1234, 0x5678@}
7107 Sometimes the artificial array mechanism is not quite enough; in
7108 moderately complex data structures, the elements of interest may not
7109 actually be adjacent---for example, if you are interested in the values
7110 of pointers in an array. One useful work-around in this situation is
7111 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7112 Variables}) as a counter in an expression that prints the first
7113 interesting value, and then repeat that expression via @key{RET}. For
7114 instance, suppose you have an array @code{dtab} of pointers to
7115 structures, and you are interested in the values of a field @code{fv}
7116 in each structure. Here is an example of what you might type:
7126 @node Output Formats
7127 @section Output Formats
7129 @cindex formatted output
7130 @cindex output formats
7131 By default, @value{GDBN} prints a value according to its data type. Sometimes
7132 this is not what you want. For example, you might want to print a number
7133 in hex, or a pointer in decimal. Or you might want to view data in memory
7134 at a certain address as a character string or as an instruction. To do
7135 these things, specify an @dfn{output format} when you print a value.
7137 The simplest use of output formats is to say how to print a value
7138 already computed. This is done by starting the arguments of the
7139 @code{print} command with a slash and a format letter. The format
7140 letters supported are:
7144 Regard the bits of the value as an integer, and print the integer in
7148 Print as integer in signed decimal.
7151 Print as integer in unsigned decimal.
7154 Print as integer in octal.
7157 Print as integer in binary. The letter @samp{t} stands for ``two''.
7158 @footnote{@samp{b} cannot be used because these format letters are also
7159 used with the @code{x} command, where @samp{b} stands for ``byte'';
7160 see @ref{Memory,,Examining Memory}.}
7163 @cindex unknown address, locating
7164 @cindex locate address
7165 Print as an address, both absolute in hexadecimal and as an offset from
7166 the nearest preceding symbol. You can use this format used to discover
7167 where (in what function) an unknown address is located:
7170 (@value{GDBP}) p/a 0x54320
7171 $3 = 0x54320 <_initialize_vx+396>
7175 The command @code{info symbol 0x54320} yields similar results.
7176 @xref{Symbols, info symbol}.
7179 Regard as an integer and print it as a character constant. This
7180 prints both the numerical value and its character representation. The
7181 character representation is replaced with the octal escape @samp{\nnn}
7182 for characters outside the 7-bit @sc{ascii} range.
7184 Without this format, @value{GDBN} displays @code{char},
7185 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7186 constants. Single-byte members of vectors are displayed as integer
7190 Regard the bits of the value as a floating point number and print
7191 using typical floating point syntax.
7194 @cindex printing strings
7195 @cindex printing byte arrays
7196 Regard as a string, if possible. With this format, pointers to single-byte
7197 data are displayed as null-terminated strings and arrays of single-byte data
7198 are displayed as fixed-length strings. Other values are displayed in their
7201 Without this format, @value{GDBN} displays pointers to and arrays of
7202 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7203 strings. Single-byte members of a vector are displayed as an integer
7207 @cindex raw printing
7208 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7209 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7210 Printing}). This typically results in a higher-level display of the
7211 value's contents. The @samp{r} format bypasses any Python
7212 pretty-printer which might exist.
7215 For example, to print the program counter in hex (@pxref{Registers}), type
7222 Note that no space is required before the slash; this is because command
7223 names in @value{GDBN} cannot contain a slash.
7225 To reprint the last value in the value history with a different format,
7226 you can use the @code{print} command with just a format and no
7227 expression. For example, @samp{p/x} reprints the last value in hex.
7230 @section Examining Memory
7232 You can use the command @code{x} (for ``examine'') to examine memory in
7233 any of several formats, independently of your program's data types.
7235 @cindex examining memory
7237 @kindex x @r{(examine memory)}
7238 @item x/@var{nfu} @var{addr}
7241 Use the @code{x} command to examine memory.
7244 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7245 much memory to display and how to format it; @var{addr} is an
7246 expression giving the address where you want to start displaying memory.
7247 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7248 Several commands set convenient defaults for @var{addr}.
7251 @item @var{n}, the repeat count
7252 The repeat count is a decimal integer; the default is 1. It specifies
7253 how much memory (counting by units @var{u}) to display.
7254 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7257 @item @var{f}, the display format
7258 The display format is one of the formats used by @code{print}
7259 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7260 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7261 The default is @samp{x} (hexadecimal) initially. The default changes
7262 each time you use either @code{x} or @code{print}.
7264 @item @var{u}, the unit size
7265 The unit size is any of
7271 Halfwords (two bytes).
7273 Words (four bytes). This is the initial default.
7275 Giant words (eight bytes).
7278 Each time you specify a unit size with @code{x}, that size becomes the
7279 default unit the next time you use @code{x}. For the @samp{i} format,
7280 the unit size is ignored and is normally not written. For the @samp{s} format,
7281 the unit size defaults to @samp{b}, unless it is explicitly given.
7282 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7283 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7284 Note that the results depend on the programming language of the
7285 current compilation unit. If the language is C, the @samp{s}
7286 modifier will use the UTF-16 encoding while @samp{w} will use
7287 UTF-32. The encoding is set by the programming language and cannot
7290 @item @var{addr}, starting display address
7291 @var{addr} is the address where you want @value{GDBN} to begin displaying
7292 memory. The expression need not have a pointer value (though it may);
7293 it is always interpreted as an integer address of a byte of memory.
7294 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7295 @var{addr} is usually just after the last address examined---but several
7296 other commands also set the default address: @code{info breakpoints} (to
7297 the address of the last breakpoint listed), @code{info line} (to the
7298 starting address of a line), and @code{print} (if you use it to display
7299 a value from memory).
7302 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7303 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7304 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7305 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7306 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7308 Since the letters indicating unit sizes are all distinct from the
7309 letters specifying output formats, you do not have to remember whether
7310 unit size or format comes first; either order works. The output
7311 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7312 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7314 Even though the unit size @var{u} is ignored for the formats @samp{s}
7315 and @samp{i}, you might still want to use a count @var{n}; for example,
7316 @samp{3i} specifies that you want to see three machine instructions,
7317 including any operands. For convenience, especially when used with
7318 the @code{display} command, the @samp{i} format also prints branch delay
7319 slot instructions, if any, beyond the count specified, which immediately
7320 follow the last instruction that is within the count. The command
7321 @code{disassemble} gives an alternative way of inspecting machine
7322 instructions; see @ref{Machine Code,,Source and Machine Code}.
7324 All the defaults for the arguments to @code{x} are designed to make it
7325 easy to continue scanning memory with minimal specifications each time
7326 you use @code{x}. For example, after you have inspected three machine
7327 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7328 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7329 the repeat count @var{n} is used again; the other arguments default as
7330 for successive uses of @code{x}.
7332 When examining machine instructions, the instruction at current program
7333 counter is shown with a @code{=>} marker. For example:
7336 (@value{GDBP}) x/5i $pc-6
7337 0x804837f <main+11>: mov %esp,%ebp
7338 0x8048381 <main+13>: push %ecx
7339 0x8048382 <main+14>: sub $0x4,%esp
7340 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7341 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7344 @cindex @code{$_}, @code{$__}, and value history
7345 The addresses and contents printed by the @code{x} command are not saved
7346 in the value history because there is often too much of them and they
7347 would get in the way. Instead, @value{GDBN} makes these values available for
7348 subsequent use in expressions as values of the convenience variables
7349 @code{$_} and @code{$__}. After an @code{x} command, the last address
7350 examined is available for use in expressions in the convenience variable
7351 @code{$_}. The contents of that address, as examined, are available in
7352 the convenience variable @code{$__}.
7354 If the @code{x} command has a repeat count, the address and contents saved
7355 are from the last memory unit printed; this is not the same as the last
7356 address printed if several units were printed on the last line of output.
7358 @cindex remote memory comparison
7359 @cindex verify remote memory image
7360 When you are debugging a program running on a remote target machine
7361 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7362 remote machine's memory against the executable file you downloaded to
7363 the target. The @code{compare-sections} command is provided for such
7367 @kindex compare-sections
7368 @item compare-sections @r{[}@var{section-name}@r{]}
7369 Compare the data of a loadable section @var{section-name} in the
7370 executable file of the program being debugged with the same section in
7371 the remote machine's memory, and report any mismatches. With no
7372 arguments, compares all loadable sections. This command's
7373 availability depends on the target's support for the @code{"qCRC"}
7378 @section Automatic Display
7379 @cindex automatic display
7380 @cindex display of expressions
7382 If you find that you want to print the value of an expression frequently
7383 (to see how it changes), you might want to add it to the @dfn{automatic
7384 display list} so that @value{GDBN} prints its value each time your program stops.
7385 Each expression added to the list is given a number to identify it;
7386 to remove an expression from the list, you specify that number.
7387 The automatic display looks like this:
7391 3: bar[5] = (struct hack *) 0x3804
7395 This display shows item numbers, expressions and their current values. As with
7396 displays you request manually using @code{x} or @code{print}, you can
7397 specify the output format you prefer; in fact, @code{display} decides
7398 whether to use @code{print} or @code{x} depending your format
7399 specification---it uses @code{x} if you specify either the @samp{i}
7400 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7404 @item display @var{expr}
7405 Add the expression @var{expr} to the list of expressions to display
7406 each time your program stops. @xref{Expressions, ,Expressions}.
7408 @code{display} does not repeat if you press @key{RET} again after using it.
7410 @item display/@var{fmt} @var{expr}
7411 For @var{fmt} specifying only a display format and not a size or
7412 count, add the expression @var{expr} to the auto-display list but
7413 arrange to display it each time in the specified format @var{fmt}.
7414 @xref{Output Formats,,Output Formats}.
7416 @item display/@var{fmt} @var{addr}
7417 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7418 number of units, add the expression @var{addr} as a memory address to
7419 be examined each time your program stops. Examining means in effect
7420 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7423 For example, @samp{display/i $pc} can be helpful, to see the machine
7424 instruction about to be executed each time execution stops (@samp{$pc}
7425 is a common name for the program counter; @pxref{Registers, ,Registers}).
7428 @kindex delete display
7430 @item undisplay @var{dnums}@dots{}
7431 @itemx delete display @var{dnums}@dots{}
7432 Remove item numbers @var{dnums} from the list of expressions to display.
7434 @code{undisplay} does not repeat if you press @key{RET} after using it.
7435 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7437 @kindex disable display
7438 @item disable display @var{dnums}@dots{}
7439 Disable the display of item numbers @var{dnums}. A disabled display
7440 item is not printed automatically, but is not forgotten. It may be
7441 enabled again later.
7443 @kindex enable display
7444 @item enable display @var{dnums}@dots{}
7445 Enable display of item numbers @var{dnums}. It becomes effective once
7446 again in auto display of its expression, until you specify otherwise.
7449 Display the current values of the expressions on the list, just as is
7450 done when your program stops.
7452 @kindex info display
7454 Print the list of expressions previously set up to display
7455 automatically, each one with its item number, but without showing the
7456 values. This includes disabled expressions, which are marked as such.
7457 It also includes expressions which would not be displayed right now
7458 because they refer to automatic variables not currently available.
7461 @cindex display disabled out of scope
7462 If a display expression refers to local variables, then it does not make
7463 sense outside the lexical context for which it was set up. Such an
7464 expression is disabled when execution enters a context where one of its
7465 variables is not defined. For example, if you give the command
7466 @code{display last_char} while inside a function with an argument
7467 @code{last_char}, @value{GDBN} displays this argument while your program
7468 continues to stop inside that function. When it stops elsewhere---where
7469 there is no variable @code{last_char}---the display is disabled
7470 automatically. The next time your program stops where @code{last_char}
7471 is meaningful, you can enable the display expression once again.
7473 @node Print Settings
7474 @section Print Settings
7476 @cindex format options
7477 @cindex print settings
7478 @value{GDBN} provides the following ways to control how arrays, structures,
7479 and symbols are printed.
7482 These settings are useful for debugging programs in any language:
7486 @item set print address
7487 @itemx set print address on
7488 @cindex print/don't print memory addresses
7489 @value{GDBN} prints memory addresses showing the location of stack
7490 traces, structure values, pointer values, breakpoints, and so forth,
7491 even when it also displays the contents of those addresses. The default
7492 is @code{on}. For example, this is what a stack frame display looks like with
7493 @code{set print address on}:
7498 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7500 530 if (lquote != def_lquote)
7504 @item set print address off
7505 Do not print addresses when displaying their contents. For example,
7506 this is the same stack frame displayed with @code{set print address off}:
7510 (@value{GDBP}) set print addr off
7512 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7513 530 if (lquote != def_lquote)
7517 You can use @samp{set print address off} to eliminate all machine
7518 dependent displays from the @value{GDBN} interface. For example, with
7519 @code{print address off}, you should get the same text for backtraces on
7520 all machines---whether or not they involve pointer arguments.
7523 @item show print address
7524 Show whether or not addresses are to be printed.
7527 When @value{GDBN} prints a symbolic address, it normally prints the
7528 closest earlier symbol plus an offset. If that symbol does not uniquely
7529 identify the address (for example, it is a name whose scope is a single
7530 source file), you may need to clarify. One way to do this is with
7531 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7532 you can set @value{GDBN} to print the source file and line number when
7533 it prints a symbolic address:
7536 @item set print symbol-filename on
7537 @cindex source file and line of a symbol
7538 @cindex symbol, source file and line
7539 Tell @value{GDBN} to print the source file name and line number of a
7540 symbol in the symbolic form of an address.
7542 @item set print symbol-filename off
7543 Do not print source file name and line number of a symbol. This is the
7546 @item show print symbol-filename
7547 Show whether or not @value{GDBN} will print the source file name and
7548 line number of a symbol in the symbolic form of an address.
7551 Another situation where it is helpful to show symbol filenames and line
7552 numbers is when disassembling code; @value{GDBN} shows you the line
7553 number and source file that corresponds to each instruction.
7555 Also, you may wish to see the symbolic form only if the address being
7556 printed is reasonably close to the closest earlier symbol:
7559 @item set print max-symbolic-offset @var{max-offset}
7560 @cindex maximum value for offset of closest symbol
7561 Tell @value{GDBN} to only display the symbolic form of an address if the
7562 offset between the closest earlier symbol and the address is less than
7563 @var{max-offset}. The default is 0, which tells @value{GDBN}
7564 to always print the symbolic form of an address if any symbol precedes it.
7566 @item show print max-symbolic-offset
7567 Ask how large the maximum offset is that @value{GDBN} prints in a
7571 @cindex wild pointer, interpreting
7572 @cindex pointer, finding referent
7573 If you have a pointer and you are not sure where it points, try
7574 @samp{set print symbol-filename on}. Then you can determine the name
7575 and source file location of the variable where it points, using
7576 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7577 For example, here @value{GDBN} shows that a variable @code{ptt} points
7578 at another variable @code{t}, defined in @file{hi2.c}:
7581 (@value{GDBP}) set print symbol-filename on
7582 (@value{GDBP}) p/a ptt
7583 $4 = 0xe008 <t in hi2.c>
7587 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7588 does not show the symbol name and filename of the referent, even with
7589 the appropriate @code{set print} options turned on.
7592 Other settings control how different kinds of objects are printed:
7595 @item set print array
7596 @itemx set print array on
7597 @cindex pretty print arrays
7598 Pretty print arrays. This format is more convenient to read,
7599 but uses more space. The default is off.
7601 @item set print array off
7602 Return to compressed format for arrays.
7604 @item show print array
7605 Show whether compressed or pretty format is selected for displaying
7608 @cindex print array indexes
7609 @item set print array-indexes
7610 @itemx set print array-indexes on
7611 Print the index of each element when displaying arrays. May be more
7612 convenient to locate a given element in the array or quickly find the
7613 index of a given element in that printed array. The default is off.
7615 @item set print array-indexes off
7616 Stop printing element indexes when displaying arrays.
7618 @item show print array-indexes
7619 Show whether the index of each element is printed when displaying
7622 @item set print elements @var{number-of-elements}
7623 @cindex number of array elements to print
7624 @cindex limit on number of printed array elements
7625 Set a limit on how many elements of an array @value{GDBN} will print.
7626 If @value{GDBN} is printing a large array, it stops printing after it has
7627 printed the number of elements set by the @code{set print elements} command.
7628 This limit also applies to the display of strings.
7629 When @value{GDBN} starts, this limit is set to 200.
7630 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7632 @item show print elements
7633 Display the number of elements of a large array that @value{GDBN} will print.
7634 If the number is 0, then the printing is unlimited.
7636 @item set print frame-arguments @var{value}
7637 @kindex set print frame-arguments
7638 @cindex printing frame argument values
7639 @cindex print all frame argument values
7640 @cindex print frame argument values for scalars only
7641 @cindex do not print frame argument values
7642 This command allows to control how the values of arguments are printed
7643 when the debugger prints a frame (@pxref{Frames}). The possible
7648 The values of all arguments are printed.
7651 Print the value of an argument only if it is a scalar. The value of more
7652 complex arguments such as arrays, structures, unions, etc, is replaced
7653 by @code{@dots{}}. This is the default. Here is an example where
7654 only scalar arguments are shown:
7657 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7662 None of the argument values are printed. Instead, the value of each argument
7663 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7666 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7671 By default, only scalar arguments are printed. This command can be used
7672 to configure the debugger to print the value of all arguments, regardless
7673 of their type. However, it is often advantageous to not print the value
7674 of more complex parameters. For instance, it reduces the amount of
7675 information printed in each frame, making the backtrace more readable.
7676 Also, it improves performance when displaying Ada frames, because
7677 the computation of large arguments can sometimes be CPU-intensive,
7678 especially in large applications. Setting @code{print frame-arguments}
7679 to @code{scalars} (the default) or @code{none} avoids this computation,
7680 thus speeding up the display of each Ada frame.
7682 @item show print frame-arguments
7683 Show how the value of arguments should be displayed when printing a frame.
7685 @item set print repeats
7686 @cindex repeated array elements
7687 Set the threshold for suppressing display of repeated array
7688 elements. When the number of consecutive identical elements of an
7689 array exceeds the threshold, @value{GDBN} prints the string
7690 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7691 identical repetitions, instead of displaying the identical elements
7692 themselves. Setting the threshold to zero will cause all elements to
7693 be individually printed. The default threshold is 10.
7695 @item show print repeats
7696 Display the current threshold for printing repeated identical
7699 @item set print null-stop
7700 @cindex @sc{null} elements in arrays
7701 Cause @value{GDBN} to stop printing the characters of an array when the first
7702 @sc{null} is encountered. This is useful when large arrays actually
7703 contain only short strings.
7706 @item show print null-stop
7707 Show whether @value{GDBN} stops printing an array on the first
7708 @sc{null} character.
7710 @item set print pretty on
7711 @cindex print structures in indented form
7712 @cindex indentation in structure display
7713 Cause @value{GDBN} to print structures in an indented format with one member
7714 per line, like this:
7729 @item set print pretty off
7730 Cause @value{GDBN} to print structures in a compact format, like this:
7734 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7735 meat = 0x54 "Pork"@}
7740 This is the default format.
7742 @item show print pretty
7743 Show which format @value{GDBN} is using to print structures.
7745 @item set print sevenbit-strings on
7746 @cindex eight-bit characters in strings
7747 @cindex octal escapes in strings
7748 Print using only seven-bit characters; if this option is set,
7749 @value{GDBN} displays any eight-bit characters (in strings or
7750 character values) using the notation @code{\}@var{nnn}. This setting is
7751 best if you are working in English (@sc{ascii}) and you use the
7752 high-order bit of characters as a marker or ``meta'' bit.
7754 @item set print sevenbit-strings off
7755 Print full eight-bit characters. This allows the use of more
7756 international character sets, and is the default.
7758 @item show print sevenbit-strings
7759 Show whether or not @value{GDBN} is printing only seven-bit characters.
7761 @item set print union on
7762 @cindex unions in structures, printing
7763 Tell @value{GDBN} to print unions which are contained in structures
7764 and other unions. This is the default setting.
7766 @item set print union off
7767 Tell @value{GDBN} not to print unions which are contained in
7768 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7771 @item show print union
7772 Ask @value{GDBN} whether or not it will print unions which are contained in
7773 structures and other unions.
7775 For example, given the declarations
7778 typedef enum @{Tree, Bug@} Species;
7779 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7780 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7791 struct thing foo = @{Tree, @{Acorn@}@};
7795 with @code{set print union on} in effect @samp{p foo} would print
7798 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7802 and with @code{set print union off} in effect it would print
7805 $1 = @{it = Tree, form = @{...@}@}
7809 @code{set print union} affects programs written in C-like languages
7815 These settings are of interest when debugging C@t{++} programs:
7818 @cindex demangling C@t{++} names
7819 @item set print demangle
7820 @itemx set print demangle on
7821 Print C@t{++} names in their source form rather than in the encoded
7822 (``mangled'') form passed to the assembler and linker for type-safe
7823 linkage. The default is on.
7825 @item show print demangle
7826 Show whether C@t{++} names are printed in mangled or demangled form.
7828 @item set print asm-demangle
7829 @itemx set print asm-demangle on
7830 Print C@t{++} names in their source form rather than their mangled form, even
7831 in assembler code printouts such as instruction disassemblies.
7834 @item show print asm-demangle
7835 Show whether C@t{++} names in assembly listings are printed in mangled
7838 @cindex C@t{++} symbol decoding style
7839 @cindex symbol decoding style, C@t{++}
7840 @kindex set demangle-style
7841 @item set demangle-style @var{style}
7842 Choose among several encoding schemes used by different compilers to
7843 represent C@t{++} names. The choices for @var{style} are currently:
7847 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7850 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7851 This is the default.
7854 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7857 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7860 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7861 @strong{Warning:} this setting alone is not sufficient to allow
7862 debugging @code{cfront}-generated executables. @value{GDBN} would
7863 require further enhancement to permit that.
7866 If you omit @var{style}, you will see a list of possible formats.
7868 @item show demangle-style
7869 Display the encoding style currently in use for decoding C@t{++} symbols.
7871 @item set print object
7872 @itemx set print object on
7873 @cindex derived type of an object, printing
7874 @cindex display derived types
7875 When displaying a pointer to an object, identify the @emph{actual}
7876 (derived) type of the object rather than the @emph{declared} type, using
7877 the virtual function table.
7879 @item set print object off
7880 Display only the declared type of objects, without reference to the
7881 virtual function table. This is the default setting.
7883 @item show print object
7884 Show whether actual, or declared, object types are displayed.
7886 @item set print static-members
7887 @itemx set print static-members on
7888 @cindex static members of C@t{++} objects
7889 Print static members when displaying a C@t{++} object. The default is on.
7891 @item set print static-members off
7892 Do not print static members when displaying a C@t{++} object.
7894 @item show print static-members
7895 Show whether C@t{++} static members are printed or not.
7897 @item set print pascal_static-members
7898 @itemx set print pascal_static-members on
7899 @cindex static members of Pascal objects
7900 @cindex Pascal objects, static members display
7901 Print static members when displaying a Pascal object. The default is on.
7903 @item set print pascal_static-members off
7904 Do not print static members when displaying a Pascal object.
7906 @item show print pascal_static-members
7907 Show whether Pascal static members are printed or not.
7909 @c These don't work with HP ANSI C++ yet.
7910 @item set print vtbl
7911 @itemx set print vtbl on
7912 @cindex pretty print C@t{++} virtual function tables
7913 @cindex virtual functions (C@t{++}) display
7914 @cindex VTBL display
7915 Pretty print C@t{++} virtual function tables. The default is off.
7916 (The @code{vtbl} commands do not work on programs compiled with the HP
7917 ANSI C@t{++} compiler (@code{aCC}).)
7919 @item set print vtbl off
7920 Do not pretty print C@t{++} virtual function tables.
7922 @item show print vtbl
7923 Show whether C@t{++} virtual function tables are pretty printed, or not.
7926 @node Pretty Printing
7927 @section Pretty Printing
7929 @value{GDBN} provides a mechanism to allow pretty-printing of values using
7930 Python code. It greatly simplifies the display of complex objects. This
7931 mechanism works for both MI and the CLI.
7933 For example, here is how a C@t{++} @code{std::string} looks without a
7937 (@value{GDBP}) print s
7939 static npos = 4294967295,
7941 <std::allocator<char>> = @{
7942 <__gnu_cxx::new_allocator<char>> = @{
7943 <No data fields>@}, <No data fields>
7945 members of std::basic_string<char, std::char_traits<char>,
7946 std::allocator<char> >::_Alloc_hider:
7947 _M_p = 0x804a014 "abcd"
7952 With a pretty-printer for @code{std::string} only the contents are printed:
7955 (@value{GDBP}) print s
7959 For implementing pretty printers for new types you should read the Python API
7960 details (@pxref{Pretty Printing API}).
7963 @section Value History
7965 @cindex value history
7966 @cindex history of values printed by @value{GDBN}
7967 Values printed by the @code{print} command are saved in the @value{GDBN}
7968 @dfn{value history}. This allows you to refer to them in other expressions.
7969 Values are kept until the symbol table is re-read or discarded
7970 (for example with the @code{file} or @code{symbol-file} commands).
7971 When the symbol table changes, the value history is discarded,
7972 since the values may contain pointers back to the types defined in the
7977 @cindex history number
7978 The values printed are given @dfn{history numbers} by which you can
7979 refer to them. These are successive integers starting with one.
7980 @code{print} shows you the history number assigned to a value by
7981 printing @samp{$@var{num} = } before the value; here @var{num} is the
7984 To refer to any previous value, use @samp{$} followed by the value's
7985 history number. The way @code{print} labels its output is designed to
7986 remind you of this. Just @code{$} refers to the most recent value in
7987 the history, and @code{$$} refers to the value before that.
7988 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7989 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7990 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7992 For example, suppose you have just printed a pointer to a structure and
7993 want to see the contents of the structure. It suffices to type
7999 If you have a chain of structures where the component @code{next} points
8000 to the next one, you can print the contents of the next one with this:
8007 You can print successive links in the chain by repeating this
8008 command---which you can do by just typing @key{RET}.
8010 Note that the history records values, not expressions. If the value of
8011 @code{x} is 4 and you type these commands:
8019 then the value recorded in the value history by the @code{print} command
8020 remains 4 even though the value of @code{x} has changed.
8025 Print the last ten values in the value history, with their item numbers.
8026 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8027 values} does not change the history.
8029 @item show values @var{n}
8030 Print ten history values centered on history item number @var{n}.
8033 Print ten history values just after the values last printed. If no more
8034 values are available, @code{show values +} produces no display.
8037 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8038 same effect as @samp{show values +}.
8040 @node Convenience Vars
8041 @section Convenience Variables
8043 @cindex convenience variables
8044 @cindex user-defined variables
8045 @value{GDBN} provides @dfn{convenience variables} that you can use within
8046 @value{GDBN} to hold on to a value and refer to it later. These variables
8047 exist entirely within @value{GDBN}; they are not part of your program, and
8048 setting a convenience variable has no direct effect on further execution
8049 of your program. That is why you can use them freely.
8051 Convenience variables are prefixed with @samp{$}. Any name preceded by
8052 @samp{$} can be used for a convenience variable, unless it is one of
8053 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8054 (Value history references, in contrast, are @emph{numbers} preceded
8055 by @samp{$}. @xref{Value History, ,Value History}.)
8057 You can save a value in a convenience variable with an assignment
8058 expression, just as you would set a variable in your program.
8062 set $foo = *object_ptr
8066 would save in @code{$foo} the value contained in the object pointed to by
8069 Using a convenience variable for the first time creates it, but its
8070 value is @code{void} until you assign a new value. You can alter the
8071 value with another assignment at any time.
8073 Convenience variables have no fixed types. You can assign a convenience
8074 variable any type of value, including structures and arrays, even if
8075 that variable already has a value of a different type. The convenience
8076 variable, when used as an expression, has the type of its current value.
8079 @kindex show convenience
8080 @cindex show all user variables
8081 @item show convenience
8082 Print a list of convenience variables used so far, and their values.
8083 Abbreviated @code{show conv}.
8085 @kindex init-if-undefined
8086 @cindex convenience variables, initializing
8087 @item init-if-undefined $@var{variable} = @var{expression}
8088 Set a convenience variable if it has not already been set. This is useful
8089 for user-defined commands that keep some state. It is similar, in concept,
8090 to using local static variables with initializers in C (except that
8091 convenience variables are global). It can also be used to allow users to
8092 override default values used in a command script.
8094 If the variable is already defined then the expression is not evaluated so
8095 any side-effects do not occur.
8098 One of the ways to use a convenience variable is as a counter to be
8099 incremented or a pointer to be advanced. For example, to print
8100 a field from successive elements of an array of structures:
8104 print bar[$i++]->contents
8108 Repeat that command by typing @key{RET}.
8110 Some convenience variables are created automatically by @value{GDBN} and given
8111 values likely to be useful.
8114 @vindex $_@r{, convenience variable}
8116 The variable @code{$_} is automatically set by the @code{x} command to
8117 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8118 commands which provide a default address for @code{x} to examine also
8119 set @code{$_} to that address; these commands include @code{info line}
8120 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8121 except when set by the @code{x} command, in which case it is a pointer
8122 to the type of @code{$__}.
8124 @vindex $__@r{, convenience variable}
8126 The variable @code{$__} is automatically set by the @code{x} command
8127 to the value found in the last address examined. Its type is chosen
8128 to match the format in which the data was printed.
8131 @vindex $_exitcode@r{, convenience variable}
8132 The variable @code{$_exitcode} is automatically set to the exit code when
8133 the program being debugged terminates.
8136 @vindex $_siginfo@r{, convenience variable}
8137 The variable @code{$_siginfo} contains extra signal information
8138 (@pxref{extra signal information}). Note that @code{$_siginfo}
8139 could be empty, if the application has not yet received any signals.
8140 For example, it will be empty before you execute the @code{run} command.
8143 @vindex $_tlb@r{, convenience variable}
8144 The variable @code{$_tlb} is automatically set when debugging
8145 applications running on MS-Windows in native mode or connected to
8146 gdbserver that supports the @code{qGetTIBAddr} request.
8147 @xref{General Query Packets}.
8148 This variable contains the address of the thread information block.
8152 On HP-UX systems, if you refer to a function or variable name that
8153 begins with a dollar sign, @value{GDBN} searches for a user or system
8154 name first, before it searches for a convenience variable.
8156 @cindex convenience functions
8157 @value{GDBN} also supplies some @dfn{convenience functions}. These
8158 have a syntax similar to convenience variables. A convenience
8159 function can be used in an expression just like an ordinary function;
8160 however, a convenience function is implemented internally to
8165 @kindex help function
8166 @cindex show all convenience functions
8167 Print a list of all convenience functions.
8174 You can refer to machine register contents, in expressions, as variables
8175 with names starting with @samp{$}. The names of registers are different
8176 for each machine; use @code{info registers} to see the names used on
8180 @kindex info registers
8181 @item info registers
8182 Print the names and values of all registers except floating-point
8183 and vector registers (in the selected stack frame).
8185 @kindex info all-registers
8186 @cindex floating point registers
8187 @item info all-registers
8188 Print the names and values of all registers, including floating-point
8189 and vector registers (in the selected stack frame).
8191 @item info registers @var{regname} @dots{}
8192 Print the @dfn{relativized} value of each specified register @var{regname}.
8193 As discussed in detail below, register values are normally relative to
8194 the selected stack frame. @var{regname} may be any register name valid on
8195 the machine you are using, with or without the initial @samp{$}.
8198 @cindex stack pointer register
8199 @cindex program counter register
8200 @cindex process status register
8201 @cindex frame pointer register
8202 @cindex standard registers
8203 @value{GDBN} has four ``standard'' register names that are available (in
8204 expressions) on most machines---whenever they do not conflict with an
8205 architecture's canonical mnemonics for registers. The register names
8206 @code{$pc} and @code{$sp} are used for the program counter register and
8207 the stack pointer. @code{$fp} is used for a register that contains a
8208 pointer to the current stack frame, and @code{$ps} is used for a
8209 register that contains the processor status. For example,
8210 you could print the program counter in hex with
8217 or print the instruction to be executed next with
8224 or add four to the stack pointer@footnote{This is a way of removing
8225 one word from the stack, on machines where stacks grow downward in
8226 memory (most machines, nowadays). This assumes that the innermost
8227 stack frame is selected; setting @code{$sp} is not allowed when other
8228 stack frames are selected. To pop entire frames off the stack,
8229 regardless of machine architecture, use @code{return};
8230 see @ref{Returning, ,Returning from a Function}.} with
8236 Whenever possible, these four standard register names are available on
8237 your machine even though the machine has different canonical mnemonics,
8238 so long as there is no conflict. The @code{info registers} command
8239 shows the canonical names. For example, on the SPARC, @code{info
8240 registers} displays the processor status register as @code{$psr} but you
8241 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8242 is an alias for the @sc{eflags} register.
8244 @value{GDBN} always considers the contents of an ordinary register as an
8245 integer when the register is examined in this way. Some machines have
8246 special registers which can hold nothing but floating point; these
8247 registers are considered to have floating point values. There is no way
8248 to refer to the contents of an ordinary register as floating point value
8249 (although you can @emph{print} it as a floating point value with
8250 @samp{print/f $@var{regname}}).
8252 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8253 means that the data format in which the register contents are saved by
8254 the operating system is not the same one that your program normally
8255 sees. For example, the registers of the 68881 floating point
8256 coprocessor are always saved in ``extended'' (raw) format, but all C
8257 programs expect to work with ``double'' (virtual) format. In such
8258 cases, @value{GDBN} normally works with the virtual format only (the format
8259 that makes sense for your program), but the @code{info registers} command
8260 prints the data in both formats.
8262 @cindex SSE registers (x86)
8263 @cindex MMX registers (x86)
8264 Some machines have special registers whose contents can be interpreted
8265 in several different ways. For example, modern x86-based machines
8266 have SSE and MMX registers that can hold several values packed
8267 together in several different formats. @value{GDBN} refers to such
8268 registers in @code{struct} notation:
8271 (@value{GDBP}) print $xmm1
8273 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8274 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8275 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8276 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8277 v4_int32 = @{0, 20657912, 11, 13@},
8278 v2_int64 = @{88725056443645952, 55834574859@},
8279 uint128 = 0x0000000d0000000b013b36f800000000
8284 To set values of such registers, you need to tell @value{GDBN} which
8285 view of the register you wish to change, as if you were assigning
8286 value to a @code{struct} member:
8289 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8292 Normally, register values are relative to the selected stack frame
8293 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8294 value that the register would contain if all stack frames farther in
8295 were exited and their saved registers restored. In order to see the
8296 true contents of hardware registers, you must select the innermost
8297 frame (with @samp{frame 0}).
8299 However, @value{GDBN} must deduce where registers are saved, from the machine
8300 code generated by your compiler. If some registers are not saved, or if
8301 @value{GDBN} is unable to locate the saved registers, the selected stack
8302 frame makes no difference.
8304 @node Floating Point Hardware
8305 @section Floating Point Hardware
8306 @cindex floating point
8308 Depending on the configuration, @value{GDBN} may be able to give
8309 you more information about the status of the floating point hardware.
8314 Display hardware-dependent information about the floating
8315 point unit. The exact contents and layout vary depending on the
8316 floating point chip. Currently, @samp{info float} is supported on
8317 the ARM and x86 machines.
8321 @section Vector Unit
8324 Depending on the configuration, @value{GDBN} may be able to give you
8325 more information about the status of the vector unit.
8330 Display information about the vector unit. The exact contents and
8331 layout vary depending on the hardware.
8334 @node OS Information
8335 @section Operating System Auxiliary Information
8336 @cindex OS information
8338 @value{GDBN} provides interfaces to useful OS facilities that can help
8339 you debug your program.
8341 @cindex @code{ptrace} system call
8342 @cindex @code{struct user} contents
8343 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8344 machines), it interfaces with the inferior via the @code{ptrace}
8345 system call. The operating system creates a special sata structure,
8346 called @code{struct user}, for this interface. You can use the
8347 command @code{info udot} to display the contents of this data
8353 Display the contents of the @code{struct user} maintained by the OS
8354 kernel for the program being debugged. @value{GDBN} displays the
8355 contents of @code{struct user} as a list of hex numbers, similar to
8356 the @code{examine} command.
8359 @cindex auxiliary vector
8360 @cindex vector, auxiliary
8361 Some operating systems supply an @dfn{auxiliary vector} to programs at
8362 startup. This is akin to the arguments and environment that you
8363 specify for a program, but contains a system-dependent variety of
8364 binary values that tell system libraries important details about the
8365 hardware, operating system, and process. Each value's purpose is
8366 identified by an integer tag; the meanings are well-known but system-specific.
8367 Depending on the configuration and operating system facilities,
8368 @value{GDBN} may be able to show you this information. For remote
8369 targets, this functionality may further depend on the remote stub's
8370 support of the @samp{qXfer:auxv:read} packet, see
8371 @ref{qXfer auxiliary vector read}.
8376 Display the auxiliary vector of the inferior, which can be either a
8377 live process or a core dump file. @value{GDBN} prints each tag value
8378 numerically, and also shows names and text descriptions for recognized
8379 tags. Some values in the vector are numbers, some bit masks, and some
8380 pointers to strings or other data. @value{GDBN} displays each value in the
8381 most appropriate form for a recognized tag, and in hexadecimal for
8382 an unrecognized tag.
8385 On some targets, @value{GDBN} can access operating-system-specific information
8386 and display it to user, without interpretation. For remote targets,
8387 this functionality depends on the remote stub's support of the
8388 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8391 @kindex info os processes
8392 @item info os processes
8393 Display the list of processes on the target. For each process,
8394 @value{GDBN} prints the process identifier, the name of the user, and
8395 the command corresponding to the process.
8398 @node Memory Region Attributes
8399 @section Memory Region Attributes
8400 @cindex memory region attributes
8402 @dfn{Memory region attributes} allow you to describe special handling
8403 required by regions of your target's memory. @value{GDBN} uses
8404 attributes to determine whether to allow certain types of memory
8405 accesses; whether to use specific width accesses; and whether to cache
8406 target memory. By default the description of memory regions is
8407 fetched from the target (if the current target supports this), but the
8408 user can override the fetched regions.
8410 Defined memory regions can be individually enabled and disabled. When a
8411 memory region is disabled, @value{GDBN} uses the default attributes when
8412 accessing memory in that region. Similarly, if no memory regions have
8413 been defined, @value{GDBN} uses the default attributes when accessing
8416 When a memory region is defined, it is given a number to identify it;
8417 to enable, disable, or remove a memory region, you specify that number.
8421 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8422 Define a memory region bounded by @var{lower} and @var{upper} with
8423 attributes @var{attributes}@dots{}, and add it to the list of regions
8424 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8425 case: it is treated as the target's maximum memory address.
8426 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8429 Discard any user changes to the memory regions and use target-supplied
8430 regions, if available, or no regions if the target does not support.
8433 @item delete mem @var{nums}@dots{}
8434 Remove memory regions @var{nums}@dots{} from the list of regions
8435 monitored by @value{GDBN}.
8438 @item disable mem @var{nums}@dots{}
8439 Disable monitoring of memory regions @var{nums}@dots{}.
8440 A disabled memory region is not forgotten.
8441 It may be enabled again later.
8444 @item enable mem @var{nums}@dots{}
8445 Enable monitoring of memory regions @var{nums}@dots{}.
8449 Print a table of all defined memory regions, with the following columns
8453 @item Memory Region Number
8454 @item Enabled or Disabled.
8455 Enabled memory regions are marked with @samp{y}.
8456 Disabled memory regions are marked with @samp{n}.
8459 The address defining the inclusive lower bound of the memory region.
8462 The address defining the exclusive upper bound of the memory region.
8465 The list of attributes set for this memory region.
8470 @subsection Attributes
8472 @subsubsection Memory Access Mode
8473 The access mode attributes set whether @value{GDBN} may make read or
8474 write accesses to a memory region.
8476 While these attributes prevent @value{GDBN} from performing invalid
8477 memory accesses, they do nothing to prevent the target system, I/O DMA,
8478 etc.@: from accessing memory.
8482 Memory is read only.
8484 Memory is write only.
8486 Memory is read/write. This is the default.
8489 @subsubsection Memory Access Size
8490 The access size attribute tells @value{GDBN} to use specific sized
8491 accesses in the memory region. Often memory mapped device registers
8492 require specific sized accesses. If no access size attribute is
8493 specified, @value{GDBN} may use accesses of any size.
8497 Use 8 bit memory accesses.
8499 Use 16 bit memory accesses.
8501 Use 32 bit memory accesses.
8503 Use 64 bit memory accesses.
8506 @c @subsubsection Hardware/Software Breakpoints
8507 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8508 @c will use hardware or software breakpoints for the internal breakpoints
8509 @c used by the step, next, finish, until, etc. commands.
8513 @c Always use hardware breakpoints
8514 @c @item swbreak (default)
8517 @subsubsection Data Cache
8518 The data cache attributes set whether @value{GDBN} will cache target
8519 memory. While this generally improves performance by reducing debug
8520 protocol overhead, it can lead to incorrect results because @value{GDBN}
8521 does not know about volatile variables or memory mapped device
8526 Enable @value{GDBN} to cache target memory.
8528 Disable @value{GDBN} from caching target memory. This is the default.
8531 @subsection Memory Access Checking
8532 @value{GDBN} can be instructed to refuse accesses to memory that is
8533 not explicitly described. This can be useful if accessing such
8534 regions has undesired effects for a specific target, or to provide
8535 better error checking. The following commands control this behaviour.
8538 @kindex set mem inaccessible-by-default
8539 @item set mem inaccessible-by-default [on|off]
8540 If @code{on} is specified, make @value{GDBN} treat memory not
8541 explicitly described by the memory ranges as non-existent and refuse accesses
8542 to such memory. The checks are only performed if there's at least one
8543 memory range defined. If @code{off} is specified, make @value{GDBN}
8544 treat the memory not explicitly described by the memory ranges as RAM.
8545 The default value is @code{on}.
8546 @kindex show mem inaccessible-by-default
8547 @item show mem inaccessible-by-default
8548 Show the current handling of accesses to unknown memory.
8552 @c @subsubsection Memory Write Verification
8553 @c The memory write verification attributes set whether @value{GDBN}
8554 @c will re-reads data after each write to verify the write was successful.
8558 @c @item noverify (default)
8561 @node Dump/Restore Files
8562 @section Copy Between Memory and a File
8563 @cindex dump/restore files
8564 @cindex append data to a file
8565 @cindex dump data to a file
8566 @cindex restore data from a file
8568 You can use the commands @code{dump}, @code{append}, and
8569 @code{restore} to copy data between target memory and a file. The
8570 @code{dump} and @code{append} commands write data to a file, and the
8571 @code{restore} command reads data from a file back into the inferior's
8572 memory. Files may be in binary, Motorola S-record, Intel hex, or
8573 Tektronix Hex format; however, @value{GDBN} can only append to binary
8579 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8580 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8581 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8582 or the value of @var{expr}, to @var{filename} in the given format.
8584 The @var{format} parameter may be any one of:
8591 Motorola S-record format.
8593 Tektronix Hex format.
8596 @value{GDBN} uses the same definitions of these formats as the
8597 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8598 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8602 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8603 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8604 Append the contents of memory from @var{start_addr} to @var{end_addr},
8605 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8606 (@value{GDBN} can only append data to files in raw binary form.)
8609 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8610 Restore the contents of file @var{filename} into memory. The
8611 @code{restore} command can automatically recognize any known @sc{bfd}
8612 file format, except for raw binary. To restore a raw binary file you
8613 must specify the optional keyword @code{binary} after the filename.
8615 If @var{bias} is non-zero, its value will be added to the addresses
8616 contained in the file. Binary files always start at address zero, so
8617 they will be restored at address @var{bias}. Other bfd files have
8618 a built-in location; they will be restored at offset @var{bias}
8621 If @var{start} and/or @var{end} are non-zero, then only data between
8622 file offset @var{start} and file offset @var{end} will be restored.
8623 These offsets are relative to the addresses in the file, before
8624 the @var{bias} argument is applied.
8628 @node Core File Generation
8629 @section How to Produce a Core File from Your Program
8630 @cindex dump core from inferior
8632 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8633 image of a running process and its process status (register values
8634 etc.). Its primary use is post-mortem debugging of a program that
8635 crashed while it ran outside a debugger. A program that crashes
8636 automatically produces a core file, unless this feature is disabled by
8637 the user. @xref{Files}, for information on invoking @value{GDBN} in
8638 the post-mortem debugging mode.
8640 Occasionally, you may wish to produce a core file of the program you
8641 are debugging in order to preserve a snapshot of its state.
8642 @value{GDBN} has a special command for that.
8646 @kindex generate-core-file
8647 @item generate-core-file [@var{file}]
8648 @itemx gcore [@var{file}]
8649 Produce a core dump of the inferior process. The optional argument
8650 @var{file} specifies the file name where to put the core dump. If not
8651 specified, the file name defaults to @file{core.@var{pid}}, where
8652 @var{pid} is the inferior process ID.
8654 Note that this command is implemented only for some systems (as of
8655 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8658 @node Character Sets
8659 @section Character Sets
8660 @cindex character sets
8662 @cindex translating between character sets
8663 @cindex host character set
8664 @cindex target character set
8666 If the program you are debugging uses a different character set to
8667 represent characters and strings than the one @value{GDBN} uses itself,
8668 @value{GDBN} can automatically translate between the character sets for
8669 you. The character set @value{GDBN} uses we call the @dfn{host
8670 character set}; the one the inferior program uses we call the
8671 @dfn{target character set}.
8673 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8674 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8675 remote protocol (@pxref{Remote Debugging}) to debug a program
8676 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8677 then the host character set is Latin-1, and the target character set is
8678 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8679 target-charset EBCDIC-US}, then @value{GDBN} translates between
8680 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8681 character and string literals in expressions.
8683 @value{GDBN} has no way to automatically recognize which character set
8684 the inferior program uses; you must tell it, using the @code{set
8685 target-charset} command, described below.
8687 Here are the commands for controlling @value{GDBN}'s character set
8691 @item set target-charset @var{charset}
8692 @kindex set target-charset
8693 Set the current target character set to @var{charset}. To display the
8694 list of supported target character sets, type
8695 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8697 @item set host-charset @var{charset}
8698 @kindex set host-charset
8699 Set the current host character set to @var{charset}.
8701 By default, @value{GDBN} uses a host character set appropriate to the
8702 system it is running on; you can override that default using the
8703 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8704 automatically determine the appropriate host character set. In this
8705 case, @value{GDBN} uses @samp{UTF-8}.
8707 @value{GDBN} can only use certain character sets as its host character
8708 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8709 @value{GDBN} will list the host character sets it supports.
8711 @item set charset @var{charset}
8713 Set the current host and target character sets to @var{charset}. As
8714 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8715 @value{GDBN} will list the names of the character sets that can be used
8716 for both host and target.
8719 @kindex show charset
8720 Show the names of the current host and target character sets.
8722 @item show host-charset
8723 @kindex show host-charset
8724 Show the name of the current host character set.
8726 @item show target-charset
8727 @kindex show target-charset
8728 Show the name of the current target character set.
8730 @item set target-wide-charset @var{charset}
8731 @kindex set target-wide-charset
8732 Set the current target's wide character set to @var{charset}. This is
8733 the character set used by the target's @code{wchar_t} type. To
8734 display the list of supported wide character sets, type
8735 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8737 @item show target-wide-charset
8738 @kindex show target-wide-charset
8739 Show the name of the current target's wide character set.
8742 Here is an example of @value{GDBN}'s character set support in action.
8743 Assume that the following source code has been placed in the file
8744 @file{charset-test.c}:
8750 = @{72, 101, 108, 108, 111, 44, 32, 119,
8751 111, 114, 108, 100, 33, 10, 0@};
8752 char ibm1047_hello[]
8753 = @{200, 133, 147, 147, 150, 107, 64, 166,
8754 150, 153, 147, 132, 90, 37, 0@};
8758 printf ("Hello, world!\n");
8762 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8763 containing the string @samp{Hello, world!} followed by a newline,
8764 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8766 We compile the program, and invoke the debugger on it:
8769 $ gcc -g charset-test.c -o charset-test
8770 $ gdb -nw charset-test
8771 GNU gdb 2001-12-19-cvs
8772 Copyright 2001 Free Software Foundation, Inc.
8777 We can use the @code{show charset} command to see what character sets
8778 @value{GDBN} is currently using to interpret and display characters and
8782 (@value{GDBP}) show charset
8783 The current host and target character set is `ISO-8859-1'.
8787 For the sake of printing this manual, let's use @sc{ascii} as our
8788 initial character set:
8790 (@value{GDBP}) set charset ASCII
8791 (@value{GDBP}) show charset
8792 The current host and target character set is `ASCII'.
8796 Let's assume that @sc{ascii} is indeed the correct character set for our
8797 host system --- in other words, let's assume that if @value{GDBN} prints
8798 characters using the @sc{ascii} character set, our terminal will display
8799 them properly. Since our current target character set is also
8800 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8803 (@value{GDBP}) print ascii_hello
8804 $1 = 0x401698 "Hello, world!\n"
8805 (@value{GDBP}) print ascii_hello[0]
8810 @value{GDBN} uses the target character set for character and string
8811 literals you use in expressions:
8814 (@value{GDBP}) print '+'
8819 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8822 @value{GDBN} relies on the user to tell it which character set the
8823 target program uses. If we print @code{ibm1047_hello} while our target
8824 character set is still @sc{ascii}, we get jibberish:
8827 (@value{GDBP}) print ibm1047_hello
8828 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8829 (@value{GDBP}) print ibm1047_hello[0]
8834 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8835 @value{GDBN} tells us the character sets it supports:
8838 (@value{GDBP}) set target-charset
8839 ASCII EBCDIC-US IBM1047 ISO-8859-1
8840 (@value{GDBP}) set target-charset
8843 We can select @sc{ibm1047} as our target character set, and examine the
8844 program's strings again. Now the @sc{ascii} string is wrong, but
8845 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8846 target character set, @sc{ibm1047}, to the host character set,
8847 @sc{ascii}, and they display correctly:
8850 (@value{GDBP}) set target-charset IBM1047
8851 (@value{GDBP}) show charset
8852 The current host character set is `ASCII'.
8853 The current target character set is `IBM1047'.
8854 (@value{GDBP}) print ascii_hello
8855 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8856 (@value{GDBP}) print ascii_hello[0]
8858 (@value{GDBP}) print ibm1047_hello
8859 $8 = 0x4016a8 "Hello, world!\n"
8860 (@value{GDBP}) print ibm1047_hello[0]
8865 As above, @value{GDBN} uses the target character set for character and
8866 string literals you use in expressions:
8869 (@value{GDBP}) print '+'
8874 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8877 @node Caching Remote Data
8878 @section Caching Data of Remote Targets
8879 @cindex caching data of remote targets
8881 @value{GDBN} caches data exchanged between the debugger and a
8882 remote target (@pxref{Remote Debugging}). Such caching generally improves
8883 performance, because it reduces the overhead of the remote protocol by
8884 bundling memory reads and writes into large chunks. Unfortunately, simply
8885 caching everything would lead to incorrect results, since @value{GDBN}
8886 does not necessarily know anything about volatile values, memory-mapped I/O
8887 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
8888 memory can be changed @emph{while} a gdb command is executing.
8889 Therefore, by default, @value{GDBN} only caches data
8890 known to be on the stack@footnote{In non-stop mode, it is moderately
8891 rare for a running thread to modify the stack of a stopped thread
8892 in a way that would interfere with a backtrace, and caching of
8893 stack reads provides a significant speed up of remote backtraces.}.
8894 Other regions of memory can be explicitly marked as
8895 cacheable; see @pxref{Memory Region Attributes}.
8898 @kindex set remotecache
8899 @item set remotecache on
8900 @itemx set remotecache off
8901 This option no longer does anything; it exists for compatibility
8904 @kindex show remotecache
8905 @item show remotecache
8906 Show the current state of the obsolete remotecache flag.
8908 @kindex set stack-cache
8909 @item set stack-cache on
8910 @itemx set stack-cache off
8911 Enable or disable caching of stack accesses. When @code{ON}, use
8912 caching. By default, this option is @code{ON}.
8914 @kindex show stack-cache
8915 @item show stack-cache
8916 Show the current state of data caching for memory accesses.
8919 @item info dcache @r{[}line@r{]}
8920 Print the information about the data cache performance. The
8921 information displayed includes the dcache width and depth, and for
8922 each cache line, its number, address, and how many times it was
8923 referenced. This command is useful for debugging the data cache
8926 If a line number is specified, the contents of that line will be
8930 @node Searching Memory
8931 @section Search Memory
8932 @cindex searching memory
8934 Memory can be searched for a particular sequence of bytes with the
8935 @code{find} command.
8939 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8940 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8941 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8942 etc. The search begins at address @var{start_addr} and continues for either
8943 @var{len} bytes or through to @var{end_addr} inclusive.
8946 @var{s} and @var{n} are optional parameters.
8947 They may be specified in either order, apart or together.
8950 @item @var{s}, search query size
8951 The size of each search query value.
8957 halfwords (two bytes)
8961 giant words (eight bytes)
8964 All values are interpreted in the current language.
8965 This means, for example, that if the current source language is C/C@t{++}
8966 then searching for the string ``hello'' includes the trailing '\0'.
8968 If the value size is not specified, it is taken from the
8969 value's type in the current language.
8970 This is useful when one wants to specify the search
8971 pattern as a mixture of types.
8972 Note that this means, for example, that in the case of C-like languages
8973 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8974 which is typically four bytes.
8976 @item @var{n}, maximum number of finds
8977 The maximum number of matches to print. The default is to print all finds.
8980 You can use strings as search values. Quote them with double-quotes
8982 The string value is copied into the search pattern byte by byte,
8983 regardless of the endianness of the target and the size specification.
8985 The address of each match found is printed as well as a count of the
8986 number of matches found.
8988 The address of the last value found is stored in convenience variable
8990 A count of the number of matches is stored in @samp{$numfound}.
8992 For example, if stopped at the @code{printf} in this function:
8998 static char hello[] = "hello-hello";
8999 static struct @{ char c; short s; int i; @}
9000 __attribute__ ((packed)) mixed
9001 = @{ 'c', 0x1234, 0x87654321 @};
9002 printf ("%s\n", hello);
9007 you get during debugging:
9010 (gdb) find &hello[0], +sizeof(hello), "hello"
9011 0x804956d <hello.1620+6>
9013 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9014 0x8049567 <hello.1620>
9015 0x804956d <hello.1620+6>
9017 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9018 0x8049567 <hello.1620>
9020 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9021 0x8049560 <mixed.1625>
9023 (gdb) print $numfound
9026 $2 = (void *) 0x8049560
9029 @node Optimized Code
9030 @chapter Debugging Optimized Code
9031 @cindex optimized code, debugging
9032 @cindex debugging optimized code
9034 Almost all compilers support optimization. With optimization
9035 disabled, the compiler generates assembly code that corresponds
9036 directly to your source code, in a simplistic way. As the compiler
9037 applies more powerful optimizations, the generated assembly code
9038 diverges from your original source code. With help from debugging
9039 information generated by the compiler, @value{GDBN} can map from
9040 the running program back to constructs from your original source.
9042 @value{GDBN} is more accurate with optimization disabled. If you
9043 can recompile without optimization, it is easier to follow the
9044 progress of your program during debugging. But, there are many cases
9045 where you may need to debug an optimized version.
9047 When you debug a program compiled with @samp{-g -O}, remember that the
9048 optimizer has rearranged your code; the debugger shows you what is
9049 really there. Do not be too surprised when the execution path does not
9050 exactly match your source file! An extreme example: if you define a
9051 variable, but never use it, @value{GDBN} never sees that
9052 variable---because the compiler optimizes it out of existence.
9054 Some things do not work as well with @samp{-g -O} as with just
9055 @samp{-g}, particularly on machines with instruction scheduling. If in
9056 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9057 please report it to us as a bug (including a test case!).
9058 @xref{Variables}, for more information about debugging optimized code.
9061 * Inline Functions:: How @value{GDBN} presents inlining
9064 @node Inline Functions
9065 @section Inline Functions
9066 @cindex inline functions, debugging
9068 @dfn{Inlining} is an optimization that inserts a copy of the function
9069 body directly at each call site, instead of jumping to a shared
9070 routine. @value{GDBN} displays inlined functions just like
9071 non-inlined functions. They appear in backtraces. You can view their
9072 arguments and local variables, step into them with @code{step}, skip
9073 them with @code{next}, and escape from them with @code{finish}.
9074 You can check whether a function was inlined by using the
9075 @code{info frame} command.
9077 For @value{GDBN} to support inlined functions, the compiler must
9078 record information about inlining in the debug information ---
9079 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9080 other compilers do also. @value{GDBN} only supports inlined functions
9081 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9082 do not emit two required attributes (@samp{DW_AT_call_file} and
9083 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9084 function calls with earlier versions of @value{NGCC}. It instead
9085 displays the arguments and local variables of inlined functions as
9086 local variables in the caller.
9088 The body of an inlined function is directly included at its call site;
9089 unlike a non-inlined function, there are no instructions devoted to
9090 the call. @value{GDBN} still pretends that the call site and the
9091 start of the inlined function are different instructions. Stepping to
9092 the call site shows the call site, and then stepping again shows
9093 the first line of the inlined function, even though no additional
9094 instructions are executed.
9096 This makes source-level debugging much clearer; you can see both the
9097 context of the call and then the effect of the call. Only stepping by
9098 a single instruction using @code{stepi} or @code{nexti} does not do
9099 this; single instruction steps always show the inlined body.
9101 There are some ways that @value{GDBN} does not pretend that inlined
9102 function calls are the same as normal calls:
9106 You cannot set breakpoints on inlined functions. @value{GDBN}
9107 either reports that there is no symbol with that name, or else sets the
9108 breakpoint only on non-inlined copies of the function. This limitation
9109 will be removed in a future version of @value{GDBN}; until then,
9110 set a breakpoint by line number on the first line of the inlined
9114 Setting breakpoints at the call site of an inlined function may not
9115 work, because the call site does not contain any code. @value{GDBN}
9116 may incorrectly move the breakpoint to the next line of the enclosing
9117 function, after the call. This limitation will be removed in a future
9118 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9119 or inside the inlined function instead.
9122 @value{GDBN} cannot locate the return value of inlined calls after
9123 using the @code{finish} command. This is a limitation of compiler-generated
9124 debugging information; after @code{finish}, you can step to the next line
9125 and print a variable where your program stored the return value.
9131 @chapter C Preprocessor Macros
9133 Some languages, such as C and C@t{++}, provide a way to define and invoke
9134 ``preprocessor macros'' which expand into strings of tokens.
9135 @value{GDBN} can evaluate expressions containing macro invocations, show
9136 the result of macro expansion, and show a macro's definition, including
9137 where it was defined.
9139 You may need to compile your program specially to provide @value{GDBN}
9140 with information about preprocessor macros. Most compilers do not
9141 include macros in their debugging information, even when you compile
9142 with the @option{-g} flag. @xref{Compilation}.
9144 A program may define a macro at one point, remove that definition later,
9145 and then provide a different definition after that. Thus, at different
9146 points in the program, a macro may have different definitions, or have
9147 no definition at all. If there is a current stack frame, @value{GDBN}
9148 uses the macros in scope at that frame's source code line. Otherwise,
9149 @value{GDBN} uses the macros in scope at the current listing location;
9152 Whenever @value{GDBN} evaluates an expression, it always expands any
9153 macro invocations present in the expression. @value{GDBN} also provides
9154 the following commands for working with macros explicitly.
9158 @kindex macro expand
9159 @cindex macro expansion, showing the results of preprocessor
9160 @cindex preprocessor macro expansion, showing the results of
9161 @cindex expanding preprocessor macros
9162 @item macro expand @var{expression}
9163 @itemx macro exp @var{expression}
9164 Show the results of expanding all preprocessor macro invocations in
9165 @var{expression}. Since @value{GDBN} simply expands macros, but does
9166 not parse the result, @var{expression} need not be a valid expression;
9167 it can be any string of tokens.
9170 @item macro expand-once @var{expression}
9171 @itemx macro exp1 @var{expression}
9172 @cindex expand macro once
9173 @i{(This command is not yet implemented.)} Show the results of
9174 expanding those preprocessor macro invocations that appear explicitly in
9175 @var{expression}. Macro invocations appearing in that expansion are
9176 left unchanged. This command allows you to see the effect of a
9177 particular macro more clearly, without being confused by further
9178 expansions. Since @value{GDBN} simply expands macros, but does not
9179 parse the result, @var{expression} need not be a valid expression; it
9180 can be any string of tokens.
9183 @cindex macro definition, showing
9184 @cindex definition, showing a macro's
9185 @item info macro @var{macro}
9186 Show the definition of the macro named @var{macro}, and describe the
9187 source location or compiler command-line where that definition was established.
9189 @kindex macro define
9190 @cindex user-defined macros
9191 @cindex defining macros interactively
9192 @cindex macros, user-defined
9193 @item macro define @var{macro} @var{replacement-list}
9194 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9195 Introduce a definition for a preprocessor macro named @var{macro},
9196 invocations of which are replaced by the tokens given in
9197 @var{replacement-list}. The first form of this command defines an
9198 ``object-like'' macro, which takes no arguments; the second form
9199 defines a ``function-like'' macro, which takes the arguments given in
9202 A definition introduced by this command is in scope in every
9203 expression evaluated in @value{GDBN}, until it is removed with the
9204 @code{macro undef} command, described below. The definition overrides
9205 all definitions for @var{macro} present in the program being debugged,
9206 as well as any previous user-supplied definition.
9209 @item macro undef @var{macro}
9210 Remove any user-supplied definition for the macro named @var{macro}.
9211 This command only affects definitions provided with the @code{macro
9212 define} command, described above; it cannot remove definitions present
9213 in the program being debugged.
9217 List all the macros defined using the @code{macro define} command.
9220 @cindex macros, example of debugging with
9221 Here is a transcript showing the above commands in action. First, we
9222 show our source files:
9230 #define ADD(x) (M + x)
9235 printf ("Hello, world!\n");
9237 printf ("We're so creative.\n");
9239 printf ("Goodbye, world!\n");
9246 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9247 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9248 compiler includes information about preprocessor macros in the debugging
9252 $ gcc -gdwarf-2 -g3 sample.c -o sample
9256 Now, we start @value{GDBN} on our sample program:
9260 GNU gdb 2002-05-06-cvs
9261 Copyright 2002 Free Software Foundation, Inc.
9262 GDB is free software, @dots{}
9266 We can expand macros and examine their definitions, even when the
9267 program is not running. @value{GDBN} uses the current listing position
9268 to decide which macro definitions are in scope:
9271 (@value{GDBP}) list main
9274 5 #define ADD(x) (M + x)
9279 10 printf ("Hello, world!\n");
9281 12 printf ("We're so creative.\n");
9282 (@value{GDBP}) info macro ADD
9283 Defined at /home/jimb/gdb/macros/play/sample.c:5
9284 #define ADD(x) (M + x)
9285 (@value{GDBP}) info macro Q
9286 Defined at /home/jimb/gdb/macros/play/sample.h:1
9287 included at /home/jimb/gdb/macros/play/sample.c:2
9289 (@value{GDBP}) macro expand ADD(1)
9290 expands to: (42 + 1)
9291 (@value{GDBP}) macro expand-once ADD(1)
9292 expands to: once (M + 1)
9296 In the example above, note that @code{macro expand-once} expands only
9297 the macro invocation explicit in the original text --- the invocation of
9298 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9299 which was introduced by @code{ADD}.
9301 Once the program is running, @value{GDBN} uses the macro definitions in
9302 force at the source line of the current stack frame:
9305 (@value{GDBP}) break main
9306 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9308 Starting program: /home/jimb/gdb/macros/play/sample
9310 Breakpoint 1, main () at sample.c:10
9311 10 printf ("Hello, world!\n");
9315 At line 10, the definition of the macro @code{N} at line 9 is in force:
9318 (@value{GDBP}) info macro N
9319 Defined at /home/jimb/gdb/macros/play/sample.c:9
9321 (@value{GDBP}) macro expand N Q M
9323 (@value{GDBP}) print N Q M
9328 As we step over directives that remove @code{N}'s definition, and then
9329 give it a new definition, @value{GDBN} finds the definition (or lack
9330 thereof) in force at each point:
9335 12 printf ("We're so creative.\n");
9336 (@value{GDBP}) info macro N
9337 The symbol `N' has no definition as a C/C++ preprocessor macro
9338 at /home/jimb/gdb/macros/play/sample.c:12
9341 14 printf ("Goodbye, world!\n");
9342 (@value{GDBP}) info macro N
9343 Defined at /home/jimb/gdb/macros/play/sample.c:13
9345 (@value{GDBP}) macro expand N Q M
9346 expands to: 1729 < 42
9347 (@value{GDBP}) print N Q M
9352 In addition to source files, macros can be defined on the compilation command
9353 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9354 such a way, @value{GDBN} displays the location of their definition as line zero
9355 of the source file submitted to the compiler.
9358 (@value{GDBP}) info macro __STDC__
9359 Defined at /home/jimb/gdb/macros/play/sample.c:0
9366 @chapter Tracepoints
9367 @c This chapter is based on the documentation written by Michael
9368 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9371 In some applications, it is not feasible for the debugger to interrupt
9372 the program's execution long enough for the developer to learn
9373 anything helpful about its behavior. If the program's correctness
9374 depends on its real-time behavior, delays introduced by a debugger
9375 might cause the program to change its behavior drastically, or perhaps
9376 fail, even when the code itself is correct. It is useful to be able
9377 to observe the program's behavior without interrupting it.
9379 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9380 specify locations in the program, called @dfn{tracepoints}, and
9381 arbitrary expressions to evaluate when those tracepoints are reached.
9382 Later, using the @code{tfind} command, you can examine the values
9383 those expressions had when the program hit the tracepoints. The
9384 expressions may also denote objects in memory---structures or arrays,
9385 for example---whose values @value{GDBN} should record; while visiting
9386 a particular tracepoint, you may inspect those objects as if they were
9387 in memory at that moment. However, because @value{GDBN} records these
9388 values without interacting with you, it can do so quickly and
9389 unobtrusively, hopefully not disturbing the program's behavior.
9391 The tracepoint facility is currently available only for remote
9392 targets. @xref{Targets}. In addition, your remote target must know
9393 how to collect trace data. This functionality is implemented in the
9394 remote stub; however, none of the stubs distributed with @value{GDBN}
9395 support tracepoints as of this writing. The format of the remote
9396 packets used to implement tracepoints are described in @ref{Tracepoint
9399 It is also possible to get trace data from a file, in a manner reminiscent
9400 of corefiles; you specify the filename, and use @code{tfind} to search
9401 through the file. @xref{Trace Files}, for more details.
9403 This chapter describes the tracepoint commands and features.
9407 * Analyze Collected Data::
9408 * Tracepoint Variables::
9412 @node Set Tracepoints
9413 @section Commands to Set Tracepoints
9415 Before running such a @dfn{trace experiment}, an arbitrary number of
9416 tracepoints can be set. A tracepoint is actually a special type of
9417 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9418 standard breakpoint commands. For instance, as with breakpoints,
9419 tracepoint numbers are successive integers starting from one, and many
9420 of the commands associated with tracepoints take the tracepoint number
9421 as their argument, to identify which tracepoint to work on.
9423 For each tracepoint, you can specify, in advance, some arbitrary set
9424 of data that you want the target to collect in the trace buffer when
9425 it hits that tracepoint. The collected data can include registers,
9426 local variables, or global data. Later, you can use @value{GDBN}
9427 commands to examine the values these data had at the time the
9430 Tracepoints do not support every breakpoint feature. Ignore counts on
9431 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9432 commands when they are hit. Tracepoints may not be thread-specific
9435 @cindex fast tracepoints
9436 Some targets may support @dfn{fast tracepoints}, which are inserted in
9437 a different way (such as with a jump instead of a trap), that is
9438 faster but possibly restricted in where they may be installed.
9440 This section describes commands to set tracepoints and associated
9441 conditions and actions.
9444 * Create and Delete Tracepoints::
9445 * Enable and Disable Tracepoints::
9446 * Tracepoint Passcounts::
9447 * Tracepoint Conditions::
9448 * Trace State Variables::
9449 * Tracepoint Actions::
9450 * Listing Tracepoints::
9451 * Starting and Stopping Trace Experiments::
9452 * Tracepoint Restrictions::
9455 @node Create and Delete Tracepoints
9456 @subsection Create and Delete Tracepoints
9459 @cindex set tracepoint
9461 @item trace @var{location}
9462 The @code{trace} command is very similar to the @code{break} command.
9463 Its argument @var{location} can be a source line, a function name, or
9464 an address in the target program. @xref{Specify Location}. The
9465 @code{trace} command defines a tracepoint, which is a point in the
9466 target program where the debugger will briefly stop, collect some
9467 data, and then allow the program to continue. Setting a tracepoint or
9468 changing its actions doesn't take effect until the next @code{tstart}
9469 command, and once a trace experiment is running, further changes will
9470 not have any effect until the next trace experiment starts.
9472 Here are some examples of using the @code{trace} command:
9475 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9477 (@value{GDBP}) @b{trace +2} // 2 lines forward
9479 (@value{GDBP}) @b{trace my_function} // first source line of function
9481 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9483 (@value{GDBP}) @b{trace *0x2117c4} // an address
9487 You can abbreviate @code{trace} as @code{tr}.
9489 @item trace @var{location} if @var{cond}
9490 Set a tracepoint with condition @var{cond}; evaluate the expression
9491 @var{cond} each time the tracepoint is reached, and collect data only
9492 if the value is nonzero---that is, if @var{cond} evaluates as true.
9493 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9494 information on tracepoint conditions.
9496 @item ftrace @var{location} [ if @var{cond} ]
9497 @cindex set fast tracepoint
9499 The @code{ftrace} command sets a fast tracepoint. For targets that
9500 support them, fast tracepoints will use a more efficient but possibly
9501 less general technique to trigger data collection, such as a jump
9502 instruction instead of a trap, or some sort of hardware support. It
9503 may not be possible to create a fast tracepoint at the desired
9504 location, in which case the command will exit with an explanatory
9507 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9511 @cindex last tracepoint number
9512 @cindex recent tracepoint number
9513 @cindex tracepoint number
9514 The convenience variable @code{$tpnum} records the tracepoint number
9515 of the most recently set tracepoint.
9517 @kindex delete tracepoint
9518 @cindex tracepoint deletion
9519 @item delete tracepoint @r{[}@var{num}@r{]}
9520 Permanently delete one or more tracepoints. With no argument, the
9521 default is to delete all tracepoints. Note that the regular
9522 @code{delete} command can remove tracepoints also.
9527 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9529 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9533 You can abbreviate this command as @code{del tr}.
9536 @node Enable and Disable Tracepoints
9537 @subsection Enable and Disable Tracepoints
9539 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9542 @kindex disable tracepoint
9543 @item disable tracepoint @r{[}@var{num}@r{]}
9544 Disable tracepoint @var{num}, or all tracepoints if no argument
9545 @var{num} is given. A disabled tracepoint will have no effect during
9546 the next trace experiment, but it is not forgotten. You can re-enable
9547 a disabled tracepoint using the @code{enable tracepoint} command.
9549 @kindex enable tracepoint
9550 @item enable tracepoint @r{[}@var{num}@r{]}
9551 Enable tracepoint @var{num}, or all tracepoints. The enabled
9552 tracepoints will become effective the next time a trace experiment is
9556 @node Tracepoint Passcounts
9557 @subsection Tracepoint Passcounts
9561 @cindex tracepoint pass count
9562 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9563 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9564 automatically stop a trace experiment. If a tracepoint's passcount is
9565 @var{n}, then the trace experiment will be automatically stopped on
9566 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9567 @var{num} is not specified, the @code{passcount} command sets the
9568 passcount of the most recently defined tracepoint. If no passcount is
9569 given, the trace experiment will run until stopped explicitly by the
9575 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9576 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9578 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9579 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9580 (@value{GDBP}) @b{trace foo}
9581 (@value{GDBP}) @b{pass 3}
9582 (@value{GDBP}) @b{trace bar}
9583 (@value{GDBP}) @b{pass 2}
9584 (@value{GDBP}) @b{trace baz}
9585 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9586 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9587 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9588 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9592 @node Tracepoint Conditions
9593 @subsection Tracepoint Conditions
9594 @cindex conditional tracepoints
9595 @cindex tracepoint conditions
9597 The simplest sort of tracepoint collects data every time your program
9598 reaches a specified place. You can also specify a @dfn{condition} for
9599 a tracepoint. A condition is just a Boolean expression in your
9600 programming language (@pxref{Expressions, ,Expressions}). A
9601 tracepoint with a condition evaluates the expression each time your
9602 program reaches it, and data collection happens only if the condition
9605 Tracepoint conditions can be specified when a tracepoint is set, by
9606 using @samp{if} in the arguments to the @code{trace} command.
9607 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9608 also be set or changed at any time with the @code{condition} command,
9609 just as with breakpoints.
9611 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9612 the conditional expression itself. Instead, @value{GDBN} encodes the
9613 expression into an agent expression (@pxref{Agent Expressions}
9614 suitable for execution on the target, independently of @value{GDBN}.
9615 Global variables become raw memory locations, locals become stack
9616 accesses, and so forth.
9618 For instance, suppose you have a function that is usually called
9619 frequently, but should not be called after an error has occurred. You
9620 could use the following tracepoint command to collect data about calls
9621 of that function that happen while the error code is propagating
9622 through the program; an unconditional tracepoint could end up
9623 collecting thousands of useless trace frames that you would have to
9627 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9630 @node Trace State Variables
9631 @subsection Trace State Variables
9632 @cindex trace state variables
9634 A @dfn{trace state variable} is a special type of variable that is
9635 created and managed by target-side code. The syntax is the same as
9636 that for GDB's convenience variables (a string prefixed with ``$''),
9637 but they are stored on the target. They must be created explicitly,
9638 using a @code{tvariable} command. They are always 64-bit signed
9641 Trace state variables are remembered by @value{GDBN}, and downloaded
9642 to the target along with tracepoint information when the trace
9643 experiment starts. There are no intrinsic limits on the number of
9644 trace state variables, beyond memory limitations of the target.
9646 @cindex convenience variables, and trace state variables
9647 Although trace state variables are managed by the target, you can use
9648 them in print commands and expressions as if they were convenience
9649 variables; @value{GDBN} will get the current value from the target
9650 while the trace experiment is running. Trace state variables share
9651 the same namespace as other ``$'' variables, which means that you
9652 cannot have trace state variables with names like @code{$23} or
9653 @code{$pc}, nor can you have a trace state variable and a convenience
9654 variable with the same name.
9658 @item tvariable $@var{name} [ = @var{expression} ]
9660 The @code{tvariable} command creates a new trace state variable named
9661 @code{$@var{name}}, and optionally gives it an initial value of
9662 @var{expression}. @var{expression} is evaluated when this command is
9663 entered; the result will be converted to an integer if possible,
9664 otherwise @value{GDBN} will report an error. A subsequent
9665 @code{tvariable} command specifying the same name does not create a
9666 variable, but instead assigns the supplied initial value to the
9667 existing variable of that name, overwriting any previous initial
9668 value. The default initial value is 0.
9670 @item info tvariables
9671 @kindex info tvariables
9672 List all the trace state variables along with their initial values.
9673 Their current values may also be displayed, if the trace experiment is
9676 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
9677 @kindex delete tvariable
9678 Delete the given trace state variables, or all of them if no arguments
9683 @node Tracepoint Actions
9684 @subsection Tracepoint Action Lists
9688 @cindex tracepoint actions
9689 @item actions @r{[}@var{num}@r{]}
9690 This command will prompt for a list of actions to be taken when the
9691 tracepoint is hit. If the tracepoint number @var{num} is not
9692 specified, this command sets the actions for the one that was most
9693 recently defined (so that you can define a tracepoint and then say
9694 @code{actions} without bothering about its number). You specify the
9695 actions themselves on the following lines, one action at a time, and
9696 terminate the actions list with a line containing just @code{end}. So
9697 far, the only defined actions are @code{collect}, @code{teval}, and
9698 @code{while-stepping}.
9700 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
9701 Commands, ,Breakpoint Command Lists}), except that only the defined
9702 actions are allowed; any other @value{GDBN} command is rejected.
9704 @cindex remove actions from a tracepoint
9705 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9706 and follow it immediately with @samp{end}.
9709 (@value{GDBP}) @b{collect @var{data}} // collect some data
9711 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9713 (@value{GDBP}) @b{end} // signals the end of actions.
9716 In the following example, the action list begins with @code{collect}
9717 commands indicating the things to be collected when the tracepoint is
9718 hit. Then, in order to single-step and collect additional data
9719 following the tracepoint, a @code{while-stepping} command is used,
9720 followed by the list of things to be collected after each step in a
9721 sequence of single steps. The @code{while-stepping} command is
9722 terminated by its own separate @code{end} command. Lastly, the action
9723 list is terminated by an @code{end} command.
9726 (@value{GDBP}) @b{trace foo}
9727 (@value{GDBP}) @b{actions}
9728 Enter actions for tracepoint 1, one per line:
9732 > collect $pc, arr[i]
9737 @kindex collect @r{(tracepoints)}
9738 @item collect @var{expr1}, @var{expr2}, @dots{}
9739 Collect values of the given expressions when the tracepoint is hit.
9740 This command accepts a comma-separated list of any valid expressions.
9741 In addition to global, static, or local variables, the following
9742 special arguments are supported:
9746 collect all registers
9749 collect all function arguments
9752 collect all local variables.
9755 You can give several consecutive @code{collect} commands, each one
9756 with a single argument, or one @code{collect} command with several
9757 arguments separated by commas; the effect is the same.
9759 The command @code{info scope} (@pxref{Symbols, info scope}) is
9760 particularly useful for figuring out what data to collect.
9762 @kindex teval @r{(tracepoints)}
9763 @item teval @var{expr1}, @var{expr2}, @dots{}
9764 Evaluate the given expressions when the tracepoint is hit. This
9765 command accepts a comma-separated list of expressions. The results
9766 are discarded, so this is mainly useful for assigning values to trace
9767 state variables (@pxref{Trace State Variables}) without adding those
9768 values to the trace buffer, as would be the case if the @code{collect}
9771 @kindex while-stepping @r{(tracepoints)}
9772 @item while-stepping @var{n}
9773 Perform @var{n} single-step instruction traces after the tracepoint,
9774 collecting new data after each step. The @code{while-stepping}
9775 command is followed by the list of what to collect while stepping
9776 (followed by its own @code{end} command):
9780 > collect $regs, myglobal
9786 Note that @code{$pc} is not automatically collected by
9787 @code{while-stepping}; you need to explicitly collect that register if
9788 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
9791 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
9792 @kindex set default-collect
9793 @cindex default collection action
9794 This variable is a list of expressions to collect at each tracepoint
9795 hit. It is effectively an additional @code{collect} action prepended
9796 to every tracepoint action list. The expressions are parsed
9797 individually for each tracepoint, so for instance a variable named
9798 @code{xyz} may be interpreted as a global for one tracepoint, and a
9799 local for another, as appropriate to the tracepoint's location.
9801 @item show default-collect
9802 @kindex show default-collect
9803 Show the list of expressions that are collected by default at each
9808 @node Listing Tracepoints
9809 @subsection Listing Tracepoints
9812 @kindex info tracepoints
9814 @cindex information about tracepoints
9815 @item info tracepoints @r{[}@var{num}@r{]}
9816 Display information about the tracepoint @var{num}. If you don't
9817 specify a tracepoint number, displays information about all the
9818 tracepoints defined so far. The format is similar to that used for
9819 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
9820 command, simply restricting itself to tracepoints.
9822 A tracepoint's listing may include additional information specific to
9827 its passcount as given by the @code{passcount @var{n}} command
9831 (@value{GDBP}) @b{info trace}
9832 Num Type Disp Enb Address What
9833 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
9835 collect globfoo, $regs
9844 This command can be abbreviated @code{info tp}.
9847 @node Starting and Stopping Trace Experiments
9848 @subsection Starting and Stopping Trace Experiments
9852 @cindex start a new trace experiment
9853 @cindex collected data discarded
9855 This command takes no arguments. It starts the trace experiment, and
9856 begins collecting data. This has the side effect of discarding all
9857 the data collected in the trace buffer during the previous trace
9861 @cindex stop a running trace experiment
9863 This command takes no arguments. It ends the trace experiment, and
9864 stops collecting data.
9866 @strong{Note}: a trace experiment and data collection may stop
9867 automatically if any tracepoint's passcount is reached
9868 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
9871 @cindex status of trace data collection
9872 @cindex trace experiment, status of
9874 This command displays the status of the current trace data
9878 Here is an example of the commands we described so far:
9881 (@value{GDBP}) @b{trace gdb_c_test}
9882 (@value{GDBP}) @b{actions}
9883 Enter actions for tracepoint #1, one per line.
9884 > collect $regs,$locals,$args
9889 (@value{GDBP}) @b{tstart}
9890 [time passes @dots{}]
9891 (@value{GDBP}) @b{tstop}
9894 @cindex disconnected tracing
9895 You can choose to continue running the trace experiment even if
9896 @value{GDBN} disconnects from the target, voluntarily or
9897 involuntarily. For commands such as @code{detach}, the debugger will
9898 ask what you want to do with the trace. But for unexpected
9899 terminations (@value{GDBN} crash, network outage), it would be
9900 unfortunate to lose hard-won trace data, so the variable
9901 @code{disconnected-tracing} lets you decide whether the trace should
9902 continue running without @value{GDBN}.
9905 @item set disconnected-tracing on
9906 @itemx set disconnected-tracing off
9907 @kindex set disconnected-tracing
9908 Choose whether a tracing run should continue to run if @value{GDBN}
9909 has disconnected from the target. Note that @code{detach} or
9910 @code{quit} will ask you directly what to do about a running trace no
9911 matter what this variable's setting, so the variable is mainly useful
9912 for handling unexpected situations, such as loss of the network.
9914 @item show disconnected-tracing
9915 @kindex show disconnected-tracing
9916 Show the current choice for disconnected tracing.
9920 When you reconnect to the target, the trace experiment may or may not
9921 still be running; it might have filled the trace buffer in the
9922 meantime, or stopped for one of the other reasons. If it is running,
9923 it will continue after reconnection.
9925 Upon reconnection, the target will upload information about the
9926 tracepoints in effect. @value{GDBN} will then compare that
9927 information to the set of tracepoints currently defined, and attempt
9928 to match them up, allowing for the possibility that the numbers may
9929 have changed due to creation and deletion in the meantime. If one of
9930 the target's tracepoints does not match any in @value{GDBN}, the
9931 debugger will create a new tracepoint, so that you have a number with
9932 which to specify that tracepoint. This matching-up process is
9933 necessarily heuristic, and it may result in useless tracepoints being
9934 created; you may simply delete them if they are of no use.
9936 @cindex circular trace buffer
9937 If your target agent supports a @dfn{circular trace buffer}, then you
9938 can run a trace experiment indefinitely without filling the trace
9939 buffer; when space runs out, the agent deletes already-collected trace
9940 frames, oldest first, until there is enough room to continue
9941 collecting. This is especially useful if your tracepoints are being
9942 hit too often, and your trace gets terminated prematurely because the
9943 buffer is full. To ask for a circular trace buffer, simply set
9944 @samp{circular_trace_buffer} to on. You can set this at any time,
9945 including during tracing; if the agent can do it, it will change
9946 buffer handling on the fly, otherwise it will not take effect until
9950 @item set circular-trace-buffer on
9951 @itemx set circular-trace-buffer off
9952 @kindex set circular-trace-buffer
9953 Choose whether a tracing run should use a linear or circular buffer
9954 for trace data. A linear buffer will not lose any trace data, but may
9955 fill up prematurely, while a circular buffer will discard old trace
9956 data, but it will have always room for the latest tracepoint hits.
9958 @item show circular-trace-buffer
9959 @kindex show circular-trace-buffer
9960 Show the current choice for the trace buffer. Note that this may not
9961 match the agent's current buffer handling, nor is it guaranteed to
9962 match the setting that might have been in effect during a past run,
9963 for instance if you are looking at frames from a trace file.
9967 @node Tracepoint Restrictions
9968 @subsection Tracepoint Restrictions
9970 @cindex tracepoint restrictions
9971 There are a number of restrictions on the use of tracepoints. As
9972 described above, tracepoint data gathering occurs on the target
9973 without interaction from @value{GDBN}. Thus the full capabilities of
9974 the debugger are not available during data gathering, and then at data
9975 examination time, you will be limited by only having what was
9976 collected. The following items describe some common problems, but it
9977 is not exhaustive, and you may run into additional difficulties not
9983 Tracepoint expressions are intended to gather objects (lvalues). Thus
9984 the full flexibility of GDB's expression evaluator is not available.
9985 You cannot call functions, cast objects to aggregate types, access
9986 convenience variables or modify values (except by assignment to trace
9987 state variables). Some language features may implicitly call
9988 functions (for instance Objective-C fields with accessors), and therefore
9989 cannot be collected either.
9992 Collection of local variables, either individually or in bulk with
9993 @code{$locals} or @code{$args}, during @code{while-stepping} may
9994 behave erratically. The stepping action may enter a new scope (for
9995 instance by stepping into a function), or the location of the variable
9996 may change (for instance it is loaded into a register). The
9997 tracepoint data recorded uses the location information for the
9998 variables that is correct for the tracepoint location. When the
9999 tracepoint is created, it is not possible, in general, to determine
10000 where the steps of a @code{while-stepping} sequence will advance the
10001 program---particularly if a conditional branch is stepped.
10004 Collection of an incompletely-initialized or partially-destroyed object
10005 may result in something that @value{GDBN} cannot display, or displays
10006 in a misleading way.
10009 When @value{GDBN} displays a pointer to character it automatically
10010 dereferences the pointer to also display characters of the string
10011 being pointed to. However, collecting the pointer during tracing does
10012 not automatically collect the string. You need to explicitly
10013 dereference the pointer and provide size information if you want to
10014 collect not only the pointer, but the memory pointed to. For example,
10015 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10019 It is not possible to collect a complete stack backtrace at a
10020 tracepoint. Instead, you may collect the registers and a few hundred
10021 bytes from the stack pointer with something like @code{*$esp@@300}
10022 (adjust to use the name of the actual stack pointer register on your
10023 target architecture, and the amount of stack you wish to capture).
10024 Then the @code{backtrace} command will show a partial backtrace when
10025 using a trace frame. The number of stack frames that can be examined
10026 depends on the sizes of the frames in the collected stack. Note that
10027 if you ask for a block so large that it goes past the bottom of the
10028 stack, the target agent may report an error trying to read from an
10032 If you do not collect registers at a tracepoint, @value{GDBN} can
10033 infer that the value of @code{$pc} must be the same as the address of
10034 the tracepoint and use that when you are looking at a trace frame
10035 for that tracepoint. However, this cannot work if the tracepoint has
10036 multiple locations (for instance if it was set in a function that was
10037 inlined), or if it has a @code{while-stepping} loop. In those cases
10038 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10043 @node Analyze Collected Data
10044 @section Using the Collected Data
10046 After the tracepoint experiment ends, you use @value{GDBN} commands
10047 for examining the trace data. The basic idea is that each tracepoint
10048 collects a trace @dfn{snapshot} every time it is hit and another
10049 snapshot every time it single-steps. All these snapshots are
10050 consecutively numbered from zero and go into a buffer, and you can
10051 examine them later. The way you examine them is to @dfn{focus} on a
10052 specific trace snapshot. When the remote stub is focused on a trace
10053 snapshot, it will respond to all @value{GDBN} requests for memory and
10054 registers by reading from the buffer which belongs to that snapshot,
10055 rather than from @emph{real} memory or registers of the program being
10056 debugged. This means that @strong{all} @value{GDBN} commands
10057 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10058 behave as if we were currently debugging the program state as it was
10059 when the tracepoint occurred. Any requests for data that are not in
10060 the buffer will fail.
10063 * tfind:: How to select a trace snapshot
10064 * tdump:: How to display all data for a snapshot
10065 * save tracepoints:: How to save tracepoints for a future run
10069 @subsection @code{tfind @var{n}}
10072 @cindex select trace snapshot
10073 @cindex find trace snapshot
10074 The basic command for selecting a trace snapshot from the buffer is
10075 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10076 counting from zero. If no argument @var{n} is given, the next
10077 snapshot is selected.
10079 Here are the various forms of using the @code{tfind} command.
10083 Find the first snapshot in the buffer. This is a synonym for
10084 @code{tfind 0} (since 0 is the number of the first snapshot).
10087 Stop debugging trace snapshots, resume @emph{live} debugging.
10090 Same as @samp{tfind none}.
10093 No argument means find the next trace snapshot.
10096 Find the previous trace snapshot before the current one. This permits
10097 retracing earlier steps.
10099 @item tfind tracepoint @var{num}
10100 Find the next snapshot associated with tracepoint @var{num}. Search
10101 proceeds forward from the last examined trace snapshot. If no
10102 argument @var{num} is given, it means find the next snapshot collected
10103 for the same tracepoint as the current snapshot.
10105 @item tfind pc @var{addr}
10106 Find the next snapshot associated with the value @var{addr} of the
10107 program counter. Search proceeds forward from the last examined trace
10108 snapshot. If no argument @var{addr} is given, it means find the next
10109 snapshot with the same value of PC as the current snapshot.
10111 @item tfind outside @var{addr1}, @var{addr2}
10112 Find the next snapshot whose PC is outside the given range of
10113 addresses (exclusive).
10115 @item tfind range @var{addr1}, @var{addr2}
10116 Find the next snapshot whose PC is between @var{addr1} and
10117 @var{addr2} (inclusive).
10119 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10120 Find the next snapshot associated with the source line @var{n}. If
10121 the optional argument @var{file} is given, refer to line @var{n} in
10122 that source file. Search proceeds forward from the last examined
10123 trace snapshot. If no argument @var{n} is given, it means find the
10124 next line other than the one currently being examined; thus saying
10125 @code{tfind line} repeatedly can appear to have the same effect as
10126 stepping from line to line in a @emph{live} debugging session.
10129 The default arguments for the @code{tfind} commands are specifically
10130 designed to make it easy to scan through the trace buffer. For
10131 instance, @code{tfind} with no argument selects the next trace
10132 snapshot, and @code{tfind -} with no argument selects the previous
10133 trace snapshot. So, by giving one @code{tfind} command, and then
10134 simply hitting @key{RET} repeatedly you can examine all the trace
10135 snapshots in order. Or, by saying @code{tfind -} and then hitting
10136 @key{RET} repeatedly you can examine the snapshots in reverse order.
10137 The @code{tfind line} command with no argument selects the snapshot
10138 for the next source line executed. The @code{tfind pc} command with
10139 no argument selects the next snapshot with the same program counter
10140 (PC) as the current frame. The @code{tfind tracepoint} command with
10141 no argument selects the next trace snapshot collected by the same
10142 tracepoint as the current one.
10144 In addition to letting you scan through the trace buffer manually,
10145 these commands make it easy to construct @value{GDBN} scripts that
10146 scan through the trace buffer and print out whatever collected data
10147 you are interested in. Thus, if we want to examine the PC, FP, and SP
10148 registers from each trace frame in the buffer, we can say this:
10151 (@value{GDBP}) @b{tfind start}
10152 (@value{GDBP}) @b{while ($trace_frame != -1)}
10153 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10154 $trace_frame, $pc, $sp, $fp
10158 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10159 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10160 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10161 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10162 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10163 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10164 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10165 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10166 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10167 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10168 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10171 Or, if we want to examine the variable @code{X} at each source line in
10175 (@value{GDBP}) @b{tfind start}
10176 (@value{GDBP}) @b{while ($trace_frame != -1)}
10177 > printf "Frame %d, X == %d\n", $trace_frame, X
10187 @subsection @code{tdump}
10189 @cindex dump all data collected at tracepoint
10190 @cindex tracepoint data, display
10192 This command takes no arguments. It prints all the data collected at
10193 the current trace snapshot.
10196 (@value{GDBP}) @b{trace 444}
10197 (@value{GDBP}) @b{actions}
10198 Enter actions for tracepoint #2, one per line:
10199 > collect $regs, $locals, $args, gdb_long_test
10202 (@value{GDBP}) @b{tstart}
10204 (@value{GDBP}) @b{tfind line 444}
10205 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10207 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10209 (@value{GDBP}) @b{tdump}
10210 Data collected at tracepoint 2, trace frame 1:
10211 d0 0xc4aa0085 -995491707
10215 d4 0x71aea3d 119204413
10218 d7 0x380035 3670069
10219 a0 0x19e24a 1696330
10220 a1 0x3000668 50333288
10222 a3 0x322000 3284992
10223 a4 0x3000698 50333336
10224 a5 0x1ad3cc 1758156
10225 fp 0x30bf3c 0x30bf3c
10226 sp 0x30bf34 0x30bf34
10228 pc 0x20b2c8 0x20b2c8
10232 p = 0x20e5b4 "gdb-test"
10239 gdb_long_test = 17 '\021'
10244 @code{tdump} works by scanning the tracepoint's current collection
10245 actions and printing the value of each expression listed. So
10246 @code{tdump} can fail, if after a run, you change the tracepoint's
10247 actions to mention variables that were not collected during the run.
10249 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10250 uses the collected value of @code{$pc} to distinguish between trace
10251 frames that were collected at the tracepoint hit, and frames that were
10252 collected while stepping. This allows it to correctly choose whether
10253 to display the basic list of collections, or the collections from the
10254 body of the while-stepping loop. However, if @code{$pc} was not collected,
10255 then @code{tdump} will always attempt to dump using the basic collection
10256 list, and may fail if a while-stepping frame does not include all the
10257 same data that is collected at the tracepoint hit.
10258 @c This is getting pretty arcane, example would be good.
10260 @node save tracepoints
10261 @subsection @code{save tracepoints @var{filename}}
10262 @kindex save tracepoints
10263 @kindex save-tracepoints
10264 @cindex save tracepoints for future sessions
10266 This command saves all current tracepoint definitions together with
10267 their actions and passcounts, into a file @file{@var{filename}}
10268 suitable for use in a later debugging session. To read the saved
10269 tracepoint definitions, use the @code{source} command (@pxref{Command
10270 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10271 alias for @w{@code{save tracepoints}}
10273 @node Tracepoint Variables
10274 @section Convenience Variables for Tracepoints
10275 @cindex tracepoint variables
10276 @cindex convenience variables for tracepoints
10279 @vindex $trace_frame
10280 @item (int) $trace_frame
10281 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10282 snapshot is selected.
10284 @vindex $tracepoint
10285 @item (int) $tracepoint
10286 The tracepoint for the current trace snapshot.
10288 @vindex $trace_line
10289 @item (int) $trace_line
10290 The line number for the current trace snapshot.
10292 @vindex $trace_file
10293 @item (char []) $trace_file
10294 The source file for the current trace snapshot.
10296 @vindex $trace_func
10297 @item (char []) $trace_func
10298 The name of the function containing @code{$tracepoint}.
10301 Note: @code{$trace_file} is not suitable for use in @code{printf},
10302 use @code{output} instead.
10304 Here's a simple example of using these convenience variables for
10305 stepping through all the trace snapshots and printing some of their
10306 data. Note that these are not the same as trace state variables,
10307 which are managed by the target.
10310 (@value{GDBP}) @b{tfind start}
10312 (@value{GDBP}) @b{while $trace_frame != -1}
10313 > output $trace_file
10314 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10320 @section Using Trace Files
10321 @cindex trace files
10323 In some situations, the target running a trace experiment may no
10324 longer be available; perhaps it crashed, or the hardware was needed
10325 for a different activity. To handle these cases, you can arrange to
10326 dump the trace data into a file, and later use that file as a source
10327 of trace data, via the @code{target tfile} command.
10332 @item tsave [ -r ] @var{filename}
10333 Save the trace data to @var{filename}. By default, this command
10334 assumes that @var{filename} refers to the host filesystem, so if
10335 necessary @value{GDBN} will copy raw trace data up from the target and
10336 then save it. If the target supports it, you can also supply the
10337 optional argument @code{-r} (``remote'') to direct the target to save
10338 the data directly into @var{filename} in its own filesystem, which may be
10339 more efficient if the trace buffer is very large. (Note, however, that
10340 @code{target tfile} can only read from files accessible to the host.)
10342 @kindex target tfile
10344 @item target tfile @var{filename}
10345 Use the file named @var{filename} as a source of trace data. Commands
10346 that examine data work as they do with a live target, but it is not
10347 possible to run any new trace experiments. @code{tstatus} will report
10348 the state of the trace run at the moment the data was saved, as well
10349 as the current trace frame you are examining. @var{filename} must be
10350 on a filesystem accessible to the host.
10355 @chapter Debugging Programs That Use Overlays
10358 If your program is too large to fit completely in your target system's
10359 memory, you can sometimes use @dfn{overlays} to work around this
10360 problem. @value{GDBN} provides some support for debugging programs that
10364 * How Overlays Work:: A general explanation of overlays.
10365 * Overlay Commands:: Managing overlays in @value{GDBN}.
10366 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10367 mapped by asking the inferior.
10368 * Overlay Sample Program:: A sample program using overlays.
10371 @node How Overlays Work
10372 @section How Overlays Work
10373 @cindex mapped overlays
10374 @cindex unmapped overlays
10375 @cindex load address, overlay's
10376 @cindex mapped address
10377 @cindex overlay area
10379 Suppose you have a computer whose instruction address space is only 64
10380 kilobytes long, but which has much more memory which can be accessed by
10381 other means: special instructions, segment registers, or memory
10382 management hardware, for example. Suppose further that you want to
10383 adapt a program which is larger than 64 kilobytes to run on this system.
10385 One solution is to identify modules of your program which are relatively
10386 independent, and need not call each other directly; call these modules
10387 @dfn{overlays}. Separate the overlays from the main program, and place
10388 their machine code in the larger memory. Place your main program in
10389 instruction memory, but leave at least enough space there to hold the
10390 largest overlay as well.
10392 Now, to call a function located in an overlay, you must first copy that
10393 overlay's machine code from the large memory into the space set aside
10394 for it in the instruction memory, and then jump to its entry point
10397 @c NB: In the below the mapped area's size is greater or equal to the
10398 @c size of all overlays. This is intentional to remind the developer
10399 @c that overlays don't necessarily need to be the same size.
10403 Data Instruction Larger
10404 Address Space Address Space Address Space
10405 +-----------+ +-----------+ +-----------+
10407 +-----------+ +-----------+ +-----------+<-- overlay 1
10408 | program | | main | .----| overlay 1 | load address
10409 | variables | | program | | +-----------+
10410 | and heap | | | | | |
10411 +-----------+ | | | +-----------+<-- overlay 2
10412 | | +-----------+ | | | load address
10413 +-----------+ | | | .-| overlay 2 |
10415 mapped --->+-----------+ | | +-----------+
10416 address | | | | | |
10417 | overlay | <-' | | |
10418 | area | <---' +-----------+<-- overlay 3
10419 | | <---. | | load address
10420 +-----------+ `--| overlay 3 |
10427 @anchor{A code overlay}A code overlay
10431 The diagram (@pxref{A code overlay}) shows a system with separate data
10432 and instruction address spaces. To map an overlay, the program copies
10433 its code from the larger address space to the instruction address space.
10434 Since the overlays shown here all use the same mapped address, only one
10435 may be mapped at a time. For a system with a single address space for
10436 data and instructions, the diagram would be similar, except that the
10437 program variables and heap would share an address space with the main
10438 program and the overlay area.
10440 An overlay loaded into instruction memory and ready for use is called a
10441 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10442 instruction memory. An overlay not present (or only partially present)
10443 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10444 is its address in the larger memory. The mapped address is also called
10445 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10446 called the @dfn{load memory address}, or @dfn{LMA}.
10448 Unfortunately, overlays are not a completely transparent way to adapt a
10449 program to limited instruction memory. They introduce a new set of
10450 global constraints you must keep in mind as you design your program:
10455 Before calling or returning to a function in an overlay, your program
10456 must make sure that overlay is actually mapped. Otherwise, the call or
10457 return will transfer control to the right address, but in the wrong
10458 overlay, and your program will probably crash.
10461 If the process of mapping an overlay is expensive on your system, you
10462 will need to choose your overlays carefully to minimize their effect on
10463 your program's performance.
10466 The executable file you load onto your system must contain each
10467 overlay's instructions, appearing at the overlay's load address, not its
10468 mapped address. However, each overlay's instructions must be relocated
10469 and its symbols defined as if the overlay were at its mapped address.
10470 You can use GNU linker scripts to specify different load and relocation
10471 addresses for pieces of your program; see @ref{Overlay Description,,,
10472 ld.info, Using ld: the GNU linker}.
10475 The procedure for loading executable files onto your system must be able
10476 to load their contents into the larger address space as well as the
10477 instruction and data spaces.
10481 The overlay system described above is rather simple, and could be
10482 improved in many ways:
10487 If your system has suitable bank switch registers or memory management
10488 hardware, you could use those facilities to make an overlay's load area
10489 contents simply appear at their mapped address in instruction space.
10490 This would probably be faster than copying the overlay to its mapped
10491 area in the usual way.
10494 If your overlays are small enough, you could set aside more than one
10495 overlay area, and have more than one overlay mapped at a time.
10498 You can use overlays to manage data, as well as instructions. In
10499 general, data overlays are even less transparent to your design than
10500 code overlays: whereas code overlays only require care when you call or
10501 return to functions, data overlays require care every time you access
10502 the data. Also, if you change the contents of a data overlay, you
10503 must copy its contents back out to its load address before you can copy a
10504 different data overlay into the same mapped area.
10509 @node Overlay Commands
10510 @section Overlay Commands
10512 To use @value{GDBN}'s overlay support, each overlay in your program must
10513 correspond to a separate section of the executable file. The section's
10514 virtual memory address and load memory address must be the overlay's
10515 mapped and load addresses. Identifying overlays with sections allows
10516 @value{GDBN} to determine the appropriate address of a function or
10517 variable, depending on whether the overlay is mapped or not.
10519 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10520 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10525 Disable @value{GDBN}'s overlay support. When overlay support is
10526 disabled, @value{GDBN} assumes that all functions and variables are
10527 always present at their mapped addresses. By default, @value{GDBN}'s
10528 overlay support is disabled.
10530 @item overlay manual
10531 @cindex manual overlay debugging
10532 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10533 relies on you to tell it which overlays are mapped, and which are not,
10534 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10535 commands described below.
10537 @item overlay map-overlay @var{overlay}
10538 @itemx overlay map @var{overlay}
10539 @cindex map an overlay
10540 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10541 be the name of the object file section containing the overlay. When an
10542 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10543 functions and variables at their mapped addresses. @value{GDBN} assumes
10544 that any other overlays whose mapped ranges overlap that of
10545 @var{overlay} are now unmapped.
10547 @item overlay unmap-overlay @var{overlay}
10548 @itemx overlay unmap @var{overlay}
10549 @cindex unmap an overlay
10550 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10551 must be the name of the object file section containing the overlay.
10552 When an overlay is unmapped, @value{GDBN} assumes it can find the
10553 overlay's functions and variables at their load addresses.
10556 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10557 consults a data structure the overlay manager maintains in the inferior
10558 to see which overlays are mapped. For details, see @ref{Automatic
10559 Overlay Debugging}.
10561 @item overlay load-target
10562 @itemx overlay load
10563 @cindex reloading the overlay table
10564 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10565 re-reads the table @value{GDBN} automatically each time the inferior
10566 stops, so this command should only be necessary if you have changed the
10567 overlay mapping yourself using @value{GDBN}. This command is only
10568 useful when using automatic overlay debugging.
10570 @item overlay list-overlays
10571 @itemx overlay list
10572 @cindex listing mapped overlays
10573 Display a list of the overlays currently mapped, along with their mapped
10574 addresses, load addresses, and sizes.
10578 Normally, when @value{GDBN} prints a code address, it includes the name
10579 of the function the address falls in:
10582 (@value{GDBP}) print main
10583 $3 = @{int ()@} 0x11a0 <main>
10586 When overlay debugging is enabled, @value{GDBN} recognizes code in
10587 unmapped overlays, and prints the names of unmapped functions with
10588 asterisks around them. For example, if @code{foo} is a function in an
10589 unmapped overlay, @value{GDBN} prints it this way:
10592 (@value{GDBP}) overlay list
10593 No sections are mapped.
10594 (@value{GDBP}) print foo
10595 $5 = @{int (int)@} 0x100000 <*foo*>
10598 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10602 (@value{GDBP}) overlay list
10603 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10604 mapped at 0x1016 - 0x104a
10605 (@value{GDBP}) print foo
10606 $6 = @{int (int)@} 0x1016 <foo>
10609 When overlay debugging is enabled, @value{GDBN} can find the correct
10610 address for functions and variables in an overlay, whether or not the
10611 overlay is mapped. This allows most @value{GDBN} commands, like
10612 @code{break} and @code{disassemble}, to work normally, even on unmapped
10613 code. However, @value{GDBN}'s breakpoint support has some limitations:
10617 @cindex breakpoints in overlays
10618 @cindex overlays, setting breakpoints in
10619 You can set breakpoints in functions in unmapped overlays, as long as
10620 @value{GDBN} can write to the overlay at its load address.
10622 @value{GDBN} can not set hardware or simulator-based breakpoints in
10623 unmapped overlays. However, if you set a breakpoint at the end of your
10624 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10625 you are using manual overlay management), @value{GDBN} will re-set its
10626 breakpoints properly.
10630 @node Automatic Overlay Debugging
10631 @section Automatic Overlay Debugging
10632 @cindex automatic overlay debugging
10634 @value{GDBN} can automatically track which overlays are mapped and which
10635 are not, given some simple co-operation from the overlay manager in the
10636 inferior. If you enable automatic overlay debugging with the
10637 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
10638 looks in the inferior's memory for certain variables describing the
10639 current state of the overlays.
10641 Here are the variables your overlay manager must define to support
10642 @value{GDBN}'s automatic overlay debugging:
10646 @item @code{_ovly_table}:
10647 This variable must be an array of the following structures:
10652 /* The overlay's mapped address. */
10655 /* The size of the overlay, in bytes. */
10656 unsigned long size;
10658 /* The overlay's load address. */
10661 /* Non-zero if the overlay is currently mapped;
10663 unsigned long mapped;
10667 @item @code{_novlys}:
10668 This variable must be a four-byte signed integer, holding the total
10669 number of elements in @code{_ovly_table}.
10673 To decide whether a particular overlay is mapped or not, @value{GDBN}
10674 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
10675 @code{lma} members equal the VMA and LMA of the overlay's section in the
10676 executable file. When @value{GDBN} finds a matching entry, it consults
10677 the entry's @code{mapped} member to determine whether the overlay is
10680 In addition, your overlay manager may define a function called
10681 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
10682 will silently set a breakpoint there. If the overlay manager then
10683 calls this function whenever it has changed the overlay table, this
10684 will enable @value{GDBN} to accurately keep track of which overlays
10685 are in program memory, and update any breakpoints that may be set
10686 in overlays. This will allow breakpoints to work even if the
10687 overlays are kept in ROM or other non-writable memory while they
10688 are not being executed.
10690 @node Overlay Sample Program
10691 @section Overlay Sample Program
10692 @cindex overlay example program
10694 When linking a program which uses overlays, you must place the overlays
10695 at their load addresses, while relocating them to run at their mapped
10696 addresses. To do this, you must write a linker script (@pxref{Overlay
10697 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
10698 since linker scripts are specific to a particular host system, target
10699 architecture, and target memory layout, this manual cannot provide
10700 portable sample code demonstrating @value{GDBN}'s overlay support.
10702 However, the @value{GDBN} source distribution does contain an overlaid
10703 program, with linker scripts for a few systems, as part of its test
10704 suite. The program consists of the following files from
10705 @file{gdb/testsuite/gdb.base}:
10709 The main program file.
10711 A simple overlay manager, used by @file{overlays.c}.
10716 Overlay modules, loaded and used by @file{overlays.c}.
10719 Linker scripts for linking the test program on the @code{d10v-elf}
10720 and @code{m32r-elf} targets.
10723 You can build the test program using the @code{d10v-elf} GCC
10724 cross-compiler like this:
10727 $ d10v-elf-gcc -g -c overlays.c
10728 $ d10v-elf-gcc -g -c ovlymgr.c
10729 $ d10v-elf-gcc -g -c foo.c
10730 $ d10v-elf-gcc -g -c bar.c
10731 $ d10v-elf-gcc -g -c baz.c
10732 $ d10v-elf-gcc -g -c grbx.c
10733 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
10734 baz.o grbx.o -Wl,-Td10v.ld -o overlays
10737 The build process is identical for any other architecture, except that
10738 you must substitute the appropriate compiler and linker script for the
10739 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
10743 @chapter Using @value{GDBN} with Different Languages
10746 Although programming languages generally have common aspects, they are
10747 rarely expressed in the same manner. For instance, in ANSI C,
10748 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
10749 Modula-2, it is accomplished by @code{p^}. Values can also be
10750 represented (and displayed) differently. Hex numbers in C appear as
10751 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
10753 @cindex working language
10754 Language-specific information is built into @value{GDBN} for some languages,
10755 allowing you to express operations like the above in your program's
10756 native language, and allowing @value{GDBN} to output values in a manner
10757 consistent with the syntax of your program's native language. The
10758 language you use to build expressions is called the @dfn{working
10762 * Setting:: Switching between source languages
10763 * Show:: Displaying the language
10764 * Checks:: Type and range checks
10765 * Supported Languages:: Supported languages
10766 * Unsupported Languages:: Unsupported languages
10770 @section Switching Between Source Languages
10772 There are two ways to control the working language---either have @value{GDBN}
10773 set it automatically, or select it manually yourself. You can use the
10774 @code{set language} command for either purpose. On startup, @value{GDBN}
10775 defaults to setting the language automatically. The working language is
10776 used to determine how expressions you type are interpreted, how values
10779 In addition to the working language, every source file that
10780 @value{GDBN} knows about has its own working language. For some object
10781 file formats, the compiler might indicate which language a particular
10782 source file is in. However, most of the time @value{GDBN} infers the
10783 language from the name of the file. The language of a source file
10784 controls whether C@t{++} names are demangled---this way @code{backtrace} can
10785 show each frame appropriately for its own language. There is no way to
10786 set the language of a source file from within @value{GDBN}, but you can
10787 set the language associated with a filename extension. @xref{Show, ,
10788 Displaying the Language}.
10790 This is most commonly a problem when you use a program, such
10791 as @code{cfront} or @code{f2c}, that generates C but is written in
10792 another language. In that case, make the
10793 program use @code{#line} directives in its C output; that way
10794 @value{GDBN} will know the correct language of the source code of the original
10795 program, and will display that source code, not the generated C code.
10798 * Filenames:: Filename extensions and languages.
10799 * Manually:: Setting the working language manually
10800 * Automatically:: Having @value{GDBN} infer the source language
10804 @subsection List of Filename Extensions and Languages
10806 If a source file name ends in one of the following extensions, then
10807 @value{GDBN} infers that its language is the one indicated.
10825 C@t{++} source file
10828 Objective-C source file
10832 Fortran source file
10835 Modula-2 source file
10839 Assembler source file. This actually behaves almost like C, but
10840 @value{GDBN} does not skip over function prologues when stepping.
10843 In addition, you may set the language associated with a filename
10844 extension. @xref{Show, , Displaying the Language}.
10847 @subsection Setting the Working Language
10849 If you allow @value{GDBN} to set the language automatically,
10850 expressions are interpreted the same way in your debugging session and
10853 @kindex set language
10854 If you wish, you may set the language manually. To do this, issue the
10855 command @samp{set language @var{lang}}, where @var{lang} is the name of
10856 a language, such as
10857 @code{c} or @code{modula-2}.
10858 For a list of the supported languages, type @samp{set language}.
10860 Setting the language manually prevents @value{GDBN} from updating the working
10861 language automatically. This can lead to confusion if you try
10862 to debug a program when the working language is not the same as the
10863 source language, when an expression is acceptable to both
10864 languages---but means different things. For instance, if the current
10865 source file were written in C, and @value{GDBN} was parsing Modula-2, a
10873 might not have the effect you intended. In C, this means to add
10874 @code{b} and @code{c} and place the result in @code{a}. The result
10875 printed would be the value of @code{a}. In Modula-2, this means to compare
10876 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
10878 @node Automatically
10879 @subsection Having @value{GDBN} Infer the Source Language
10881 To have @value{GDBN} set the working language automatically, use
10882 @samp{set language local} or @samp{set language auto}. @value{GDBN}
10883 then infers the working language. That is, when your program stops in a
10884 frame (usually by encountering a breakpoint), @value{GDBN} sets the
10885 working language to the language recorded for the function in that
10886 frame. If the language for a frame is unknown (that is, if the function
10887 or block corresponding to the frame was defined in a source file that
10888 does not have a recognized extension), the current working language is
10889 not changed, and @value{GDBN} issues a warning.
10891 This may not seem necessary for most programs, which are written
10892 entirely in one source language. However, program modules and libraries
10893 written in one source language can be used by a main program written in
10894 a different source language. Using @samp{set language auto} in this
10895 case frees you from having to set the working language manually.
10898 @section Displaying the Language
10900 The following commands help you find out which language is the
10901 working language, and also what language source files were written in.
10904 @item show language
10905 @kindex show language
10906 Display the current working language. This is the
10907 language you can use with commands such as @code{print} to
10908 build and compute expressions that may involve variables in your program.
10911 @kindex info frame@r{, show the source language}
10912 Display the source language for this frame. This language becomes the
10913 working language if you use an identifier from this frame.
10914 @xref{Frame Info, ,Information about a Frame}, to identify the other
10915 information listed here.
10918 @kindex info source@r{, show the source language}
10919 Display the source language of this source file.
10920 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
10921 information listed here.
10924 In unusual circumstances, you may have source files with extensions
10925 not in the standard list. You can then set the extension associated
10926 with a language explicitly:
10929 @item set extension-language @var{ext} @var{language}
10930 @kindex set extension-language
10931 Tell @value{GDBN} that source files with extension @var{ext} are to be
10932 assumed as written in the source language @var{language}.
10934 @item info extensions
10935 @kindex info extensions
10936 List all the filename extensions and the associated languages.
10940 @section Type and Range Checking
10943 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
10944 checking are included, but they do not yet have any effect. This
10945 section documents the intended facilities.
10947 @c FIXME remove warning when type/range code added
10949 Some languages are designed to guard you against making seemingly common
10950 errors through a series of compile- and run-time checks. These include
10951 checking the type of arguments to functions and operators, and making
10952 sure mathematical overflows are caught at run time. Checks such as
10953 these help to ensure a program's correctness once it has been compiled
10954 by eliminating type mismatches, and providing active checks for range
10955 errors when your program is running.
10957 @value{GDBN} can check for conditions like the above if you wish.
10958 Although @value{GDBN} does not check the statements in your program,
10959 it can check expressions entered directly into @value{GDBN} for
10960 evaluation via the @code{print} command, for example. As with the
10961 working language, @value{GDBN} can also decide whether or not to check
10962 automatically based on your program's source language.
10963 @xref{Supported Languages, ,Supported Languages}, for the default
10964 settings of supported languages.
10967 * Type Checking:: An overview of type checking
10968 * Range Checking:: An overview of range checking
10971 @cindex type checking
10972 @cindex checks, type
10973 @node Type Checking
10974 @subsection An Overview of Type Checking
10976 Some languages, such as Modula-2, are strongly typed, meaning that the
10977 arguments to operators and functions have to be of the correct type,
10978 otherwise an error occurs. These checks prevent type mismatch
10979 errors from ever causing any run-time problems. For example,
10987 The second example fails because the @code{CARDINAL} 1 is not
10988 type-compatible with the @code{REAL} 2.3.
10990 For the expressions you use in @value{GDBN} commands, you can tell the
10991 @value{GDBN} type checker to skip checking;
10992 to treat any mismatches as errors and abandon the expression;
10993 or to only issue warnings when type mismatches occur,
10994 but evaluate the expression anyway. When you choose the last of
10995 these, @value{GDBN} evaluates expressions like the second example above, but
10996 also issues a warning.
10998 Even if you turn type checking off, there may be other reasons
10999 related to type that prevent @value{GDBN} from evaluating an expression.
11000 For instance, @value{GDBN} does not know how to add an @code{int} and
11001 a @code{struct foo}. These particular type errors have nothing to do
11002 with the language in use, and usually arise from expressions, such as
11003 the one described above, which make little sense to evaluate anyway.
11005 Each language defines to what degree it is strict about type. For
11006 instance, both Modula-2 and C require the arguments to arithmetical
11007 operators to be numbers. In C, enumerated types and pointers can be
11008 represented as numbers, so that they are valid arguments to mathematical
11009 operators. @xref{Supported Languages, ,Supported Languages}, for further
11010 details on specific languages.
11012 @value{GDBN} provides some additional commands for controlling the type checker:
11014 @kindex set check type
11015 @kindex show check type
11017 @item set check type auto
11018 Set type checking on or off based on the current working language.
11019 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11022 @item set check type on
11023 @itemx set check type off
11024 Set type checking on or off, overriding the default setting for the
11025 current working language. Issue a warning if the setting does not
11026 match the language default. If any type mismatches occur in
11027 evaluating an expression while type checking is on, @value{GDBN} prints a
11028 message and aborts evaluation of the expression.
11030 @item set check type warn
11031 Cause the type checker to issue warnings, but to always attempt to
11032 evaluate the expression. Evaluating the expression may still
11033 be impossible for other reasons. For example, @value{GDBN} cannot add
11034 numbers and structures.
11037 Show the current setting of the type checker, and whether or not @value{GDBN}
11038 is setting it automatically.
11041 @cindex range checking
11042 @cindex checks, range
11043 @node Range Checking
11044 @subsection An Overview of Range Checking
11046 In some languages (such as Modula-2), it is an error to exceed the
11047 bounds of a type; this is enforced with run-time checks. Such range
11048 checking is meant to ensure program correctness by making sure
11049 computations do not overflow, or indices on an array element access do
11050 not exceed the bounds of the array.
11052 For expressions you use in @value{GDBN} commands, you can tell
11053 @value{GDBN} to treat range errors in one of three ways: ignore them,
11054 always treat them as errors and abandon the expression, or issue
11055 warnings but evaluate the expression anyway.
11057 A range error can result from numerical overflow, from exceeding an
11058 array index bound, or when you type a constant that is not a member
11059 of any type. Some languages, however, do not treat overflows as an
11060 error. In many implementations of C, mathematical overflow causes the
11061 result to ``wrap around'' to lower values---for example, if @var{m} is
11062 the largest integer value, and @var{s} is the smallest, then
11065 @var{m} + 1 @result{} @var{s}
11068 This, too, is specific to individual languages, and in some cases
11069 specific to individual compilers or machines. @xref{Supported Languages, ,
11070 Supported Languages}, for further details on specific languages.
11072 @value{GDBN} provides some additional commands for controlling the range checker:
11074 @kindex set check range
11075 @kindex show check range
11077 @item set check range auto
11078 Set range checking on or off based on the current working language.
11079 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11082 @item set check range on
11083 @itemx set check range off
11084 Set range checking on or off, overriding the default setting for the
11085 current working language. A warning is issued if the setting does not
11086 match the language default. If a range error occurs and range checking is on,
11087 then a message is printed and evaluation of the expression is aborted.
11089 @item set check range warn
11090 Output messages when the @value{GDBN} range checker detects a range error,
11091 but attempt to evaluate the expression anyway. Evaluating the
11092 expression may still be impossible for other reasons, such as accessing
11093 memory that the process does not own (a typical example from many Unix
11097 Show the current setting of the range checker, and whether or not it is
11098 being set automatically by @value{GDBN}.
11101 @node Supported Languages
11102 @section Supported Languages
11104 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
11105 assembly, Modula-2, and Ada.
11106 @c This is false ...
11107 Some @value{GDBN} features may be used in expressions regardless of the
11108 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11109 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11110 ,Expressions}) can be used with the constructs of any supported
11113 The following sections detail to what degree each source language is
11114 supported by @value{GDBN}. These sections are not meant to be language
11115 tutorials or references, but serve only as a reference guide to what the
11116 @value{GDBN} expression parser accepts, and what input and output
11117 formats should look like for different languages. There are many good
11118 books written on each of these languages; please look to these for a
11119 language reference or tutorial.
11122 * C:: C and C@t{++}
11123 * Objective-C:: Objective-C
11124 * Fortran:: Fortran
11126 * Modula-2:: Modula-2
11131 @subsection C and C@t{++}
11133 @cindex C and C@t{++}
11134 @cindex expressions in C or C@t{++}
11136 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11137 to both languages. Whenever this is the case, we discuss those languages
11141 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11142 @cindex @sc{gnu} C@t{++}
11143 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11144 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11145 effectively, you must compile your C@t{++} programs with a supported
11146 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11147 compiler (@code{aCC}).
11149 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11150 format; if it doesn't work on your system, try the stabs+ debugging
11151 format. You can select those formats explicitly with the @code{g++}
11152 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11153 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11154 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11157 * C Operators:: C and C@t{++} operators
11158 * C Constants:: C and C@t{++} constants
11159 * C Plus Plus Expressions:: C@t{++} expressions
11160 * C Defaults:: Default settings for C and C@t{++}
11161 * C Checks:: C and C@t{++} type and range checks
11162 * Debugging C:: @value{GDBN} and C
11163 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11164 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11168 @subsubsection C and C@t{++} Operators
11170 @cindex C and C@t{++} operators
11172 Operators must be defined on values of specific types. For instance,
11173 @code{+} is defined on numbers, but not on structures. Operators are
11174 often defined on groups of types.
11176 For the purposes of C and C@t{++}, the following definitions hold:
11181 @emph{Integral types} include @code{int} with any of its storage-class
11182 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11185 @emph{Floating-point types} include @code{float}, @code{double}, and
11186 @code{long double} (if supported by the target platform).
11189 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11192 @emph{Scalar types} include all of the above.
11197 The following operators are supported. They are listed here
11198 in order of increasing precedence:
11202 The comma or sequencing operator. Expressions in a comma-separated list
11203 are evaluated from left to right, with the result of the entire
11204 expression being the last expression evaluated.
11207 Assignment. The value of an assignment expression is the value
11208 assigned. Defined on scalar types.
11211 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11212 and translated to @w{@code{@var{a} = @var{a op b}}}.
11213 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11214 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11215 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11218 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11219 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11223 Logical @sc{or}. Defined on integral types.
11226 Logical @sc{and}. Defined on integral types.
11229 Bitwise @sc{or}. Defined on integral types.
11232 Bitwise exclusive-@sc{or}. Defined on integral types.
11235 Bitwise @sc{and}. Defined on integral types.
11238 Equality and inequality. Defined on scalar types. The value of these
11239 expressions is 0 for false and non-zero for true.
11241 @item <@r{, }>@r{, }<=@r{, }>=
11242 Less than, greater than, less than or equal, greater than or equal.
11243 Defined on scalar types. The value of these expressions is 0 for false
11244 and non-zero for true.
11247 left shift, and right shift. Defined on integral types.
11250 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11253 Addition and subtraction. Defined on integral types, floating-point types and
11256 @item *@r{, }/@r{, }%
11257 Multiplication, division, and modulus. Multiplication and division are
11258 defined on integral and floating-point types. Modulus is defined on
11262 Increment and decrement. When appearing before a variable, the
11263 operation is performed before the variable is used in an expression;
11264 when appearing after it, the variable's value is used before the
11265 operation takes place.
11268 Pointer dereferencing. Defined on pointer types. Same precedence as
11272 Address operator. Defined on variables. Same precedence as @code{++}.
11274 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11275 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11276 to examine the address
11277 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11281 Negative. Defined on integral and floating-point types. Same
11282 precedence as @code{++}.
11285 Logical negation. Defined on integral types. Same precedence as
11289 Bitwise complement operator. Defined on integral types. Same precedence as
11294 Structure member, and pointer-to-structure member. For convenience,
11295 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11296 pointer based on the stored type information.
11297 Defined on @code{struct} and @code{union} data.
11300 Dereferences of pointers to members.
11303 Array indexing. @code{@var{a}[@var{i}]} is defined as
11304 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11307 Function parameter list. Same precedence as @code{->}.
11310 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11311 and @code{class} types.
11314 Doubled colons also represent the @value{GDBN} scope operator
11315 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11319 If an operator is redefined in the user code, @value{GDBN} usually
11320 attempts to invoke the redefined version instead of using the operator's
11321 predefined meaning.
11324 @subsubsection C and C@t{++} Constants
11326 @cindex C and C@t{++} constants
11328 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11333 Integer constants are a sequence of digits. Octal constants are
11334 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11335 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11336 @samp{l}, specifying that the constant should be treated as a
11340 Floating point constants are a sequence of digits, followed by a decimal
11341 point, followed by a sequence of digits, and optionally followed by an
11342 exponent. An exponent is of the form:
11343 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11344 sequence of digits. The @samp{+} is optional for positive exponents.
11345 A floating-point constant may also end with a letter @samp{f} or
11346 @samp{F}, specifying that the constant should be treated as being of
11347 the @code{float} (as opposed to the default @code{double}) type; or with
11348 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11352 Enumerated constants consist of enumerated identifiers, or their
11353 integral equivalents.
11356 Character constants are a single character surrounded by single quotes
11357 (@code{'}), or a number---the ordinal value of the corresponding character
11358 (usually its @sc{ascii} value). Within quotes, the single character may
11359 be represented by a letter or by @dfn{escape sequences}, which are of
11360 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11361 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11362 @samp{@var{x}} is a predefined special character---for example,
11363 @samp{\n} for newline.
11366 String constants are a sequence of character constants surrounded by
11367 double quotes (@code{"}). Any valid character constant (as described
11368 above) may appear. Double quotes within the string must be preceded by
11369 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11373 Pointer constants are an integral value. You can also write pointers
11374 to constants using the C operator @samp{&}.
11377 Array constants are comma-separated lists surrounded by braces @samp{@{}
11378 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11379 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11380 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11383 @node C Plus Plus Expressions
11384 @subsubsection C@t{++} Expressions
11386 @cindex expressions in C@t{++}
11387 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11389 @cindex debugging C@t{++} programs
11390 @cindex C@t{++} compilers
11391 @cindex debug formats and C@t{++}
11392 @cindex @value{NGCC} and C@t{++}
11394 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11395 proper compiler and the proper debug format. Currently, @value{GDBN}
11396 works best when debugging C@t{++} code that is compiled with
11397 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11398 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11399 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11400 stabs+ as their default debug format, so you usually don't need to
11401 specify a debug format explicitly. Other compilers and/or debug formats
11402 are likely to work badly or not at all when using @value{GDBN} to debug
11408 @cindex member functions
11410 Member function calls are allowed; you can use expressions like
11413 count = aml->GetOriginal(x, y)
11416 @vindex this@r{, inside C@t{++} member functions}
11417 @cindex namespace in C@t{++}
11419 While a member function is active (in the selected stack frame), your
11420 expressions have the same namespace available as the member function;
11421 that is, @value{GDBN} allows implicit references to the class instance
11422 pointer @code{this} following the same rules as C@t{++}.
11424 @cindex call overloaded functions
11425 @cindex overloaded functions, calling
11426 @cindex type conversions in C@t{++}
11428 You can call overloaded functions; @value{GDBN} resolves the function
11429 call to the right definition, with some restrictions. @value{GDBN} does not
11430 perform overload resolution involving user-defined type conversions,
11431 calls to constructors, or instantiations of templates that do not exist
11432 in the program. It also cannot handle ellipsis argument lists or
11435 It does perform integral conversions and promotions, floating-point
11436 promotions, arithmetic conversions, pointer conversions, conversions of
11437 class objects to base classes, and standard conversions such as those of
11438 functions or arrays to pointers; it requires an exact match on the
11439 number of function arguments.
11441 Overload resolution is always performed, unless you have specified
11442 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11443 ,@value{GDBN} Features for C@t{++}}.
11445 You must specify @code{set overload-resolution off} in order to use an
11446 explicit function signature to call an overloaded function, as in
11448 p 'foo(char,int)'('x', 13)
11451 The @value{GDBN} command-completion facility can simplify this;
11452 see @ref{Completion, ,Command Completion}.
11454 @cindex reference declarations
11456 @value{GDBN} understands variables declared as C@t{++} references; you can use
11457 them in expressions just as you do in C@t{++} source---they are automatically
11460 In the parameter list shown when @value{GDBN} displays a frame, the values of
11461 reference variables are not displayed (unlike other variables); this
11462 avoids clutter, since references are often used for large structures.
11463 The @emph{address} of a reference variable is always shown, unless
11464 you have specified @samp{set print address off}.
11467 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11468 expressions can use it just as expressions in your program do. Since
11469 one scope may be defined in another, you can use @code{::} repeatedly if
11470 necessary, for example in an expression like
11471 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11472 resolving name scope by reference to source files, in both C and C@t{++}
11473 debugging (@pxref{Variables, ,Program Variables}).
11476 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11477 calling virtual functions correctly, printing out virtual bases of
11478 objects, calling functions in a base subobject, casting objects, and
11479 invoking user-defined operators.
11482 @subsubsection C and C@t{++} Defaults
11484 @cindex C and C@t{++} defaults
11486 If you allow @value{GDBN} to set type and range checking automatically, they
11487 both default to @code{off} whenever the working language changes to
11488 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11489 selects the working language.
11491 If you allow @value{GDBN} to set the language automatically, it
11492 recognizes source files whose names end with @file{.c}, @file{.C}, or
11493 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11494 these files, it sets the working language to C or C@t{++}.
11495 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11496 for further details.
11498 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11499 @c unimplemented. If (b) changes, it might make sense to let this node
11500 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11503 @subsubsection C and C@t{++} Type and Range Checks
11505 @cindex C and C@t{++} checks
11507 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11508 is not used. However, if you turn type checking on, @value{GDBN}
11509 considers two variables type equivalent if:
11513 The two variables are structured and have the same structure, union, or
11517 The two variables have the same type name, or types that have been
11518 declared equivalent through @code{typedef}.
11521 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11524 The two @code{struct}, @code{union}, or @code{enum} variables are
11525 declared in the same declaration. (Note: this may not be true for all C
11530 Range checking, if turned on, is done on mathematical operations. Array
11531 indices are not checked, since they are often used to index a pointer
11532 that is not itself an array.
11535 @subsubsection @value{GDBN} and C
11537 The @code{set print union} and @code{show print union} commands apply to
11538 the @code{union} type. When set to @samp{on}, any @code{union} that is
11539 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11540 appears as @samp{@{...@}}.
11542 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11543 with pointers and a memory allocation function. @xref{Expressions,
11546 @node Debugging C Plus Plus
11547 @subsubsection @value{GDBN} Features for C@t{++}
11549 @cindex commands for C@t{++}
11551 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11552 designed specifically for use with C@t{++}. Here is a summary:
11555 @cindex break in overloaded functions
11556 @item @r{breakpoint menus}
11557 When you want a breakpoint in a function whose name is overloaded,
11558 @value{GDBN} has the capability to display a menu of possible breakpoint
11559 locations to help you specify which function definition you want.
11560 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11562 @cindex overloading in C@t{++}
11563 @item rbreak @var{regex}
11564 Setting breakpoints using regular expressions is helpful for setting
11565 breakpoints on overloaded functions that are not members of any special
11567 @xref{Set Breaks, ,Setting Breakpoints}.
11569 @cindex C@t{++} exception handling
11572 Debug C@t{++} exception handling using these commands. @xref{Set
11573 Catchpoints, , Setting Catchpoints}.
11575 @cindex inheritance
11576 @item ptype @var{typename}
11577 Print inheritance relationships as well as other information for type
11579 @xref{Symbols, ,Examining the Symbol Table}.
11581 @cindex C@t{++} symbol display
11582 @item set print demangle
11583 @itemx show print demangle
11584 @itemx set print asm-demangle
11585 @itemx show print asm-demangle
11586 Control whether C@t{++} symbols display in their source form, both when
11587 displaying code as C@t{++} source and when displaying disassemblies.
11588 @xref{Print Settings, ,Print Settings}.
11590 @item set print object
11591 @itemx show print object
11592 Choose whether to print derived (actual) or declared types of objects.
11593 @xref{Print Settings, ,Print Settings}.
11595 @item set print vtbl
11596 @itemx show print vtbl
11597 Control the format for printing virtual function tables.
11598 @xref{Print Settings, ,Print Settings}.
11599 (The @code{vtbl} commands do not work on programs compiled with the HP
11600 ANSI C@t{++} compiler (@code{aCC}).)
11602 @kindex set overload-resolution
11603 @cindex overloaded functions, overload resolution
11604 @item set overload-resolution on
11605 Enable overload resolution for C@t{++} expression evaluation. The default
11606 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11607 and searches for a function whose signature matches the argument types,
11608 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11609 Expressions, ,C@t{++} Expressions}, for details).
11610 If it cannot find a match, it emits a message.
11612 @item set overload-resolution off
11613 Disable overload resolution for C@t{++} expression evaluation. For
11614 overloaded functions that are not class member functions, @value{GDBN}
11615 chooses the first function of the specified name that it finds in the
11616 symbol table, whether or not its arguments are of the correct type. For
11617 overloaded functions that are class member functions, @value{GDBN}
11618 searches for a function whose signature @emph{exactly} matches the
11621 @kindex show overload-resolution
11622 @item show overload-resolution
11623 Show the current setting of overload resolution.
11625 @item @r{Overloaded symbol names}
11626 You can specify a particular definition of an overloaded symbol, using
11627 the same notation that is used to declare such symbols in C@t{++}: type
11628 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
11629 also use the @value{GDBN} command-line word completion facilities to list the
11630 available choices, or to finish the type list for you.
11631 @xref{Completion,, Command Completion}, for details on how to do this.
11634 @node Decimal Floating Point
11635 @subsubsection Decimal Floating Point format
11636 @cindex decimal floating point format
11638 @value{GDBN} can examine, set and perform computations with numbers in
11639 decimal floating point format, which in the C language correspond to the
11640 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
11641 specified by the extension to support decimal floating-point arithmetic.
11643 There are two encodings in use, depending on the architecture: BID (Binary
11644 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
11645 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
11648 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
11649 to manipulate decimal floating point numbers, it is not possible to convert
11650 (using a cast, for example) integers wider than 32-bit to decimal float.
11652 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
11653 point computations, error checking in decimal float operations ignores
11654 underflow, overflow and divide by zero exceptions.
11656 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
11657 to inspect @code{_Decimal128} values stored in floating point registers.
11658 See @ref{PowerPC,,PowerPC} for more details.
11661 @subsection Objective-C
11663 @cindex Objective-C
11664 This section provides information about some commands and command
11665 options that are useful for debugging Objective-C code. See also
11666 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
11667 few more commands specific to Objective-C support.
11670 * Method Names in Commands::
11671 * The Print Command with Objective-C::
11674 @node Method Names in Commands
11675 @subsubsection Method Names in Commands
11677 The following commands have been extended to accept Objective-C method
11678 names as line specifications:
11680 @kindex clear@r{, and Objective-C}
11681 @kindex break@r{, and Objective-C}
11682 @kindex info line@r{, and Objective-C}
11683 @kindex jump@r{, and Objective-C}
11684 @kindex list@r{, and Objective-C}
11688 @item @code{info line}
11693 A fully qualified Objective-C method name is specified as
11696 -[@var{Class} @var{methodName}]
11699 where the minus sign is used to indicate an instance method and a
11700 plus sign (not shown) is used to indicate a class method. The class
11701 name @var{Class} and method name @var{methodName} are enclosed in
11702 brackets, similar to the way messages are specified in Objective-C
11703 source code. For example, to set a breakpoint at the @code{create}
11704 instance method of class @code{Fruit} in the program currently being
11708 break -[Fruit create]
11711 To list ten program lines around the @code{initialize} class method,
11715 list +[NSText initialize]
11718 In the current version of @value{GDBN}, the plus or minus sign is
11719 required. In future versions of @value{GDBN}, the plus or minus
11720 sign will be optional, but you can use it to narrow the search. It
11721 is also possible to specify just a method name:
11727 You must specify the complete method name, including any colons. If
11728 your program's source files contain more than one @code{create} method,
11729 you'll be presented with a numbered list of classes that implement that
11730 method. Indicate your choice by number, or type @samp{0} to exit if
11733 As another example, to clear a breakpoint established at the
11734 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
11737 clear -[NSWindow makeKeyAndOrderFront:]
11740 @node The Print Command with Objective-C
11741 @subsubsection The Print Command With Objective-C
11742 @cindex Objective-C, print objects
11743 @kindex print-object
11744 @kindex po @r{(@code{print-object})}
11746 The print command has also been extended to accept methods. For example:
11749 print -[@var{object} hash]
11752 @cindex print an Objective-C object description
11753 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
11755 will tell @value{GDBN} to send the @code{hash} message to @var{object}
11756 and print the result. Also, an additional command has been added,
11757 @code{print-object} or @code{po} for short, which is meant to print
11758 the description of an object. However, this command may only work
11759 with certain Objective-C libraries that have a particular hook
11760 function, @code{_NSPrintForDebugger}, defined.
11763 @subsection Fortran
11764 @cindex Fortran-specific support in @value{GDBN}
11766 @value{GDBN} can be used to debug programs written in Fortran, but it
11767 currently supports only the features of Fortran 77 language.
11769 @cindex trailing underscore, in Fortran symbols
11770 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
11771 among them) append an underscore to the names of variables and
11772 functions. When you debug programs compiled by those compilers, you
11773 will need to refer to variables and functions with a trailing
11777 * Fortran Operators:: Fortran operators and expressions
11778 * Fortran Defaults:: Default settings for Fortran
11779 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
11782 @node Fortran Operators
11783 @subsubsection Fortran Operators and Expressions
11785 @cindex Fortran operators and expressions
11787 Operators must be defined on values of specific types. For instance,
11788 @code{+} is defined on numbers, but not on characters or other non-
11789 arithmetic types. Operators are often defined on groups of types.
11793 The exponentiation operator. It raises the first operand to the power
11797 The range operator. Normally used in the form of array(low:high) to
11798 represent a section of array.
11801 The access component operator. Normally used to access elements in derived
11802 types. Also suitable for unions. As unions aren't part of regular Fortran,
11803 this can only happen when accessing a register that uses a gdbarch-defined
11807 @node Fortran Defaults
11808 @subsubsection Fortran Defaults
11810 @cindex Fortran Defaults
11812 Fortran symbols are usually case-insensitive, so @value{GDBN} by
11813 default uses case-insensitive matches for Fortran symbols. You can
11814 change that with the @samp{set case-insensitive} command, see
11815 @ref{Symbols}, for the details.
11817 @node Special Fortran Commands
11818 @subsubsection Special Fortran Commands
11820 @cindex Special Fortran commands
11822 @value{GDBN} has some commands to support Fortran-specific features,
11823 such as displaying common blocks.
11826 @cindex @code{COMMON} blocks, Fortran
11827 @kindex info common
11828 @item info common @r{[}@var{common-name}@r{]}
11829 This command prints the values contained in the Fortran @code{COMMON}
11830 block whose name is @var{common-name}. With no argument, the names of
11831 all @code{COMMON} blocks visible at the current program location are
11838 @cindex Pascal support in @value{GDBN}, limitations
11839 Debugging Pascal programs which use sets, subranges, file variables, or
11840 nested functions does not currently work. @value{GDBN} does not support
11841 entering expressions, printing values, or similar features using Pascal
11844 The Pascal-specific command @code{set print pascal_static-members}
11845 controls whether static members of Pascal objects are displayed.
11846 @xref{Print Settings, pascal_static-members}.
11849 @subsection Modula-2
11851 @cindex Modula-2, @value{GDBN} support
11853 The extensions made to @value{GDBN} to support Modula-2 only support
11854 output from the @sc{gnu} Modula-2 compiler (which is currently being
11855 developed). Other Modula-2 compilers are not currently supported, and
11856 attempting to debug executables produced by them is most likely
11857 to give an error as @value{GDBN} reads in the executable's symbol
11860 @cindex expressions in Modula-2
11862 * M2 Operators:: Built-in operators
11863 * Built-In Func/Proc:: Built-in functions and procedures
11864 * M2 Constants:: Modula-2 constants
11865 * M2 Types:: Modula-2 types
11866 * M2 Defaults:: Default settings for Modula-2
11867 * Deviations:: Deviations from standard Modula-2
11868 * M2 Checks:: Modula-2 type and range checks
11869 * M2 Scope:: The scope operators @code{::} and @code{.}
11870 * GDB/M2:: @value{GDBN} and Modula-2
11874 @subsubsection Operators
11875 @cindex Modula-2 operators
11877 Operators must be defined on values of specific types. For instance,
11878 @code{+} is defined on numbers, but not on structures. Operators are
11879 often defined on groups of types. For the purposes of Modula-2, the
11880 following definitions hold:
11885 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
11889 @emph{Character types} consist of @code{CHAR} and its subranges.
11892 @emph{Floating-point types} consist of @code{REAL}.
11895 @emph{Pointer types} consist of anything declared as @code{POINTER TO
11899 @emph{Scalar types} consist of all of the above.
11902 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
11905 @emph{Boolean types} consist of @code{BOOLEAN}.
11909 The following operators are supported, and appear in order of
11910 increasing precedence:
11914 Function argument or array index separator.
11917 Assignment. The value of @var{var} @code{:=} @var{value} is
11921 Less than, greater than on integral, floating-point, or enumerated
11925 Less than or equal to, greater than or equal to
11926 on integral, floating-point and enumerated types, or set inclusion on
11927 set types. Same precedence as @code{<}.
11929 @item =@r{, }<>@r{, }#
11930 Equality and two ways of expressing inequality, valid on scalar types.
11931 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
11932 available for inequality, since @code{#} conflicts with the script
11936 Set membership. Defined on set types and the types of their members.
11937 Same precedence as @code{<}.
11940 Boolean disjunction. Defined on boolean types.
11943 Boolean conjunction. Defined on boolean types.
11946 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11949 Addition and subtraction on integral and floating-point types, or union
11950 and difference on set types.
11953 Multiplication on integral and floating-point types, or set intersection
11957 Division on floating-point types, or symmetric set difference on set
11958 types. Same precedence as @code{*}.
11961 Integer division and remainder. Defined on integral types. Same
11962 precedence as @code{*}.
11965 Negative. Defined on @code{INTEGER} and @code{REAL} data.
11968 Pointer dereferencing. Defined on pointer types.
11971 Boolean negation. Defined on boolean types. Same precedence as
11975 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
11976 precedence as @code{^}.
11979 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
11982 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
11986 @value{GDBN} and Modula-2 scope operators.
11990 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
11991 treats the use of the operator @code{IN}, or the use of operators
11992 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
11993 @code{<=}, and @code{>=} on sets as an error.
11997 @node Built-In Func/Proc
11998 @subsubsection Built-in Functions and Procedures
11999 @cindex Modula-2 built-ins
12001 Modula-2 also makes available several built-in procedures and functions.
12002 In describing these, the following metavariables are used:
12007 represents an @code{ARRAY} variable.
12010 represents a @code{CHAR} constant or variable.
12013 represents a variable or constant of integral type.
12016 represents an identifier that belongs to a set. Generally used in the
12017 same function with the metavariable @var{s}. The type of @var{s} should
12018 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12021 represents a variable or constant of integral or floating-point type.
12024 represents a variable or constant of floating-point type.
12030 represents a variable.
12033 represents a variable or constant of one of many types. See the
12034 explanation of the function for details.
12037 All Modula-2 built-in procedures also return a result, described below.
12041 Returns the absolute value of @var{n}.
12044 If @var{c} is a lower case letter, it returns its upper case
12045 equivalent, otherwise it returns its argument.
12048 Returns the character whose ordinal value is @var{i}.
12051 Decrements the value in the variable @var{v} by one. Returns the new value.
12053 @item DEC(@var{v},@var{i})
12054 Decrements the value in the variable @var{v} by @var{i}. Returns the
12057 @item EXCL(@var{m},@var{s})
12058 Removes the element @var{m} from the set @var{s}. Returns the new
12061 @item FLOAT(@var{i})
12062 Returns the floating point equivalent of the integer @var{i}.
12064 @item HIGH(@var{a})
12065 Returns the index of the last member of @var{a}.
12068 Increments the value in the variable @var{v} by one. Returns the new value.
12070 @item INC(@var{v},@var{i})
12071 Increments the value in the variable @var{v} by @var{i}. Returns the
12074 @item INCL(@var{m},@var{s})
12075 Adds the element @var{m} to the set @var{s} if it is not already
12076 there. Returns the new set.
12079 Returns the maximum value of the type @var{t}.
12082 Returns the minimum value of the type @var{t}.
12085 Returns boolean TRUE if @var{i} is an odd number.
12088 Returns the ordinal value of its argument. For example, the ordinal
12089 value of a character is its @sc{ascii} value (on machines supporting the
12090 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12091 integral, character and enumerated types.
12093 @item SIZE(@var{x})
12094 Returns the size of its argument. @var{x} can be a variable or a type.
12096 @item TRUNC(@var{r})
12097 Returns the integral part of @var{r}.
12099 @item TSIZE(@var{x})
12100 Returns the size of its argument. @var{x} can be a variable or a type.
12102 @item VAL(@var{t},@var{i})
12103 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12107 @emph{Warning:} Sets and their operations are not yet supported, so
12108 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12112 @cindex Modula-2 constants
12114 @subsubsection Constants
12116 @value{GDBN} allows you to express the constants of Modula-2 in the following
12122 Integer constants are simply a sequence of digits. When used in an
12123 expression, a constant is interpreted to be type-compatible with the
12124 rest of the expression. Hexadecimal integers are specified by a
12125 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12128 Floating point constants appear as a sequence of digits, followed by a
12129 decimal point and another sequence of digits. An optional exponent can
12130 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12131 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12132 digits of the floating point constant must be valid decimal (base 10)
12136 Character constants consist of a single character enclosed by a pair of
12137 like quotes, either single (@code{'}) or double (@code{"}). They may
12138 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12139 followed by a @samp{C}.
12142 String constants consist of a sequence of characters enclosed by a
12143 pair of like quotes, either single (@code{'}) or double (@code{"}).
12144 Escape sequences in the style of C are also allowed. @xref{C
12145 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12149 Enumerated constants consist of an enumerated identifier.
12152 Boolean constants consist of the identifiers @code{TRUE} and
12156 Pointer constants consist of integral values only.
12159 Set constants are not yet supported.
12163 @subsubsection Modula-2 Types
12164 @cindex Modula-2 types
12166 Currently @value{GDBN} can print the following data types in Modula-2
12167 syntax: array types, record types, set types, pointer types, procedure
12168 types, enumerated types, subrange types and base types. You can also
12169 print the contents of variables declared using these type.
12170 This section gives a number of simple source code examples together with
12171 sample @value{GDBN} sessions.
12173 The first example contains the following section of code:
12182 and you can request @value{GDBN} to interrogate the type and value of
12183 @code{r} and @code{s}.
12186 (@value{GDBP}) print s
12188 (@value{GDBP}) ptype s
12190 (@value{GDBP}) print r
12192 (@value{GDBP}) ptype r
12197 Likewise if your source code declares @code{s} as:
12201 s: SET ['A'..'Z'] ;
12205 then you may query the type of @code{s} by:
12208 (@value{GDBP}) ptype s
12209 type = SET ['A'..'Z']
12213 Note that at present you cannot interactively manipulate set
12214 expressions using the debugger.
12216 The following example shows how you might declare an array in Modula-2
12217 and how you can interact with @value{GDBN} to print its type and contents:
12221 s: ARRAY [-10..10] OF CHAR ;
12225 (@value{GDBP}) ptype s
12226 ARRAY [-10..10] OF CHAR
12229 Note that the array handling is not yet complete and although the type
12230 is printed correctly, expression handling still assumes that all
12231 arrays have a lower bound of zero and not @code{-10} as in the example
12234 Here are some more type related Modula-2 examples:
12238 colour = (blue, red, yellow, green) ;
12239 t = [blue..yellow] ;
12247 The @value{GDBN} interaction shows how you can query the data type
12248 and value of a variable.
12251 (@value{GDBP}) print s
12253 (@value{GDBP}) ptype t
12254 type = [blue..yellow]
12258 In this example a Modula-2 array is declared and its contents
12259 displayed. Observe that the contents are written in the same way as
12260 their @code{C} counterparts.
12264 s: ARRAY [1..5] OF CARDINAL ;
12270 (@value{GDBP}) print s
12271 $1 = @{1, 0, 0, 0, 0@}
12272 (@value{GDBP}) ptype s
12273 type = ARRAY [1..5] OF CARDINAL
12276 The Modula-2 language interface to @value{GDBN} also understands
12277 pointer types as shown in this example:
12281 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12288 and you can request that @value{GDBN} describes the type of @code{s}.
12291 (@value{GDBP}) ptype s
12292 type = POINTER TO ARRAY [1..5] OF CARDINAL
12295 @value{GDBN} handles compound types as we can see in this example.
12296 Here we combine array types, record types, pointer types and subrange
12307 myarray = ARRAY myrange OF CARDINAL ;
12308 myrange = [-2..2] ;
12310 s: POINTER TO ARRAY myrange OF foo ;
12314 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12318 (@value{GDBP}) ptype s
12319 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12322 f3 : ARRAY [-2..2] OF CARDINAL;
12327 @subsubsection Modula-2 Defaults
12328 @cindex Modula-2 defaults
12330 If type and range checking are set automatically by @value{GDBN}, they
12331 both default to @code{on} whenever the working language changes to
12332 Modula-2. This happens regardless of whether you or @value{GDBN}
12333 selected the working language.
12335 If you allow @value{GDBN} to set the language automatically, then entering
12336 code compiled from a file whose name ends with @file{.mod} sets the
12337 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12338 Infer the Source Language}, for further details.
12341 @subsubsection Deviations from Standard Modula-2
12342 @cindex Modula-2, deviations from
12344 A few changes have been made to make Modula-2 programs easier to debug.
12345 This is done primarily via loosening its type strictness:
12349 Unlike in standard Modula-2, pointer constants can be formed by
12350 integers. This allows you to modify pointer variables during
12351 debugging. (In standard Modula-2, the actual address contained in a
12352 pointer variable is hidden from you; it can only be modified
12353 through direct assignment to another pointer variable or expression that
12354 returned a pointer.)
12357 C escape sequences can be used in strings and characters to represent
12358 non-printable characters. @value{GDBN} prints out strings with these
12359 escape sequences embedded. Single non-printable characters are
12360 printed using the @samp{CHR(@var{nnn})} format.
12363 The assignment operator (@code{:=}) returns the value of its right-hand
12367 All built-in procedures both modify @emph{and} return their argument.
12371 @subsubsection Modula-2 Type and Range Checks
12372 @cindex Modula-2 checks
12375 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12378 @c FIXME remove warning when type/range checks added
12380 @value{GDBN} considers two Modula-2 variables type equivalent if:
12384 They are of types that have been declared equivalent via a @code{TYPE
12385 @var{t1} = @var{t2}} statement
12388 They have been declared on the same line. (Note: This is true of the
12389 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12392 As long as type checking is enabled, any attempt to combine variables
12393 whose types are not equivalent is an error.
12395 Range checking is done on all mathematical operations, assignment, array
12396 index bounds, and all built-in functions and procedures.
12399 @subsubsection The Scope Operators @code{::} and @code{.}
12401 @cindex @code{.}, Modula-2 scope operator
12402 @cindex colon, doubled as scope operator
12404 @vindex colon-colon@r{, in Modula-2}
12405 @c Info cannot handle :: but TeX can.
12408 @vindex ::@r{, in Modula-2}
12411 There are a few subtle differences between the Modula-2 scope operator
12412 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12417 @var{module} . @var{id}
12418 @var{scope} :: @var{id}
12422 where @var{scope} is the name of a module or a procedure,
12423 @var{module} the name of a module, and @var{id} is any declared
12424 identifier within your program, except another module.
12426 Using the @code{::} operator makes @value{GDBN} search the scope
12427 specified by @var{scope} for the identifier @var{id}. If it is not
12428 found in the specified scope, then @value{GDBN} searches all scopes
12429 enclosing the one specified by @var{scope}.
12431 Using the @code{.} operator makes @value{GDBN} search the current scope for
12432 the identifier specified by @var{id} that was imported from the
12433 definition module specified by @var{module}. With this operator, it is
12434 an error if the identifier @var{id} was not imported from definition
12435 module @var{module}, or if @var{id} is not an identifier in
12439 @subsubsection @value{GDBN} and Modula-2
12441 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12442 Five subcommands of @code{set print} and @code{show print} apply
12443 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12444 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12445 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12446 analogue in Modula-2.
12448 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12449 with any language, is not useful with Modula-2. Its
12450 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12451 created in Modula-2 as they can in C or C@t{++}. However, because an
12452 address can be specified by an integral constant, the construct
12453 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12455 @cindex @code{#} in Modula-2
12456 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12457 interpreted as the beginning of a comment. Use @code{<>} instead.
12463 The extensions made to @value{GDBN} for Ada only support
12464 output from the @sc{gnu} Ada (GNAT) compiler.
12465 Other Ada compilers are not currently supported, and
12466 attempting to debug executables produced by them is most likely
12470 @cindex expressions in Ada
12472 * Ada Mode Intro:: General remarks on the Ada syntax
12473 and semantics supported by Ada mode
12475 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12476 * Additions to Ada:: Extensions of the Ada expression syntax.
12477 * Stopping Before Main Program:: Debugging the program during elaboration.
12478 * Ada Tasks:: Listing and setting breakpoints in tasks.
12479 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12480 * Ada Glitches:: Known peculiarities of Ada mode.
12483 @node Ada Mode Intro
12484 @subsubsection Introduction
12485 @cindex Ada mode, general
12487 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12488 syntax, with some extensions.
12489 The philosophy behind the design of this subset is
12493 That @value{GDBN} should provide basic literals and access to operations for
12494 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12495 leaving more sophisticated computations to subprograms written into the
12496 program (which therefore may be called from @value{GDBN}).
12499 That type safety and strict adherence to Ada language restrictions
12500 are not particularly important to the @value{GDBN} user.
12503 That brevity is important to the @value{GDBN} user.
12506 Thus, for brevity, the debugger acts as if all names declared in
12507 user-written packages are directly visible, even if they are not visible
12508 according to Ada rules, thus making it unnecessary to fully qualify most
12509 names with their packages, regardless of context. Where this causes
12510 ambiguity, @value{GDBN} asks the user's intent.
12512 The debugger will start in Ada mode if it detects an Ada main program.
12513 As for other languages, it will enter Ada mode when stopped in a program that
12514 was translated from an Ada source file.
12516 While in Ada mode, you may use `@t{--}' for comments. This is useful
12517 mostly for documenting command files. The standard @value{GDBN} comment
12518 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12519 middle (to allow based literals).
12521 The debugger supports limited overloading. Given a subprogram call in which
12522 the function symbol has multiple definitions, it will use the number of
12523 actual parameters and some information about their types to attempt to narrow
12524 the set of definitions. It also makes very limited use of context, preferring
12525 procedures to functions in the context of the @code{call} command, and
12526 functions to procedures elsewhere.
12528 @node Omissions from Ada
12529 @subsubsection Omissions from Ada
12530 @cindex Ada, omissions from
12532 Here are the notable omissions from the subset:
12536 Only a subset of the attributes are supported:
12540 @t{'First}, @t{'Last}, and @t{'Length}
12541 on array objects (not on types and subtypes).
12544 @t{'Min} and @t{'Max}.
12547 @t{'Pos} and @t{'Val}.
12553 @t{'Range} on array objects (not subtypes), but only as the right
12554 operand of the membership (@code{in}) operator.
12557 @t{'Access}, @t{'Unchecked_Access}, and
12558 @t{'Unrestricted_Access} (a GNAT extension).
12566 @code{Characters.Latin_1} are not available and
12567 concatenation is not implemented. Thus, escape characters in strings are
12568 not currently available.
12571 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12572 equality of representations. They will generally work correctly
12573 for strings and arrays whose elements have integer or enumeration types.
12574 They may not work correctly for arrays whose element
12575 types have user-defined equality, for arrays of real values
12576 (in particular, IEEE-conformant floating point, because of negative
12577 zeroes and NaNs), and for arrays whose elements contain unused bits with
12578 indeterminate values.
12581 The other component-by-component array operations (@code{and}, @code{or},
12582 @code{xor}, @code{not}, and relational tests other than equality)
12583 are not implemented.
12586 @cindex array aggregates (Ada)
12587 @cindex record aggregates (Ada)
12588 @cindex aggregates (Ada)
12589 There is limited support for array and record aggregates. They are
12590 permitted only on the right sides of assignments, as in these examples:
12593 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12594 (@value{GDBP}) set An_Array := (1, others => 0)
12595 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12596 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12597 (@value{GDBP}) set A_Record := (1, "Peter", True);
12598 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12602 discriminant's value by assigning an aggregate has an
12603 undefined effect if that discriminant is used within the record.
12604 However, you can first modify discriminants by directly assigning to
12605 them (which normally would not be allowed in Ada), and then performing an
12606 aggregate assignment. For example, given a variable @code{A_Rec}
12607 declared to have a type such as:
12610 type Rec (Len : Small_Integer := 0) is record
12612 Vals : IntArray (1 .. Len);
12616 you can assign a value with a different size of @code{Vals} with two
12620 (@value{GDBP}) set A_Rec.Len := 4
12621 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
12624 As this example also illustrates, @value{GDBN} is very loose about the usual
12625 rules concerning aggregates. You may leave out some of the
12626 components of an array or record aggregate (such as the @code{Len}
12627 component in the assignment to @code{A_Rec} above); they will retain their
12628 original values upon assignment. You may freely use dynamic values as
12629 indices in component associations. You may even use overlapping or
12630 redundant component associations, although which component values are
12631 assigned in such cases is not defined.
12634 Calls to dispatching subprograms are not implemented.
12637 The overloading algorithm is much more limited (i.e., less selective)
12638 than that of real Ada. It makes only limited use of the context in
12639 which a subexpression appears to resolve its meaning, and it is much
12640 looser in its rules for allowing type matches. As a result, some
12641 function calls will be ambiguous, and the user will be asked to choose
12642 the proper resolution.
12645 The @code{new} operator is not implemented.
12648 Entry calls are not implemented.
12651 Aside from printing, arithmetic operations on the native VAX floating-point
12652 formats are not supported.
12655 It is not possible to slice a packed array.
12658 The names @code{True} and @code{False}, when not part of a qualified name,
12659 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
12661 Should your program
12662 redefine these names in a package or procedure (at best a dubious practice),
12663 you will have to use fully qualified names to access their new definitions.
12666 @node Additions to Ada
12667 @subsubsection Additions to Ada
12668 @cindex Ada, deviations from
12670 As it does for other languages, @value{GDBN} makes certain generic
12671 extensions to Ada (@pxref{Expressions}):
12675 If the expression @var{E} is a variable residing in memory (typically
12676 a local variable or array element) and @var{N} is a positive integer,
12677 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
12678 @var{N}-1 adjacent variables following it in memory as an array. In
12679 Ada, this operator is generally not necessary, since its prime use is
12680 in displaying parts of an array, and slicing will usually do this in
12681 Ada. However, there are occasional uses when debugging programs in
12682 which certain debugging information has been optimized away.
12685 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
12686 appears in function or file @var{B}.'' When @var{B} is a file name,
12687 you must typically surround it in single quotes.
12690 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
12691 @var{type} that appears at address @var{addr}.''
12694 A name starting with @samp{$} is a convenience variable
12695 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
12698 In addition, @value{GDBN} provides a few other shortcuts and outright
12699 additions specific to Ada:
12703 The assignment statement is allowed as an expression, returning
12704 its right-hand operand as its value. Thus, you may enter
12707 (@value{GDBP}) set x := y + 3
12708 (@value{GDBP}) print A(tmp := y + 1)
12712 The semicolon is allowed as an ``operator,'' returning as its value
12713 the value of its right-hand operand.
12714 This allows, for example,
12715 complex conditional breaks:
12718 (@value{GDBP}) break f
12719 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
12723 Rather than use catenation and symbolic character names to introduce special
12724 characters into strings, one may instead use a special bracket notation,
12725 which is also used to print strings. A sequence of characters of the form
12726 @samp{["@var{XX}"]} within a string or character literal denotes the
12727 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
12728 sequence of characters @samp{["""]} also denotes a single quotation mark
12729 in strings. For example,
12731 "One line.["0a"]Next line.["0a"]"
12734 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
12738 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
12739 @t{'Max} is optional (and is ignored in any case). For example, it is valid
12743 (@value{GDBP}) print 'max(x, y)
12747 When printing arrays, @value{GDBN} uses positional notation when the
12748 array has a lower bound of 1, and uses a modified named notation otherwise.
12749 For example, a one-dimensional array of three integers with a lower bound
12750 of 3 might print as
12757 That is, in contrast to valid Ada, only the first component has a @code{=>}
12761 You may abbreviate attributes in expressions with any unique,
12762 multi-character subsequence of
12763 their names (an exact match gets preference).
12764 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
12765 in place of @t{a'length}.
12768 @cindex quoting Ada internal identifiers
12769 Since Ada is case-insensitive, the debugger normally maps identifiers you type
12770 to lower case. The GNAT compiler uses upper-case characters for
12771 some of its internal identifiers, which are normally of no interest to users.
12772 For the rare occasions when you actually have to look at them,
12773 enclose them in angle brackets to avoid the lower-case mapping.
12776 (@value{GDBP}) print <JMPBUF_SAVE>[0]
12780 Printing an object of class-wide type or dereferencing an
12781 access-to-class-wide value will display all the components of the object's
12782 specific type (as indicated by its run-time tag). Likewise, component
12783 selection on such a value will operate on the specific type of the
12788 @node Stopping Before Main Program
12789 @subsubsection Stopping at the Very Beginning
12791 @cindex breakpointing Ada elaboration code
12792 It is sometimes necessary to debug the program during elaboration, and
12793 before reaching the main procedure.
12794 As defined in the Ada Reference
12795 Manual, the elaboration code is invoked from a procedure called
12796 @code{adainit}. To run your program up to the beginning of
12797 elaboration, simply use the following two commands:
12798 @code{tbreak adainit} and @code{run}.
12801 @subsubsection Extensions for Ada Tasks
12802 @cindex Ada, tasking
12804 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
12805 @value{GDBN} provides the following task-related commands:
12810 This command shows a list of current Ada tasks, as in the following example:
12817 (@value{GDBP}) info tasks
12818 ID TID P-ID Pri State Name
12819 1 8088000 0 15 Child Activation Wait main_task
12820 2 80a4000 1 15 Accept Statement b
12821 3 809a800 1 15 Child Activation Wait a
12822 * 4 80ae800 3 15 Runnable c
12827 In this listing, the asterisk before the last task indicates it to be the
12828 task currently being inspected.
12832 Represents @value{GDBN}'s internal task number.
12838 The parent's task ID (@value{GDBN}'s internal task number).
12841 The base priority of the task.
12844 Current state of the task.
12848 The task has been created but has not been activated. It cannot be
12852 The task is not blocked for any reason known to Ada. (It may be waiting
12853 for a mutex, though.) It is conceptually "executing" in normal mode.
12856 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
12857 that were waiting on terminate alternatives have been awakened and have
12858 terminated themselves.
12860 @item Child Activation Wait
12861 The task is waiting for created tasks to complete activation.
12863 @item Accept Statement
12864 The task is waiting on an accept or selective wait statement.
12866 @item Waiting on entry call
12867 The task is waiting on an entry call.
12869 @item Async Select Wait
12870 The task is waiting to start the abortable part of an asynchronous
12874 The task is waiting on a select statement with only a delay
12877 @item Child Termination Wait
12878 The task is sleeping having completed a master within itself, and is
12879 waiting for the tasks dependent on that master to become terminated or
12880 waiting on a terminate Phase.
12882 @item Wait Child in Term Alt
12883 The task is sleeping waiting for tasks on terminate alternatives to
12884 finish terminating.
12886 @item Accepting RV with @var{taskno}
12887 The task is accepting a rendez-vous with the task @var{taskno}.
12891 Name of the task in the program.
12895 @kindex info task @var{taskno}
12896 @item info task @var{taskno}
12897 This command shows detailled informations on the specified task, as in
12898 the following example:
12903 (@value{GDBP}) info tasks
12904 ID TID P-ID Pri State Name
12905 1 8077880 0 15 Child Activation Wait main_task
12906 * 2 807c468 1 15 Runnable task_1
12907 (@value{GDBP}) info task 2
12908 Ada Task: 0x807c468
12911 Parent: 1 (main_task)
12917 @kindex task@r{ (Ada)}
12918 @cindex current Ada task ID
12919 This command prints the ID of the current task.
12925 (@value{GDBP}) info tasks
12926 ID TID P-ID Pri State Name
12927 1 8077870 0 15 Child Activation Wait main_task
12928 * 2 807c458 1 15 Runnable t
12929 (@value{GDBP}) task
12930 [Current task is 2]
12933 @item task @var{taskno}
12934 @cindex Ada task switching
12935 This command is like the @code{thread @var{threadno}}
12936 command (@pxref{Threads}). It switches the context of debugging
12937 from the current task to the given task.
12943 (@value{GDBP}) info tasks
12944 ID TID P-ID Pri State Name
12945 1 8077870 0 15 Child Activation Wait main_task
12946 * 2 807c458 1 15 Runnable t
12947 (@value{GDBP}) task 1
12948 [Switching to task 1]
12949 #0 0x8067726 in pthread_cond_wait ()
12951 #0 0x8067726 in pthread_cond_wait ()
12952 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
12953 #2 0x805cb63 in system.task_primitives.operations.sleep ()
12954 #3 0x806153e in system.tasking.stages.activate_tasks ()
12955 #4 0x804aacc in un () at un.adb:5
12958 @item break @var{linespec} task @var{taskno}
12959 @itemx break @var{linespec} task @var{taskno} if @dots{}
12960 @cindex breakpoints and tasks, in Ada
12961 @cindex task breakpoints, in Ada
12962 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
12963 These commands are like the @code{break @dots{} thread @dots{}}
12964 command (@pxref{Thread Stops}).
12965 @var{linespec} specifies source lines, as described
12966 in @ref{Specify Location}.
12968 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
12969 to specify that you only want @value{GDBN} to stop the program when a
12970 particular Ada task reaches this breakpoint. @var{taskno} is one of the
12971 numeric task identifiers assigned by @value{GDBN}, shown in the first
12972 column of the @samp{info tasks} display.
12974 If you do not specify @samp{task @var{taskno}} when you set a
12975 breakpoint, the breakpoint applies to @emph{all} tasks of your
12978 You can use the @code{task} qualifier on conditional breakpoints as
12979 well; in this case, place @samp{task @var{taskno}} before the
12980 breakpoint condition (before the @code{if}).
12988 (@value{GDBP}) info tasks
12989 ID TID P-ID Pri State Name
12990 1 140022020 0 15 Child Activation Wait main_task
12991 2 140045060 1 15 Accept/Select Wait t2
12992 3 140044840 1 15 Runnable t1
12993 * 4 140056040 1 15 Runnable t3
12994 (@value{GDBP}) b 15 task 2
12995 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
12996 (@value{GDBP}) cont
13001 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13003 (@value{GDBP}) info tasks
13004 ID TID P-ID Pri State Name
13005 1 140022020 0 15 Child Activation Wait main_task
13006 * 2 140045060 1 15 Runnable t2
13007 3 140044840 1 15 Runnable t1
13008 4 140056040 1 15 Delay Sleep t3
13012 @node Ada Tasks and Core Files
13013 @subsubsection Tasking Support when Debugging Core Files
13014 @cindex Ada tasking and core file debugging
13016 When inspecting a core file, as opposed to debugging a live program,
13017 tasking support may be limited or even unavailable, depending on
13018 the platform being used.
13019 For instance, on x86-linux, the list of tasks is available, but task
13020 switching is not supported. On Tru64, however, task switching will work
13023 On certain platforms, including Tru64, the debugger needs to perform some
13024 memory writes in order to provide Ada tasking support. When inspecting
13025 a core file, this means that the core file must be opened with read-write
13026 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13027 Under these circumstances, you should make a backup copy of the core
13028 file before inspecting it with @value{GDBN}.
13031 @subsubsection Known Peculiarities of Ada Mode
13032 @cindex Ada, problems
13034 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13035 we know of several problems with and limitations of Ada mode in
13037 some of which will be fixed with planned future releases of the debugger
13038 and the GNU Ada compiler.
13042 Currently, the debugger
13043 has insufficient information to determine whether certain pointers represent
13044 pointers to objects or the objects themselves.
13045 Thus, the user may have to tack an extra @code{.all} after an expression
13046 to get it printed properly.
13049 Static constants that the compiler chooses not to materialize as objects in
13050 storage are invisible to the debugger.
13053 Named parameter associations in function argument lists are ignored (the
13054 argument lists are treated as positional).
13057 Many useful library packages are currently invisible to the debugger.
13060 Fixed-point arithmetic, conversions, input, and output is carried out using
13061 floating-point arithmetic, and may give results that only approximate those on
13065 The GNAT compiler never generates the prefix @code{Standard} for any of
13066 the standard symbols defined by the Ada language. @value{GDBN} knows about
13067 this: it will strip the prefix from names when you use it, and will never
13068 look for a name you have so qualified among local symbols, nor match against
13069 symbols in other packages or subprograms. If you have
13070 defined entities anywhere in your program other than parameters and
13071 local variables whose simple names match names in @code{Standard},
13072 GNAT's lack of qualification here can cause confusion. When this happens,
13073 you can usually resolve the confusion
13074 by qualifying the problematic names with package
13075 @code{Standard} explicitly.
13078 Older versions of the compiler sometimes generate erroneous debugging
13079 information, resulting in the debugger incorrectly printing the value
13080 of affected entities. In some cases, the debugger is able to work
13081 around an issue automatically. In other cases, the debugger is able
13082 to work around the issue, but the work-around has to be specifically
13085 @kindex set ada trust-PAD-over-XVS
13086 @kindex show ada trust-PAD-over-XVS
13089 @item set ada trust-PAD-over-XVS on
13090 Configure GDB to strictly follow the GNAT encoding when computing the
13091 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13092 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13093 a complete description of the encoding used by the GNAT compiler).
13094 This is the default.
13096 @item set ada trust-PAD-over-XVS off
13097 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13098 sometimes prints the wrong value for certain entities, changing @code{ada
13099 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13100 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13101 @code{off}, but this incurs a slight performance penalty, so it is
13102 recommended to leave this setting to @code{on} unless necessary.
13106 @node Unsupported Languages
13107 @section Unsupported Languages
13109 @cindex unsupported languages
13110 @cindex minimal language
13111 In addition to the other fully-supported programming languages,
13112 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13113 It does not represent a real programming language, but provides a set
13114 of capabilities close to what the C or assembly languages provide.
13115 This should allow most simple operations to be performed while debugging
13116 an application that uses a language currently not supported by @value{GDBN}.
13118 If the language is set to @code{auto}, @value{GDBN} will automatically
13119 select this language if the current frame corresponds to an unsupported
13123 @chapter Examining the Symbol Table
13125 The commands described in this chapter allow you to inquire about the
13126 symbols (names of variables, functions and types) defined in your
13127 program. This information is inherent in the text of your program and
13128 does not change as your program executes. @value{GDBN} finds it in your
13129 program's symbol table, in the file indicated when you started @value{GDBN}
13130 (@pxref{File Options, ,Choosing Files}), or by one of the
13131 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13133 @cindex symbol names
13134 @cindex names of symbols
13135 @cindex quoting names
13136 Occasionally, you may need to refer to symbols that contain unusual
13137 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13138 most frequent case is in referring to static variables in other
13139 source files (@pxref{Variables,,Program Variables}). File names
13140 are recorded in object files as debugging symbols, but @value{GDBN} would
13141 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13142 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13143 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13150 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13153 @cindex case-insensitive symbol names
13154 @cindex case sensitivity in symbol names
13155 @kindex set case-sensitive
13156 @item set case-sensitive on
13157 @itemx set case-sensitive off
13158 @itemx set case-sensitive auto
13159 Normally, when @value{GDBN} looks up symbols, it matches their names
13160 with case sensitivity determined by the current source language.
13161 Occasionally, you may wish to control that. The command @code{set
13162 case-sensitive} lets you do that by specifying @code{on} for
13163 case-sensitive matches or @code{off} for case-insensitive ones. If
13164 you specify @code{auto}, case sensitivity is reset to the default
13165 suitable for the source language. The default is case-sensitive
13166 matches for all languages except for Fortran, for which the default is
13167 case-insensitive matches.
13169 @kindex show case-sensitive
13170 @item show case-sensitive
13171 This command shows the current setting of case sensitivity for symbols
13174 @kindex info address
13175 @cindex address of a symbol
13176 @item info address @var{symbol}
13177 Describe where the data for @var{symbol} is stored. For a register
13178 variable, this says which register it is kept in. For a non-register
13179 local variable, this prints the stack-frame offset at which the variable
13182 Note the contrast with @samp{print &@var{symbol}}, which does not work
13183 at all for a register variable, and for a stack local variable prints
13184 the exact address of the current instantiation of the variable.
13186 @kindex info symbol
13187 @cindex symbol from address
13188 @cindex closest symbol and offset for an address
13189 @item info symbol @var{addr}
13190 Print the name of a symbol which is stored at the address @var{addr}.
13191 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13192 nearest symbol and an offset from it:
13195 (@value{GDBP}) info symbol 0x54320
13196 _initialize_vx + 396 in section .text
13200 This is the opposite of the @code{info address} command. You can use
13201 it to find out the name of a variable or a function given its address.
13203 For dynamically linked executables, the name of executable or shared
13204 library containing the symbol is also printed:
13207 (@value{GDBP}) info symbol 0x400225
13208 _start + 5 in section .text of /tmp/a.out
13209 (@value{GDBP}) info symbol 0x2aaaac2811cf
13210 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13214 @item whatis [@var{arg}]
13215 Print the data type of @var{arg}, which can be either an expression or
13216 a data type. With no argument, print the data type of @code{$}, the
13217 last value in the value history. If @var{arg} is an expression, it is
13218 not actually evaluated, and any side-effecting operations (such as
13219 assignments or function calls) inside it do not take place. If
13220 @var{arg} is a type name, it may be the name of a type or typedef, or
13221 for C code it may have the form @samp{class @var{class-name}},
13222 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13223 @samp{enum @var{enum-tag}}.
13224 @xref{Expressions, ,Expressions}.
13227 @item ptype [@var{arg}]
13228 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13229 detailed description of the type, instead of just the name of the type.
13230 @xref{Expressions, ,Expressions}.
13232 For example, for this variable declaration:
13235 struct complex @{double real; double imag;@} v;
13239 the two commands give this output:
13243 (@value{GDBP}) whatis v
13244 type = struct complex
13245 (@value{GDBP}) ptype v
13246 type = struct complex @{
13254 As with @code{whatis}, using @code{ptype} without an argument refers to
13255 the type of @code{$}, the last value in the value history.
13257 @cindex incomplete type
13258 Sometimes, programs use opaque data types or incomplete specifications
13259 of complex data structure. If the debug information included in the
13260 program does not allow @value{GDBN} to display a full declaration of
13261 the data type, it will say @samp{<incomplete type>}. For example,
13262 given these declarations:
13266 struct foo *fooptr;
13270 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13273 (@value{GDBP}) ptype foo
13274 $1 = <incomplete type>
13278 ``Incomplete type'' is C terminology for data types that are not
13279 completely specified.
13282 @item info types @var{regexp}
13284 Print a brief description of all types whose names match the regular
13285 expression @var{regexp} (or all types in your program, if you supply
13286 no argument). Each complete typename is matched as though it were a
13287 complete line; thus, @samp{i type value} gives information on all
13288 types in your program whose names include the string @code{value}, but
13289 @samp{i type ^value$} gives information only on types whose complete
13290 name is @code{value}.
13292 This command differs from @code{ptype} in two ways: first, like
13293 @code{whatis}, it does not print a detailed description; second, it
13294 lists all source files where a type is defined.
13297 @cindex local variables
13298 @item info scope @var{location}
13299 List all the variables local to a particular scope. This command
13300 accepts a @var{location} argument---a function name, a source line, or
13301 an address preceded by a @samp{*}, and prints all the variables local
13302 to the scope defined by that location. (@xref{Specify Location}, for
13303 details about supported forms of @var{location}.) For example:
13306 (@value{GDBP}) @b{info scope command_line_handler}
13307 Scope for command_line_handler:
13308 Symbol rl is an argument at stack/frame offset 8, length 4.
13309 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13310 Symbol linelength is in static storage at address 0x150a1c, length 4.
13311 Symbol p is a local variable in register $esi, length 4.
13312 Symbol p1 is a local variable in register $ebx, length 4.
13313 Symbol nline is a local variable in register $edx, length 4.
13314 Symbol repeat is a local variable at frame offset -8, length 4.
13318 This command is especially useful for determining what data to collect
13319 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13322 @kindex info source
13324 Show information about the current source file---that is, the source file for
13325 the function containing the current point of execution:
13328 the name of the source file, and the directory containing it,
13330 the directory it was compiled in,
13332 its length, in lines,
13334 which programming language it is written in,
13336 whether the executable includes debugging information for that file, and
13337 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13339 whether the debugging information includes information about
13340 preprocessor macros.
13344 @kindex info sources
13346 Print the names of all source files in your program for which there is
13347 debugging information, organized into two lists: files whose symbols
13348 have already been read, and files whose symbols will be read when needed.
13350 @kindex info functions
13351 @item info functions
13352 Print the names and data types of all defined functions.
13354 @item info functions @var{regexp}
13355 Print the names and data types of all defined functions
13356 whose names contain a match for regular expression @var{regexp}.
13357 Thus, @samp{info fun step} finds all functions whose names
13358 include @code{step}; @samp{info fun ^step} finds those whose names
13359 start with @code{step}. If a function name contains characters
13360 that conflict with the regular expression language (e.g.@:
13361 @samp{operator*()}), they may be quoted with a backslash.
13363 @kindex info variables
13364 @item info variables
13365 Print the names and data types of all variables that are defined
13366 outside of functions (i.e.@: excluding local variables).
13368 @item info variables @var{regexp}
13369 Print the names and data types of all variables (except for local
13370 variables) whose names contain a match for regular expression
13373 @kindex info classes
13374 @cindex Objective-C, classes and selectors
13376 @itemx info classes @var{regexp}
13377 Display all Objective-C classes in your program, or
13378 (with the @var{regexp} argument) all those matching a particular regular
13381 @kindex info selectors
13382 @item info selectors
13383 @itemx info selectors @var{regexp}
13384 Display all Objective-C selectors in your program, or
13385 (with the @var{regexp} argument) all those matching a particular regular
13389 This was never implemented.
13390 @kindex info methods
13392 @itemx info methods @var{regexp}
13393 The @code{info methods} command permits the user to examine all defined
13394 methods within C@t{++} program, or (with the @var{regexp} argument) a
13395 specific set of methods found in the various C@t{++} classes. Many
13396 C@t{++} classes provide a large number of methods. Thus, the output
13397 from the @code{ptype} command can be overwhelming and hard to use. The
13398 @code{info-methods} command filters the methods, printing only those
13399 which match the regular-expression @var{regexp}.
13402 @cindex reloading symbols
13403 Some systems allow individual object files that make up your program to
13404 be replaced without stopping and restarting your program. For example,
13405 in VxWorks you can simply recompile a defective object file and keep on
13406 running. If you are running on one of these systems, you can allow
13407 @value{GDBN} to reload the symbols for automatically relinked modules:
13410 @kindex set symbol-reloading
13411 @item set symbol-reloading on
13412 Replace symbol definitions for the corresponding source file when an
13413 object file with a particular name is seen again.
13415 @item set symbol-reloading off
13416 Do not replace symbol definitions when encountering object files of the
13417 same name more than once. This is the default state; if you are not
13418 running on a system that permits automatic relinking of modules, you
13419 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
13420 may discard symbols when linking large programs, that may contain
13421 several modules (from different directories or libraries) with the same
13424 @kindex show symbol-reloading
13425 @item show symbol-reloading
13426 Show the current @code{on} or @code{off} setting.
13429 @cindex opaque data types
13430 @kindex set opaque-type-resolution
13431 @item set opaque-type-resolution on
13432 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
13433 declared as a pointer to a @code{struct}, @code{class}, or
13434 @code{union}---for example, @code{struct MyType *}---that is used in one
13435 source file although the full declaration of @code{struct MyType} is in
13436 another source file. The default is on.
13438 A change in the setting of this subcommand will not take effect until
13439 the next time symbols for a file are loaded.
13441 @item set opaque-type-resolution off
13442 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13443 is printed as follows:
13445 @{<no data fields>@}
13448 @kindex show opaque-type-resolution
13449 @item show opaque-type-resolution
13450 Show whether opaque types are resolved or not.
13452 @kindex maint print symbols
13453 @cindex symbol dump
13454 @kindex maint print psymbols
13455 @cindex partial symbol dump
13456 @item maint print symbols @var{filename}
13457 @itemx maint print psymbols @var{filename}
13458 @itemx maint print msymbols @var{filename}
13459 Write a dump of debugging symbol data into the file @var{filename}.
13460 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13461 symbols with debugging data are included. If you use @samp{maint print
13462 symbols}, @value{GDBN} includes all the symbols for which it has already
13463 collected full details: that is, @var{filename} reflects symbols for
13464 only those files whose symbols @value{GDBN} has read. You can use the
13465 command @code{info sources} to find out which files these are. If you
13466 use @samp{maint print psymbols} instead, the dump shows information about
13467 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13468 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13469 @samp{maint print msymbols} dumps just the minimal symbol information
13470 required for each object file from which @value{GDBN} has read some symbols.
13471 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13472 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13474 @kindex maint info symtabs
13475 @kindex maint info psymtabs
13476 @cindex listing @value{GDBN}'s internal symbol tables
13477 @cindex symbol tables, listing @value{GDBN}'s internal
13478 @cindex full symbol tables, listing @value{GDBN}'s internal
13479 @cindex partial symbol tables, listing @value{GDBN}'s internal
13480 @item maint info symtabs @r{[} @var{regexp} @r{]}
13481 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13483 List the @code{struct symtab} or @code{struct partial_symtab}
13484 structures whose names match @var{regexp}. If @var{regexp} is not
13485 given, list them all. The output includes expressions which you can
13486 copy into a @value{GDBN} debugging this one to examine a particular
13487 structure in more detail. For example:
13490 (@value{GDBP}) maint info psymtabs dwarf2read
13491 @{ objfile /home/gnu/build/gdb/gdb
13492 ((struct objfile *) 0x82e69d0)
13493 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13494 ((struct partial_symtab *) 0x8474b10)
13497 text addresses 0x814d3c8 -- 0x8158074
13498 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13499 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13500 dependencies (none)
13503 (@value{GDBP}) maint info symtabs
13507 We see that there is one partial symbol table whose filename contains
13508 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13509 and we see that @value{GDBN} has not read in any symtabs yet at all.
13510 If we set a breakpoint on a function, that will cause @value{GDBN} to
13511 read the symtab for the compilation unit containing that function:
13514 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13515 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13517 (@value{GDBP}) maint info symtabs
13518 @{ objfile /home/gnu/build/gdb/gdb
13519 ((struct objfile *) 0x82e69d0)
13520 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13521 ((struct symtab *) 0x86c1f38)
13524 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13525 linetable ((struct linetable *) 0x8370fa0)
13526 debugformat DWARF 2
13535 @chapter Altering Execution
13537 Once you think you have found an error in your program, you might want to
13538 find out for certain whether correcting the apparent error would lead to
13539 correct results in the rest of the run. You can find the answer by
13540 experiment, using the @value{GDBN} features for altering execution of the
13543 For example, you can store new values into variables or memory
13544 locations, give your program a signal, restart it at a different
13545 address, or even return prematurely from a function.
13548 * Assignment:: Assignment to variables
13549 * Jumping:: Continuing at a different address
13550 * Signaling:: Giving your program a signal
13551 * Returning:: Returning from a function
13552 * Calling:: Calling your program's functions
13553 * Patching:: Patching your program
13557 @section Assignment to Variables
13560 @cindex setting variables
13561 To alter the value of a variable, evaluate an assignment expression.
13562 @xref{Expressions, ,Expressions}. For example,
13569 stores the value 4 into the variable @code{x}, and then prints the
13570 value of the assignment expression (which is 4).
13571 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13572 information on operators in supported languages.
13574 @kindex set variable
13575 @cindex variables, setting
13576 If you are not interested in seeing the value of the assignment, use the
13577 @code{set} command instead of the @code{print} command. @code{set} is
13578 really the same as @code{print} except that the expression's value is
13579 not printed and is not put in the value history (@pxref{Value History,
13580 ,Value History}). The expression is evaluated only for its effects.
13582 If the beginning of the argument string of the @code{set} command
13583 appears identical to a @code{set} subcommand, use the @code{set
13584 variable} command instead of just @code{set}. This command is identical
13585 to @code{set} except for its lack of subcommands. For example, if your
13586 program has a variable @code{width}, you get an error if you try to set
13587 a new value with just @samp{set width=13}, because @value{GDBN} has the
13588 command @code{set width}:
13591 (@value{GDBP}) whatis width
13593 (@value{GDBP}) p width
13595 (@value{GDBP}) set width=47
13596 Invalid syntax in expression.
13600 The invalid expression, of course, is @samp{=47}. In
13601 order to actually set the program's variable @code{width}, use
13604 (@value{GDBP}) set var width=47
13607 Because the @code{set} command has many subcommands that can conflict
13608 with the names of program variables, it is a good idea to use the
13609 @code{set variable} command instead of just @code{set}. For example, if
13610 your program has a variable @code{g}, you run into problems if you try
13611 to set a new value with just @samp{set g=4}, because @value{GDBN} has
13612 the command @code{set gnutarget}, abbreviated @code{set g}:
13616 (@value{GDBP}) whatis g
13620 (@value{GDBP}) set g=4
13624 The program being debugged has been started already.
13625 Start it from the beginning? (y or n) y
13626 Starting program: /home/smith/cc_progs/a.out
13627 "/home/smith/cc_progs/a.out": can't open to read symbols:
13628 Invalid bfd target.
13629 (@value{GDBP}) show g
13630 The current BFD target is "=4".
13635 The program variable @code{g} did not change, and you silently set the
13636 @code{gnutarget} to an invalid value. In order to set the variable
13640 (@value{GDBP}) set var g=4
13643 @value{GDBN} allows more implicit conversions in assignments than C; you can
13644 freely store an integer value into a pointer variable or vice versa,
13645 and you can convert any structure to any other structure that is the
13646 same length or shorter.
13647 @comment FIXME: how do structs align/pad in these conversions?
13648 @comment /doc@cygnus.com 18dec1990
13650 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
13651 construct to generate a value of specified type at a specified address
13652 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
13653 to memory location @code{0x83040} as an integer (which implies a certain size
13654 and representation in memory), and
13657 set @{int@}0x83040 = 4
13661 stores the value 4 into that memory location.
13664 @section Continuing at a Different Address
13666 Ordinarily, when you continue your program, you do so at the place where
13667 it stopped, with the @code{continue} command. You can instead continue at
13668 an address of your own choosing, with the following commands:
13672 @item jump @var{linespec}
13673 @itemx jump @var{location}
13674 Resume execution at line @var{linespec} or at address given by
13675 @var{location}. Execution stops again immediately if there is a
13676 breakpoint there. @xref{Specify Location}, for a description of the
13677 different forms of @var{linespec} and @var{location}. It is common
13678 practice to use the @code{tbreak} command in conjunction with
13679 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
13681 The @code{jump} command does not change the current stack frame, or
13682 the stack pointer, or the contents of any memory location or any
13683 register other than the program counter. If line @var{linespec} is in
13684 a different function from the one currently executing, the results may
13685 be bizarre if the two functions expect different patterns of arguments or
13686 of local variables. For this reason, the @code{jump} command requests
13687 confirmation if the specified line is not in the function currently
13688 executing. However, even bizarre results are predictable if you are
13689 well acquainted with the machine-language code of your program.
13692 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
13693 On many systems, you can get much the same effect as the @code{jump}
13694 command by storing a new value into the register @code{$pc}. The
13695 difference is that this does not start your program running; it only
13696 changes the address of where it @emph{will} run when you continue. For
13704 makes the next @code{continue} command or stepping command execute at
13705 address @code{0x485}, rather than at the address where your program stopped.
13706 @xref{Continuing and Stepping, ,Continuing and Stepping}.
13708 The most common occasion to use the @code{jump} command is to back
13709 up---perhaps with more breakpoints set---over a portion of a program
13710 that has already executed, in order to examine its execution in more
13715 @section Giving your Program a Signal
13716 @cindex deliver a signal to a program
13720 @item signal @var{signal}
13721 Resume execution where your program stopped, but immediately give it the
13722 signal @var{signal}. @var{signal} can be the name or the number of a
13723 signal. For example, on many systems @code{signal 2} and @code{signal
13724 SIGINT} are both ways of sending an interrupt signal.
13726 Alternatively, if @var{signal} is zero, continue execution without
13727 giving a signal. This is useful when your program stopped on account of
13728 a signal and would ordinary see the signal when resumed with the
13729 @code{continue} command; @samp{signal 0} causes it to resume without a
13732 @code{signal} does not repeat when you press @key{RET} a second time
13733 after executing the command.
13737 Invoking the @code{signal} command is not the same as invoking the
13738 @code{kill} utility from the shell. Sending a signal with @code{kill}
13739 causes @value{GDBN} to decide what to do with the signal depending on
13740 the signal handling tables (@pxref{Signals}). The @code{signal} command
13741 passes the signal directly to your program.
13745 @section Returning from a Function
13748 @cindex returning from a function
13751 @itemx return @var{expression}
13752 You can cancel execution of a function call with the @code{return}
13753 command. If you give an
13754 @var{expression} argument, its value is used as the function's return
13758 When you use @code{return}, @value{GDBN} discards the selected stack frame
13759 (and all frames within it). You can think of this as making the
13760 discarded frame return prematurely. If you wish to specify a value to
13761 be returned, give that value as the argument to @code{return}.
13763 This pops the selected stack frame (@pxref{Selection, ,Selecting a
13764 Frame}), and any other frames inside of it, leaving its caller as the
13765 innermost remaining frame. That frame becomes selected. The
13766 specified value is stored in the registers used for returning values
13769 The @code{return} command does not resume execution; it leaves the
13770 program stopped in the state that would exist if the function had just
13771 returned. In contrast, the @code{finish} command (@pxref{Continuing
13772 and Stepping, ,Continuing and Stepping}) resumes execution until the
13773 selected stack frame returns naturally.
13775 @value{GDBN} needs to know how the @var{expression} argument should be set for
13776 the inferior. The concrete registers assignment depends on the OS ABI and the
13777 type being returned by the selected stack frame. For example it is common for
13778 OS ABI to return floating point values in FPU registers while integer values in
13779 CPU registers. Still some ABIs return even floating point values in CPU
13780 registers. Larger integer widths (such as @code{long long int}) also have
13781 specific placement rules. @value{GDBN} already knows the OS ABI from its
13782 current target so it needs to find out also the type being returned to make the
13783 assignment into the right register(s).
13785 Normally, the selected stack frame has debug info. @value{GDBN} will always
13786 use the debug info instead of the implicit type of @var{expression} when the
13787 debug info is available. For example, if you type @kbd{return -1}, and the
13788 function in the current stack frame is declared to return a @code{long long
13789 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
13790 into a @code{long long int}:
13793 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
13795 (@value{GDBP}) return -1
13796 Make func return now? (y or n) y
13797 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
13798 43 printf ("result=%lld\n", func ());
13802 However, if the selected stack frame does not have a debug info, e.g., if the
13803 function was compiled without debug info, @value{GDBN} has to find out the type
13804 to return from user. Specifying a different type by mistake may set the value
13805 in different inferior registers than the caller code expects. For example,
13806 typing @kbd{return -1} with its implicit type @code{int} would set only a part
13807 of a @code{long long int} result for a debug info less function (on 32-bit
13808 architectures). Therefore the user is required to specify the return type by
13809 an appropriate cast explicitly:
13812 Breakpoint 2, 0x0040050b in func ()
13813 (@value{GDBP}) return -1
13814 Return value type not available for selected stack frame.
13815 Please use an explicit cast of the value to return.
13816 (@value{GDBP}) return (long long int) -1
13817 Make selected stack frame return now? (y or n) y
13818 #0 0x00400526 in main ()
13823 @section Calling Program Functions
13826 @cindex calling functions
13827 @cindex inferior functions, calling
13828 @item print @var{expr}
13829 Evaluate the expression @var{expr} and display the resulting value.
13830 @var{expr} may include calls to functions in the program being
13834 @item call @var{expr}
13835 Evaluate the expression @var{expr} without displaying @code{void}
13838 You can use this variant of the @code{print} command if you want to
13839 execute a function from your program that does not return anything
13840 (a.k.a.@: @dfn{a void function}), but without cluttering the output
13841 with @code{void} returned values that @value{GDBN} will otherwise
13842 print. If the result is not void, it is printed and saved in the
13846 It is possible for the function you call via the @code{print} or
13847 @code{call} command to generate a signal (e.g., if there's a bug in
13848 the function, or if you passed it incorrect arguments). What happens
13849 in that case is controlled by the @code{set unwindonsignal} command.
13851 Similarly, with a C@t{++} program it is possible for the function you
13852 call via the @code{print} or @code{call} command to generate an
13853 exception that is not handled due to the constraints of the dummy
13854 frame. In this case, any exception that is raised in the frame, but has
13855 an out-of-frame exception handler will not be found. GDB builds a
13856 dummy-frame for the inferior function call, and the unwinder cannot
13857 seek for exception handlers outside of this dummy-frame. What happens
13858 in that case is controlled by the
13859 @code{set unwind-on-terminating-exception} command.
13862 @item set unwindonsignal
13863 @kindex set unwindonsignal
13864 @cindex unwind stack in called functions
13865 @cindex call dummy stack unwinding
13866 Set unwinding of the stack if a signal is received while in a function
13867 that @value{GDBN} called in the program being debugged. If set to on,
13868 @value{GDBN} unwinds the stack it created for the call and restores
13869 the context to what it was before the call. If set to off (the
13870 default), @value{GDBN} stops in the frame where the signal was
13873 @item show unwindonsignal
13874 @kindex show unwindonsignal
13875 Show the current setting of stack unwinding in the functions called by
13878 @item set unwind-on-terminating-exception
13879 @kindex set unwind-on-terminating-exception
13880 @cindex unwind stack in called functions with unhandled exceptions
13881 @cindex call dummy stack unwinding on unhandled exception.
13882 Set unwinding of the stack if a C@t{++} exception is raised, but left
13883 unhandled while in a function that @value{GDBN} called in the program being
13884 debugged. If set to on (the default), @value{GDBN} unwinds the stack
13885 it created for the call and restores the context to what it was before
13886 the call. If set to off, @value{GDBN} the exception is delivered to
13887 the default C@t{++} exception handler and the inferior terminated.
13889 @item show unwind-on-terminating-exception
13890 @kindex show unwind-on-terminating-exception
13891 Show the current setting of stack unwinding in the functions called by
13896 @cindex weak alias functions
13897 Sometimes, a function you wish to call is actually a @dfn{weak alias}
13898 for another function. In such case, @value{GDBN} might not pick up
13899 the type information, including the types of the function arguments,
13900 which causes @value{GDBN} to call the inferior function incorrectly.
13901 As a result, the called function will function erroneously and may
13902 even crash. A solution to that is to use the name of the aliased
13906 @section Patching Programs
13908 @cindex patching binaries
13909 @cindex writing into executables
13910 @cindex writing into corefiles
13912 By default, @value{GDBN} opens the file containing your program's
13913 executable code (or the corefile) read-only. This prevents accidental
13914 alterations to machine code; but it also prevents you from intentionally
13915 patching your program's binary.
13917 If you'd like to be able to patch the binary, you can specify that
13918 explicitly with the @code{set write} command. For example, you might
13919 want to turn on internal debugging flags, or even to make emergency
13925 @itemx set write off
13926 If you specify @samp{set write on}, @value{GDBN} opens executable and
13927 core files for both reading and writing; if you specify @kbd{set write
13928 off} (the default), @value{GDBN} opens them read-only.
13930 If you have already loaded a file, you must load it again (using the
13931 @code{exec-file} or @code{core-file} command) after changing @code{set
13932 write}, for your new setting to take effect.
13936 Display whether executable files and core files are opened for writing
13937 as well as reading.
13941 @chapter @value{GDBN} Files
13943 @value{GDBN} needs to know the file name of the program to be debugged,
13944 both in order to read its symbol table and in order to start your
13945 program. To debug a core dump of a previous run, you must also tell
13946 @value{GDBN} the name of the core dump file.
13949 * Files:: Commands to specify files
13950 * Separate Debug Files:: Debugging information in separate files
13951 * Symbol Errors:: Errors reading symbol files
13952 * Data Files:: GDB data files
13956 @section Commands to Specify Files
13958 @cindex symbol table
13959 @cindex core dump file
13961 You may want to specify executable and core dump file names. The usual
13962 way to do this is at start-up time, using the arguments to
13963 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
13964 Out of @value{GDBN}}).
13966 Occasionally it is necessary to change to a different file during a
13967 @value{GDBN} session. Or you may run @value{GDBN} and forget to
13968 specify a file you want to use. Or you are debugging a remote target
13969 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
13970 Program}). In these situations the @value{GDBN} commands to specify
13971 new files are useful.
13974 @cindex executable file
13976 @item file @var{filename}
13977 Use @var{filename} as the program to be debugged. It is read for its
13978 symbols and for the contents of pure memory. It is also the program
13979 executed when you use the @code{run} command. If you do not specify a
13980 directory and the file is not found in the @value{GDBN} working directory,
13981 @value{GDBN} uses the environment variable @code{PATH} as a list of
13982 directories to search, just as the shell does when looking for a program
13983 to run. You can change the value of this variable, for both @value{GDBN}
13984 and your program, using the @code{path} command.
13986 @cindex unlinked object files
13987 @cindex patching object files
13988 You can load unlinked object @file{.o} files into @value{GDBN} using
13989 the @code{file} command. You will not be able to ``run'' an object
13990 file, but you can disassemble functions and inspect variables. Also,
13991 if the underlying BFD functionality supports it, you could use
13992 @kbd{gdb -write} to patch object files using this technique. Note
13993 that @value{GDBN} can neither interpret nor modify relocations in this
13994 case, so branches and some initialized variables will appear to go to
13995 the wrong place. But this feature is still handy from time to time.
13998 @code{file} with no argument makes @value{GDBN} discard any information it
13999 has on both executable file and the symbol table.
14002 @item exec-file @r{[} @var{filename} @r{]}
14003 Specify that the program to be run (but not the symbol table) is found
14004 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14005 if necessary to locate your program. Omitting @var{filename} means to
14006 discard information on the executable file.
14008 @kindex symbol-file
14009 @item symbol-file @r{[} @var{filename} @r{]}
14010 Read symbol table information from file @var{filename}. @code{PATH} is
14011 searched when necessary. Use the @code{file} command to get both symbol
14012 table and program to run from the same file.
14014 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14015 program's symbol table.
14017 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14018 some breakpoints and auto-display expressions. This is because they may
14019 contain pointers to the internal data recording symbols and data types,
14020 which are part of the old symbol table data being discarded inside
14023 @code{symbol-file} does not repeat if you press @key{RET} again after
14026 When @value{GDBN} is configured for a particular environment, it
14027 understands debugging information in whatever format is the standard
14028 generated for that environment; you may use either a @sc{gnu} compiler, or
14029 other compilers that adhere to the local conventions.
14030 Best results are usually obtained from @sc{gnu} compilers; for example,
14031 using @code{@value{NGCC}} you can generate debugging information for
14034 For most kinds of object files, with the exception of old SVR3 systems
14035 using COFF, the @code{symbol-file} command does not normally read the
14036 symbol table in full right away. Instead, it scans the symbol table
14037 quickly to find which source files and which symbols are present. The
14038 details are read later, one source file at a time, as they are needed.
14040 The purpose of this two-stage reading strategy is to make @value{GDBN}
14041 start up faster. For the most part, it is invisible except for
14042 occasional pauses while the symbol table details for a particular source
14043 file are being read. (The @code{set verbose} command can turn these
14044 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14045 Warnings and Messages}.)
14047 We have not implemented the two-stage strategy for COFF yet. When the
14048 symbol table is stored in COFF format, @code{symbol-file} reads the
14049 symbol table data in full right away. Note that ``stabs-in-COFF''
14050 still does the two-stage strategy, since the debug info is actually
14054 @cindex reading symbols immediately
14055 @cindex symbols, reading immediately
14056 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14057 @itemx file @r{[} -readnow @r{]} @var{filename}
14058 You can override the @value{GDBN} two-stage strategy for reading symbol
14059 tables by using the @samp{-readnow} option with any of the commands that
14060 load symbol table information, if you want to be sure @value{GDBN} has the
14061 entire symbol table available.
14063 @c FIXME: for now no mention of directories, since this seems to be in
14064 @c flux. 13mar1992 status is that in theory GDB would look either in
14065 @c current dir or in same dir as myprog; but issues like competing
14066 @c GDB's, or clutter in system dirs, mean that in practice right now
14067 @c only current dir is used. FFish says maybe a special GDB hierarchy
14068 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14072 @item core-file @r{[}@var{filename}@r{]}
14074 Specify the whereabouts of a core dump file to be used as the ``contents
14075 of memory''. Traditionally, core files contain only some parts of the
14076 address space of the process that generated them; @value{GDBN} can access the
14077 executable file itself for other parts.
14079 @code{core-file} with no argument specifies that no core file is
14082 Note that the core file is ignored when your program is actually running
14083 under @value{GDBN}. So, if you have been running your program and you
14084 wish to debug a core file instead, you must kill the subprocess in which
14085 the program is running. To do this, use the @code{kill} command
14086 (@pxref{Kill Process, ,Killing the Child Process}).
14088 @kindex add-symbol-file
14089 @cindex dynamic linking
14090 @item add-symbol-file @var{filename} @var{address}
14091 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14092 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14093 The @code{add-symbol-file} command reads additional symbol table
14094 information from the file @var{filename}. You would use this command
14095 when @var{filename} has been dynamically loaded (by some other means)
14096 into the program that is running. @var{address} should be the memory
14097 address at which the file has been loaded; @value{GDBN} cannot figure
14098 this out for itself. You can additionally specify an arbitrary number
14099 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14100 section name and base address for that section. You can specify any
14101 @var{address} as an expression.
14103 The symbol table of the file @var{filename} is added to the symbol table
14104 originally read with the @code{symbol-file} command. You can use the
14105 @code{add-symbol-file} command any number of times; the new symbol data
14106 thus read keeps adding to the old. To discard all old symbol data
14107 instead, use the @code{symbol-file} command without any arguments.
14109 @cindex relocatable object files, reading symbols from
14110 @cindex object files, relocatable, reading symbols from
14111 @cindex reading symbols from relocatable object files
14112 @cindex symbols, reading from relocatable object files
14113 @cindex @file{.o} files, reading symbols from
14114 Although @var{filename} is typically a shared library file, an
14115 executable file, or some other object file which has been fully
14116 relocated for loading into a process, you can also load symbolic
14117 information from relocatable @file{.o} files, as long as:
14121 the file's symbolic information refers only to linker symbols defined in
14122 that file, not to symbols defined by other object files,
14124 every section the file's symbolic information refers to has actually
14125 been loaded into the inferior, as it appears in the file, and
14127 you can determine the address at which every section was loaded, and
14128 provide these to the @code{add-symbol-file} command.
14132 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14133 relocatable files into an already running program; such systems
14134 typically make the requirements above easy to meet. However, it's
14135 important to recognize that many native systems use complex link
14136 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14137 assembly, for example) that make the requirements difficult to meet. In
14138 general, one cannot assume that using @code{add-symbol-file} to read a
14139 relocatable object file's symbolic information will have the same effect
14140 as linking the relocatable object file into the program in the normal
14143 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14145 @kindex add-symbol-file-from-memory
14146 @cindex @code{syscall DSO}
14147 @cindex load symbols from memory
14148 @item add-symbol-file-from-memory @var{address}
14149 Load symbols from the given @var{address} in a dynamically loaded
14150 object file whose image is mapped directly into the inferior's memory.
14151 For example, the Linux kernel maps a @code{syscall DSO} into each
14152 process's address space; this DSO provides kernel-specific code for
14153 some system calls. The argument can be any expression whose
14154 evaluation yields the address of the file's shared object file header.
14155 For this command to work, you must have used @code{symbol-file} or
14156 @code{exec-file} commands in advance.
14158 @kindex add-shared-symbol-files
14160 @item add-shared-symbol-files @var{library-file}
14161 @itemx assf @var{library-file}
14162 The @code{add-shared-symbol-files} command can currently be used only
14163 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14164 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14165 @value{GDBN} automatically looks for shared libraries, however if
14166 @value{GDBN} does not find yours, you can invoke
14167 @code{add-shared-symbol-files}. It takes one argument: the shared
14168 library's file name. @code{assf} is a shorthand alias for
14169 @code{add-shared-symbol-files}.
14172 @item section @var{section} @var{addr}
14173 The @code{section} command changes the base address of the named
14174 @var{section} of the exec file to @var{addr}. This can be used if the
14175 exec file does not contain section addresses, (such as in the
14176 @code{a.out} format), or when the addresses specified in the file
14177 itself are wrong. Each section must be changed separately. The
14178 @code{info files} command, described below, lists all the sections and
14182 @kindex info target
14185 @code{info files} and @code{info target} are synonymous; both print the
14186 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14187 including the names of the executable and core dump files currently in
14188 use by @value{GDBN}, and the files from which symbols were loaded. The
14189 command @code{help target} lists all possible targets rather than
14192 @kindex maint info sections
14193 @item maint info sections
14194 Another command that can give you extra information about program sections
14195 is @code{maint info sections}. In addition to the section information
14196 displayed by @code{info files}, this command displays the flags and file
14197 offset of each section in the executable and core dump files. In addition,
14198 @code{maint info sections} provides the following command options (which
14199 may be arbitrarily combined):
14203 Display sections for all loaded object files, including shared libraries.
14204 @item @var{sections}
14205 Display info only for named @var{sections}.
14206 @item @var{section-flags}
14207 Display info only for sections for which @var{section-flags} are true.
14208 The section flags that @value{GDBN} currently knows about are:
14211 Section will have space allocated in the process when loaded.
14212 Set for all sections except those containing debug information.
14214 Section will be loaded from the file into the child process memory.
14215 Set for pre-initialized code and data, clear for @code{.bss} sections.
14217 Section needs to be relocated before loading.
14219 Section cannot be modified by the child process.
14221 Section contains executable code only.
14223 Section contains data only (no executable code).
14225 Section will reside in ROM.
14227 Section contains data for constructor/destructor lists.
14229 Section is not empty.
14231 An instruction to the linker to not output the section.
14232 @item COFF_SHARED_LIBRARY
14233 A notification to the linker that the section contains
14234 COFF shared library information.
14236 Section contains common symbols.
14239 @kindex set trust-readonly-sections
14240 @cindex read-only sections
14241 @item set trust-readonly-sections on
14242 Tell @value{GDBN} that readonly sections in your object file
14243 really are read-only (i.e.@: that their contents will not change).
14244 In that case, @value{GDBN} can fetch values from these sections
14245 out of the object file, rather than from the target program.
14246 For some targets (notably embedded ones), this can be a significant
14247 enhancement to debugging performance.
14249 The default is off.
14251 @item set trust-readonly-sections off
14252 Tell @value{GDBN} not to trust readonly sections. This means that
14253 the contents of the section might change while the program is running,
14254 and must therefore be fetched from the target when needed.
14256 @item show trust-readonly-sections
14257 Show the current setting of trusting readonly sections.
14260 All file-specifying commands allow both absolute and relative file names
14261 as arguments. @value{GDBN} always converts the file name to an absolute file
14262 name and remembers it that way.
14264 @cindex shared libraries
14265 @anchor{Shared Libraries}
14266 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14267 and IBM RS/6000 AIX shared libraries.
14269 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14270 shared libraries. @xref{Expat}.
14272 @value{GDBN} automatically loads symbol definitions from shared libraries
14273 when you use the @code{run} command, or when you examine a core file.
14274 (Before you issue the @code{run} command, @value{GDBN} does not understand
14275 references to a function in a shared library, however---unless you are
14276 debugging a core file).
14278 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14279 automatically loads the symbols at the time of the @code{shl_load} call.
14281 @c FIXME: some @value{GDBN} release may permit some refs to undef
14282 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14283 @c FIXME...lib; check this from time to time when updating manual
14285 There are times, however, when you may wish to not automatically load
14286 symbol definitions from shared libraries, such as when they are
14287 particularly large or there are many of them.
14289 To control the automatic loading of shared library symbols, use the
14293 @kindex set auto-solib-add
14294 @item set auto-solib-add @var{mode}
14295 If @var{mode} is @code{on}, symbols from all shared object libraries
14296 will be loaded automatically when the inferior begins execution, you
14297 attach to an independently started inferior, or when the dynamic linker
14298 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14299 is @code{off}, symbols must be loaded manually, using the
14300 @code{sharedlibrary} command. The default value is @code{on}.
14302 @cindex memory used for symbol tables
14303 If your program uses lots of shared libraries with debug info that
14304 takes large amounts of memory, you can decrease the @value{GDBN}
14305 memory footprint by preventing it from automatically loading the
14306 symbols from shared libraries. To that end, type @kbd{set
14307 auto-solib-add off} before running the inferior, then load each
14308 library whose debug symbols you do need with @kbd{sharedlibrary
14309 @var{regexp}}, where @var{regexp} is a regular expression that matches
14310 the libraries whose symbols you want to be loaded.
14312 @kindex show auto-solib-add
14313 @item show auto-solib-add
14314 Display the current autoloading mode.
14317 @cindex load shared library
14318 To explicitly load shared library symbols, use the @code{sharedlibrary}
14322 @kindex info sharedlibrary
14324 @item info share @var{regex}
14325 @itemx info sharedlibrary @var{regex}
14326 Print the names of the shared libraries which are currently loaded
14327 that match @var{regex}. If @var{regex} is omitted then print
14328 all shared libraries that are loaded.
14330 @kindex sharedlibrary
14332 @item sharedlibrary @var{regex}
14333 @itemx share @var{regex}
14334 Load shared object library symbols for files matching a
14335 Unix regular expression.
14336 As with files loaded automatically, it only loads shared libraries
14337 required by your program for a core file or after typing @code{run}. If
14338 @var{regex} is omitted all shared libraries required by your program are
14341 @item nosharedlibrary
14342 @kindex nosharedlibrary
14343 @cindex unload symbols from shared libraries
14344 Unload all shared object library symbols. This discards all symbols
14345 that have been loaded from all shared libraries. Symbols from shared
14346 libraries that were loaded by explicit user requests are not
14350 Sometimes you may wish that @value{GDBN} stops and gives you control
14351 when any of shared library events happen. Use the @code{set
14352 stop-on-solib-events} command for this:
14355 @item set stop-on-solib-events
14356 @kindex set stop-on-solib-events
14357 This command controls whether @value{GDBN} should give you control
14358 when the dynamic linker notifies it about some shared library event.
14359 The most common event of interest is loading or unloading of a new
14362 @item show stop-on-solib-events
14363 @kindex show stop-on-solib-events
14364 Show whether @value{GDBN} stops and gives you control when shared
14365 library events happen.
14368 Shared libraries are also supported in many cross or remote debugging
14369 configurations. @value{GDBN} needs to have access to the target's libraries;
14370 this can be accomplished either by providing copies of the libraries
14371 on the host system, or by asking @value{GDBN} to automatically retrieve the
14372 libraries from the target. If copies of the target libraries are
14373 provided, they need to be the same as the target libraries, although the
14374 copies on the target can be stripped as long as the copies on the host are
14377 @cindex where to look for shared libraries
14378 For remote debugging, you need to tell @value{GDBN} where the target
14379 libraries are, so that it can load the correct copies---otherwise, it
14380 may try to load the host's libraries. @value{GDBN} has two variables
14381 to specify the search directories for target libraries.
14384 @cindex prefix for shared library file names
14385 @cindex system root, alternate
14386 @kindex set solib-absolute-prefix
14387 @kindex set sysroot
14388 @item set sysroot @var{path}
14389 Use @var{path} as the system root for the program being debugged. Any
14390 absolute shared library paths will be prefixed with @var{path}; many
14391 runtime loaders store the absolute paths to the shared library in the
14392 target program's memory. If you use @code{set sysroot} to find shared
14393 libraries, they need to be laid out in the same way that they are on
14394 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
14397 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
14398 retrieve the target libraries from the remote system. This is only
14399 supported when using a remote target that supports the @code{remote get}
14400 command (@pxref{File Transfer,,Sending files to a remote system}).
14401 The part of @var{path} following the initial @file{remote:}
14402 (if present) is used as system root prefix on the remote file system.
14403 @footnote{If you want to specify a local system root using a directory
14404 that happens to be named @file{remote:}, you need to use some equivalent
14405 variant of the name like @file{./remote:}.}
14407 For targets with an MS-DOS based filesystem, such as MS-Windows and
14408 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
14409 absolute file name with @var{path}. But first, on Unix hosts,
14410 @value{GDBN} converts all backslash directory separators into forward
14411 slashes, because the backslash is not a directory separator on Unix:
14414 c:\foo\bar.dll @result{} c:/foo/bar.dll
14417 Then, @value{GDBN} attempts prefixing the target file name with
14418 @var{path}, and looks for the resulting file name in the host file
14422 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
14425 If that does not find the shared library, @value{GDBN} tries removing
14426 the @samp{:} character from the drive spec, both for convenience, and,
14427 for the case of the host file system not supporting file names with
14431 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
14434 This makes it possible to have a system root that mirrors a target
14435 with more than one drive. E.g., you may want to setup your local
14436 copies of the target system shared libraries like so (note @samp{c} vs
14440 @file{/path/to/sysroot/c/sys/bin/foo.dll}
14441 @file{/path/to/sysroot/c/sys/bin/bar.dll}
14442 @file{/path/to/sysroot/z/sys/bin/bar.dll}
14446 and point the system root at @file{/path/to/sysroot}, so that
14447 @value{GDBN} can find the correct copies of both
14448 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
14450 If that still does not find the shared library, @value{GDBN} tries
14451 removing the whole drive spec from the target file name:
14454 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
14457 This last lookup makes it possible to not care about the drive name,
14458 if you don't want or need to.
14460 The @code{set solib-absolute-prefix} command is an alias for @code{set
14463 @cindex default system root
14464 @cindex @samp{--with-sysroot}
14465 You can set the default system root by using the configure-time
14466 @samp{--with-sysroot} option. If the system root is inside
14467 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14468 @samp{--exec-prefix}), then the default system root will be updated
14469 automatically if the installed @value{GDBN} is moved to a new
14472 @kindex show sysroot
14474 Display the current shared library prefix.
14476 @kindex set solib-search-path
14477 @item set solib-search-path @var{path}
14478 If this variable is set, @var{path} is a colon-separated list of
14479 directories to search for shared libraries. @samp{solib-search-path}
14480 is used after @samp{sysroot} fails to locate the library, or if the
14481 path to the library is relative instead of absolute. If you want to
14482 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
14483 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
14484 finding your host's libraries. @samp{sysroot} is preferred; setting
14485 it to a nonexistent directory may interfere with automatic loading
14486 of shared library symbols.
14488 @kindex show solib-search-path
14489 @item show solib-search-path
14490 Display the current shared library search path.
14492 @cindex DOS file-name semantics of file names.
14493 @kindex set target-file-system-kind (unix|dos-based|auto)
14494 @kindex show target-file-system-kind
14495 @item set target-file-system-kind @var{kind}
14496 Set assumed file system kind for target reported file names.
14498 Shared library file names as reported by the target system may not
14499 make sense as is on the system @value{GDBN} is running on. For
14500 example, when remote debugging a target that has MS-DOS based file
14501 system semantics, from a Unix host, the target may be reporting to
14502 @value{GDBN} a list of loaded shared libraries with file names such as
14503 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
14504 drive letters, so the @samp{c:\} prefix is not normally understood as
14505 indicating an absolute file name, and neither is the backslash
14506 normally considered a directory separator character. In that case,
14507 the native file system would interpret this whole absolute file name
14508 as a relative file name with no directory components. This would make
14509 it impossible to point @value{GDBN} at a copy of the remote target's
14510 shared libraries on the host using @code{set sysroot}, and impractical
14511 with @code{set solib-search-path}. Setting
14512 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
14513 to interpret such file names similarly to how the target would, and to
14514 map them to file names valid on @value{GDBN}'s native file system
14515 semantics. The value of @var{kind} can be @code{"auto"}, in addition
14516 to one of the supported file system kinds. In that case, @value{GDBN}
14517 tries to determine the appropriate file system variant based on the
14518 current target's operating system (@pxref{ABI, ,Configuring the
14519 Current ABI}). The supported file system settings are:
14523 Instruct @value{GDBN} to assume the target file system is of Unix
14524 kind. Only file names starting the forward slash (@samp{/}) character
14525 are considered absolute, and the directory separator character is also
14529 Instruct @value{GDBN} to assume the target file system is DOS based.
14530 File names starting with either a forward slash, or a drive letter
14531 followed by a colon (e.g., @samp{c:}), are considered absolute, and
14532 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
14533 considered directory separators.
14536 Instruct @value{GDBN} to use the file system kind associated with the
14537 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
14538 This is the default.
14543 @node Separate Debug Files
14544 @section Debugging Information in Separate Files
14545 @cindex separate debugging information files
14546 @cindex debugging information in separate files
14547 @cindex @file{.debug} subdirectories
14548 @cindex debugging information directory, global
14549 @cindex global debugging information directory
14550 @cindex build ID, and separate debugging files
14551 @cindex @file{.build-id} directory
14553 @value{GDBN} allows you to put a program's debugging information in a
14554 file separate from the executable itself, in a way that allows
14555 @value{GDBN} to find and load the debugging information automatically.
14556 Since debugging information can be very large---sometimes larger
14557 than the executable code itself---some systems distribute debugging
14558 information for their executables in separate files, which users can
14559 install only when they need to debug a problem.
14561 @value{GDBN} supports two ways of specifying the separate debug info
14566 The executable contains a @dfn{debug link} that specifies the name of
14567 the separate debug info file. The separate debug file's name is
14568 usually @file{@var{executable}.debug}, where @var{executable} is the
14569 name of the corresponding executable file without leading directories
14570 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14571 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14572 checksum for the debug file, which @value{GDBN} uses to validate that
14573 the executable and the debug file came from the same build.
14576 The executable contains a @dfn{build ID}, a unique bit string that is
14577 also present in the corresponding debug info file. (This is supported
14578 only on some operating systems, notably those which use the ELF format
14579 for binary files and the @sc{gnu} Binutils.) For more details about
14580 this feature, see the description of the @option{--build-id}
14581 command-line option in @ref{Options, , Command Line Options, ld.info,
14582 The GNU Linker}. The debug info file's name is not specified
14583 explicitly by the build ID, but can be computed from the build ID, see
14587 Depending on the way the debug info file is specified, @value{GDBN}
14588 uses two different methods of looking for the debug file:
14592 For the ``debug link'' method, @value{GDBN} looks up the named file in
14593 the directory of the executable file, then in a subdirectory of that
14594 directory named @file{.debug}, and finally under the global debug
14595 directory, in a subdirectory whose name is identical to the leading
14596 directories of the executable's absolute file name.
14599 For the ``build ID'' method, @value{GDBN} looks in the
14600 @file{.build-id} subdirectory of the global debug directory for a file
14601 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
14602 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
14603 are the rest of the bit string. (Real build ID strings are 32 or more
14604 hex characters, not 10.)
14607 So, for example, suppose you ask @value{GDBN} to debug
14608 @file{/usr/bin/ls}, which has a debug link that specifies the
14609 file @file{ls.debug}, and a build ID whose value in hex is
14610 @code{abcdef1234}. If the global debug directory is
14611 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
14612 debug information files, in the indicated order:
14616 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
14618 @file{/usr/bin/ls.debug}
14620 @file{/usr/bin/.debug/ls.debug}
14622 @file{/usr/lib/debug/usr/bin/ls.debug}.
14625 You can set the global debugging info directory's name, and view the
14626 name @value{GDBN} is currently using.
14630 @kindex set debug-file-directory
14631 @item set debug-file-directory @var{directories}
14632 Set the directories which @value{GDBN} searches for separate debugging
14633 information files to @var{directory}. Multiple directory components can be set
14634 concatenating them by a directory separator.
14636 @kindex show debug-file-directory
14637 @item show debug-file-directory
14638 Show the directories @value{GDBN} searches for separate debugging
14643 @cindex @code{.gnu_debuglink} sections
14644 @cindex debug link sections
14645 A debug link is a special section of the executable file named
14646 @code{.gnu_debuglink}. The section must contain:
14650 A filename, with any leading directory components removed, followed by
14653 zero to three bytes of padding, as needed to reach the next four-byte
14654 boundary within the section, and
14656 a four-byte CRC checksum, stored in the same endianness used for the
14657 executable file itself. The checksum is computed on the debugging
14658 information file's full contents by the function given below, passing
14659 zero as the @var{crc} argument.
14662 Any executable file format can carry a debug link, as long as it can
14663 contain a section named @code{.gnu_debuglink} with the contents
14666 @cindex @code{.note.gnu.build-id} sections
14667 @cindex build ID sections
14668 The build ID is a special section in the executable file (and in other
14669 ELF binary files that @value{GDBN} may consider). This section is
14670 often named @code{.note.gnu.build-id}, but that name is not mandatory.
14671 It contains unique identification for the built files---the ID remains
14672 the same across multiple builds of the same build tree. The default
14673 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
14674 content for the build ID string. The same section with an identical
14675 value is present in the original built binary with symbols, in its
14676 stripped variant, and in the separate debugging information file.
14678 The debugging information file itself should be an ordinary
14679 executable, containing a full set of linker symbols, sections, and
14680 debugging information. The sections of the debugging information file
14681 should have the same names, addresses, and sizes as the original file,
14682 but they need not contain any data---much like a @code{.bss} section
14683 in an ordinary executable.
14685 The @sc{gnu} binary utilities (Binutils) package includes the
14686 @samp{objcopy} utility that can produce
14687 the separated executable / debugging information file pairs using the
14688 following commands:
14691 @kbd{objcopy --only-keep-debug foo foo.debug}
14696 These commands remove the debugging
14697 information from the executable file @file{foo} and place it in the file
14698 @file{foo.debug}. You can use the first, second or both methods to link the
14703 The debug link method needs the following additional command to also leave
14704 behind a debug link in @file{foo}:
14707 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
14710 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
14711 a version of the @code{strip} command such that the command @kbd{strip foo -f
14712 foo.debug} has the same functionality as the two @code{objcopy} commands and
14713 the @code{ln -s} command above, together.
14716 Build ID gets embedded into the main executable using @code{ld --build-id} or
14717 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
14718 compatibility fixes for debug files separation are present in @sc{gnu} binary
14719 utilities (Binutils) package since version 2.18.
14724 @cindex CRC algorithm definition
14725 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
14726 IEEE 802.3 using the polynomial:
14728 @c TexInfo requires naked braces for multi-digit exponents for Tex
14729 @c output, but this causes HTML output to barf. HTML has to be set using
14730 @c raw commands. So we end up having to specify this equation in 2
14735 <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>
14736 + <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
14742 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
14743 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
14747 The function is computed byte at a time, taking the least
14748 significant bit of each byte first. The initial pattern
14749 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
14750 the final result is inverted to ensure trailing zeros also affect the
14753 @emph{Note:} This is the same CRC polynomial as used in handling the
14754 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
14755 , @value{GDBN} Remote Serial Protocol}). However in the
14756 case of the Remote Serial Protocol, the CRC is computed @emph{most}
14757 significant bit first, and the result is not inverted, so trailing
14758 zeros have no effect on the CRC value.
14760 To complete the description, we show below the code of the function
14761 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
14762 initially supplied @code{crc} argument means that an initial call to
14763 this function passing in zero will start computing the CRC using
14766 @kindex gnu_debuglink_crc32
14769 gnu_debuglink_crc32 (unsigned long crc,
14770 unsigned char *buf, size_t len)
14772 static const unsigned long crc32_table[256] =
14774 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
14775 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
14776 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
14777 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
14778 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
14779 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
14780 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
14781 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
14782 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
14783 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
14784 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
14785 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
14786 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
14787 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
14788 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
14789 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
14790 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
14791 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
14792 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
14793 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
14794 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
14795 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
14796 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
14797 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
14798 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
14799 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
14800 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
14801 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
14802 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
14803 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
14804 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
14805 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
14806 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
14807 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
14808 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
14809 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
14810 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
14811 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
14812 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
14813 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
14814 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
14815 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
14816 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
14817 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
14818 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
14819 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
14820 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
14821 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
14822 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
14823 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
14824 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
14827 unsigned char *end;
14829 crc = ~crc & 0xffffffff;
14830 for (end = buf + len; buf < end; ++buf)
14831 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
14832 return ~crc & 0xffffffff;
14837 This computation does not apply to the ``build ID'' method.
14840 @node Symbol Errors
14841 @section Errors Reading Symbol Files
14843 While reading a symbol file, @value{GDBN} occasionally encounters problems,
14844 such as symbol types it does not recognize, or known bugs in compiler
14845 output. By default, @value{GDBN} does not notify you of such problems, since
14846 they are relatively common and primarily of interest to people
14847 debugging compilers. If you are interested in seeing information
14848 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
14849 only one message about each such type of problem, no matter how many
14850 times the problem occurs; or you can ask @value{GDBN} to print more messages,
14851 to see how many times the problems occur, with the @code{set
14852 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
14855 The messages currently printed, and their meanings, include:
14858 @item inner block not inside outer block in @var{symbol}
14860 The symbol information shows where symbol scopes begin and end
14861 (such as at the start of a function or a block of statements). This
14862 error indicates that an inner scope block is not fully contained
14863 in its outer scope blocks.
14865 @value{GDBN} circumvents the problem by treating the inner block as if it had
14866 the same scope as the outer block. In the error message, @var{symbol}
14867 may be shown as ``@code{(don't know)}'' if the outer block is not a
14870 @item block at @var{address} out of order
14872 The symbol information for symbol scope blocks should occur in
14873 order of increasing addresses. This error indicates that it does not
14876 @value{GDBN} does not circumvent this problem, and has trouble
14877 locating symbols in the source file whose symbols it is reading. (You
14878 can often determine what source file is affected by specifying
14879 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
14882 @item bad block start address patched
14884 The symbol information for a symbol scope block has a start address
14885 smaller than the address of the preceding source line. This is known
14886 to occur in the SunOS 4.1.1 (and earlier) C compiler.
14888 @value{GDBN} circumvents the problem by treating the symbol scope block as
14889 starting on the previous source line.
14891 @item bad string table offset in symbol @var{n}
14894 Symbol number @var{n} contains a pointer into the string table which is
14895 larger than the size of the string table.
14897 @value{GDBN} circumvents the problem by considering the symbol to have the
14898 name @code{foo}, which may cause other problems if many symbols end up
14901 @item unknown symbol type @code{0x@var{nn}}
14903 The symbol information contains new data types that @value{GDBN} does
14904 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
14905 uncomprehended information, in hexadecimal.
14907 @value{GDBN} circumvents the error by ignoring this symbol information.
14908 This usually allows you to debug your program, though certain symbols
14909 are not accessible. If you encounter such a problem and feel like
14910 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
14911 on @code{complain}, then go up to the function @code{read_dbx_symtab}
14912 and examine @code{*bufp} to see the symbol.
14914 @item stub type has NULL name
14916 @value{GDBN} could not find the full definition for a struct or class.
14918 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
14919 The symbol information for a C@t{++} member function is missing some
14920 information that recent versions of the compiler should have output for
14923 @item info mismatch between compiler and debugger
14925 @value{GDBN} could not parse a type specification output by the compiler.
14930 @section GDB Data Files
14932 @cindex prefix for data files
14933 @value{GDBN} will sometimes read an auxiliary data file. These files
14934 are kept in a directory known as the @dfn{data directory}.
14936 You can set the data directory's name, and view the name @value{GDBN}
14937 is currently using.
14940 @kindex set data-directory
14941 @item set data-directory @var{directory}
14942 Set the directory which @value{GDBN} searches for auxiliary data files
14943 to @var{directory}.
14945 @kindex show data-directory
14946 @item show data-directory
14947 Show the directory @value{GDBN} searches for auxiliary data files.
14950 @cindex default data directory
14951 @cindex @samp{--with-gdb-datadir}
14952 You can set the default data directory by using the configure-time
14953 @samp{--with-gdb-datadir} option. If the data directory is inside
14954 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14955 @samp{--exec-prefix}), then the default data directory will be updated
14956 automatically if the installed @value{GDBN} is moved to a new
14960 @chapter Specifying a Debugging Target
14962 @cindex debugging target
14963 A @dfn{target} is the execution environment occupied by your program.
14965 Often, @value{GDBN} runs in the same host environment as your program;
14966 in that case, the debugging target is specified as a side effect when
14967 you use the @code{file} or @code{core} commands. When you need more
14968 flexibility---for example, running @value{GDBN} on a physically separate
14969 host, or controlling a standalone system over a serial port or a
14970 realtime system over a TCP/IP connection---you can use the @code{target}
14971 command to specify one of the target types configured for @value{GDBN}
14972 (@pxref{Target Commands, ,Commands for Managing Targets}).
14974 @cindex target architecture
14975 It is possible to build @value{GDBN} for several different @dfn{target
14976 architectures}. When @value{GDBN} is built like that, you can choose
14977 one of the available architectures with the @kbd{set architecture}
14981 @kindex set architecture
14982 @kindex show architecture
14983 @item set architecture @var{arch}
14984 This command sets the current target architecture to @var{arch}. The
14985 value of @var{arch} can be @code{"auto"}, in addition to one of the
14986 supported architectures.
14988 @item show architecture
14989 Show the current target architecture.
14991 @item set processor
14993 @kindex set processor
14994 @kindex show processor
14995 These are alias commands for, respectively, @code{set architecture}
14996 and @code{show architecture}.
15000 * Active Targets:: Active targets
15001 * Target Commands:: Commands for managing targets
15002 * Byte Order:: Choosing target byte order
15005 @node Active Targets
15006 @section Active Targets
15008 @cindex stacking targets
15009 @cindex active targets
15010 @cindex multiple targets
15012 There are three classes of targets: processes, core files, and
15013 executable files. @value{GDBN} can work concurrently on up to three
15014 active targets, one in each class. This allows you to (for example)
15015 start a process and inspect its activity without abandoning your work on
15018 For example, if you execute @samp{gdb a.out}, then the executable file
15019 @code{a.out} is the only active target. If you designate a core file as
15020 well---presumably from a prior run that crashed and coredumped---then
15021 @value{GDBN} has two active targets and uses them in tandem, looking
15022 first in the corefile target, then in the executable file, to satisfy
15023 requests for memory addresses. (Typically, these two classes of target
15024 are complementary, since core files contain only a program's
15025 read-write memory---variables and so on---plus machine status, while
15026 executable files contain only the program text and initialized data.)
15028 When you type @code{run}, your executable file becomes an active process
15029 target as well. When a process target is active, all @value{GDBN}
15030 commands requesting memory addresses refer to that target; addresses in
15031 an active core file or executable file target are obscured while the
15032 process target is active.
15034 Use the @code{core-file} and @code{exec-file} commands to select a new
15035 core file or executable target (@pxref{Files, ,Commands to Specify
15036 Files}). To specify as a target a process that is already running, use
15037 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
15040 @node Target Commands
15041 @section Commands for Managing Targets
15044 @item target @var{type} @var{parameters}
15045 Connects the @value{GDBN} host environment to a target machine or
15046 process. A target is typically a protocol for talking to debugging
15047 facilities. You use the argument @var{type} to specify the type or
15048 protocol of the target machine.
15050 Further @var{parameters} are interpreted by the target protocol, but
15051 typically include things like device names or host names to connect
15052 with, process numbers, and baud rates.
15054 The @code{target} command does not repeat if you press @key{RET} again
15055 after executing the command.
15057 @kindex help target
15059 Displays the names of all targets available. To display targets
15060 currently selected, use either @code{info target} or @code{info files}
15061 (@pxref{Files, ,Commands to Specify Files}).
15063 @item help target @var{name}
15064 Describe a particular target, including any parameters necessary to
15067 @kindex set gnutarget
15068 @item set gnutarget @var{args}
15069 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15070 knows whether it is reading an @dfn{executable},
15071 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15072 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15073 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15076 @emph{Warning:} To specify a file format with @code{set gnutarget},
15077 you must know the actual BFD name.
15081 @xref{Files, , Commands to Specify Files}.
15083 @kindex show gnutarget
15084 @item show gnutarget
15085 Use the @code{show gnutarget} command to display what file format
15086 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15087 @value{GDBN} will determine the file format for each file automatically,
15088 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15091 @cindex common targets
15092 Here are some common targets (available, or not, depending on the GDB
15097 @item target exec @var{program}
15098 @cindex executable file target
15099 An executable file. @samp{target exec @var{program}} is the same as
15100 @samp{exec-file @var{program}}.
15102 @item target core @var{filename}
15103 @cindex core dump file target
15104 A core dump file. @samp{target core @var{filename}} is the same as
15105 @samp{core-file @var{filename}}.
15107 @item target remote @var{medium}
15108 @cindex remote target
15109 A remote system connected to @value{GDBN} via a serial line or network
15110 connection. This command tells @value{GDBN} to use its own remote
15111 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15113 For example, if you have a board connected to @file{/dev/ttya} on the
15114 machine running @value{GDBN}, you could say:
15117 target remote /dev/ttya
15120 @code{target remote} supports the @code{load} command. This is only
15121 useful if you have some other way of getting the stub to the target
15122 system, and you can put it somewhere in memory where it won't get
15123 clobbered by the download.
15125 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15126 @cindex built-in simulator target
15127 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15135 works; however, you cannot assume that a specific memory map, device
15136 drivers, or even basic I/O is available, although some simulators do
15137 provide these. For info about any processor-specific simulator details,
15138 see the appropriate section in @ref{Embedded Processors, ,Embedded
15143 Some configurations may include these targets as well:
15147 @item target nrom @var{dev}
15148 @cindex NetROM ROM emulator target
15149 NetROM ROM emulator. This target only supports downloading.
15153 Different targets are available on different configurations of @value{GDBN};
15154 your configuration may have more or fewer targets.
15156 Many remote targets require you to download the executable's code once
15157 you've successfully established a connection. You may wish to control
15158 various aspects of this process.
15163 @kindex set hash@r{, for remote monitors}
15164 @cindex hash mark while downloading
15165 This command controls whether a hash mark @samp{#} is displayed while
15166 downloading a file to the remote monitor. If on, a hash mark is
15167 displayed after each S-record is successfully downloaded to the
15171 @kindex show hash@r{, for remote monitors}
15172 Show the current status of displaying the hash mark.
15174 @item set debug monitor
15175 @kindex set debug monitor
15176 @cindex display remote monitor communications
15177 Enable or disable display of communications messages between
15178 @value{GDBN} and the remote monitor.
15180 @item show debug monitor
15181 @kindex show debug monitor
15182 Show the current status of displaying communications between
15183 @value{GDBN} and the remote monitor.
15188 @kindex load @var{filename}
15189 @item load @var{filename}
15191 Depending on what remote debugging facilities are configured into
15192 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15193 is meant to make @var{filename} (an executable) available for debugging
15194 on the remote system---by downloading, or dynamic linking, for example.
15195 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15196 the @code{add-symbol-file} command.
15198 If your @value{GDBN} does not have a @code{load} command, attempting to
15199 execute it gets the error message ``@code{You can't do that when your
15200 target is @dots{}}''
15202 The file is loaded at whatever address is specified in the executable.
15203 For some object file formats, you can specify the load address when you
15204 link the program; for other formats, like a.out, the object file format
15205 specifies a fixed address.
15206 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15208 Depending on the remote side capabilities, @value{GDBN} may be able to
15209 load programs into flash memory.
15211 @code{load} does not repeat if you press @key{RET} again after using it.
15215 @section Choosing Target Byte Order
15217 @cindex choosing target byte order
15218 @cindex target byte order
15220 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15221 offer the ability to run either big-endian or little-endian byte
15222 orders. Usually the executable or symbol will include a bit to
15223 designate the endian-ness, and you will not need to worry about
15224 which to use. However, you may still find it useful to adjust
15225 @value{GDBN}'s idea of processor endian-ness manually.
15229 @item set endian big
15230 Instruct @value{GDBN} to assume the target is big-endian.
15232 @item set endian little
15233 Instruct @value{GDBN} to assume the target is little-endian.
15235 @item set endian auto
15236 Instruct @value{GDBN} to use the byte order associated with the
15240 Display @value{GDBN}'s current idea of the target byte order.
15244 Note that these commands merely adjust interpretation of symbolic
15245 data on the host, and that they have absolutely no effect on the
15249 @node Remote Debugging
15250 @chapter Debugging Remote Programs
15251 @cindex remote debugging
15253 If you are trying to debug a program running on a machine that cannot run
15254 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15255 For example, you might use remote debugging on an operating system kernel,
15256 or on a small system which does not have a general purpose operating system
15257 powerful enough to run a full-featured debugger.
15259 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15260 to make this work with particular debugging targets. In addition,
15261 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15262 but not specific to any particular target system) which you can use if you
15263 write the remote stubs---the code that runs on the remote system to
15264 communicate with @value{GDBN}.
15266 Other remote targets may be available in your
15267 configuration of @value{GDBN}; use @code{help target} to list them.
15270 * Connecting:: Connecting to a remote target
15271 * File Transfer:: Sending files to a remote system
15272 * Server:: Using the gdbserver program
15273 * Remote Configuration:: Remote configuration
15274 * Remote Stub:: Implementing a remote stub
15278 @section Connecting to a Remote Target
15280 On the @value{GDBN} host machine, you will need an unstripped copy of
15281 your program, since @value{GDBN} needs symbol and debugging information.
15282 Start up @value{GDBN} as usual, using the name of the local copy of your
15283 program as the first argument.
15285 @cindex @code{target remote}
15286 @value{GDBN} can communicate with the target over a serial line, or
15287 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15288 each case, @value{GDBN} uses the same protocol for debugging your
15289 program; only the medium carrying the debugging packets varies. The
15290 @code{target remote} command establishes a connection to the target.
15291 Its arguments indicate which medium to use:
15295 @item target remote @var{serial-device}
15296 @cindex serial line, @code{target remote}
15297 Use @var{serial-device} to communicate with the target. For example,
15298 to use a serial line connected to the device named @file{/dev/ttyb}:
15301 target remote /dev/ttyb
15304 If you're using a serial line, you may want to give @value{GDBN} the
15305 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15306 (@pxref{Remote Configuration, set remotebaud}) before the
15307 @code{target} command.
15309 @item target remote @code{@var{host}:@var{port}}
15310 @itemx target remote @code{tcp:@var{host}:@var{port}}
15311 @cindex @acronym{TCP} port, @code{target remote}
15312 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15313 The @var{host} may be either a host name or a numeric @acronym{IP}
15314 address; @var{port} must be a decimal number. The @var{host} could be
15315 the target machine itself, if it is directly connected to the net, or
15316 it might be a terminal server which in turn has a serial line to the
15319 For example, to connect to port 2828 on a terminal server named
15323 target remote manyfarms:2828
15326 If your remote target is actually running on the same machine as your
15327 debugger session (e.g.@: a simulator for your target running on the
15328 same host), you can omit the hostname. For example, to connect to
15329 port 1234 on your local machine:
15332 target remote :1234
15336 Note that the colon is still required here.
15338 @item target remote @code{udp:@var{host}:@var{port}}
15339 @cindex @acronym{UDP} port, @code{target remote}
15340 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15341 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15344 target remote udp:manyfarms:2828
15347 When using a @acronym{UDP} connection for remote debugging, you should
15348 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15349 can silently drop packets on busy or unreliable networks, which will
15350 cause havoc with your debugging session.
15352 @item target remote | @var{command}
15353 @cindex pipe, @code{target remote} to
15354 Run @var{command} in the background and communicate with it using a
15355 pipe. The @var{command} is a shell command, to be parsed and expanded
15356 by the system's command shell, @code{/bin/sh}; it should expect remote
15357 protocol packets on its standard input, and send replies on its
15358 standard output. You could use this to run a stand-alone simulator
15359 that speaks the remote debugging protocol, to make net connections
15360 using programs like @code{ssh}, or for other similar tricks.
15362 If @var{command} closes its standard output (perhaps by exiting),
15363 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15364 program has already exited, this will have no effect.)
15368 Once the connection has been established, you can use all the usual
15369 commands to examine and change data. The remote program is already
15370 running; you can use @kbd{step} and @kbd{continue}, and you do not
15371 need to use @kbd{run}.
15373 @cindex interrupting remote programs
15374 @cindex remote programs, interrupting
15375 Whenever @value{GDBN} is waiting for the remote program, if you type the
15376 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
15377 program. This may or may not succeed, depending in part on the hardware
15378 and the serial drivers the remote system uses. If you type the
15379 interrupt character once again, @value{GDBN} displays this prompt:
15382 Interrupted while waiting for the program.
15383 Give up (and stop debugging it)? (y or n)
15386 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
15387 (If you decide you want to try again later, you can use @samp{target
15388 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
15389 goes back to waiting.
15392 @kindex detach (remote)
15394 When you have finished debugging the remote program, you can use the
15395 @code{detach} command to release it from @value{GDBN} control.
15396 Detaching from the target normally resumes its execution, but the results
15397 will depend on your particular remote stub. After the @code{detach}
15398 command, @value{GDBN} is free to connect to another target.
15402 The @code{disconnect} command behaves like @code{detach}, except that
15403 the target is generally not resumed. It will wait for @value{GDBN}
15404 (this instance or another one) to connect and continue debugging. After
15405 the @code{disconnect} command, @value{GDBN} is again free to connect to
15408 @cindex send command to remote monitor
15409 @cindex extend @value{GDBN} for remote targets
15410 @cindex add new commands for external monitor
15412 @item monitor @var{cmd}
15413 This command allows you to send arbitrary commands directly to the
15414 remote monitor. Since @value{GDBN} doesn't care about the commands it
15415 sends like this, this command is the way to extend @value{GDBN}---you
15416 can add new commands that only the external monitor will understand
15420 @node File Transfer
15421 @section Sending files to a remote system
15422 @cindex remote target, file transfer
15423 @cindex file transfer
15424 @cindex sending files to remote systems
15426 Some remote targets offer the ability to transfer files over the same
15427 connection used to communicate with @value{GDBN}. This is convenient
15428 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
15429 running @code{gdbserver} over a network interface. For other targets,
15430 e.g.@: embedded devices with only a single serial port, this may be
15431 the only way to upload or download files.
15433 Not all remote targets support these commands.
15437 @item remote put @var{hostfile} @var{targetfile}
15438 Copy file @var{hostfile} from the host system (the machine running
15439 @value{GDBN}) to @var{targetfile} on the target system.
15442 @item remote get @var{targetfile} @var{hostfile}
15443 Copy file @var{targetfile} from the target system to @var{hostfile}
15444 on the host system.
15446 @kindex remote delete
15447 @item remote delete @var{targetfile}
15448 Delete @var{targetfile} from the target system.
15453 @section Using the @code{gdbserver} Program
15456 @cindex remote connection without stubs
15457 @code{gdbserver} is a control program for Unix-like systems, which
15458 allows you to connect your program with a remote @value{GDBN} via
15459 @code{target remote}---but without linking in the usual debugging stub.
15461 @code{gdbserver} is not a complete replacement for the debugging stubs,
15462 because it requires essentially the same operating-system facilities
15463 that @value{GDBN} itself does. In fact, a system that can run
15464 @code{gdbserver} to connect to a remote @value{GDBN} could also run
15465 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
15466 because it is a much smaller program than @value{GDBN} itself. It is
15467 also easier to port than all of @value{GDBN}, so you may be able to get
15468 started more quickly on a new system by using @code{gdbserver}.
15469 Finally, if you develop code for real-time systems, you may find that
15470 the tradeoffs involved in real-time operation make it more convenient to
15471 do as much development work as possible on another system, for example
15472 by cross-compiling. You can use @code{gdbserver} to make a similar
15473 choice for debugging.
15475 @value{GDBN} and @code{gdbserver} communicate via either a serial line
15476 or a TCP connection, using the standard @value{GDBN} remote serial
15480 @emph{Warning:} @code{gdbserver} does not have any built-in security.
15481 Do not run @code{gdbserver} connected to any public network; a
15482 @value{GDBN} connection to @code{gdbserver} provides access to the
15483 target system with the same privileges as the user running
15487 @subsection Running @code{gdbserver}
15488 @cindex arguments, to @code{gdbserver}
15490 Run @code{gdbserver} on the target system. You need a copy of the
15491 program you want to debug, including any libraries it requires.
15492 @code{gdbserver} does not need your program's symbol table, so you can
15493 strip the program if necessary to save space. @value{GDBN} on the host
15494 system does all the symbol handling.
15496 To use the server, you must tell it how to communicate with @value{GDBN};
15497 the name of your program; and the arguments for your program. The usual
15501 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
15504 @var{comm} is either a device name (to use a serial line) or a TCP
15505 hostname and portnumber. For example, to debug Emacs with the argument
15506 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
15510 target> gdbserver /dev/com1 emacs foo.txt
15513 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
15516 To use a TCP connection instead of a serial line:
15519 target> gdbserver host:2345 emacs foo.txt
15522 The only difference from the previous example is the first argument,
15523 specifying that you are communicating with the host @value{GDBN} via
15524 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
15525 expect a TCP connection from machine @samp{host} to local TCP port 2345.
15526 (Currently, the @samp{host} part is ignored.) You can choose any number
15527 you want for the port number as long as it does not conflict with any
15528 TCP ports already in use on the target system (for example, @code{23} is
15529 reserved for @code{telnet}).@footnote{If you choose a port number that
15530 conflicts with another service, @code{gdbserver} prints an error message
15531 and exits.} You must use the same port number with the host @value{GDBN}
15532 @code{target remote} command.
15534 @subsubsection Attaching to a Running Program
15536 On some targets, @code{gdbserver} can also attach to running programs.
15537 This is accomplished via the @code{--attach} argument. The syntax is:
15540 target> gdbserver --attach @var{comm} @var{pid}
15543 @var{pid} is the process ID of a currently running process. It isn't necessary
15544 to point @code{gdbserver} at a binary for the running process.
15547 @cindex attach to a program by name
15548 You can debug processes by name instead of process ID if your target has the
15549 @code{pidof} utility:
15552 target> gdbserver --attach @var{comm} `pidof @var{program}`
15555 In case more than one copy of @var{program} is running, or @var{program}
15556 has multiple threads, most versions of @code{pidof} support the
15557 @code{-s} option to only return the first process ID.
15559 @subsubsection Multi-Process Mode for @code{gdbserver}
15560 @cindex gdbserver, multiple processes
15561 @cindex multiple processes with gdbserver
15563 When you connect to @code{gdbserver} using @code{target remote},
15564 @code{gdbserver} debugs the specified program only once. When the
15565 program exits, or you detach from it, @value{GDBN} closes the connection
15566 and @code{gdbserver} exits.
15568 If you connect using @kbd{target extended-remote}, @code{gdbserver}
15569 enters multi-process mode. When the debugged program exits, or you
15570 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
15571 though no program is running. The @code{run} and @code{attach}
15572 commands instruct @code{gdbserver} to run or attach to a new program.
15573 The @code{run} command uses @code{set remote exec-file} (@pxref{set
15574 remote exec-file}) to select the program to run. Command line
15575 arguments are supported, except for wildcard expansion and I/O
15576 redirection (@pxref{Arguments}).
15578 To start @code{gdbserver} without supplying an initial command to run
15579 or process ID to attach, use the @option{--multi} command line option.
15580 Then you can connect using @kbd{target extended-remote} and start
15581 the program you want to debug.
15583 @code{gdbserver} does not automatically exit in multi-process mode.
15584 You can terminate it by using @code{monitor exit}
15585 (@pxref{Monitor Commands for gdbserver}).
15587 @subsubsection Other Command-Line Arguments for @code{gdbserver}
15589 The @option{--debug} option tells @code{gdbserver} to display extra
15590 status information about the debugging process. The
15591 @option{--remote-debug} option tells @code{gdbserver} to display
15592 remote protocol debug output. These options are intended for
15593 @code{gdbserver} development and for bug reports to the developers.
15595 The @option{--wrapper} option specifies a wrapper to launch programs
15596 for debugging. The option should be followed by the name of the
15597 wrapper, then any command-line arguments to pass to the wrapper, then
15598 @kbd{--} indicating the end of the wrapper arguments.
15600 @code{gdbserver} runs the specified wrapper program with a combined
15601 command line including the wrapper arguments, then the name of the
15602 program to debug, then any arguments to the program. The wrapper
15603 runs until it executes your program, and then @value{GDBN} gains control.
15605 You can use any program that eventually calls @code{execve} with
15606 its arguments as a wrapper. Several standard Unix utilities do
15607 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
15608 with @code{exec "$@@"} will also work.
15610 For example, you can use @code{env} to pass an environment variable to
15611 the debugged program, without setting the variable in @code{gdbserver}'s
15615 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
15618 @subsection Connecting to @code{gdbserver}
15620 Run @value{GDBN} on the host system.
15622 First make sure you have the necessary symbol files. Load symbols for
15623 your application using the @code{file} command before you connect. Use
15624 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
15625 was compiled with the correct sysroot using @code{--with-sysroot}).
15627 The symbol file and target libraries must exactly match the executable
15628 and libraries on the target, with one exception: the files on the host
15629 system should not be stripped, even if the files on the target system
15630 are. Mismatched or missing files will lead to confusing results
15631 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
15632 files may also prevent @code{gdbserver} from debugging multi-threaded
15635 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
15636 For TCP connections, you must start up @code{gdbserver} prior to using
15637 the @code{target remote} command. Otherwise you may get an error whose
15638 text depends on the host system, but which usually looks something like
15639 @samp{Connection refused}. Don't use the @code{load}
15640 command in @value{GDBN} when using @code{gdbserver}, since the program is
15641 already on the target.
15643 @subsection Monitor Commands for @code{gdbserver}
15644 @cindex monitor commands, for @code{gdbserver}
15645 @anchor{Monitor Commands for gdbserver}
15647 During a @value{GDBN} session using @code{gdbserver}, you can use the
15648 @code{monitor} command to send special requests to @code{gdbserver}.
15649 Here are the available commands.
15653 List the available monitor commands.
15655 @item monitor set debug 0
15656 @itemx monitor set debug 1
15657 Disable or enable general debugging messages.
15659 @item monitor set remote-debug 0
15660 @itemx monitor set remote-debug 1
15661 Disable or enable specific debugging messages associated with the remote
15662 protocol (@pxref{Remote Protocol}).
15664 @item monitor set libthread-db-search-path [PATH]
15665 @cindex gdbserver, search path for @code{libthread_db}
15666 When this command is issued, @var{path} is a colon-separated list of
15667 directories to search for @code{libthread_db} (@pxref{Threads,,set
15668 libthread-db-search-path}). If you omit @var{path},
15669 @samp{libthread-db-search-path} will be reset to an empty list.
15672 Tell gdbserver to exit immediately. This command should be followed by
15673 @code{disconnect} to close the debugging session. @code{gdbserver} will
15674 detach from any attached processes and kill any processes it created.
15675 Use @code{monitor exit} to terminate @code{gdbserver} at the end
15676 of a multi-process mode debug session.
15680 @node Remote Configuration
15681 @section Remote Configuration
15684 @kindex show remote
15685 This section documents the configuration options available when
15686 debugging remote programs. For the options related to the File I/O
15687 extensions of the remote protocol, see @ref{system,
15688 system-call-allowed}.
15691 @item set remoteaddresssize @var{bits}
15692 @cindex address size for remote targets
15693 @cindex bits in remote address
15694 Set the maximum size of address in a memory packet to the specified
15695 number of bits. @value{GDBN} will mask off the address bits above
15696 that number, when it passes addresses to the remote target. The
15697 default value is the number of bits in the target's address.
15699 @item show remoteaddresssize
15700 Show the current value of remote address size in bits.
15702 @item set remotebaud @var{n}
15703 @cindex baud rate for remote targets
15704 Set the baud rate for the remote serial I/O to @var{n} baud. The
15705 value is used to set the speed of the serial port used for debugging
15708 @item show remotebaud
15709 Show the current speed of the remote connection.
15711 @item set remotebreak
15712 @cindex interrupt remote programs
15713 @cindex BREAK signal instead of Ctrl-C
15714 @anchor{set remotebreak}
15715 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
15716 when you type @kbd{Ctrl-c} to interrupt the program running
15717 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
15718 character instead. The default is off, since most remote systems
15719 expect to see @samp{Ctrl-C} as the interrupt signal.
15721 @item show remotebreak
15722 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
15723 interrupt the remote program.
15725 @item set remoteflow on
15726 @itemx set remoteflow off
15727 @kindex set remoteflow
15728 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
15729 on the serial port used to communicate to the remote target.
15731 @item show remoteflow
15732 @kindex show remoteflow
15733 Show the current setting of hardware flow control.
15735 @item set remotelogbase @var{base}
15736 Set the base (a.k.a.@: radix) of logging serial protocol
15737 communications to @var{base}. Supported values of @var{base} are:
15738 @code{ascii}, @code{octal}, and @code{hex}. The default is
15741 @item show remotelogbase
15742 Show the current setting of the radix for logging remote serial
15745 @item set remotelogfile @var{file}
15746 @cindex record serial communications on file
15747 Record remote serial communications on the named @var{file}. The
15748 default is not to record at all.
15750 @item show remotelogfile.
15751 Show the current setting of the file name on which to record the
15752 serial communications.
15754 @item set remotetimeout @var{num}
15755 @cindex timeout for serial communications
15756 @cindex remote timeout
15757 Set the timeout limit to wait for the remote target to respond to
15758 @var{num} seconds. The default is 2 seconds.
15760 @item show remotetimeout
15761 Show the current number of seconds to wait for the remote target
15764 @cindex limit hardware breakpoints and watchpoints
15765 @cindex remote target, limit break- and watchpoints
15766 @anchor{set remote hardware-watchpoint-limit}
15767 @anchor{set remote hardware-breakpoint-limit}
15768 @item set remote hardware-watchpoint-limit @var{limit}
15769 @itemx set remote hardware-breakpoint-limit @var{limit}
15770 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
15771 watchpoints. A limit of -1, the default, is treated as unlimited.
15773 @item set remote exec-file @var{filename}
15774 @itemx show remote exec-file
15775 @anchor{set remote exec-file}
15776 @cindex executable file, for remote target
15777 Select the file used for @code{run} with @code{target
15778 extended-remote}. This should be set to a filename valid on the
15779 target system. If it is not set, the target will use a default
15780 filename (e.g.@: the last program run).
15782 @item set remote interrupt-sequence
15783 @cindex interrupt remote programs
15784 @cindex select Ctrl-C, BREAK or BREAK-g
15785 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
15786 @samp{BREAK-g} as the
15787 sequence to the remote target in order to interrupt the execution.
15788 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
15789 is high level of serial line for some certain time.
15790 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
15791 It is @code{BREAK} signal followed by character @code{g}.
15793 @item show interrupt-sequence
15794 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
15795 is sent by @value{GDBN} to interrupt the remote program.
15796 @code{BREAK-g} is BREAK signal followed by @code{g} and
15797 also known as Magic SysRq g.
15799 @item set remote interrupt-on-connect
15800 @cindex send interrupt-sequence on start
15801 Specify whether interrupt-sequence is sent to remote target when
15802 @value{GDBN} connects to it. This is mostly needed when you debug
15803 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
15804 which is known as Magic SysRq g in order to connect @value{GDBN}.
15806 @item show interrupt-on-connect
15807 Show whether interrupt-sequence is sent
15808 to remote target when @value{GDBN} connects to it.
15812 @item set tcp auto-retry on
15813 @cindex auto-retry, for remote TCP target
15814 Enable auto-retry for remote TCP connections. This is useful if the remote
15815 debugging agent is launched in parallel with @value{GDBN}; there is a race
15816 condition because the agent may not become ready to accept the connection
15817 before @value{GDBN} attempts to connect. When auto-retry is
15818 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
15819 to establish the connection using the timeout specified by
15820 @code{set tcp connect-timeout}.
15822 @item set tcp auto-retry off
15823 Do not auto-retry failed TCP connections.
15825 @item show tcp auto-retry
15826 Show the current auto-retry setting.
15828 @item set tcp connect-timeout @var{seconds}
15829 @cindex connection timeout, for remote TCP target
15830 @cindex timeout, for remote target connection
15831 Set the timeout for establishing a TCP connection to the remote target to
15832 @var{seconds}. The timeout affects both polling to retry failed connections
15833 (enabled by @code{set tcp auto-retry on}) and waiting for connections
15834 that are merely slow to complete, and represents an approximate cumulative
15837 @item show tcp connect-timeout
15838 Show the current connection timeout setting.
15841 @cindex remote packets, enabling and disabling
15842 The @value{GDBN} remote protocol autodetects the packets supported by
15843 your debugging stub. If you need to override the autodetection, you
15844 can use these commands to enable or disable individual packets. Each
15845 packet can be set to @samp{on} (the remote target supports this
15846 packet), @samp{off} (the remote target does not support this packet),
15847 or @samp{auto} (detect remote target support for this packet). They
15848 all default to @samp{auto}. For more information about each packet,
15849 see @ref{Remote Protocol}.
15851 During normal use, you should not have to use any of these commands.
15852 If you do, that may be a bug in your remote debugging stub, or a bug
15853 in @value{GDBN}. You may want to report the problem to the
15854 @value{GDBN} developers.
15856 For each packet @var{name}, the command to enable or disable the
15857 packet is @code{set remote @var{name}-packet}. The available settings
15860 @multitable @columnfractions 0.28 0.32 0.25
15863 @tab Related Features
15865 @item @code{fetch-register}
15867 @tab @code{info registers}
15869 @item @code{set-register}
15873 @item @code{binary-download}
15875 @tab @code{load}, @code{set}
15877 @item @code{read-aux-vector}
15878 @tab @code{qXfer:auxv:read}
15879 @tab @code{info auxv}
15881 @item @code{symbol-lookup}
15882 @tab @code{qSymbol}
15883 @tab Detecting multiple threads
15885 @item @code{attach}
15886 @tab @code{vAttach}
15889 @item @code{verbose-resume}
15891 @tab Stepping or resuming multiple threads
15897 @item @code{software-breakpoint}
15901 @item @code{hardware-breakpoint}
15905 @item @code{write-watchpoint}
15909 @item @code{read-watchpoint}
15913 @item @code{access-watchpoint}
15917 @item @code{target-features}
15918 @tab @code{qXfer:features:read}
15919 @tab @code{set architecture}
15921 @item @code{library-info}
15922 @tab @code{qXfer:libraries:read}
15923 @tab @code{info sharedlibrary}
15925 @item @code{memory-map}
15926 @tab @code{qXfer:memory-map:read}
15927 @tab @code{info mem}
15929 @item @code{read-spu-object}
15930 @tab @code{qXfer:spu:read}
15931 @tab @code{info spu}
15933 @item @code{write-spu-object}
15934 @tab @code{qXfer:spu:write}
15935 @tab @code{info spu}
15937 @item @code{read-siginfo-object}
15938 @tab @code{qXfer:siginfo:read}
15939 @tab @code{print $_siginfo}
15941 @item @code{write-siginfo-object}
15942 @tab @code{qXfer:siginfo:write}
15943 @tab @code{set $_siginfo}
15945 @item @code{threads}
15946 @tab @code{qXfer:threads:read}
15947 @tab @code{info threads}
15949 @item @code{get-thread-local-@*storage-address}
15950 @tab @code{qGetTLSAddr}
15951 @tab Displaying @code{__thread} variables
15953 @item @code{get-thread-information-block-address}
15954 @tab @code{qGetTIBAddr}
15955 @tab Display MS-Windows Thread Information Block.
15957 @item @code{search-memory}
15958 @tab @code{qSearch:memory}
15961 @item @code{supported-packets}
15962 @tab @code{qSupported}
15963 @tab Remote communications parameters
15965 @item @code{pass-signals}
15966 @tab @code{QPassSignals}
15967 @tab @code{handle @var{signal}}
15969 @item @code{hostio-close-packet}
15970 @tab @code{vFile:close}
15971 @tab @code{remote get}, @code{remote put}
15973 @item @code{hostio-open-packet}
15974 @tab @code{vFile:open}
15975 @tab @code{remote get}, @code{remote put}
15977 @item @code{hostio-pread-packet}
15978 @tab @code{vFile:pread}
15979 @tab @code{remote get}, @code{remote put}
15981 @item @code{hostio-pwrite-packet}
15982 @tab @code{vFile:pwrite}
15983 @tab @code{remote get}, @code{remote put}
15985 @item @code{hostio-unlink-packet}
15986 @tab @code{vFile:unlink}
15987 @tab @code{remote delete}
15989 @item @code{noack-packet}
15990 @tab @code{QStartNoAckMode}
15991 @tab Packet acknowledgment
15993 @item @code{osdata}
15994 @tab @code{qXfer:osdata:read}
15995 @tab @code{info os}
15997 @item @code{query-attached}
15998 @tab @code{qAttached}
15999 @tab Querying remote process attach state.
16003 @section Implementing a Remote Stub
16005 @cindex debugging stub, example
16006 @cindex remote stub, example
16007 @cindex stub example, remote debugging
16008 The stub files provided with @value{GDBN} implement the target side of the
16009 communication protocol, and the @value{GDBN} side is implemented in the
16010 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16011 these subroutines to communicate, and ignore the details. (If you're
16012 implementing your own stub file, you can still ignore the details: start
16013 with one of the existing stub files. @file{sparc-stub.c} is the best
16014 organized, and therefore the easiest to read.)
16016 @cindex remote serial debugging, overview
16017 To debug a program running on another machine (the debugging
16018 @dfn{target} machine), you must first arrange for all the usual
16019 prerequisites for the program to run by itself. For example, for a C
16024 A startup routine to set up the C runtime environment; these usually
16025 have a name like @file{crt0}. The startup routine may be supplied by
16026 your hardware supplier, or you may have to write your own.
16029 A C subroutine library to support your program's
16030 subroutine calls, notably managing input and output.
16033 A way of getting your program to the other machine---for example, a
16034 download program. These are often supplied by the hardware
16035 manufacturer, but you may have to write your own from hardware
16039 The next step is to arrange for your program to use a serial port to
16040 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16041 machine). In general terms, the scheme looks like this:
16045 @value{GDBN} already understands how to use this protocol; when everything
16046 else is set up, you can simply use the @samp{target remote} command
16047 (@pxref{Targets,,Specifying a Debugging Target}).
16049 @item On the target,
16050 you must link with your program a few special-purpose subroutines that
16051 implement the @value{GDBN} remote serial protocol. The file containing these
16052 subroutines is called a @dfn{debugging stub}.
16054 On certain remote targets, you can use an auxiliary program
16055 @code{gdbserver} instead of linking a stub into your program.
16056 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16059 The debugging stub is specific to the architecture of the remote
16060 machine; for example, use @file{sparc-stub.c} to debug programs on
16063 @cindex remote serial stub list
16064 These working remote stubs are distributed with @value{GDBN}:
16069 @cindex @file{i386-stub.c}
16072 For Intel 386 and compatible architectures.
16075 @cindex @file{m68k-stub.c}
16076 @cindex Motorola 680x0
16078 For Motorola 680x0 architectures.
16081 @cindex @file{sh-stub.c}
16084 For Renesas SH architectures.
16087 @cindex @file{sparc-stub.c}
16089 For @sc{sparc} architectures.
16091 @item sparcl-stub.c
16092 @cindex @file{sparcl-stub.c}
16095 For Fujitsu @sc{sparclite} architectures.
16099 The @file{README} file in the @value{GDBN} distribution may list other
16100 recently added stubs.
16103 * Stub Contents:: What the stub can do for you
16104 * Bootstrapping:: What you must do for the stub
16105 * Debug Session:: Putting it all together
16108 @node Stub Contents
16109 @subsection What the Stub Can Do for You
16111 @cindex remote serial stub
16112 The debugging stub for your architecture supplies these three
16116 @item set_debug_traps
16117 @findex set_debug_traps
16118 @cindex remote serial stub, initialization
16119 This routine arranges for @code{handle_exception} to run when your
16120 program stops. You must call this subroutine explicitly near the
16121 beginning of your program.
16123 @item handle_exception
16124 @findex handle_exception
16125 @cindex remote serial stub, main routine
16126 This is the central workhorse, but your program never calls it
16127 explicitly---the setup code arranges for @code{handle_exception} to
16128 run when a trap is triggered.
16130 @code{handle_exception} takes control when your program stops during
16131 execution (for example, on a breakpoint), and mediates communications
16132 with @value{GDBN} on the host machine. This is where the communications
16133 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16134 representative on the target machine. It begins by sending summary
16135 information on the state of your program, then continues to execute,
16136 retrieving and transmitting any information @value{GDBN} needs, until you
16137 execute a @value{GDBN} command that makes your program resume; at that point,
16138 @code{handle_exception} returns control to your own code on the target
16142 @cindex @code{breakpoint} subroutine, remote
16143 Use this auxiliary subroutine to make your program contain a
16144 breakpoint. Depending on the particular situation, this may be the only
16145 way for @value{GDBN} to get control. For instance, if your target
16146 machine has some sort of interrupt button, you won't need to call this;
16147 pressing the interrupt button transfers control to
16148 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16149 simply receiving characters on the serial port may also trigger a trap;
16150 again, in that situation, you don't need to call @code{breakpoint} from
16151 your own program---simply running @samp{target remote} from the host
16152 @value{GDBN} session gets control.
16154 Call @code{breakpoint} if none of these is true, or if you simply want
16155 to make certain your program stops at a predetermined point for the
16156 start of your debugging session.
16159 @node Bootstrapping
16160 @subsection What You Must Do for the Stub
16162 @cindex remote stub, support routines
16163 The debugging stubs that come with @value{GDBN} are set up for a particular
16164 chip architecture, but they have no information about the rest of your
16165 debugging target machine.
16167 First of all you need to tell the stub how to communicate with the
16171 @item int getDebugChar()
16172 @findex getDebugChar
16173 Write this subroutine to read a single character from the serial port.
16174 It may be identical to @code{getchar} for your target system; a
16175 different name is used to allow you to distinguish the two if you wish.
16177 @item void putDebugChar(int)
16178 @findex putDebugChar
16179 Write this subroutine to write a single character to the serial port.
16180 It may be identical to @code{putchar} for your target system; a
16181 different name is used to allow you to distinguish the two if you wish.
16184 @cindex control C, and remote debugging
16185 @cindex interrupting remote targets
16186 If you want @value{GDBN} to be able to stop your program while it is
16187 running, you need to use an interrupt-driven serial driver, and arrange
16188 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16189 character). That is the character which @value{GDBN} uses to tell the
16190 remote system to stop.
16192 Getting the debugging target to return the proper status to @value{GDBN}
16193 probably requires changes to the standard stub; one quick and dirty way
16194 is to just execute a breakpoint instruction (the ``dirty'' part is that
16195 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16197 Other routines you need to supply are:
16200 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16201 @findex exceptionHandler
16202 Write this function to install @var{exception_address} in the exception
16203 handling tables. You need to do this because the stub does not have any
16204 way of knowing what the exception handling tables on your target system
16205 are like (for example, the processor's table might be in @sc{rom},
16206 containing entries which point to a table in @sc{ram}).
16207 @var{exception_number} is the exception number which should be changed;
16208 its meaning is architecture-dependent (for example, different numbers
16209 might represent divide by zero, misaligned access, etc). When this
16210 exception occurs, control should be transferred directly to
16211 @var{exception_address}, and the processor state (stack, registers,
16212 and so on) should be just as it is when a processor exception occurs. So if
16213 you want to use a jump instruction to reach @var{exception_address}, it
16214 should be a simple jump, not a jump to subroutine.
16216 For the 386, @var{exception_address} should be installed as an interrupt
16217 gate so that interrupts are masked while the handler runs. The gate
16218 should be at privilege level 0 (the most privileged level). The
16219 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16220 help from @code{exceptionHandler}.
16222 @item void flush_i_cache()
16223 @findex flush_i_cache
16224 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16225 instruction cache, if any, on your target machine. If there is no
16226 instruction cache, this subroutine may be a no-op.
16228 On target machines that have instruction caches, @value{GDBN} requires this
16229 function to make certain that the state of your program is stable.
16233 You must also make sure this library routine is available:
16236 @item void *memset(void *, int, int)
16238 This is the standard library function @code{memset} that sets an area of
16239 memory to a known value. If you have one of the free versions of
16240 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16241 either obtain it from your hardware manufacturer, or write your own.
16244 If you do not use the GNU C compiler, you may need other standard
16245 library subroutines as well; this varies from one stub to another,
16246 but in general the stubs are likely to use any of the common library
16247 subroutines which @code{@value{NGCC}} generates as inline code.
16250 @node Debug Session
16251 @subsection Putting it All Together
16253 @cindex remote serial debugging summary
16254 In summary, when your program is ready to debug, you must follow these
16259 Make sure you have defined the supporting low-level routines
16260 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16262 @code{getDebugChar}, @code{putDebugChar},
16263 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16267 Insert these lines near the top of your program:
16275 For the 680x0 stub only, you need to provide a variable called
16276 @code{exceptionHook}. Normally you just use:
16279 void (*exceptionHook)() = 0;
16283 but if before calling @code{set_debug_traps}, you set it to point to a
16284 function in your program, that function is called when
16285 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
16286 error). The function indicated by @code{exceptionHook} is called with
16287 one parameter: an @code{int} which is the exception number.
16290 Compile and link together: your program, the @value{GDBN} debugging stub for
16291 your target architecture, and the supporting subroutines.
16294 Make sure you have a serial connection between your target machine and
16295 the @value{GDBN} host, and identify the serial port on the host.
16298 @c The "remote" target now provides a `load' command, so we should
16299 @c document that. FIXME.
16300 Download your program to your target machine (or get it there by
16301 whatever means the manufacturer provides), and start it.
16304 Start @value{GDBN} on the host, and connect to the target
16305 (@pxref{Connecting,,Connecting to a Remote Target}).
16309 @node Configurations
16310 @chapter Configuration-Specific Information
16312 While nearly all @value{GDBN} commands are available for all native and
16313 cross versions of the debugger, there are some exceptions. This chapter
16314 describes things that are only available in certain configurations.
16316 There are three major categories of configurations: native
16317 configurations, where the host and target are the same, embedded
16318 operating system configurations, which are usually the same for several
16319 different processor architectures, and bare embedded processors, which
16320 are quite different from each other.
16325 * Embedded Processors::
16332 This section describes details specific to particular native
16337 * BSD libkvm Interface:: Debugging BSD kernel memory images
16338 * SVR4 Process Information:: SVR4 process information
16339 * DJGPP Native:: Features specific to the DJGPP port
16340 * Cygwin Native:: Features specific to the Cygwin port
16341 * Hurd Native:: Features specific to @sc{gnu} Hurd
16342 * Neutrino:: Features specific to QNX Neutrino
16343 * Darwin:: Features specific to Darwin
16349 On HP-UX systems, if you refer to a function or variable name that
16350 begins with a dollar sign, @value{GDBN} searches for a user or system
16351 name first, before it searches for a convenience variable.
16354 @node BSD libkvm Interface
16355 @subsection BSD libkvm Interface
16358 @cindex kernel memory image
16359 @cindex kernel crash dump
16361 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
16362 interface that provides a uniform interface for accessing kernel virtual
16363 memory images, including live systems and crash dumps. @value{GDBN}
16364 uses this interface to allow you to debug live kernels and kernel crash
16365 dumps on many native BSD configurations. This is implemented as a
16366 special @code{kvm} debugging target. For debugging a live system, load
16367 the currently running kernel into @value{GDBN} and connect to the
16371 (@value{GDBP}) @b{target kvm}
16374 For debugging crash dumps, provide the file name of the crash dump as an
16378 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
16381 Once connected to the @code{kvm} target, the following commands are
16387 Set current context from the @dfn{Process Control Block} (PCB) address.
16390 Set current context from proc address. This command isn't available on
16391 modern FreeBSD systems.
16394 @node SVR4 Process Information
16395 @subsection SVR4 Process Information
16397 @cindex examine process image
16398 @cindex process info via @file{/proc}
16400 Many versions of SVR4 and compatible systems provide a facility called
16401 @samp{/proc} that can be used to examine the image of a running
16402 process using file-system subroutines. If @value{GDBN} is configured
16403 for an operating system with this facility, the command @code{info
16404 proc} is available to report information about the process running
16405 your program, or about any process running on your system. @code{info
16406 proc} works only on SVR4 systems that include the @code{procfs} code.
16407 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
16408 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
16414 @itemx info proc @var{process-id}
16415 Summarize available information about any running process. If a
16416 process ID is specified by @var{process-id}, display information about
16417 that process; otherwise display information about the program being
16418 debugged. The summary includes the debugged process ID, the command
16419 line used to invoke it, its current working directory, and its
16420 executable file's absolute file name.
16422 On some systems, @var{process-id} can be of the form
16423 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
16424 within a process. If the optional @var{pid} part is missing, it means
16425 a thread from the process being debugged (the leading @samp{/} still
16426 needs to be present, or else @value{GDBN} will interpret the number as
16427 a process ID rather than a thread ID).
16429 @item info proc mappings
16430 @cindex memory address space mappings
16431 Report the memory address space ranges accessible in the program, with
16432 information on whether the process has read, write, or execute access
16433 rights to each range. On @sc{gnu}/Linux systems, each memory range
16434 includes the object file which is mapped to that range, instead of the
16435 memory access rights to that range.
16437 @item info proc stat
16438 @itemx info proc status
16439 @cindex process detailed status information
16440 These subcommands are specific to @sc{gnu}/Linux systems. They show
16441 the process-related information, including the user ID and group ID;
16442 how many threads are there in the process; its virtual memory usage;
16443 the signals that are pending, blocked, and ignored; its TTY; its
16444 consumption of system and user time; its stack size; its @samp{nice}
16445 value; etc. For more information, see the @samp{proc} man page
16446 (type @kbd{man 5 proc} from your shell prompt).
16448 @item info proc all
16449 Show all the information about the process described under all of the
16450 above @code{info proc} subcommands.
16453 @comment These sub-options of 'info proc' were not included when
16454 @comment procfs.c was re-written. Keep their descriptions around
16455 @comment against the day when someone finds the time to put them back in.
16456 @kindex info proc times
16457 @item info proc times
16458 Starting time, user CPU time, and system CPU time for your program and
16461 @kindex info proc id
16463 Report on the process IDs related to your program: its own process ID,
16464 the ID of its parent, the process group ID, and the session ID.
16467 @item set procfs-trace
16468 @kindex set procfs-trace
16469 @cindex @code{procfs} API calls
16470 This command enables and disables tracing of @code{procfs} API calls.
16472 @item show procfs-trace
16473 @kindex show procfs-trace
16474 Show the current state of @code{procfs} API call tracing.
16476 @item set procfs-file @var{file}
16477 @kindex set procfs-file
16478 Tell @value{GDBN} to write @code{procfs} API trace to the named
16479 @var{file}. @value{GDBN} appends the trace info to the previous
16480 contents of the file. The default is to display the trace on the
16483 @item show procfs-file
16484 @kindex show procfs-file
16485 Show the file to which @code{procfs} API trace is written.
16487 @item proc-trace-entry
16488 @itemx proc-trace-exit
16489 @itemx proc-untrace-entry
16490 @itemx proc-untrace-exit
16491 @kindex proc-trace-entry
16492 @kindex proc-trace-exit
16493 @kindex proc-untrace-entry
16494 @kindex proc-untrace-exit
16495 These commands enable and disable tracing of entries into and exits
16496 from the @code{syscall} interface.
16499 @kindex info pidlist
16500 @cindex process list, QNX Neutrino
16501 For QNX Neutrino only, this command displays the list of all the
16502 processes and all the threads within each process.
16505 @kindex info meminfo
16506 @cindex mapinfo list, QNX Neutrino
16507 For QNX Neutrino only, this command displays the list of all mapinfos.
16511 @subsection Features for Debugging @sc{djgpp} Programs
16512 @cindex @sc{djgpp} debugging
16513 @cindex native @sc{djgpp} debugging
16514 @cindex MS-DOS-specific commands
16517 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
16518 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
16519 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
16520 top of real-mode DOS systems and their emulations.
16522 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
16523 defines a few commands specific to the @sc{djgpp} port. This
16524 subsection describes those commands.
16529 This is a prefix of @sc{djgpp}-specific commands which print
16530 information about the target system and important OS structures.
16533 @cindex MS-DOS system info
16534 @cindex free memory information (MS-DOS)
16535 @item info dos sysinfo
16536 This command displays assorted information about the underlying
16537 platform: the CPU type and features, the OS version and flavor, the
16538 DPMI version, and the available conventional and DPMI memory.
16543 @cindex segment descriptor tables
16544 @cindex descriptor tables display
16546 @itemx info dos ldt
16547 @itemx info dos idt
16548 These 3 commands display entries from, respectively, Global, Local,
16549 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
16550 tables are data structures which store a descriptor for each segment
16551 that is currently in use. The segment's selector is an index into a
16552 descriptor table; the table entry for that index holds the
16553 descriptor's base address and limit, and its attributes and access
16556 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
16557 segment (used for both data and the stack), and a DOS segment (which
16558 allows access to DOS/BIOS data structures and absolute addresses in
16559 conventional memory). However, the DPMI host will usually define
16560 additional segments in order to support the DPMI environment.
16562 @cindex garbled pointers
16563 These commands allow to display entries from the descriptor tables.
16564 Without an argument, all entries from the specified table are
16565 displayed. An argument, which should be an integer expression, means
16566 display a single entry whose index is given by the argument. For
16567 example, here's a convenient way to display information about the
16568 debugged program's data segment:
16571 @exdent @code{(@value{GDBP}) info dos ldt $ds}
16572 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
16576 This comes in handy when you want to see whether a pointer is outside
16577 the data segment's limit (i.e.@: @dfn{garbled}).
16579 @cindex page tables display (MS-DOS)
16581 @itemx info dos pte
16582 These two commands display entries from, respectively, the Page
16583 Directory and the Page Tables. Page Directories and Page Tables are
16584 data structures which control how virtual memory addresses are mapped
16585 into physical addresses. A Page Table includes an entry for every
16586 page of memory that is mapped into the program's address space; there
16587 may be several Page Tables, each one holding up to 4096 entries. A
16588 Page Directory has up to 4096 entries, one each for every Page Table
16589 that is currently in use.
16591 Without an argument, @kbd{info dos pde} displays the entire Page
16592 Directory, and @kbd{info dos pte} displays all the entries in all of
16593 the Page Tables. An argument, an integer expression, given to the
16594 @kbd{info dos pde} command means display only that entry from the Page
16595 Directory table. An argument given to the @kbd{info dos pte} command
16596 means display entries from a single Page Table, the one pointed to by
16597 the specified entry in the Page Directory.
16599 @cindex direct memory access (DMA) on MS-DOS
16600 These commands are useful when your program uses @dfn{DMA} (Direct
16601 Memory Access), which needs physical addresses to program the DMA
16604 These commands are supported only with some DPMI servers.
16606 @cindex physical address from linear address
16607 @item info dos address-pte @var{addr}
16608 This command displays the Page Table entry for a specified linear
16609 address. The argument @var{addr} is a linear address which should
16610 already have the appropriate segment's base address added to it,
16611 because this command accepts addresses which may belong to @emph{any}
16612 segment. For example, here's how to display the Page Table entry for
16613 the page where a variable @code{i} is stored:
16616 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
16617 @exdent @code{Page Table entry for address 0x11a00d30:}
16618 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
16622 This says that @code{i} is stored at offset @code{0xd30} from the page
16623 whose physical base address is @code{0x02698000}, and shows all the
16624 attributes of that page.
16626 Note that you must cast the addresses of variables to a @code{char *},
16627 since otherwise the value of @code{__djgpp_base_address}, the base
16628 address of all variables and functions in a @sc{djgpp} program, will
16629 be added using the rules of C pointer arithmetics: if @code{i} is
16630 declared an @code{int}, @value{GDBN} will add 4 times the value of
16631 @code{__djgpp_base_address} to the address of @code{i}.
16633 Here's another example, it displays the Page Table entry for the
16637 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
16638 @exdent @code{Page Table entry for address 0x29110:}
16639 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
16643 (The @code{+ 3} offset is because the transfer buffer's address is the
16644 3rd member of the @code{_go32_info_block} structure.) The output
16645 clearly shows that this DPMI server maps the addresses in conventional
16646 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
16647 linear (@code{0x29110}) addresses are identical.
16649 This command is supported only with some DPMI servers.
16652 @cindex DOS serial data link, remote debugging
16653 In addition to native debugging, the DJGPP port supports remote
16654 debugging via a serial data link. The following commands are specific
16655 to remote serial debugging in the DJGPP port of @value{GDBN}.
16658 @kindex set com1base
16659 @kindex set com1irq
16660 @kindex set com2base
16661 @kindex set com2irq
16662 @kindex set com3base
16663 @kindex set com3irq
16664 @kindex set com4base
16665 @kindex set com4irq
16666 @item set com1base @var{addr}
16667 This command sets the base I/O port address of the @file{COM1} serial
16670 @item set com1irq @var{irq}
16671 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
16672 for the @file{COM1} serial port.
16674 There are similar commands @samp{set com2base}, @samp{set com3irq},
16675 etc.@: for setting the port address and the @code{IRQ} lines for the
16678 @kindex show com1base
16679 @kindex show com1irq
16680 @kindex show com2base
16681 @kindex show com2irq
16682 @kindex show com3base
16683 @kindex show com3irq
16684 @kindex show com4base
16685 @kindex show com4irq
16686 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
16687 display the current settings of the base address and the @code{IRQ}
16688 lines used by the COM ports.
16691 @kindex info serial
16692 @cindex DOS serial port status
16693 This command prints the status of the 4 DOS serial ports. For each
16694 port, it prints whether it's active or not, its I/O base address and
16695 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
16696 counts of various errors encountered so far.
16700 @node Cygwin Native
16701 @subsection Features for Debugging MS Windows PE Executables
16702 @cindex MS Windows debugging
16703 @cindex native Cygwin debugging
16704 @cindex Cygwin-specific commands
16706 @value{GDBN} supports native debugging of MS Windows programs, including
16707 DLLs with and without symbolic debugging information.
16709 @cindex Ctrl-BREAK, MS-Windows
16710 @cindex interrupt debuggee on MS-Windows
16711 MS-Windows programs that call @code{SetConsoleMode} to switch off the
16712 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
16713 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
16714 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
16715 sequence, which can be used to interrupt the debuggee even if it
16718 There are various additional Cygwin-specific commands, described in
16719 this section. Working with DLLs that have no debugging symbols is
16720 described in @ref{Non-debug DLL Symbols}.
16725 This is a prefix of MS Windows-specific commands which print
16726 information about the target system and important OS structures.
16728 @item info w32 selector
16729 This command displays information returned by
16730 the Win32 API @code{GetThreadSelectorEntry} function.
16731 It takes an optional argument that is evaluated to
16732 a long value to give the information about this given selector.
16733 Without argument, this command displays information
16734 about the six segment registers.
16736 @item info w32 thread-information-block
16737 This command displays thread specific information stored in the
16738 Thread Information Block (readable on the X86 CPU family using @code{$fs}
16739 selector for 32-bit programs and @code{$gs} for 64-bit programs).
16743 This is a Cygwin-specific alias of @code{info shared}.
16745 @kindex dll-symbols
16747 This command loads symbols from a dll similarly to
16748 add-sym command but without the need to specify a base address.
16750 @kindex set cygwin-exceptions
16751 @cindex debugging the Cygwin DLL
16752 @cindex Cygwin DLL, debugging
16753 @item set cygwin-exceptions @var{mode}
16754 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
16755 happen inside the Cygwin DLL. If @var{mode} is @code{off},
16756 @value{GDBN} will delay recognition of exceptions, and may ignore some
16757 exceptions which seem to be caused by internal Cygwin DLL
16758 ``bookkeeping''. This option is meant primarily for debugging the
16759 Cygwin DLL itself; the default value is @code{off} to avoid annoying
16760 @value{GDBN} users with false @code{SIGSEGV} signals.
16762 @kindex show cygwin-exceptions
16763 @item show cygwin-exceptions
16764 Displays whether @value{GDBN} will break on exceptions that happen
16765 inside the Cygwin DLL itself.
16767 @kindex set new-console
16768 @item set new-console @var{mode}
16769 If @var{mode} is @code{on} the debuggee will
16770 be started in a new console on next start.
16771 If @var{mode} is @code{off}, the debuggee will
16772 be started in the same console as the debugger.
16774 @kindex show new-console
16775 @item show new-console
16776 Displays whether a new console is used
16777 when the debuggee is started.
16779 @kindex set new-group
16780 @item set new-group @var{mode}
16781 This boolean value controls whether the debuggee should
16782 start a new group or stay in the same group as the debugger.
16783 This affects the way the Windows OS handles
16786 @kindex show new-group
16787 @item show new-group
16788 Displays current value of new-group boolean.
16790 @kindex set debugevents
16791 @item set debugevents
16792 This boolean value adds debug output concerning kernel events related
16793 to the debuggee seen by the debugger. This includes events that
16794 signal thread and process creation and exit, DLL loading and
16795 unloading, console interrupts, and debugging messages produced by the
16796 Windows @code{OutputDebugString} API call.
16798 @kindex set debugexec
16799 @item set debugexec
16800 This boolean value adds debug output concerning execute events
16801 (such as resume thread) seen by the debugger.
16803 @kindex set debugexceptions
16804 @item set debugexceptions
16805 This boolean value adds debug output concerning exceptions in the
16806 debuggee seen by the debugger.
16808 @kindex set debugmemory
16809 @item set debugmemory
16810 This boolean value adds debug output concerning debuggee memory reads
16811 and writes by the debugger.
16815 This boolean values specifies whether the debuggee is called
16816 via a shell or directly (default value is on).
16820 Displays if the debuggee will be started with a shell.
16825 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
16828 @node Non-debug DLL Symbols
16829 @subsubsection Support for DLLs without Debugging Symbols
16830 @cindex DLLs with no debugging symbols
16831 @cindex Minimal symbols and DLLs
16833 Very often on windows, some of the DLLs that your program relies on do
16834 not include symbolic debugging information (for example,
16835 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
16836 symbols in a DLL, it relies on the minimal amount of symbolic
16837 information contained in the DLL's export table. This section
16838 describes working with such symbols, known internally to @value{GDBN} as
16839 ``minimal symbols''.
16841 Note that before the debugged program has started execution, no DLLs
16842 will have been loaded. The easiest way around this problem is simply to
16843 start the program --- either by setting a breakpoint or letting the
16844 program run once to completion. It is also possible to force
16845 @value{GDBN} to load a particular DLL before starting the executable ---
16846 see the shared library information in @ref{Files}, or the
16847 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
16848 explicitly loading symbols from a DLL with no debugging information will
16849 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
16850 which may adversely affect symbol lookup performance.
16852 @subsubsection DLL Name Prefixes
16854 In keeping with the naming conventions used by the Microsoft debugging
16855 tools, DLL export symbols are made available with a prefix based on the
16856 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
16857 also entered into the symbol table, so @code{CreateFileA} is often
16858 sufficient. In some cases there will be name clashes within a program
16859 (particularly if the executable itself includes full debugging symbols)
16860 necessitating the use of the fully qualified name when referring to the
16861 contents of the DLL. Use single-quotes around the name to avoid the
16862 exclamation mark (``!'') being interpreted as a language operator.
16864 Note that the internal name of the DLL may be all upper-case, even
16865 though the file name of the DLL is lower-case, or vice-versa. Since
16866 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
16867 some confusion. If in doubt, try the @code{info functions} and
16868 @code{info variables} commands or even @code{maint print msymbols}
16869 (@pxref{Symbols}). Here's an example:
16872 (@value{GDBP}) info function CreateFileA
16873 All functions matching regular expression "CreateFileA":
16875 Non-debugging symbols:
16876 0x77e885f4 CreateFileA
16877 0x77e885f4 KERNEL32!CreateFileA
16881 (@value{GDBP}) info function !
16882 All functions matching regular expression "!":
16884 Non-debugging symbols:
16885 0x6100114c cygwin1!__assert
16886 0x61004034 cygwin1!_dll_crt0@@0
16887 0x61004240 cygwin1!dll_crt0(per_process *)
16891 @subsubsection Working with Minimal Symbols
16893 Symbols extracted from a DLL's export table do not contain very much
16894 type information. All that @value{GDBN} can do is guess whether a symbol
16895 refers to a function or variable depending on the linker section that
16896 contains the symbol. Also note that the actual contents of the memory
16897 contained in a DLL are not available unless the program is running. This
16898 means that you cannot examine the contents of a variable or disassemble
16899 a function within a DLL without a running program.
16901 Variables are generally treated as pointers and dereferenced
16902 automatically. For this reason, it is often necessary to prefix a
16903 variable name with the address-of operator (``&'') and provide explicit
16904 type information in the command. Here's an example of the type of
16908 (@value{GDBP}) print 'cygwin1!__argv'
16913 (@value{GDBP}) x 'cygwin1!__argv'
16914 0x10021610: "\230y\""
16917 And two possible solutions:
16920 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
16921 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
16925 (@value{GDBP}) x/2x &'cygwin1!__argv'
16926 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
16927 (@value{GDBP}) x/x 0x10021608
16928 0x10021608: 0x0022fd98
16929 (@value{GDBP}) x/s 0x0022fd98
16930 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
16933 Setting a break point within a DLL is possible even before the program
16934 starts execution. However, under these circumstances, @value{GDBN} can't
16935 examine the initial instructions of the function in order to skip the
16936 function's frame set-up code. You can work around this by using ``*&''
16937 to set the breakpoint at a raw memory address:
16940 (@value{GDBP}) break *&'python22!PyOS_Readline'
16941 Breakpoint 1 at 0x1e04eff0
16944 The author of these extensions is not entirely convinced that setting a
16945 break point within a shared DLL like @file{kernel32.dll} is completely
16949 @subsection Commands Specific to @sc{gnu} Hurd Systems
16950 @cindex @sc{gnu} Hurd debugging
16952 This subsection describes @value{GDBN} commands specific to the
16953 @sc{gnu} Hurd native debugging.
16958 @kindex set signals@r{, Hurd command}
16959 @kindex set sigs@r{, Hurd command}
16960 This command toggles the state of inferior signal interception by
16961 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
16962 affected by this command. @code{sigs} is a shorthand alias for
16967 @kindex show signals@r{, Hurd command}
16968 @kindex show sigs@r{, Hurd command}
16969 Show the current state of intercepting inferior's signals.
16971 @item set signal-thread
16972 @itemx set sigthread
16973 @kindex set signal-thread
16974 @kindex set sigthread
16975 This command tells @value{GDBN} which thread is the @code{libc} signal
16976 thread. That thread is run when a signal is delivered to a running
16977 process. @code{set sigthread} is the shorthand alias of @code{set
16980 @item show signal-thread
16981 @itemx show sigthread
16982 @kindex show signal-thread
16983 @kindex show sigthread
16984 These two commands show which thread will run when the inferior is
16985 delivered a signal.
16988 @kindex set stopped@r{, Hurd command}
16989 This commands tells @value{GDBN} that the inferior process is stopped,
16990 as with the @code{SIGSTOP} signal. The stopped process can be
16991 continued by delivering a signal to it.
16994 @kindex show stopped@r{, Hurd command}
16995 This command shows whether @value{GDBN} thinks the debuggee is
16998 @item set exceptions
16999 @kindex set exceptions@r{, Hurd command}
17000 Use this command to turn off trapping of exceptions in the inferior.
17001 When exception trapping is off, neither breakpoints nor
17002 single-stepping will work. To restore the default, set exception
17005 @item show exceptions
17006 @kindex show exceptions@r{, Hurd command}
17007 Show the current state of trapping exceptions in the inferior.
17009 @item set task pause
17010 @kindex set task@r{, Hurd commands}
17011 @cindex task attributes (@sc{gnu} Hurd)
17012 @cindex pause current task (@sc{gnu} Hurd)
17013 This command toggles task suspension when @value{GDBN} has control.
17014 Setting it to on takes effect immediately, and the task is suspended
17015 whenever @value{GDBN} gets control. Setting it to off will take
17016 effect the next time the inferior is continued. If this option is set
17017 to off, you can use @code{set thread default pause on} or @code{set
17018 thread pause on} (see below) to pause individual threads.
17020 @item show task pause
17021 @kindex show task@r{, Hurd commands}
17022 Show the current state of task suspension.
17024 @item set task detach-suspend-count
17025 @cindex task suspend count
17026 @cindex detach from task, @sc{gnu} Hurd
17027 This command sets the suspend count the task will be left with when
17028 @value{GDBN} detaches from it.
17030 @item show task detach-suspend-count
17031 Show the suspend count the task will be left with when detaching.
17033 @item set task exception-port
17034 @itemx set task excp
17035 @cindex task exception port, @sc{gnu} Hurd
17036 This command sets the task exception port to which @value{GDBN} will
17037 forward exceptions. The argument should be the value of the @dfn{send
17038 rights} of the task. @code{set task excp} is a shorthand alias.
17040 @item set noninvasive
17041 @cindex noninvasive task options
17042 This command switches @value{GDBN} to a mode that is the least
17043 invasive as far as interfering with the inferior is concerned. This
17044 is the same as using @code{set task pause}, @code{set exceptions}, and
17045 @code{set signals} to values opposite to the defaults.
17047 @item info send-rights
17048 @itemx info receive-rights
17049 @itemx info port-rights
17050 @itemx info port-sets
17051 @itemx info dead-names
17054 @cindex send rights, @sc{gnu} Hurd
17055 @cindex receive rights, @sc{gnu} Hurd
17056 @cindex port rights, @sc{gnu} Hurd
17057 @cindex port sets, @sc{gnu} Hurd
17058 @cindex dead names, @sc{gnu} Hurd
17059 These commands display information about, respectively, send rights,
17060 receive rights, port rights, port sets, and dead names of a task.
17061 There are also shorthand aliases: @code{info ports} for @code{info
17062 port-rights} and @code{info psets} for @code{info port-sets}.
17064 @item set thread pause
17065 @kindex set thread@r{, Hurd command}
17066 @cindex thread properties, @sc{gnu} Hurd
17067 @cindex pause current thread (@sc{gnu} Hurd)
17068 This command toggles current thread suspension when @value{GDBN} has
17069 control. Setting it to on takes effect immediately, and the current
17070 thread is suspended whenever @value{GDBN} gets control. Setting it to
17071 off will take effect the next time the inferior is continued.
17072 Normally, this command has no effect, since when @value{GDBN} has
17073 control, the whole task is suspended. However, if you used @code{set
17074 task pause off} (see above), this command comes in handy to suspend
17075 only the current thread.
17077 @item show thread pause
17078 @kindex show thread@r{, Hurd command}
17079 This command shows the state of current thread suspension.
17081 @item set thread run
17082 This command sets whether the current thread is allowed to run.
17084 @item show thread run
17085 Show whether the current thread is allowed to run.
17087 @item set thread detach-suspend-count
17088 @cindex thread suspend count, @sc{gnu} Hurd
17089 @cindex detach from thread, @sc{gnu} Hurd
17090 This command sets the suspend count @value{GDBN} will leave on a
17091 thread when detaching. This number is relative to the suspend count
17092 found by @value{GDBN} when it notices the thread; use @code{set thread
17093 takeover-suspend-count} to force it to an absolute value.
17095 @item show thread detach-suspend-count
17096 Show the suspend count @value{GDBN} will leave on the thread when
17099 @item set thread exception-port
17100 @itemx set thread excp
17101 Set the thread exception port to which to forward exceptions. This
17102 overrides the port set by @code{set task exception-port} (see above).
17103 @code{set thread excp} is the shorthand alias.
17105 @item set thread takeover-suspend-count
17106 Normally, @value{GDBN}'s thread suspend counts are relative to the
17107 value @value{GDBN} finds when it notices each thread. This command
17108 changes the suspend counts to be absolute instead.
17110 @item set thread default
17111 @itemx show thread default
17112 @cindex thread default settings, @sc{gnu} Hurd
17113 Each of the above @code{set thread} commands has a @code{set thread
17114 default} counterpart (e.g., @code{set thread default pause}, @code{set
17115 thread default exception-port}, etc.). The @code{thread default}
17116 variety of commands sets the default thread properties for all
17117 threads; you can then change the properties of individual threads with
17118 the non-default commands.
17123 @subsection QNX Neutrino
17124 @cindex QNX Neutrino
17126 @value{GDBN} provides the following commands specific to the QNX
17130 @item set debug nto-debug
17131 @kindex set debug nto-debug
17132 When set to on, enables debugging messages specific to the QNX
17135 @item show debug nto-debug
17136 @kindex show debug nto-debug
17137 Show the current state of QNX Neutrino messages.
17144 @value{GDBN} provides the following commands specific to the Darwin target:
17147 @item set debug darwin @var{num}
17148 @kindex set debug darwin
17149 When set to a non zero value, enables debugging messages specific to
17150 the Darwin support. Higher values produce more verbose output.
17152 @item show debug darwin
17153 @kindex show debug darwin
17154 Show the current state of Darwin messages.
17156 @item set debug mach-o @var{num}
17157 @kindex set debug mach-o
17158 When set to a non zero value, enables debugging messages while
17159 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17160 file format used on Darwin for object and executable files.) Higher
17161 values produce more verbose output. This is a command to diagnose
17162 problems internal to @value{GDBN} and should not be needed in normal
17165 @item show debug mach-o
17166 @kindex show debug mach-o
17167 Show the current state of Mach-O file messages.
17169 @item set mach-exceptions on
17170 @itemx set mach-exceptions off
17171 @kindex set mach-exceptions
17172 On Darwin, faults are first reported as a Mach exception and are then
17173 mapped to a Posix signal. Use this command to turn on trapping of
17174 Mach exceptions in the inferior. This might be sometimes useful to
17175 better understand the cause of a fault. The default is off.
17177 @item show mach-exceptions
17178 @kindex show mach-exceptions
17179 Show the current state of exceptions trapping.
17184 @section Embedded Operating Systems
17186 This section describes configurations involving the debugging of
17187 embedded operating systems that are available for several different
17191 * VxWorks:: Using @value{GDBN} with VxWorks
17194 @value{GDBN} includes the ability to debug programs running on
17195 various real-time operating systems.
17198 @subsection Using @value{GDBN} with VxWorks
17204 @kindex target vxworks
17205 @item target vxworks @var{machinename}
17206 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17207 is the target system's machine name or IP address.
17211 On VxWorks, @code{load} links @var{filename} dynamically on the
17212 current target system as well as adding its symbols in @value{GDBN}.
17214 @value{GDBN} enables developers to spawn and debug tasks running on networked
17215 VxWorks targets from a Unix host. Already-running tasks spawned from
17216 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17217 both the Unix host and on the VxWorks target. The program
17218 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17219 installed with the name @code{vxgdb}, to distinguish it from a
17220 @value{GDBN} for debugging programs on the host itself.)
17223 @item VxWorks-timeout @var{args}
17224 @kindex vxworks-timeout
17225 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17226 This option is set by the user, and @var{args} represents the number of
17227 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17228 your VxWorks target is a slow software simulator or is on the far side
17229 of a thin network line.
17232 The following information on connecting to VxWorks was current when
17233 this manual was produced; newer releases of VxWorks may use revised
17236 @findex INCLUDE_RDB
17237 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17238 to include the remote debugging interface routines in the VxWorks
17239 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17240 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17241 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17242 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17243 information on configuring and remaking VxWorks, see the manufacturer's
17245 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17247 Once you have included @file{rdb.a} in your VxWorks system image and set
17248 your Unix execution search path to find @value{GDBN}, you are ready to
17249 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17250 @code{vxgdb}, depending on your installation).
17252 @value{GDBN} comes up showing the prompt:
17259 * VxWorks Connection:: Connecting to VxWorks
17260 * VxWorks Download:: VxWorks download
17261 * VxWorks Attach:: Running tasks
17264 @node VxWorks Connection
17265 @subsubsection Connecting to VxWorks
17267 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17268 network. To connect to a target whose host name is ``@code{tt}'', type:
17271 (vxgdb) target vxworks tt
17275 @value{GDBN} displays messages like these:
17278 Attaching remote machine across net...
17283 @value{GDBN} then attempts to read the symbol tables of any object modules
17284 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
17285 these files by searching the directories listed in the command search
17286 path (@pxref{Environment, ,Your Program's Environment}); if it fails
17287 to find an object file, it displays a message such as:
17290 prog.o: No such file or directory.
17293 When this happens, add the appropriate directory to the search path with
17294 the @value{GDBN} command @code{path}, and execute the @code{target}
17297 @node VxWorks Download
17298 @subsubsection VxWorks Download
17300 @cindex download to VxWorks
17301 If you have connected to the VxWorks target and you want to debug an
17302 object that has not yet been loaded, you can use the @value{GDBN}
17303 @code{load} command to download a file from Unix to VxWorks
17304 incrementally. The object file given as an argument to the @code{load}
17305 command is actually opened twice: first by the VxWorks target in order
17306 to download the code, then by @value{GDBN} in order to read the symbol
17307 table. This can lead to problems if the current working directories on
17308 the two systems differ. If both systems have NFS mounted the same
17309 filesystems, you can avoid these problems by using absolute paths.
17310 Otherwise, it is simplest to set the working directory on both systems
17311 to the directory in which the object file resides, and then to reference
17312 the file by its name, without any path. For instance, a program
17313 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
17314 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
17315 program, type this on VxWorks:
17318 -> cd "@var{vxpath}/vw/demo/rdb"
17322 Then, in @value{GDBN}, type:
17325 (vxgdb) cd @var{hostpath}/vw/demo/rdb
17326 (vxgdb) load prog.o
17329 @value{GDBN} displays a response similar to this:
17332 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
17335 You can also use the @code{load} command to reload an object module
17336 after editing and recompiling the corresponding source file. Note that
17337 this makes @value{GDBN} delete all currently-defined breakpoints,
17338 auto-displays, and convenience variables, and to clear the value
17339 history. (This is necessary in order to preserve the integrity of
17340 debugger's data structures that reference the target system's symbol
17343 @node VxWorks Attach
17344 @subsubsection Running Tasks
17346 @cindex running VxWorks tasks
17347 You can also attach to an existing task using the @code{attach} command as
17351 (vxgdb) attach @var{task}
17355 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
17356 or suspended when you attach to it. Running tasks are suspended at
17357 the time of attachment.
17359 @node Embedded Processors
17360 @section Embedded Processors
17362 This section goes into details specific to particular embedded
17365 @cindex send command to simulator
17366 Whenever a specific embedded processor has a simulator, @value{GDBN}
17367 allows to send an arbitrary command to the simulator.
17370 @item sim @var{command}
17371 @kindex sim@r{, a command}
17372 Send an arbitrary @var{command} string to the simulator. Consult the
17373 documentation for the specific simulator in use for information about
17374 acceptable commands.
17380 * M32R/D:: Renesas M32R/D
17381 * M68K:: Motorola M68K
17382 * MicroBlaze:: Xilinx MicroBlaze
17383 * MIPS Embedded:: MIPS Embedded
17384 * OpenRISC 1000:: OpenRisc 1000
17385 * PA:: HP PA Embedded
17386 * PowerPC Embedded:: PowerPC Embedded
17387 * Sparclet:: Tsqware Sparclet
17388 * Sparclite:: Fujitsu Sparclite
17389 * Z8000:: Zilog Z8000
17392 * Super-H:: Renesas Super-H
17401 @item target rdi @var{dev}
17402 ARM Angel monitor, via RDI library interface to ADP protocol. You may
17403 use this target to communicate with both boards running the Angel
17404 monitor, or with the EmbeddedICE JTAG debug device.
17407 @item target rdp @var{dev}
17412 @value{GDBN} provides the following ARM-specific commands:
17415 @item set arm disassembler
17417 This commands selects from a list of disassembly styles. The
17418 @code{"std"} style is the standard style.
17420 @item show arm disassembler
17422 Show the current disassembly style.
17424 @item set arm apcs32
17425 @cindex ARM 32-bit mode
17426 This command toggles ARM operation mode between 32-bit and 26-bit.
17428 @item show arm apcs32
17429 Display the current usage of the ARM 32-bit mode.
17431 @item set arm fpu @var{fputype}
17432 This command sets the ARM floating-point unit (FPU) type. The
17433 argument @var{fputype} can be one of these:
17437 Determine the FPU type by querying the OS ABI.
17439 Software FPU, with mixed-endian doubles on little-endian ARM
17442 GCC-compiled FPA co-processor.
17444 Software FPU with pure-endian doubles.
17450 Show the current type of the FPU.
17453 This command forces @value{GDBN} to use the specified ABI.
17456 Show the currently used ABI.
17458 @item set arm fallback-mode (arm|thumb|auto)
17459 @value{GDBN} uses the symbol table, when available, to determine
17460 whether instructions are ARM or Thumb. This command controls
17461 @value{GDBN}'s default behavior when the symbol table is not
17462 available. The default is @samp{auto}, which causes @value{GDBN} to
17463 use the current execution mode (from the @code{T} bit in the @code{CPSR}
17466 @item show arm fallback-mode
17467 Show the current fallback instruction mode.
17469 @item set arm force-mode (arm|thumb|auto)
17470 This command overrides use of the symbol table to determine whether
17471 instructions are ARM or Thumb. The default is @samp{auto}, which
17472 causes @value{GDBN} to use the symbol table and then the setting
17473 of @samp{set arm fallback-mode}.
17475 @item show arm force-mode
17476 Show the current forced instruction mode.
17478 @item set debug arm
17479 Toggle whether to display ARM-specific debugging messages from the ARM
17480 target support subsystem.
17482 @item show debug arm
17483 Show whether ARM-specific debugging messages are enabled.
17486 The following commands are available when an ARM target is debugged
17487 using the RDI interface:
17490 @item rdilogfile @r{[}@var{file}@r{]}
17492 @cindex ADP (Angel Debugger Protocol) logging
17493 Set the filename for the ADP (Angel Debugger Protocol) packet log.
17494 With an argument, sets the log file to the specified @var{file}. With
17495 no argument, show the current log file name. The default log file is
17498 @item rdilogenable @r{[}@var{arg}@r{]}
17499 @kindex rdilogenable
17500 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
17501 enables logging, with an argument 0 or @code{"no"} disables it. With
17502 no arguments displays the current setting. When logging is enabled,
17503 ADP packets exchanged between @value{GDBN} and the RDI target device
17504 are logged to a file.
17506 @item set rdiromatzero
17507 @kindex set rdiromatzero
17508 @cindex ROM at zero address, RDI
17509 Tell @value{GDBN} whether the target has ROM at address 0. If on,
17510 vector catching is disabled, so that zero address can be used. If off
17511 (the default), vector catching is enabled. For this command to take
17512 effect, it needs to be invoked prior to the @code{target rdi} command.
17514 @item show rdiromatzero
17515 @kindex show rdiromatzero
17516 Show the current setting of ROM at zero address.
17518 @item set rdiheartbeat
17519 @kindex set rdiheartbeat
17520 @cindex RDI heartbeat
17521 Enable or disable RDI heartbeat packets. It is not recommended to
17522 turn on this option, since it confuses ARM and EPI JTAG interface, as
17523 well as the Angel monitor.
17525 @item show rdiheartbeat
17526 @kindex show rdiheartbeat
17527 Show the setting of RDI heartbeat packets.
17531 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17532 The @value{GDBN} ARM simulator accepts the following optional arguments.
17535 @item --swi-support=@var{type}
17536 Tell the simulator which SWI interfaces to support.
17537 @var{type} may be a comma separated list of the following values.
17538 The default value is @code{all}.
17551 @subsection Renesas M32R/D and M32R/SDI
17554 @kindex target m32r
17555 @item target m32r @var{dev}
17556 Renesas M32R/D ROM monitor.
17558 @kindex target m32rsdi
17559 @item target m32rsdi @var{dev}
17560 Renesas M32R SDI server, connected via parallel port to the board.
17563 The following @value{GDBN} commands are specific to the M32R monitor:
17566 @item set download-path @var{path}
17567 @kindex set download-path
17568 @cindex find downloadable @sc{srec} files (M32R)
17569 Set the default path for finding downloadable @sc{srec} files.
17571 @item show download-path
17572 @kindex show download-path
17573 Show the default path for downloadable @sc{srec} files.
17575 @item set board-address @var{addr}
17576 @kindex set board-address
17577 @cindex M32-EVA target board address
17578 Set the IP address for the M32R-EVA target board.
17580 @item show board-address
17581 @kindex show board-address
17582 Show the current IP address of the target board.
17584 @item set server-address @var{addr}
17585 @kindex set server-address
17586 @cindex download server address (M32R)
17587 Set the IP address for the download server, which is the @value{GDBN}'s
17590 @item show server-address
17591 @kindex show server-address
17592 Display the IP address of the download server.
17594 @item upload @r{[}@var{file}@r{]}
17595 @kindex upload@r{, M32R}
17596 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
17597 upload capability. If no @var{file} argument is given, the current
17598 executable file is uploaded.
17600 @item tload @r{[}@var{file}@r{]}
17601 @kindex tload@r{, M32R}
17602 Test the @code{upload} command.
17605 The following commands are available for M32R/SDI:
17610 @cindex reset SDI connection, M32R
17611 This command resets the SDI connection.
17615 This command shows the SDI connection status.
17618 @kindex debug_chaos
17619 @cindex M32R/Chaos debugging
17620 Instructs the remote that M32R/Chaos debugging is to be used.
17622 @item use_debug_dma
17623 @kindex use_debug_dma
17624 Instructs the remote to use the DEBUG_DMA method of accessing memory.
17627 @kindex use_mon_code
17628 Instructs the remote to use the MON_CODE method of accessing memory.
17631 @kindex use_ib_break
17632 Instructs the remote to set breakpoints by IB break.
17634 @item use_dbt_break
17635 @kindex use_dbt_break
17636 Instructs the remote to set breakpoints by DBT.
17642 The Motorola m68k configuration includes ColdFire support, and a
17643 target command for the following ROM monitor.
17647 @kindex target dbug
17648 @item target dbug @var{dev}
17649 dBUG ROM monitor for Motorola ColdFire.
17654 @subsection MicroBlaze
17655 @cindex Xilinx MicroBlaze
17656 @cindex XMD, Xilinx Microprocessor Debugger
17658 The MicroBlaze is a soft-core processor supported on various Xilinx
17659 FPGAs, such as Spartan or Virtex series. Boards with these processors
17660 usually have JTAG ports which connect to a host system running the Xilinx
17661 Embedded Development Kit (EDK) or Software Development Kit (SDK).
17662 This host system is used to download the configuration bitstream to
17663 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
17664 communicates with the target board using the JTAG interface and
17665 presents a @code{gdbserver} interface to the board. By default
17666 @code{xmd} uses port @code{1234}. (While it is possible to change
17667 this default port, it requires the use of undocumented @code{xmd}
17668 commands. Contact Xilinx support if you need to do this.)
17670 Use these GDB commands to connect to the MicroBlaze target processor.
17673 @item target remote :1234
17674 Use this command to connect to the target if you are running @value{GDBN}
17675 on the same system as @code{xmd}.
17677 @item target remote @var{xmd-host}:1234
17678 Use this command to connect to the target if it is connected to @code{xmd}
17679 running on a different system named @var{xmd-host}.
17682 Use this command to download a program to the MicroBlaze target.
17684 @item set debug microblaze @var{n}
17685 Enable MicroBlaze-specific debugging messages if non-zero.
17687 @item show debug microblaze @var{n}
17688 Show MicroBlaze-specific debugging level.
17691 @node MIPS Embedded
17692 @subsection MIPS Embedded
17694 @cindex MIPS boards
17695 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
17696 MIPS board attached to a serial line. This is available when
17697 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
17700 Use these @value{GDBN} commands to specify the connection to your target board:
17703 @item target mips @var{port}
17704 @kindex target mips @var{port}
17705 To run a program on the board, start up @code{@value{GDBP}} with the
17706 name of your program as the argument. To connect to the board, use the
17707 command @samp{target mips @var{port}}, where @var{port} is the name of
17708 the serial port connected to the board. If the program has not already
17709 been downloaded to the board, you may use the @code{load} command to
17710 download it. You can then use all the usual @value{GDBN} commands.
17712 For example, this sequence connects to the target board through a serial
17713 port, and loads and runs a program called @var{prog} through the
17717 host$ @value{GDBP} @var{prog}
17718 @value{GDBN} is free software and @dots{}
17719 (@value{GDBP}) target mips /dev/ttyb
17720 (@value{GDBP}) load @var{prog}
17724 @item target mips @var{hostname}:@var{portnumber}
17725 On some @value{GDBN} host configurations, you can specify a TCP
17726 connection (for instance, to a serial line managed by a terminal
17727 concentrator) instead of a serial port, using the syntax
17728 @samp{@var{hostname}:@var{portnumber}}.
17730 @item target pmon @var{port}
17731 @kindex target pmon @var{port}
17734 @item target ddb @var{port}
17735 @kindex target ddb @var{port}
17736 NEC's DDB variant of PMON for Vr4300.
17738 @item target lsi @var{port}
17739 @kindex target lsi @var{port}
17740 LSI variant of PMON.
17742 @kindex target r3900
17743 @item target r3900 @var{dev}
17744 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
17746 @kindex target array
17747 @item target array @var{dev}
17748 Array Tech LSI33K RAID controller board.
17754 @value{GDBN} also supports these special commands for MIPS targets:
17757 @item set mipsfpu double
17758 @itemx set mipsfpu single
17759 @itemx set mipsfpu none
17760 @itemx set mipsfpu auto
17761 @itemx show mipsfpu
17762 @kindex set mipsfpu
17763 @kindex show mipsfpu
17764 @cindex MIPS remote floating point
17765 @cindex floating point, MIPS remote
17766 If your target board does not support the MIPS floating point
17767 coprocessor, you should use the command @samp{set mipsfpu none} (if you
17768 need this, you may wish to put the command in your @value{GDBN} init
17769 file). This tells @value{GDBN} how to find the return value of
17770 functions which return floating point values. It also allows
17771 @value{GDBN} to avoid saving the floating point registers when calling
17772 functions on the board. If you are using a floating point coprocessor
17773 with only single precision floating point support, as on the @sc{r4650}
17774 processor, use the command @samp{set mipsfpu single}. The default
17775 double precision floating point coprocessor may be selected using
17776 @samp{set mipsfpu double}.
17778 In previous versions the only choices were double precision or no
17779 floating point, so @samp{set mipsfpu on} will select double precision
17780 and @samp{set mipsfpu off} will select no floating point.
17782 As usual, you can inquire about the @code{mipsfpu} variable with
17783 @samp{show mipsfpu}.
17785 @item set timeout @var{seconds}
17786 @itemx set retransmit-timeout @var{seconds}
17787 @itemx show timeout
17788 @itemx show retransmit-timeout
17789 @cindex @code{timeout}, MIPS protocol
17790 @cindex @code{retransmit-timeout}, MIPS protocol
17791 @kindex set timeout
17792 @kindex show timeout
17793 @kindex set retransmit-timeout
17794 @kindex show retransmit-timeout
17795 You can control the timeout used while waiting for a packet, in the MIPS
17796 remote protocol, with the @code{set timeout @var{seconds}} command. The
17797 default is 5 seconds. Similarly, you can control the timeout used while
17798 waiting for an acknowledgment of a packet with the @code{set
17799 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
17800 You can inspect both values with @code{show timeout} and @code{show
17801 retransmit-timeout}. (These commands are @emph{only} available when
17802 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
17804 The timeout set by @code{set timeout} does not apply when @value{GDBN}
17805 is waiting for your program to stop. In that case, @value{GDBN} waits
17806 forever because it has no way of knowing how long the program is going
17807 to run before stopping.
17809 @item set syn-garbage-limit @var{num}
17810 @kindex set syn-garbage-limit@r{, MIPS remote}
17811 @cindex synchronize with remote MIPS target
17812 Limit the maximum number of characters @value{GDBN} should ignore when
17813 it tries to synchronize with the remote target. The default is 10
17814 characters. Setting the limit to -1 means there's no limit.
17816 @item show syn-garbage-limit
17817 @kindex show syn-garbage-limit@r{, MIPS remote}
17818 Show the current limit on the number of characters to ignore when
17819 trying to synchronize with the remote system.
17821 @item set monitor-prompt @var{prompt}
17822 @kindex set monitor-prompt@r{, MIPS remote}
17823 @cindex remote monitor prompt
17824 Tell @value{GDBN} to expect the specified @var{prompt} string from the
17825 remote monitor. The default depends on the target:
17835 @item show monitor-prompt
17836 @kindex show monitor-prompt@r{, MIPS remote}
17837 Show the current strings @value{GDBN} expects as the prompt from the
17840 @item set monitor-warnings
17841 @kindex set monitor-warnings@r{, MIPS remote}
17842 Enable or disable monitor warnings about hardware breakpoints. This
17843 has effect only for the @code{lsi} target. When on, @value{GDBN} will
17844 display warning messages whose codes are returned by the @code{lsi}
17845 PMON monitor for breakpoint commands.
17847 @item show monitor-warnings
17848 @kindex show monitor-warnings@r{, MIPS remote}
17849 Show the current setting of printing monitor warnings.
17851 @item pmon @var{command}
17852 @kindex pmon@r{, MIPS remote}
17853 @cindex send PMON command
17854 This command allows sending an arbitrary @var{command} string to the
17855 monitor. The monitor must be in debug mode for this to work.
17858 @node OpenRISC 1000
17859 @subsection OpenRISC 1000
17860 @cindex OpenRISC 1000
17862 @cindex or1k boards
17863 See OR1k Architecture document (@uref{www.opencores.org}) for more information
17864 about platform and commands.
17868 @kindex target jtag
17869 @item target jtag jtag://@var{host}:@var{port}
17871 Connects to remote JTAG server.
17872 JTAG remote server can be either an or1ksim or JTAG server,
17873 connected via parallel port to the board.
17875 Example: @code{target jtag jtag://localhost:9999}
17878 @item or1ksim @var{command}
17879 If connected to @code{or1ksim} OpenRISC 1000 Architectural
17880 Simulator, proprietary commands can be executed.
17882 @kindex info or1k spr
17883 @item info or1k spr
17884 Displays spr groups.
17886 @item info or1k spr @var{group}
17887 @itemx info or1k spr @var{groupno}
17888 Displays register names in selected group.
17890 @item info or1k spr @var{group} @var{register}
17891 @itemx info or1k spr @var{register}
17892 @itemx info or1k spr @var{groupno} @var{registerno}
17893 @itemx info or1k spr @var{registerno}
17894 Shows information about specified spr register.
17897 @item spr @var{group} @var{register} @var{value}
17898 @itemx spr @var{register @var{value}}
17899 @itemx spr @var{groupno} @var{registerno @var{value}}
17900 @itemx spr @var{registerno @var{value}}
17901 Writes @var{value} to specified spr register.
17904 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
17905 It is very similar to @value{GDBN} trace, except it does not interfere with normal
17906 program execution and is thus much faster. Hardware breakpoints/watchpoint
17907 triggers can be set using:
17910 Load effective address/data
17912 Store effective address/data
17914 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
17919 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
17920 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
17922 @code{htrace} commands:
17923 @cindex OpenRISC 1000 htrace
17926 @item hwatch @var{conditional}
17927 Set hardware watchpoint on combination of Load/Store Effective Address(es)
17928 or Data. For example:
17930 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17932 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17936 Display information about current HW trace configuration.
17938 @item htrace trigger @var{conditional}
17939 Set starting criteria for HW trace.
17941 @item htrace qualifier @var{conditional}
17942 Set acquisition qualifier for HW trace.
17944 @item htrace stop @var{conditional}
17945 Set HW trace stopping criteria.
17947 @item htrace record [@var{data}]*
17948 Selects the data to be recorded, when qualifier is met and HW trace was
17951 @item htrace enable
17952 @itemx htrace disable
17953 Enables/disables the HW trace.
17955 @item htrace rewind [@var{filename}]
17956 Clears currently recorded trace data.
17958 If filename is specified, new trace file is made and any newly collected data
17959 will be written there.
17961 @item htrace print [@var{start} [@var{len}]]
17962 Prints trace buffer, using current record configuration.
17964 @item htrace mode continuous
17965 Set continuous trace mode.
17967 @item htrace mode suspend
17968 Set suspend trace mode.
17972 @node PowerPC Embedded
17973 @subsection PowerPC Embedded
17975 @value{GDBN} provides the following PowerPC-specific commands:
17978 @kindex set powerpc
17979 @item set powerpc soft-float
17980 @itemx show powerpc soft-float
17981 Force @value{GDBN} to use (or not use) a software floating point calling
17982 convention. By default, @value{GDBN} selects the calling convention based
17983 on the selected architecture and the provided executable file.
17985 @item set powerpc vector-abi
17986 @itemx show powerpc vector-abi
17987 Force @value{GDBN} to use the specified calling convention for vector
17988 arguments and return values. The valid options are @samp{auto};
17989 @samp{generic}, to avoid vector registers even if they are present;
17990 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
17991 registers. By default, @value{GDBN} selects the calling convention
17992 based on the selected architecture and the provided executable file.
17994 @kindex target dink32
17995 @item target dink32 @var{dev}
17996 DINK32 ROM monitor.
17998 @kindex target ppcbug
17999 @item target ppcbug @var{dev}
18000 @kindex target ppcbug1
18001 @item target ppcbug1 @var{dev}
18002 PPCBUG ROM monitor for PowerPC.
18005 @item target sds @var{dev}
18006 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18009 @cindex SDS protocol
18010 The following commands specific to the SDS protocol are supported
18014 @item set sdstimeout @var{nsec}
18015 @kindex set sdstimeout
18016 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18017 default is 2 seconds.
18019 @item show sdstimeout
18020 @kindex show sdstimeout
18021 Show the current value of the SDS timeout.
18023 @item sds @var{command}
18024 @kindex sds@r{, a command}
18025 Send the specified @var{command} string to the SDS monitor.
18030 @subsection HP PA Embedded
18034 @kindex target op50n
18035 @item target op50n @var{dev}
18036 OP50N monitor, running on an OKI HPPA board.
18038 @kindex target w89k
18039 @item target w89k @var{dev}
18040 W89K monitor, running on a Winbond HPPA board.
18045 @subsection Tsqware Sparclet
18049 @value{GDBN} enables developers to debug tasks running on
18050 Sparclet targets from a Unix host.
18051 @value{GDBN} uses code that runs on
18052 both the Unix host and on the Sparclet target. The program
18053 @code{@value{GDBP}} is installed and executed on the Unix host.
18056 @item remotetimeout @var{args}
18057 @kindex remotetimeout
18058 @value{GDBN} supports the option @code{remotetimeout}.
18059 This option is set by the user, and @var{args} represents the number of
18060 seconds @value{GDBN} waits for responses.
18063 @cindex compiling, on Sparclet
18064 When compiling for debugging, include the options @samp{-g} to get debug
18065 information and @samp{-Ttext} to relocate the program to where you wish to
18066 load it on the target. You may also want to add the options @samp{-n} or
18067 @samp{-N} in order to reduce the size of the sections. Example:
18070 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18073 You can use @code{objdump} to verify that the addresses are what you intended:
18076 sparclet-aout-objdump --headers --syms prog
18079 @cindex running, on Sparclet
18081 your Unix execution search path to find @value{GDBN}, you are ready to
18082 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18083 (or @code{sparclet-aout-gdb}, depending on your installation).
18085 @value{GDBN} comes up showing the prompt:
18092 * Sparclet File:: Setting the file to debug
18093 * Sparclet Connection:: Connecting to Sparclet
18094 * Sparclet Download:: Sparclet download
18095 * Sparclet Execution:: Running and debugging
18098 @node Sparclet File
18099 @subsubsection Setting File to Debug
18101 The @value{GDBN} command @code{file} lets you choose with program to debug.
18104 (gdbslet) file prog
18108 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18109 @value{GDBN} locates
18110 the file by searching the directories listed in the command search
18112 If the file was compiled with debug information (option @samp{-g}), source
18113 files will be searched as well.
18114 @value{GDBN} locates
18115 the source files by searching the directories listed in the directory search
18116 path (@pxref{Environment, ,Your Program's Environment}).
18118 to find a file, it displays a message such as:
18121 prog: No such file or directory.
18124 When this happens, add the appropriate directories to the search paths with
18125 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18126 @code{target} command again.
18128 @node Sparclet Connection
18129 @subsubsection Connecting to Sparclet
18131 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18132 To connect to a target on serial port ``@code{ttya}'', type:
18135 (gdbslet) target sparclet /dev/ttya
18136 Remote target sparclet connected to /dev/ttya
18137 main () at ../prog.c:3
18141 @value{GDBN} displays messages like these:
18147 @node Sparclet Download
18148 @subsubsection Sparclet Download
18150 @cindex download to Sparclet
18151 Once connected to the Sparclet target,
18152 you can use the @value{GDBN}
18153 @code{load} command to download the file from the host to the target.
18154 The file name and load offset should be given as arguments to the @code{load}
18156 Since the file format is aout, the program must be loaded to the starting
18157 address. You can use @code{objdump} to find out what this value is. The load
18158 offset is an offset which is added to the VMA (virtual memory address)
18159 of each of the file's sections.
18160 For instance, if the program
18161 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18162 and bss at 0x12010170, in @value{GDBN}, type:
18165 (gdbslet) load prog 0x12010000
18166 Loading section .text, size 0xdb0 vma 0x12010000
18169 If the code is loaded at a different address then what the program was linked
18170 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18171 to tell @value{GDBN} where to map the symbol table.
18173 @node Sparclet Execution
18174 @subsubsection Running and Debugging
18176 @cindex running and debugging Sparclet programs
18177 You can now begin debugging the task using @value{GDBN}'s execution control
18178 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18179 manual for the list of commands.
18183 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18185 Starting program: prog
18186 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18187 3 char *symarg = 0;
18189 4 char *execarg = "hello!";
18194 @subsection Fujitsu Sparclite
18198 @kindex target sparclite
18199 @item target sparclite @var{dev}
18200 Fujitsu sparclite boards, used only for the purpose of loading.
18201 You must use an additional command to debug the program.
18202 For example: target remote @var{dev} using @value{GDBN} standard
18208 @subsection Zilog Z8000
18211 @cindex simulator, Z8000
18212 @cindex Zilog Z8000 simulator
18214 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
18217 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
18218 unsegmented variant of the Z8000 architecture) or the Z8001 (the
18219 segmented variant). The simulator recognizes which architecture is
18220 appropriate by inspecting the object code.
18223 @item target sim @var{args}
18225 @kindex target sim@r{, with Z8000}
18226 Debug programs on a simulated CPU. If the simulator supports setup
18227 options, specify them via @var{args}.
18231 After specifying this target, you can debug programs for the simulated
18232 CPU in the same style as programs for your host computer; use the
18233 @code{file} command to load a new program image, the @code{run} command
18234 to run your program, and so on.
18236 As well as making available all the usual machine registers
18237 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18238 additional items of information as specially named registers:
18243 Counts clock-ticks in the simulator.
18246 Counts instructions run in the simulator.
18249 Execution time in 60ths of a second.
18253 You can refer to these values in @value{GDBN} expressions with the usual
18254 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18255 conditional breakpoint that suspends only after at least 5000
18256 simulated clock ticks.
18259 @subsection Atmel AVR
18262 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18263 following AVR-specific commands:
18266 @item info io_registers
18267 @kindex info io_registers@r{, AVR}
18268 @cindex I/O registers (Atmel AVR)
18269 This command displays information about the AVR I/O registers. For
18270 each register, @value{GDBN} prints its number and value.
18277 When configured for debugging CRIS, @value{GDBN} provides the
18278 following CRIS-specific commands:
18281 @item set cris-version @var{ver}
18282 @cindex CRIS version
18283 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
18284 The CRIS version affects register names and sizes. This command is useful in
18285 case autodetection of the CRIS version fails.
18287 @item show cris-version
18288 Show the current CRIS version.
18290 @item set cris-dwarf2-cfi
18291 @cindex DWARF-2 CFI and CRIS
18292 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
18293 Change to @samp{off} when using @code{gcc-cris} whose version is below
18296 @item show cris-dwarf2-cfi
18297 Show the current state of using DWARF-2 CFI.
18299 @item set cris-mode @var{mode}
18301 Set the current CRIS mode to @var{mode}. It should only be changed when
18302 debugging in guru mode, in which case it should be set to
18303 @samp{guru} (the default is @samp{normal}).
18305 @item show cris-mode
18306 Show the current CRIS mode.
18310 @subsection Renesas Super-H
18313 For the Renesas Super-H processor, @value{GDBN} provides these
18318 @kindex regs@r{, Super-H}
18319 Show the values of all Super-H registers.
18321 @item set sh calling-convention @var{convention}
18322 @kindex set sh calling-convention
18323 Set the calling-convention used when calling functions from @value{GDBN}.
18324 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
18325 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
18326 convention. If the DWARF-2 information of the called function specifies
18327 that the function follows the Renesas calling convention, the function
18328 is called using the Renesas calling convention. If the calling convention
18329 is set to @samp{renesas}, the Renesas calling convention is always used,
18330 regardless of the DWARF-2 information. This can be used to override the
18331 default of @samp{gcc} if debug information is missing, or the compiler
18332 does not emit the DWARF-2 calling convention entry for a function.
18334 @item show sh calling-convention
18335 @kindex show sh calling-convention
18336 Show the current calling convention setting.
18341 @node Architectures
18342 @section Architectures
18344 This section describes characteristics of architectures that affect
18345 all uses of @value{GDBN} with the architecture, both native and cross.
18352 * HPPA:: HP PA architecture
18353 * SPU:: Cell Broadband Engine SPU architecture
18358 @subsection x86 Architecture-specific Issues
18361 @item set struct-convention @var{mode}
18362 @kindex set struct-convention
18363 @cindex struct return convention
18364 @cindex struct/union returned in registers
18365 Set the convention used by the inferior to return @code{struct}s and
18366 @code{union}s from functions to @var{mode}. Possible values of
18367 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
18368 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
18369 are returned on the stack, while @code{"reg"} means that a
18370 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
18371 be returned in a register.
18373 @item show struct-convention
18374 @kindex show struct-convention
18375 Show the current setting of the convention to return @code{struct}s
18384 @kindex set rstack_high_address
18385 @cindex AMD 29K register stack
18386 @cindex register stack, AMD29K
18387 @item set rstack_high_address @var{address}
18388 On AMD 29000 family processors, registers are saved in a separate
18389 @dfn{register stack}. There is no way for @value{GDBN} to determine the
18390 extent of this stack. Normally, @value{GDBN} just assumes that the
18391 stack is ``large enough''. This may result in @value{GDBN} referencing
18392 memory locations that do not exist. If necessary, you can get around
18393 this problem by specifying the ending address of the register stack with
18394 the @code{set rstack_high_address} command. The argument should be an
18395 address, which you probably want to precede with @samp{0x} to specify in
18398 @kindex show rstack_high_address
18399 @item show rstack_high_address
18400 Display the current limit of the register stack, on AMD 29000 family
18408 See the following section.
18413 @cindex stack on Alpha
18414 @cindex stack on MIPS
18415 @cindex Alpha stack
18417 Alpha- and MIPS-based computers use an unusual stack frame, which
18418 sometimes requires @value{GDBN} to search backward in the object code to
18419 find the beginning of a function.
18421 @cindex response time, MIPS debugging
18422 To improve response time (especially for embedded applications, where
18423 @value{GDBN} may be restricted to a slow serial line for this search)
18424 you may want to limit the size of this search, using one of these
18428 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
18429 @item set heuristic-fence-post @var{limit}
18430 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
18431 search for the beginning of a function. A value of @var{0} (the
18432 default) means there is no limit. However, except for @var{0}, the
18433 larger the limit the more bytes @code{heuristic-fence-post} must search
18434 and therefore the longer it takes to run. You should only need to use
18435 this command when debugging a stripped executable.
18437 @item show heuristic-fence-post
18438 Display the current limit.
18442 These commands are available @emph{only} when @value{GDBN} is configured
18443 for debugging programs on Alpha or MIPS processors.
18445 Several MIPS-specific commands are available when debugging MIPS
18449 @item set mips abi @var{arg}
18450 @kindex set mips abi
18451 @cindex set ABI for MIPS
18452 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
18453 values of @var{arg} are:
18457 The default ABI associated with the current binary (this is the
18468 @item show mips abi
18469 @kindex show mips abi
18470 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
18473 @itemx show mipsfpu
18474 @xref{MIPS Embedded, set mipsfpu}.
18476 @item set mips mask-address @var{arg}
18477 @kindex set mips mask-address
18478 @cindex MIPS addresses, masking
18479 This command determines whether the most-significant 32 bits of 64-bit
18480 MIPS addresses are masked off. The argument @var{arg} can be
18481 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
18482 setting, which lets @value{GDBN} determine the correct value.
18484 @item show mips mask-address
18485 @kindex show mips mask-address
18486 Show whether the upper 32 bits of MIPS addresses are masked off or
18489 @item set remote-mips64-transfers-32bit-regs
18490 @kindex set remote-mips64-transfers-32bit-regs
18491 This command controls compatibility with 64-bit MIPS targets that
18492 transfer data in 32-bit quantities. If you have an old MIPS 64 target
18493 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
18494 and 64 bits for other registers, set this option to @samp{on}.
18496 @item show remote-mips64-transfers-32bit-regs
18497 @kindex show remote-mips64-transfers-32bit-regs
18498 Show the current setting of compatibility with older MIPS 64 targets.
18500 @item set debug mips
18501 @kindex set debug mips
18502 This command turns on and off debugging messages for the MIPS-specific
18503 target code in @value{GDBN}.
18505 @item show debug mips
18506 @kindex show debug mips
18507 Show the current setting of MIPS debugging messages.
18513 @cindex HPPA support
18515 When @value{GDBN} is debugging the HP PA architecture, it provides the
18516 following special commands:
18519 @item set debug hppa
18520 @kindex set debug hppa
18521 This command determines whether HPPA architecture-specific debugging
18522 messages are to be displayed.
18524 @item show debug hppa
18525 Show whether HPPA debugging messages are displayed.
18527 @item maint print unwind @var{address}
18528 @kindex maint print unwind@r{, HPPA}
18529 This command displays the contents of the unwind table entry at the
18530 given @var{address}.
18536 @subsection Cell Broadband Engine SPU architecture
18537 @cindex Cell Broadband Engine
18540 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
18541 it provides the following special commands:
18544 @item info spu event
18546 Display SPU event facility status. Shows current event mask
18547 and pending event status.
18549 @item info spu signal
18550 Display SPU signal notification facility status. Shows pending
18551 signal-control word and signal notification mode of both signal
18552 notification channels.
18554 @item info spu mailbox
18555 Display SPU mailbox facility status. Shows all pending entries,
18556 in order of processing, in each of the SPU Write Outbound,
18557 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
18560 Display MFC DMA status. Shows all pending commands in the MFC
18561 DMA queue. For each entry, opcode, tag, class IDs, effective
18562 and local store addresses and transfer size are shown.
18564 @item info spu proxydma
18565 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
18566 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
18567 and local store addresses and transfer size are shown.
18571 When @value{GDBN} is debugging a combined PowerPC/SPU application
18572 on the Cell Broadband Engine, it provides in addition the following
18576 @item set spu stop-on-load @var{arg}
18578 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
18579 will give control to the user when a new SPE thread enters its @code{main}
18580 function. The default is @code{off}.
18582 @item show spu stop-on-load
18584 Show whether to stop for new SPE threads.
18586 @item set spu auto-flush-cache @var{arg}
18587 Set whether to automatically flush the software-managed cache. When set to
18588 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
18589 cache to be flushed whenever SPE execution stops. This provides a consistent
18590 view of PowerPC memory that is accessed via the cache. If an application
18591 does not use the software-managed cache, this option has no effect.
18593 @item show spu auto-flush-cache
18594 Show whether to automatically flush the software-managed cache.
18599 @subsection PowerPC
18600 @cindex PowerPC architecture
18602 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
18603 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
18604 numbers stored in the floating point registers. These values must be stored
18605 in two consecutive registers, always starting at an even register like
18606 @code{f0} or @code{f2}.
18608 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
18609 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
18610 @code{f2} and @code{f3} for @code{$dl1} and so on.
18612 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
18613 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
18616 @node Controlling GDB
18617 @chapter Controlling @value{GDBN}
18619 You can alter the way @value{GDBN} interacts with you by using the
18620 @code{set} command. For commands controlling how @value{GDBN} displays
18621 data, see @ref{Print Settings, ,Print Settings}. Other settings are
18626 * Editing:: Command editing
18627 * Command History:: Command history
18628 * Screen Size:: Screen size
18629 * Numbers:: Numbers
18630 * ABI:: Configuring the current ABI
18631 * Messages/Warnings:: Optional warnings and messages
18632 * Debugging Output:: Optional messages about internal happenings
18633 * Other Misc Settings:: Other Miscellaneous Settings
18641 @value{GDBN} indicates its readiness to read a command by printing a string
18642 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
18643 can change the prompt string with the @code{set prompt} command. For
18644 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
18645 the prompt in one of the @value{GDBN} sessions so that you can always tell
18646 which one you are talking to.
18648 @emph{Note:} @code{set prompt} does not add a space for you after the
18649 prompt you set. This allows you to set a prompt which ends in a space
18650 or a prompt that does not.
18654 @item set prompt @var{newprompt}
18655 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
18657 @kindex show prompt
18659 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
18663 @section Command Editing
18665 @cindex command line editing
18667 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
18668 @sc{gnu} library provides consistent behavior for programs which provide a
18669 command line interface to the user. Advantages are @sc{gnu} Emacs-style
18670 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
18671 substitution, and a storage and recall of command history across
18672 debugging sessions.
18674 You may control the behavior of command line editing in @value{GDBN} with the
18675 command @code{set}.
18678 @kindex set editing
18681 @itemx set editing on
18682 Enable command line editing (enabled by default).
18684 @item set editing off
18685 Disable command line editing.
18687 @kindex show editing
18689 Show whether command line editing is enabled.
18692 @xref{Command Line Editing}, for more details about the Readline
18693 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
18694 encouraged to read that chapter.
18696 @node Command History
18697 @section Command History
18698 @cindex command history
18700 @value{GDBN} can keep track of the commands you type during your
18701 debugging sessions, so that you can be certain of precisely what
18702 happened. Use these commands to manage the @value{GDBN} command
18705 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
18706 package, to provide the history facility. @xref{Using History
18707 Interactively}, for the detailed description of the History library.
18709 To issue a command to @value{GDBN} without affecting certain aspects of
18710 the state which is seen by users, prefix it with @samp{server }
18711 (@pxref{Server Prefix}). This
18712 means that this command will not affect the command history, nor will it
18713 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18714 pressed on a line by itself.
18716 @cindex @code{server}, command prefix
18717 The server prefix does not affect the recording of values into the value
18718 history; to print a value without recording it into the value history,
18719 use the @code{output} command instead of the @code{print} command.
18721 Here is the description of @value{GDBN} commands related to command
18725 @cindex history substitution
18726 @cindex history file
18727 @kindex set history filename
18728 @cindex @env{GDBHISTFILE}, environment variable
18729 @item set history filename @var{fname}
18730 Set the name of the @value{GDBN} command history file to @var{fname}.
18731 This is the file where @value{GDBN} reads an initial command history
18732 list, and where it writes the command history from this session when it
18733 exits. You can access this list through history expansion or through
18734 the history command editing characters listed below. This file defaults
18735 to the value of the environment variable @code{GDBHISTFILE}, or to
18736 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
18739 @cindex save command history
18740 @kindex set history save
18741 @item set history save
18742 @itemx set history save on
18743 Record command history in a file, whose name may be specified with the
18744 @code{set history filename} command. By default, this option is disabled.
18746 @item set history save off
18747 Stop recording command history in a file.
18749 @cindex history size
18750 @kindex set history size
18751 @cindex @env{HISTSIZE}, environment variable
18752 @item set history size @var{size}
18753 Set the number of commands which @value{GDBN} keeps in its history list.
18754 This defaults to the value of the environment variable
18755 @code{HISTSIZE}, or to 256 if this variable is not set.
18758 History expansion assigns special meaning to the character @kbd{!}.
18759 @xref{Event Designators}, for more details.
18761 @cindex history expansion, turn on/off
18762 Since @kbd{!} is also the logical not operator in C, history expansion
18763 is off by default. If you decide to enable history expansion with the
18764 @code{set history expansion on} command, you may sometimes need to
18765 follow @kbd{!} (when it is used as logical not, in an expression) with
18766 a space or a tab to prevent it from being expanded. The readline
18767 history facilities do not attempt substitution on the strings
18768 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
18770 The commands to control history expansion are:
18773 @item set history expansion on
18774 @itemx set history expansion
18775 @kindex set history expansion
18776 Enable history expansion. History expansion is off by default.
18778 @item set history expansion off
18779 Disable history expansion.
18782 @kindex show history
18784 @itemx show history filename
18785 @itemx show history save
18786 @itemx show history size
18787 @itemx show history expansion
18788 These commands display the state of the @value{GDBN} history parameters.
18789 @code{show history} by itself displays all four states.
18794 @kindex show commands
18795 @cindex show last commands
18796 @cindex display command history
18797 @item show commands
18798 Display the last ten commands in the command history.
18800 @item show commands @var{n}
18801 Print ten commands centered on command number @var{n}.
18803 @item show commands +
18804 Print ten commands just after the commands last printed.
18808 @section Screen Size
18809 @cindex size of screen
18810 @cindex pauses in output
18812 Certain commands to @value{GDBN} may produce large amounts of
18813 information output to the screen. To help you read all of it,
18814 @value{GDBN} pauses and asks you for input at the end of each page of
18815 output. Type @key{RET} when you want to continue the output, or @kbd{q}
18816 to discard the remaining output. Also, the screen width setting
18817 determines when to wrap lines of output. Depending on what is being
18818 printed, @value{GDBN} tries to break the line at a readable place,
18819 rather than simply letting it overflow onto the following line.
18821 Normally @value{GDBN} knows the size of the screen from the terminal
18822 driver software. For example, on Unix @value{GDBN} uses the termcap data base
18823 together with the value of the @code{TERM} environment variable and the
18824 @code{stty rows} and @code{stty cols} settings. If this is not correct,
18825 you can override it with the @code{set height} and @code{set
18832 @kindex show height
18833 @item set height @var{lpp}
18835 @itemx set width @var{cpl}
18837 These @code{set} commands specify a screen height of @var{lpp} lines and
18838 a screen width of @var{cpl} characters. The associated @code{show}
18839 commands display the current settings.
18841 If you specify a height of zero lines, @value{GDBN} does not pause during
18842 output no matter how long the output is. This is useful if output is to a
18843 file or to an editor buffer.
18845 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
18846 from wrapping its output.
18848 @item set pagination on
18849 @itemx set pagination off
18850 @kindex set pagination
18851 Turn the output pagination on or off; the default is on. Turning
18852 pagination off is the alternative to @code{set height 0}. Note that
18853 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
18854 Options, -batch}) also automatically disables pagination.
18856 @item show pagination
18857 @kindex show pagination
18858 Show the current pagination mode.
18863 @cindex number representation
18864 @cindex entering numbers
18866 You can always enter numbers in octal, decimal, or hexadecimal in
18867 @value{GDBN} by the usual conventions: octal numbers begin with
18868 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
18869 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
18870 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
18871 10; likewise, the default display for numbers---when no particular
18872 format is specified---is base 10. You can change the default base for
18873 both input and output with the commands described below.
18876 @kindex set input-radix
18877 @item set input-radix @var{base}
18878 Set the default base for numeric input. Supported choices
18879 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18880 specified either unambiguously or using the current input radix; for
18884 set input-radix 012
18885 set input-radix 10.
18886 set input-radix 0xa
18890 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
18891 leaves the input radix unchanged, no matter what it was, since
18892 @samp{10}, being without any leading or trailing signs of its base, is
18893 interpreted in the current radix. Thus, if the current radix is 16,
18894 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
18897 @kindex set output-radix
18898 @item set output-radix @var{base}
18899 Set the default base for numeric display. Supported choices
18900 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18901 specified either unambiguously or using the current input radix.
18903 @kindex show input-radix
18904 @item show input-radix
18905 Display the current default base for numeric input.
18907 @kindex show output-radix
18908 @item show output-radix
18909 Display the current default base for numeric display.
18911 @item set radix @r{[}@var{base}@r{]}
18915 These commands set and show the default base for both input and output
18916 of numbers. @code{set radix} sets the radix of input and output to
18917 the same base; without an argument, it resets the radix back to its
18918 default value of 10.
18923 @section Configuring the Current ABI
18925 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
18926 application automatically. However, sometimes you need to override its
18927 conclusions. Use these commands to manage @value{GDBN}'s view of the
18934 One @value{GDBN} configuration can debug binaries for multiple operating
18935 system targets, either via remote debugging or native emulation.
18936 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
18937 but you can override its conclusion using the @code{set osabi} command.
18938 One example where this is useful is in debugging of binaries which use
18939 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
18940 not have the same identifying marks that the standard C library for your
18945 Show the OS ABI currently in use.
18948 With no argument, show the list of registered available OS ABI's.
18950 @item set osabi @var{abi}
18951 Set the current OS ABI to @var{abi}.
18954 @cindex float promotion
18956 Generally, the way that an argument of type @code{float} is passed to a
18957 function depends on whether the function is prototyped. For a prototyped
18958 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
18959 according to the architecture's convention for @code{float}. For unprototyped
18960 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
18961 @code{double} and then passed.
18963 Unfortunately, some forms of debug information do not reliably indicate whether
18964 a function is prototyped. If @value{GDBN} calls a function that is not marked
18965 as prototyped, it consults @kbd{set coerce-float-to-double}.
18968 @kindex set coerce-float-to-double
18969 @item set coerce-float-to-double
18970 @itemx set coerce-float-to-double on
18971 Arguments of type @code{float} will be promoted to @code{double} when passed
18972 to an unprototyped function. This is the default setting.
18974 @item set coerce-float-to-double off
18975 Arguments of type @code{float} will be passed directly to unprototyped
18978 @kindex show coerce-float-to-double
18979 @item show coerce-float-to-double
18980 Show the current setting of promoting @code{float} to @code{double}.
18984 @kindex show cp-abi
18985 @value{GDBN} needs to know the ABI used for your program's C@t{++}
18986 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
18987 used to build your application. @value{GDBN} only fully supports
18988 programs with a single C@t{++} ABI; if your program contains code using
18989 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
18990 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
18991 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
18992 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
18993 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
18994 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
18999 Show the C@t{++} ABI currently in use.
19002 With no argument, show the list of supported C@t{++} ABI's.
19004 @item set cp-abi @var{abi}
19005 @itemx set cp-abi auto
19006 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19009 @node Messages/Warnings
19010 @section Optional Warnings and Messages
19012 @cindex verbose operation
19013 @cindex optional warnings
19014 By default, @value{GDBN} is silent about its inner workings. If you are
19015 running on a slow machine, you may want to use the @code{set verbose}
19016 command. This makes @value{GDBN} tell you when it does a lengthy
19017 internal operation, so you will not think it has crashed.
19019 Currently, the messages controlled by @code{set verbose} are those
19020 which announce that the symbol table for a source file is being read;
19021 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19024 @kindex set verbose
19025 @item set verbose on
19026 Enables @value{GDBN} output of certain informational messages.
19028 @item set verbose off
19029 Disables @value{GDBN} output of certain informational messages.
19031 @kindex show verbose
19033 Displays whether @code{set verbose} is on or off.
19036 By default, if @value{GDBN} encounters bugs in the symbol table of an
19037 object file, it is silent; but if you are debugging a compiler, you may
19038 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19043 @kindex set complaints
19044 @item set complaints @var{limit}
19045 Permits @value{GDBN} to output @var{limit} complaints about each type of
19046 unusual symbols before becoming silent about the problem. Set
19047 @var{limit} to zero to suppress all complaints; set it to a large number
19048 to prevent complaints from being suppressed.
19050 @kindex show complaints
19051 @item show complaints
19052 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19056 @anchor{confirmation requests}
19057 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19058 lot of stupid questions to confirm certain commands. For example, if
19059 you try to run a program which is already running:
19063 The program being debugged has been started already.
19064 Start it from the beginning? (y or n)
19067 If you are willing to unflinchingly face the consequences of your own
19068 commands, you can disable this ``feature'':
19072 @kindex set confirm
19074 @cindex confirmation
19075 @cindex stupid questions
19076 @item set confirm off
19077 Disables confirmation requests. Note that running @value{GDBN} with
19078 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19079 automatically disables confirmation requests.
19081 @item set confirm on
19082 Enables confirmation requests (the default).
19084 @kindex show confirm
19086 Displays state of confirmation requests.
19090 @cindex command tracing
19091 If you need to debug user-defined commands or sourced files you may find it
19092 useful to enable @dfn{command tracing}. In this mode each command will be
19093 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19094 quantity denoting the call depth of each command.
19097 @kindex set trace-commands
19098 @cindex command scripts, debugging
19099 @item set trace-commands on
19100 Enable command tracing.
19101 @item set trace-commands off
19102 Disable command tracing.
19103 @item show trace-commands
19104 Display the current state of command tracing.
19107 @node Debugging Output
19108 @section Optional Messages about Internal Happenings
19109 @cindex optional debugging messages
19111 @value{GDBN} has commands that enable optional debugging messages from
19112 various @value{GDBN} subsystems; normally these commands are of
19113 interest to @value{GDBN} maintainers, or when reporting a bug. This
19114 section documents those commands.
19117 @kindex set exec-done-display
19118 @item set exec-done-display
19119 Turns on or off the notification of asynchronous commands'
19120 completion. When on, @value{GDBN} will print a message when an
19121 asynchronous command finishes its execution. The default is off.
19122 @kindex show exec-done-display
19123 @item show exec-done-display
19124 Displays the current setting of asynchronous command completion
19127 @cindex gdbarch debugging info
19128 @cindex architecture debugging info
19129 @item set debug arch
19130 Turns on or off display of gdbarch debugging info. The default is off
19132 @item show debug arch
19133 Displays the current state of displaying gdbarch debugging info.
19134 @item set debug aix-thread
19135 @cindex AIX threads
19136 Display debugging messages about inner workings of the AIX thread
19138 @item show debug aix-thread
19139 Show the current state of AIX thread debugging info display.
19140 @item set debug dwarf2-die
19141 @cindex DWARF2 DIEs
19142 Dump DWARF2 DIEs after they are read in.
19143 The value is the number of nesting levels to print.
19144 A value of zero turns off the display.
19145 @item show debug dwarf2-die
19146 Show the current state of DWARF2 DIE debugging.
19147 @item set debug displaced
19148 @cindex displaced stepping debugging info
19149 Turns on or off display of @value{GDBN} debugging info for the
19150 displaced stepping support. The default is off.
19151 @item show debug displaced
19152 Displays the current state of displaying @value{GDBN} debugging info
19153 related to displaced stepping.
19154 @item set debug event
19155 @cindex event debugging info
19156 Turns on or off display of @value{GDBN} event debugging info. The
19158 @item show debug event
19159 Displays the current state of displaying @value{GDBN} event debugging
19161 @item set debug expression
19162 @cindex expression debugging info
19163 Turns on or off display of debugging info about @value{GDBN}
19164 expression parsing. The default is off.
19165 @item show debug expression
19166 Displays the current state of displaying debugging info about
19167 @value{GDBN} expression parsing.
19168 @item set debug frame
19169 @cindex frame debugging info
19170 Turns on or off display of @value{GDBN} frame debugging info. The
19172 @item show debug frame
19173 Displays the current state of displaying @value{GDBN} frame debugging
19175 @item set debug gnu-nat
19176 @cindex @sc{gnu}/Hurd debug messages
19177 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19178 @item show debug gnu-nat
19179 Show the current state of @sc{gnu}/Hurd debugging messages.
19180 @item set debug infrun
19181 @cindex inferior debugging info
19182 Turns on or off display of @value{GDBN} debugging info for running the inferior.
19183 The default is off. @file{infrun.c} contains GDB's runtime state machine used
19184 for implementing operations such as single-stepping the inferior.
19185 @item show debug infrun
19186 Displays the current state of @value{GDBN} inferior debugging.
19187 @item set debug lin-lwp
19188 @cindex @sc{gnu}/Linux LWP debug messages
19189 @cindex Linux lightweight processes
19190 Turns on or off debugging messages from the Linux LWP debug support.
19191 @item show debug lin-lwp
19192 Show the current state of Linux LWP debugging messages.
19193 @item set debug lin-lwp-async
19194 @cindex @sc{gnu}/Linux LWP async debug messages
19195 @cindex Linux lightweight processes
19196 Turns on or off debugging messages from the Linux LWP async debug support.
19197 @item show debug lin-lwp-async
19198 Show the current state of Linux LWP async debugging messages.
19199 @item set debug observer
19200 @cindex observer debugging info
19201 Turns on or off display of @value{GDBN} observer debugging. This
19202 includes info such as the notification of observable events.
19203 @item show debug observer
19204 Displays the current state of observer debugging.
19205 @item set debug overload
19206 @cindex C@t{++} overload debugging info
19207 Turns on or off display of @value{GDBN} C@t{++} overload debugging
19208 info. This includes info such as ranking of functions, etc. The default
19210 @item show debug overload
19211 Displays the current state of displaying @value{GDBN} C@t{++} overload
19213 @cindex expression parser, debugging info
19214 @cindex debug expression parser
19215 @item set debug parser
19216 Turns on or off the display of expression parser debugging output.
19217 Internally, this sets the @code{yydebug} variable in the expression
19218 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
19219 details. The default is off.
19220 @item show debug parser
19221 Show the current state of expression parser debugging.
19222 @cindex packets, reporting on stdout
19223 @cindex serial connections, debugging
19224 @cindex debug remote protocol
19225 @cindex remote protocol debugging
19226 @cindex display remote packets
19227 @item set debug remote
19228 Turns on or off display of reports on all packets sent back and forth across
19229 the serial line to the remote machine. The info is printed on the
19230 @value{GDBN} standard output stream. The default is off.
19231 @item show debug remote
19232 Displays the state of display of remote packets.
19233 @item set debug serial
19234 Turns on or off display of @value{GDBN} serial debugging info. The
19236 @item show debug serial
19237 Displays the current state of displaying @value{GDBN} serial debugging
19239 @item set debug solib-frv
19240 @cindex FR-V shared-library debugging
19241 Turns on or off debugging messages for FR-V shared-library code.
19242 @item show debug solib-frv
19243 Display the current state of FR-V shared-library code debugging
19245 @item set debug target
19246 @cindex target debugging info
19247 Turns on or off display of @value{GDBN} target debugging info. This info
19248 includes what is going on at the target level of GDB, as it happens. The
19249 default is 0. Set it to 1 to track events, and to 2 to also track the
19250 value of large memory transfers. Changes to this flag do not take effect
19251 until the next time you connect to a target or use the @code{run} command.
19252 @item show debug target
19253 Displays the current state of displaying @value{GDBN} target debugging
19255 @item set debug timestamp
19256 @cindex timestampping debugging info
19257 Turns on or off display of timestamps with @value{GDBN} debugging info.
19258 When enabled, seconds and microseconds are displayed before each debugging
19260 @item show debug timestamp
19261 Displays the current state of displaying timestamps with @value{GDBN}
19263 @item set debugvarobj
19264 @cindex variable object debugging info
19265 Turns on or off display of @value{GDBN} variable object debugging
19266 info. The default is off.
19267 @item show debugvarobj
19268 Displays the current state of displaying @value{GDBN} variable object
19270 @item set debug xml
19271 @cindex XML parser debugging
19272 Turns on or off debugging messages for built-in XML parsers.
19273 @item show debug xml
19274 Displays the current state of XML debugging messages.
19277 @node Other Misc Settings
19278 @section Other Miscellaneous Settings
19279 @cindex miscellaneous settings
19282 @kindex set interactive-mode
19283 @item set interactive-mode
19284 If @code{on}, forces @value{GDBN} to operate interactively.
19285 If @code{off}, forces @value{GDBN} to operate non-interactively,
19286 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
19287 based on whether the debugger was started in a terminal or not.
19289 In the vast majority of cases, the debugger should be able to guess
19290 correctly which mode should be used. But this setting can be useful
19291 in certain specific cases, such as running a MinGW @value{GDBN}
19292 inside a cygwin window.
19294 @kindex show interactive-mode
19295 @item show interactive-mode
19296 Displays whether the debugger is operating in interactive mode or not.
19299 @node Extending GDB
19300 @chapter Extending @value{GDBN}
19301 @cindex extending GDB
19303 @value{GDBN} provides two mechanisms for extension. The first is based
19304 on composition of @value{GDBN} commands, and the second is based on the
19305 Python scripting language.
19307 To facilitate the use of these extensions, @value{GDBN} is capable
19308 of evaluating the contents of a file. When doing so, @value{GDBN}
19309 can recognize which scripting language is being used by looking at
19310 the filename extension. Files with an unrecognized filename extension
19311 are always treated as a @value{GDBN} Command Files.
19312 @xref{Command Files,, Command files}.
19314 You can control how @value{GDBN} evaluates these files with the following
19318 @kindex set script-extension
19319 @kindex show script-extension
19320 @item set script-extension off
19321 All scripts are always evaluated as @value{GDBN} Command Files.
19323 @item set script-extension soft
19324 The debugger determines the scripting language based on filename
19325 extension. If this scripting language is supported, @value{GDBN}
19326 evaluates the script using that language. Otherwise, it evaluates
19327 the file as a @value{GDBN} Command File.
19329 @item set script-extension strict
19330 The debugger determines the scripting language based on filename
19331 extension, and evaluates the script using that language. If the
19332 language is not supported, then the evaluation fails.
19334 @item show script-extension
19335 Display the current value of the @code{script-extension} option.
19340 * Sequences:: Canned Sequences of Commands
19341 * Python:: Scripting @value{GDBN} using Python
19345 @section Canned Sequences of Commands
19347 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
19348 Command Lists}), @value{GDBN} provides two ways to store sequences of
19349 commands for execution as a unit: user-defined commands and command
19353 * Define:: How to define your own commands
19354 * Hooks:: Hooks for user-defined commands
19355 * Command Files:: How to write scripts of commands to be stored in a file
19356 * Output:: Commands for controlled output
19360 @subsection User-defined Commands
19362 @cindex user-defined command
19363 @cindex arguments, to user-defined commands
19364 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
19365 which you assign a new name as a command. This is done with the
19366 @code{define} command. User commands may accept up to 10 arguments
19367 separated by whitespace. Arguments are accessed within the user command
19368 via @code{$arg0@dots{}$arg9}. A trivial example:
19372 print $arg0 + $arg1 + $arg2
19377 To execute the command use:
19384 This defines the command @code{adder}, which prints the sum of
19385 its three arguments. Note the arguments are text substitutions, so they may
19386 reference variables, use complex expressions, or even perform inferior
19389 @cindex argument count in user-defined commands
19390 @cindex how many arguments (user-defined commands)
19391 In addition, @code{$argc} may be used to find out how many arguments have
19392 been passed. This expands to a number in the range 0@dots{}10.
19397 print $arg0 + $arg1
19400 print $arg0 + $arg1 + $arg2
19408 @item define @var{commandname}
19409 Define a command named @var{commandname}. If there is already a command
19410 by that name, you are asked to confirm that you want to redefine it.
19411 @var{commandname} may be a bare command name consisting of letters,
19412 numbers, dashes, and underscores. It may also start with any predefined
19413 prefix command. For example, @samp{define target my-target} creates
19414 a user-defined @samp{target my-target} command.
19416 The definition of the command is made up of other @value{GDBN} command lines,
19417 which are given following the @code{define} command. The end of these
19418 commands is marked by a line containing @code{end}.
19421 @kindex end@r{ (user-defined commands)}
19422 @item document @var{commandname}
19423 Document the user-defined command @var{commandname}, so that it can be
19424 accessed by @code{help}. The command @var{commandname} must already be
19425 defined. This command reads lines of documentation just as @code{define}
19426 reads the lines of the command definition, ending with @code{end}.
19427 After the @code{document} command is finished, @code{help} on command
19428 @var{commandname} displays the documentation you have written.
19430 You may use the @code{document} command again to change the
19431 documentation of a command. Redefining the command with @code{define}
19432 does not change the documentation.
19434 @kindex dont-repeat
19435 @cindex don't repeat command
19437 Used inside a user-defined command, this tells @value{GDBN} that this
19438 command should not be repeated when the user hits @key{RET}
19439 (@pxref{Command Syntax, repeat last command}).
19441 @kindex help user-defined
19442 @item help user-defined
19443 List all user-defined commands, with the first line of the documentation
19448 @itemx show user @var{commandname}
19449 Display the @value{GDBN} commands used to define @var{commandname} (but
19450 not its documentation). If no @var{commandname} is given, display the
19451 definitions for all user-defined commands.
19453 @cindex infinite recursion in user-defined commands
19454 @kindex show max-user-call-depth
19455 @kindex set max-user-call-depth
19456 @item show max-user-call-depth
19457 @itemx set max-user-call-depth
19458 The value of @code{max-user-call-depth} controls how many recursion
19459 levels are allowed in user-defined commands before @value{GDBN} suspects an
19460 infinite recursion and aborts the command.
19463 In addition to the above commands, user-defined commands frequently
19464 use control flow commands, described in @ref{Command Files}.
19466 When user-defined commands are executed, the
19467 commands of the definition are not printed. An error in any command
19468 stops execution of the user-defined command.
19470 If used interactively, commands that would ask for confirmation proceed
19471 without asking when used inside a user-defined command. Many @value{GDBN}
19472 commands that normally print messages to say what they are doing omit the
19473 messages when used in a user-defined command.
19476 @subsection User-defined Command Hooks
19477 @cindex command hooks
19478 @cindex hooks, for commands
19479 @cindex hooks, pre-command
19482 You may define @dfn{hooks}, which are a special kind of user-defined
19483 command. Whenever you run the command @samp{foo}, if the user-defined
19484 command @samp{hook-foo} exists, it is executed (with no arguments)
19485 before that command.
19487 @cindex hooks, post-command
19489 A hook may also be defined which is run after the command you executed.
19490 Whenever you run the command @samp{foo}, if the user-defined command
19491 @samp{hookpost-foo} exists, it is executed (with no arguments) after
19492 that command. Post-execution hooks may exist simultaneously with
19493 pre-execution hooks, for the same command.
19495 It is valid for a hook to call the command which it hooks. If this
19496 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
19498 @c It would be nice if hookpost could be passed a parameter indicating
19499 @c if the command it hooks executed properly or not. FIXME!
19501 @kindex stop@r{, a pseudo-command}
19502 In addition, a pseudo-command, @samp{stop} exists. Defining
19503 (@samp{hook-stop}) makes the associated commands execute every time
19504 execution stops in your program: before breakpoint commands are run,
19505 displays are printed, or the stack frame is printed.
19507 For example, to ignore @code{SIGALRM} signals while
19508 single-stepping, but treat them normally during normal execution,
19513 handle SIGALRM nopass
19517 handle SIGALRM pass
19520 define hook-continue
19521 handle SIGALRM pass
19525 As a further example, to hook at the beginning and end of the @code{echo}
19526 command, and to add extra text to the beginning and end of the message,
19534 define hookpost-echo
19538 (@value{GDBP}) echo Hello World
19539 <<<---Hello World--->>>
19544 You can define a hook for any single-word command in @value{GDBN}, but
19545 not for command aliases; you should define a hook for the basic command
19546 name, e.g.@: @code{backtrace} rather than @code{bt}.
19547 @c FIXME! So how does Joe User discover whether a command is an alias
19549 You can hook a multi-word command by adding @code{hook-} or
19550 @code{hookpost-} to the last word of the command, e.g.@:
19551 @samp{define target hook-remote} to add a hook to @samp{target remote}.
19553 If an error occurs during the execution of your hook, execution of
19554 @value{GDBN} commands stops and @value{GDBN} issues a prompt
19555 (before the command that you actually typed had a chance to run).
19557 If you try to define a hook which does not match any known command, you
19558 get a warning from the @code{define} command.
19560 @node Command Files
19561 @subsection Command Files
19563 @cindex command files
19564 @cindex scripting commands
19565 A command file for @value{GDBN} is a text file made of lines that are
19566 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
19567 also be included. An empty line in a command file does nothing; it
19568 does not mean to repeat the last command, as it would from the
19571 You can request the execution of a command file with the @code{source}
19572 command. Note that the @code{source} command is also used to evaluate
19573 scripts that are not Command Files. The exact behavior can be configured
19574 using the @code{script-extension} setting.
19575 @xref{Extending GDB,, Extending GDB}.
19579 @cindex execute commands from a file
19580 @item source [-s] [-v] @var{filename}
19581 Execute the command file @var{filename}.
19584 The lines in a command file are generally executed sequentially,
19585 unless the order of execution is changed by one of the
19586 @emph{flow-control commands} described below. The commands are not
19587 printed as they are executed. An error in any command terminates
19588 execution of the command file and control is returned to the console.
19590 @value{GDBN} first searches for @var{filename} in the current directory.
19591 If the file is not found there, and @var{filename} does not specify a
19592 directory, then @value{GDBN} also looks for the file on the source search path
19593 (specified with the @samp{directory} command);
19594 except that @file{$cdir} is not searched because the compilation directory
19595 is not relevant to scripts.
19597 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
19598 on the search path even if @var{filename} specifies a directory.
19599 The search is done by appending @var{filename} to each element of the
19600 search path. So, for example, if @var{filename} is @file{mylib/myscript}
19601 and the search path contains @file{/home/user} then @value{GDBN} will
19602 look for the script @file{/home/user/mylib/myscript}.
19603 The search is also done if @var{filename} is an absolute path.
19604 For example, if @var{filename} is @file{/tmp/myscript} and
19605 the search path contains @file{/home/user} then @value{GDBN} will
19606 look for the script @file{/home/user/tmp/myscript}.
19607 For DOS-like systems, if @var{filename} contains a drive specification,
19608 it is stripped before concatenation. For example, if @var{filename} is
19609 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
19610 will look for the script @file{c:/tmp/myscript}.
19612 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
19613 each command as it is executed. The option must be given before
19614 @var{filename}, and is interpreted as part of the filename anywhere else.
19616 Commands that would ask for confirmation if used interactively proceed
19617 without asking when used in a command file. Many @value{GDBN} commands that
19618 normally print messages to say what they are doing omit the messages
19619 when called from command files.
19621 @value{GDBN} also accepts command input from standard input. In this
19622 mode, normal output goes to standard output and error output goes to
19623 standard error. Errors in a command file supplied on standard input do
19624 not terminate execution of the command file---execution continues with
19628 gdb < cmds > log 2>&1
19631 (The syntax above will vary depending on the shell used.) This example
19632 will execute commands from the file @file{cmds}. All output and errors
19633 would be directed to @file{log}.
19635 Since commands stored on command files tend to be more general than
19636 commands typed interactively, they frequently need to deal with
19637 complicated situations, such as different or unexpected values of
19638 variables and symbols, changes in how the program being debugged is
19639 built, etc. @value{GDBN} provides a set of flow-control commands to
19640 deal with these complexities. Using these commands, you can write
19641 complex scripts that loop over data structures, execute commands
19642 conditionally, etc.
19649 This command allows to include in your script conditionally executed
19650 commands. The @code{if} command takes a single argument, which is an
19651 expression to evaluate. It is followed by a series of commands that
19652 are executed only if the expression is true (its value is nonzero).
19653 There can then optionally be an @code{else} line, followed by a series
19654 of commands that are only executed if the expression was false. The
19655 end of the list is marked by a line containing @code{end}.
19659 This command allows to write loops. Its syntax is similar to
19660 @code{if}: the command takes a single argument, which is an expression
19661 to evaluate, and must be followed by the commands to execute, one per
19662 line, terminated by an @code{end}. These commands are called the
19663 @dfn{body} of the loop. The commands in the body of @code{while} are
19664 executed repeatedly as long as the expression evaluates to true.
19668 This command exits the @code{while} loop in whose body it is included.
19669 Execution of the script continues after that @code{while}s @code{end}
19672 @kindex loop_continue
19673 @item loop_continue
19674 This command skips the execution of the rest of the body of commands
19675 in the @code{while} loop in whose body it is included. Execution
19676 branches to the beginning of the @code{while} loop, where it evaluates
19677 the controlling expression.
19679 @kindex end@r{ (if/else/while commands)}
19681 Terminate the block of commands that are the body of @code{if},
19682 @code{else}, or @code{while} flow-control commands.
19687 @subsection Commands for Controlled Output
19689 During the execution of a command file or a user-defined command, normal
19690 @value{GDBN} output is suppressed; the only output that appears is what is
19691 explicitly printed by the commands in the definition. This section
19692 describes three commands useful for generating exactly the output you
19697 @item echo @var{text}
19698 @c I do not consider backslash-space a standard C escape sequence
19699 @c because it is not in ANSI.
19700 Print @var{text}. Nonprinting characters can be included in
19701 @var{text} using C escape sequences, such as @samp{\n} to print a
19702 newline. @strong{No newline is printed unless you specify one.}
19703 In addition to the standard C escape sequences, a backslash followed
19704 by a space stands for a space. This is useful for displaying a
19705 string with spaces at the beginning or the end, since leading and
19706 trailing spaces are otherwise trimmed from all arguments.
19707 To print @samp{@w{ }and foo =@w{ }}, use the command
19708 @samp{echo \@w{ }and foo = \@w{ }}.
19710 A backslash at the end of @var{text} can be used, as in C, to continue
19711 the command onto subsequent lines. For example,
19714 echo This is some text\n\
19715 which is continued\n\
19716 onto several lines.\n
19719 produces the same output as
19722 echo This is some text\n
19723 echo which is continued\n
19724 echo onto several lines.\n
19728 @item output @var{expression}
19729 Print the value of @var{expression} and nothing but that value: no
19730 newlines, no @samp{$@var{nn} = }. The value is not entered in the
19731 value history either. @xref{Expressions, ,Expressions}, for more information
19734 @item output/@var{fmt} @var{expression}
19735 Print the value of @var{expression} in format @var{fmt}. You can use
19736 the same formats as for @code{print}. @xref{Output Formats,,Output
19737 Formats}, for more information.
19740 @item printf @var{template}, @var{expressions}@dots{}
19741 Print the values of one or more @var{expressions} under the control of
19742 the string @var{template}. To print several values, make
19743 @var{expressions} be a comma-separated list of individual expressions,
19744 which may be either numbers or pointers. Their values are printed as
19745 specified by @var{template}, exactly as a C program would do by
19746 executing the code below:
19749 printf (@var{template}, @var{expressions}@dots{});
19752 As in @code{C} @code{printf}, ordinary characters in @var{template}
19753 are printed verbatim, while @dfn{conversion specification} introduced
19754 by the @samp{%} character cause subsequent @var{expressions} to be
19755 evaluated, their values converted and formatted according to type and
19756 style information encoded in the conversion specifications, and then
19759 For example, you can print two values in hex like this:
19762 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
19765 @code{printf} supports all the standard @code{C} conversion
19766 specifications, including the flags and modifiers between the @samp{%}
19767 character and the conversion letter, with the following exceptions:
19771 The argument-ordering modifiers, such as @samp{2$}, are not supported.
19774 The modifier @samp{*} is not supported for specifying precision or
19778 The @samp{'} flag (for separation of digits into groups according to
19779 @code{LC_NUMERIC'}) is not supported.
19782 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
19786 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
19789 The conversion letters @samp{a} and @samp{A} are not supported.
19793 Note that the @samp{ll} type modifier is supported only if the
19794 underlying @code{C} implementation used to build @value{GDBN} supports
19795 the @code{long long int} type, and the @samp{L} type modifier is
19796 supported only if @code{long double} type is available.
19798 As in @code{C}, @code{printf} supports simple backslash-escape
19799 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
19800 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
19801 single character. Octal and hexadecimal escape sequences are not
19804 Additionally, @code{printf} supports conversion specifications for DFP
19805 (@dfn{Decimal Floating Point}) types using the following length modifiers
19806 together with a floating point specifier.
19811 @samp{H} for printing @code{Decimal32} types.
19814 @samp{D} for printing @code{Decimal64} types.
19817 @samp{DD} for printing @code{Decimal128} types.
19820 If the underlying @code{C} implementation used to build @value{GDBN} has
19821 support for the three length modifiers for DFP types, other modifiers
19822 such as width and precision will also be available for @value{GDBN} to use.
19824 In case there is no such @code{C} support, no additional modifiers will be
19825 available and the value will be printed in the standard way.
19827 Here's an example of printing DFP types using the above conversion letters:
19829 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
19835 @section Scripting @value{GDBN} using Python
19836 @cindex python scripting
19837 @cindex scripting with python
19839 You can script @value{GDBN} using the @uref{http://www.python.org/,
19840 Python programming language}. This feature is available only if
19841 @value{GDBN} was configured using @option{--with-python}.
19844 * Python Commands:: Accessing Python from @value{GDBN}.
19845 * Python API:: Accessing @value{GDBN} from Python.
19846 * Auto-loading:: Automatically loading Python code.
19849 @node Python Commands
19850 @subsection Python Commands
19851 @cindex python commands
19852 @cindex commands to access python
19854 @value{GDBN} provides one command for accessing the Python interpreter,
19855 and one related setting:
19859 @item python @r{[}@var{code}@r{]}
19860 The @code{python} command can be used to evaluate Python code.
19862 If given an argument, the @code{python} command will evaluate the
19863 argument as a Python command. For example:
19866 (@value{GDBP}) python print 23
19870 If you do not provide an argument to @code{python}, it will act as a
19871 multi-line command, like @code{define}. In this case, the Python
19872 script is made up of subsequent command lines, given after the
19873 @code{python} command. This command list is terminated using a line
19874 containing @code{end}. For example:
19877 (@value{GDBP}) python
19879 End with a line saying just "end".
19885 @kindex maint set python print-stack
19886 @item maint set python print-stack
19887 By default, @value{GDBN} will print a stack trace when an error occurs
19888 in a Python script. This can be controlled using @code{maint set
19889 python print-stack}: if @code{on}, the default, then Python stack
19890 printing is enabled; if @code{off}, then Python stack printing is
19894 It is also possible to execute a Python script from the @value{GDBN}
19898 @item source @file{script-name}
19899 The script name must end with @samp{.py} and @value{GDBN} must be configured
19900 to recognize the script language based on filename extension using
19901 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
19903 @item python execfile ("script-name")
19904 This method is based on the @code{execfile} Python built-in function,
19905 and thus is always available.
19909 @subsection Python API
19911 @cindex programming in python
19913 @cindex python stdout
19914 @cindex python pagination
19915 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
19916 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
19917 A Python program which outputs to one of these streams may have its
19918 output interrupted by the user (@pxref{Screen Size}). In this
19919 situation, a Python @code{KeyboardInterrupt} exception is thrown.
19922 * Basic Python:: Basic Python Functions.
19923 * Exception Handling::
19924 * Values From Inferior::
19925 * Types In Python:: Python representation of types.
19926 * Pretty Printing API:: Pretty-printing values.
19927 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
19928 * Commands In Python:: Implementing new commands in Python.
19929 * Functions In Python:: Writing new convenience functions.
19930 * Progspaces In Python:: Program spaces.
19931 * Objfiles In Python:: Object files.
19932 * Frames In Python:: Accessing inferior stack frames from Python.
19933 * Blocks In Python:: Accessing frame blocks from Python.
19934 * Symbols In Python:: Python representation of symbols.
19935 * Symbol Tables In Python:: Python representation of symbol tables.
19936 * Lazy Strings In Python:: Python representation of lazy strings.
19937 * Breakpoints In Python:: Manipulating breakpoints using Python.
19941 @subsubsection Basic Python
19943 @cindex python functions
19944 @cindex python module
19946 @value{GDBN} introduces a new Python module, named @code{gdb}. All
19947 methods and classes added by @value{GDBN} are placed in this module.
19948 @value{GDBN} automatically @code{import}s the @code{gdb} module for
19949 use in all scripts evaluated by the @code{python} command.
19951 @findex gdb.execute
19952 @defun execute command [from_tty]
19953 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
19954 If a GDB exception happens while @var{command} runs, it is
19955 translated as described in @ref{Exception Handling,,Exception Handling}.
19956 If no exceptions occur, this function returns @code{None}.
19958 @var{from_tty} specifies whether @value{GDBN} ought to consider this
19959 command as having originated from the user invoking it interactively.
19960 It must be a boolean value. If omitted, it defaults to @code{False}.
19963 @findex gdb.breakpoints
19965 Return a sequence holding all of @value{GDBN}'s breakpoints.
19966 @xref{Breakpoints In Python}, for more information.
19969 @findex gdb.parameter
19970 @defun parameter parameter
19971 Return the value of a @value{GDBN} parameter. @var{parameter} is a
19972 string naming the parameter to look up; @var{parameter} may contain
19973 spaces if the parameter has a multi-part name. For example,
19974 @samp{print object} is a valid parameter name.
19976 If the named parameter does not exist, this function throws a
19977 @code{RuntimeError}. Otherwise, the parameter's value is converted to
19978 a Python value of the appropriate type, and returned.
19981 @findex gdb.history
19982 @defun history number
19983 Return a value from @value{GDBN}'s value history (@pxref{Value
19984 History}). @var{number} indicates which history element to return.
19985 If @var{number} is negative, then @value{GDBN} will take its absolute value
19986 and count backward from the last element (i.e., the most recent element) to
19987 find the value to return. If @var{number} is zero, then @value{GDBN} will
19988 return the most recent element. If the element specified by @var{number}
19989 doesn't exist in the value history, a @code{RuntimeError} exception will be
19992 If no exception is raised, the return value is always an instance of
19993 @code{gdb.Value} (@pxref{Values From Inferior}).
19996 @findex gdb.parse_and_eval
19997 @defun parse_and_eval expression
19998 Parse @var{expression} as an expression in the current language,
19999 evaluate it, and return the result as a @code{gdb.Value}.
20000 @var{expression} must be a string.
20002 This function can be useful when implementing a new command
20003 (@pxref{Commands In Python}), as it provides a way to parse the
20004 command's argument as an expression. It is also useful simply to
20005 compute values, for example, it is the only way to get the value of a
20006 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20010 @defun write string
20011 Print a string to @value{GDBN}'s paginated standard output stream.
20012 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20013 call this function.
20018 Flush @value{GDBN}'s paginated standard output stream. Flushing
20019 @code{sys.stdout} or @code{sys.stderr} will automatically call this
20023 @findex gdb.target_charset
20024 @defun target_charset
20025 Return the name of the current target character set (@pxref{Character
20026 Sets}). This differs from @code{gdb.parameter('target-charset')} in
20027 that @samp{auto} is never returned.
20030 @findex gdb.target_wide_charset
20031 @defun target_wide_charset
20032 Return the name of the current target wide character set
20033 (@pxref{Character Sets}). This differs from
20034 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
20038 @node Exception Handling
20039 @subsubsection Exception Handling
20040 @cindex python exceptions
20041 @cindex exceptions, python
20043 When executing the @code{python} command, Python exceptions
20044 uncaught within the Python code are translated to calls to
20045 @value{GDBN} error-reporting mechanism. If the command that called
20046 @code{python} does not handle the error, @value{GDBN} will
20047 terminate it and print an error message containing the Python
20048 exception name, the associated value, and the Python call stack
20049 backtrace at the point where the exception was raised. Example:
20052 (@value{GDBP}) python print foo
20053 Traceback (most recent call last):
20054 File "<string>", line 1, in <module>
20055 NameError: name 'foo' is not defined
20058 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
20059 code are converted to Python @code{RuntimeError} exceptions. User
20060 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
20061 prompt) is translated to a Python @code{KeyboardInterrupt}
20062 exception. If you catch these exceptions in your Python code, your
20063 exception handler will see @code{RuntimeError} or
20064 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
20065 message as its value, and the Python call stack backtrace at the
20066 Python statement closest to where the @value{GDBN} error occured as the
20069 @node Values From Inferior
20070 @subsubsection Values From Inferior
20071 @cindex values from inferior, with Python
20072 @cindex python, working with values from inferior
20074 @cindex @code{gdb.Value}
20075 @value{GDBN} provides values it obtains from the inferior program in
20076 an object of type @code{gdb.Value}. @value{GDBN} uses this object
20077 for its internal bookkeeping of the inferior's values, and for
20078 fetching values when necessary.
20080 Inferior values that are simple scalars can be used directly in
20081 Python expressions that are valid for the value's data type. Here's
20082 an example for an integer or floating-point value @code{some_val}:
20089 As result of this, @code{bar} will also be a @code{gdb.Value} object
20090 whose values are of the same type as those of @code{some_val}.
20092 Inferior values that are structures or instances of some class can
20093 be accessed using the Python @dfn{dictionary syntax}. For example, if
20094 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
20095 can access its @code{foo} element with:
20098 bar = some_val['foo']
20101 Again, @code{bar} will also be a @code{gdb.Value} object.
20103 The following attributes are provided:
20106 @defivar Value address
20107 If this object is addressable, this read-only attribute holds a
20108 @code{gdb.Value} object representing the address. Otherwise,
20109 this attribute holds @code{None}.
20112 @cindex optimized out value in Python
20113 @defivar Value is_optimized_out
20114 This read-only boolean attribute is true if the compiler optimized out
20115 this value, thus it is not available for fetching from the inferior.
20118 @defivar Value type
20119 The type of this @code{gdb.Value}. The value of this attribute is a
20120 @code{gdb.Type} object.
20124 The following methods are provided:
20127 @defmethod Value cast type
20128 Return a new instance of @code{gdb.Value} that is the result of
20129 casting this instance to the type described by @var{type}, which must
20130 be a @code{gdb.Type} object. If the cast cannot be performed for some
20131 reason, this method throws an exception.
20134 @defmethod Value dereference
20135 For pointer data types, this method returns a new @code{gdb.Value} object
20136 whose contents is the object pointed to by the pointer. For example, if
20137 @code{foo} is a C pointer to an @code{int}, declared in your C program as
20144 then you can use the corresponding @code{gdb.Value} to access what
20145 @code{foo} points to like this:
20148 bar = foo.dereference ()
20151 The result @code{bar} will be a @code{gdb.Value} object holding the
20152 value pointed to by @code{foo}.
20155 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
20156 If this @code{gdb.Value} represents a string, then this method
20157 converts the contents to a Python string. Otherwise, this method will
20158 throw an exception.
20160 Strings are recognized in a language-specific way; whether a given
20161 @code{gdb.Value} represents a string is determined by the current
20164 For C-like languages, a value is a string if it is a pointer to or an
20165 array of characters or ints. The string is assumed to be terminated
20166 by a zero of the appropriate width. However if the optional length
20167 argument is given, the string will be converted to that given length,
20168 ignoring any embedded zeros that the string may contain.
20170 If the optional @var{encoding} argument is given, it must be a string
20171 naming the encoding of the string in the @code{gdb.Value}, such as
20172 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
20173 the same encodings as the corresponding argument to Python's
20174 @code{string.decode} method, and the Python codec machinery will be used
20175 to convert the string. If @var{encoding} is not given, or if
20176 @var{encoding} is the empty string, then either the @code{target-charset}
20177 (@pxref{Character Sets}) will be used, or a language-specific encoding
20178 will be used, if the current language is able to supply one.
20180 The optional @var{errors} argument is the same as the corresponding
20181 argument to Python's @code{string.decode} method.
20183 If the optional @var{length} argument is given, the string will be
20184 fetched and converted to the given length.
20187 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
20188 If this @code{gdb.Value} represents a string, then this method
20189 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
20190 In Python}). Otherwise, this method will throw an exception.
20192 If the optional @var{encoding} argument is given, it must be a string
20193 naming the encoding of the @code{gdb.LazyString}. Some examples are:
20194 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
20195 @var{encoding} argument is an encoding that @value{GDBN} does
20196 recognize, @value{GDBN} will raise an error.
20198 When a lazy string is printed, the @value{GDBN} encoding machinery is
20199 used to convert the string during printing. If the optional
20200 @var{encoding} argument is not provided, or is an empty string,
20201 @value{GDBN} will automatically select the encoding most suitable for
20202 the string type. For further information on encoding in @value{GDBN}
20203 please see @ref{Character Sets}.
20205 If the optional @var{length} argument is given, the string will be
20206 fetched and encoded to the length of characters specified. If
20207 the @var{length} argument is not provided, the string will be fetched
20208 and encoded until a null of appropriate width is found.
20212 @node Types In Python
20213 @subsubsection Types In Python
20214 @cindex types in Python
20215 @cindex Python, working with types
20218 @value{GDBN} represents types from the inferior using the class
20221 The following type-related functions are available in the @code{gdb}
20224 @findex gdb.lookup_type
20225 @defun lookup_type name [block]
20226 This function looks up a type by name. @var{name} is the name of the
20227 type to look up. It must be a string.
20229 If @var{block} is given, then @var{name} is looked up in that scope.
20230 Otherwise, it is searched for globally.
20232 Ordinarily, this function will return an instance of @code{gdb.Type}.
20233 If the named type cannot be found, it will throw an exception.
20236 An instance of @code{Type} has the following attributes:
20240 The type code for this type. The type code will be one of the
20241 @code{TYPE_CODE_} constants defined below.
20244 @defivar Type sizeof
20245 The size of this type, in target @code{char} units. Usually, a
20246 target's @code{char} type will be an 8-bit byte. However, on some
20247 unusual platforms, this type may have a different size.
20251 The tag name for this type. The tag name is the name after
20252 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
20253 languages have this concept. If this type has no tag name, then
20254 @code{None} is returned.
20258 The following methods are provided:
20261 @defmethod Type fields
20262 For structure and union types, this method returns the fields. Range
20263 types have two fields, the minimum and maximum values. Enum types
20264 have one field per enum constant. Function and method types have one
20265 field per parameter. The base types of C@t{++} classes are also
20266 represented as fields. If the type has no fields, or does not fit
20267 into one of these categories, an empty sequence will be returned.
20269 Each field is an object, with some pre-defined attributes:
20272 This attribute is not available for @code{static} fields (as in
20273 C@t{++} or Java). For non-@code{static} fields, the value is the bit
20274 position of the field.
20277 The name of the field, or @code{None} for anonymous fields.
20280 This is @code{True} if the field is artificial, usually meaning that
20281 it was provided by the compiler and not the user. This attribute is
20282 always provided, and is @code{False} if the field is not artificial.
20284 @item is_base_class
20285 This is @code{True} if the field represents a base class of a C@t{++}
20286 structure. This attribute is always provided, and is @code{False}
20287 if the field is not a base class of the type that is the argument of
20288 @code{fields}, or if that type was not a C@t{++} class.
20291 If the field is packed, or is a bitfield, then this will have a
20292 non-zero value, which is the size of the field in bits. Otherwise,
20293 this will be zero; in this case the field's size is given by its type.
20296 The type of the field. This is usually an instance of @code{Type},
20297 but it can be @code{None} in some situations.
20301 @defmethod Type const
20302 Return a new @code{gdb.Type} object which represents a
20303 @code{const}-qualified variant of this type.
20306 @defmethod Type volatile
20307 Return a new @code{gdb.Type} object which represents a
20308 @code{volatile}-qualified variant of this type.
20311 @defmethod Type unqualified
20312 Return a new @code{gdb.Type} object which represents an unqualified
20313 variant of this type. That is, the result is neither @code{const} nor
20317 @defmethod Type range
20318 Return a Python @code{Tuple} object that contains two elements: the
20319 low bound of the argument type and the high bound of that type. If
20320 the type does not have a range, @value{GDBN} will raise a
20321 @code{RuntimeError} exception.
20324 @defmethod Type reference
20325 Return a new @code{gdb.Type} object which represents a reference to this
20329 @defmethod Type pointer
20330 Return a new @code{gdb.Type} object which represents a pointer to this
20334 @defmethod Type strip_typedefs
20335 Return a new @code{gdb.Type} that represents the real type,
20336 after removing all layers of typedefs.
20339 @defmethod Type target
20340 Return a new @code{gdb.Type} object which represents the target type
20343 For a pointer type, the target type is the type of the pointed-to
20344 object. For an array type (meaning C-like arrays), the target type is
20345 the type of the elements of the array. For a function or method type,
20346 the target type is the type of the return value. For a complex type,
20347 the target type is the type of the elements. For a typedef, the
20348 target type is the aliased type.
20350 If the type does not have a target, this method will throw an
20354 @defmethod Type template_argument n [block]
20355 If this @code{gdb.Type} is an instantiation of a template, this will
20356 return a new @code{gdb.Type} which represents the type of the
20357 @var{n}th template argument.
20359 If this @code{gdb.Type} is not a template type, this will throw an
20360 exception. Ordinarily, only C@t{++} code will have template types.
20362 If @var{block} is given, then @var{name} is looked up in that scope.
20363 Otherwise, it is searched for globally.
20368 Each type has a code, which indicates what category this type falls
20369 into. The available type categories are represented by constants
20370 defined in the @code{gdb} module:
20373 @findex TYPE_CODE_PTR
20374 @findex gdb.TYPE_CODE_PTR
20375 @item TYPE_CODE_PTR
20376 The type is a pointer.
20378 @findex TYPE_CODE_ARRAY
20379 @findex gdb.TYPE_CODE_ARRAY
20380 @item TYPE_CODE_ARRAY
20381 The type is an array.
20383 @findex TYPE_CODE_STRUCT
20384 @findex gdb.TYPE_CODE_STRUCT
20385 @item TYPE_CODE_STRUCT
20386 The type is a structure.
20388 @findex TYPE_CODE_UNION
20389 @findex gdb.TYPE_CODE_UNION
20390 @item TYPE_CODE_UNION
20391 The type is a union.
20393 @findex TYPE_CODE_ENUM
20394 @findex gdb.TYPE_CODE_ENUM
20395 @item TYPE_CODE_ENUM
20396 The type is an enum.
20398 @findex TYPE_CODE_FLAGS
20399 @findex gdb.TYPE_CODE_FLAGS
20400 @item TYPE_CODE_FLAGS
20401 A bit flags type, used for things such as status registers.
20403 @findex TYPE_CODE_FUNC
20404 @findex gdb.TYPE_CODE_FUNC
20405 @item TYPE_CODE_FUNC
20406 The type is a function.
20408 @findex TYPE_CODE_INT
20409 @findex gdb.TYPE_CODE_INT
20410 @item TYPE_CODE_INT
20411 The type is an integer type.
20413 @findex TYPE_CODE_FLT
20414 @findex gdb.TYPE_CODE_FLT
20415 @item TYPE_CODE_FLT
20416 A floating point type.
20418 @findex TYPE_CODE_VOID
20419 @findex gdb.TYPE_CODE_VOID
20420 @item TYPE_CODE_VOID
20421 The special type @code{void}.
20423 @findex TYPE_CODE_SET
20424 @findex gdb.TYPE_CODE_SET
20425 @item TYPE_CODE_SET
20428 @findex TYPE_CODE_RANGE
20429 @findex gdb.TYPE_CODE_RANGE
20430 @item TYPE_CODE_RANGE
20431 A range type, that is, an integer type with bounds.
20433 @findex TYPE_CODE_STRING
20434 @findex gdb.TYPE_CODE_STRING
20435 @item TYPE_CODE_STRING
20436 A string type. Note that this is only used for certain languages with
20437 language-defined string types; C strings are not represented this way.
20439 @findex TYPE_CODE_BITSTRING
20440 @findex gdb.TYPE_CODE_BITSTRING
20441 @item TYPE_CODE_BITSTRING
20444 @findex TYPE_CODE_ERROR
20445 @findex gdb.TYPE_CODE_ERROR
20446 @item TYPE_CODE_ERROR
20447 An unknown or erroneous type.
20449 @findex TYPE_CODE_METHOD
20450 @findex gdb.TYPE_CODE_METHOD
20451 @item TYPE_CODE_METHOD
20452 A method type, as found in C@t{++} or Java.
20454 @findex TYPE_CODE_METHODPTR
20455 @findex gdb.TYPE_CODE_METHODPTR
20456 @item TYPE_CODE_METHODPTR
20457 A pointer-to-member-function.
20459 @findex TYPE_CODE_MEMBERPTR
20460 @findex gdb.TYPE_CODE_MEMBERPTR
20461 @item TYPE_CODE_MEMBERPTR
20462 A pointer-to-member.
20464 @findex TYPE_CODE_REF
20465 @findex gdb.TYPE_CODE_REF
20466 @item TYPE_CODE_REF
20469 @findex TYPE_CODE_CHAR
20470 @findex gdb.TYPE_CODE_CHAR
20471 @item TYPE_CODE_CHAR
20474 @findex TYPE_CODE_BOOL
20475 @findex gdb.TYPE_CODE_BOOL
20476 @item TYPE_CODE_BOOL
20479 @findex TYPE_CODE_COMPLEX
20480 @findex gdb.TYPE_CODE_COMPLEX
20481 @item TYPE_CODE_COMPLEX
20482 A complex float type.
20484 @findex TYPE_CODE_TYPEDEF
20485 @findex gdb.TYPE_CODE_TYPEDEF
20486 @item TYPE_CODE_TYPEDEF
20487 A typedef to some other type.
20489 @findex TYPE_CODE_NAMESPACE
20490 @findex gdb.TYPE_CODE_NAMESPACE
20491 @item TYPE_CODE_NAMESPACE
20492 A C@t{++} namespace.
20494 @findex TYPE_CODE_DECFLOAT
20495 @findex gdb.TYPE_CODE_DECFLOAT
20496 @item TYPE_CODE_DECFLOAT
20497 A decimal floating point type.
20499 @findex TYPE_CODE_INTERNAL_FUNCTION
20500 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
20501 @item TYPE_CODE_INTERNAL_FUNCTION
20502 A function internal to @value{GDBN}. This is the type used to represent
20503 convenience functions.
20506 @node Pretty Printing API
20507 @subsubsection Pretty Printing API
20509 An example output is provided (@pxref{Pretty Printing}).
20511 A pretty-printer is just an object that holds a value and implements a
20512 specific interface, defined here.
20514 @defop Operation {pretty printer} children (self)
20515 @value{GDBN} will call this method on a pretty-printer to compute the
20516 children of the pretty-printer's value.
20518 This method must return an object conforming to the Python iterator
20519 protocol. Each item returned by the iterator must be a tuple holding
20520 two elements. The first element is the ``name'' of the child; the
20521 second element is the child's value. The value can be any Python
20522 object which is convertible to a @value{GDBN} value.
20524 This method is optional. If it does not exist, @value{GDBN} will act
20525 as though the value has no children.
20528 @defop Operation {pretty printer} display_hint (self)
20529 The CLI may call this method and use its result to change the
20530 formatting of a value. The result will also be supplied to an MI
20531 consumer as a @samp{displayhint} attribute of the variable being
20534 This method is optional. If it does exist, this method must return a
20537 Some display hints are predefined by @value{GDBN}:
20541 Indicate that the object being printed is ``array-like''. The CLI
20542 uses this to respect parameters such as @code{set print elements} and
20543 @code{set print array}.
20546 Indicate that the object being printed is ``map-like'', and that the
20547 children of this value can be assumed to alternate between keys and
20551 Indicate that the object being printed is ``string-like''. If the
20552 printer's @code{to_string} method returns a Python string of some
20553 kind, then @value{GDBN} will call its internal language-specific
20554 string-printing function to format the string. For the CLI this means
20555 adding quotation marks, possibly escaping some characters, respecting
20556 @code{set print elements}, and the like.
20560 @defop Operation {pretty printer} to_string (self)
20561 @value{GDBN} will call this method to display the string
20562 representation of the value passed to the object's constructor.
20564 When printing from the CLI, if the @code{to_string} method exists,
20565 then @value{GDBN} will prepend its result to the values returned by
20566 @code{children}. Exactly how this formatting is done is dependent on
20567 the display hint, and may change as more hints are added. Also,
20568 depending on the print settings (@pxref{Print Settings}), the CLI may
20569 print just the result of @code{to_string} in a stack trace, omitting
20570 the result of @code{children}.
20572 If this method returns a string, it is printed verbatim.
20574 Otherwise, if this method returns an instance of @code{gdb.Value},
20575 then @value{GDBN} prints this value. This may result in a call to
20576 another pretty-printer.
20578 If instead the method returns a Python value which is convertible to a
20579 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
20580 the resulting value. Again, this may result in a call to another
20581 pretty-printer. Python scalars (integers, floats, and booleans) and
20582 strings are convertible to @code{gdb.Value}; other types are not.
20584 Finally, if this method returns @code{None} then no further operations
20585 are peformed in this method and nothing is printed.
20587 If the result is not one of these types, an exception is raised.
20590 @node Selecting Pretty-Printers
20591 @subsubsection Selecting Pretty-Printers
20593 The Python list @code{gdb.pretty_printers} contains an array of
20594 functions that have been registered via addition as a pretty-printer.
20595 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
20596 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
20599 A function on one of these lists is passed a single @code{gdb.Value}
20600 argument and should return a pretty-printer object conforming to the
20601 interface definition above (@pxref{Pretty Printing API}). If a function
20602 cannot create a pretty-printer for the value, it should return
20605 @value{GDBN} first checks the @code{pretty_printers} attribute of each
20606 @code{gdb.Objfile} in the current program space and iteratively calls
20607 each function in the list for that @code{gdb.Objfile} until it receives
20608 a pretty-printer object.
20609 If no pretty-printer is found in the objfile lists, @value{GDBN} then
20610 searches the pretty-printer list of the current program space,
20611 calling each function until an object is returned.
20612 After these lists have been exhausted, it tries the global
20613 @code{gdb.pretty-printers} list, again calling each function until an
20614 object is returned.
20616 The order in which the objfiles are searched is not specified. For a
20617 given list, functions are always invoked from the head of the list,
20618 and iterated over sequentially until the end of the list, or a printer
20619 object is returned.
20621 Here is an example showing how a @code{std::string} printer might be
20625 class StdStringPrinter:
20626 "Print a std::string"
20628 def __init__ (self, val):
20631 def to_string (self):
20632 return self.val['_M_dataplus']['_M_p']
20634 def display_hint (self):
20638 And here is an example showing how a lookup function for the printer
20639 example above might be written.
20642 def str_lookup_function (val):
20644 lookup_tag = val.type.tag
20645 regex = re.compile ("^std::basic_string<char,.*>$")
20646 if lookup_tag == None:
20648 if regex.match (lookup_tag):
20649 return StdStringPrinter (val)
20654 The example lookup function extracts the value's type, and attempts to
20655 match it to a type that it can pretty-print. If it is a type the
20656 printer can pretty-print, it will return a printer object. If not, it
20657 returns @code{None}.
20659 We recommend that you put your core pretty-printers into a Python
20660 package. If your pretty-printers are for use with a library, we
20661 further recommend embedding a version number into the package name.
20662 This practice will enable @value{GDBN} to load multiple versions of
20663 your pretty-printers at the same time, because they will have
20666 You should write auto-loaded code (@pxref{Auto-loading}) such that it
20667 can be evaluated multiple times without changing its meaning. An
20668 ideal auto-load file will consist solely of @code{import}s of your
20669 printer modules, followed by a call to a register pretty-printers with
20670 the current objfile.
20672 Taken as a whole, this approach will scale nicely to multiple
20673 inferiors, each potentially using a different library version.
20674 Embedding a version number in the Python package name will ensure that
20675 @value{GDBN} is able to load both sets of printers simultaneously.
20676 Then, because the search for pretty-printers is done by objfile, and
20677 because your auto-loaded code took care to register your library's
20678 printers with a specific objfile, @value{GDBN} will find the correct
20679 printers for the specific version of the library used by each
20682 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
20683 this code might appear in @code{gdb.libstdcxx.v6}:
20686 def register_printers (objfile):
20687 objfile.pretty_printers.add (str_lookup_function)
20691 And then the corresponding contents of the auto-load file would be:
20694 import gdb.libstdcxx.v6
20695 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
20698 @node Commands In Python
20699 @subsubsection Commands In Python
20701 @cindex commands in python
20702 @cindex python commands
20703 You can implement new @value{GDBN} CLI commands in Python. A CLI
20704 command is implemented using an instance of the @code{gdb.Command}
20705 class, most commonly using a subclass.
20707 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
20708 The object initializer for @code{Command} registers the new command
20709 with @value{GDBN}. This initializer is normally invoked from the
20710 subclass' own @code{__init__} method.
20712 @var{name} is the name of the command. If @var{name} consists of
20713 multiple words, then the initial words are looked for as prefix
20714 commands. In this case, if one of the prefix commands does not exist,
20715 an exception is raised.
20717 There is no support for multi-line commands.
20719 @var{command_class} should be one of the @samp{COMMAND_} constants
20720 defined below. This argument tells @value{GDBN} how to categorize the
20721 new command in the help system.
20723 @var{completer_class} is an optional argument. If given, it should be
20724 one of the @samp{COMPLETE_} constants defined below. This argument
20725 tells @value{GDBN} how to perform completion for this command. If not
20726 given, @value{GDBN} will attempt to complete using the object's
20727 @code{complete} method (see below); if no such method is found, an
20728 error will occur when completion is attempted.
20730 @var{prefix} is an optional argument. If @code{True}, then the new
20731 command is a prefix command; sub-commands of this command may be
20734 The help text for the new command is taken from the Python
20735 documentation string for the command's class, if there is one. If no
20736 documentation string is provided, the default value ``This command is
20737 not documented.'' is used.
20740 @cindex don't repeat Python command
20741 @defmethod Command dont_repeat
20742 By default, a @value{GDBN} command is repeated when the user enters a
20743 blank line at the command prompt. A command can suppress this
20744 behavior by invoking the @code{dont_repeat} method. This is similar
20745 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
20748 @defmethod Command invoke argument from_tty
20749 This method is called by @value{GDBN} when this command is invoked.
20751 @var{argument} is a string. It is the argument to the command, after
20752 leading and trailing whitespace has been stripped.
20754 @var{from_tty} is a boolean argument. When true, this means that the
20755 command was entered by the user at the terminal; when false it means
20756 that the command came from elsewhere.
20758 If this method throws an exception, it is turned into a @value{GDBN}
20759 @code{error} call. Otherwise, the return value is ignored.
20762 @cindex completion of Python commands
20763 @defmethod Command complete text word
20764 This method is called by @value{GDBN} when the user attempts
20765 completion on this command. All forms of completion are handled by
20766 this method, that is, the @key{TAB} and @key{M-?} key bindings
20767 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
20770 The arguments @var{text} and @var{word} are both strings. @var{text}
20771 holds the complete command line up to the cursor's location.
20772 @var{word} holds the last word of the command line; this is computed
20773 using a word-breaking heuristic.
20775 The @code{complete} method can return several values:
20778 If the return value is a sequence, the contents of the sequence are
20779 used as the completions. It is up to @code{complete} to ensure that the
20780 contents actually do complete the word. A zero-length sequence is
20781 allowed, it means that there were no completions available. Only
20782 string elements of the sequence are used; other elements in the
20783 sequence are ignored.
20786 If the return value is one of the @samp{COMPLETE_} constants defined
20787 below, then the corresponding @value{GDBN}-internal completion
20788 function is invoked, and its result is used.
20791 All other results are treated as though there were no available
20796 When a new command is registered, it must be declared as a member of
20797 some general class of commands. This is used to classify top-level
20798 commands in the on-line help system; note that prefix commands are not
20799 listed under their own category but rather that of their top-level
20800 command. The available classifications are represented by constants
20801 defined in the @code{gdb} module:
20804 @findex COMMAND_NONE
20805 @findex gdb.COMMAND_NONE
20807 The command does not belong to any particular class. A command in
20808 this category will not be displayed in any of the help categories.
20810 @findex COMMAND_RUNNING
20811 @findex gdb.COMMAND_RUNNING
20812 @item COMMAND_RUNNING
20813 The command is related to running the inferior. For example,
20814 @code{start}, @code{step}, and @code{continue} are in this category.
20815 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
20816 commands in this category.
20818 @findex COMMAND_DATA
20819 @findex gdb.COMMAND_DATA
20821 The command is related to data or variables. For example,
20822 @code{call}, @code{find}, and @code{print} are in this category. Type
20823 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
20826 @findex COMMAND_STACK
20827 @findex gdb.COMMAND_STACK
20828 @item COMMAND_STACK
20829 The command has to do with manipulation of the stack. For example,
20830 @code{backtrace}, @code{frame}, and @code{return} are in this
20831 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
20832 list of commands in this category.
20834 @findex COMMAND_FILES
20835 @findex gdb.COMMAND_FILES
20836 @item COMMAND_FILES
20837 This class is used for file-related commands. For example,
20838 @code{file}, @code{list} and @code{section} are in this category.
20839 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
20840 commands in this category.
20842 @findex COMMAND_SUPPORT
20843 @findex gdb.COMMAND_SUPPORT
20844 @item COMMAND_SUPPORT
20845 This should be used for ``support facilities'', generally meaning
20846 things that are useful to the user when interacting with @value{GDBN},
20847 but not related to the state of the inferior. For example,
20848 @code{help}, @code{make}, and @code{shell} are in this category. Type
20849 @kbd{help support} at the @value{GDBN} prompt to see a list of
20850 commands in this category.
20852 @findex COMMAND_STATUS
20853 @findex gdb.COMMAND_STATUS
20854 @item COMMAND_STATUS
20855 The command is an @samp{info}-related command, that is, related to the
20856 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
20857 and @code{show} are in this category. Type @kbd{help status} at the
20858 @value{GDBN} prompt to see a list of commands in this category.
20860 @findex COMMAND_BREAKPOINTS
20861 @findex gdb.COMMAND_BREAKPOINTS
20862 @item COMMAND_BREAKPOINTS
20863 The command has to do with breakpoints. For example, @code{break},
20864 @code{clear}, and @code{delete} are in this category. Type @kbd{help
20865 breakpoints} at the @value{GDBN} prompt to see a list of commands in
20868 @findex COMMAND_TRACEPOINTS
20869 @findex gdb.COMMAND_TRACEPOINTS
20870 @item COMMAND_TRACEPOINTS
20871 The command has to do with tracepoints. For example, @code{trace},
20872 @code{actions}, and @code{tfind} are in this category. Type
20873 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
20874 commands in this category.
20876 @findex COMMAND_OBSCURE
20877 @findex gdb.COMMAND_OBSCURE
20878 @item COMMAND_OBSCURE
20879 The command is only used in unusual circumstances, or is not of
20880 general interest to users. For example, @code{checkpoint},
20881 @code{fork}, and @code{stop} are in this category. Type @kbd{help
20882 obscure} at the @value{GDBN} prompt to see a list of commands in this
20885 @findex COMMAND_MAINTENANCE
20886 @findex gdb.COMMAND_MAINTENANCE
20887 @item COMMAND_MAINTENANCE
20888 The command is only useful to @value{GDBN} maintainers. The
20889 @code{maintenance} and @code{flushregs} commands are in this category.
20890 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
20891 commands in this category.
20894 A new command can use a predefined completion function, either by
20895 specifying it via an argument at initialization, or by returning it
20896 from the @code{complete} method. These predefined completion
20897 constants are all defined in the @code{gdb} module:
20900 @findex COMPLETE_NONE
20901 @findex gdb.COMPLETE_NONE
20902 @item COMPLETE_NONE
20903 This constant means that no completion should be done.
20905 @findex COMPLETE_FILENAME
20906 @findex gdb.COMPLETE_FILENAME
20907 @item COMPLETE_FILENAME
20908 This constant means that filename completion should be performed.
20910 @findex COMPLETE_LOCATION
20911 @findex gdb.COMPLETE_LOCATION
20912 @item COMPLETE_LOCATION
20913 This constant means that location completion should be done.
20914 @xref{Specify Location}.
20916 @findex COMPLETE_COMMAND
20917 @findex gdb.COMPLETE_COMMAND
20918 @item COMPLETE_COMMAND
20919 This constant means that completion should examine @value{GDBN}
20922 @findex COMPLETE_SYMBOL
20923 @findex gdb.COMPLETE_SYMBOL
20924 @item COMPLETE_SYMBOL
20925 This constant means that completion should be done using symbol names
20929 The following code snippet shows how a trivial CLI command can be
20930 implemented in Python:
20933 class HelloWorld (gdb.Command):
20934 """Greet the whole world."""
20936 def __init__ (self):
20937 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20939 def invoke (self, arg, from_tty):
20940 print "Hello, World!"
20945 The last line instantiates the class, and is necessary to trigger the
20946 registration of the command with @value{GDBN}. Depending on how the
20947 Python code is read into @value{GDBN}, you may need to import the
20948 @code{gdb} module explicitly.
20950 @node Functions In Python
20951 @subsubsection Writing new convenience functions
20953 @cindex writing convenience functions
20954 @cindex convenience functions in python
20955 @cindex python convenience functions
20956 @tindex gdb.Function
20958 You can implement new convenience functions (@pxref{Convenience Vars})
20959 in Python. A convenience function is an instance of a subclass of the
20960 class @code{gdb.Function}.
20962 @defmethod Function __init__ name
20963 The initializer for @code{Function} registers the new function with
20964 @value{GDBN}. The argument @var{name} is the name of the function,
20965 a string. The function will be visible to the user as a convenience
20966 variable of type @code{internal function}, whose name is the same as
20967 the given @var{name}.
20969 The documentation for the new function is taken from the documentation
20970 string for the new class.
20973 @defmethod Function invoke @var{*args}
20974 When a convenience function is evaluated, its arguments are converted
20975 to instances of @code{gdb.Value}, and then the function's
20976 @code{invoke} method is called. Note that @value{GDBN} does not
20977 predetermine the arity of convenience functions. Instead, all
20978 available arguments are passed to @code{invoke}, following the
20979 standard Python calling convention. In particular, a convenience
20980 function can have default values for parameters without ill effect.
20982 The return value of this method is used as its value in the enclosing
20983 expression. If an ordinary Python value is returned, it is converted
20984 to a @code{gdb.Value} following the usual rules.
20987 The following code snippet shows how a trivial convenience function can
20988 be implemented in Python:
20991 class Greet (gdb.Function):
20992 """Return string to greet someone.
20993 Takes a name as argument."""
20995 def __init__ (self):
20996 super (Greet, self).__init__ ("greet")
20998 def invoke (self, name):
20999 return "Hello, %s!" % name.string ()
21004 The last line instantiates the class, and is necessary to trigger the
21005 registration of the function with @value{GDBN}. Depending on how the
21006 Python code is read into @value{GDBN}, you may need to import the
21007 @code{gdb} module explicitly.
21009 @node Progspaces In Python
21010 @subsubsection Program Spaces In Python
21012 @cindex progspaces in python
21013 @tindex gdb.Progspace
21015 A program space, or @dfn{progspace}, represents a symbolic view
21016 of an address space.
21017 It consists of all of the objfiles of the program.
21018 @xref{Objfiles In Python}.
21019 @xref{Inferiors and Programs, program spaces}, for more details
21020 about program spaces.
21022 The following progspace-related functions are available in the
21025 @findex gdb.current_progspace
21026 @defun current_progspace
21027 This function returns the program space of the currently selected inferior.
21028 @xref{Inferiors and Programs}.
21031 @findex gdb.progspaces
21033 Return a sequence of all the progspaces currently known to @value{GDBN}.
21036 Each progspace is represented by an instance of the @code{gdb.Progspace}
21039 @defivar Progspace filename
21040 The file name of the progspace as a string.
21043 @defivar Progspace pretty_printers
21044 The @code{pretty_printers} attribute is a list of functions. It is
21045 used to look up pretty-printers. A @code{Value} is passed to each
21046 function in order; if the function returns @code{None}, then the
21047 search continues. Otherwise, the return value should be an object
21048 which is used to format the value. @xref{Pretty Printing API}, for more
21052 @node Objfiles In Python
21053 @subsubsection Objfiles In Python
21055 @cindex objfiles in python
21056 @tindex gdb.Objfile
21058 @value{GDBN} loads symbols for an inferior from various
21059 symbol-containing files (@pxref{Files}). These include the primary
21060 executable file, any shared libraries used by the inferior, and any
21061 separate debug info files (@pxref{Separate Debug Files}).
21062 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
21064 The following objfile-related functions are available in the
21067 @findex gdb.current_objfile
21068 @defun current_objfile
21069 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
21070 sets the ``current objfile'' to the corresponding objfile. This
21071 function returns the current objfile. If there is no current objfile,
21072 this function returns @code{None}.
21075 @findex gdb.objfiles
21077 Return a sequence of all the objfiles current known to @value{GDBN}.
21078 @xref{Objfiles In Python}.
21081 Each objfile is represented by an instance of the @code{gdb.Objfile}
21084 @defivar Objfile filename
21085 The file name of the objfile as a string.
21088 @defivar Objfile pretty_printers
21089 The @code{pretty_printers} attribute is a list of functions. It is
21090 used to look up pretty-printers. A @code{Value} is passed to each
21091 function in order; if the function returns @code{None}, then the
21092 search continues. Otherwise, the return value should be an object
21093 which is used to format the value. @xref{Pretty Printing API}, for more
21097 @node Frames In Python
21098 @subsubsection Accessing inferior stack frames from Python.
21100 @cindex frames in python
21101 When the debugged program stops, @value{GDBN} is able to analyze its call
21102 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
21103 represents a frame in the stack. A @code{gdb.Frame} object is only valid
21104 while its corresponding frame exists in the inferior's stack. If you try
21105 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
21108 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
21112 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
21116 The following frame-related functions are available in the @code{gdb} module:
21118 @findex gdb.selected_frame
21119 @defun selected_frame
21120 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
21123 @defun frame_stop_reason_string reason
21124 Return a string explaining the reason why @value{GDBN} stopped unwinding
21125 frames, as expressed by the given @var{reason} code (an integer, see the
21126 @code{unwind_stop_reason} method further down in this section).
21129 A @code{gdb.Frame} object has the following methods:
21132 @defmethod Frame is_valid
21133 Returns true if the @code{gdb.Frame} object is valid, false if not.
21134 A frame object can become invalid if the frame it refers to doesn't
21135 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
21136 an exception if it is invalid at the time the method is called.
21139 @defmethod Frame name
21140 Returns the function name of the frame, or @code{None} if it can't be
21144 @defmethod Frame type
21145 Returns the type of the frame. The value can be one of
21146 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
21147 or @code{gdb.SENTINEL_FRAME}.
21150 @defmethod Frame unwind_stop_reason
21151 Return an integer representing the reason why it's not possible to find
21152 more frames toward the outermost frame. Use
21153 @code{gdb.frame_stop_reason_string} to convert the value returned by this
21154 function to a string.
21157 @defmethod Frame pc
21158 Returns the frame's resume address.
21161 @defmethod Frame block
21162 Return the frame's code block. @xref{Blocks In Python}.
21165 @defmethod Frame function
21166 Return the symbol for the function corresponding to this frame.
21167 @xref{Symbols In Python}.
21170 @defmethod Frame older
21171 Return the frame that called this frame.
21174 @defmethod Frame newer
21175 Return the frame called by this frame.
21178 @defmethod Frame find_sal
21179 Return the frame's symtab and line object.
21180 @xref{Symbol Tables In Python}.
21183 @defmethod Frame read_var variable @r{[}block@r{]}
21184 Return the value of @var{variable} in this frame. If the optional
21185 argument @var{block} is provided, search for the variable from that
21186 block; otherwise start at the frame's current block (which is
21187 determined by the frame's current program counter). @var{variable}
21188 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
21189 @code{gdb.Block} object.
21192 @defmethod Frame select
21193 Set this frame to be the selected frame. @xref{Stack, ,Examining the
21198 @node Blocks In Python
21199 @subsubsection Accessing frame blocks from Python.
21201 @cindex blocks in python
21204 Within each frame, @value{GDBN} maintains information on each block
21205 stored in that frame. These blocks are organized hierarchically, and
21206 are represented individually in Python as a @code{gdb.Block}.
21207 Please see @ref{Frames In Python}, for a more in-depth discussion on
21208 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
21209 detailed technical information on @value{GDBN}'s book-keeping of the
21212 The following block-related functions are available in the @code{gdb}
21215 @findex gdb.block_for_pc
21216 @defun block_for_pc pc
21217 Return the @code{gdb.Block} containing the given @var{pc} value. If the
21218 block cannot be found for the @var{pc} value specified, the function
21219 will return @code{None}.
21222 A @code{gdb.Block} object has the following attributes:
21225 @defivar Block start
21226 The start address of the block. This attribute is not writable.
21230 The end address of the block. This attribute is not writable.
21233 @defivar Block function
21234 The name of the block represented as a @code{gdb.Symbol}. If the
21235 block is not named, then this attribute holds @code{None}. This
21236 attribute is not writable.
21239 @defivar Block superblock
21240 The block containing this block. If this parent block does not exist,
21241 this attribute holds @code{None}. This attribute is not writable.
21245 @node Symbols In Python
21246 @subsubsection Python representation of Symbols.
21248 @cindex symbols in python
21251 @value{GDBN} represents every variable, function and type as an
21252 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
21253 Similarly, Python represents these symbols in @value{GDBN} with the
21254 @code{gdb.Symbol} object.
21256 The following symbol-related functions are available in the @code{gdb}
21259 @findex gdb.lookup_symbol
21260 @defun lookup_symbol name [block] [domain]
21261 This function searches for a symbol by name. The search scope can be
21262 restricted to the parameters defined in the optional domain and block
21265 @var{name} is the name of the symbol. It must be a string. The
21266 optional @var{block} argument restricts the search to symbols visible
21267 in that @var{block}. The @var{block} argument must be a
21268 @code{gdb.Block} object. The optional @var{domain} argument restricts
21269 the search to the domain type. The @var{domain} argument must be a
21270 domain constant defined in the @code{gdb} module and described later
21274 A @code{gdb.Symbol} object has the following attributes:
21277 @defivar Symbol symtab
21278 The symbol table in which the symbol appears. This attribute is
21279 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
21280 Python}. This attribute is not writable.
21283 @defivar Symbol name
21284 The name of the symbol as a string. This attribute is not writable.
21287 @defivar Symbol linkage_name
21288 The name of the symbol, as used by the linker (i.e., may be mangled).
21289 This attribute is not writable.
21292 @defivar Symbol print_name
21293 The name of the symbol in a form suitable for output. This is either
21294 @code{name} or @code{linkage_name}, depending on whether the user
21295 asked @value{GDBN} to display demangled or mangled names.
21298 @defivar Symbol addr_class
21299 The address class of the symbol. This classifies how to find the value
21300 of a symbol. Each address class is a constant defined in the
21301 @code{gdb} module and described later in this chapter.
21304 @defivar Symbol is_argument
21305 @code{True} if the symbol is an argument of a function.
21308 @defivar Symbol is_constant
21309 @code{True} if the symbol is a constant.
21312 @defivar Symbol is_function
21313 @code{True} if the symbol is a function or a method.
21316 @defivar Symbol is_variable
21317 @code{True} if the symbol is a variable.
21321 The available domain categories in @code{gdb.Symbol} are represented
21322 as constants in the @code{gdb} module:
21325 @findex SYMBOL_UNDEF_DOMAIN
21326 @findex gdb.SYMBOL_UNDEF_DOMAIN
21327 @item SYMBOL_UNDEF_DOMAIN
21328 This is used when a domain has not been discovered or none of the
21329 following domains apply. This usually indicates an error either
21330 in the symbol information or in @value{GDBN}'s handling of symbols.
21331 @findex SYMBOL_VAR_DOMAIN
21332 @findex gdb.SYMBOL_VAR_DOMAIN
21333 @item SYMBOL_VAR_DOMAIN
21334 This domain contains variables, function names, typedef names and enum
21336 @findex SYMBOL_STRUCT_DOMAIN
21337 @findex gdb.SYMBOL_STRUCT_DOMAIN
21338 @item SYMBOL_STRUCT_DOMAIN
21339 This domain holds struct, union and enum type names.
21340 @findex SYMBOL_LABEL_DOMAIN
21341 @findex gdb.SYMBOL_LABEL_DOMAIN
21342 @item SYMBOL_LABEL_DOMAIN
21343 This domain contains names of labels (for gotos).
21344 @findex SYMBOL_VARIABLES_DOMAIN
21345 @findex gdb.SYMBOL_VARIABLES_DOMAIN
21346 @item SYMBOL_VARIABLES_DOMAIN
21347 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
21348 contains everything minus functions and types.
21349 @findex SYMBOL_FUNCTIONS_DOMAIN
21350 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
21351 @item SYMBOL_FUNCTION_DOMAIN
21352 This domain contains all functions.
21353 @findex SYMBOL_TYPES_DOMAIN
21354 @findex gdb.SYMBOL_TYPES_DOMAIN
21355 @item SYMBOL_TYPES_DOMAIN
21356 This domain contains all types.
21359 The available address class categories in @code{gdb.Symbol} are represented
21360 as constants in the @code{gdb} module:
21363 @findex SYMBOL_LOC_UNDEF
21364 @findex gdb.SYMBOL_LOC_UNDEF
21365 @item SYMBOL_LOC_UNDEF
21366 If this is returned by address class, it indicates an error either in
21367 the symbol information or in @value{GDBN}'s handling of symbols.
21368 @findex SYMBOL_LOC_CONST
21369 @findex gdb.SYMBOL_LOC_CONST
21370 @item SYMBOL_LOC_CONST
21371 Value is constant int.
21372 @findex SYMBOL_LOC_STATIC
21373 @findex gdb.SYMBOL_LOC_STATIC
21374 @item SYMBOL_LOC_STATIC
21375 Value is at a fixed address.
21376 @findex SYMBOL_LOC_REGISTER
21377 @findex gdb.SYMBOL_LOC_REGISTER
21378 @item SYMBOL_LOC_REGISTER
21379 Value is in a register.
21380 @findex SYMBOL_LOC_ARG
21381 @findex gdb.SYMBOL_LOC_ARG
21382 @item SYMBOL_LOC_ARG
21383 Value is an argument. This value is at the offset stored within the
21384 symbol inside the frame's argument list.
21385 @findex SYMBOL_LOC_REF_ARG
21386 @findex gdb.SYMBOL_LOC_REF_ARG
21387 @item SYMBOL_LOC_REF_ARG
21388 Value address is stored in the frame's argument list. Just like
21389 @code{LOC_ARG} except that the value's address is stored at the
21390 offset, not the value itself.
21391 @findex SYMBOL_LOC_REGPARM_ADDR
21392 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
21393 @item SYMBOL_LOC_REGPARM_ADDR
21394 Value is a specified register. Just like @code{LOC_REGISTER} except
21395 the register holds the address of the argument instead of the argument
21397 @findex SYMBOL_LOC_LOCAL
21398 @findex gdb.SYMBOL_LOC_LOCAL
21399 @item SYMBOL_LOC_LOCAL
21400 Value is a local variable.
21401 @findex SYMBOL_LOC_TYPEDEF
21402 @findex gdb.SYMBOL_LOC_TYPEDEF
21403 @item SYMBOL_LOC_TYPEDEF
21404 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
21406 @findex SYMBOL_LOC_BLOCK
21407 @findex gdb.SYMBOL_LOC_BLOCK
21408 @item SYMBOL_LOC_BLOCK
21410 @findex SYMBOL_LOC_CONST_BYTES
21411 @findex gdb.SYMBOL_LOC_CONST_BYTES
21412 @item SYMBOL_LOC_CONST_BYTES
21413 Value is a byte-sequence.
21414 @findex SYMBOL_LOC_UNRESOLVED
21415 @findex gdb.SYMBOL_LOC_UNRESOLVED
21416 @item SYMBOL_LOC_UNRESOLVED
21417 Value is at a fixed address, but the address of the variable has to be
21418 determined from the minimal symbol table whenever the variable is
21420 @findex SYMBOL_LOC_OPTIMIZED_OUT
21421 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
21422 @item SYMBOL_LOC_OPTIMIZED_OUT
21423 The value does not actually exist in the program.
21424 @findex SYMBOL_LOC_COMPUTED
21425 @findex gdb.SYMBOL_LOC_COMPUTED
21426 @item SYMBOL_LOC_COMPUTED
21427 The value's address is a computed location.
21430 @node Symbol Tables In Python
21431 @subsubsection Symbol table representation in Python.
21433 @cindex symbol tables in python
21435 @tindex gdb.Symtab_and_line
21437 Access to symbol table data maintained by @value{GDBN} on the inferior
21438 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
21439 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
21440 from the @code{find_sal} method in @code{gdb.Frame} object.
21441 @xref{Frames In Python}.
21443 For more information on @value{GDBN}'s symbol table management, see
21444 @ref{Symbols, ,Examining the Symbol Table}, for more information.
21446 A @code{gdb.Symtab_and_line} object has the following attributes:
21449 @defivar Symtab_and_line symtab
21450 The symbol table object (@code{gdb.Symtab}) for this frame.
21451 This attribute is not writable.
21454 @defivar Symtab_and_line pc
21455 Indicates the current program counter address. This attribute is not
21459 @defivar Symtab_and_line line
21460 Indicates the current line number for this object. This
21461 attribute is not writable.
21465 A @code{gdb.Symtab} object has the following attributes:
21468 @defivar Symtab filename
21469 The symbol table's source filename. This attribute is not writable.
21472 @defivar Symtab objfile
21473 The symbol table's backing object file. @xref{Objfiles In Python}.
21474 This attribute is not writable.
21478 The following methods are provided:
21481 @defmethod Symtab fullname
21482 Return the symbol table's source absolute file name.
21486 @node Breakpoints In Python
21487 @subsubsection Manipulating breakpoints using Python
21489 @cindex breakpoints in python
21490 @tindex gdb.Breakpoint
21492 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
21495 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]}
21496 Create a new breakpoint. @var{spec} is a string naming the
21497 location of the breakpoint, or an expression that defines a
21498 watchpoint. The contents can be any location recognized by the
21499 @code{break} command, or in the case of a watchpoint, by the @code{watch}
21500 command. The optional @var{type} denotes the breakpoint to create
21501 from the types defined later in this chapter. This argument can be
21502 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
21503 defaults to @code{BP_BREAKPOINT}. The optional @var{wp_class}
21504 argument defines the class of watchpoint to create, if @var{type} is
21505 defined as @code{BP_WATCHPOINT}. If a watchpoint class is not
21506 provided, it is assumed to be a @var{WP_WRITE} class.
21509 The available watchpoint types represented by constants are defined in the
21514 @findex gdb.WP_READ
21516 Read only watchpoint.
21519 @findex gdb.WP_WRITE
21521 Write only watchpoint.
21524 @findex gdb.WP_ACCESS
21526 Read/Write watchpoint.
21529 @defmethod Breakpoint is_valid
21530 Return @code{True} if this @code{Breakpoint} object is valid,
21531 @code{False} otherwise. A @code{Breakpoint} object can become invalid
21532 if the user deletes the breakpoint. In this case, the object still
21533 exists, but the underlying breakpoint does not. In the cases of
21534 watchpoint scope, the watchpoint remains valid even if execution of the
21535 inferior leaves the scope of that watchpoint.
21538 @defivar Breakpoint enabled
21539 This attribute is @code{True} if the breakpoint is enabled, and
21540 @code{False} otherwise. This attribute is writable.
21543 @defivar Breakpoint silent
21544 This attribute is @code{True} if the breakpoint is silent, and
21545 @code{False} otherwise. This attribute is writable.
21547 Note that a breakpoint can also be silent if it has commands and the
21548 first command is @code{silent}. This is not reported by the
21549 @code{silent} attribute.
21552 @defivar Breakpoint thread
21553 If the breakpoint is thread-specific, this attribute holds the thread
21554 id. If the breakpoint is not thread-specific, this attribute is
21555 @code{None}. This attribute is writable.
21558 @defivar Breakpoint task
21559 If the breakpoint is Ada task-specific, this attribute holds the Ada task
21560 id. If the breakpoint is not task-specific (or the underlying
21561 language is not Ada), this attribute is @code{None}. This attribute
21565 @defivar Breakpoint ignore_count
21566 This attribute holds the ignore count for the breakpoint, an integer.
21567 This attribute is writable.
21570 @defivar Breakpoint number
21571 This attribute holds the breakpoint's number --- the identifier used by
21572 the user to manipulate the breakpoint. This attribute is not writable.
21575 @defivar Breakpoint type
21576 This attribute holds the breakpoint's type --- the identifier used to
21577 determine the actual breakpoint type or use-case. This attribute is not
21581 The available types are represented by constants defined in the @code{gdb}
21585 @findex BP_BREAKPOINT
21586 @findex gdb.BP_BREAKPOINT
21587 @item BP_BREAKPOINT
21588 Normal code breakpoint.
21590 @findex BP_WATCHPOINT
21591 @findex gdb.BP_WATCHPOINT
21592 @item BP_WATCHPOINT
21593 Watchpoint breakpoint.
21595 @findex BP_HARDWARE_WATCHPOINT
21596 @findex gdb.BP_HARDWARE_WATCHPOINT
21597 @item BP_HARDWARE_WATCHPOINT
21598 Hardware assisted watchpoint.
21600 @findex BP_READ_WATCHPOINT
21601 @findex gdb.BP_READ_WATCHPOINT
21602 @item BP_READ_WATCHPOINT
21603 Hardware assisted read watchpoint.
21605 @findex BP_ACCESS_WATCHPOINT
21606 @findex gdb.BP_ACCESS_WATCHPOINT
21607 @item BP_ACCESS_WATCHPOINT
21608 Hardware assisted access watchpoint.
21611 @defivar Breakpoint hit_count
21612 This attribute holds the hit count for the breakpoint, an integer.
21613 This attribute is writable, but currently it can only be set to zero.
21616 @defivar Breakpoint location
21617 This attribute holds the location of the breakpoint, as specified by
21618 the user. It is a string. If the breakpoint does not have a location
21619 (that is, it is a watchpoint) the attribute's value is @code{None}. This
21620 attribute is not writable.
21623 @defivar Breakpoint expression
21624 This attribute holds a breakpoint expression, as specified by
21625 the user. It is a string. If the breakpoint does not have an
21626 expression (the breakpoint is not a watchpoint) the attribute's value
21627 is @code{None}. This attribute is not writable.
21630 @defivar Breakpoint condition
21631 This attribute holds the condition of the breakpoint, as specified by
21632 the user. It is a string. If there is no condition, this attribute's
21633 value is @code{None}. This attribute is writable.
21636 @defivar Breakpoint commands
21637 This attribute holds the commands attached to the breakpoint. If
21638 there are commands, this attribute's value is a string holding all the
21639 commands, separated by newlines. If there are no commands, this
21640 attribute is @code{None}. This attribute is not writable.
21643 @node Lazy Strings In Python
21644 @subsubsection Python representation of lazy strings.
21646 @cindex lazy strings in python
21647 @tindex gdb.LazyString
21649 A @dfn{lazy string} is a string whose contents is not retrieved or
21650 encoded until it is needed.
21652 A @code{gdb.LazyString} is represented in @value{GDBN} as an
21653 @code{address} that points to a region of memory, an @code{encoding}
21654 that will be used to encode that region of memory, and a @code{length}
21655 to delimit the region of memory that represents the string. The
21656 difference between a @code{gdb.LazyString} and a string wrapped within
21657 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
21658 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
21659 retrieved and encoded during printing, while a @code{gdb.Value}
21660 wrapping a string is immediately retrieved and encoded on creation.
21662 A @code{gdb.LazyString} object has the following functions:
21664 @defmethod LazyString value
21665 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
21666 will point to the string in memory, but will lose all the delayed
21667 retrieval, encoding and handling that @value{GDBN} applies to a
21668 @code{gdb.LazyString}.
21671 @defivar LazyString address
21672 This attribute holds the address of the string. This attribute is not
21676 @defivar LazyString length
21677 This attribute holds the length of the string in characters. If the
21678 length is -1, then the string will be fetched and encoded up to the
21679 first null of appropriate width. This attribute is not writable.
21682 @defivar LazyString encoding
21683 This attribute holds the encoding that will be applied to the string
21684 when the string is printed by @value{GDBN}. If the encoding is not
21685 set, or contains an empty string, then @value{GDBN} will select the
21686 most appropriate encoding when the string is printed. This attribute
21690 @defivar LazyString type
21691 This attribute holds the type that is represented by the lazy string's
21692 type. For a lazy string this will always be a pointer type. To
21693 resolve this to the lazy string's character type, use the type's
21694 @code{target} method. @xref{Types In Python}. This attribute is not
21699 @subsection Auto-loading
21700 @cindex auto-loading, Python
21702 When a new object file is read (for example, due to the @code{file}
21703 command, or because the inferior has loaded a shared library),
21704 @value{GDBN} will look for Python support scripts in several ways:
21705 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
21708 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
21709 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
21710 * Which flavor to choose?::
21713 The auto-loading feature is useful for supplying application-specific
21714 debugging commands and scripts.
21716 Auto-loading can be enabled or disabled.
21719 @kindex maint set python auto-load
21720 @item maint set python auto-load [yes|no]
21721 Enable or disable the Python auto-loading feature.
21723 @kindex maint show python auto-load
21724 @item maint show python auto-load
21725 Show whether Python auto-loading is enabled or disabled.
21728 When reading an auto-loaded file, @value{GDBN} sets the
21729 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
21730 function (@pxref{Objfiles In Python}). This can be useful for
21731 registering objfile-specific pretty-printers.
21733 @node objfile-gdb.py file
21734 @subsubsection The @file{@var{objfile}-gdb.py} file
21735 @cindex @file{@var{objfile}-gdb.py}
21737 When a new object file is read, @value{GDBN} looks for
21738 a file named @file{@var{objfile}-gdb.py},
21739 where @var{objfile} is the object file's real name, formed by ensuring
21740 that the file name is absolute, following all symlinks, and resolving
21741 @code{.} and @code{..} components. If this file exists and is
21742 readable, @value{GDBN} will evaluate it as a Python script.
21744 If this file does not exist, and if the parameter
21745 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
21746 then @value{GDBN} will look for @var{real-name} in all of the
21747 directories mentioned in the value of @code{debug-file-directory}.
21749 Finally, if this file does not exist, then @value{GDBN} will look for
21750 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
21751 @var{data-directory} is @value{GDBN}'s data directory (available via
21752 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
21753 is the object file's real name, as described above.
21755 @value{GDBN} does not track which files it has already auto-loaded this way.
21756 @value{GDBN} will load the associated script every time the corresponding
21757 @var{objfile} is opened.
21758 So your @file{-gdb.py} file should be careful to avoid errors if it
21759 is evaluated more than once.
21761 @node .debug_gdb_scripts section
21762 @subsubsection The @code{.debug_gdb_scripts} section
21763 @cindex @code{.debug_gdb_scripts} section
21765 For systems using file formats like ELF and COFF,
21766 when @value{GDBN} loads a new object file
21767 it will look for a special section named @samp{.debug_gdb_scripts}.
21768 If this section exists, its contents is a list of names of scripts to load.
21770 @value{GDBN} will look for each specified script file first in the
21771 current directory and then along the source search path
21772 (@pxref{Source Path, ,Specifying Source Directories}),
21773 except that @file{$cdir} is not searched, since the compilation
21774 directory is not relevant to scripts.
21776 Entries can be placed in section @code{.debug_gdb_scripts} with,
21777 for example, this GCC macro:
21780 /* Note: The "MS" section flags are to remote duplicates. */
21781 #define DEFINE_GDB_SCRIPT(script_name) \
21783 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
21785 .asciz \"" script_name "\"\n\
21791 Then one can reference the macro in a header or source file like this:
21794 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
21797 The script name may include directories if desired.
21799 If the macro is put in a header, any application or library
21800 using this header will get a reference to the specified script.
21802 @node Which flavor to choose?
21803 @subsubsection Which flavor to choose?
21805 Given the multiple ways of auto-loading Python scripts, it might not always
21806 be clear which one to choose. This section provides some guidance.
21808 Benefits of the @file{-gdb.py} way:
21812 Can be used with file formats that don't support multiple sections.
21815 Ease of finding scripts for public libraries.
21817 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
21818 in the source search path.
21819 For publicly installed libraries, e.g., @file{libstdc++}, there typically
21820 isn't a source directory in which to find the script.
21823 Doesn't require source code additions.
21826 Benefits of the @code{.debug_gdb_scripts} way:
21830 Works with static linking.
21832 Scripts for libraries done the @file{-gdb.py} way require an objfile to
21833 trigger their loading. When an application is statically linked the only
21834 objfile available is the executable, and it is cumbersome to attach all the
21835 scripts from all the input libraries to the executable's @file{-gdb.py} script.
21838 Works with classes that are entirely inlined.
21840 Some classes can be entirely inlined, and thus there may not be an associated
21841 shared library to attach a @file{-gdb.py} script to.
21844 Scripts needn't be copied out of the source tree.
21846 In some circumstances, apps can be built out of large collections of internal
21847 libraries, and the build infrastructure necessary to install the
21848 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
21849 cumbersome. It may be easier to specify the scripts in the
21850 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
21851 top of the source tree to the source search path.
21855 @chapter Command Interpreters
21856 @cindex command interpreters
21858 @value{GDBN} supports multiple command interpreters, and some command
21859 infrastructure to allow users or user interface writers to switch
21860 between interpreters or run commands in other interpreters.
21862 @value{GDBN} currently supports two command interpreters, the console
21863 interpreter (sometimes called the command-line interpreter or @sc{cli})
21864 and the machine interface interpreter (or @sc{gdb/mi}). This manual
21865 describes both of these interfaces in great detail.
21867 By default, @value{GDBN} will start with the console interpreter.
21868 However, the user may choose to start @value{GDBN} with another
21869 interpreter by specifying the @option{-i} or @option{--interpreter}
21870 startup options. Defined interpreters include:
21874 @cindex console interpreter
21875 The traditional console or command-line interpreter. This is the most often
21876 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
21877 @value{GDBN} will use this interpreter.
21880 @cindex mi interpreter
21881 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
21882 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
21883 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
21887 @cindex mi2 interpreter
21888 The current @sc{gdb/mi} interface.
21891 @cindex mi1 interpreter
21892 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
21896 @cindex invoke another interpreter
21897 The interpreter being used by @value{GDBN} may not be dynamically
21898 switched at runtime. Although possible, this could lead to a very
21899 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
21900 enters the command "interpreter-set console" in a console view,
21901 @value{GDBN} would switch to using the console interpreter, rendering
21902 the IDE inoperable!
21904 @kindex interpreter-exec
21905 Although you may only choose a single interpreter at startup, you may execute
21906 commands in any interpreter from the current interpreter using the appropriate
21907 command. If you are running the console interpreter, simply use the
21908 @code{interpreter-exec} command:
21911 interpreter-exec mi "-data-list-register-names"
21914 @sc{gdb/mi} has a similar command, although it is only available in versions of
21915 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
21918 @chapter @value{GDBN} Text User Interface
21920 @cindex Text User Interface
21923 * TUI Overview:: TUI overview
21924 * TUI Keys:: TUI key bindings
21925 * TUI Single Key Mode:: TUI single key mode
21926 * TUI Commands:: TUI-specific commands
21927 * TUI Configuration:: TUI configuration variables
21930 The @value{GDBN} Text User Interface (TUI) is a terminal
21931 interface which uses the @code{curses} library to show the source
21932 file, the assembly output, the program registers and @value{GDBN}
21933 commands in separate text windows. The TUI mode is supported only
21934 on platforms where a suitable version of the @code{curses} library
21937 @pindex @value{GDBTUI}
21938 The TUI mode is enabled by default when you invoke @value{GDBN} as
21939 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
21940 You can also switch in and out of TUI mode while @value{GDBN} runs by
21941 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
21942 @xref{TUI Keys, ,TUI Key Bindings}.
21945 @section TUI Overview
21947 In TUI mode, @value{GDBN} can display several text windows:
21951 This window is the @value{GDBN} command window with the @value{GDBN}
21952 prompt and the @value{GDBN} output. The @value{GDBN} input is still
21953 managed using readline.
21956 The source window shows the source file of the program. The current
21957 line and active breakpoints are displayed in this window.
21960 The assembly window shows the disassembly output of the program.
21963 This window shows the processor registers. Registers are highlighted
21964 when their values change.
21967 The source and assembly windows show the current program position
21968 by highlighting the current line and marking it with a @samp{>} marker.
21969 Breakpoints are indicated with two markers. The first marker
21970 indicates the breakpoint type:
21974 Breakpoint which was hit at least once.
21977 Breakpoint which was never hit.
21980 Hardware breakpoint which was hit at least once.
21983 Hardware breakpoint which was never hit.
21986 The second marker indicates whether the breakpoint is enabled or not:
21990 Breakpoint is enabled.
21993 Breakpoint is disabled.
21996 The source, assembly and register windows are updated when the current
21997 thread changes, when the frame changes, or when the program counter
22000 These windows are not all visible at the same time. The command
22001 window is always visible. The others can be arranged in several
22012 source and assembly,
22015 source and registers, or
22018 assembly and registers.
22021 A status line above the command window shows the following information:
22025 Indicates the current @value{GDBN} target.
22026 (@pxref{Targets, ,Specifying a Debugging Target}).
22029 Gives the current process or thread number.
22030 When no process is being debugged, this field is set to @code{No process}.
22033 Gives the current function name for the selected frame.
22034 The name is demangled if demangling is turned on (@pxref{Print Settings}).
22035 When there is no symbol corresponding to the current program counter,
22036 the string @code{??} is displayed.
22039 Indicates the current line number for the selected frame.
22040 When the current line number is not known, the string @code{??} is displayed.
22043 Indicates the current program counter address.
22047 @section TUI Key Bindings
22048 @cindex TUI key bindings
22050 The TUI installs several key bindings in the readline keymaps
22051 (@pxref{Command Line Editing}). The following key bindings
22052 are installed for both TUI mode and the @value{GDBN} standard mode.
22061 Enter or leave the TUI mode. When leaving the TUI mode,
22062 the curses window management stops and @value{GDBN} operates using
22063 its standard mode, writing on the terminal directly. When reentering
22064 the TUI mode, control is given back to the curses windows.
22065 The screen is then refreshed.
22069 Use a TUI layout with only one window. The layout will
22070 either be @samp{source} or @samp{assembly}. When the TUI mode
22071 is not active, it will switch to the TUI mode.
22073 Think of this key binding as the Emacs @kbd{C-x 1} binding.
22077 Use a TUI layout with at least two windows. When the current
22078 layout already has two windows, the next layout with two windows is used.
22079 When a new layout is chosen, one window will always be common to the
22080 previous layout and the new one.
22082 Think of it as the Emacs @kbd{C-x 2} binding.
22086 Change the active window. The TUI associates several key bindings
22087 (like scrolling and arrow keys) with the active window. This command
22088 gives the focus to the next TUI window.
22090 Think of it as the Emacs @kbd{C-x o} binding.
22094 Switch in and out of the TUI SingleKey mode that binds single
22095 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
22098 The following key bindings only work in the TUI mode:
22103 Scroll the active window one page up.
22107 Scroll the active window one page down.
22111 Scroll the active window one line up.
22115 Scroll the active window one line down.
22119 Scroll the active window one column left.
22123 Scroll the active window one column right.
22127 Refresh the screen.
22130 Because the arrow keys scroll the active window in the TUI mode, they
22131 are not available for their normal use by readline unless the command
22132 window has the focus. When another window is active, you must use
22133 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
22134 and @kbd{C-f} to control the command window.
22136 @node TUI Single Key Mode
22137 @section TUI Single Key Mode
22138 @cindex TUI single key mode
22140 The TUI also provides a @dfn{SingleKey} mode, which binds several
22141 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
22142 switch into this mode, where the following key bindings are used:
22145 @kindex c @r{(SingleKey TUI key)}
22149 @kindex d @r{(SingleKey TUI key)}
22153 @kindex f @r{(SingleKey TUI key)}
22157 @kindex n @r{(SingleKey TUI key)}
22161 @kindex q @r{(SingleKey TUI key)}
22163 exit the SingleKey mode.
22165 @kindex r @r{(SingleKey TUI key)}
22169 @kindex s @r{(SingleKey TUI key)}
22173 @kindex u @r{(SingleKey TUI key)}
22177 @kindex v @r{(SingleKey TUI key)}
22181 @kindex w @r{(SingleKey TUI key)}
22186 Other keys temporarily switch to the @value{GDBN} command prompt.
22187 The key that was pressed is inserted in the editing buffer so that
22188 it is possible to type most @value{GDBN} commands without interaction
22189 with the TUI SingleKey mode. Once the command is entered the TUI
22190 SingleKey mode is restored. The only way to permanently leave
22191 this mode is by typing @kbd{q} or @kbd{C-x s}.
22195 @section TUI-specific Commands
22196 @cindex TUI commands
22198 The TUI has specific commands to control the text windows.
22199 These commands are always available, even when @value{GDBN} is not in
22200 the TUI mode. When @value{GDBN} is in the standard mode, most
22201 of these commands will automatically switch to the TUI mode.
22203 Note that if @value{GDBN}'s @code{stdout} is not connected to a
22204 terminal, or @value{GDBN} has been started with the machine interface
22205 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
22206 these commands will fail with an error, because it would not be
22207 possible or desirable to enable curses window management.
22212 List and give the size of all displayed windows.
22216 Display the next layout.
22219 Display the previous layout.
22222 Display the source window only.
22225 Display the assembly window only.
22228 Display the source and assembly window.
22231 Display the register window together with the source or assembly window.
22235 Make the next window active for scrolling.
22238 Make the previous window active for scrolling.
22241 Make the source window active for scrolling.
22244 Make the assembly window active for scrolling.
22247 Make the register window active for scrolling.
22250 Make the command window active for scrolling.
22254 Refresh the screen. This is similar to typing @kbd{C-L}.
22256 @item tui reg float
22258 Show the floating point registers in the register window.
22260 @item tui reg general
22261 Show the general registers in the register window.
22264 Show the next register group. The list of register groups as well as
22265 their order is target specific. The predefined register groups are the
22266 following: @code{general}, @code{float}, @code{system}, @code{vector},
22267 @code{all}, @code{save}, @code{restore}.
22269 @item tui reg system
22270 Show the system registers in the register window.
22274 Update the source window and the current execution point.
22276 @item winheight @var{name} +@var{count}
22277 @itemx winheight @var{name} -@var{count}
22279 Change the height of the window @var{name} by @var{count}
22280 lines. Positive counts increase the height, while negative counts
22283 @item tabset @var{nchars}
22285 Set the width of tab stops to be @var{nchars} characters.
22288 @node TUI Configuration
22289 @section TUI Configuration Variables
22290 @cindex TUI configuration variables
22292 Several configuration variables control the appearance of TUI windows.
22295 @item set tui border-kind @var{kind}
22296 @kindex set tui border-kind
22297 Select the border appearance for the source, assembly and register windows.
22298 The possible values are the following:
22301 Use a space character to draw the border.
22304 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
22307 Use the Alternate Character Set to draw the border. The border is
22308 drawn using character line graphics if the terminal supports them.
22311 @item set tui border-mode @var{mode}
22312 @kindex set tui border-mode
22313 @itemx set tui active-border-mode @var{mode}
22314 @kindex set tui active-border-mode
22315 Select the display attributes for the borders of the inactive windows
22316 or the active window. The @var{mode} can be one of the following:
22319 Use normal attributes to display the border.
22325 Use reverse video mode.
22328 Use half bright mode.
22330 @item half-standout
22331 Use half bright and standout mode.
22334 Use extra bright or bold mode.
22336 @item bold-standout
22337 Use extra bright or bold and standout mode.
22342 @chapter Using @value{GDBN} under @sc{gnu} Emacs
22345 @cindex @sc{gnu} Emacs
22346 A special interface allows you to use @sc{gnu} Emacs to view (and
22347 edit) the source files for the program you are debugging with
22350 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
22351 executable file you want to debug as an argument. This command starts
22352 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
22353 created Emacs buffer.
22354 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
22356 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
22361 All ``terminal'' input and output goes through an Emacs buffer, called
22364 This applies both to @value{GDBN} commands and their output, and to the input
22365 and output done by the program you are debugging.
22367 This is useful because it means that you can copy the text of previous
22368 commands and input them again; you can even use parts of the output
22371 All the facilities of Emacs' Shell mode are available for interacting
22372 with your program. In particular, you can send signals the usual
22373 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
22377 @value{GDBN} displays source code through Emacs.
22379 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
22380 source file for that frame and puts an arrow (@samp{=>}) at the
22381 left margin of the current line. Emacs uses a separate buffer for
22382 source display, and splits the screen to show both your @value{GDBN} session
22385 Explicit @value{GDBN} @code{list} or search commands still produce output as
22386 usual, but you probably have no reason to use them from Emacs.
22389 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
22390 a graphical mode, enabled by default, which provides further buffers
22391 that can control the execution and describe the state of your program.
22392 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
22394 If you specify an absolute file name when prompted for the @kbd{M-x
22395 gdb} argument, then Emacs sets your current working directory to where
22396 your program resides. If you only specify the file name, then Emacs
22397 sets your current working directory to to the directory associated
22398 with the previous buffer. In this case, @value{GDBN} may find your
22399 program by searching your environment's @code{PATH} variable, but on
22400 some operating systems it might not find the source. So, although the
22401 @value{GDBN} input and output session proceeds normally, the auxiliary
22402 buffer does not display the current source and line of execution.
22404 The initial working directory of @value{GDBN} is printed on the top
22405 line of the GUD buffer and this serves as a default for the commands
22406 that specify files for @value{GDBN} to operate on. @xref{Files,
22407 ,Commands to Specify Files}.
22409 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
22410 need to call @value{GDBN} by a different name (for example, if you
22411 keep several configurations around, with different names) you can
22412 customize the Emacs variable @code{gud-gdb-command-name} to run the
22415 In the GUD buffer, you can use these special Emacs commands in
22416 addition to the standard Shell mode commands:
22420 Describe the features of Emacs' GUD Mode.
22423 Execute to another source line, like the @value{GDBN} @code{step} command; also
22424 update the display window to show the current file and location.
22427 Execute to next source line in this function, skipping all function
22428 calls, like the @value{GDBN} @code{next} command. Then update the display window
22429 to show the current file and location.
22432 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
22433 display window accordingly.
22436 Execute until exit from the selected stack frame, like the @value{GDBN}
22437 @code{finish} command.
22440 Continue execution of your program, like the @value{GDBN} @code{continue}
22444 Go up the number of frames indicated by the numeric argument
22445 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
22446 like the @value{GDBN} @code{up} command.
22449 Go down the number of frames indicated by the numeric argument, like the
22450 @value{GDBN} @code{down} command.
22453 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
22454 tells @value{GDBN} to set a breakpoint on the source line point is on.
22456 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
22457 separate frame which shows a backtrace when the GUD buffer is current.
22458 Move point to any frame in the stack and type @key{RET} to make it
22459 become the current frame and display the associated source in the
22460 source buffer. Alternatively, click @kbd{Mouse-2} to make the
22461 selected frame become the current one. In graphical mode, the
22462 speedbar displays watch expressions.
22464 If you accidentally delete the source-display buffer, an easy way to get
22465 it back is to type the command @code{f} in the @value{GDBN} buffer, to
22466 request a frame display; when you run under Emacs, this recreates
22467 the source buffer if necessary to show you the context of the current
22470 The source files displayed in Emacs are in ordinary Emacs buffers
22471 which are visiting the source files in the usual way. You can edit
22472 the files with these buffers if you wish; but keep in mind that @value{GDBN}
22473 communicates with Emacs in terms of line numbers. If you add or
22474 delete lines from the text, the line numbers that @value{GDBN} knows cease
22475 to correspond properly with the code.
22477 A more detailed description of Emacs' interaction with @value{GDBN} is
22478 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
22481 @c The following dropped because Epoch is nonstandard. Reactivate
22482 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
22484 @kindex Emacs Epoch environment
22488 Version 18 of @sc{gnu} Emacs has a built-in window system
22489 called the @code{epoch}
22490 environment. Users of this environment can use a new command,
22491 @code{inspect} which performs identically to @code{print} except that
22492 each value is printed in its own window.
22497 @chapter The @sc{gdb/mi} Interface
22499 @unnumberedsec Function and Purpose
22501 @cindex @sc{gdb/mi}, its purpose
22502 @sc{gdb/mi} is a line based machine oriented text interface to
22503 @value{GDBN} and is activated by specifying using the
22504 @option{--interpreter} command line option (@pxref{Mode Options}). It
22505 is specifically intended to support the development of systems which
22506 use the debugger as just one small component of a larger system.
22508 This chapter is a specification of the @sc{gdb/mi} interface. It is written
22509 in the form of a reference manual.
22511 Note that @sc{gdb/mi} is still under construction, so some of the
22512 features described below are incomplete and subject to change
22513 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
22515 @unnumberedsec Notation and Terminology
22517 @cindex notational conventions, for @sc{gdb/mi}
22518 This chapter uses the following notation:
22522 @code{|} separates two alternatives.
22525 @code{[ @var{something} ]} indicates that @var{something} is optional:
22526 it may or may not be given.
22529 @code{( @var{group} )*} means that @var{group} inside the parentheses
22530 may repeat zero or more times.
22533 @code{( @var{group} )+} means that @var{group} inside the parentheses
22534 may repeat one or more times.
22537 @code{"@var{string}"} means a literal @var{string}.
22541 @heading Dependencies
22545 * GDB/MI General Design::
22546 * GDB/MI Command Syntax::
22547 * GDB/MI Compatibility with CLI::
22548 * GDB/MI Development and Front Ends::
22549 * GDB/MI Output Records::
22550 * GDB/MI Simple Examples::
22551 * GDB/MI Command Description Format::
22552 * GDB/MI Breakpoint Commands::
22553 * GDB/MI Program Context::
22554 * GDB/MI Thread Commands::
22555 * GDB/MI Program Execution::
22556 * GDB/MI Stack Manipulation::
22557 * GDB/MI Variable Objects::
22558 * GDB/MI Data Manipulation::
22559 * GDB/MI Tracepoint Commands::
22560 * GDB/MI Symbol Query::
22561 * GDB/MI File Commands::
22563 * GDB/MI Kod Commands::
22564 * GDB/MI Memory Overlay Commands::
22565 * GDB/MI Signal Handling Commands::
22567 * GDB/MI Target Manipulation::
22568 * GDB/MI File Transfer Commands::
22569 * GDB/MI Miscellaneous Commands::
22572 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22573 @node GDB/MI General Design
22574 @section @sc{gdb/mi} General Design
22575 @cindex GDB/MI General Design
22577 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
22578 parts---commands sent to @value{GDBN}, responses to those commands
22579 and notifications. Each command results in exactly one response,
22580 indicating either successful completion of the command, or an error.
22581 For the commands that do not resume the target, the response contains the
22582 requested information. For the commands that resume the target, the
22583 response only indicates whether the target was successfully resumed.
22584 Notifications is the mechanism for reporting changes in the state of the
22585 target, or in @value{GDBN} state, that cannot conveniently be associated with
22586 a command and reported as part of that command response.
22588 The important examples of notifications are:
22592 Exec notifications. These are used to report changes in
22593 target state---when a target is resumed, or stopped. It would not
22594 be feasible to include this information in response of resuming
22595 commands, because one resume commands can result in multiple events in
22596 different threads. Also, quite some time may pass before any event
22597 happens in the target, while a frontend needs to know whether the resuming
22598 command itself was successfully executed.
22601 Console output, and status notifications. Console output
22602 notifications are used to report output of CLI commands, as well as
22603 diagnostics for other commands. Status notifications are used to
22604 report the progress of a long-running operation. Naturally, including
22605 this information in command response would mean no output is produced
22606 until the command is finished, which is undesirable.
22609 General notifications. Commands may have various side effects on
22610 the @value{GDBN} or target state beyond their official purpose. For example,
22611 a command may change the selected thread. Although such changes can
22612 be included in command response, using notification allows for more
22613 orthogonal frontend design.
22617 There's no guarantee that whenever an MI command reports an error,
22618 @value{GDBN} or the target are in any specific state, and especially,
22619 the state is not reverted to the state before the MI command was
22620 processed. Therefore, whenever an MI command results in an error,
22621 we recommend that the frontend refreshes all the information shown in
22622 the user interface.
22626 * Context management::
22627 * Asynchronous and non-stop modes::
22631 @node Context management
22632 @subsection Context management
22634 In most cases when @value{GDBN} accesses the target, this access is
22635 done in context of a specific thread and frame (@pxref{Frames}).
22636 Often, even when accessing global data, the target requires that a thread
22637 be specified. The CLI interface maintains the selected thread and frame,
22638 and supplies them to target on each command. This is convenient,
22639 because a command line user would not want to specify that information
22640 explicitly on each command, and because user interacts with
22641 @value{GDBN} via a single terminal, so no confusion is possible as
22642 to what thread and frame are the current ones.
22644 In the case of MI, the concept of selected thread and frame is less
22645 useful. First, a frontend can easily remember this information
22646 itself. Second, a graphical frontend can have more than one window,
22647 each one used for debugging a different thread, and the frontend might
22648 want to access additional threads for internal purposes. This
22649 increases the risk that by relying on implicitly selected thread, the
22650 frontend may be operating on a wrong one. Therefore, each MI command
22651 should explicitly specify which thread and frame to operate on. To
22652 make it possible, each MI command accepts the @samp{--thread} and
22653 @samp{--frame} options, the value to each is @value{GDBN} identifier
22654 for thread and frame to operate on.
22656 Usually, each top-level window in a frontend allows the user to select
22657 a thread and a frame, and remembers the user selection for further
22658 operations. However, in some cases @value{GDBN} may suggest that the
22659 current thread be changed. For example, when stopping on a breakpoint
22660 it is reasonable to switch to the thread where breakpoint is hit. For
22661 another example, if the user issues the CLI @samp{thread} command via
22662 the frontend, it is desirable to change the frontend's selected thread to the
22663 one specified by user. @value{GDBN} communicates the suggestion to
22664 change current thread using the @samp{=thread-selected} notification.
22665 No such notification is available for the selected frame at the moment.
22667 Note that historically, MI shares the selected thread with CLI, so
22668 frontends used the @code{-thread-select} to execute commands in the
22669 right context. However, getting this to work right is cumbersome. The
22670 simplest way is for frontend to emit @code{-thread-select} command
22671 before every command. This doubles the number of commands that need
22672 to be sent. The alternative approach is to suppress @code{-thread-select}
22673 if the selected thread in @value{GDBN} is supposed to be identical to the
22674 thread the frontend wants to operate on. However, getting this
22675 optimization right can be tricky. In particular, if the frontend
22676 sends several commands to @value{GDBN}, and one of the commands changes the
22677 selected thread, then the behaviour of subsequent commands will
22678 change. So, a frontend should either wait for response from such
22679 problematic commands, or explicitly add @code{-thread-select} for
22680 all subsequent commands. No frontend is known to do this exactly
22681 right, so it is suggested to just always pass the @samp{--thread} and
22682 @samp{--frame} options.
22684 @node Asynchronous and non-stop modes
22685 @subsection Asynchronous command execution and non-stop mode
22687 On some targets, @value{GDBN} is capable of processing MI commands
22688 even while the target is running. This is called @dfn{asynchronous
22689 command execution} (@pxref{Background Execution}). The frontend may
22690 specify a preferrence for asynchronous execution using the
22691 @code{-gdb-set target-async 1} command, which should be emitted before
22692 either running the executable or attaching to the target. After the
22693 frontend has started the executable or attached to the target, it can
22694 find if asynchronous execution is enabled using the
22695 @code{-list-target-features} command.
22697 Even if @value{GDBN} can accept a command while target is running,
22698 many commands that access the target do not work when the target is
22699 running. Therefore, asynchronous command execution is most useful
22700 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
22701 it is possible to examine the state of one thread, while other threads
22704 When a given thread is running, MI commands that try to access the
22705 target in the context of that thread may not work, or may work only on
22706 some targets. In particular, commands that try to operate on thread's
22707 stack will not work, on any target. Commands that read memory, or
22708 modify breakpoints, may work or not work, depending on the target. Note
22709 that even commands that operate on global state, such as @code{print},
22710 @code{set}, and breakpoint commands, still access the target in the
22711 context of a specific thread, so frontend should try to find a
22712 stopped thread and perform the operation on that thread (using the
22713 @samp{--thread} option).
22715 Which commands will work in the context of a running thread is
22716 highly target dependent. However, the two commands
22717 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
22718 to find the state of a thread, will always work.
22720 @node Thread groups
22721 @subsection Thread groups
22722 @value{GDBN} may be used to debug several processes at the same time.
22723 On some platfroms, @value{GDBN} may support debugging of several
22724 hardware systems, each one having several cores with several different
22725 processes running on each core. This section describes the MI
22726 mechanism to support such debugging scenarios.
22728 The key observation is that regardless of the structure of the
22729 target, MI can have a global list of threads, because most commands that
22730 accept the @samp{--thread} option do not need to know what process that
22731 thread belongs to. Therefore, it is not necessary to introduce
22732 neither additional @samp{--process} option, nor an notion of the
22733 current process in the MI interface. The only strictly new feature
22734 that is required is the ability to find how the threads are grouped
22737 To allow the user to discover such grouping, and to support arbitrary
22738 hierarchy of machines/cores/processes, MI introduces the concept of a
22739 @dfn{thread group}. Thread group is a collection of threads and other
22740 thread groups. A thread group always has a string identifier, a type,
22741 and may have additional attributes specific to the type. A new
22742 command, @code{-list-thread-groups}, returns the list of top-level
22743 thread groups, which correspond to processes that @value{GDBN} is
22744 debugging at the moment. By passing an identifier of a thread group
22745 to the @code{-list-thread-groups} command, it is possible to obtain
22746 the members of specific thread group.
22748 To allow the user to easily discover processes, and other objects, he
22749 wishes to debug, a concept of @dfn{available thread group} is
22750 introduced. Available thread group is an thread group that
22751 @value{GDBN} is not debugging, but that can be attached to, using the
22752 @code{-target-attach} command. The list of available top-level thread
22753 groups can be obtained using @samp{-list-thread-groups --available}.
22754 In general, the content of a thread group may be only retrieved only
22755 after attaching to that thread group.
22757 Thread groups are related to inferiors (@pxref{Inferiors and
22758 Programs}). Each inferior corresponds to a thread group of a special
22759 type @samp{process}, and some additional operations are permitted on
22760 such thread groups.
22762 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22763 @node GDB/MI Command Syntax
22764 @section @sc{gdb/mi} Command Syntax
22767 * GDB/MI Input Syntax::
22768 * GDB/MI Output Syntax::
22771 @node GDB/MI Input Syntax
22772 @subsection @sc{gdb/mi} Input Syntax
22774 @cindex input syntax for @sc{gdb/mi}
22775 @cindex @sc{gdb/mi}, input syntax
22777 @item @var{command} @expansion{}
22778 @code{@var{cli-command} | @var{mi-command}}
22780 @item @var{cli-command} @expansion{}
22781 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
22782 @var{cli-command} is any existing @value{GDBN} CLI command.
22784 @item @var{mi-command} @expansion{}
22785 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
22786 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
22788 @item @var{token} @expansion{}
22789 "any sequence of digits"
22791 @item @var{option} @expansion{}
22792 @code{"-" @var{parameter} [ " " @var{parameter} ]}
22794 @item @var{parameter} @expansion{}
22795 @code{@var{non-blank-sequence} | @var{c-string}}
22797 @item @var{operation} @expansion{}
22798 @emph{any of the operations described in this chapter}
22800 @item @var{non-blank-sequence} @expansion{}
22801 @emph{anything, provided it doesn't contain special characters such as
22802 "-", @var{nl}, """ and of course " "}
22804 @item @var{c-string} @expansion{}
22805 @code{""" @var{seven-bit-iso-c-string-content} """}
22807 @item @var{nl} @expansion{}
22816 The CLI commands are still handled by the @sc{mi} interpreter; their
22817 output is described below.
22820 The @code{@var{token}}, when present, is passed back when the command
22824 Some @sc{mi} commands accept optional arguments as part of the parameter
22825 list. Each option is identified by a leading @samp{-} (dash) and may be
22826 followed by an optional argument parameter. Options occur first in the
22827 parameter list and can be delimited from normal parameters using
22828 @samp{--} (this is useful when some parameters begin with a dash).
22835 We want easy access to the existing CLI syntax (for debugging).
22838 We want it to be easy to spot a @sc{mi} operation.
22841 @node GDB/MI Output Syntax
22842 @subsection @sc{gdb/mi} Output Syntax
22844 @cindex output syntax of @sc{gdb/mi}
22845 @cindex @sc{gdb/mi}, output syntax
22846 The output from @sc{gdb/mi} consists of zero or more out-of-band records
22847 followed, optionally, by a single result record. This result record
22848 is for the most recent command. The sequence of output records is
22849 terminated by @samp{(gdb)}.
22851 If an input command was prefixed with a @code{@var{token}} then the
22852 corresponding output for that command will also be prefixed by that same
22856 @item @var{output} @expansion{}
22857 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
22859 @item @var{result-record} @expansion{}
22860 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
22862 @item @var{out-of-band-record} @expansion{}
22863 @code{@var{async-record} | @var{stream-record}}
22865 @item @var{async-record} @expansion{}
22866 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
22868 @item @var{exec-async-output} @expansion{}
22869 @code{[ @var{token} ] "*" @var{async-output}}
22871 @item @var{status-async-output} @expansion{}
22872 @code{[ @var{token} ] "+" @var{async-output}}
22874 @item @var{notify-async-output} @expansion{}
22875 @code{[ @var{token} ] "=" @var{async-output}}
22877 @item @var{async-output} @expansion{}
22878 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
22880 @item @var{result-class} @expansion{}
22881 @code{"done" | "running" | "connected" | "error" | "exit"}
22883 @item @var{async-class} @expansion{}
22884 @code{"stopped" | @var{others}} (where @var{others} will be added
22885 depending on the needs---this is still in development).
22887 @item @var{result} @expansion{}
22888 @code{ @var{variable} "=" @var{value}}
22890 @item @var{variable} @expansion{}
22891 @code{ @var{string} }
22893 @item @var{value} @expansion{}
22894 @code{ @var{const} | @var{tuple} | @var{list} }
22896 @item @var{const} @expansion{}
22897 @code{@var{c-string}}
22899 @item @var{tuple} @expansion{}
22900 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
22902 @item @var{list} @expansion{}
22903 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
22904 @var{result} ( "," @var{result} )* "]" }
22906 @item @var{stream-record} @expansion{}
22907 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
22909 @item @var{console-stream-output} @expansion{}
22910 @code{"~" @var{c-string}}
22912 @item @var{target-stream-output} @expansion{}
22913 @code{"@@" @var{c-string}}
22915 @item @var{log-stream-output} @expansion{}
22916 @code{"&" @var{c-string}}
22918 @item @var{nl} @expansion{}
22921 @item @var{token} @expansion{}
22922 @emph{any sequence of digits}.
22930 All output sequences end in a single line containing a period.
22933 The @code{@var{token}} is from the corresponding request. Note that
22934 for all async output, while the token is allowed by the grammar and
22935 may be output by future versions of @value{GDBN} for select async
22936 output messages, it is generally omitted. Frontends should treat
22937 all async output as reporting general changes in the state of the
22938 target and there should be no need to associate async output to any
22942 @cindex status output in @sc{gdb/mi}
22943 @var{status-async-output} contains on-going status information about the
22944 progress of a slow operation. It can be discarded. All status output is
22945 prefixed by @samp{+}.
22948 @cindex async output in @sc{gdb/mi}
22949 @var{exec-async-output} contains asynchronous state change on the target
22950 (stopped, started, disappeared). All async output is prefixed by
22954 @cindex notify output in @sc{gdb/mi}
22955 @var{notify-async-output} contains supplementary information that the
22956 client should handle (e.g., a new breakpoint information). All notify
22957 output is prefixed by @samp{=}.
22960 @cindex console output in @sc{gdb/mi}
22961 @var{console-stream-output} is output that should be displayed as is in the
22962 console. It is the textual response to a CLI command. All the console
22963 output is prefixed by @samp{~}.
22966 @cindex target output in @sc{gdb/mi}
22967 @var{target-stream-output} is the output produced by the target program.
22968 All the target output is prefixed by @samp{@@}.
22971 @cindex log output in @sc{gdb/mi}
22972 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
22973 instance messages that should be displayed as part of an error log. All
22974 the log output is prefixed by @samp{&}.
22977 @cindex list output in @sc{gdb/mi}
22978 New @sc{gdb/mi} commands should only output @var{lists} containing
22984 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
22985 details about the various output records.
22987 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22988 @node GDB/MI Compatibility with CLI
22989 @section @sc{gdb/mi} Compatibility with CLI
22991 @cindex compatibility, @sc{gdb/mi} and CLI
22992 @cindex @sc{gdb/mi}, compatibility with CLI
22994 For the developers convenience CLI commands can be entered directly,
22995 but there may be some unexpected behaviour. For example, commands
22996 that query the user will behave as if the user replied yes, breakpoint
22997 command lists are not executed and some CLI commands, such as
22998 @code{if}, @code{when} and @code{define}, prompt for further input with
22999 @samp{>}, which is not valid MI output.
23001 This feature may be removed at some stage in the future and it is
23002 recommended that front ends use the @code{-interpreter-exec} command
23003 (@pxref{-interpreter-exec}).
23005 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23006 @node GDB/MI Development and Front Ends
23007 @section @sc{gdb/mi} Development and Front Ends
23008 @cindex @sc{gdb/mi} development
23010 The application which takes the MI output and presents the state of the
23011 program being debugged to the user is called a @dfn{front end}.
23013 Although @sc{gdb/mi} is still incomplete, it is currently being used
23014 by a variety of front ends to @value{GDBN}. This makes it difficult
23015 to introduce new functionality without breaking existing usage. This
23016 section tries to minimize the problems by describing how the protocol
23019 Some changes in MI need not break a carefully designed front end, and
23020 for these the MI version will remain unchanged. The following is a
23021 list of changes that may occur within one level, so front ends should
23022 parse MI output in a way that can handle them:
23026 New MI commands may be added.
23029 New fields may be added to the output of any MI command.
23032 The range of values for fields with specified values, e.g.,
23033 @code{in_scope} (@pxref{-var-update}) may be extended.
23035 @c The format of field's content e.g type prefix, may change so parse it
23036 @c at your own risk. Yes, in general?
23038 @c The order of fields may change? Shouldn't really matter but it might
23039 @c resolve inconsistencies.
23042 If the changes are likely to break front ends, the MI version level
23043 will be increased by one. This will allow the front end to parse the
23044 output according to the MI version. Apart from mi0, new versions of
23045 @value{GDBN} will not support old versions of MI and it will be the
23046 responsibility of the front end to work with the new one.
23048 @c Starting with mi3, add a new command -mi-version that prints the MI
23051 The best way to avoid unexpected changes in MI that might break your front
23052 end is to make your project known to @value{GDBN} developers and
23053 follow development on @email{gdb@@sourceware.org} and
23054 @email{gdb-patches@@sourceware.org}.
23055 @cindex mailing lists
23057 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23058 @node GDB/MI Output Records
23059 @section @sc{gdb/mi} Output Records
23062 * GDB/MI Result Records::
23063 * GDB/MI Stream Records::
23064 * GDB/MI Async Records::
23065 * GDB/MI Frame Information::
23066 * GDB/MI Thread Information::
23069 @node GDB/MI Result Records
23070 @subsection @sc{gdb/mi} Result Records
23072 @cindex result records in @sc{gdb/mi}
23073 @cindex @sc{gdb/mi}, result records
23074 In addition to a number of out-of-band notifications, the response to a
23075 @sc{gdb/mi} command includes one of the following result indications:
23079 @item "^done" [ "," @var{results} ]
23080 The synchronous operation was successful, @code{@var{results}} are the return
23085 This result record is equivalent to @samp{^done}. Historically, it
23086 was output instead of @samp{^done} if the command has resumed the
23087 target. This behaviour is maintained for backward compatibility, but
23088 all frontends should treat @samp{^done} and @samp{^running}
23089 identically and rely on the @samp{*running} output record to determine
23090 which threads are resumed.
23094 @value{GDBN} has connected to a remote target.
23096 @item "^error" "," @var{c-string}
23098 The operation failed. The @code{@var{c-string}} contains the corresponding
23103 @value{GDBN} has terminated.
23107 @node GDB/MI Stream Records
23108 @subsection @sc{gdb/mi} Stream Records
23110 @cindex @sc{gdb/mi}, stream records
23111 @cindex stream records in @sc{gdb/mi}
23112 @value{GDBN} internally maintains a number of output streams: the console, the
23113 target, and the log. The output intended for each of these streams is
23114 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
23116 Each stream record begins with a unique @dfn{prefix character} which
23117 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
23118 Syntax}). In addition to the prefix, each stream record contains a
23119 @code{@var{string-output}}. This is either raw text (with an implicit new
23120 line) or a quoted C string (which does not contain an implicit newline).
23123 @item "~" @var{string-output}
23124 The console output stream contains text that should be displayed in the
23125 CLI console window. It contains the textual responses to CLI commands.
23127 @item "@@" @var{string-output}
23128 The target output stream contains any textual output from the running
23129 target. This is only present when GDB's event loop is truly
23130 asynchronous, which is currently only the case for remote targets.
23132 @item "&" @var{string-output}
23133 The log stream contains debugging messages being produced by @value{GDBN}'s
23137 @node GDB/MI Async Records
23138 @subsection @sc{gdb/mi} Async Records
23140 @cindex async records in @sc{gdb/mi}
23141 @cindex @sc{gdb/mi}, async records
23142 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
23143 additional changes that have occurred. Those changes can either be a
23144 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
23145 target activity (e.g., target stopped).
23147 The following is the list of possible async records:
23151 @item *running,thread-id="@var{thread}"
23152 The target is now running. The @var{thread} field tells which
23153 specific thread is now running, and can be @samp{all} if all threads
23154 are running. The frontend should assume that no interaction with a
23155 running thread is possible after this notification is produced.
23156 The frontend should not assume that this notification is output
23157 only once for any command. @value{GDBN} may emit this notification
23158 several times, either for different threads, because it cannot resume
23159 all threads together, or even for a single thread, if the thread must
23160 be stepped though some code before letting it run freely.
23162 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
23163 The target has stopped. The @var{reason} field can have one of the
23167 @item breakpoint-hit
23168 A breakpoint was reached.
23169 @item watchpoint-trigger
23170 A watchpoint was triggered.
23171 @item read-watchpoint-trigger
23172 A read watchpoint was triggered.
23173 @item access-watchpoint-trigger
23174 An access watchpoint was triggered.
23175 @item function-finished
23176 An -exec-finish or similar CLI command was accomplished.
23177 @item location-reached
23178 An -exec-until or similar CLI command was accomplished.
23179 @item watchpoint-scope
23180 A watchpoint has gone out of scope.
23181 @item end-stepping-range
23182 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
23183 similar CLI command was accomplished.
23184 @item exited-signalled
23185 The inferior exited because of a signal.
23187 The inferior exited.
23188 @item exited-normally
23189 The inferior exited normally.
23190 @item signal-received
23191 A signal was received by the inferior.
23194 The @var{id} field identifies the thread that directly caused the stop
23195 -- for example by hitting a breakpoint. Depending on whether all-stop
23196 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
23197 stop all threads, or only the thread that directly triggered the stop.
23198 If all threads are stopped, the @var{stopped} field will have the
23199 value of @code{"all"}. Otherwise, the value of the @var{stopped}
23200 field will be a list of thread identifiers. Presently, this list will
23201 always include a single thread, but frontend should be prepared to see
23202 several threads in the list. The @var{core} field reports the
23203 processor core on which the stop event has happened. This field may be absent
23204 if such information is not available.
23206 @item =thread-group-added,id="@var{id}"
23207 @itemx =thread-group-removed,id="@var{id}"
23208 A thread group was either added or removed. The @var{id} field
23209 contains the @value{GDBN} identifier of the thread group. When a thread
23210 group is added, it generally might not be associated with a running
23211 process. When a thread group is removed, its id becomes invalid and
23212 cannot be used in any way.
23214 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
23215 A thread group became associated with a running program,
23216 either because the program was just started or the thread group
23217 was attached to a program. The @var{id} field contains the
23218 @value{GDBN} identifier of the thread group. The @var{pid} field
23219 contains process identifier, specific to the operating system.
23221 @itemx =thread-group-exited,id="@var{id}"
23222 A thread group is no longer associated with a running program,
23223 either because the program has exited, or because it was detached
23224 from. The @var{id} field contains the @value{GDBN} identifier of the
23227 @item =thread-created,id="@var{id}",group-id="@var{gid}"
23228 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
23229 A thread either was created, or has exited. The @var{id} field
23230 contains the @value{GDBN} identifier of the thread. The @var{gid}
23231 field identifies the thread group this thread belongs to.
23233 @item =thread-selected,id="@var{id}"
23234 Informs that the selected thread was changed as result of the last
23235 command. This notification is not emitted as result of @code{-thread-select}
23236 command but is emitted whenever an MI command that is not documented
23237 to change the selected thread actually changes it. In particular,
23238 invoking, directly or indirectly (via user-defined command), the CLI
23239 @code{thread} command, will generate this notification.
23241 We suggest that in response to this notification, front ends
23242 highlight the selected thread and cause subsequent commands to apply to
23245 @item =library-loaded,...
23246 Reports that a new library file was loaded by the program. This
23247 notification has 4 fields---@var{id}, @var{target-name},
23248 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
23249 opaque identifier of the library. For remote debugging case,
23250 @var{target-name} and @var{host-name} fields give the name of the
23251 library file on the target, and on the host respectively. For native
23252 debugging, both those fields have the same value. The
23253 @var{symbols-loaded} field reports if the debug symbols for this
23254 library are loaded. The @var{thread-group} field, if present,
23255 specifies the id of the thread group in whose context the library was loaded.
23256 If the field is absent, it means the library was loaded in the context
23257 of all present thread groups.
23259 @item =library-unloaded,...
23260 Reports that a library was unloaded by the program. This notification
23261 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
23262 the same meaning as for the @code{=library-loaded} notification.
23263 The @var{thread-group} field, if present, specifies the id of the
23264 thread group in whose context the library was unloaded. If the field is
23265 absent, it means the library was unloaded in the context of all present
23270 @node GDB/MI Frame Information
23271 @subsection @sc{gdb/mi} Frame Information
23273 Response from many MI commands includes an information about stack
23274 frame. This information is a tuple that may have the following
23279 The level of the stack frame. The innermost frame has the level of
23280 zero. This field is always present.
23283 The name of the function corresponding to the frame. This field may
23284 be absent if @value{GDBN} is unable to determine the function name.
23287 The code address for the frame. This field is always present.
23290 The name of the source files that correspond to the frame's code
23291 address. This field may be absent.
23294 The source line corresponding to the frames' code address. This field
23298 The name of the binary file (either executable or shared library) the
23299 corresponds to the frame's code address. This field may be absent.
23303 @node GDB/MI Thread Information
23304 @subsection @sc{gdb/mi} Thread Information
23306 Whenever @value{GDBN} has to report an information about a thread, it
23307 uses a tuple with the following fields:
23311 The numeric id assigned to the thread by @value{GDBN}. This field is
23315 Target-specific string identifying the thread. This field is always present.
23318 Additional information about the thread provided by the target.
23319 It is supposed to be human-readable and not interpreted by the
23320 frontend. This field is optional.
23323 Either @samp{stopped} or @samp{running}, depending on whether the
23324 thread is presently running. This field is always present.
23327 The value of this field is an integer number of the processor core the
23328 thread was last seen on. This field is optional.
23332 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23333 @node GDB/MI Simple Examples
23334 @section Simple Examples of @sc{gdb/mi} Interaction
23335 @cindex @sc{gdb/mi}, simple examples
23337 This subsection presents several simple examples of interaction using
23338 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
23339 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
23340 the output received from @sc{gdb/mi}.
23342 Note the line breaks shown in the examples are here only for
23343 readability, they don't appear in the real output.
23345 @subheading Setting a Breakpoint
23347 Setting a breakpoint generates synchronous output which contains detailed
23348 information of the breakpoint.
23351 -> -break-insert main
23352 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
23353 enabled="y",addr="0x08048564",func="main",file="myprog.c",
23354 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
23358 @subheading Program Execution
23360 Program execution generates asynchronous records and MI gives the
23361 reason that execution stopped.
23367 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
23368 frame=@{addr="0x08048564",func="main",
23369 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
23370 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
23375 <- *stopped,reason="exited-normally"
23379 @subheading Quitting @value{GDBN}
23381 Quitting @value{GDBN} just prints the result class @samp{^exit}.
23389 Please note that @samp{^exit} is printed immediately, but it might
23390 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
23391 performs necessary cleanups, including killing programs being debugged
23392 or disconnecting from debug hardware, so the frontend should wait till
23393 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
23394 fails to exit in reasonable time.
23396 @subheading A Bad Command
23398 Here's what happens if you pass a non-existent command:
23402 <- ^error,msg="Undefined MI command: rubbish"
23407 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23408 @node GDB/MI Command Description Format
23409 @section @sc{gdb/mi} Command Description Format
23411 The remaining sections describe blocks of commands. Each block of
23412 commands is laid out in a fashion similar to this section.
23414 @subheading Motivation
23416 The motivation for this collection of commands.
23418 @subheading Introduction
23420 A brief introduction to this collection of commands as a whole.
23422 @subheading Commands
23424 For each command in the block, the following is described:
23426 @subsubheading Synopsis
23429 -command @var{args}@dots{}
23432 @subsubheading Result
23434 @subsubheading @value{GDBN} Command
23436 The corresponding @value{GDBN} CLI command(s), if any.
23438 @subsubheading Example
23440 Example(s) formatted for readability. Some of the described commands have
23441 not been implemented yet and these are labeled N.A.@: (not available).
23444 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23445 @node GDB/MI Breakpoint Commands
23446 @section @sc{gdb/mi} Breakpoint Commands
23448 @cindex breakpoint commands for @sc{gdb/mi}
23449 @cindex @sc{gdb/mi}, breakpoint commands
23450 This section documents @sc{gdb/mi} commands for manipulating
23453 @subheading The @code{-break-after} Command
23454 @findex -break-after
23456 @subsubheading Synopsis
23459 -break-after @var{number} @var{count}
23462 The breakpoint number @var{number} is not in effect until it has been
23463 hit @var{count} times. To see how this is reflected in the output of
23464 the @samp{-break-list} command, see the description of the
23465 @samp{-break-list} command below.
23467 @subsubheading @value{GDBN} Command
23469 The corresponding @value{GDBN} command is @samp{ignore}.
23471 @subsubheading Example
23476 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
23477 enabled="y",addr="0x000100d0",func="main",file="hello.c",
23478 fullname="/home/foo/hello.c",line="5",times="0"@}
23485 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23486 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23487 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23488 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23489 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23490 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23491 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23492 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23493 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23494 line="5",times="0",ignore="3"@}]@}
23499 @subheading The @code{-break-catch} Command
23500 @findex -break-catch
23503 @subheading The @code{-break-commands} Command
23504 @findex -break-commands
23506 @subsubheading Synopsis
23509 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
23512 Specifies the CLI commands that should be executed when breakpoint
23513 @var{number} is hit. The parameters @var{command1} to @var{commandN}
23514 are the commands. If no command is specified, any previously-set
23515 commands are cleared. @xref{Break Commands}. Typical use of this
23516 functionality is tracing a program, that is, printing of values of
23517 some variables whenever breakpoint is hit and then continuing.
23519 @subsubheading @value{GDBN} Command
23521 The corresponding @value{GDBN} command is @samp{commands}.
23523 @subsubheading Example
23528 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
23529 enabled="y",addr="0x000100d0",func="main",file="hello.c",
23530 fullname="/home/foo/hello.c",line="5",times="0"@}
23532 -break-commands 1 "print v" "continue"
23537 @subheading The @code{-break-condition} Command
23538 @findex -break-condition
23540 @subsubheading Synopsis
23543 -break-condition @var{number} @var{expr}
23546 Breakpoint @var{number} will stop the program only if the condition in
23547 @var{expr} is true. The condition becomes part of the
23548 @samp{-break-list} output (see the description of the @samp{-break-list}
23551 @subsubheading @value{GDBN} Command
23553 The corresponding @value{GDBN} command is @samp{condition}.
23555 @subsubheading Example
23559 -break-condition 1 1
23563 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23564 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23565 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23566 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23567 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23568 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23569 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23570 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23571 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23572 line="5",cond="1",times="0",ignore="3"@}]@}
23576 @subheading The @code{-break-delete} Command
23577 @findex -break-delete
23579 @subsubheading Synopsis
23582 -break-delete ( @var{breakpoint} )+
23585 Delete the breakpoint(s) whose number(s) are specified in the argument
23586 list. This is obviously reflected in the breakpoint list.
23588 @subsubheading @value{GDBN} Command
23590 The corresponding @value{GDBN} command is @samp{delete}.
23592 @subsubheading Example
23600 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
23601 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23602 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23603 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23604 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23605 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23606 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23611 @subheading The @code{-break-disable} Command
23612 @findex -break-disable
23614 @subsubheading Synopsis
23617 -break-disable ( @var{breakpoint} )+
23620 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
23621 break list is now set to @samp{n} for the named @var{breakpoint}(s).
23623 @subsubheading @value{GDBN} Command
23625 The corresponding @value{GDBN} command is @samp{disable}.
23627 @subsubheading Example
23635 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23636 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23637 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23638 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23639 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23640 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23641 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23642 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
23643 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23644 line="5",times="0"@}]@}
23648 @subheading The @code{-break-enable} Command
23649 @findex -break-enable
23651 @subsubheading Synopsis
23654 -break-enable ( @var{breakpoint} )+
23657 Enable (previously disabled) @var{breakpoint}(s).
23659 @subsubheading @value{GDBN} Command
23661 The corresponding @value{GDBN} command is @samp{enable}.
23663 @subsubheading Example
23671 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23672 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23673 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23674 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23675 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23676 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23677 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23678 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
23679 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23680 line="5",times="0"@}]@}
23684 @subheading The @code{-break-info} Command
23685 @findex -break-info
23687 @subsubheading Synopsis
23690 -break-info @var{breakpoint}
23694 Get information about a single breakpoint.
23696 @subsubheading @value{GDBN} Command
23698 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
23700 @subsubheading Example
23703 @subheading The @code{-break-insert} Command
23704 @findex -break-insert
23706 @subsubheading Synopsis
23709 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
23710 [ -c @var{condition} ] [ -i @var{ignore-count} ]
23711 [ -p @var{thread} ] [ @var{location} ]
23715 If specified, @var{location}, can be one of:
23722 @item filename:linenum
23723 @item filename:function
23727 The possible optional parameters of this command are:
23731 Insert a temporary breakpoint.
23733 Insert a hardware breakpoint.
23734 @item -c @var{condition}
23735 Make the breakpoint conditional on @var{condition}.
23736 @item -i @var{ignore-count}
23737 Initialize the @var{ignore-count}.
23739 If @var{location} cannot be parsed (for example if it
23740 refers to unknown files or functions), create a pending
23741 breakpoint. Without this flag, @value{GDBN} will report
23742 an error, and won't create a breakpoint, if @var{location}
23745 Create a disabled breakpoint.
23747 Create a tracepoint. @xref{Tracepoints}. When this parameter
23748 is used together with @samp{-h}, a fast tracepoint is created.
23751 @subsubheading Result
23753 The result is in the form:
23756 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
23757 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
23758 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
23759 times="@var{times}"@}
23763 where @var{number} is the @value{GDBN} number for this breakpoint,
23764 @var{funcname} is the name of the function where the breakpoint was
23765 inserted, @var{filename} is the name of the source file which contains
23766 this function, @var{lineno} is the source line number within that file
23767 and @var{times} the number of times that the breakpoint has been hit
23768 (always 0 for -break-insert but may be greater for -break-info or -break-list
23769 which use the same output).
23771 Note: this format is open to change.
23772 @c An out-of-band breakpoint instead of part of the result?
23774 @subsubheading @value{GDBN} Command
23776 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
23777 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
23779 @subsubheading Example
23784 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
23785 fullname="/home/foo/recursive2.c,line="4",times="0"@}
23787 -break-insert -t foo
23788 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
23789 fullname="/home/foo/recursive2.c,line="11",times="0"@}
23792 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23793 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23794 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23795 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23796 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23797 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23798 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23799 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23800 addr="0x0001072c", func="main",file="recursive2.c",
23801 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
23802 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
23803 addr="0x00010774",func="foo",file="recursive2.c",
23804 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
23806 -break-insert -r foo.*
23807 ~int foo(int, int);
23808 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
23809 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
23813 @subheading The @code{-break-list} Command
23814 @findex -break-list
23816 @subsubheading Synopsis
23822 Displays the list of inserted breakpoints, showing the following fields:
23826 number of the breakpoint
23828 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
23830 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
23833 is the breakpoint enabled or no: @samp{y} or @samp{n}
23835 memory location at which the breakpoint is set
23837 logical location of the breakpoint, expressed by function name, file
23840 number of times the breakpoint has been hit
23843 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
23844 @code{body} field is an empty list.
23846 @subsubheading @value{GDBN} Command
23848 The corresponding @value{GDBN} command is @samp{info break}.
23850 @subsubheading Example
23855 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23856 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23857 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23858 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23859 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23860 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23861 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23862 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23863 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
23864 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
23865 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
23866 line="13",times="0"@}]@}
23870 Here's an example of the result when there are no breakpoints:
23875 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
23876 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23877 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23878 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23879 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23880 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23881 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23886 @subheading The @code{-break-passcount} Command
23887 @findex -break-passcount
23889 @subsubheading Synopsis
23892 -break-passcount @var{tracepoint-number} @var{passcount}
23895 Set the passcount for tracepoint @var{tracepoint-number} to
23896 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
23897 is not a tracepoint, error is emitted. This corresponds to CLI
23898 command @samp{passcount}.
23900 @subheading The @code{-break-watch} Command
23901 @findex -break-watch
23903 @subsubheading Synopsis
23906 -break-watch [ -a | -r ]
23909 Create a watchpoint. With the @samp{-a} option it will create an
23910 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
23911 read from or on a write to the memory location. With the @samp{-r}
23912 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
23913 trigger only when the memory location is accessed for reading. Without
23914 either of the options, the watchpoint created is a regular watchpoint,
23915 i.e., it will trigger when the memory location is accessed for writing.
23916 @xref{Set Watchpoints, , Setting Watchpoints}.
23918 Note that @samp{-break-list} will report a single list of watchpoints and
23919 breakpoints inserted.
23921 @subsubheading @value{GDBN} Command
23923 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
23926 @subsubheading Example
23928 Setting a watchpoint on a variable in the @code{main} function:
23933 ^done,wpt=@{number="2",exp="x"@}
23938 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
23939 value=@{old="-268439212",new="55"@},
23940 frame=@{func="main",args=[],file="recursive2.c",
23941 fullname="/home/foo/bar/recursive2.c",line="5"@}
23945 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
23946 the program execution twice: first for the variable changing value, then
23947 for the watchpoint going out of scope.
23952 ^done,wpt=@{number="5",exp="C"@}
23957 *stopped,reason="watchpoint-trigger",
23958 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
23959 frame=@{func="callee4",args=[],
23960 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23961 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
23966 *stopped,reason="watchpoint-scope",wpnum="5",
23967 frame=@{func="callee3",args=[@{name="strarg",
23968 value="0x11940 \"A string argument.\""@}],
23969 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23970 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
23974 Listing breakpoints and watchpoints, at different points in the program
23975 execution. Note that once the watchpoint goes out of scope, it is
23981 ^done,wpt=@{number="2",exp="C"@}
23984 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23985 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23986 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23987 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23988 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23989 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23990 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23991 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23992 addr="0x00010734",func="callee4",
23993 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23994 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
23995 bkpt=@{number="2",type="watchpoint",disp="keep",
23996 enabled="y",addr="",what="C",times="0"@}]@}
24001 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
24002 value=@{old="-276895068",new="3"@},
24003 frame=@{func="callee4",args=[],
24004 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24005 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24008 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24009 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24010 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24011 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24012 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24013 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24014 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24015 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24016 addr="0x00010734",func="callee4",
24017 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24018 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
24019 bkpt=@{number="2",type="watchpoint",disp="keep",
24020 enabled="y",addr="",what="C",times="-5"@}]@}
24024 ^done,reason="watchpoint-scope",wpnum="2",
24025 frame=@{func="callee3",args=[@{name="strarg",
24026 value="0x11940 \"A string argument.\""@}],
24027 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24028 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24031 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24032 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24033 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24034 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24035 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24036 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24037 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24038 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24039 addr="0x00010734",func="callee4",
24040 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24041 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
24046 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24047 @node GDB/MI Program Context
24048 @section @sc{gdb/mi} Program Context
24050 @subheading The @code{-exec-arguments} Command
24051 @findex -exec-arguments
24054 @subsubheading Synopsis
24057 -exec-arguments @var{args}
24060 Set the inferior program arguments, to be used in the next
24063 @subsubheading @value{GDBN} Command
24065 The corresponding @value{GDBN} command is @samp{set args}.
24067 @subsubheading Example
24071 -exec-arguments -v word
24078 @subheading The @code{-exec-show-arguments} Command
24079 @findex -exec-show-arguments
24081 @subsubheading Synopsis
24084 -exec-show-arguments
24087 Print the arguments of the program.
24089 @subsubheading @value{GDBN} Command
24091 The corresponding @value{GDBN} command is @samp{show args}.
24093 @subsubheading Example
24098 @subheading The @code{-environment-cd} Command
24099 @findex -environment-cd
24101 @subsubheading Synopsis
24104 -environment-cd @var{pathdir}
24107 Set @value{GDBN}'s working directory.
24109 @subsubheading @value{GDBN} Command
24111 The corresponding @value{GDBN} command is @samp{cd}.
24113 @subsubheading Example
24117 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
24123 @subheading The @code{-environment-directory} Command
24124 @findex -environment-directory
24126 @subsubheading Synopsis
24129 -environment-directory [ -r ] [ @var{pathdir} ]+
24132 Add directories @var{pathdir} to beginning of search path for source files.
24133 If the @samp{-r} option is used, the search path is reset to the default
24134 search path. If directories @var{pathdir} are supplied in addition to the
24135 @samp{-r} option, the search path is first reset and then addition
24137 Multiple directories may be specified, separated by blanks. Specifying
24138 multiple directories in a single command
24139 results in the directories added to the beginning of the
24140 search path in the same order they were presented in the command.
24141 If blanks are needed as
24142 part of a directory name, double-quotes should be used around
24143 the name. In the command output, the path will show up separated
24144 by the system directory-separator character. The directory-separator
24145 character must not be used
24146 in any directory name.
24147 If no directories are specified, the current search path is displayed.
24149 @subsubheading @value{GDBN} Command
24151 The corresponding @value{GDBN} command is @samp{dir}.
24153 @subsubheading Example
24157 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
24158 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
24160 -environment-directory ""
24161 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
24163 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
24164 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
24166 -environment-directory -r
24167 ^done,source-path="$cdir:$cwd"
24172 @subheading The @code{-environment-path} Command
24173 @findex -environment-path
24175 @subsubheading Synopsis
24178 -environment-path [ -r ] [ @var{pathdir} ]+
24181 Add directories @var{pathdir} to beginning of search path for object files.
24182 If the @samp{-r} option is used, the search path is reset to the original
24183 search path that existed at gdb start-up. If directories @var{pathdir} are
24184 supplied in addition to the
24185 @samp{-r} option, the search path is first reset and then addition
24187 Multiple directories may be specified, separated by blanks. Specifying
24188 multiple directories in a single command
24189 results in the directories added to the beginning of the
24190 search path in the same order they were presented in the command.
24191 If blanks are needed as
24192 part of a directory name, double-quotes should be used around
24193 the name. In the command output, the path will show up separated
24194 by the system directory-separator character. The directory-separator
24195 character must not be used
24196 in any directory name.
24197 If no directories are specified, the current path is displayed.
24200 @subsubheading @value{GDBN} Command
24202 The corresponding @value{GDBN} command is @samp{path}.
24204 @subsubheading Example
24209 ^done,path="/usr/bin"
24211 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
24212 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
24214 -environment-path -r /usr/local/bin
24215 ^done,path="/usr/local/bin:/usr/bin"
24220 @subheading The @code{-environment-pwd} Command
24221 @findex -environment-pwd
24223 @subsubheading Synopsis
24229 Show the current working directory.
24231 @subsubheading @value{GDBN} Command
24233 The corresponding @value{GDBN} command is @samp{pwd}.
24235 @subsubheading Example
24240 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
24244 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24245 @node GDB/MI Thread Commands
24246 @section @sc{gdb/mi} Thread Commands
24249 @subheading The @code{-thread-info} Command
24250 @findex -thread-info
24252 @subsubheading Synopsis
24255 -thread-info [ @var{thread-id} ]
24258 Reports information about either a specific thread, if
24259 the @var{thread-id} parameter is present, or about all
24260 threads. When printing information about all threads,
24261 also reports the current thread.
24263 @subsubheading @value{GDBN} Command
24265 The @samp{info thread} command prints the same information
24268 @subsubheading Example
24273 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
24274 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
24275 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
24276 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
24277 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
24278 current-thread-id="1"
24282 The @samp{state} field may have the following values:
24286 The thread is stopped. Frame information is available for stopped
24290 The thread is running. There's no frame information for running
24295 @subheading The @code{-thread-list-ids} Command
24296 @findex -thread-list-ids
24298 @subsubheading Synopsis
24304 Produces a list of the currently known @value{GDBN} thread ids. At the
24305 end of the list it also prints the total number of such threads.
24307 This command is retained for historical reasons, the
24308 @code{-thread-info} command should be used instead.
24310 @subsubheading @value{GDBN} Command
24312 Part of @samp{info threads} supplies the same information.
24314 @subsubheading Example
24319 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
24320 current-thread-id="1",number-of-threads="3"
24325 @subheading The @code{-thread-select} Command
24326 @findex -thread-select
24328 @subsubheading Synopsis
24331 -thread-select @var{threadnum}
24334 Make @var{threadnum} the current thread. It prints the number of the new
24335 current thread, and the topmost frame for that thread.
24337 This command is deprecated in favor of explicitly using the
24338 @samp{--thread} option to each command.
24340 @subsubheading @value{GDBN} Command
24342 The corresponding @value{GDBN} command is @samp{thread}.
24344 @subsubheading Example
24351 *stopped,reason="end-stepping-range",thread-id="2",line="187",
24352 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
24356 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
24357 number-of-threads="3"
24360 ^done,new-thread-id="3",
24361 frame=@{level="0",func="vprintf",
24362 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
24363 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
24367 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24368 @node GDB/MI Program Execution
24369 @section @sc{gdb/mi} Program Execution
24371 These are the asynchronous commands which generate the out-of-band
24372 record @samp{*stopped}. Currently @value{GDBN} only really executes
24373 asynchronously with remote targets and this interaction is mimicked in
24376 @subheading The @code{-exec-continue} Command
24377 @findex -exec-continue
24379 @subsubheading Synopsis
24382 -exec-continue [--reverse] [--all|--thread-group N]
24385 Resumes the execution of the inferior program, which will continue
24386 to execute until it reaches a debugger stop event. If the
24387 @samp{--reverse} option is specified, execution resumes in reverse until
24388 it reaches a stop event. Stop events may include
24391 breakpoints or watchpoints
24393 signals or exceptions
24395 the end of the process (or its beginning under @samp{--reverse})
24397 the end or beginning of a replay log if one is being used.
24399 In all-stop mode (@pxref{All-Stop
24400 Mode}), may resume only one thread, or all threads, depending on the
24401 value of the @samp{scheduler-locking} variable. If @samp{--all} is
24402 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
24403 ignored in all-stop mode. If the @samp{--thread-group} options is
24404 specified, then all threads in that thread group are resumed.
24406 @subsubheading @value{GDBN} Command
24408 The corresponding @value{GDBN} corresponding is @samp{continue}.
24410 @subsubheading Example
24417 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
24418 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
24424 @subheading The @code{-exec-finish} Command
24425 @findex -exec-finish
24427 @subsubheading Synopsis
24430 -exec-finish [--reverse]
24433 Resumes the execution of the inferior program until the current
24434 function is exited. Displays the results returned by the function.
24435 If the @samp{--reverse} option is specified, resumes the reverse
24436 execution of the inferior program until the point where current
24437 function was called.
24439 @subsubheading @value{GDBN} Command
24441 The corresponding @value{GDBN} command is @samp{finish}.
24443 @subsubheading Example
24445 Function returning @code{void}.
24452 *stopped,reason="function-finished",frame=@{func="main",args=[],
24453 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
24457 Function returning other than @code{void}. The name of the internal
24458 @value{GDBN} variable storing the result is printed, together with the
24465 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
24466 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
24467 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24468 gdb-result-var="$1",return-value="0"
24473 @subheading The @code{-exec-interrupt} Command
24474 @findex -exec-interrupt
24476 @subsubheading Synopsis
24479 -exec-interrupt [--all|--thread-group N]
24482 Interrupts the background execution of the target. Note how the token
24483 associated with the stop message is the one for the execution command
24484 that has been interrupted. The token for the interrupt itself only
24485 appears in the @samp{^done} output. If the user is trying to
24486 interrupt a non-running program, an error message will be printed.
24488 Note that when asynchronous execution is enabled, this command is
24489 asynchronous just like other execution commands. That is, first the
24490 @samp{^done} response will be printed, and the target stop will be
24491 reported after that using the @samp{*stopped} notification.
24493 In non-stop mode, only the context thread is interrupted by default.
24494 All threads (in all inferiors) will be interrupted if the
24495 @samp{--all} option is specified. If the @samp{--thread-group}
24496 option is specified, all threads in that group will be interrupted.
24498 @subsubheading @value{GDBN} Command
24500 The corresponding @value{GDBN} command is @samp{interrupt}.
24502 @subsubheading Example
24513 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
24514 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
24515 fullname="/home/foo/bar/try.c",line="13"@}
24520 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
24524 @subheading The @code{-exec-jump} Command
24527 @subsubheading Synopsis
24530 -exec-jump @var{location}
24533 Resumes execution of the inferior program at the location specified by
24534 parameter. @xref{Specify Location}, for a description of the
24535 different forms of @var{location}.
24537 @subsubheading @value{GDBN} Command
24539 The corresponding @value{GDBN} command is @samp{jump}.
24541 @subsubheading Example
24544 -exec-jump foo.c:10
24545 *running,thread-id="all"
24550 @subheading The @code{-exec-next} Command
24553 @subsubheading Synopsis
24556 -exec-next [--reverse]
24559 Resumes execution of the inferior program, stopping when the beginning
24560 of the next source line is reached.
24562 If the @samp{--reverse} option is specified, resumes reverse execution
24563 of the inferior program, stopping at the beginning of the previous
24564 source line. If you issue this command on the first line of a
24565 function, it will take you back to the caller of that function, to the
24566 source line where the function was called.
24569 @subsubheading @value{GDBN} Command
24571 The corresponding @value{GDBN} command is @samp{next}.
24573 @subsubheading Example
24579 *stopped,reason="end-stepping-range",line="8",file="hello.c"
24584 @subheading The @code{-exec-next-instruction} Command
24585 @findex -exec-next-instruction
24587 @subsubheading Synopsis
24590 -exec-next-instruction [--reverse]
24593 Executes one machine instruction. If the instruction is a function
24594 call, continues until the function returns. If the program stops at an
24595 instruction in the middle of a source line, the address will be
24598 If the @samp{--reverse} option is specified, resumes reverse execution
24599 of the inferior program, stopping at the previous instruction. If the
24600 previously executed instruction was a return from another function,
24601 it will continue to execute in reverse until the call to that function
24602 (from the current stack frame) is reached.
24604 @subsubheading @value{GDBN} Command
24606 The corresponding @value{GDBN} command is @samp{nexti}.
24608 @subsubheading Example
24612 -exec-next-instruction
24616 *stopped,reason="end-stepping-range",
24617 addr="0x000100d4",line="5",file="hello.c"
24622 @subheading The @code{-exec-return} Command
24623 @findex -exec-return
24625 @subsubheading Synopsis
24631 Makes current function return immediately. Doesn't execute the inferior.
24632 Displays the new current frame.
24634 @subsubheading @value{GDBN} Command
24636 The corresponding @value{GDBN} command is @samp{return}.
24638 @subsubheading Example
24642 200-break-insert callee4
24643 200^done,bkpt=@{number="1",addr="0x00010734",
24644 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
24649 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
24650 frame=@{func="callee4",args=[],
24651 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24652 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
24658 111^done,frame=@{level="0",func="callee3",
24659 args=[@{name="strarg",
24660 value="0x11940 \"A string argument.\""@}],
24661 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24662 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24667 @subheading The @code{-exec-run} Command
24670 @subsubheading Synopsis
24673 -exec-run [--all | --thread-group N]
24676 Starts execution of the inferior from the beginning. The inferior
24677 executes until either a breakpoint is encountered or the program
24678 exits. In the latter case the output will include an exit code, if
24679 the program has exited exceptionally.
24681 When no option is specified, the current inferior is started. If the
24682 @samp{--thread-group} option is specified, it should refer to a thread
24683 group of type @samp{process}, and that thread group will be started.
24684 If the @samp{--all} option is specified, then all inferiors will be started.
24686 @subsubheading @value{GDBN} Command
24688 The corresponding @value{GDBN} command is @samp{run}.
24690 @subsubheading Examples
24695 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
24700 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
24701 frame=@{func="main",args=[],file="recursive2.c",
24702 fullname="/home/foo/bar/recursive2.c",line="4"@}
24707 Program exited normally:
24715 *stopped,reason="exited-normally"
24720 Program exited exceptionally:
24728 *stopped,reason="exited",exit-code="01"
24732 Another way the program can terminate is if it receives a signal such as
24733 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
24737 *stopped,reason="exited-signalled",signal-name="SIGINT",
24738 signal-meaning="Interrupt"
24742 @c @subheading -exec-signal
24745 @subheading The @code{-exec-step} Command
24748 @subsubheading Synopsis
24751 -exec-step [--reverse]
24754 Resumes execution of the inferior program, stopping when the beginning
24755 of the next source line is reached, if the next source line is not a
24756 function call. If it is, stop at the first instruction of the called
24757 function. If the @samp{--reverse} option is specified, resumes reverse
24758 execution of the inferior program, stopping at the beginning of the
24759 previously executed source line.
24761 @subsubheading @value{GDBN} Command
24763 The corresponding @value{GDBN} command is @samp{step}.
24765 @subsubheading Example
24767 Stepping into a function:
24773 *stopped,reason="end-stepping-range",
24774 frame=@{func="foo",args=[@{name="a",value="10"@},
24775 @{name="b",value="0"@}],file="recursive2.c",
24776 fullname="/home/foo/bar/recursive2.c",line="11"@}
24786 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
24791 @subheading The @code{-exec-step-instruction} Command
24792 @findex -exec-step-instruction
24794 @subsubheading Synopsis
24797 -exec-step-instruction [--reverse]
24800 Resumes the inferior which executes one machine instruction. If the
24801 @samp{--reverse} option is specified, resumes reverse execution of the
24802 inferior program, stopping at the previously executed instruction.
24803 The output, once @value{GDBN} has stopped, will vary depending on
24804 whether we have stopped in the middle of a source line or not. In the
24805 former case, the address at which the program stopped will be printed
24808 @subsubheading @value{GDBN} Command
24810 The corresponding @value{GDBN} command is @samp{stepi}.
24812 @subsubheading Example
24816 -exec-step-instruction
24820 *stopped,reason="end-stepping-range",
24821 frame=@{func="foo",args=[],file="try.c",
24822 fullname="/home/foo/bar/try.c",line="10"@}
24824 -exec-step-instruction
24828 *stopped,reason="end-stepping-range",
24829 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
24830 fullname="/home/foo/bar/try.c",line="10"@}
24835 @subheading The @code{-exec-until} Command
24836 @findex -exec-until
24838 @subsubheading Synopsis
24841 -exec-until [ @var{location} ]
24844 Executes the inferior until the @var{location} specified in the
24845 argument is reached. If there is no argument, the inferior executes
24846 until a source line greater than the current one is reached. The
24847 reason for stopping in this case will be @samp{location-reached}.
24849 @subsubheading @value{GDBN} Command
24851 The corresponding @value{GDBN} command is @samp{until}.
24853 @subsubheading Example
24857 -exec-until recursive2.c:6
24861 *stopped,reason="location-reached",frame=@{func="main",args=[],
24862 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
24867 @subheading -file-clear
24868 Is this going away????
24871 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24872 @node GDB/MI Stack Manipulation
24873 @section @sc{gdb/mi} Stack Manipulation Commands
24876 @subheading The @code{-stack-info-frame} Command
24877 @findex -stack-info-frame
24879 @subsubheading Synopsis
24885 Get info on the selected frame.
24887 @subsubheading @value{GDBN} Command
24889 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
24890 (without arguments).
24892 @subsubheading Example
24897 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
24898 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24899 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
24903 @subheading The @code{-stack-info-depth} Command
24904 @findex -stack-info-depth
24906 @subsubheading Synopsis
24909 -stack-info-depth [ @var{max-depth} ]
24912 Return the depth of the stack. If the integer argument @var{max-depth}
24913 is specified, do not count beyond @var{max-depth} frames.
24915 @subsubheading @value{GDBN} Command
24917 There's no equivalent @value{GDBN} command.
24919 @subsubheading Example
24921 For a stack with frame levels 0 through 11:
24928 -stack-info-depth 4
24931 -stack-info-depth 12
24934 -stack-info-depth 11
24937 -stack-info-depth 13
24942 @subheading The @code{-stack-list-arguments} Command
24943 @findex -stack-list-arguments
24945 @subsubheading Synopsis
24948 -stack-list-arguments @var{print-values}
24949 [ @var{low-frame} @var{high-frame} ]
24952 Display a list of the arguments for the frames between @var{low-frame}
24953 and @var{high-frame} (inclusive). If @var{low-frame} and
24954 @var{high-frame} are not provided, list the arguments for the whole
24955 call stack. If the two arguments are equal, show the single frame
24956 at the corresponding level. It is an error if @var{low-frame} is
24957 larger than the actual number of frames. On the other hand,
24958 @var{high-frame} may be larger than the actual number of frames, in
24959 which case only existing frames will be returned.
24961 If @var{print-values} is 0 or @code{--no-values}, print only the names of
24962 the variables; if it is 1 or @code{--all-values}, print also their
24963 values; and if it is 2 or @code{--simple-values}, print the name,
24964 type and value for simple data types, and the name and type for arrays,
24965 structures and unions.
24967 Use of this command to obtain arguments in a single frame is
24968 deprecated in favor of the @samp{-stack-list-variables} command.
24970 @subsubheading @value{GDBN} Command
24972 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
24973 @samp{gdb_get_args} command which partially overlaps with the
24974 functionality of @samp{-stack-list-arguments}.
24976 @subsubheading Example
24983 frame=@{level="0",addr="0x00010734",func="callee4",
24984 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24985 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
24986 frame=@{level="1",addr="0x0001076c",func="callee3",
24987 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24988 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
24989 frame=@{level="2",addr="0x0001078c",func="callee2",
24990 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24991 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
24992 frame=@{level="3",addr="0x000107b4",func="callee1",
24993 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24994 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
24995 frame=@{level="4",addr="0x000107e0",func="main",
24996 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24997 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
24999 -stack-list-arguments 0
25002 frame=@{level="0",args=[]@},
25003 frame=@{level="1",args=[name="strarg"]@},
25004 frame=@{level="2",args=[name="intarg",name="strarg"]@},
25005 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
25006 frame=@{level="4",args=[]@}]
25008 -stack-list-arguments 1
25011 frame=@{level="0",args=[]@},
25013 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25014 frame=@{level="2",args=[
25015 @{name="intarg",value="2"@},
25016 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25017 @{frame=@{level="3",args=[
25018 @{name="intarg",value="2"@},
25019 @{name="strarg",value="0x11940 \"A string argument.\""@},
25020 @{name="fltarg",value="3.5"@}]@},
25021 frame=@{level="4",args=[]@}]
25023 -stack-list-arguments 0 2 2
25024 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
25026 -stack-list-arguments 1 2 2
25027 ^done,stack-args=[frame=@{level="2",
25028 args=[@{name="intarg",value="2"@},
25029 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
25033 @c @subheading -stack-list-exception-handlers
25036 @subheading The @code{-stack-list-frames} Command
25037 @findex -stack-list-frames
25039 @subsubheading Synopsis
25042 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
25045 List the frames currently on the stack. For each frame it displays the
25050 The frame number, 0 being the topmost frame, i.e., the innermost function.
25052 The @code{$pc} value for that frame.
25056 File name of the source file where the function lives.
25058 Line number corresponding to the @code{$pc}.
25061 If invoked without arguments, this command prints a backtrace for the
25062 whole stack. If given two integer arguments, it shows the frames whose
25063 levels are between the two arguments (inclusive). If the two arguments
25064 are equal, it shows the single frame at the corresponding level. It is
25065 an error if @var{low-frame} is larger than the actual number of
25066 frames. On the other hand, @var{high-frame} may be larger than the
25067 actual number of frames, in which case only existing frames will be returned.
25069 @subsubheading @value{GDBN} Command
25071 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
25073 @subsubheading Example
25075 Full stack backtrace:
25081 [frame=@{level="0",addr="0x0001076c",func="foo",
25082 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
25083 frame=@{level="1",addr="0x000107a4",func="foo",
25084 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25085 frame=@{level="2",addr="0x000107a4",func="foo",
25086 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25087 frame=@{level="3",addr="0x000107a4",func="foo",
25088 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25089 frame=@{level="4",addr="0x000107a4",func="foo",
25090 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25091 frame=@{level="5",addr="0x000107a4",func="foo",
25092 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25093 frame=@{level="6",addr="0x000107a4",func="foo",
25094 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25095 frame=@{level="7",addr="0x000107a4",func="foo",
25096 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25097 frame=@{level="8",addr="0x000107a4",func="foo",
25098 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25099 frame=@{level="9",addr="0x000107a4",func="foo",
25100 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25101 frame=@{level="10",addr="0x000107a4",func="foo",
25102 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25103 frame=@{level="11",addr="0x00010738",func="main",
25104 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
25108 Show frames between @var{low_frame} and @var{high_frame}:
25112 -stack-list-frames 3 5
25114 [frame=@{level="3",addr="0x000107a4",func="foo",
25115 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25116 frame=@{level="4",addr="0x000107a4",func="foo",
25117 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25118 frame=@{level="5",addr="0x000107a4",func="foo",
25119 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
25123 Show a single frame:
25127 -stack-list-frames 3 3
25129 [frame=@{level="3",addr="0x000107a4",func="foo",
25130 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
25135 @subheading The @code{-stack-list-locals} Command
25136 @findex -stack-list-locals
25138 @subsubheading Synopsis
25141 -stack-list-locals @var{print-values}
25144 Display the local variable names for the selected frame. If
25145 @var{print-values} is 0 or @code{--no-values}, print only the names of
25146 the variables; if it is 1 or @code{--all-values}, print also their
25147 values; and if it is 2 or @code{--simple-values}, print the name,
25148 type and value for simple data types, and the name and type for arrays,
25149 structures and unions. In this last case, a frontend can immediately
25150 display the value of simple data types and create variable objects for
25151 other data types when the user wishes to explore their values in
25154 This command is deprecated in favor of the
25155 @samp{-stack-list-variables} command.
25157 @subsubheading @value{GDBN} Command
25159 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
25161 @subsubheading Example
25165 -stack-list-locals 0
25166 ^done,locals=[name="A",name="B",name="C"]
25168 -stack-list-locals --all-values
25169 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
25170 @{name="C",value="@{1, 2, 3@}"@}]
25171 -stack-list-locals --simple-values
25172 ^done,locals=[@{name="A",type="int",value="1"@},
25173 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
25177 @subheading The @code{-stack-list-variables} Command
25178 @findex -stack-list-variables
25180 @subsubheading Synopsis
25183 -stack-list-variables @var{print-values}
25186 Display the names of local variables and function arguments for the selected frame. If
25187 @var{print-values} is 0 or @code{--no-values}, print only the names of
25188 the variables; if it is 1 or @code{--all-values}, print also their
25189 values; and if it is 2 or @code{--simple-values}, print the name,
25190 type and value for simple data types, and the name and type for arrays,
25191 structures and unions.
25193 @subsubheading Example
25197 -stack-list-variables --thread 1 --frame 0 --all-values
25198 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
25203 @subheading The @code{-stack-select-frame} Command
25204 @findex -stack-select-frame
25206 @subsubheading Synopsis
25209 -stack-select-frame @var{framenum}
25212 Change the selected frame. Select a different frame @var{framenum} on
25215 This command in deprecated in favor of passing the @samp{--frame}
25216 option to every command.
25218 @subsubheading @value{GDBN} Command
25220 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
25221 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
25223 @subsubheading Example
25227 -stack-select-frame 2
25232 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25233 @node GDB/MI Variable Objects
25234 @section @sc{gdb/mi} Variable Objects
25238 @subheading Motivation for Variable Objects in @sc{gdb/mi}
25240 For the implementation of a variable debugger window (locals, watched
25241 expressions, etc.), we are proposing the adaptation of the existing code
25242 used by @code{Insight}.
25244 The two main reasons for that are:
25248 It has been proven in practice (it is already on its second generation).
25251 It will shorten development time (needless to say how important it is
25255 The original interface was designed to be used by Tcl code, so it was
25256 slightly changed so it could be used through @sc{gdb/mi}. This section
25257 describes the @sc{gdb/mi} operations that will be available and gives some
25258 hints about their use.
25260 @emph{Note}: In addition to the set of operations described here, we
25261 expect the @sc{gui} implementation of a variable window to require, at
25262 least, the following operations:
25265 @item @code{-gdb-show} @code{output-radix}
25266 @item @code{-stack-list-arguments}
25267 @item @code{-stack-list-locals}
25268 @item @code{-stack-select-frame}
25273 @subheading Introduction to Variable Objects
25275 @cindex variable objects in @sc{gdb/mi}
25277 Variable objects are "object-oriented" MI interface for examining and
25278 changing values of expressions. Unlike some other MI interfaces that
25279 work with expressions, variable objects are specifically designed for
25280 simple and efficient presentation in the frontend. A variable object
25281 is identified by string name. When a variable object is created, the
25282 frontend specifies the expression for that variable object. The
25283 expression can be a simple variable, or it can be an arbitrary complex
25284 expression, and can even involve CPU registers. After creating a
25285 variable object, the frontend can invoke other variable object
25286 operations---for example to obtain or change the value of a variable
25287 object, or to change display format.
25289 Variable objects have hierarchical tree structure. Any variable object
25290 that corresponds to a composite type, such as structure in C, has
25291 a number of child variable objects, for example corresponding to each
25292 element of a structure. A child variable object can itself have
25293 children, recursively. Recursion ends when we reach
25294 leaf variable objects, which always have built-in types. Child variable
25295 objects are created only by explicit request, so if a frontend
25296 is not interested in the children of a particular variable object, no
25297 child will be created.
25299 For a leaf variable object it is possible to obtain its value as a
25300 string, or set the value from a string. String value can be also
25301 obtained for a non-leaf variable object, but it's generally a string
25302 that only indicates the type of the object, and does not list its
25303 contents. Assignment to a non-leaf variable object is not allowed.
25305 A frontend does not need to read the values of all variable objects each time
25306 the program stops. Instead, MI provides an update command that lists all
25307 variable objects whose values has changed since the last update
25308 operation. This considerably reduces the amount of data that must
25309 be transferred to the frontend. As noted above, children variable
25310 objects are created on demand, and only leaf variable objects have a
25311 real value. As result, gdb will read target memory only for leaf
25312 variables that frontend has created.
25314 The automatic update is not always desirable. For example, a frontend
25315 might want to keep a value of some expression for future reference,
25316 and never update it. For another example, fetching memory is
25317 relatively slow for embedded targets, so a frontend might want
25318 to disable automatic update for the variables that are either not
25319 visible on the screen, or ``closed''. This is possible using so
25320 called ``frozen variable objects''. Such variable objects are never
25321 implicitly updated.
25323 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
25324 fixed variable object, the expression is parsed when the variable
25325 object is created, including associating identifiers to specific
25326 variables. The meaning of expression never changes. For a floating
25327 variable object the values of variables whose names appear in the
25328 expressions are re-evaluated every time in the context of the current
25329 frame. Consider this example:
25334 struct work_state state;
25341 If a fixed variable object for the @code{state} variable is created in
25342 this function, and we enter the recursive call, the the variable
25343 object will report the value of @code{state} in the top-level
25344 @code{do_work} invocation. On the other hand, a floating variable
25345 object will report the value of @code{state} in the current frame.
25347 If an expression specified when creating a fixed variable object
25348 refers to a local variable, the variable object becomes bound to the
25349 thread and frame in which the variable object is created. When such
25350 variable object is updated, @value{GDBN} makes sure that the
25351 thread/frame combination the variable object is bound to still exists,
25352 and re-evaluates the variable object in context of that thread/frame.
25354 The following is the complete set of @sc{gdb/mi} operations defined to
25355 access this functionality:
25357 @multitable @columnfractions .4 .6
25358 @item @strong{Operation}
25359 @tab @strong{Description}
25361 @item @code{-enable-pretty-printing}
25362 @tab enable Python-based pretty-printing
25363 @item @code{-var-create}
25364 @tab create a variable object
25365 @item @code{-var-delete}
25366 @tab delete the variable object and/or its children
25367 @item @code{-var-set-format}
25368 @tab set the display format of this variable
25369 @item @code{-var-show-format}
25370 @tab show the display format of this variable
25371 @item @code{-var-info-num-children}
25372 @tab tells how many children this object has
25373 @item @code{-var-list-children}
25374 @tab return a list of the object's children
25375 @item @code{-var-info-type}
25376 @tab show the type of this variable object
25377 @item @code{-var-info-expression}
25378 @tab print parent-relative expression that this variable object represents
25379 @item @code{-var-info-path-expression}
25380 @tab print full expression that this variable object represents
25381 @item @code{-var-show-attributes}
25382 @tab is this variable editable? does it exist here?
25383 @item @code{-var-evaluate-expression}
25384 @tab get the value of this variable
25385 @item @code{-var-assign}
25386 @tab set the value of this variable
25387 @item @code{-var-update}
25388 @tab update the variable and its children
25389 @item @code{-var-set-frozen}
25390 @tab set frozeness attribute
25391 @item @code{-var-set-update-range}
25392 @tab set range of children to display on update
25395 In the next subsection we describe each operation in detail and suggest
25396 how it can be used.
25398 @subheading Description And Use of Operations on Variable Objects
25400 @subheading The @code{-enable-pretty-printing} Command
25401 @findex -enable-pretty-printing
25404 -enable-pretty-printing
25407 @value{GDBN} allows Python-based visualizers to affect the output of the
25408 MI variable object commands. However, because there was no way to
25409 implement this in a fully backward-compatible way, a front end must
25410 request that this functionality be enabled.
25412 Once enabled, this feature cannot be disabled.
25414 Note that if Python support has not been compiled into @value{GDBN},
25415 this command will still succeed (and do nothing).
25417 This feature is currently (as of @value{GDBN} 7.0) experimental, and
25418 may work differently in future versions of @value{GDBN}.
25420 @subheading The @code{-var-create} Command
25421 @findex -var-create
25423 @subsubheading Synopsis
25426 -var-create @{@var{name} | "-"@}
25427 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
25430 This operation creates a variable object, which allows the monitoring of
25431 a variable, the result of an expression, a memory cell or a CPU
25434 The @var{name} parameter is the string by which the object can be
25435 referenced. It must be unique. If @samp{-} is specified, the varobj
25436 system will generate a string ``varNNNNNN'' automatically. It will be
25437 unique provided that one does not specify @var{name} of that format.
25438 The command fails if a duplicate name is found.
25440 The frame under which the expression should be evaluated can be
25441 specified by @var{frame-addr}. A @samp{*} indicates that the current
25442 frame should be used. A @samp{@@} indicates that a floating variable
25443 object must be created.
25445 @var{expression} is any expression valid on the current language set (must not
25446 begin with a @samp{*}), or one of the following:
25450 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
25453 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
25456 @samp{$@var{regname}} --- a CPU register name
25459 @cindex dynamic varobj
25460 A varobj's contents may be provided by a Python-based pretty-printer. In this
25461 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
25462 have slightly different semantics in some cases. If the
25463 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
25464 will never create a dynamic varobj. This ensures backward
25465 compatibility for existing clients.
25467 @subsubheading Result
25469 This operation returns attributes of the newly-created varobj. These
25474 The name of the varobj.
25477 The number of children of the varobj. This number is not necessarily
25478 reliable for a dynamic varobj. Instead, you must examine the
25479 @samp{has_more} attribute.
25482 The varobj's scalar value. For a varobj whose type is some sort of
25483 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
25484 will not be interesting.
25487 The varobj's type. This is a string representation of the type, as
25488 would be printed by the @value{GDBN} CLI.
25491 If a variable object is bound to a specific thread, then this is the
25492 thread's identifier.
25495 For a dynamic varobj, this indicates whether there appear to be any
25496 children available. For a non-dynamic varobj, this will be 0.
25499 This attribute will be present and have the value @samp{1} if the
25500 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
25501 then this attribute will not be present.
25504 A dynamic varobj can supply a display hint to the front end. The
25505 value comes directly from the Python pretty-printer object's
25506 @code{display_hint} method. @xref{Pretty Printing API}.
25509 Typical output will look like this:
25512 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
25513 has_more="@var{has_more}"
25517 @subheading The @code{-var-delete} Command
25518 @findex -var-delete
25520 @subsubheading Synopsis
25523 -var-delete [ -c ] @var{name}
25526 Deletes a previously created variable object and all of its children.
25527 With the @samp{-c} option, just deletes the children.
25529 Returns an error if the object @var{name} is not found.
25532 @subheading The @code{-var-set-format} Command
25533 @findex -var-set-format
25535 @subsubheading Synopsis
25538 -var-set-format @var{name} @var{format-spec}
25541 Sets the output format for the value of the object @var{name} to be
25544 @anchor{-var-set-format}
25545 The syntax for the @var{format-spec} is as follows:
25548 @var{format-spec} @expansion{}
25549 @{binary | decimal | hexadecimal | octal | natural@}
25552 The natural format is the default format choosen automatically
25553 based on the variable type (like decimal for an @code{int}, hex
25554 for pointers, etc.).
25556 For a variable with children, the format is set only on the
25557 variable itself, and the children are not affected.
25559 @subheading The @code{-var-show-format} Command
25560 @findex -var-show-format
25562 @subsubheading Synopsis
25565 -var-show-format @var{name}
25568 Returns the format used to display the value of the object @var{name}.
25571 @var{format} @expansion{}
25576 @subheading The @code{-var-info-num-children} Command
25577 @findex -var-info-num-children
25579 @subsubheading Synopsis
25582 -var-info-num-children @var{name}
25585 Returns the number of children of a variable object @var{name}:
25591 Note that this number is not completely reliable for a dynamic varobj.
25592 It will return the current number of children, but more children may
25596 @subheading The @code{-var-list-children} Command
25597 @findex -var-list-children
25599 @subsubheading Synopsis
25602 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
25604 @anchor{-var-list-children}
25606 Return a list of the children of the specified variable object and
25607 create variable objects for them, if they do not already exist. With
25608 a single argument or if @var{print-values} has a value for of 0 or
25609 @code{--no-values}, print only the names of the variables; if
25610 @var{print-values} is 1 or @code{--all-values}, also print their
25611 values; and if it is 2 or @code{--simple-values} print the name and
25612 value for simple data types and just the name for arrays, structures
25615 @var{from} and @var{to}, if specified, indicate the range of children
25616 to report. If @var{from} or @var{to} is less than zero, the range is
25617 reset and all children will be reported. Otherwise, children starting
25618 at @var{from} (zero-based) and up to and excluding @var{to} will be
25621 If a child range is requested, it will only affect the current call to
25622 @code{-var-list-children}, but not future calls to @code{-var-update}.
25623 For this, you must instead use @code{-var-set-update-range}. The
25624 intent of this approach is to enable a front end to implement any
25625 update approach it likes; for example, scrolling a view may cause the
25626 front end to request more children with @code{-var-list-children}, and
25627 then the front end could call @code{-var-set-update-range} with a
25628 different range to ensure that future updates are restricted to just
25631 For each child the following results are returned:
25636 Name of the variable object created for this child.
25639 The expression to be shown to the user by the front end to designate this child.
25640 For example this may be the name of a structure member.
25642 For a dynamic varobj, this value cannot be used to form an
25643 expression. There is no way to do this at all with a dynamic varobj.
25645 For C/C@t{++} structures there are several pseudo children returned to
25646 designate access qualifiers. For these pseudo children @var{exp} is
25647 @samp{public}, @samp{private}, or @samp{protected}. In this case the
25648 type and value are not present.
25650 A dynamic varobj will not report the access qualifying
25651 pseudo-children, regardless of the language. This information is not
25652 available at all with a dynamic varobj.
25655 Number of children this child has. For a dynamic varobj, this will be
25659 The type of the child.
25662 If values were requested, this is the value.
25665 If this variable object is associated with a thread, this is the thread id.
25666 Otherwise this result is not present.
25669 If the variable object is frozen, this variable will be present with a value of 1.
25672 The result may have its own attributes:
25676 A dynamic varobj can supply a display hint to the front end. The
25677 value comes directly from the Python pretty-printer object's
25678 @code{display_hint} method. @xref{Pretty Printing API}.
25681 This is an integer attribute which is nonzero if there are children
25682 remaining after the end of the selected range.
25685 @subsubheading Example
25689 -var-list-children n
25690 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
25691 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
25693 -var-list-children --all-values n
25694 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
25695 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
25699 @subheading The @code{-var-info-type} Command
25700 @findex -var-info-type
25702 @subsubheading Synopsis
25705 -var-info-type @var{name}
25708 Returns the type of the specified variable @var{name}. The type is
25709 returned as a string in the same format as it is output by the
25713 type=@var{typename}
25717 @subheading The @code{-var-info-expression} Command
25718 @findex -var-info-expression
25720 @subsubheading Synopsis
25723 -var-info-expression @var{name}
25726 Returns a string that is suitable for presenting this
25727 variable object in user interface. The string is generally
25728 not valid expression in the current language, and cannot be evaluated.
25730 For example, if @code{a} is an array, and variable object
25731 @code{A} was created for @code{a}, then we'll get this output:
25734 (gdb) -var-info-expression A.1
25735 ^done,lang="C",exp="1"
25739 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
25741 Note that the output of the @code{-var-list-children} command also
25742 includes those expressions, so the @code{-var-info-expression} command
25745 @subheading The @code{-var-info-path-expression} Command
25746 @findex -var-info-path-expression
25748 @subsubheading Synopsis
25751 -var-info-path-expression @var{name}
25754 Returns an expression that can be evaluated in the current
25755 context and will yield the same value that a variable object has.
25756 Compare this with the @code{-var-info-expression} command, which
25757 result can be used only for UI presentation. Typical use of
25758 the @code{-var-info-path-expression} command is creating a
25759 watchpoint from a variable object.
25761 This command is currently not valid for children of a dynamic varobj,
25762 and will give an error when invoked on one.
25764 For example, suppose @code{C} is a C@t{++} class, derived from class
25765 @code{Base}, and that the @code{Base} class has a member called
25766 @code{m_size}. Assume a variable @code{c} is has the type of
25767 @code{C} and a variable object @code{C} was created for variable
25768 @code{c}. Then, we'll get this output:
25770 (gdb) -var-info-path-expression C.Base.public.m_size
25771 ^done,path_expr=((Base)c).m_size)
25774 @subheading The @code{-var-show-attributes} Command
25775 @findex -var-show-attributes
25777 @subsubheading Synopsis
25780 -var-show-attributes @var{name}
25783 List attributes of the specified variable object @var{name}:
25786 status=@var{attr} [ ( ,@var{attr} )* ]
25790 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
25792 @subheading The @code{-var-evaluate-expression} Command
25793 @findex -var-evaluate-expression
25795 @subsubheading Synopsis
25798 -var-evaluate-expression [-f @var{format-spec}] @var{name}
25801 Evaluates the expression that is represented by the specified variable
25802 object and returns its value as a string. The format of the string
25803 can be specified with the @samp{-f} option. The possible values of
25804 this option are the same as for @code{-var-set-format}
25805 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
25806 the current display format will be used. The current display format
25807 can be changed using the @code{-var-set-format} command.
25813 Note that one must invoke @code{-var-list-children} for a variable
25814 before the value of a child variable can be evaluated.
25816 @subheading The @code{-var-assign} Command
25817 @findex -var-assign
25819 @subsubheading Synopsis
25822 -var-assign @var{name} @var{expression}
25825 Assigns the value of @var{expression} to the variable object specified
25826 by @var{name}. The object must be @samp{editable}. If the variable's
25827 value is altered by the assign, the variable will show up in any
25828 subsequent @code{-var-update} list.
25830 @subsubheading Example
25838 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
25842 @subheading The @code{-var-update} Command
25843 @findex -var-update
25845 @subsubheading Synopsis
25848 -var-update [@var{print-values}] @{@var{name} | "*"@}
25851 Reevaluate the expressions corresponding to the variable object
25852 @var{name} and all its direct and indirect children, and return the
25853 list of variable objects whose values have changed; @var{name} must
25854 be a root variable object. Here, ``changed'' means that the result of
25855 @code{-var-evaluate-expression} before and after the
25856 @code{-var-update} is different. If @samp{*} is used as the variable
25857 object names, all existing variable objects are updated, except
25858 for frozen ones (@pxref{-var-set-frozen}). The option
25859 @var{print-values} determines whether both names and values, or just
25860 names are printed. The possible values of this option are the same
25861 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
25862 recommended to use the @samp{--all-values} option, to reduce the
25863 number of MI commands needed on each program stop.
25865 With the @samp{*} parameter, if a variable object is bound to a
25866 currently running thread, it will not be updated, without any
25869 If @code{-var-set-update-range} was previously used on a varobj, then
25870 only the selected range of children will be reported.
25872 @code{-var-update} reports all the changed varobjs in a tuple named
25875 Each item in the change list is itself a tuple holding:
25879 The name of the varobj.
25882 If values were requested for this update, then this field will be
25883 present and will hold the value of the varobj.
25886 @anchor{-var-update}
25887 This field is a string which may take one of three values:
25891 The variable object's current value is valid.
25894 The variable object does not currently hold a valid value but it may
25895 hold one in the future if its associated expression comes back into
25899 The variable object no longer holds a valid value.
25900 This can occur when the executable file being debugged has changed,
25901 either through recompilation or by using the @value{GDBN} @code{file}
25902 command. The front end should normally choose to delete these variable
25906 In the future new values may be added to this list so the front should
25907 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
25910 This is only present if the varobj is still valid. If the type
25911 changed, then this will be the string @samp{true}; otherwise it will
25915 If the varobj's type changed, then this field will be present and will
25918 @item new_num_children
25919 For a dynamic varobj, if the number of children changed, or if the
25920 type changed, this will be the new number of children.
25922 The @samp{numchild} field in other varobj responses is generally not
25923 valid for a dynamic varobj -- it will show the number of children that
25924 @value{GDBN} knows about, but because dynamic varobjs lazily
25925 instantiate their children, this will not reflect the number of
25926 children which may be available.
25928 The @samp{new_num_children} attribute only reports changes to the
25929 number of children known by @value{GDBN}. This is the only way to
25930 detect whether an update has removed children (which necessarily can
25931 only happen at the end of the update range).
25934 The display hint, if any.
25937 This is an integer value, which will be 1 if there are more children
25938 available outside the varobj's update range.
25941 This attribute will be present and have the value @samp{1} if the
25942 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
25943 then this attribute will not be present.
25946 If new children were added to a dynamic varobj within the selected
25947 update range (as set by @code{-var-set-update-range}), then they will
25948 be listed in this attribute.
25951 @subsubheading Example
25958 -var-update --all-values var1
25959 ^done,changelist=[@{name="var1",value="3",in_scope="true",
25960 type_changed="false"@}]
25964 @subheading The @code{-var-set-frozen} Command
25965 @findex -var-set-frozen
25966 @anchor{-var-set-frozen}
25968 @subsubheading Synopsis
25971 -var-set-frozen @var{name} @var{flag}
25974 Set the frozenness flag on the variable object @var{name}. The
25975 @var{flag} parameter should be either @samp{1} to make the variable
25976 frozen or @samp{0} to make it unfrozen. If a variable object is
25977 frozen, then neither itself, nor any of its children, are
25978 implicitly updated by @code{-var-update} of
25979 a parent variable or by @code{-var-update *}. Only
25980 @code{-var-update} of the variable itself will update its value and
25981 values of its children. After a variable object is unfrozen, it is
25982 implicitly updated by all subsequent @code{-var-update} operations.
25983 Unfreezing a variable does not update it, only subsequent
25984 @code{-var-update} does.
25986 @subsubheading Example
25990 -var-set-frozen V 1
25995 @subheading The @code{-var-set-update-range} command
25996 @findex -var-set-update-range
25997 @anchor{-var-set-update-range}
25999 @subsubheading Synopsis
26002 -var-set-update-range @var{name} @var{from} @var{to}
26005 Set the range of children to be returned by future invocations of
26006 @code{-var-update}.
26008 @var{from} and @var{to} indicate the range of children to report. If
26009 @var{from} or @var{to} is less than zero, the range is reset and all
26010 children will be reported. Otherwise, children starting at @var{from}
26011 (zero-based) and up to and excluding @var{to} will be reported.
26013 @subsubheading Example
26017 -var-set-update-range V 1 2
26021 @subheading The @code{-var-set-visualizer} command
26022 @findex -var-set-visualizer
26023 @anchor{-var-set-visualizer}
26025 @subsubheading Synopsis
26028 -var-set-visualizer @var{name} @var{visualizer}
26031 Set a visualizer for the variable object @var{name}.
26033 @var{visualizer} is the visualizer to use. The special value
26034 @samp{None} means to disable any visualizer in use.
26036 If not @samp{None}, @var{visualizer} must be a Python expression.
26037 This expression must evaluate to a callable object which accepts a
26038 single argument. @value{GDBN} will call this object with the value of
26039 the varobj @var{name} as an argument (this is done so that the same
26040 Python pretty-printing code can be used for both the CLI and MI).
26041 When called, this object must return an object which conforms to the
26042 pretty-printing interface (@pxref{Pretty Printing API}).
26044 The pre-defined function @code{gdb.default_visualizer} may be used to
26045 select a visualizer by following the built-in process
26046 (@pxref{Selecting Pretty-Printers}). This is done automatically when
26047 a varobj is created, and so ordinarily is not needed.
26049 This feature is only available if Python support is enabled. The MI
26050 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
26051 can be used to check this.
26053 @subsubheading Example
26055 Resetting the visualizer:
26059 -var-set-visualizer V None
26063 Reselecting the default (type-based) visualizer:
26067 -var-set-visualizer V gdb.default_visualizer
26071 Suppose @code{SomeClass} is a visualizer class. A lambda expression
26072 can be used to instantiate this class for a varobj:
26076 -var-set-visualizer V "lambda val: SomeClass()"
26080 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26081 @node GDB/MI Data Manipulation
26082 @section @sc{gdb/mi} Data Manipulation
26084 @cindex data manipulation, in @sc{gdb/mi}
26085 @cindex @sc{gdb/mi}, data manipulation
26086 This section describes the @sc{gdb/mi} commands that manipulate data:
26087 examine memory and registers, evaluate expressions, etc.
26089 @c REMOVED FROM THE INTERFACE.
26090 @c @subheading -data-assign
26091 @c Change the value of a program variable. Plenty of side effects.
26092 @c @subsubheading GDB Command
26094 @c @subsubheading Example
26097 @subheading The @code{-data-disassemble} Command
26098 @findex -data-disassemble
26100 @subsubheading Synopsis
26104 [ -s @var{start-addr} -e @var{end-addr} ]
26105 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
26113 @item @var{start-addr}
26114 is the beginning address (or @code{$pc})
26115 @item @var{end-addr}
26117 @item @var{filename}
26118 is the name of the file to disassemble
26119 @item @var{linenum}
26120 is the line number to disassemble around
26122 is the number of disassembly lines to be produced. If it is -1,
26123 the whole function will be disassembled, in case no @var{end-addr} is
26124 specified. If @var{end-addr} is specified as a non-zero value, and
26125 @var{lines} is lower than the number of disassembly lines between
26126 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
26127 displayed; if @var{lines} is higher than the number of lines between
26128 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
26131 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
26135 @subsubheading Result
26137 The output for each instruction is composed of four fields:
26146 Note that whatever included in the instruction field, is not manipulated
26147 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
26149 @subsubheading @value{GDBN} Command
26151 There's no direct mapping from this command to the CLI.
26153 @subsubheading Example
26155 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
26159 -data-disassemble -s $pc -e "$pc + 20" -- 0
26162 @{address="0x000107c0",func-name="main",offset="4",
26163 inst="mov 2, %o0"@},
26164 @{address="0x000107c4",func-name="main",offset="8",
26165 inst="sethi %hi(0x11800), %o2"@},
26166 @{address="0x000107c8",func-name="main",offset="12",
26167 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
26168 @{address="0x000107cc",func-name="main",offset="16",
26169 inst="sethi %hi(0x11800), %o2"@},
26170 @{address="0x000107d0",func-name="main",offset="20",
26171 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
26175 Disassemble the whole @code{main} function. Line 32 is part of
26179 -data-disassemble -f basics.c -l 32 -- 0
26181 @{address="0x000107bc",func-name="main",offset="0",
26182 inst="save %sp, -112, %sp"@},
26183 @{address="0x000107c0",func-name="main",offset="4",
26184 inst="mov 2, %o0"@},
26185 @{address="0x000107c4",func-name="main",offset="8",
26186 inst="sethi %hi(0x11800), %o2"@},
26188 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
26189 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
26193 Disassemble 3 instructions from the start of @code{main}:
26197 -data-disassemble -f basics.c -l 32 -n 3 -- 0
26199 @{address="0x000107bc",func-name="main",offset="0",
26200 inst="save %sp, -112, %sp"@},
26201 @{address="0x000107c0",func-name="main",offset="4",
26202 inst="mov 2, %o0"@},
26203 @{address="0x000107c4",func-name="main",offset="8",
26204 inst="sethi %hi(0x11800), %o2"@}]
26208 Disassemble 3 instructions from the start of @code{main} in mixed mode:
26212 -data-disassemble -f basics.c -l 32 -n 3 -- 1
26214 src_and_asm_line=@{line="31",
26215 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
26216 testsuite/gdb.mi/basics.c",line_asm_insn=[
26217 @{address="0x000107bc",func-name="main",offset="0",
26218 inst="save %sp, -112, %sp"@}]@},
26219 src_and_asm_line=@{line="32",
26220 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
26221 testsuite/gdb.mi/basics.c",line_asm_insn=[
26222 @{address="0x000107c0",func-name="main",offset="4",
26223 inst="mov 2, %o0"@},
26224 @{address="0x000107c4",func-name="main",offset="8",
26225 inst="sethi %hi(0x11800), %o2"@}]@}]
26230 @subheading The @code{-data-evaluate-expression} Command
26231 @findex -data-evaluate-expression
26233 @subsubheading Synopsis
26236 -data-evaluate-expression @var{expr}
26239 Evaluate @var{expr} as an expression. The expression could contain an
26240 inferior function call. The function call will execute synchronously.
26241 If the expression contains spaces, it must be enclosed in double quotes.
26243 @subsubheading @value{GDBN} Command
26245 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
26246 @samp{call}. In @code{gdbtk} only, there's a corresponding
26247 @samp{gdb_eval} command.
26249 @subsubheading Example
26251 In the following example, the numbers that precede the commands are the
26252 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
26253 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
26257 211-data-evaluate-expression A
26260 311-data-evaluate-expression &A
26261 311^done,value="0xefffeb7c"
26263 411-data-evaluate-expression A+3
26266 511-data-evaluate-expression "A + 3"
26272 @subheading The @code{-data-list-changed-registers} Command
26273 @findex -data-list-changed-registers
26275 @subsubheading Synopsis
26278 -data-list-changed-registers
26281 Display a list of the registers that have changed.
26283 @subsubheading @value{GDBN} Command
26285 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
26286 has the corresponding command @samp{gdb_changed_register_list}.
26288 @subsubheading Example
26290 On a PPC MBX board:
26298 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
26299 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
26302 -data-list-changed-registers
26303 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
26304 "10","11","13","14","15","16","17","18","19","20","21","22","23",
26305 "24","25","26","27","28","30","31","64","65","66","67","69"]
26310 @subheading The @code{-data-list-register-names} Command
26311 @findex -data-list-register-names
26313 @subsubheading Synopsis
26316 -data-list-register-names [ ( @var{regno} )+ ]
26319 Show a list of register names for the current target. If no arguments
26320 are given, it shows a list of the names of all the registers. If
26321 integer numbers are given as arguments, it will print a list of the
26322 names of the registers corresponding to the arguments. To ensure
26323 consistency between a register name and its number, the output list may
26324 include empty register names.
26326 @subsubheading @value{GDBN} Command
26328 @value{GDBN} does not have a command which corresponds to
26329 @samp{-data-list-register-names}. In @code{gdbtk} there is a
26330 corresponding command @samp{gdb_regnames}.
26332 @subsubheading Example
26334 For the PPC MBX board:
26337 -data-list-register-names
26338 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
26339 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
26340 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
26341 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
26342 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
26343 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
26344 "", "pc","ps","cr","lr","ctr","xer"]
26346 -data-list-register-names 1 2 3
26347 ^done,register-names=["r1","r2","r3"]
26351 @subheading The @code{-data-list-register-values} Command
26352 @findex -data-list-register-values
26354 @subsubheading Synopsis
26357 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
26360 Display the registers' contents. @var{fmt} is the format according to
26361 which the registers' contents are to be returned, followed by an optional
26362 list of numbers specifying the registers to display. A missing list of
26363 numbers indicates that the contents of all the registers must be returned.
26365 Allowed formats for @var{fmt} are:
26382 @subsubheading @value{GDBN} Command
26384 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
26385 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
26387 @subsubheading Example
26389 For a PPC MBX board (note: line breaks are for readability only, they
26390 don't appear in the actual output):
26394 -data-list-register-values r 64 65
26395 ^done,register-values=[@{number="64",value="0xfe00a300"@},
26396 @{number="65",value="0x00029002"@}]
26398 -data-list-register-values x
26399 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
26400 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
26401 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
26402 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
26403 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
26404 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
26405 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
26406 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
26407 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
26408 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
26409 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
26410 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
26411 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
26412 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
26413 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
26414 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
26415 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
26416 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
26417 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
26418 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
26419 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
26420 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
26421 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
26422 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
26423 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
26424 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
26425 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
26426 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
26427 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
26428 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
26429 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
26430 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
26431 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
26432 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
26433 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
26434 @{number="69",value="0x20002b03"@}]
26439 @subheading The @code{-data-read-memory} Command
26440 @findex -data-read-memory
26442 @subsubheading Synopsis
26445 -data-read-memory [ -o @var{byte-offset} ]
26446 @var{address} @var{word-format} @var{word-size}
26447 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
26454 @item @var{address}
26455 An expression specifying the address of the first memory word to be
26456 read. Complex expressions containing embedded white space should be
26457 quoted using the C convention.
26459 @item @var{word-format}
26460 The format to be used to print the memory words. The notation is the
26461 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
26464 @item @var{word-size}
26465 The size of each memory word in bytes.
26467 @item @var{nr-rows}
26468 The number of rows in the output table.
26470 @item @var{nr-cols}
26471 The number of columns in the output table.
26474 If present, indicates that each row should include an @sc{ascii} dump. The
26475 value of @var{aschar} is used as a padding character when a byte is not a
26476 member of the printable @sc{ascii} character set (printable @sc{ascii}
26477 characters are those whose code is between 32 and 126, inclusively).
26479 @item @var{byte-offset}
26480 An offset to add to the @var{address} before fetching memory.
26483 This command displays memory contents as a table of @var{nr-rows} by
26484 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
26485 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
26486 (returned as @samp{total-bytes}). Should less than the requested number
26487 of bytes be returned by the target, the missing words are identified
26488 using @samp{N/A}. The number of bytes read from the target is returned
26489 in @samp{nr-bytes} and the starting address used to read memory in
26492 The address of the next/previous row or page is available in
26493 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
26496 @subsubheading @value{GDBN} Command
26498 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
26499 @samp{gdb_get_mem} memory read command.
26501 @subsubheading Example
26503 Read six bytes of memory starting at @code{bytes+6} but then offset by
26504 @code{-6} bytes. Format as three rows of two columns. One byte per
26505 word. Display each word in hex.
26509 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
26510 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
26511 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
26512 prev-page="0x0000138a",memory=[
26513 @{addr="0x00001390",data=["0x00","0x01"]@},
26514 @{addr="0x00001392",data=["0x02","0x03"]@},
26515 @{addr="0x00001394",data=["0x04","0x05"]@}]
26519 Read two bytes of memory starting at address @code{shorts + 64} and
26520 display as a single word formatted in decimal.
26524 5-data-read-memory shorts+64 d 2 1 1
26525 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
26526 next-row="0x00001512",prev-row="0x0000150e",
26527 next-page="0x00001512",prev-page="0x0000150e",memory=[
26528 @{addr="0x00001510",data=["128"]@}]
26532 Read thirty two bytes of memory starting at @code{bytes+16} and format
26533 as eight rows of four columns. Include a string encoding with @samp{x}
26534 used as the non-printable character.
26538 4-data-read-memory bytes+16 x 1 8 4 x
26539 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
26540 next-row="0x000013c0",prev-row="0x0000139c",
26541 next-page="0x000013c0",prev-page="0x00001380",memory=[
26542 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
26543 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
26544 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
26545 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
26546 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
26547 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
26548 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
26549 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
26553 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26554 @node GDB/MI Tracepoint Commands
26555 @section @sc{gdb/mi} Tracepoint Commands
26557 The commands defined in this section implement MI support for
26558 tracepoints. For detailed introduction, see @ref{Tracepoints}.
26560 @subheading The @code{-trace-find} Command
26561 @findex -trace-find
26563 @subsubheading Synopsis
26566 -trace-find @var{mode} [@var{parameters}@dots{}]
26569 Find a trace frame using criteria defined by @var{mode} and
26570 @var{parameters}. The following table lists permissible
26571 modes and their parameters. For details of operation, see @ref{tfind}.
26576 No parameters are required. Stops examining trace frames.
26579 An integer is required as parameter. Selects tracepoint frame with
26582 @item tracepoint-number
26583 An integer is required as parameter. Finds next
26584 trace frame that corresponds to tracepoint with the specified number.
26587 An address is required as parameter. Finds
26588 next trace frame that corresponds to any tracepoint at the specified
26591 @item pc-inside-range
26592 Two addresses are required as parameters. Finds next trace
26593 frame that corresponds to a tracepoint at an address inside the
26594 specified range. Both bounds are considered to be inside the range.
26596 @item pc-outside-range
26597 Two addresses are required as parameters. Finds
26598 next trace frame that corresponds to a tracepoint at an address outside
26599 the specified range. Both bounds are considered to be inside the range.
26602 Line specification is required as parameter. @xref{Specify Location}.
26603 Finds next trace frame that corresponds to a tracepoint at
26604 the specified location.
26608 If @samp{none} was passed as @var{mode}, the response does not
26609 have fields. Otherwise, the response may have the following fields:
26613 This field has either @samp{0} or @samp{1} as the value, depending
26614 on whether a matching tracepoint was found.
26617 The index of the found traceframe. This field is present iff
26618 the @samp{found} field has value of @samp{1}.
26621 The index of the found tracepoint. This field is present iff
26622 the @samp{found} field has value of @samp{1}.
26625 The information about the frame corresponding to the found trace
26626 frame. This field is present only if a trace frame was found.
26627 @xref{GDB/MI Frame Information}, for description of this field.
26631 @subsubheading @value{GDBN} Command
26633 The corresponding @value{GDBN} command is @samp{tfind}.
26635 @subheading -trace-define-variable
26636 @findex -trace-define-variable
26638 @subsubheading Synopsis
26641 -trace-define-variable @var{name} [ @var{value} ]
26644 Create trace variable @var{name} if it does not exist. If
26645 @var{value} is specified, sets the initial value of the specified
26646 trace variable to that value. Note that the @var{name} should start
26647 with the @samp{$} character.
26649 @subsubheading @value{GDBN} Command
26651 The corresponding @value{GDBN} command is @samp{tvariable}.
26653 @subheading -trace-list-variables
26654 @findex -trace-list-variables
26656 @subsubheading Synopsis
26659 -trace-list-variables
26662 Return a table of all defined trace variables. Each element of the
26663 table has the following fields:
26667 The name of the trace variable. This field is always present.
26670 The initial value. This is a 64-bit signed integer. This
26671 field is always present.
26674 The value the trace variable has at the moment. This is a 64-bit
26675 signed integer. This field is absent iff current value is
26676 not defined, for example if the trace was never run, or is
26681 @subsubheading @value{GDBN} Command
26683 The corresponding @value{GDBN} command is @samp{tvariables}.
26685 @subsubheading Example
26689 -trace-list-variables
26690 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
26691 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
26692 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
26693 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
26694 body=[variable=@{name="$trace_timestamp",initial="0"@}
26695 variable=@{name="$foo",initial="10",current="15"@}]@}
26699 @subheading -trace-save
26700 @findex -trace-save
26702 @subsubheading Synopsis
26705 -trace-save [-r ] @var{filename}
26708 Saves the collected trace data to @var{filename}. Without the
26709 @samp{-r} option, the data is downloaded from the target and saved
26710 in a local file. With the @samp{-r} option the target is asked
26711 to perform the save.
26713 @subsubheading @value{GDBN} Command
26715 The corresponding @value{GDBN} command is @samp{tsave}.
26718 @subheading -trace-start
26719 @findex -trace-start
26721 @subsubheading Synopsis
26727 Starts a tracing experiments. The result of this command does not
26730 @subsubheading @value{GDBN} Command
26732 The corresponding @value{GDBN} command is @samp{tstart}.
26734 @subheading -trace-status
26735 @findex -trace-status
26737 @subsubheading Synopsis
26743 Obtains the status of a tracing experiment. The result may include
26744 the following fields:
26749 May have a value of either @samp{0}, when no tracing operations are
26750 supported, @samp{1}, when all tracing operations are supported, or
26751 @samp{file} when examining trace file. In the latter case, examining
26752 of trace frame is possible but new tracing experiement cannot be
26753 started. This field is always present.
26756 May have a value of either @samp{0} or @samp{1} depending on whether
26757 tracing experiement is in progress on target. This field is present
26758 if @samp{supported} field is not @samp{0}.
26761 Report the reason why the tracing was stopped last time. This field
26762 may be absent iff tracing was never stopped on target yet. The
26763 value of @samp{request} means the tracing was stopped as result of
26764 the @code{-trace-stop} command. The value of @samp{overflow} means
26765 the tracing buffer is full. The value of @samp{disconnection} means
26766 tracing was automatically stopped when @value{GDBN} has disconnected.
26767 The value of @samp{passcount} means tracing was stopped when a
26768 tracepoint was passed a maximal number of times for that tracepoint.
26769 This field is present if @samp{supported} field is not @samp{0}.
26771 @item stopping-tracepoint
26772 The number of tracepoint whose passcount as exceeded. This field is
26773 present iff the @samp{stop-reason} field has the value of
26777 @itemx frames-created
26778 The @samp{frames} field is a count of the total number of trace frames
26779 in the trace buffer, while @samp{frames-created} is the total created
26780 during the run, including ones that were discarded, such as when a
26781 circular trace buffer filled up. Both fields are optional.
26785 These fields tell the current size of the tracing buffer and the
26786 remaining space. These fields are optional.
26789 The value of the circular trace buffer flag. @code{1} means that the
26790 trace buffer is circular and old trace frames will be discarded if
26791 necessary to make room, @code{0} means that the trace buffer is linear
26795 The value of the disconnected tracing flag. @code{1} means that
26796 tracing will continue after @value{GDBN} disconnects, @code{0} means
26797 that the trace run will stop.
26801 @subsubheading @value{GDBN} Command
26803 The corresponding @value{GDBN} command is @samp{tstatus}.
26805 @subheading -trace-stop
26806 @findex -trace-stop
26808 @subsubheading Synopsis
26814 Stops a tracing experiment. The result of this command has the same
26815 fields as @code{-trace-status}, except that the @samp{supported} and
26816 @samp{running} fields are not output.
26818 @subsubheading @value{GDBN} Command
26820 The corresponding @value{GDBN} command is @samp{tstop}.
26823 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26824 @node GDB/MI Symbol Query
26825 @section @sc{gdb/mi} Symbol Query Commands
26829 @subheading The @code{-symbol-info-address} Command
26830 @findex -symbol-info-address
26832 @subsubheading Synopsis
26835 -symbol-info-address @var{symbol}
26838 Describe where @var{symbol} is stored.
26840 @subsubheading @value{GDBN} Command
26842 The corresponding @value{GDBN} command is @samp{info address}.
26844 @subsubheading Example
26848 @subheading The @code{-symbol-info-file} Command
26849 @findex -symbol-info-file
26851 @subsubheading Synopsis
26857 Show the file for the symbol.
26859 @subsubheading @value{GDBN} Command
26861 There's no equivalent @value{GDBN} command. @code{gdbtk} has
26862 @samp{gdb_find_file}.
26864 @subsubheading Example
26868 @subheading The @code{-symbol-info-function} Command
26869 @findex -symbol-info-function
26871 @subsubheading Synopsis
26874 -symbol-info-function
26877 Show which function the symbol lives in.
26879 @subsubheading @value{GDBN} Command
26881 @samp{gdb_get_function} in @code{gdbtk}.
26883 @subsubheading Example
26887 @subheading The @code{-symbol-info-line} Command
26888 @findex -symbol-info-line
26890 @subsubheading Synopsis
26896 Show the core addresses of the code for a source line.
26898 @subsubheading @value{GDBN} Command
26900 The corresponding @value{GDBN} command is @samp{info line}.
26901 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
26903 @subsubheading Example
26907 @subheading The @code{-symbol-info-symbol} Command
26908 @findex -symbol-info-symbol
26910 @subsubheading Synopsis
26913 -symbol-info-symbol @var{addr}
26916 Describe what symbol is at location @var{addr}.
26918 @subsubheading @value{GDBN} Command
26920 The corresponding @value{GDBN} command is @samp{info symbol}.
26922 @subsubheading Example
26926 @subheading The @code{-symbol-list-functions} Command
26927 @findex -symbol-list-functions
26929 @subsubheading Synopsis
26932 -symbol-list-functions
26935 List the functions in the executable.
26937 @subsubheading @value{GDBN} Command
26939 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
26940 @samp{gdb_search} in @code{gdbtk}.
26942 @subsubheading Example
26947 @subheading The @code{-symbol-list-lines} Command
26948 @findex -symbol-list-lines
26950 @subsubheading Synopsis
26953 -symbol-list-lines @var{filename}
26956 Print the list of lines that contain code and their associated program
26957 addresses for the given source filename. The entries are sorted in
26958 ascending PC order.
26960 @subsubheading @value{GDBN} Command
26962 There is no corresponding @value{GDBN} command.
26964 @subsubheading Example
26967 -symbol-list-lines basics.c
26968 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
26974 @subheading The @code{-symbol-list-types} Command
26975 @findex -symbol-list-types
26977 @subsubheading Synopsis
26983 List all the type names.
26985 @subsubheading @value{GDBN} Command
26987 The corresponding commands are @samp{info types} in @value{GDBN},
26988 @samp{gdb_search} in @code{gdbtk}.
26990 @subsubheading Example
26994 @subheading The @code{-symbol-list-variables} Command
26995 @findex -symbol-list-variables
26997 @subsubheading Synopsis
27000 -symbol-list-variables
27003 List all the global and static variable names.
27005 @subsubheading @value{GDBN} Command
27007 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
27009 @subsubheading Example
27013 @subheading The @code{-symbol-locate} Command
27014 @findex -symbol-locate
27016 @subsubheading Synopsis
27022 @subsubheading @value{GDBN} Command
27024 @samp{gdb_loc} in @code{gdbtk}.
27026 @subsubheading Example
27030 @subheading The @code{-symbol-type} Command
27031 @findex -symbol-type
27033 @subsubheading Synopsis
27036 -symbol-type @var{variable}
27039 Show type of @var{variable}.
27041 @subsubheading @value{GDBN} Command
27043 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
27044 @samp{gdb_obj_variable}.
27046 @subsubheading Example
27051 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27052 @node GDB/MI File Commands
27053 @section @sc{gdb/mi} File Commands
27055 This section describes the GDB/MI commands to specify executable file names
27056 and to read in and obtain symbol table information.
27058 @subheading The @code{-file-exec-and-symbols} Command
27059 @findex -file-exec-and-symbols
27061 @subsubheading Synopsis
27064 -file-exec-and-symbols @var{file}
27067 Specify the executable file to be debugged. This file is the one from
27068 which the symbol table is also read. If no file is specified, the
27069 command clears the executable and symbol information. If breakpoints
27070 are set when using this command with no arguments, @value{GDBN} will produce
27071 error messages. Otherwise, no output is produced, except a completion
27074 @subsubheading @value{GDBN} Command
27076 The corresponding @value{GDBN} command is @samp{file}.
27078 @subsubheading Example
27082 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27088 @subheading The @code{-file-exec-file} Command
27089 @findex -file-exec-file
27091 @subsubheading Synopsis
27094 -file-exec-file @var{file}
27097 Specify the executable file to be debugged. Unlike
27098 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
27099 from this file. If used without argument, @value{GDBN} clears the information
27100 about the executable file. No output is produced, except a completion
27103 @subsubheading @value{GDBN} Command
27105 The corresponding @value{GDBN} command is @samp{exec-file}.
27107 @subsubheading Example
27111 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27118 @subheading The @code{-file-list-exec-sections} Command
27119 @findex -file-list-exec-sections
27121 @subsubheading Synopsis
27124 -file-list-exec-sections
27127 List the sections of the current executable file.
27129 @subsubheading @value{GDBN} Command
27131 The @value{GDBN} command @samp{info file} shows, among the rest, the same
27132 information as this command. @code{gdbtk} has a corresponding command
27133 @samp{gdb_load_info}.
27135 @subsubheading Example
27140 @subheading The @code{-file-list-exec-source-file} Command
27141 @findex -file-list-exec-source-file
27143 @subsubheading Synopsis
27146 -file-list-exec-source-file
27149 List the line number, the current source file, and the absolute path
27150 to the current source file for the current executable. The macro
27151 information field has a value of @samp{1} or @samp{0} depending on
27152 whether or not the file includes preprocessor macro information.
27154 @subsubheading @value{GDBN} Command
27156 The @value{GDBN} equivalent is @samp{info source}
27158 @subsubheading Example
27162 123-file-list-exec-source-file
27163 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
27168 @subheading The @code{-file-list-exec-source-files} Command
27169 @findex -file-list-exec-source-files
27171 @subsubheading Synopsis
27174 -file-list-exec-source-files
27177 List the source files for the current executable.
27179 It will always output the filename, but only when @value{GDBN} can find
27180 the absolute file name of a source file, will it output the fullname.
27182 @subsubheading @value{GDBN} Command
27184 The @value{GDBN} equivalent is @samp{info sources}.
27185 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
27187 @subsubheading Example
27190 -file-list-exec-source-files
27192 @{file=foo.c,fullname=/home/foo.c@},
27193 @{file=/home/bar.c,fullname=/home/bar.c@},
27194 @{file=gdb_could_not_find_fullpath.c@}]
27199 @subheading The @code{-file-list-shared-libraries} Command
27200 @findex -file-list-shared-libraries
27202 @subsubheading Synopsis
27205 -file-list-shared-libraries
27208 List the shared libraries in the program.
27210 @subsubheading @value{GDBN} Command
27212 The corresponding @value{GDBN} command is @samp{info shared}.
27214 @subsubheading Example
27218 @subheading The @code{-file-list-symbol-files} Command
27219 @findex -file-list-symbol-files
27221 @subsubheading Synopsis
27224 -file-list-symbol-files
27229 @subsubheading @value{GDBN} Command
27231 The corresponding @value{GDBN} command is @samp{info file} (part of it).
27233 @subsubheading Example
27238 @subheading The @code{-file-symbol-file} Command
27239 @findex -file-symbol-file
27241 @subsubheading Synopsis
27244 -file-symbol-file @var{file}
27247 Read symbol table info from the specified @var{file} argument. When
27248 used without arguments, clears @value{GDBN}'s symbol table info. No output is
27249 produced, except for a completion notification.
27251 @subsubheading @value{GDBN} Command
27253 The corresponding @value{GDBN} command is @samp{symbol-file}.
27255 @subsubheading Example
27259 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27265 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27266 @node GDB/MI Memory Overlay Commands
27267 @section @sc{gdb/mi} Memory Overlay Commands
27269 The memory overlay commands are not implemented.
27271 @c @subheading -overlay-auto
27273 @c @subheading -overlay-list-mapping-state
27275 @c @subheading -overlay-list-overlays
27277 @c @subheading -overlay-map
27279 @c @subheading -overlay-off
27281 @c @subheading -overlay-on
27283 @c @subheading -overlay-unmap
27285 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27286 @node GDB/MI Signal Handling Commands
27287 @section @sc{gdb/mi} Signal Handling Commands
27289 Signal handling commands are not implemented.
27291 @c @subheading -signal-handle
27293 @c @subheading -signal-list-handle-actions
27295 @c @subheading -signal-list-signal-types
27299 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27300 @node GDB/MI Target Manipulation
27301 @section @sc{gdb/mi} Target Manipulation Commands
27304 @subheading The @code{-target-attach} Command
27305 @findex -target-attach
27307 @subsubheading Synopsis
27310 -target-attach @var{pid} | @var{gid} | @var{file}
27313 Attach to a process @var{pid} or a file @var{file} outside of
27314 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
27315 group, the id previously returned by
27316 @samp{-list-thread-groups --available} must be used.
27318 @subsubheading @value{GDBN} Command
27320 The corresponding @value{GDBN} command is @samp{attach}.
27322 @subsubheading Example
27326 =thread-created,id="1"
27327 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
27333 @subheading The @code{-target-compare-sections} Command
27334 @findex -target-compare-sections
27336 @subsubheading Synopsis
27339 -target-compare-sections [ @var{section} ]
27342 Compare data of section @var{section} on target to the exec file.
27343 Without the argument, all sections are compared.
27345 @subsubheading @value{GDBN} Command
27347 The @value{GDBN} equivalent is @samp{compare-sections}.
27349 @subsubheading Example
27354 @subheading The @code{-target-detach} Command
27355 @findex -target-detach
27357 @subsubheading Synopsis
27360 -target-detach [ @var{pid} | @var{gid} ]
27363 Detach from the remote target which normally resumes its execution.
27364 If either @var{pid} or @var{gid} is specified, detaches from either
27365 the specified process, or specified thread group. There's no output.
27367 @subsubheading @value{GDBN} Command
27369 The corresponding @value{GDBN} command is @samp{detach}.
27371 @subsubheading Example
27381 @subheading The @code{-target-disconnect} Command
27382 @findex -target-disconnect
27384 @subsubheading Synopsis
27390 Disconnect from the remote target. There's no output and the target is
27391 generally not resumed.
27393 @subsubheading @value{GDBN} Command
27395 The corresponding @value{GDBN} command is @samp{disconnect}.
27397 @subsubheading Example
27407 @subheading The @code{-target-download} Command
27408 @findex -target-download
27410 @subsubheading Synopsis
27416 Loads the executable onto the remote target.
27417 It prints out an update message every half second, which includes the fields:
27421 The name of the section.
27423 The size of what has been sent so far for that section.
27425 The size of the section.
27427 The total size of what was sent so far (the current and the previous sections).
27429 The size of the overall executable to download.
27433 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
27434 @sc{gdb/mi} Output Syntax}).
27436 In addition, it prints the name and size of the sections, as they are
27437 downloaded. These messages include the following fields:
27441 The name of the section.
27443 The size of the section.
27445 The size of the overall executable to download.
27449 At the end, a summary is printed.
27451 @subsubheading @value{GDBN} Command
27453 The corresponding @value{GDBN} command is @samp{load}.
27455 @subsubheading Example
27457 Note: each status message appears on a single line. Here the messages
27458 have been broken down so that they can fit onto a page.
27463 +download,@{section=".text",section-size="6668",total-size="9880"@}
27464 +download,@{section=".text",section-sent="512",section-size="6668",
27465 total-sent="512",total-size="9880"@}
27466 +download,@{section=".text",section-sent="1024",section-size="6668",
27467 total-sent="1024",total-size="9880"@}
27468 +download,@{section=".text",section-sent="1536",section-size="6668",
27469 total-sent="1536",total-size="9880"@}
27470 +download,@{section=".text",section-sent="2048",section-size="6668",
27471 total-sent="2048",total-size="9880"@}
27472 +download,@{section=".text",section-sent="2560",section-size="6668",
27473 total-sent="2560",total-size="9880"@}
27474 +download,@{section=".text",section-sent="3072",section-size="6668",
27475 total-sent="3072",total-size="9880"@}
27476 +download,@{section=".text",section-sent="3584",section-size="6668",
27477 total-sent="3584",total-size="9880"@}
27478 +download,@{section=".text",section-sent="4096",section-size="6668",
27479 total-sent="4096",total-size="9880"@}
27480 +download,@{section=".text",section-sent="4608",section-size="6668",
27481 total-sent="4608",total-size="9880"@}
27482 +download,@{section=".text",section-sent="5120",section-size="6668",
27483 total-sent="5120",total-size="9880"@}
27484 +download,@{section=".text",section-sent="5632",section-size="6668",
27485 total-sent="5632",total-size="9880"@}
27486 +download,@{section=".text",section-sent="6144",section-size="6668",
27487 total-sent="6144",total-size="9880"@}
27488 +download,@{section=".text",section-sent="6656",section-size="6668",
27489 total-sent="6656",total-size="9880"@}
27490 +download,@{section=".init",section-size="28",total-size="9880"@}
27491 +download,@{section=".fini",section-size="28",total-size="9880"@}
27492 +download,@{section=".data",section-size="3156",total-size="9880"@}
27493 +download,@{section=".data",section-sent="512",section-size="3156",
27494 total-sent="7236",total-size="9880"@}
27495 +download,@{section=".data",section-sent="1024",section-size="3156",
27496 total-sent="7748",total-size="9880"@}
27497 +download,@{section=".data",section-sent="1536",section-size="3156",
27498 total-sent="8260",total-size="9880"@}
27499 +download,@{section=".data",section-sent="2048",section-size="3156",
27500 total-sent="8772",total-size="9880"@}
27501 +download,@{section=".data",section-sent="2560",section-size="3156",
27502 total-sent="9284",total-size="9880"@}
27503 +download,@{section=".data",section-sent="3072",section-size="3156",
27504 total-sent="9796",total-size="9880"@}
27505 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
27512 @subheading The @code{-target-exec-status} Command
27513 @findex -target-exec-status
27515 @subsubheading Synopsis
27518 -target-exec-status
27521 Provide information on the state of the target (whether it is running or
27522 not, for instance).
27524 @subsubheading @value{GDBN} Command
27526 There's no equivalent @value{GDBN} command.
27528 @subsubheading Example
27532 @subheading The @code{-target-list-available-targets} Command
27533 @findex -target-list-available-targets
27535 @subsubheading Synopsis
27538 -target-list-available-targets
27541 List the possible targets to connect to.
27543 @subsubheading @value{GDBN} Command
27545 The corresponding @value{GDBN} command is @samp{help target}.
27547 @subsubheading Example
27551 @subheading The @code{-target-list-current-targets} Command
27552 @findex -target-list-current-targets
27554 @subsubheading Synopsis
27557 -target-list-current-targets
27560 Describe the current target.
27562 @subsubheading @value{GDBN} Command
27564 The corresponding information is printed by @samp{info file} (among
27567 @subsubheading Example
27571 @subheading The @code{-target-list-parameters} Command
27572 @findex -target-list-parameters
27574 @subsubheading Synopsis
27577 -target-list-parameters
27583 @subsubheading @value{GDBN} Command
27587 @subsubheading Example
27591 @subheading The @code{-target-select} Command
27592 @findex -target-select
27594 @subsubheading Synopsis
27597 -target-select @var{type} @var{parameters @dots{}}
27600 Connect @value{GDBN} to the remote target. This command takes two args:
27604 The type of target, for instance @samp{remote}, etc.
27605 @item @var{parameters}
27606 Device names, host names and the like. @xref{Target Commands, ,
27607 Commands for Managing Targets}, for more details.
27610 The output is a connection notification, followed by the address at
27611 which the target program is, in the following form:
27614 ^connected,addr="@var{address}",func="@var{function name}",
27615 args=[@var{arg list}]
27618 @subsubheading @value{GDBN} Command
27620 The corresponding @value{GDBN} command is @samp{target}.
27622 @subsubheading Example
27626 -target-select remote /dev/ttya
27627 ^connected,addr="0xfe00a300",func="??",args=[]
27631 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27632 @node GDB/MI File Transfer Commands
27633 @section @sc{gdb/mi} File Transfer Commands
27636 @subheading The @code{-target-file-put} Command
27637 @findex -target-file-put
27639 @subsubheading Synopsis
27642 -target-file-put @var{hostfile} @var{targetfile}
27645 Copy file @var{hostfile} from the host system (the machine running
27646 @value{GDBN}) to @var{targetfile} on the target system.
27648 @subsubheading @value{GDBN} Command
27650 The corresponding @value{GDBN} command is @samp{remote put}.
27652 @subsubheading Example
27656 -target-file-put localfile remotefile
27662 @subheading The @code{-target-file-get} Command
27663 @findex -target-file-get
27665 @subsubheading Synopsis
27668 -target-file-get @var{targetfile} @var{hostfile}
27671 Copy file @var{targetfile} from the target system to @var{hostfile}
27672 on the host system.
27674 @subsubheading @value{GDBN} Command
27676 The corresponding @value{GDBN} command is @samp{remote get}.
27678 @subsubheading Example
27682 -target-file-get remotefile localfile
27688 @subheading The @code{-target-file-delete} Command
27689 @findex -target-file-delete
27691 @subsubheading Synopsis
27694 -target-file-delete @var{targetfile}
27697 Delete @var{targetfile} from the target system.
27699 @subsubheading @value{GDBN} Command
27701 The corresponding @value{GDBN} command is @samp{remote delete}.
27703 @subsubheading Example
27707 -target-file-delete remotefile
27713 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27714 @node GDB/MI Miscellaneous Commands
27715 @section Miscellaneous @sc{gdb/mi} Commands
27717 @c @subheading -gdb-complete
27719 @subheading The @code{-gdb-exit} Command
27722 @subsubheading Synopsis
27728 Exit @value{GDBN} immediately.
27730 @subsubheading @value{GDBN} Command
27732 Approximately corresponds to @samp{quit}.
27734 @subsubheading Example
27744 @subheading The @code{-exec-abort} Command
27745 @findex -exec-abort
27747 @subsubheading Synopsis
27753 Kill the inferior running program.
27755 @subsubheading @value{GDBN} Command
27757 The corresponding @value{GDBN} command is @samp{kill}.
27759 @subsubheading Example
27764 @subheading The @code{-gdb-set} Command
27767 @subsubheading Synopsis
27773 Set an internal @value{GDBN} variable.
27774 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
27776 @subsubheading @value{GDBN} Command
27778 The corresponding @value{GDBN} command is @samp{set}.
27780 @subsubheading Example
27790 @subheading The @code{-gdb-show} Command
27793 @subsubheading Synopsis
27799 Show the current value of a @value{GDBN} variable.
27801 @subsubheading @value{GDBN} Command
27803 The corresponding @value{GDBN} command is @samp{show}.
27805 @subsubheading Example
27814 @c @subheading -gdb-source
27817 @subheading The @code{-gdb-version} Command
27818 @findex -gdb-version
27820 @subsubheading Synopsis
27826 Show version information for @value{GDBN}. Used mostly in testing.
27828 @subsubheading @value{GDBN} Command
27830 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
27831 default shows this information when you start an interactive session.
27833 @subsubheading Example
27835 @c This example modifies the actual output from GDB to avoid overfull
27841 ~Copyright 2000 Free Software Foundation, Inc.
27842 ~GDB is free software, covered by the GNU General Public License, and
27843 ~you are welcome to change it and/or distribute copies of it under
27844 ~ certain conditions.
27845 ~Type "show copying" to see the conditions.
27846 ~There is absolutely no warranty for GDB. Type "show warranty" for
27848 ~This GDB was configured as
27849 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
27854 @subheading The @code{-list-features} Command
27855 @findex -list-features
27857 Returns a list of particular features of the MI protocol that
27858 this version of gdb implements. A feature can be a command,
27859 or a new field in an output of some command, or even an
27860 important bugfix. While a frontend can sometimes detect presence
27861 of a feature at runtime, it is easier to perform detection at debugger
27864 The command returns a list of strings, with each string naming an
27865 available feature. Each returned string is just a name, it does not
27866 have any internal structure. The list of possible feature names
27872 (gdb) -list-features
27873 ^done,result=["feature1","feature2"]
27876 The current list of features is:
27879 @item frozen-varobjs
27880 Indicates presence of the @code{-var-set-frozen} command, as well
27881 as possible presense of the @code{frozen} field in the output
27882 of @code{-varobj-create}.
27883 @item pending-breakpoints
27884 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
27886 Indicates presence of Python scripting support, Python-based
27887 pretty-printing commands, and possible presence of the
27888 @samp{display_hint} field in the output of @code{-var-list-children}
27890 Indicates presence of the @code{-thread-info} command.
27894 @subheading The @code{-list-target-features} Command
27895 @findex -list-target-features
27897 Returns a list of particular features that are supported by the
27898 target. Those features affect the permitted MI commands, but
27899 unlike the features reported by the @code{-list-features} command, the
27900 features depend on which target GDB is using at the moment. Whenever
27901 a target can change, due to commands such as @code{-target-select},
27902 @code{-target-attach} or @code{-exec-run}, the list of target features
27903 may change, and the frontend should obtain it again.
27907 (gdb) -list-features
27908 ^done,result=["async"]
27911 The current list of features is:
27915 Indicates that the target is capable of asynchronous command
27916 execution, which means that @value{GDBN} will accept further commands
27917 while the target is running.
27921 @subheading The @code{-list-thread-groups} Command
27922 @findex -list-thread-groups
27924 @subheading Synopsis
27927 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
27930 Lists thread groups (@pxref{Thread groups}). When a single thread
27931 group is passed as the argument, lists the children of that group.
27932 When several thread group are passed, lists information about those
27933 thread groups. Without any parameters, lists information about all
27934 top-level thread groups.
27936 Normally, thread groups that are being debugged are reported.
27937 With the @samp{--available} option, @value{GDBN} reports thread groups
27938 available on the target.
27940 The output of this command may have either a @samp{threads} result or
27941 a @samp{groups} result. The @samp{thread} result has a list of tuples
27942 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
27943 Information}). The @samp{groups} result has a list of tuples as value,
27944 each tuple describing a thread group. If top-level groups are
27945 requested (that is, no parameter is passed), or when several groups
27946 are passed, the output always has a @samp{groups} result. The format
27947 of the @samp{group} result is described below.
27949 To reduce the number of roundtrips it's possible to list thread groups
27950 together with their children, by passing the @samp{--recurse} option
27951 and the recursion depth. Presently, only recursion depth of 1 is
27952 permitted. If this option is present, then every reported thread group
27953 will also include its children, either as @samp{group} or
27954 @samp{threads} field.
27956 In general, any combination of option and parameters is permitted, with
27957 the following caveats:
27961 When a single thread group is passed, the output will typically
27962 be the @samp{threads} result. Because threads may not contain
27963 anything, the @samp{recurse} option will be ignored.
27966 When the @samp{--available} option is passed, limited information may
27967 be available. In particular, the list of threads of a process might
27968 be inaccessible. Further, specifying specific thread groups might
27969 not give any performance advantage over listing all thread groups.
27970 The frontend should assume that @samp{-list-thread-groups --available}
27971 is always an expensive operation and cache the results.
27975 The @samp{groups} result is a list of tuples, where each tuple may
27976 have the following fields:
27980 Identifier of the thread group. This field is always present.
27981 The identifier is an opaque string; frontends should not try to
27982 convert it to an integer, even though it might look like one.
27985 The type of the thread group. At present, only @samp{process} is a
27989 The target-specific process identifier. This field is only present
27990 for thread groups of type @samp{process} and only if the process exists.
27993 The number of children this thread group has. This field may be
27994 absent for an available thread group.
27997 This field has a list of tuples as value, each tuple describing a
27998 thread. It may be present if the @samp{--recurse} option is
27999 specified, and it's actually possible to obtain the threads.
28002 This field is a list of integers, each identifying a core that one
28003 thread of the group is running on. This field may be absent if
28004 such information is not available.
28007 The name of the executable file that corresponds to this thread group.
28008 The field is only present for thread groups of type @samp{process},
28009 and only if there is a corresponding executable file.
28013 @subheading Example
28017 -list-thread-groups
28018 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
28019 -list-thread-groups 17
28020 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28021 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
28022 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28023 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
28024 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
28025 -list-thread-groups --available
28026 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
28027 -list-thread-groups --available --recurse 1
28028 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28029 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28030 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
28031 -list-thread-groups --available --recurse 1 17 18
28032 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28033 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28034 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
28038 @subheading The @code{-add-inferior} Command
28039 @findex -add-inferior
28041 @subheading Synopsis
28047 Creates a new inferior (@pxref{Inferiors and Programs}). The created
28048 inferior is not associated with any executable. Such association may
28049 be established with the @samp{-file-exec-and-symbols} command
28050 (@pxref{GDB/MI File Commands}). The command response has a single
28051 field, @samp{thread-group}, whose value is the identifier of the
28052 thread group corresponding to the new inferior.
28054 @subheading Example
28059 ^done,thread-group="i3"
28062 @subheading The @code{-interpreter-exec} Command
28063 @findex -interpreter-exec
28065 @subheading Synopsis
28068 -interpreter-exec @var{interpreter} @var{command}
28070 @anchor{-interpreter-exec}
28072 Execute the specified @var{command} in the given @var{interpreter}.
28074 @subheading @value{GDBN} Command
28076 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
28078 @subheading Example
28082 -interpreter-exec console "break main"
28083 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
28084 &"During symbol reading, bad structure-type format.\n"
28085 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
28090 @subheading The @code{-inferior-tty-set} Command
28091 @findex -inferior-tty-set
28093 @subheading Synopsis
28096 -inferior-tty-set /dev/pts/1
28099 Set terminal for future runs of the program being debugged.
28101 @subheading @value{GDBN} Command
28103 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
28105 @subheading Example
28109 -inferior-tty-set /dev/pts/1
28114 @subheading The @code{-inferior-tty-show} Command
28115 @findex -inferior-tty-show
28117 @subheading Synopsis
28123 Show terminal for future runs of program being debugged.
28125 @subheading @value{GDBN} Command
28127 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
28129 @subheading Example
28133 -inferior-tty-set /dev/pts/1
28137 ^done,inferior_tty_terminal="/dev/pts/1"
28141 @subheading The @code{-enable-timings} Command
28142 @findex -enable-timings
28144 @subheading Synopsis
28147 -enable-timings [yes | no]
28150 Toggle the printing of the wallclock, user and system times for an MI
28151 command as a field in its output. This command is to help frontend
28152 developers optimize the performance of their code. No argument is
28153 equivalent to @samp{yes}.
28155 @subheading @value{GDBN} Command
28159 @subheading Example
28167 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28168 addr="0x080484ed",func="main",file="myprog.c",
28169 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
28170 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
28178 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28179 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
28180 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
28181 fullname="/home/nickrob/myprog.c",line="73"@}
28186 @chapter @value{GDBN} Annotations
28188 This chapter describes annotations in @value{GDBN}. Annotations were
28189 designed to interface @value{GDBN} to graphical user interfaces or other
28190 similar programs which want to interact with @value{GDBN} at a
28191 relatively high level.
28193 The annotation mechanism has largely been superseded by @sc{gdb/mi}
28197 This is Edition @value{EDITION}, @value{DATE}.
28201 * Annotations Overview:: What annotations are; the general syntax.
28202 * Server Prefix:: Issuing a command without affecting user state.
28203 * Prompting:: Annotations marking @value{GDBN}'s need for input.
28204 * Errors:: Annotations for error messages.
28205 * Invalidation:: Some annotations describe things now invalid.
28206 * Annotations for Running::
28207 Whether the program is running, how it stopped, etc.
28208 * Source Annotations:: Annotations describing source code.
28211 @node Annotations Overview
28212 @section What is an Annotation?
28213 @cindex annotations
28215 Annotations start with a newline character, two @samp{control-z}
28216 characters, and the name of the annotation. If there is no additional
28217 information associated with this annotation, the name of the annotation
28218 is followed immediately by a newline. If there is additional
28219 information, the name of the annotation is followed by a space, the
28220 additional information, and a newline. The additional information
28221 cannot contain newline characters.
28223 Any output not beginning with a newline and two @samp{control-z}
28224 characters denotes literal output from @value{GDBN}. Currently there is
28225 no need for @value{GDBN} to output a newline followed by two
28226 @samp{control-z} characters, but if there was such a need, the
28227 annotations could be extended with an @samp{escape} annotation which
28228 means those three characters as output.
28230 The annotation @var{level}, which is specified using the
28231 @option{--annotate} command line option (@pxref{Mode Options}), controls
28232 how much information @value{GDBN} prints together with its prompt,
28233 values of expressions, source lines, and other types of output. Level 0
28234 is for no annotations, level 1 is for use when @value{GDBN} is run as a
28235 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
28236 for programs that control @value{GDBN}, and level 2 annotations have
28237 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
28238 Interface, annotate, GDB's Obsolete Annotations}).
28241 @kindex set annotate
28242 @item set annotate @var{level}
28243 The @value{GDBN} command @code{set annotate} sets the level of
28244 annotations to the specified @var{level}.
28246 @item show annotate
28247 @kindex show annotate
28248 Show the current annotation level.
28251 This chapter describes level 3 annotations.
28253 A simple example of starting up @value{GDBN} with annotations is:
28256 $ @kbd{gdb --annotate=3}
28258 Copyright 2003 Free Software Foundation, Inc.
28259 GDB is free software, covered by the GNU General Public License,
28260 and you are welcome to change it and/or distribute copies of it
28261 under certain conditions.
28262 Type "show copying" to see the conditions.
28263 There is absolutely no warranty for GDB. Type "show warranty"
28265 This GDB was configured as "i386-pc-linux-gnu"
28276 Here @samp{quit} is input to @value{GDBN}; the rest is output from
28277 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
28278 denotes a @samp{control-z} character) are annotations; the rest is
28279 output from @value{GDBN}.
28281 @node Server Prefix
28282 @section The Server Prefix
28283 @cindex server prefix
28285 If you prefix a command with @samp{server } then it will not affect
28286 the command history, nor will it affect @value{GDBN}'s notion of which
28287 command to repeat if @key{RET} is pressed on a line by itself. This
28288 means that commands can be run behind a user's back by a front-end in
28289 a transparent manner.
28291 The @code{server } prefix does not affect the recording of values into
28292 the value history; to print a value without recording it into the
28293 value history, use the @code{output} command instead of the
28294 @code{print} command.
28296 Using this prefix also disables confirmation requests
28297 (@pxref{confirmation requests}).
28300 @section Annotation for @value{GDBN} Input
28302 @cindex annotations for prompts
28303 When @value{GDBN} prompts for input, it annotates this fact so it is possible
28304 to know when to send output, when the output from a given command is
28307 Different kinds of input each have a different @dfn{input type}. Each
28308 input type has three annotations: a @code{pre-} annotation, which
28309 denotes the beginning of any prompt which is being output, a plain
28310 annotation, which denotes the end of the prompt, and then a @code{post-}
28311 annotation which denotes the end of any echo which may (or may not) be
28312 associated with the input. For example, the @code{prompt} input type
28313 features the following annotations:
28321 The input types are
28324 @findex pre-prompt annotation
28325 @findex prompt annotation
28326 @findex post-prompt annotation
28328 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
28330 @findex pre-commands annotation
28331 @findex commands annotation
28332 @findex post-commands annotation
28334 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
28335 command. The annotations are repeated for each command which is input.
28337 @findex pre-overload-choice annotation
28338 @findex overload-choice annotation
28339 @findex post-overload-choice annotation
28340 @item overload-choice
28341 When @value{GDBN} wants the user to select between various overloaded functions.
28343 @findex pre-query annotation
28344 @findex query annotation
28345 @findex post-query annotation
28347 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
28349 @findex pre-prompt-for-continue annotation
28350 @findex prompt-for-continue annotation
28351 @findex post-prompt-for-continue annotation
28352 @item prompt-for-continue
28353 When @value{GDBN} is asking the user to press return to continue. Note: Don't
28354 expect this to work well; instead use @code{set height 0} to disable
28355 prompting. This is because the counting of lines is buggy in the
28356 presence of annotations.
28361 @cindex annotations for errors, warnings and interrupts
28363 @findex quit annotation
28368 This annotation occurs right before @value{GDBN} responds to an interrupt.
28370 @findex error annotation
28375 This annotation occurs right before @value{GDBN} responds to an error.
28377 Quit and error annotations indicate that any annotations which @value{GDBN} was
28378 in the middle of may end abruptly. For example, if a
28379 @code{value-history-begin} annotation is followed by a @code{error}, one
28380 cannot expect to receive the matching @code{value-history-end}. One
28381 cannot expect not to receive it either, however; an error annotation
28382 does not necessarily mean that @value{GDBN} is immediately returning all the way
28385 @findex error-begin annotation
28386 A quit or error annotation may be preceded by
28392 Any output between that and the quit or error annotation is the error
28395 Warning messages are not yet annotated.
28396 @c If we want to change that, need to fix warning(), type_error(),
28397 @c range_error(), and possibly other places.
28400 @section Invalidation Notices
28402 @cindex annotations for invalidation messages
28403 The following annotations say that certain pieces of state may have
28407 @findex frames-invalid annotation
28408 @item ^Z^Zframes-invalid
28410 The frames (for example, output from the @code{backtrace} command) may
28413 @findex breakpoints-invalid annotation
28414 @item ^Z^Zbreakpoints-invalid
28416 The breakpoints may have changed. For example, the user just added or
28417 deleted a breakpoint.
28420 @node Annotations for Running
28421 @section Running the Program
28422 @cindex annotations for running programs
28424 @findex starting annotation
28425 @findex stopping annotation
28426 When the program starts executing due to a @value{GDBN} command such as
28427 @code{step} or @code{continue},
28433 is output. When the program stops,
28439 is output. Before the @code{stopped} annotation, a variety of
28440 annotations describe how the program stopped.
28443 @findex exited annotation
28444 @item ^Z^Zexited @var{exit-status}
28445 The program exited, and @var{exit-status} is the exit status (zero for
28446 successful exit, otherwise nonzero).
28448 @findex signalled annotation
28449 @findex signal-name annotation
28450 @findex signal-name-end annotation
28451 @findex signal-string annotation
28452 @findex signal-string-end annotation
28453 @item ^Z^Zsignalled
28454 The program exited with a signal. After the @code{^Z^Zsignalled}, the
28455 annotation continues:
28461 ^Z^Zsignal-name-end
28465 ^Z^Zsignal-string-end
28470 where @var{name} is the name of the signal, such as @code{SIGILL} or
28471 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
28472 as @code{Illegal Instruction} or @code{Segmentation fault}.
28473 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
28474 user's benefit and have no particular format.
28476 @findex signal annotation
28478 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
28479 just saying that the program received the signal, not that it was
28480 terminated with it.
28482 @findex breakpoint annotation
28483 @item ^Z^Zbreakpoint @var{number}
28484 The program hit breakpoint number @var{number}.
28486 @findex watchpoint annotation
28487 @item ^Z^Zwatchpoint @var{number}
28488 The program hit watchpoint number @var{number}.
28491 @node Source Annotations
28492 @section Displaying Source
28493 @cindex annotations for source display
28495 @findex source annotation
28496 The following annotation is used instead of displaying source code:
28499 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
28502 where @var{filename} is an absolute file name indicating which source
28503 file, @var{line} is the line number within that file (where 1 is the
28504 first line in the file), @var{character} is the character position
28505 within the file (where 0 is the first character in the file) (for most
28506 debug formats this will necessarily point to the beginning of a line),
28507 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
28508 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
28509 @var{addr} is the address in the target program associated with the
28510 source which is being displayed. @var{addr} is in the form @samp{0x}
28511 followed by one or more lowercase hex digits (note that this does not
28512 depend on the language).
28514 @node JIT Interface
28515 @chapter JIT Compilation Interface
28516 @cindex just-in-time compilation
28517 @cindex JIT compilation interface
28519 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
28520 interface. A JIT compiler is a program or library that generates native
28521 executable code at runtime and executes it, usually in order to achieve good
28522 performance while maintaining platform independence.
28524 Programs that use JIT compilation are normally difficult to debug because
28525 portions of their code are generated at runtime, instead of being loaded from
28526 object files, which is where @value{GDBN} normally finds the program's symbols
28527 and debug information. In order to debug programs that use JIT compilation,
28528 @value{GDBN} has an interface that allows the program to register in-memory
28529 symbol files with @value{GDBN} at runtime.
28531 If you are using @value{GDBN} to debug a program that uses this interface, then
28532 it should work transparently so long as you have not stripped the binary. If
28533 you are developing a JIT compiler, then the interface is documented in the rest
28534 of this chapter. At this time, the only known client of this interface is the
28537 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
28538 JIT compiler communicates with @value{GDBN} by writing data into a global
28539 variable and calling a fuction at a well-known symbol. When @value{GDBN}
28540 attaches, it reads a linked list of symbol files from the global variable to
28541 find existing code, and puts a breakpoint in the function so that it can find
28542 out about additional code.
28545 * Declarations:: Relevant C struct declarations
28546 * Registering Code:: Steps to register code
28547 * Unregistering Code:: Steps to unregister code
28551 @section JIT Declarations
28553 These are the relevant struct declarations that a C program should include to
28554 implement the interface:
28564 struct jit_code_entry
28566 struct jit_code_entry *next_entry;
28567 struct jit_code_entry *prev_entry;
28568 const char *symfile_addr;
28569 uint64_t symfile_size;
28572 struct jit_descriptor
28575 /* This type should be jit_actions_t, but we use uint32_t
28576 to be explicit about the bitwidth. */
28577 uint32_t action_flag;
28578 struct jit_code_entry *relevant_entry;
28579 struct jit_code_entry *first_entry;
28582 /* GDB puts a breakpoint in this function. */
28583 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
28585 /* Make sure to specify the version statically, because the
28586 debugger may check the version before we can set it. */
28587 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
28590 If the JIT is multi-threaded, then it is important that the JIT synchronize any
28591 modifications to this global data properly, which can easily be done by putting
28592 a global mutex around modifications to these structures.
28594 @node Registering Code
28595 @section Registering Code
28597 To register code with @value{GDBN}, the JIT should follow this protocol:
28601 Generate an object file in memory with symbols and other desired debug
28602 information. The file must include the virtual addresses of the sections.
28605 Create a code entry for the file, which gives the start and size of the symbol
28609 Add it to the linked list in the JIT descriptor.
28612 Point the relevant_entry field of the descriptor at the entry.
28615 Set @code{action_flag} to @code{JIT_REGISTER} and call
28616 @code{__jit_debug_register_code}.
28619 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
28620 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
28621 new code. However, the linked list must still be maintained in order to allow
28622 @value{GDBN} to attach to a running process and still find the symbol files.
28624 @node Unregistering Code
28625 @section Unregistering Code
28627 If code is freed, then the JIT should use the following protocol:
28631 Remove the code entry corresponding to the code from the linked list.
28634 Point the @code{relevant_entry} field of the descriptor at the code entry.
28637 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
28638 @code{__jit_debug_register_code}.
28641 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
28642 and the JIT will leak the memory used for the associated symbol files.
28645 @chapter Reporting Bugs in @value{GDBN}
28646 @cindex bugs in @value{GDBN}
28647 @cindex reporting bugs in @value{GDBN}
28649 Your bug reports play an essential role in making @value{GDBN} reliable.
28651 Reporting a bug may help you by bringing a solution to your problem, or it
28652 may not. But in any case the principal function of a bug report is to help
28653 the entire community by making the next version of @value{GDBN} work better. Bug
28654 reports are your contribution to the maintenance of @value{GDBN}.
28656 In order for a bug report to serve its purpose, you must include the
28657 information that enables us to fix the bug.
28660 * Bug Criteria:: Have you found a bug?
28661 * Bug Reporting:: How to report bugs
28665 @section Have You Found a Bug?
28666 @cindex bug criteria
28668 If you are not sure whether you have found a bug, here are some guidelines:
28671 @cindex fatal signal
28672 @cindex debugger crash
28673 @cindex crash of debugger
28675 If the debugger gets a fatal signal, for any input whatever, that is a
28676 @value{GDBN} bug. Reliable debuggers never crash.
28678 @cindex error on valid input
28680 If @value{GDBN} produces an error message for valid input, that is a
28681 bug. (Note that if you're cross debugging, the problem may also be
28682 somewhere in the connection to the target.)
28684 @cindex invalid input
28686 If @value{GDBN} does not produce an error message for invalid input,
28687 that is a bug. However, you should note that your idea of
28688 ``invalid input'' might be our idea of ``an extension'' or ``support
28689 for traditional practice''.
28692 If you are an experienced user of debugging tools, your suggestions
28693 for improvement of @value{GDBN} are welcome in any case.
28696 @node Bug Reporting
28697 @section How to Report Bugs
28698 @cindex bug reports
28699 @cindex @value{GDBN} bugs, reporting
28701 A number of companies and individuals offer support for @sc{gnu} products.
28702 If you obtained @value{GDBN} from a support organization, we recommend you
28703 contact that organization first.
28705 You can find contact information for many support companies and
28706 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
28708 @c should add a web page ref...
28711 @ifset BUGURL_DEFAULT
28712 In any event, we also recommend that you submit bug reports for
28713 @value{GDBN}. The preferred method is to submit them directly using
28714 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
28715 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
28718 @strong{Do not send bug reports to @samp{info-gdb}, or to
28719 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
28720 not want to receive bug reports. Those that do have arranged to receive
28723 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
28724 serves as a repeater. The mailing list and the newsgroup carry exactly
28725 the same messages. Often people think of posting bug reports to the
28726 newsgroup instead of mailing them. This appears to work, but it has one
28727 problem which can be crucial: a newsgroup posting often lacks a mail
28728 path back to the sender. Thus, if we need to ask for more information,
28729 we may be unable to reach you. For this reason, it is better to send
28730 bug reports to the mailing list.
28732 @ifclear BUGURL_DEFAULT
28733 In any event, we also recommend that you submit bug reports for
28734 @value{GDBN} to @value{BUGURL}.
28738 The fundamental principle of reporting bugs usefully is this:
28739 @strong{report all the facts}. If you are not sure whether to state a
28740 fact or leave it out, state it!
28742 Often people omit facts because they think they know what causes the
28743 problem and assume that some details do not matter. Thus, you might
28744 assume that the name of the variable you use in an example does not matter.
28745 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
28746 stray memory reference which happens to fetch from the location where that
28747 name is stored in memory; perhaps, if the name were different, the contents
28748 of that location would fool the debugger into doing the right thing despite
28749 the bug. Play it safe and give a specific, complete example. That is the
28750 easiest thing for you to do, and the most helpful.
28752 Keep in mind that the purpose of a bug report is to enable us to fix the
28753 bug. It may be that the bug has been reported previously, but neither
28754 you nor we can know that unless your bug report is complete and
28757 Sometimes people give a few sketchy facts and ask, ``Does this ring a
28758 bell?'' Those bug reports are useless, and we urge everyone to
28759 @emph{refuse to respond to them} except to chide the sender to report
28762 To enable us to fix the bug, you should include all these things:
28766 The version of @value{GDBN}. @value{GDBN} announces it if you start
28767 with no arguments; you can also print it at any time using @code{show
28770 Without this, we will not know whether there is any point in looking for
28771 the bug in the current version of @value{GDBN}.
28774 The type of machine you are using, and the operating system name and
28778 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
28779 ``@value{GCC}--2.8.1''.
28782 What compiler (and its version) was used to compile the program you are
28783 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
28784 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
28785 to get this information; for other compilers, see the documentation for
28789 The command arguments you gave the compiler to compile your example and
28790 observe the bug. For example, did you use @samp{-O}? To guarantee
28791 you will not omit something important, list them all. A copy of the
28792 Makefile (or the output from make) is sufficient.
28794 If we were to try to guess the arguments, we would probably guess wrong
28795 and then we might not encounter the bug.
28798 A complete input script, and all necessary source files, that will
28802 A description of what behavior you observe that you believe is
28803 incorrect. For example, ``It gets a fatal signal.''
28805 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
28806 will certainly notice it. But if the bug is incorrect output, we might
28807 not notice unless it is glaringly wrong. You might as well not give us
28808 a chance to make a mistake.
28810 Even if the problem you experience is a fatal signal, you should still
28811 say so explicitly. Suppose something strange is going on, such as, your
28812 copy of @value{GDBN} is out of synch, or you have encountered a bug in
28813 the C library on your system. (This has happened!) Your copy might
28814 crash and ours would not. If you told us to expect a crash, then when
28815 ours fails to crash, we would know that the bug was not happening for
28816 us. If you had not told us to expect a crash, then we would not be able
28817 to draw any conclusion from our observations.
28820 @cindex recording a session script
28821 To collect all this information, you can use a session recording program
28822 such as @command{script}, which is available on many Unix systems.
28823 Just run your @value{GDBN} session inside @command{script} and then
28824 include the @file{typescript} file with your bug report.
28826 Another way to record a @value{GDBN} session is to run @value{GDBN}
28827 inside Emacs and then save the entire buffer to a file.
28830 If you wish to suggest changes to the @value{GDBN} source, send us context
28831 diffs. If you even discuss something in the @value{GDBN} source, refer to
28832 it by context, not by line number.
28834 The line numbers in our development sources will not match those in your
28835 sources. Your line numbers would convey no useful information to us.
28839 Here are some things that are not necessary:
28843 A description of the envelope of the bug.
28845 Often people who encounter a bug spend a lot of time investigating
28846 which changes to the input file will make the bug go away and which
28847 changes will not affect it.
28849 This is often time consuming and not very useful, because the way we
28850 will find the bug is by running a single example under the debugger
28851 with breakpoints, not by pure deduction from a series of examples.
28852 We recommend that you save your time for something else.
28854 Of course, if you can find a simpler example to report @emph{instead}
28855 of the original one, that is a convenience for us. Errors in the
28856 output will be easier to spot, running under the debugger will take
28857 less time, and so on.
28859 However, simplification is not vital; if you do not want to do this,
28860 report the bug anyway and send us the entire test case you used.
28863 A patch for the bug.
28865 A patch for the bug does help us if it is a good one. But do not omit
28866 the necessary information, such as the test case, on the assumption that
28867 a patch is all we need. We might see problems with your patch and decide
28868 to fix the problem another way, or we might not understand it at all.
28870 Sometimes with a program as complicated as @value{GDBN} it is very hard to
28871 construct an example that will make the program follow a certain path
28872 through the code. If you do not send us the example, we will not be able
28873 to construct one, so we will not be able to verify that the bug is fixed.
28875 And if we cannot understand what bug you are trying to fix, or why your
28876 patch should be an improvement, we will not install it. A test case will
28877 help us to understand.
28880 A guess about what the bug is or what it depends on.
28882 Such guesses are usually wrong. Even we cannot guess right about such
28883 things without first using the debugger to find the facts.
28886 @c The readline documentation is distributed with the readline code
28887 @c and consists of the two following files:
28889 @c inc-hist.texinfo
28890 @c Use -I with makeinfo to point to the appropriate directory,
28891 @c environment var TEXINPUTS with TeX.
28892 @include rluser.texi
28893 @include inc-hist.texinfo
28896 @node Formatting Documentation
28897 @appendix Formatting Documentation
28899 @cindex @value{GDBN} reference card
28900 @cindex reference card
28901 The @value{GDBN} 4 release includes an already-formatted reference card, ready
28902 for printing with PostScript or Ghostscript, in the @file{gdb}
28903 subdirectory of the main source directory@footnote{In
28904 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
28905 release.}. If you can use PostScript or Ghostscript with your printer,
28906 you can print the reference card immediately with @file{refcard.ps}.
28908 The release also includes the source for the reference card. You
28909 can format it, using @TeX{}, by typing:
28915 The @value{GDBN} reference card is designed to print in @dfn{landscape}
28916 mode on US ``letter'' size paper;
28917 that is, on a sheet 11 inches wide by 8.5 inches
28918 high. You will need to specify this form of printing as an option to
28919 your @sc{dvi} output program.
28921 @cindex documentation
28923 All the documentation for @value{GDBN} comes as part of the machine-readable
28924 distribution. The documentation is written in Texinfo format, which is
28925 a documentation system that uses a single source file to produce both
28926 on-line information and a printed manual. You can use one of the Info
28927 formatting commands to create the on-line version of the documentation
28928 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
28930 @value{GDBN} includes an already formatted copy of the on-line Info
28931 version of this manual in the @file{gdb} subdirectory. The main Info
28932 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
28933 subordinate files matching @samp{gdb.info*} in the same directory. If
28934 necessary, you can print out these files, or read them with any editor;
28935 but they are easier to read using the @code{info} subsystem in @sc{gnu}
28936 Emacs or the standalone @code{info} program, available as part of the
28937 @sc{gnu} Texinfo distribution.
28939 If you want to format these Info files yourself, you need one of the
28940 Info formatting programs, such as @code{texinfo-format-buffer} or
28943 If you have @code{makeinfo} installed, and are in the top level
28944 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
28945 version @value{GDBVN}), you can make the Info file by typing:
28952 If you want to typeset and print copies of this manual, you need @TeX{},
28953 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
28954 Texinfo definitions file.
28956 @TeX{} is a typesetting program; it does not print files directly, but
28957 produces output files called @sc{dvi} files. To print a typeset
28958 document, you need a program to print @sc{dvi} files. If your system
28959 has @TeX{} installed, chances are it has such a program. The precise
28960 command to use depends on your system; @kbd{lpr -d} is common; another
28961 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
28962 require a file name without any extension or a @samp{.dvi} extension.
28964 @TeX{} also requires a macro definitions file called
28965 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
28966 written in Texinfo format. On its own, @TeX{} cannot either read or
28967 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
28968 and is located in the @file{gdb-@var{version-number}/texinfo}
28971 If you have @TeX{} and a @sc{dvi} printer program installed, you can
28972 typeset and print this manual. First switch to the @file{gdb}
28973 subdirectory of the main source directory (for example, to
28974 @file{gdb-@value{GDBVN}/gdb}) and type:
28980 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
28982 @node Installing GDB
28983 @appendix Installing @value{GDBN}
28984 @cindex installation
28987 * Requirements:: Requirements for building @value{GDBN}
28988 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
28989 * Separate Objdir:: Compiling @value{GDBN} in another directory
28990 * Config Names:: Specifying names for hosts and targets
28991 * Configure Options:: Summary of options for configure
28992 * System-wide configuration:: Having a system-wide init file
28996 @section Requirements for Building @value{GDBN}
28997 @cindex building @value{GDBN}, requirements for
28999 Building @value{GDBN} requires various tools and packages to be available.
29000 Other packages will be used only if they are found.
29002 @heading Tools/Packages Necessary for Building @value{GDBN}
29004 @item ISO C90 compiler
29005 @value{GDBN} is written in ISO C90. It should be buildable with any
29006 working C90 compiler, e.g.@: GCC.
29010 @heading Tools/Packages Optional for Building @value{GDBN}
29014 @value{GDBN} can use the Expat XML parsing library. This library may be
29015 included with your operating system distribution; if it is not, you
29016 can get the latest version from @url{http://expat.sourceforge.net}.
29017 The @file{configure} script will search for this library in several
29018 standard locations; if it is installed in an unusual path, you can
29019 use the @option{--with-libexpat-prefix} option to specify its location.
29025 Remote protocol memory maps (@pxref{Memory Map Format})
29027 Target descriptions (@pxref{Target Descriptions})
29029 Remote shared library lists (@pxref{Library List Format})
29031 MS-Windows shared libraries (@pxref{Shared Libraries})
29035 @cindex compressed debug sections
29036 @value{GDBN} will use the @samp{zlib} library, if available, to read
29037 compressed debug sections. Some linkers, such as GNU gold, are capable
29038 of producing binaries with compressed debug sections. If @value{GDBN}
29039 is compiled with @samp{zlib}, it will be able to read the debug
29040 information in such binaries.
29042 The @samp{zlib} library is likely included with your operating system
29043 distribution; if it is not, you can get the latest version from
29044 @url{http://zlib.net}.
29047 @value{GDBN}'s features related to character sets (@pxref{Character
29048 Sets}) require a functioning @code{iconv} implementation. If you are
29049 on a GNU system, then this is provided by the GNU C Library. Some
29050 other systems also provide a working @code{iconv}.
29052 On systems with @code{iconv}, you can install GNU Libiconv. If you
29053 have previously installed Libiconv, you can use the
29054 @option{--with-libiconv-prefix} option to configure.
29056 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
29057 arrange to build Libiconv if a directory named @file{libiconv} appears
29058 in the top-most source directory. If Libiconv is built this way, and
29059 if the operating system does not provide a suitable @code{iconv}
29060 implementation, then the just-built library will automatically be used
29061 by @value{GDBN}. One easy way to set this up is to download GNU
29062 Libiconv, unpack it, and then rename the directory holding the
29063 Libiconv source code to @samp{libiconv}.
29066 @node Running Configure
29067 @section Invoking the @value{GDBN} @file{configure} Script
29068 @cindex configuring @value{GDBN}
29069 @value{GDBN} comes with a @file{configure} script that automates the process
29070 of preparing @value{GDBN} for installation; you can then use @code{make} to
29071 build the @code{gdb} program.
29073 @c irrelevant in info file; it's as current as the code it lives with.
29074 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
29075 look at the @file{README} file in the sources; we may have improved the
29076 installation procedures since publishing this manual.}
29079 The @value{GDBN} distribution includes all the source code you need for
29080 @value{GDBN} in a single directory, whose name is usually composed by
29081 appending the version number to @samp{gdb}.
29083 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
29084 @file{gdb-@value{GDBVN}} directory. That directory contains:
29087 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
29088 script for configuring @value{GDBN} and all its supporting libraries
29090 @item gdb-@value{GDBVN}/gdb
29091 the source specific to @value{GDBN} itself
29093 @item gdb-@value{GDBVN}/bfd
29094 source for the Binary File Descriptor library
29096 @item gdb-@value{GDBVN}/include
29097 @sc{gnu} include files
29099 @item gdb-@value{GDBVN}/libiberty
29100 source for the @samp{-liberty} free software library
29102 @item gdb-@value{GDBVN}/opcodes
29103 source for the library of opcode tables and disassemblers
29105 @item gdb-@value{GDBVN}/readline
29106 source for the @sc{gnu} command-line interface
29108 @item gdb-@value{GDBVN}/glob
29109 source for the @sc{gnu} filename pattern-matching subroutine
29111 @item gdb-@value{GDBVN}/mmalloc
29112 source for the @sc{gnu} memory-mapped malloc package
29115 The simplest way to configure and build @value{GDBN} is to run @file{configure}
29116 from the @file{gdb-@var{version-number}} source directory, which in
29117 this example is the @file{gdb-@value{GDBVN}} directory.
29119 First switch to the @file{gdb-@var{version-number}} source directory
29120 if you are not already in it; then run @file{configure}. Pass the
29121 identifier for the platform on which @value{GDBN} will run as an
29127 cd gdb-@value{GDBVN}
29128 ./configure @var{host}
29133 where @var{host} is an identifier such as @samp{sun4} or
29134 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
29135 (You can often leave off @var{host}; @file{configure} tries to guess the
29136 correct value by examining your system.)
29138 Running @samp{configure @var{host}} and then running @code{make} builds the
29139 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
29140 libraries, then @code{gdb} itself. The configured source files, and the
29141 binaries, are left in the corresponding source directories.
29144 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
29145 system does not recognize this automatically when you run a different
29146 shell, you may need to run @code{sh} on it explicitly:
29149 sh configure @var{host}
29152 If you run @file{configure} from a directory that contains source
29153 directories for multiple libraries or programs, such as the
29154 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
29156 creates configuration files for every directory level underneath (unless
29157 you tell it not to, with the @samp{--norecursion} option).
29159 You should run the @file{configure} script from the top directory in the
29160 source tree, the @file{gdb-@var{version-number}} directory. If you run
29161 @file{configure} from one of the subdirectories, you will configure only
29162 that subdirectory. That is usually not what you want. In particular,
29163 if you run the first @file{configure} from the @file{gdb} subdirectory
29164 of the @file{gdb-@var{version-number}} directory, you will omit the
29165 configuration of @file{bfd}, @file{readline}, and other sibling
29166 directories of the @file{gdb} subdirectory. This leads to build errors
29167 about missing include files such as @file{bfd/bfd.h}.
29169 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
29170 However, you should make sure that the shell on your path (named by
29171 the @samp{SHELL} environment variable) is publicly readable. Remember
29172 that @value{GDBN} uses the shell to start your program---some systems refuse to
29173 let @value{GDBN} debug child processes whose programs are not readable.
29175 @node Separate Objdir
29176 @section Compiling @value{GDBN} in Another Directory
29178 If you want to run @value{GDBN} versions for several host or target machines,
29179 you need a different @code{gdb} compiled for each combination of
29180 host and target. @file{configure} is designed to make this easy by
29181 allowing you to generate each configuration in a separate subdirectory,
29182 rather than in the source directory. If your @code{make} program
29183 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
29184 @code{make} in each of these directories builds the @code{gdb}
29185 program specified there.
29187 To build @code{gdb} in a separate directory, run @file{configure}
29188 with the @samp{--srcdir} option to specify where to find the source.
29189 (You also need to specify a path to find @file{configure}
29190 itself from your working directory. If the path to @file{configure}
29191 would be the same as the argument to @samp{--srcdir}, you can leave out
29192 the @samp{--srcdir} option; it is assumed.)
29194 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
29195 separate directory for a Sun 4 like this:
29199 cd gdb-@value{GDBVN}
29202 ../gdb-@value{GDBVN}/configure sun4
29207 When @file{configure} builds a configuration using a remote source
29208 directory, it creates a tree for the binaries with the same structure
29209 (and using the same names) as the tree under the source directory. In
29210 the example, you'd find the Sun 4 library @file{libiberty.a} in the
29211 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
29212 @file{gdb-sun4/gdb}.
29214 Make sure that your path to the @file{configure} script has just one
29215 instance of @file{gdb} in it. If your path to @file{configure} looks
29216 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
29217 one subdirectory of @value{GDBN}, not the whole package. This leads to
29218 build errors about missing include files such as @file{bfd/bfd.h}.
29220 One popular reason to build several @value{GDBN} configurations in separate
29221 directories is to configure @value{GDBN} for cross-compiling (where
29222 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
29223 programs that run on another machine---the @dfn{target}).
29224 You specify a cross-debugging target by
29225 giving the @samp{--target=@var{target}} option to @file{configure}.
29227 When you run @code{make} to build a program or library, you must run
29228 it in a configured directory---whatever directory you were in when you
29229 called @file{configure} (or one of its subdirectories).
29231 The @code{Makefile} that @file{configure} generates in each source
29232 directory also runs recursively. If you type @code{make} in a source
29233 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
29234 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
29235 will build all the required libraries, and then build GDB.
29237 When you have multiple hosts or targets configured in separate
29238 directories, you can run @code{make} on them in parallel (for example,
29239 if they are NFS-mounted on each of the hosts); they will not interfere
29243 @section Specifying Names for Hosts and Targets
29245 The specifications used for hosts and targets in the @file{configure}
29246 script are based on a three-part naming scheme, but some short predefined
29247 aliases are also supported. The full naming scheme encodes three pieces
29248 of information in the following pattern:
29251 @var{architecture}-@var{vendor}-@var{os}
29254 For example, you can use the alias @code{sun4} as a @var{host} argument,
29255 or as the value for @var{target} in a @code{--target=@var{target}}
29256 option. The equivalent full name is @samp{sparc-sun-sunos4}.
29258 The @file{configure} script accompanying @value{GDBN} does not provide
29259 any query facility to list all supported host and target names or
29260 aliases. @file{configure} calls the Bourne shell script
29261 @code{config.sub} to map abbreviations to full names; you can read the
29262 script, if you wish, or you can use it to test your guesses on
29263 abbreviations---for example:
29266 % sh config.sub i386-linux
29268 % sh config.sub alpha-linux
29269 alpha-unknown-linux-gnu
29270 % sh config.sub hp9k700
29272 % sh config.sub sun4
29273 sparc-sun-sunos4.1.1
29274 % sh config.sub sun3
29275 m68k-sun-sunos4.1.1
29276 % sh config.sub i986v
29277 Invalid configuration `i986v': machine `i986v' not recognized
29281 @code{config.sub} is also distributed in the @value{GDBN} source
29282 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
29284 @node Configure Options
29285 @section @file{configure} Options
29287 Here is a summary of the @file{configure} options and arguments that
29288 are most often useful for building @value{GDBN}. @file{configure} also has
29289 several other options not listed here. @inforef{What Configure
29290 Does,,configure.info}, for a full explanation of @file{configure}.
29293 configure @r{[}--help@r{]}
29294 @r{[}--prefix=@var{dir}@r{]}
29295 @r{[}--exec-prefix=@var{dir}@r{]}
29296 @r{[}--srcdir=@var{dirname}@r{]}
29297 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
29298 @r{[}--target=@var{target}@r{]}
29303 You may introduce options with a single @samp{-} rather than
29304 @samp{--} if you prefer; but you may abbreviate option names if you use
29309 Display a quick summary of how to invoke @file{configure}.
29311 @item --prefix=@var{dir}
29312 Configure the source to install programs and files under directory
29315 @item --exec-prefix=@var{dir}
29316 Configure the source to install programs under directory
29319 @c avoid splitting the warning from the explanation:
29321 @item --srcdir=@var{dirname}
29322 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
29323 @code{make} that implements the @code{VPATH} feature.}@*
29324 Use this option to make configurations in directories separate from the
29325 @value{GDBN} source directories. Among other things, you can use this to
29326 build (or maintain) several configurations simultaneously, in separate
29327 directories. @file{configure} writes configuration-specific files in
29328 the current directory, but arranges for them to use the source in the
29329 directory @var{dirname}. @file{configure} creates directories under
29330 the working directory in parallel to the source directories below
29333 @item --norecursion
29334 Configure only the directory level where @file{configure} is executed; do not
29335 propagate configuration to subdirectories.
29337 @item --target=@var{target}
29338 Configure @value{GDBN} for cross-debugging programs running on the specified
29339 @var{target}. Without this option, @value{GDBN} is configured to debug
29340 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
29342 There is no convenient way to generate a list of all available targets.
29344 @item @var{host} @dots{}
29345 Configure @value{GDBN} to run on the specified @var{host}.
29347 There is no convenient way to generate a list of all available hosts.
29350 There are many other options available as well, but they are generally
29351 needed for special purposes only.
29353 @node System-wide configuration
29354 @section System-wide configuration and settings
29355 @cindex system-wide init file
29357 @value{GDBN} can be configured to have a system-wide init file;
29358 this file will be read and executed at startup (@pxref{Startup, , What
29359 @value{GDBN} does during startup}).
29361 Here is the corresponding configure option:
29364 @item --with-system-gdbinit=@var{file}
29365 Specify that the default location of the system-wide init file is
29369 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
29370 it may be subject to relocation. Two possible cases:
29374 If the default location of this init file contains @file{$prefix},
29375 it will be subject to relocation. Suppose that the configure options
29376 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
29377 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
29378 init file is looked for as @file{$install/etc/gdbinit} instead of
29379 @file{$prefix/etc/gdbinit}.
29382 By contrast, if the default location does not contain the prefix,
29383 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
29384 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
29385 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
29386 wherever @value{GDBN} is installed.
29389 @node Maintenance Commands
29390 @appendix Maintenance Commands
29391 @cindex maintenance commands
29392 @cindex internal commands
29394 In addition to commands intended for @value{GDBN} users, @value{GDBN}
29395 includes a number of commands intended for @value{GDBN} developers,
29396 that are not documented elsewhere in this manual. These commands are
29397 provided here for reference. (For commands that turn on debugging
29398 messages, see @ref{Debugging Output}.)
29401 @kindex maint agent
29402 @kindex maint agent-eval
29403 @item maint agent @var{expression}
29404 @itemx maint agent-eval @var{expression}
29405 Translate the given @var{expression} into remote agent bytecodes.
29406 This command is useful for debugging the Agent Expression mechanism
29407 (@pxref{Agent Expressions}). The @samp{agent} version produces an
29408 expression useful for data collection, such as by tracepoints, while
29409 @samp{maint agent-eval} produces an expression that evaluates directly
29410 to a result. For instance, a collection expression for @code{globa +
29411 globb} will include bytecodes to record four bytes of memory at each
29412 of the addresses of @code{globa} and @code{globb}, while discarding
29413 the result of the addition, while an evaluation expression will do the
29414 addition and return the sum.
29416 @kindex maint info breakpoints
29417 @item @anchor{maint info breakpoints}maint info breakpoints
29418 Using the same format as @samp{info breakpoints}, display both the
29419 breakpoints you've set explicitly, and those @value{GDBN} is using for
29420 internal purposes. Internal breakpoints are shown with negative
29421 breakpoint numbers. The type column identifies what kind of breakpoint
29426 Normal, explicitly set breakpoint.
29429 Normal, explicitly set watchpoint.
29432 Internal breakpoint, used to handle correctly stepping through
29433 @code{longjmp} calls.
29435 @item longjmp resume
29436 Internal breakpoint at the target of a @code{longjmp}.
29439 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
29442 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
29445 Shared library events.
29449 @kindex set displaced-stepping
29450 @kindex show displaced-stepping
29451 @cindex displaced stepping support
29452 @cindex out-of-line single-stepping
29453 @item set displaced-stepping
29454 @itemx show displaced-stepping
29455 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
29456 if the target supports it. Displaced stepping is a way to single-step
29457 over breakpoints without removing them from the inferior, by executing
29458 an out-of-line copy of the instruction that was originally at the
29459 breakpoint location. It is also known as out-of-line single-stepping.
29462 @item set displaced-stepping on
29463 If the target architecture supports it, @value{GDBN} will use
29464 displaced stepping to step over breakpoints.
29466 @item set displaced-stepping off
29467 @value{GDBN} will not use displaced stepping to step over breakpoints,
29468 even if such is supported by the target architecture.
29470 @cindex non-stop mode, and @samp{set displaced-stepping}
29471 @item set displaced-stepping auto
29472 This is the default mode. @value{GDBN} will use displaced stepping
29473 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
29474 architecture supports displaced stepping.
29477 @kindex maint check-symtabs
29478 @item maint check-symtabs
29479 Check the consistency of psymtabs and symtabs.
29481 @kindex maint cplus first_component
29482 @item maint cplus first_component @var{name}
29483 Print the first C@t{++} class/namespace component of @var{name}.
29485 @kindex maint cplus namespace
29486 @item maint cplus namespace
29487 Print the list of possible C@t{++} namespaces.
29489 @kindex maint demangle
29490 @item maint demangle @var{name}
29491 Demangle a C@t{++} or Objective-C mangled @var{name}.
29493 @kindex maint deprecate
29494 @kindex maint undeprecate
29495 @cindex deprecated commands
29496 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
29497 @itemx maint undeprecate @var{command}
29498 Deprecate or undeprecate the named @var{command}. Deprecated commands
29499 cause @value{GDBN} to issue a warning when you use them. The optional
29500 argument @var{replacement} says which newer command should be used in
29501 favor of the deprecated one; if it is given, @value{GDBN} will mention
29502 the replacement as part of the warning.
29504 @kindex maint dump-me
29505 @item maint dump-me
29506 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
29507 Cause a fatal signal in the debugger and force it to dump its core.
29508 This is supported only on systems which support aborting a program
29509 with the @code{SIGQUIT} signal.
29511 @kindex maint internal-error
29512 @kindex maint internal-warning
29513 @item maint internal-error @r{[}@var{message-text}@r{]}
29514 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
29515 Cause @value{GDBN} to call the internal function @code{internal_error}
29516 or @code{internal_warning} and hence behave as though an internal error
29517 or internal warning has been detected. In addition to reporting the
29518 internal problem, these functions give the user the opportunity to
29519 either quit @value{GDBN} or create a core file of the current
29520 @value{GDBN} session.
29522 These commands take an optional parameter @var{message-text} that is
29523 used as the text of the error or warning message.
29525 Here's an example of using @code{internal-error}:
29528 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
29529 @dots{}/maint.c:121: internal-error: testing, 1, 2
29530 A problem internal to GDB has been detected. Further
29531 debugging may prove unreliable.
29532 Quit this debugging session? (y or n) @kbd{n}
29533 Create a core file? (y or n) @kbd{n}
29537 @cindex @value{GDBN} internal error
29538 @cindex internal errors, control of @value{GDBN} behavior
29540 @kindex maint set internal-error
29541 @kindex maint show internal-error
29542 @kindex maint set internal-warning
29543 @kindex maint show internal-warning
29544 @item maint set internal-error @var{action} [ask|yes|no]
29545 @itemx maint show internal-error @var{action}
29546 @itemx maint set internal-warning @var{action} [ask|yes|no]
29547 @itemx maint show internal-warning @var{action}
29548 When @value{GDBN} reports an internal problem (error or warning) it
29549 gives the user the opportunity to both quit @value{GDBN} and create a
29550 core file of the current @value{GDBN} session. These commands let you
29551 override the default behaviour for each particular @var{action},
29552 described in the table below.
29556 You can specify that @value{GDBN} should always (yes) or never (no)
29557 quit. The default is to ask the user what to do.
29560 You can specify that @value{GDBN} should always (yes) or never (no)
29561 create a core file. The default is to ask the user what to do.
29564 @kindex maint packet
29565 @item maint packet @var{text}
29566 If @value{GDBN} is talking to an inferior via the serial protocol,
29567 then this command sends the string @var{text} to the inferior, and
29568 displays the response packet. @value{GDBN} supplies the initial
29569 @samp{$} character, the terminating @samp{#} character, and the
29572 @kindex maint print architecture
29573 @item maint print architecture @r{[}@var{file}@r{]}
29574 Print the entire architecture configuration. The optional argument
29575 @var{file} names the file where the output goes.
29577 @kindex maint print c-tdesc
29578 @item maint print c-tdesc
29579 Print the current target description (@pxref{Target Descriptions}) as
29580 a C source file. The created source file can be used in @value{GDBN}
29581 when an XML parser is not available to parse the description.
29583 @kindex maint print dummy-frames
29584 @item maint print dummy-frames
29585 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
29588 (@value{GDBP}) @kbd{b add}
29590 (@value{GDBP}) @kbd{print add(2,3)}
29591 Breakpoint 2, add (a=2, b=3) at @dots{}
29593 The program being debugged stopped while in a function called from GDB.
29595 (@value{GDBP}) @kbd{maint print dummy-frames}
29596 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
29597 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
29598 call_lo=0x01014000 call_hi=0x01014001
29602 Takes an optional file parameter.
29604 @kindex maint print registers
29605 @kindex maint print raw-registers
29606 @kindex maint print cooked-registers
29607 @kindex maint print register-groups
29608 @item maint print registers @r{[}@var{file}@r{]}
29609 @itemx maint print raw-registers @r{[}@var{file}@r{]}
29610 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
29611 @itemx maint print register-groups @r{[}@var{file}@r{]}
29612 Print @value{GDBN}'s internal register data structures.
29614 The command @code{maint print raw-registers} includes the contents of
29615 the raw register cache; the command @code{maint print cooked-registers}
29616 includes the (cooked) value of all registers, including registers which
29617 aren't available on the target nor visible to user; and the
29618 command @code{maint print register-groups} includes the groups that each
29619 register is a member of. @xref{Registers,, Registers, gdbint,
29620 @value{GDBN} Internals}.
29622 These commands take an optional parameter, a file name to which to
29623 write the information.
29625 @kindex maint print reggroups
29626 @item maint print reggroups @r{[}@var{file}@r{]}
29627 Print @value{GDBN}'s internal register group data structures. The
29628 optional argument @var{file} tells to what file to write the
29631 The register groups info looks like this:
29634 (@value{GDBP}) @kbd{maint print reggroups}
29647 This command forces @value{GDBN} to flush its internal register cache.
29649 @kindex maint print objfiles
29650 @cindex info for known object files
29651 @item maint print objfiles
29652 Print a dump of all known object files. For each object file, this
29653 command prints its name, address in memory, and all of its psymtabs
29656 @kindex maint print section-scripts
29657 @cindex info for known .debug_gdb_scripts-loaded scripts
29658 @item maint print section-scripts [@var{regexp}]
29659 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
29660 If @var{regexp} is specified, only print scripts loaded by object files
29661 matching @var{regexp}.
29662 For each script, this command prints its name as specified in the objfile,
29663 and the full path if known.
29664 @xref{.debug_gdb_scripts section}.
29666 @kindex maint print statistics
29667 @cindex bcache statistics
29668 @item maint print statistics
29669 This command prints, for each object file in the program, various data
29670 about that object file followed by the byte cache (@dfn{bcache})
29671 statistics for the object file. The objfile data includes the number
29672 of minimal, partial, full, and stabs symbols, the number of types
29673 defined by the objfile, the number of as yet unexpanded psym tables,
29674 the number of line tables and string tables, and the amount of memory
29675 used by the various tables. The bcache statistics include the counts,
29676 sizes, and counts of duplicates of all and unique objects, max,
29677 average, and median entry size, total memory used and its overhead and
29678 savings, and various measures of the hash table size and chain
29681 @kindex maint print target-stack
29682 @cindex target stack description
29683 @item maint print target-stack
29684 A @dfn{target} is an interface between the debugger and a particular
29685 kind of file or process. Targets can be stacked in @dfn{strata},
29686 so that more than one target can potentially respond to a request.
29687 In particular, memory accesses will walk down the stack of targets
29688 until they find a target that is interested in handling that particular
29691 This command prints a short description of each layer that was pushed on
29692 the @dfn{target stack}, starting from the top layer down to the bottom one.
29694 @kindex maint print type
29695 @cindex type chain of a data type
29696 @item maint print type @var{expr}
29697 Print the type chain for a type specified by @var{expr}. The argument
29698 can be either a type name or a symbol. If it is a symbol, the type of
29699 that symbol is described. The type chain produced by this command is
29700 a recursive definition of the data type as stored in @value{GDBN}'s
29701 data structures, including its flags and contained types.
29703 @kindex maint set dwarf2 max-cache-age
29704 @kindex maint show dwarf2 max-cache-age
29705 @item maint set dwarf2 max-cache-age
29706 @itemx maint show dwarf2 max-cache-age
29707 Control the DWARF 2 compilation unit cache.
29709 @cindex DWARF 2 compilation units cache
29710 In object files with inter-compilation-unit references, such as those
29711 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
29712 reader needs to frequently refer to previously read compilation units.
29713 This setting controls how long a compilation unit will remain in the
29714 cache if it is not referenced. A higher limit means that cached
29715 compilation units will be stored in memory longer, and more total
29716 memory will be used. Setting it to zero disables caching, which will
29717 slow down @value{GDBN} startup, but reduce memory consumption.
29719 @kindex maint set profile
29720 @kindex maint show profile
29721 @cindex profiling GDB
29722 @item maint set profile
29723 @itemx maint show profile
29724 Control profiling of @value{GDBN}.
29726 Profiling will be disabled until you use the @samp{maint set profile}
29727 command to enable it. When you enable profiling, the system will begin
29728 collecting timing and execution count data; when you disable profiling or
29729 exit @value{GDBN}, the results will be written to a log file. Remember that
29730 if you use profiling, @value{GDBN} will overwrite the profiling log file
29731 (often called @file{gmon.out}). If you have a record of important profiling
29732 data in a @file{gmon.out} file, be sure to move it to a safe location.
29734 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
29735 compiled with the @samp{-pg} compiler option.
29737 @kindex maint set show-debug-regs
29738 @kindex maint show show-debug-regs
29739 @cindex hardware debug registers
29740 @item maint set show-debug-regs
29741 @itemx maint show show-debug-regs
29742 Control whether to show variables that mirror the hardware debug
29743 registers. Use @code{ON} to enable, @code{OFF} to disable. If
29744 enabled, the debug registers values are shown when @value{GDBN} inserts or
29745 removes a hardware breakpoint or watchpoint, and when the inferior
29746 triggers a hardware-assisted breakpoint or watchpoint.
29748 @kindex maint set show-all-tib
29749 @kindex maint show show-all-tib
29750 @item maint set show-all-tib
29751 @itemx maint show show-all-tib
29752 Control whether to show all non zero areas within a 1k block starting
29753 at thread local base, when using the @samp{info w32 thread-information-block}
29756 @kindex maint space
29757 @cindex memory used by commands
29759 Control whether to display memory usage for each command. If set to a
29760 nonzero value, @value{GDBN} will display how much memory each command
29761 took, following the command's own output. This can also be requested
29762 by invoking @value{GDBN} with the @option{--statistics} command-line
29763 switch (@pxref{Mode Options}).
29766 @cindex time of command execution
29768 Control whether to display the execution time for each command. If
29769 set to a nonzero value, @value{GDBN} will display how much time it
29770 took to execute each command, following the command's own output.
29771 The time is not printed for the commands that run the target, since
29772 there's no mechanism currently to compute how much time was spend
29773 by @value{GDBN} and how much time was spend by the program been debugged.
29774 it's not possibly currently
29775 This can also be requested by invoking @value{GDBN} with the
29776 @option{--statistics} command-line switch (@pxref{Mode Options}).
29778 @kindex maint translate-address
29779 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
29780 Find the symbol stored at the location specified by the address
29781 @var{addr} and an optional section name @var{section}. If found,
29782 @value{GDBN} prints the name of the closest symbol and an offset from
29783 the symbol's location to the specified address. This is similar to
29784 the @code{info address} command (@pxref{Symbols}), except that this
29785 command also allows to find symbols in other sections.
29787 If section was not specified, the section in which the symbol was found
29788 is also printed. For dynamically linked executables, the name of
29789 executable or shared library containing the symbol is printed as well.
29793 The following command is useful for non-interactive invocations of
29794 @value{GDBN}, such as in the test suite.
29797 @item set watchdog @var{nsec}
29798 @kindex set watchdog
29799 @cindex watchdog timer
29800 @cindex timeout for commands
29801 Set the maximum number of seconds @value{GDBN} will wait for the
29802 target operation to finish. If this time expires, @value{GDBN}
29803 reports and error and the command is aborted.
29805 @item show watchdog
29806 Show the current setting of the target wait timeout.
29809 @node Remote Protocol
29810 @appendix @value{GDBN} Remote Serial Protocol
29815 * Stop Reply Packets::
29816 * General Query Packets::
29817 * Architecture-Specific Protocol Details::
29818 * Tracepoint Packets::
29819 * Host I/O Packets::
29821 * Notification Packets::
29822 * Remote Non-Stop::
29823 * Packet Acknowledgment::
29825 * File-I/O Remote Protocol Extension::
29826 * Library List Format::
29827 * Memory Map Format::
29828 * Thread List Format::
29834 There may be occasions when you need to know something about the
29835 protocol---for example, if there is only one serial port to your target
29836 machine, you might want your program to do something special if it
29837 recognizes a packet meant for @value{GDBN}.
29839 In the examples below, @samp{->} and @samp{<-} are used to indicate
29840 transmitted and received data, respectively.
29842 @cindex protocol, @value{GDBN} remote serial
29843 @cindex serial protocol, @value{GDBN} remote
29844 @cindex remote serial protocol
29845 All @value{GDBN} commands and responses (other than acknowledgments
29846 and notifications, see @ref{Notification Packets}) are sent as a
29847 @var{packet}. A @var{packet} is introduced with the character
29848 @samp{$}, the actual @var{packet-data}, and the terminating character
29849 @samp{#} followed by a two-digit @var{checksum}:
29852 @code{$}@var{packet-data}@code{#}@var{checksum}
29856 @cindex checksum, for @value{GDBN} remote
29858 The two-digit @var{checksum} is computed as the modulo 256 sum of all
29859 characters between the leading @samp{$} and the trailing @samp{#} (an
29860 eight bit unsigned checksum).
29862 Implementors should note that prior to @value{GDBN} 5.0 the protocol
29863 specification also included an optional two-digit @var{sequence-id}:
29866 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
29869 @cindex sequence-id, for @value{GDBN} remote
29871 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
29872 has never output @var{sequence-id}s. Stubs that handle packets added
29873 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
29875 When either the host or the target machine receives a packet, the first
29876 response expected is an acknowledgment: either @samp{+} (to indicate
29877 the package was received correctly) or @samp{-} (to request
29881 -> @code{$}@var{packet-data}@code{#}@var{checksum}
29886 The @samp{+}/@samp{-} acknowledgments can be disabled
29887 once a connection is established.
29888 @xref{Packet Acknowledgment}, for details.
29890 The host (@value{GDBN}) sends @var{command}s, and the target (the
29891 debugging stub incorporated in your program) sends a @var{response}. In
29892 the case of step and continue @var{command}s, the response is only sent
29893 when the operation has completed, and the target has again stopped all
29894 threads in all attached processes. This is the default all-stop mode
29895 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
29896 execution mode; see @ref{Remote Non-Stop}, for details.
29898 @var{packet-data} consists of a sequence of characters with the
29899 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
29902 @cindex remote protocol, field separator
29903 Fields within the packet should be separated using @samp{,} @samp{;} or
29904 @samp{:}. Except where otherwise noted all numbers are represented in
29905 @sc{hex} with leading zeros suppressed.
29907 Implementors should note that prior to @value{GDBN} 5.0, the character
29908 @samp{:} could not appear as the third character in a packet (as it
29909 would potentially conflict with the @var{sequence-id}).
29911 @cindex remote protocol, binary data
29912 @anchor{Binary Data}
29913 Binary data in most packets is encoded either as two hexadecimal
29914 digits per byte of binary data. This allowed the traditional remote
29915 protocol to work over connections which were only seven-bit clean.
29916 Some packets designed more recently assume an eight-bit clean
29917 connection, and use a more efficient encoding to send and receive
29920 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
29921 as an escape character. Any escaped byte is transmitted as the escape
29922 character followed by the original character XORed with @code{0x20}.
29923 For example, the byte @code{0x7d} would be transmitted as the two
29924 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
29925 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
29926 @samp{@}}) must always be escaped. Responses sent by the stub
29927 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
29928 is not interpreted as the start of a run-length encoded sequence
29931 Response @var{data} can be run-length encoded to save space.
29932 Run-length encoding replaces runs of identical characters with one
29933 instance of the repeated character, followed by a @samp{*} and a
29934 repeat count. The repeat count is itself sent encoded, to avoid
29935 binary characters in @var{data}: a value of @var{n} is sent as
29936 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
29937 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
29938 code 32) for a repeat count of 3. (This is because run-length
29939 encoding starts to win for counts 3 or more.) Thus, for example,
29940 @samp{0* } is a run-length encoding of ``0000'': the space character
29941 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
29944 The printable characters @samp{#} and @samp{$} or with a numeric value
29945 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
29946 seven repeats (@samp{$}) can be expanded using a repeat count of only
29947 five (@samp{"}). For example, @samp{00000000} can be encoded as
29950 The error response returned for some packets includes a two character
29951 error number. That number is not well defined.
29953 @cindex empty response, for unsupported packets
29954 For any @var{command} not supported by the stub, an empty response
29955 (@samp{$#00}) should be returned. That way it is possible to extend the
29956 protocol. A newer @value{GDBN} can tell if a packet is supported based
29959 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
29960 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
29966 The following table provides a complete list of all currently defined
29967 @var{command}s and their corresponding response @var{data}.
29968 @xref{File-I/O Remote Protocol Extension}, for details about the File
29969 I/O extension of the remote protocol.
29971 Each packet's description has a template showing the packet's overall
29972 syntax, followed by an explanation of the packet's meaning. We
29973 include spaces in some of the templates for clarity; these are not
29974 part of the packet's syntax. No @value{GDBN} packet uses spaces to
29975 separate its components. For example, a template like @samp{foo
29976 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
29977 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
29978 @var{baz}. @value{GDBN} does not transmit a space character between the
29979 @samp{foo} and the @var{bar}, or between the @var{bar} and the
29982 @cindex @var{thread-id}, in remote protocol
29983 @anchor{thread-id syntax}
29984 Several packets and replies include a @var{thread-id} field to identify
29985 a thread. Normally these are positive numbers with a target-specific
29986 interpretation, formatted as big-endian hex strings. A @var{thread-id}
29987 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
29990 In addition, the remote protocol supports a multiprocess feature in
29991 which the @var{thread-id} syntax is extended to optionally include both
29992 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
29993 The @var{pid} (process) and @var{tid} (thread) components each have the
29994 format described above: a positive number with target-specific
29995 interpretation formatted as a big-endian hex string, literal @samp{-1}
29996 to indicate all processes or threads (respectively), or @samp{0} to
29997 indicate an arbitrary process or thread. Specifying just a process, as
29998 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
29999 error to specify all processes but a specific thread, such as
30000 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
30001 for those packets and replies explicitly documented to include a process
30002 ID, rather than a @var{thread-id}.
30004 The multiprocess @var{thread-id} syntax extensions are only used if both
30005 @value{GDBN} and the stub report support for the @samp{multiprocess}
30006 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
30009 Note that all packet forms beginning with an upper- or lower-case
30010 letter, other than those described here, are reserved for future use.
30012 Here are the packet descriptions.
30017 @cindex @samp{!} packet
30018 @anchor{extended mode}
30019 Enable extended mode. In extended mode, the remote server is made
30020 persistent. The @samp{R} packet is used to restart the program being
30026 The remote target both supports and has enabled extended mode.
30030 @cindex @samp{?} packet
30031 Indicate the reason the target halted. The reply is the same as for
30032 step and continue. This packet has a special interpretation when the
30033 target is in non-stop mode; see @ref{Remote Non-Stop}.
30036 @xref{Stop Reply Packets}, for the reply specifications.
30038 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
30039 @cindex @samp{A} packet
30040 Initialized @code{argv[]} array passed into program. @var{arglen}
30041 specifies the number of bytes in the hex encoded byte stream
30042 @var{arg}. See @code{gdbserver} for more details.
30047 The arguments were set.
30053 @cindex @samp{b} packet
30054 (Don't use this packet; its behavior is not well-defined.)
30055 Change the serial line speed to @var{baud}.
30057 JTC: @emph{When does the transport layer state change? When it's
30058 received, or after the ACK is transmitted. In either case, there are
30059 problems if the command or the acknowledgment packet is dropped.}
30061 Stan: @emph{If people really wanted to add something like this, and get
30062 it working for the first time, they ought to modify ser-unix.c to send
30063 some kind of out-of-band message to a specially-setup stub and have the
30064 switch happen "in between" packets, so that from remote protocol's point
30065 of view, nothing actually happened.}
30067 @item B @var{addr},@var{mode}
30068 @cindex @samp{B} packet
30069 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
30070 breakpoint at @var{addr}.
30072 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
30073 (@pxref{insert breakpoint or watchpoint packet}).
30075 @cindex @samp{bc} packet
30078 Backward continue. Execute the target system in reverse. No parameter.
30079 @xref{Reverse Execution}, for more information.
30082 @xref{Stop Reply Packets}, for the reply specifications.
30084 @cindex @samp{bs} packet
30087 Backward single step. Execute one instruction in reverse. No parameter.
30088 @xref{Reverse Execution}, for more information.
30091 @xref{Stop Reply Packets}, for the reply specifications.
30093 @item c @r{[}@var{addr}@r{]}
30094 @cindex @samp{c} packet
30095 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
30096 resume at current address.
30099 @xref{Stop Reply Packets}, for the reply specifications.
30101 @item C @var{sig}@r{[};@var{addr}@r{]}
30102 @cindex @samp{C} packet
30103 Continue with signal @var{sig} (hex signal number). If
30104 @samp{;@var{addr}} is omitted, resume at same address.
30107 @xref{Stop Reply Packets}, for the reply specifications.
30110 @cindex @samp{d} packet
30113 Don't use this packet; instead, define a general set packet
30114 (@pxref{General Query Packets}).
30118 @cindex @samp{D} packet
30119 The first form of the packet is used to detach @value{GDBN} from the
30120 remote system. It is sent to the remote target
30121 before @value{GDBN} disconnects via the @code{detach} command.
30123 The second form, including a process ID, is used when multiprocess
30124 protocol extensions are enabled (@pxref{multiprocess extensions}), to
30125 detach only a specific process. The @var{pid} is specified as a
30126 big-endian hex string.
30136 @item F @var{RC},@var{EE},@var{CF};@var{XX}
30137 @cindex @samp{F} packet
30138 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
30139 This is part of the File-I/O protocol extension. @xref{File-I/O
30140 Remote Protocol Extension}, for the specification.
30143 @anchor{read registers packet}
30144 @cindex @samp{g} packet
30145 Read general registers.
30149 @item @var{XX@dots{}}
30150 Each byte of register data is described by two hex digits. The bytes
30151 with the register are transmitted in target byte order. The size of
30152 each register and their position within the @samp{g} packet are
30153 determined by the @value{GDBN} internal gdbarch functions
30154 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
30155 specification of several standard @samp{g} packets is specified below.
30160 @item G @var{XX@dots{}}
30161 @cindex @samp{G} packet
30162 Write general registers. @xref{read registers packet}, for a
30163 description of the @var{XX@dots{}} data.
30173 @item H @var{c} @var{thread-id}
30174 @cindex @samp{H} packet
30175 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
30176 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
30177 should be @samp{c} for step and continue operations, @samp{g} for other
30178 operations. The thread designator @var{thread-id} has the format and
30179 interpretation described in @ref{thread-id syntax}.
30190 @c 'H': How restrictive (or permissive) is the thread model. If a
30191 @c thread is selected and stopped, are other threads allowed
30192 @c to continue to execute? As I mentioned above, I think the
30193 @c semantics of each command when a thread is selected must be
30194 @c described. For example:
30196 @c 'g': If the stub supports threads and a specific thread is
30197 @c selected, returns the register block from that thread;
30198 @c otherwise returns current registers.
30200 @c 'G' If the stub supports threads and a specific thread is
30201 @c selected, sets the registers of the register block of
30202 @c that thread; otherwise sets current registers.
30204 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
30205 @anchor{cycle step packet}
30206 @cindex @samp{i} packet
30207 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
30208 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
30209 step starting at that address.
30212 @cindex @samp{I} packet
30213 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
30217 @cindex @samp{k} packet
30220 FIXME: @emph{There is no description of how to operate when a specific
30221 thread context has been selected (i.e.@: does 'k' kill only that
30224 @item m @var{addr},@var{length}
30225 @cindex @samp{m} packet
30226 Read @var{length} bytes of memory starting at address @var{addr}.
30227 Note that @var{addr} may not be aligned to any particular boundary.
30229 The stub need not use any particular size or alignment when gathering
30230 data from memory for the response; even if @var{addr} is word-aligned
30231 and @var{length} is a multiple of the word size, the stub is free to
30232 use byte accesses, or not. For this reason, this packet may not be
30233 suitable for accessing memory-mapped I/O devices.
30234 @cindex alignment of remote memory accesses
30235 @cindex size of remote memory accesses
30236 @cindex memory, alignment and size of remote accesses
30240 @item @var{XX@dots{}}
30241 Memory contents; each byte is transmitted as a two-digit hexadecimal
30242 number. The reply may contain fewer bytes than requested if the
30243 server was able to read only part of the region of memory.
30248 @item M @var{addr},@var{length}:@var{XX@dots{}}
30249 @cindex @samp{M} packet
30250 Write @var{length} bytes of memory starting at address @var{addr}.
30251 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
30252 hexadecimal number.
30259 for an error (this includes the case where only part of the data was
30264 @cindex @samp{p} packet
30265 Read the value of register @var{n}; @var{n} is in hex.
30266 @xref{read registers packet}, for a description of how the returned
30267 register value is encoded.
30271 @item @var{XX@dots{}}
30272 the register's value
30276 Indicating an unrecognized @var{query}.
30279 @item P @var{n@dots{}}=@var{r@dots{}}
30280 @anchor{write register packet}
30281 @cindex @samp{P} packet
30282 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
30283 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
30284 digits for each byte in the register (target byte order).
30294 @item q @var{name} @var{params}@dots{}
30295 @itemx Q @var{name} @var{params}@dots{}
30296 @cindex @samp{q} packet
30297 @cindex @samp{Q} packet
30298 General query (@samp{q}) and set (@samp{Q}). These packets are
30299 described fully in @ref{General Query Packets}.
30302 @cindex @samp{r} packet
30303 Reset the entire system.
30305 Don't use this packet; use the @samp{R} packet instead.
30308 @cindex @samp{R} packet
30309 Restart the program being debugged. @var{XX}, while needed, is ignored.
30310 This packet is only available in extended mode (@pxref{extended mode}).
30312 The @samp{R} packet has no reply.
30314 @item s @r{[}@var{addr}@r{]}
30315 @cindex @samp{s} packet
30316 Single step. @var{addr} is the address at which to resume. If
30317 @var{addr} is omitted, resume at same address.
30320 @xref{Stop Reply Packets}, for the reply specifications.
30322 @item S @var{sig}@r{[};@var{addr}@r{]}
30323 @anchor{step with signal packet}
30324 @cindex @samp{S} packet
30325 Step with signal. This is analogous to the @samp{C} packet, but
30326 requests a single-step, rather than a normal resumption of execution.
30329 @xref{Stop Reply Packets}, for the reply specifications.
30331 @item t @var{addr}:@var{PP},@var{MM}
30332 @cindex @samp{t} packet
30333 Search backwards starting at address @var{addr} for a match with pattern
30334 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
30335 @var{addr} must be at least 3 digits.
30337 @item T @var{thread-id}
30338 @cindex @samp{T} packet
30339 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
30344 thread is still alive
30350 Packets starting with @samp{v} are identified by a multi-letter name,
30351 up to the first @samp{;} or @samp{?} (or the end of the packet).
30353 @item vAttach;@var{pid}
30354 @cindex @samp{vAttach} packet
30355 Attach to a new process with the specified process ID @var{pid}.
30356 The process ID is a
30357 hexadecimal integer identifying the process. In all-stop mode, all
30358 threads in the attached process are stopped; in non-stop mode, it may be
30359 attached without being stopped if that is supported by the target.
30361 @c In non-stop mode, on a successful vAttach, the stub should set the
30362 @c current thread to a thread of the newly-attached process. After
30363 @c attaching, GDB queries for the attached process's thread ID with qC.
30364 @c Also note that, from a user perspective, whether or not the
30365 @c target is stopped on attach in non-stop mode depends on whether you
30366 @c use the foreground or background version of the attach command, not
30367 @c on what vAttach does; GDB does the right thing with respect to either
30368 @c stopping or restarting threads.
30370 This packet is only available in extended mode (@pxref{extended mode}).
30376 @item @r{Any stop packet}
30377 for success in all-stop mode (@pxref{Stop Reply Packets})
30379 for success in non-stop mode (@pxref{Remote Non-Stop})
30382 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
30383 @cindex @samp{vCont} packet
30384 Resume the inferior, specifying different actions for each thread.
30385 If an action is specified with no @var{thread-id}, then it is applied to any
30386 threads that don't have a specific action specified; if no default action is
30387 specified then other threads should remain stopped in all-stop mode and
30388 in their current state in non-stop mode.
30389 Specifying multiple
30390 default actions is an error; specifying no actions is also an error.
30391 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
30393 Currently supported actions are:
30399 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
30403 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
30408 The optional argument @var{addr} normally associated with the
30409 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
30410 not supported in @samp{vCont}.
30412 The @samp{t} action is only relevant in non-stop mode
30413 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
30414 A stop reply should be generated for any affected thread not already stopped.
30415 When a thread is stopped by means of a @samp{t} action,
30416 the corresponding stop reply should indicate that the thread has stopped with
30417 signal @samp{0}, regardless of whether the target uses some other signal
30418 as an implementation detail.
30421 @xref{Stop Reply Packets}, for the reply specifications.
30424 @cindex @samp{vCont?} packet
30425 Request a list of actions supported by the @samp{vCont} packet.
30429 @item vCont@r{[};@var{action}@dots{}@r{]}
30430 The @samp{vCont} packet is supported. Each @var{action} is a supported
30431 command in the @samp{vCont} packet.
30433 The @samp{vCont} packet is not supported.
30436 @item vFile:@var{operation}:@var{parameter}@dots{}
30437 @cindex @samp{vFile} packet
30438 Perform a file operation on the target system. For details,
30439 see @ref{Host I/O Packets}.
30441 @item vFlashErase:@var{addr},@var{length}
30442 @cindex @samp{vFlashErase} packet
30443 Direct the stub to erase @var{length} bytes of flash starting at
30444 @var{addr}. The region may enclose any number of flash blocks, but
30445 its start and end must fall on block boundaries, as indicated by the
30446 flash block size appearing in the memory map (@pxref{Memory Map
30447 Format}). @value{GDBN} groups flash memory programming operations
30448 together, and sends a @samp{vFlashDone} request after each group; the
30449 stub is allowed to delay erase operation until the @samp{vFlashDone}
30450 packet is received.
30452 The stub must support @samp{vCont} if it reports support for
30453 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
30454 this case @samp{vCont} actions can be specified to apply to all threads
30455 in a process by using the @samp{p@var{pid}.-1} form of the
30466 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
30467 @cindex @samp{vFlashWrite} packet
30468 Direct the stub to write data to flash address @var{addr}. The data
30469 is passed in binary form using the same encoding as for the @samp{X}
30470 packet (@pxref{Binary Data}). The memory ranges specified by
30471 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
30472 not overlap, and must appear in order of increasing addresses
30473 (although @samp{vFlashErase} packets for higher addresses may already
30474 have been received; the ordering is guaranteed only between
30475 @samp{vFlashWrite} packets). If a packet writes to an address that was
30476 neither erased by a preceding @samp{vFlashErase} packet nor by some other
30477 target-specific method, the results are unpredictable.
30485 for vFlashWrite addressing non-flash memory
30491 @cindex @samp{vFlashDone} packet
30492 Indicate to the stub that flash programming operation is finished.
30493 The stub is permitted to delay or batch the effects of a group of
30494 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
30495 @samp{vFlashDone} packet is received. The contents of the affected
30496 regions of flash memory are unpredictable until the @samp{vFlashDone}
30497 request is completed.
30499 @item vKill;@var{pid}
30500 @cindex @samp{vKill} packet
30501 Kill the process with the specified process ID. @var{pid} is a
30502 hexadecimal integer identifying the process. This packet is used in
30503 preference to @samp{k} when multiprocess protocol extensions are
30504 supported; see @ref{multiprocess extensions}.
30514 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
30515 @cindex @samp{vRun} packet
30516 Run the program @var{filename}, passing it each @var{argument} on its
30517 command line. The file and arguments are hex-encoded strings. If
30518 @var{filename} is an empty string, the stub may use a default program
30519 (e.g.@: the last program run). The program is created in the stopped
30522 @c FIXME: What about non-stop mode?
30524 This packet is only available in extended mode (@pxref{extended mode}).
30530 @item @r{Any stop packet}
30531 for success (@pxref{Stop Reply Packets})
30535 @anchor{vStopped packet}
30536 @cindex @samp{vStopped} packet
30538 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
30539 reply and prompt for the stub to report another one.
30543 @item @r{Any stop packet}
30544 if there is another unreported stop event (@pxref{Stop Reply Packets})
30546 if there are no unreported stop events
30549 @item X @var{addr},@var{length}:@var{XX@dots{}}
30551 @cindex @samp{X} packet
30552 Write data to memory, where the data is transmitted in binary.
30553 @var{addr} is address, @var{length} is number of bytes,
30554 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
30564 @item z @var{type},@var{addr},@var{kind}
30565 @itemx Z @var{type},@var{addr},@var{kind}
30566 @anchor{insert breakpoint or watchpoint packet}
30567 @cindex @samp{z} packet
30568 @cindex @samp{Z} packets
30569 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
30570 watchpoint starting at address @var{address} of kind @var{kind}.
30572 Each breakpoint and watchpoint packet @var{type} is documented
30575 @emph{Implementation notes: A remote target shall return an empty string
30576 for an unrecognized breakpoint or watchpoint packet @var{type}. A
30577 remote target shall support either both or neither of a given
30578 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
30579 avoid potential problems with duplicate packets, the operations should
30580 be implemented in an idempotent way.}
30582 @item z0,@var{addr},@var{kind}
30583 @itemx Z0,@var{addr},@var{kind}
30584 @cindex @samp{z0} packet
30585 @cindex @samp{Z0} packet
30586 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
30587 @var{addr} of type @var{kind}.
30589 A memory breakpoint is implemented by replacing the instruction at
30590 @var{addr} with a software breakpoint or trap instruction. The
30591 @var{kind} is target-specific and typically indicates the size of
30592 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
30593 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
30594 architectures have additional meanings for @var{kind};
30595 see @ref{Architecture-Specific Protocol Details}.
30597 @emph{Implementation note: It is possible for a target to copy or move
30598 code that contains memory breakpoints (e.g., when implementing
30599 overlays). The behavior of this packet, in the presence of such a
30600 target, is not defined.}
30612 @item z1,@var{addr},@var{kind}
30613 @itemx Z1,@var{addr},@var{kind}
30614 @cindex @samp{z1} packet
30615 @cindex @samp{Z1} packet
30616 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
30617 address @var{addr}.
30619 A hardware breakpoint is implemented using a mechanism that is not
30620 dependant on being able to modify the target's memory. @var{kind}
30621 has the same meaning as in @samp{Z0} packets.
30623 @emph{Implementation note: A hardware breakpoint is not affected by code
30636 @item z2,@var{addr},@var{kind}
30637 @itemx Z2,@var{addr},@var{kind}
30638 @cindex @samp{z2} packet
30639 @cindex @samp{Z2} packet
30640 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
30641 @var{kind} is interpreted as the number of bytes to watch.
30653 @item z3,@var{addr},@var{kind}
30654 @itemx Z3,@var{addr},@var{kind}
30655 @cindex @samp{z3} packet
30656 @cindex @samp{Z3} packet
30657 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
30658 @var{kind} is interpreted as the number of bytes to watch.
30670 @item z4,@var{addr},@var{kind}
30671 @itemx Z4,@var{addr},@var{kind}
30672 @cindex @samp{z4} packet
30673 @cindex @samp{Z4} packet
30674 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
30675 @var{kind} is interpreted as the number of bytes to watch.
30689 @node Stop Reply Packets
30690 @section Stop Reply Packets
30691 @cindex stop reply packets
30693 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
30694 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
30695 receive any of the below as a reply. Except for @samp{?}
30696 and @samp{vStopped}, that reply is only returned
30697 when the target halts. In the below the exact meaning of @dfn{signal
30698 number} is defined by the header @file{include/gdb/signals.h} in the
30699 @value{GDBN} source code.
30701 As in the description of request packets, we include spaces in the
30702 reply templates for clarity; these are not part of the reply packet's
30703 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
30709 The program received signal number @var{AA} (a two-digit hexadecimal
30710 number). This is equivalent to a @samp{T} response with no
30711 @var{n}:@var{r} pairs.
30713 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
30714 @cindex @samp{T} packet reply
30715 The program received signal number @var{AA} (a two-digit hexadecimal
30716 number). This is equivalent to an @samp{S} response, except that the
30717 @samp{@var{n}:@var{r}} pairs can carry values of important registers
30718 and other information directly in the stop reply packet, reducing
30719 round-trip latency. Single-step and breakpoint traps are reported
30720 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
30724 If @var{n} is a hexadecimal number, it is a register number, and the
30725 corresponding @var{r} gives that register's value. @var{r} is a
30726 series of bytes in target byte order, with each byte given by a
30727 two-digit hex number.
30730 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
30731 the stopped thread, as specified in @ref{thread-id syntax}.
30734 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
30735 the core on which the stop event was detected.
30738 If @var{n} is a recognized @dfn{stop reason}, it describes a more
30739 specific event that stopped the target. The currently defined stop
30740 reasons are listed below. @var{aa} should be @samp{05}, the trap
30741 signal. At most one stop reason should be present.
30744 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
30745 and go on to the next; this allows us to extend the protocol in the
30749 The currently defined stop reasons are:
30755 The packet indicates a watchpoint hit, and @var{r} is the data address, in
30758 @cindex shared library events, remote reply
30760 The packet indicates that the loaded libraries have changed.
30761 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
30762 list of loaded libraries. @var{r} is ignored.
30764 @cindex replay log events, remote reply
30766 The packet indicates that the target cannot continue replaying
30767 logged execution events, because it has reached the end (or the
30768 beginning when executing backward) of the log. The value of @var{r}
30769 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
30770 for more information.
30774 @itemx W @var{AA} ; process:@var{pid}
30775 The process exited, and @var{AA} is the exit status. This is only
30776 applicable to certain targets.
30778 The second form of the response, including the process ID of the exited
30779 process, can be used only when @value{GDBN} has reported support for
30780 multiprocess protocol extensions; see @ref{multiprocess extensions}.
30781 The @var{pid} is formatted as a big-endian hex string.
30784 @itemx X @var{AA} ; process:@var{pid}
30785 The process terminated with signal @var{AA}.
30787 The second form of the response, including the process ID of the
30788 terminated process, can be used only when @value{GDBN} has reported
30789 support for multiprocess protocol extensions; see @ref{multiprocess
30790 extensions}. The @var{pid} is formatted as a big-endian hex string.
30792 @item O @var{XX}@dots{}
30793 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
30794 written as the program's console output. This can happen at any time
30795 while the program is running and the debugger should continue to wait
30796 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
30798 @item F @var{call-id},@var{parameter}@dots{}
30799 @var{call-id} is the identifier which says which host system call should
30800 be called. This is just the name of the function. Translation into the
30801 correct system call is only applicable as it's defined in @value{GDBN}.
30802 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
30805 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
30806 this very system call.
30808 The target replies with this packet when it expects @value{GDBN} to
30809 call a host system call on behalf of the target. @value{GDBN} replies
30810 with an appropriate @samp{F} packet and keeps up waiting for the next
30811 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
30812 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
30813 Protocol Extension}, for more details.
30817 @node General Query Packets
30818 @section General Query Packets
30819 @cindex remote query requests
30821 Packets starting with @samp{q} are @dfn{general query packets};
30822 packets starting with @samp{Q} are @dfn{general set packets}. General
30823 query and set packets are a semi-unified form for retrieving and
30824 sending information to and from the stub.
30826 The initial letter of a query or set packet is followed by a name
30827 indicating what sort of thing the packet applies to. For example,
30828 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
30829 definitions with the stub. These packet names follow some
30834 The name must not contain commas, colons or semicolons.
30836 Most @value{GDBN} query and set packets have a leading upper case
30839 The names of custom vendor packets should use a company prefix, in
30840 lower case, followed by a period. For example, packets designed at
30841 the Acme Corporation might begin with @samp{qacme.foo} (for querying
30842 foos) or @samp{Qacme.bar} (for setting bars).
30845 The name of a query or set packet should be separated from any
30846 parameters by a @samp{:}; the parameters themselves should be
30847 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
30848 full packet name, and check for a separator or the end of the packet,
30849 in case two packet names share a common prefix. New packets should not begin
30850 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
30851 packets predate these conventions, and have arguments without any terminator
30852 for the packet name; we suspect they are in widespread use in places that
30853 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
30854 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
30857 Like the descriptions of the other packets, each description here
30858 has a template showing the packet's overall syntax, followed by an
30859 explanation of the packet's meaning. We include spaces in some of the
30860 templates for clarity; these are not part of the packet's syntax. No
30861 @value{GDBN} packet uses spaces to separate its components.
30863 Here are the currently defined query and set packets:
30868 @cindex current thread, remote request
30869 @cindex @samp{qC} packet
30870 Return the current thread ID.
30874 @item QC @var{thread-id}
30875 Where @var{thread-id} is a thread ID as documented in
30876 @ref{thread-id syntax}.
30877 @item @r{(anything else)}
30878 Any other reply implies the old thread ID.
30881 @item qCRC:@var{addr},@var{length}
30882 @cindex CRC of memory block, remote request
30883 @cindex @samp{qCRC} packet
30884 Compute the CRC checksum of a block of memory using CRC-32 defined in
30885 IEEE 802.3. The CRC is computed byte at a time, taking the most
30886 significant bit of each byte first. The initial pattern code
30887 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
30889 @emph{Note:} This is the same CRC used in validating separate debug
30890 files (@pxref{Separate Debug Files, , Debugging Information in Separate
30891 Files}). However the algorithm is slightly different. When validating
30892 separate debug files, the CRC is computed taking the @emph{least}
30893 significant bit of each byte first, and the final result is inverted to
30894 detect trailing zeros.
30899 An error (such as memory fault)
30900 @item C @var{crc32}
30901 The specified memory region's checksum is @var{crc32}.
30905 @itemx qsThreadInfo
30906 @cindex list active threads, remote request
30907 @cindex @samp{qfThreadInfo} packet
30908 @cindex @samp{qsThreadInfo} packet
30909 Obtain a list of all active thread IDs from the target (OS). Since there
30910 may be too many active threads to fit into one reply packet, this query
30911 works iteratively: it may require more than one query/reply sequence to
30912 obtain the entire list of threads. The first query of the sequence will
30913 be the @samp{qfThreadInfo} query; subsequent queries in the
30914 sequence will be the @samp{qsThreadInfo} query.
30916 NOTE: This packet replaces the @samp{qL} query (see below).
30920 @item m @var{thread-id}
30922 @item m @var{thread-id},@var{thread-id}@dots{}
30923 a comma-separated list of thread IDs
30925 (lower case letter @samp{L}) denotes end of list.
30928 In response to each query, the target will reply with a list of one or
30929 more thread IDs, separated by commas.
30930 @value{GDBN} will respond to each reply with a request for more thread
30931 ids (using the @samp{qs} form of the query), until the target responds
30932 with @samp{l} (lower-case el, for @dfn{last}).
30933 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
30936 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
30937 @cindex get thread-local storage address, remote request
30938 @cindex @samp{qGetTLSAddr} packet
30939 Fetch the address associated with thread local storage specified
30940 by @var{thread-id}, @var{offset}, and @var{lm}.
30942 @var{thread-id} is the thread ID associated with the
30943 thread for which to fetch the TLS address. @xref{thread-id syntax}.
30945 @var{offset} is the (big endian, hex encoded) offset associated with the
30946 thread local variable. (This offset is obtained from the debug
30947 information associated with the variable.)
30949 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
30950 the load module associated with the thread local storage. For example,
30951 a @sc{gnu}/Linux system will pass the link map address of the shared
30952 object associated with the thread local storage under consideration.
30953 Other operating environments may choose to represent the load module
30954 differently, so the precise meaning of this parameter will vary.
30958 @item @var{XX}@dots{}
30959 Hex encoded (big endian) bytes representing the address of the thread
30960 local storage requested.
30963 An error occurred. @var{nn} are hex digits.
30966 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
30969 @item qGetTIBAddr:@var{thread-id}
30970 @cindex get thread information block address
30971 @cindex @samp{qGetTIBAddr} packet
30972 Fetch address of the Windows OS specific Thread Information Block.
30974 @var{thread-id} is the thread ID associated with the thread.
30978 @item @var{XX}@dots{}
30979 Hex encoded (big endian) bytes representing the linear address of the
30980 thread information block.
30983 An error occured. This means that either the thread was not found, or the
30984 address could not be retrieved.
30987 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
30990 @item qL @var{startflag} @var{threadcount} @var{nextthread}
30991 Obtain thread information from RTOS. Where: @var{startflag} (one hex
30992 digit) is one to indicate the first query and zero to indicate a
30993 subsequent query; @var{threadcount} (two hex digits) is the maximum
30994 number of threads the response packet can contain; and @var{nextthread}
30995 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
30996 returned in the response as @var{argthread}.
30998 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
31002 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
31003 Where: @var{count} (two hex digits) is the number of threads being
31004 returned; @var{done} (one hex digit) is zero to indicate more threads
31005 and one indicates no further threads; @var{argthreadid} (eight hex
31006 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
31007 is a sequence of thread IDs from the target. @var{threadid} (eight hex
31008 digits). See @code{remote.c:parse_threadlist_response()}.
31012 @cindex section offsets, remote request
31013 @cindex @samp{qOffsets} packet
31014 Get section offsets that the target used when relocating the downloaded
31019 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
31020 Relocate the @code{Text} section by @var{xxx} from its original address.
31021 Relocate the @code{Data} section by @var{yyy} from its original address.
31022 If the object file format provides segment information (e.g.@: @sc{elf}
31023 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
31024 segments by the supplied offsets.
31026 @emph{Note: while a @code{Bss} offset may be included in the response,
31027 @value{GDBN} ignores this and instead applies the @code{Data} offset
31028 to the @code{Bss} section.}
31030 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
31031 Relocate the first segment of the object file, which conventionally
31032 contains program code, to a starting address of @var{xxx}. If
31033 @samp{DataSeg} is specified, relocate the second segment, which
31034 conventionally contains modifiable data, to a starting address of
31035 @var{yyy}. @value{GDBN} will report an error if the object file
31036 does not contain segment information, or does not contain at least
31037 as many segments as mentioned in the reply. Extra segments are
31038 kept at fixed offsets relative to the last relocated segment.
31041 @item qP @var{mode} @var{thread-id}
31042 @cindex thread information, remote request
31043 @cindex @samp{qP} packet
31044 Returns information on @var{thread-id}. Where: @var{mode} is a hex
31045 encoded 32 bit mode; @var{thread-id} is a thread ID
31046 (@pxref{thread-id syntax}).
31048 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
31051 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
31055 @cindex non-stop mode, remote request
31056 @cindex @samp{QNonStop} packet
31058 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
31059 @xref{Remote Non-Stop}, for more information.
31064 The request succeeded.
31067 An error occurred. @var{nn} are hex digits.
31070 An empty reply indicates that @samp{QNonStop} is not supported by
31074 This packet is not probed by default; the remote stub must request it,
31075 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31076 Use of this packet is controlled by the @code{set non-stop} command;
31077 @pxref{Non-Stop Mode}.
31079 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
31080 @cindex pass signals to inferior, remote request
31081 @cindex @samp{QPassSignals} packet
31082 @anchor{QPassSignals}
31083 Each listed @var{signal} should be passed directly to the inferior process.
31084 Signals are numbered identically to continue packets and stop replies
31085 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
31086 strictly greater than the previous item. These signals do not need to stop
31087 the inferior, or be reported to @value{GDBN}. All other signals should be
31088 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
31089 combine; any earlier @samp{QPassSignals} list is completely replaced by the
31090 new list. This packet improves performance when using @samp{handle
31091 @var{signal} nostop noprint pass}.
31096 The request succeeded.
31099 An error occurred. @var{nn} are hex digits.
31102 An empty reply indicates that @samp{QPassSignals} is not supported by
31106 Use of this packet is controlled by the @code{set remote pass-signals}
31107 command (@pxref{Remote Configuration, set remote pass-signals}).
31108 This packet is not probed by default; the remote stub must request it,
31109 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31111 @item qRcmd,@var{command}
31112 @cindex execute remote command, remote request
31113 @cindex @samp{qRcmd} packet
31114 @var{command} (hex encoded) is passed to the local interpreter for
31115 execution. Invalid commands should be reported using the output
31116 string. Before the final result packet, the target may also respond
31117 with a number of intermediate @samp{O@var{output}} console output
31118 packets. @emph{Implementors should note that providing access to a
31119 stubs's interpreter may have security implications}.
31124 A command response with no output.
31126 A command response with the hex encoded output string @var{OUTPUT}.
31128 Indicate a badly formed request.
31130 An empty reply indicates that @samp{qRcmd} is not recognized.
31133 (Note that the @code{qRcmd} packet's name is separated from the
31134 command by a @samp{,}, not a @samp{:}, contrary to the naming
31135 conventions above. Please don't use this packet as a model for new
31138 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
31139 @cindex searching memory, in remote debugging
31140 @cindex @samp{qSearch:memory} packet
31141 @anchor{qSearch memory}
31142 Search @var{length} bytes at @var{address} for @var{search-pattern}.
31143 @var{address} and @var{length} are encoded in hex.
31144 @var{search-pattern} is a sequence of bytes, hex encoded.
31149 The pattern was not found.
31151 The pattern was found at @var{address}.
31153 A badly formed request or an error was encountered while searching memory.
31155 An empty reply indicates that @samp{qSearch:memory} is not recognized.
31158 @item QStartNoAckMode
31159 @cindex @samp{QStartNoAckMode} packet
31160 @anchor{QStartNoAckMode}
31161 Request that the remote stub disable the normal @samp{+}/@samp{-}
31162 protocol acknowledgments (@pxref{Packet Acknowledgment}).
31167 The stub has switched to no-acknowledgment mode.
31168 @value{GDBN} acknowledges this reponse,
31169 but neither the stub nor @value{GDBN} shall send or expect further
31170 @samp{+}/@samp{-} acknowledgments in the current connection.
31172 An empty reply indicates that the stub does not support no-acknowledgment mode.
31175 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
31176 @cindex supported packets, remote query
31177 @cindex features of the remote protocol
31178 @cindex @samp{qSupported} packet
31179 @anchor{qSupported}
31180 Tell the remote stub about features supported by @value{GDBN}, and
31181 query the stub for features it supports. This packet allows
31182 @value{GDBN} and the remote stub to take advantage of each others'
31183 features. @samp{qSupported} also consolidates multiple feature probes
31184 at startup, to improve @value{GDBN} performance---a single larger
31185 packet performs better than multiple smaller probe packets on
31186 high-latency links. Some features may enable behavior which must not
31187 be on by default, e.g.@: because it would confuse older clients or
31188 stubs. Other features may describe packets which could be
31189 automatically probed for, but are not. These features must be
31190 reported before @value{GDBN} will use them. This ``default
31191 unsupported'' behavior is not appropriate for all packets, but it
31192 helps to keep the initial connection time under control with new
31193 versions of @value{GDBN} which support increasing numbers of packets.
31197 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
31198 The stub supports or does not support each returned @var{stubfeature},
31199 depending on the form of each @var{stubfeature} (see below for the
31202 An empty reply indicates that @samp{qSupported} is not recognized,
31203 or that no features needed to be reported to @value{GDBN}.
31206 The allowed forms for each feature (either a @var{gdbfeature} in the
31207 @samp{qSupported} packet, or a @var{stubfeature} in the response)
31211 @item @var{name}=@var{value}
31212 The remote protocol feature @var{name} is supported, and associated
31213 with the specified @var{value}. The format of @var{value} depends
31214 on the feature, but it must not include a semicolon.
31216 The remote protocol feature @var{name} is supported, and does not
31217 need an associated value.
31219 The remote protocol feature @var{name} is not supported.
31221 The remote protocol feature @var{name} may be supported, and
31222 @value{GDBN} should auto-detect support in some other way when it is
31223 needed. This form will not be used for @var{gdbfeature} notifications,
31224 but may be used for @var{stubfeature} responses.
31227 Whenever the stub receives a @samp{qSupported} request, the
31228 supplied set of @value{GDBN} features should override any previous
31229 request. This allows @value{GDBN} to put the stub in a known
31230 state, even if the stub had previously been communicating with
31231 a different version of @value{GDBN}.
31233 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
31238 This feature indicates whether @value{GDBN} supports multiprocess
31239 extensions to the remote protocol. @value{GDBN} does not use such
31240 extensions unless the stub also reports that it supports them by
31241 including @samp{multiprocess+} in its @samp{qSupported} reply.
31242 @xref{multiprocess extensions}, for details.
31245 This feature indicates that @value{GDBN} supports the XML target
31246 description. If the stub sees @samp{xmlRegisters=} with target
31247 specific strings separated by a comma, it will report register
31251 Stubs should ignore any unknown values for
31252 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
31253 packet supports receiving packets of unlimited length (earlier
31254 versions of @value{GDBN} may reject overly long responses). Additional values
31255 for @var{gdbfeature} may be defined in the future to let the stub take
31256 advantage of new features in @value{GDBN}, e.g.@: incompatible
31257 improvements in the remote protocol---the @samp{multiprocess} feature is
31258 an example of such a feature. The stub's reply should be independent
31259 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
31260 describes all the features it supports, and then the stub replies with
31261 all the features it supports.
31263 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
31264 responses, as long as each response uses one of the standard forms.
31266 Some features are flags. A stub which supports a flag feature
31267 should respond with a @samp{+} form response. Other features
31268 require values, and the stub should respond with an @samp{=}
31271 Each feature has a default value, which @value{GDBN} will use if
31272 @samp{qSupported} is not available or if the feature is not mentioned
31273 in the @samp{qSupported} response. The default values are fixed; a
31274 stub is free to omit any feature responses that match the defaults.
31276 Not all features can be probed, but for those which can, the probing
31277 mechanism is useful: in some cases, a stub's internal
31278 architecture may not allow the protocol layer to know some information
31279 about the underlying target in advance. This is especially common in
31280 stubs which may be configured for multiple targets.
31282 These are the currently defined stub features and their properties:
31284 @multitable @columnfractions 0.35 0.2 0.12 0.2
31285 @c NOTE: The first row should be @headitem, but we do not yet require
31286 @c a new enough version of Texinfo (4.7) to use @headitem.
31288 @tab Value Required
31292 @item @samp{PacketSize}
31297 @item @samp{qXfer:auxv:read}
31302 @item @samp{qXfer:features:read}
31307 @item @samp{qXfer:libraries:read}
31312 @item @samp{qXfer:memory-map:read}
31317 @item @samp{qXfer:spu:read}
31322 @item @samp{qXfer:spu:write}
31327 @item @samp{qXfer:siginfo:read}
31332 @item @samp{qXfer:siginfo:write}
31337 @item @samp{qXfer:threads:read}
31343 @item @samp{QNonStop}
31348 @item @samp{QPassSignals}
31353 @item @samp{QStartNoAckMode}
31358 @item @samp{multiprocess}
31363 @item @samp{ConditionalTracepoints}
31368 @item @samp{ReverseContinue}
31373 @item @samp{ReverseStep}
31378 @item @samp{TracepointSource}
31385 These are the currently defined stub features, in more detail:
31388 @cindex packet size, remote protocol
31389 @item PacketSize=@var{bytes}
31390 The remote stub can accept packets up to at least @var{bytes} in
31391 length. @value{GDBN} will send packets up to this size for bulk
31392 transfers, and will never send larger packets. This is a limit on the
31393 data characters in the packet, including the frame and checksum.
31394 There is no trailing NUL byte in a remote protocol packet; if the stub
31395 stores packets in a NUL-terminated format, it should allow an extra
31396 byte in its buffer for the NUL. If this stub feature is not supported,
31397 @value{GDBN} guesses based on the size of the @samp{g} packet response.
31399 @item qXfer:auxv:read
31400 The remote stub understands the @samp{qXfer:auxv:read} packet
31401 (@pxref{qXfer auxiliary vector read}).
31403 @item qXfer:features:read
31404 The remote stub understands the @samp{qXfer:features:read} packet
31405 (@pxref{qXfer target description read}).
31407 @item qXfer:libraries:read
31408 The remote stub understands the @samp{qXfer:libraries:read} packet
31409 (@pxref{qXfer library list read}).
31411 @item qXfer:memory-map:read
31412 The remote stub understands the @samp{qXfer:memory-map:read} packet
31413 (@pxref{qXfer memory map read}).
31415 @item qXfer:spu:read
31416 The remote stub understands the @samp{qXfer:spu:read} packet
31417 (@pxref{qXfer spu read}).
31419 @item qXfer:spu:write
31420 The remote stub understands the @samp{qXfer:spu:write} packet
31421 (@pxref{qXfer spu write}).
31423 @item qXfer:siginfo:read
31424 The remote stub understands the @samp{qXfer:siginfo:read} packet
31425 (@pxref{qXfer siginfo read}).
31427 @item qXfer:siginfo:write
31428 The remote stub understands the @samp{qXfer:siginfo:write} packet
31429 (@pxref{qXfer siginfo write}).
31431 @item qXfer:threads:read
31432 The remote stub understands the @samp{qXfer:threads:read} packet
31433 (@pxref{qXfer threads read}).
31436 The remote stub understands the @samp{QNonStop} packet
31437 (@pxref{QNonStop}).
31440 The remote stub understands the @samp{QPassSignals} packet
31441 (@pxref{QPassSignals}).
31443 @item QStartNoAckMode
31444 The remote stub understands the @samp{QStartNoAckMode} packet and
31445 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
31448 @anchor{multiprocess extensions}
31449 @cindex multiprocess extensions, in remote protocol
31450 The remote stub understands the multiprocess extensions to the remote
31451 protocol syntax. The multiprocess extensions affect the syntax of
31452 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
31453 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
31454 replies. Note that reporting this feature indicates support for the
31455 syntactic extensions only, not that the stub necessarily supports
31456 debugging of more than one process at a time. The stub must not use
31457 multiprocess extensions in packet replies unless @value{GDBN} has also
31458 indicated it supports them in its @samp{qSupported} request.
31460 @item qXfer:osdata:read
31461 The remote stub understands the @samp{qXfer:osdata:read} packet
31462 ((@pxref{qXfer osdata read}).
31464 @item ConditionalTracepoints
31465 The remote stub accepts and implements conditional expressions defined
31466 for tracepoints (@pxref{Tracepoint Conditions}).
31468 @item ReverseContinue
31469 The remote stub accepts and implements the reverse continue packet
31473 The remote stub accepts and implements the reverse step packet
31476 @item TracepointSource
31477 The remote stub understands the @samp{QTDPsrc} packet that supplies
31478 the source form of tracepoint definitions.
31483 @cindex symbol lookup, remote request
31484 @cindex @samp{qSymbol} packet
31485 Notify the target that @value{GDBN} is prepared to serve symbol lookup
31486 requests. Accept requests from the target for the values of symbols.
31491 The target does not need to look up any (more) symbols.
31492 @item qSymbol:@var{sym_name}
31493 The target requests the value of symbol @var{sym_name} (hex encoded).
31494 @value{GDBN} may provide the value by using the
31495 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
31499 @item qSymbol:@var{sym_value}:@var{sym_name}
31500 Set the value of @var{sym_name} to @var{sym_value}.
31502 @var{sym_name} (hex encoded) is the name of a symbol whose value the
31503 target has previously requested.
31505 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
31506 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
31512 The target does not need to look up any (more) symbols.
31513 @item qSymbol:@var{sym_name}
31514 The target requests the value of a new symbol @var{sym_name} (hex
31515 encoded). @value{GDBN} will continue to supply the values of symbols
31516 (if available), until the target ceases to request them.
31521 @item QTDisconnected
31528 @xref{Tracepoint Packets}.
31530 @item qThreadExtraInfo,@var{thread-id}
31531 @cindex thread attributes info, remote request
31532 @cindex @samp{qThreadExtraInfo} packet
31533 Obtain a printable string description of a thread's attributes from
31534 the target OS. @var{thread-id} is a thread ID;
31535 see @ref{thread-id syntax}. This
31536 string may contain anything that the target OS thinks is interesting
31537 for @value{GDBN} to tell the user about the thread. The string is
31538 displayed in @value{GDBN}'s @code{info threads} display. Some
31539 examples of possible thread extra info strings are @samp{Runnable}, or
31540 @samp{Blocked on Mutex}.
31544 @item @var{XX}@dots{}
31545 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
31546 comprising the printable string containing the extra information about
31547 the thread's attributes.
31550 (Note that the @code{qThreadExtraInfo} packet's name is separated from
31551 the command by a @samp{,}, not a @samp{:}, contrary to the naming
31552 conventions above. Please don't use this packet as a model for new
31564 @xref{Tracepoint Packets}.
31566 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
31567 @cindex read special object, remote request
31568 @cindex @samp{qXfer} packet
31569 @anchor{qXfer read}
31570 Read uninterpreted bytes from the target's special data area
31571 identified by the keyword @var{object}. Request @var{length} bytes
31572 starting at @var{offset} bytes into the data. The content and
31573 encoding of @var{annex} is specific to @var{object}; it can supply
31574 additional details about what data to access.
31576 Here are the specific requests of this form defined so far. All
31577 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
31578 formats, listed below.
31581 @item qXfer:auxv:read::@var{offset},@var{length}
31582 @anchor{qXfer auxiliary vector read}
31583 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
31584 auxiliary vector}. Note @var{annex} must be empty.
31586 This packet is not probed by default; the remote stub must request it,
31587 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31589 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
31590 @anchor{qXfer target description read}
31591 Access the @dfn{target description}. @xref{Target Descriptions}. The
31592 annex specifies which XML document to access. The main description is
31593 always loaded from the @samp{target.xml} annex.
31595 This packet is not probed by default; the remote stub must request it,
31596 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31598 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
31599 @anchor{qXfer library list read}
31600 Access the target's list of loaded libraries. @xref{Library List Format}.
31601 The annex part of the generic @samp{qXfer} packet must be empty
31602 (@pxref{qXfer read}).
31604 Targets which maintain a list of libraries in the program's memory do
31605 not need to implement this packet; it is designed for platforms where
31606 the operating system manages the list of loaded libraries.
31608 This packet is not probed by default; the remote stub must request it,
31609 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31611 @item qXfer:memory-map:read::@var{offset},@var{length}
31612 @anchor{qXfer memory map read}
31613 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
31614 annex part of the generic @samp{qXfer} packet must be empty
31615 (@pxref{qXfer read}).
31617 This packet is not probed by default; the remote stub must request it,
31618 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31620 @item qXfer:siginfo:read::@var{offset},@var{length}
31621 @anchor{qXfer siginfo read}
31622 Read contents of the extra signal information on the target
31623 system. The annex part of the generic @samp{qXfer} packet must be
31624 empty (@pxref{qXfer read}).
31626 This packet is not probed by default; the remote stub must request it,
31627 by supplying an appropriate @samp{qSupported} response
31628 (@pxref{qSupported}).
31630 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
31631 @anchor{qXfer spu read}
31632 Read contents of an @code{spufs} file on the target system. The
31633 annex specifies which file to read; it must be of the form
31634 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
31635 in the target process, and @var{name} identifes the @code{spufs} file
31636 in that context to be accessed.
31638 This packet is not probed by default; the remote stub must request it,
31639 by supplying an appropriate @samp{qSupported} response
31640 (@pxref{qSupported}).
31642 @item qXfer:threads:read::@var{offset},@var{length}
31643 @anchor{qXfer threads read}
31644 Access the list of threads on target. @xref{Thread List Format}. The
31645 annex part of the generic @samp{qXfer} packet must be empty
31646 (@pxref{qXfer read}).
31648 This packet is not probed by default; the remote stub must request it,
31649 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31651 @item qXfer:osdata:read::@var{offset},@var{length}
31652 @anchor{qXfer osdata read}
31653 Access the target's @dfn{operating system information}.
31654 @xref{Operating System Information}.
31661 Data @var{data} (@pxref{Binary Data}) has been read from the
31662 target. There may be more data at a higher address (although
31663 it is permitted to return @samp{m} even for the last valid
31664 block of data, as long as at least one byte of data was read).
31665 @var{data} may have fewer bytes than the @var{length} in the
31669 Data @var{data} (@pxref{Binary Data}) has been read from the target.
31670 There is no more data to be read. @var{data} may have fewer bytes
31671 than the @var{length} in the request.
31674 The @var{offset} in the request is at the end of the data.
31675 There is no more data to be read.
31678 The request was malformed, or @var{annex} was invalid.
31681 The offset was invalid, or there was an error encountered reading the data.
31682 @var{nn} is a hex-encoded @code{errno} value.
31685 An empty reply indicates the @var{object} string was not recognized by
31686 the stub, or that the object does not support reading.
31689 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
31690 @cindex write data into object, remote request
31691 @anchor{qXfer write}
31692 Write uninterpreted bytes into the target's special data area
31693 identified by the keyword @var{object}, starting at @var{offset} bytes
31694 into the data. @var{data}@dots{} is the binary-encoded data
31695 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
31696 is specific to @var{object}; it can supply additional details about what data
31699 Here are the specific requests of this form defined so far. All
31700 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
31701 formats, listed below.
31704 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
31705 @anchor{qXfer siginfo write}
31706 Write @var{data} to the extra signal information on the target system.
31707 The annex part of the generic @samp{qXfer} packet must be
31708 empty (@pxref{qXfer write}).
31710 This packet is not probed by default; the remote stub must request it,
31711 by supplying an appropriate @samp{qSupported} response
31712 (@pxref{qSupported}).
31714 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
31715 @anchor{qXfer spu write}
31716 Write @var{data} to an @code{spufs} file on the target system. The
31717 annex specifies which file to write; it must be of the form
31718 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
31719 in the target process, and @var{name} identifes the @code{spufs} file
31720 in that context to be accessed.
31722 This packet is not probed by default; the remote stub must request it,
31723 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31729 @var{nn} (hex encoded) is the number of bytes written.
31730 This may be fewer bytes than supplied in the request.
31733 The request was malformed, or @var{annex} was invalid.
31736 The offset was invalid, or there was an error encountered writing the data.
31737 @var{nn} is a hex-encoded @code{errno} value.
31740 An empty reply indicates the @var{object} string was not
31741 recognized by the stub, or that the object does not support writing.
31744 @item qXfer:@var{object}:@var{operation}:@dots{}
31745 Requests of this form may be added in the future. When a stub does
31746 not recognize the @var{object} keyword, or its support for
31747 @var{object} does not recognize the @var{operation} keyword, the stub
31748 must respond with an empty packet.
31750 @item qAttached:@var{pid}
31751 @cindex query attached, remote request
31752 @cindex @samp{qAttached} packet
31753 Return an indication of whether the remote server attached to an
31754 existing process or created a new process. When the multiprocess
31755 protocol extensions are supported (@pxref{multiprocess extensions}),
31756 @var{pid} is an integer in hexadecimal format identifying the target
31757 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
31758 the query packet will be simplified as @samp{qAttached}.
31760 This query is used, for example, to know whether the remote process
31761 should be detached or killed when a @value{GDBN} session is ended with
31762 the @code{quit} command.
31767 The remote server attached to an existing process.
31769 The remote server created a new process.
31771 A badly formed request or an error was encountered.
31776 @node Architecture-Specific Protocol Details
31777 @section Architecture-Specific Protocol Details
31779 This section describes how the remote protocol is applied to specific
31780 target architectures. Also see @ref{Standard Target Features}, for
31781 details of XML target descriptions for each architecture.
31785 @subsubsection Breakpoint Kinds
31787 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
31792 16-bit Thumb mode breakpoint.
31795 32-bit Thumb mode (Thumb-2) breakpoint.
31798 32-bit ARM mode breakpoint.
31804 @subsubsection Register Packet Format
31806 The following @code{g}/@code{G} packets have previously been defined.
31807 In the below, some thirty-two bit registers are transferred as
31808 sixty-four bits. Those registers should be zero/sign extended (which?)
31809 to fill the space allocated. Register bytes are transferred in target
31810 byte order. The two nibbles within a register byte are transferred
31811 most-significant - least-significant.
31817 All registers are transferred as thirty-two bit quantities in the order:
31818 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
31819 registers; fsr; fir; fp.
31823 All registers are transferred as sixty-four bit quantities (including
31824 thirty-two bit registers such as @code{sr}). The ordering is the same
31829 @node Tracepoint Packets
31830 @section Tracepoint Packets
31831 @cindex tracepoint packets
31832 @cindex packets, tracepoint
31834 Here we describe the packets @value{GDBN} uses to implement
31835 tracepoints (@pxref{Tracepoints}).
31839 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
31840 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
31841 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
31842 the tracepoint is disabled. @var{step} is the tracepoint's step
31843 count, and @var{pass} is its pass count. If an @samp{F} is present,
31844 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
31845 the number of bytes that the target should copy elsewhere to make room
31846 for the tracepoint. If an @samp{X} is present, it introduces a
31847 tracepoint condition, which consists of a hexadecimal length, followed
31848 by a comma and hex-encoded bytes, in a manner similar to action
31849 encodings as described below. If the trailing @samp{-} is present,
31850 further @samp{QTDP} packets will follow to specify this tracepoint's
31856 The packet was understood and carried out.
31858 The packet was not recognized.
31861 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
31862 Define actions to be taken when a tracepoint is hit. @var{n} and
31863 @var{addr} must be the same as in the initial @samp{QTDP} packet for
31864 this tracepoint. This packet may only be sent immediately after
31865 another @samp{QTDP} packet that ended with a @samp{-}. If the
31866 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
31867 specifying more actions for this tracepoint.
31869 In the series of action packets for a given tracepoint, at most one
31870 can have an @samp{S} before its first @var{action}. If such a packet
31871 is sent, it and the following packets define ``while-stepping''
31872 actions. Any prior packets define ordinary actions --- that is, those
31873 taken when the tracepoint is first hit. If no action packet has an
31874 @samp{S}, then all the packets in the series specify ordinary
31875 tracepoint actions.
31877 The @samp{@var{action}@dots{}} portion of the packet is a series of
31878 actions, concatenated without separators. Each action has one of the
31884 Collect the registers whose bits are set in @var{mask}. @var{mask} is
31885 a hexadecimal number whose @var{i}'th bit is set if register number
31886 @var{i} should be collected. (The least significant bit is numbered
31887 zero.) Note that @var{mask} may be any number of digits long; it may
31888 not fit in a 32-bit word.
31890 @item M @var{basereg},@var{offset},@var{len}
31891 Collect @var{len} bytes of memory starting at the address in register
31892 number @var{basereg}, plus @var{offset}. If @var{basereg} is
31893 @samp{-1}, then the range has a fixed address: @var{offset} is the
31894 address of the lowest byte to collect. The @var{basereg},
31895 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
31896 values (the @samp{-1} value for @var{basereg} is a special case).
31898 @item X @var{len},@var{expr}
31899 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
31900 it directs. @var{expr} is an agent expression, as described in
31901 @ref{Agent Expressions}. Each byte of the expression is encoded as a
31902 two-digit hex number in the packet; @var{len} is the number of bytes
31903 in the expression (and thus one-half the number of hex digits in the
31908 Any number of actions may be packed together in a single @samp{QTDP}
31909 packet, as long as the packet does not exceed the maximum packet
31910 length (400 bytes, for many stubs). There may be only one @samp{R}
31911 action per tracepoint, and it must precede any @samp{M} or @samp{X}
31912 actions. Any registers referred to by @samp{M} and @samp{X} actions
31913 must be collected by a preceding @samp{R} action. (The
31914 ``while-stepping'' actions are treated as if they were attached to a
31915 separate tracepoint, as far as these restrictions are concerned.)
31920 The packet was understood and carried out.
31922 The packet was not recognized.
31925 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
31926 @cindex @samp{QTDPsrc} packet
31927 Specify a source string of tracepoint @var{n} at address @var{addr}.
31928 This is useful to get accurate reproduction of the tracepoints
31929 originally downloaded at the beginning of the trace run. @var{type}
31930 is the name of the tracepoint part, such as @samp{cond} for the
31931 tracepoint's conditional expression (see below for a list of types), while
31932 @var{bytes} is the string, encoded in hexadecimal.
31934 @var{start} is the offset of the @var{bytes} within the overall source
31935 string, while @var{slen} is the total length of the source string.
31936 This is intended for handling source strings that are longer than will
31937 fit in a single packet.
31938 @c Add detailed example when this info is moved into a dedicated
31939 @c tracepoint descriptions section.
31941 The available string types are @samp{at} for the location,
31942 @samp{cond} for the conditional, and @samp{cmd} for an action command.
31943 @value{GDBN} sends a separate packet for each command in the action
31944 list, in the same order in which the commands are stored in the list.
31946 The target does not need to do anything with source strings except
31947 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
31950 Although this packet is optional, and @value{GDBN} will only send it
31951 if the target replies with @samp{TracepointSource} @xref{General
31952 Query Packets}, it makes both disconnected tracing and trace files
31953 much easier to use. Otherwise the user must be careful that the
31954 tracepoints in effect while looking at trace frames are identical to
31955 the ones in effect during the trace run; even a small discrepancy
31956 could cause @samp{tdump} not to work, or a particular trace frame not
31959 @item QTDV:@var{n}:@var{value}
31960 @cindex define trace state variable, remote request
31961 @cindex @samp{QTDV} packet
31962 Create a new trace state variable, number @var{n}, with an initial
31963 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
31964 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
31965 the option of not using this packet for initial values of zero; the
31966 target should simply create the trace state variables as they are
31967 mentioned in expressions.
31969 @item QTFrame:@var{n}
31970 Select the @var{n}'th tracepoint frame from the buffer, and use the
31971 register and memory contents recorded there to answer subsequent
31972 request packets from @value{GDBN}.
31974 A successful reply from the stub indicates that the stub has found the
31975 requested frame. The response is a series of parts, concatenated
31976 without separators, describing the frame we selected. Each part has
31977 one of the following forms:
31981 The selected frame is number @var{n} in the trace frame buffer;
31982 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
31983 was no frame matching the criteria in the request packet.
31986 The selected trace frame records a hit of tracepoint number @var{t};
31987 @var{t} is a hexadecimal number.
31991 @item QTFrame:pc:@var{addr}
31992 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
31993 currently selected frame whose PC is @var{addr};
31994 @var{addr} is a hexadecimal number.
31996 @item QTFrame:tdp:@var{t}
31997 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
31998 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
31999 is a hexadecimal number.
32001 @item QTFrame:range:@var{start}:@var{end}
32002 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32003 currently selected frame whose PC is between @var{start} (inclusive)
32004 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
32007 @item QTFrame:outside:@var{start}:@var{end}
32008 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
32009 frame @emph{outside} the given range of addresses (exclusive).
32012 Begin the tracepoint experiment. Begin collecting data from tracepoint
32013 hits in the trace frame buffer.
32016 End the tracepoint experiment. Stop collecting trace frames.
32019 Clear the table of tracepoints, and empty the trace frame buffer.
32021 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
32022 Establish the given ranges of memory as ``transparent''. The stub
32023 will answer requests for these ranges from memory's current contents,
32024 if they were not collected as part of the tracepoint hit.
32026 @value{GDBN} uses this to mark read-only regions of memory, like those
32027 containing program code. Since these areas never change, they should
32028 still have the same contents they did when the tracepoint was hit, so
32029 there's no reason for the stub to refuse to provide their contents.
32031 @item QTDisconnected:@var{value}
32032 Set the choice to what to do with the tracing run when @value{GDBN}
32033 disconnects from the target. A @var{value} of 1 directs the target to
32034 continue the tracing run, while 0 tells the target to stop tracing if
32035 @value{GDBN} is no longer in the picture.
32038 Ask the stub if there is a trace experiment running right now.
32040 The reply has the form:
32044 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
32045 @var{running} is a single digit @code{1} if the trace is presently
32046 running, or @code{0} if not. It is followed by semicolon-separated
32047 optional fields that an agent may use to report additional status.
32051 If the trace is not running, the agent may report any of several
32052 explanations as one of the optional fields:
32057 No trace has been run yet.
32060 The trace was stopped by a user-originated stop command.
32063 The trace stopped because the trace buffer filled up.
32065 @item tdisconnected:0
32066 The trace stopped because @value{GDBN} disconnected from the target.
32068 @item tpasscount:@var{tpnum}
32069 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
32071 @item terror:@var{text}:@var{tpnum}
32072 The trace stopped because tracepoint @var{tpnum} had an error. The
32073 string @var{text} is available to describe the nature of the error
32074 (for instance, a divide by zero in the condition expression).
32075 @var{text} is hex encoded.
32078 The trace stopped for some other reason.
32082 Additional optional fields supply statistical and other information.
32083 Although not required, they are extremely useful for users monitoring
32084 the progress of a trace run. If a trace has stopped, and these
32085 numbers are reported, they must reflect the state of the just-stopped
32090 @item tframes:@var{n}
32091 The number of trace frames in the buffer.
32093 @item tcreated:@var{n}
32094 The total number of trace frames created during the run. This may
32095 be larger than the trace frame count, if the buffer is circular.
32097 @item tsize:@var{n}
32098 The total size of the trace buffer, in bytes.
32100 @item tfree:@var{n}
32101 The number of bytes still unused in the buffer.
32103 @item circular:@var{n}
32104 The value of the circular trace buffer flag. @code{1} means that the
32105 trace buffer is circular and old trace frames will be discarded if
32106 necessary to make room, @code{0} means that the trace buffer is linear
32109 @item disconn:@var{n}
32110 The value of the disconnected tracing flag. @code{1} means that
32111 tracing will continue after @value{GDBN} disconnects, @code{0} means
32112 that the trace run will stop.
32116 @item qTV:@var{var}
32117 @cindex trace state variable value, remote request
32118 @cindex @samp{qTV} packet
32119 Ask the stub for the value of the trace state variable number @var{var}.
32124 The value of the variable is @var{value}. This will be the current
32125 value of the variable if the user is examining a running target, or a
32126 saved value if the variable was collected in the trace frame that the
32127 user is looking at. Note that multiple requests may result in
32128 different reply values, such as when requesting values while the
32129 program is running.
32132 The value of the variable is unknown. This would occur, for example,
32133 if the user is examining a trace frame in which the requested variable
32139 These packets request data about tracepoints that are being used by
32140 the target. @value{GDBN} sends @code{qTfP} to get the first piece
32141 of data, and multiple @code{qTsP} to get additional pieces. Replies
32142 to these packets generally take the form of the @code{QTDP} packets
32143 that define tracepoints. (FIXME add detailed syntax)
32147 These packets request data about trace state variables that are on the
32148 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
32149 and multiple @code{qTsV} to get additional variables. Replies to
32150 these packets follow the syntax of the @code{QTDV} packets that define
32151 trace state variables.
32153 @item QTSave:@var{filename}
32154 This packet directs the target to save trace data to the file name
32155 @var{filename} in the target's filesystem. @var{filename} is encoded
32156 as a hex string; the interpretation of the file name (relative vs
32157 absolute, wild cards, etc) is up to the target.
32159 @item qTBuffer:@var{offset},@var{len}
32160 Return up to @var{len} bytes of the current contents of trace buffer,
32161 starting at @var{offset}. The trace buffer is treated as if it were
32162 a contiguous collection of traceframes, as per the trace file format.
32163 The reply consists as many hex-encoded bytes as the target can deliver
32164 in a packet; it is not an error to return fewer than were asked for.
32165 A reply consisting of just @code{l} indicates that no bytes are
32168 @item QTBuffer:circular:@var{value}
32169 This packet directs the target to use a circular trace buffer if
32170 @var{value} is 1, or a linear buffer if the value is 0.
32174 @node Host I/O Packets
32175 @section Host I/O Packets
32176 @cindex Host I/O, remote protocol
32177 @cindex file transfer, remote protocol
32179 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
32180 operations on the far side of a remote link. For example, Host I/O is
32181 used to upload and download files to a remote target with its own
32182 filesystem. Host I/O uses the same constant values and data structure
32183 layout as the target-initiated File-I/O protocol. However, the
32184 Host I/O packets are structured differently. The target-initiated
32185 protocol relies on target memory to store parameters and buffers.
32186 Host I/O requests are initiated by @value{GDBN}, and the
32187 target's memory is not involved. @xref{File-I/O Remote Protocol
32188 Extension}, for more details on the target-initiated protocol.
32190 The Host I/O request packets all encode a single operation along with
32191 its arguments. They have this format:
32195 @item vFile:@var{operation}: @var{parameter}@dots{}
32196 @var{operation} is the name of the particular request; the target
32197 should compare the entire packet name up to the second colon when checking
32198 for a supported operation. The format of @var{parameter} depends on
32199 the operation. Numbers are always passed in hexadecimal. Negative
32200 numbers have an explicit minus sign (i.e.@: two's complement is not
32201 used). Strings (e.g.@: filenames) are encoded as a series of
32202 hexadecimal bytes. The last argument to a system call may be a
32203 buffer of escaped binary data (@pxref{Binary Data}).
32207 The valid responses to Host I/O packets are:
32211 @item F @var{result} [, @var{errno}] [; @var{attachment}]
32212 @var{result} is the integer value returned by this operation, usually
32213 non-negative for success and -1 for errors. If an error has occured,
32214 @var{errno} will be included in the result. @var{errno} will have a
32215 value defined by the File-I/O protocol (@pxref{Errno Values}). For
32216 operations which return data, @var{attachment} supplies the data as a
32217 binary buffer. Binary buffers in response packets are escaped in the
32218 normal way (@pxref{Binary Data}). See the individual packet
32219 documentation for the interpretation of @var{result} and
32223 An empty response indicates that this operation is not recognized.
32227 These are the supported Host I/O operations:
32230 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
32231 Open a file at @var{pathname} and return a file descriptor for it, or
32232 return -1 if an error occurs. @var{pathname} is a string,
32233 @var{flags} is an integer indicating a mask of open flags
32234 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
32235 of mode bits to use if the file is created (@pxref{mode_t Values}).
32236 @xref{open}, for details of the open flags and mode values.
32238 @item vFile:close: @var{fd}
32239 Close the open file corresponding to @var{fd} and return 0, or
32240 -1 if an error occurs.
32242 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
32243 Read data from the open file corresponding to @var{fd}. Up to
32244 @var{count} bytes will be read from the file, starting at @var{offset}
32245 relative to the start of the file. The target may read fewer bytes;
32246 common reasons include packet size limits and an end-of-file
32247 condition. The number of bytes read is returned. Zero should only be
32248 returned for a successful read at the end of the file, or if
32249 @var{count} was zero.
32251 The data read should be returned as a binary attachment on success.
32252 If zero bytes were read, the response should include an empty binary
32253 attachment (i.e.@: a trailing semicolon). The return value is the
32254 number of target bytes read; the binary attachment may be longer if
32255 some characters were escaped.
32257 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
32258 Write @var{data} (a binary buffer) to the open file corresponding
32259 to @var{fd}. Start the write at @var{offset} from the start of the
32260 file. Unlike many @code{write} system calls, there is no
32261 separate @var{count} argument; the length of @var{data} in the
32262 packet is used. @samp{vFile:write} returns the number of bytes written,
32263 which may be shorter than the length of @var{data}, or -1 if an
32266 @item vFile:unlink: @var{pathname}
32267 Delete the file at @var{pathname} on the target. Return 0,
32268 or -1 if an error occurs. @var{pathname} is a string.
32273 @section Interrupts
32274 @cindex interrupts (remote protocol)
32276 When a program on the remote target is running, @value{GDBN} may
32277 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
32278 a @code{BREAK} followed by @code{g},
32279 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
32281 The precise meaning of @code{BREAK} is defined by the transport
32282 mechanism and may, in fact, be undefined. @value{GDBN} does not
32283 currently define a @code{BREAK} mechanism for any of the network
32284 interfaces except for TCP, in which case @value{GDBN} sends the
32285 @code{telnet} BREAK sequence.
32287 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
32288 transport mechanisms. It is represented by sending the single byte
32289 @code{0x03} without any of the usual packet overhead described in
32290 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
32291 transmitted as part of a packet, it is considered to be packet data
32292 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
32293 (@pxref{X packet}), used for binary downloads, may include an unescaped
32294 @code{0x03} as part of its packet.
32296 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
32297 When Linux kernel receives this sequence from serial port,
32298 it stops execution and connects to gdb.
32300 Stubs are not required to recognize these interrupt mechanisms and the
32301 precise meaning associated with receipt of the interrupt is
32302 implementation defined. If the target supports debugging of multiple
32303 threads and/or processes, it should attempt to interrupt all
32304 currently-executing threads and processes.
32305 If the stub is successful at interrupting the
32306 running program, it should send one of the stop
32307 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
32308 of successfully stopping the program in all-stop mode, and a stop reply
32309 for each stopped thread in non-stop mode.
32310 Interrupts received while the
32311 program is stopped are discarded.
32313 @node Notification Packets
32314 @section Notification Packets
32315 @cindex notification packets
32316 @cindex packets, notification
32318 The @value{GDBN} remote serial protocol includes @dfn{notifications},
32319 packets that require no acknowledgment. Both the GDB and the stub
32320 may send notifications (although the only notifications defined at
32321 present are sent by the stub). Notifications carry information
32322 without incurring the round-trip latency of an acknowledgment, and so
32323 are useful for low-impact communications where occasional packet loss
32326 A notification packet has the form @samp{% @var{data} #
32327 @var{checksum}}, where @var{data} is the content of the notification,
32328 and @var{checksum} is a checksum of @var{data}, computed and formatted
32329 as for ordinary @value{GDBN} packets. A notification's @var{data}
32330 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
32331 receiving a notification, the recipient sends no @samp{+} or @samp{-}
32332 to acknowledge the notification's receipt or to report its corruption.
32334 Every notification's @var{data} begins with a name, which contains no
32335 colon characters, followed by a colon character.
32337 Recipients should silently ignore corrupted notifications and
32338 notifications they do not understand. Recipients should restart
32339 timeout periods on receipt of a well-formed notification, whether or
32340 not they understand it.
32342 Senders should only send the notifications described here when this
32343 protocol description specifies that they are permitted. In the
32344 future, we may extend the protocol to permit existing notifications in
32345 new contexts; this rule helps older senders avoid confusing newer
32348 (Older versions of @value{GDBN} ignore bytes received until they see
32349 the @samp{$} byte that begins an ordinary packet, so new stubs may
32350 transmit notifications without fear of confusing older clients. There
32351 are no notifications defined for @value{GDBN} to send at the moment, but we
32352 assume that most older stubs would ignore them, as well.)
32354 The following notification packets from the stub to @value{GDBN} are
32358 @item Stop: @var{reply}
32359 Report an asynchronous stop event in non-stop mode.
32360 The @var{reply} has the form of a stop reply, as
32361 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
32362 for information on how these notifications are acknowledged by
32366 @node Remote Non-Stop
32367 @section Remote Protocol Support for Non-Stop Mode
32369 @value{GDBN}'s remote protocol supports non-stop debugging of
32370 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
32371 supports non-stop mode, it should report that to @value{GDBN} by including
32372 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
32374 @value{GDBN} typically sends a @samp{QNonStop} packet only when
32375 establishing a new connection with the stub. Entering non-stop mode
32376 does not alter the state of any currently-running threads, but targets
32377 must stop all threads in any already-attached processes when entering
32378 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
32379 probe the target state after a mode change.
32381 In non-stop mode, when an attached process encounters an event that
32382 would otherwise be reported with a stop reply, it uses the
32383 asynchronous notification mechanism (@pxref{Notification Packets}) to
32384 inform @value{GDBN}. In contrast to all-stop mode, where all threads
32385 in all processes are stopped when a stop reply is sent, in non-stop
32386 mode only the thread reporting the stop event is stopped. That is,
32387 when reporting a @samp{S} or @samp{T} response to indicate completion
32388 of a step operation, hitting a breakpoint, or a fault, only the
32389 affected thread is stopped; any other still-running threads continue
32390 to run. When reporting a @samp{W} or @samp{X} response, all running
32391 threads belonging to other attached processes continue to run.
32393 Only one stop reply notification at a time may be pending; if
32394 additional stop events occur before @value{GDBN} has acknowledged the
32395 previous notification, they must be queued by the stub for later
32396 synchronous transmission in response to @samp{vStopped} packets from
32397 @value{GDBN}. Because the notification mechanism is unreliable,
32398 the stub is permitted to resend a stop reply notification
32399 if it believes @value{GDBN} may not have received it. @value{GDBN}
32400 ignores additional stop reply notifications received before it has
32401 finished processing a previous notification and the stub has completed
32402 sending any queued stop events.
32404 Otherwise, @value{GDBN} must be prepared to receive a stop reply
32405 notification at any time. Specifically, they may appear when
32406 @value{GDBN} is not otherwise reading input from the stub, or when
32407 @value{GDBN} is expecting to read a normal synchronous response or a
32408 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
32409 Notification packets are distinct from any other communication from
32410 the stub so there is no ambiguity.
32412 After receiving a stop reply notification, @value{GDBN} shall
32413 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
32414 as a regular, synchronous request to the stub. Such acknowledgment
32415 is not required to happen immediately, as @value{GDBN} is permitted to
32416 send other, unrelated packets to the stub first, which the stub should
32419 Upon receiving a @samp{vStopped} packet, if the stub has other queued
32420 stop events to report to @value{GDBN}, it shall respond by sending a
32421 normal stop reply response. @value{GDBN} shall then send another
32422 @samp{vStopped} packet to solicit further responses; again, it is
32423 permitted to send other, unrelated packets as well which the stub
32424 should process normally.
32426 If the stub receives a @samp{vStopped} packet and there are no
32427 additional stop events to report, the stub shall return an @samp{OK}
32428 response. At this point, if further stop events occur, the stub shall
32429 send a new stop reply notification, @value{GDBN} shall accept the
32430 notification, and the process shall be repeated.
32432 In non-stop mode, the target shall respond to the @samp{?} packet as
32433 follows. First, any incomplete stop reply notification/@samp{vStopped}
32434 sequence in progress is abandoned. The target must begin a new
32435 sequence reporting stop events for all stopped threads, whether or not
32436 it has previously reported those events to @value{GDBN}. The first
32437 stop reply is sent as a synchronous reply to the @samp{?} packet, and
32438 subsequent stop replies are sent as responses to @samp{vStopped} packets
32439 using the mechanism described above. The target must not send
32440 asynchronous stop reply notifications until the sequence is complete.
32441 If all threads are running when the target receives the @samp{?} packet,
32442 or if the target is not attached to any process, it shall respond
32445 @node Packet Acknowledgment
32446 @section Packet Acknowledgment
32448 @cindex acknowledgment, for @value{GDBN} remote
32449 @cindex packet acknowledgment, for @value{GDBN} remote
32450 By default, when either the host or the target machine receives a packet,
32451 the first response expected is an acknowledgment: either @samp{+} (to indicate
32452 the package was received correctly) or @samp{-} (to request retransmission).
32453 This mechanism allows the @value{GDBN} remote protocol to operate over
32454 unreliable transport mechanisms, such as a serial line.
32456 In cases where the transport mechanism is itself reliable (such as a pipe or
32457 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
32458 It may be desirable to disable them in that case to reduce communication
32459 overhead, or for other reasons. This can be accomplished by means of the
32460 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
32462 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
32463 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
32464 and response format still includes the normal checksum, as described in
32465 @ref{Overview}, but the checksum may be ignored by the receiver.
32467 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
32468 no-acknowledgment mode, it should report that to @value{GDBN}
32469 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
32470 @pxref{qSupported}.
32471 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
32472 disabled via the @code{set remote noack-packet off} command
32473 (@pxref{Remote Configuration}),
32474 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
32475 Only then may the stub actually turn off packet acknowledgments.
32476 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
32477 response, which can be safely ignored by the stub.
32479 Note that @code{set remote noack-packet} command only affects negotiation
32480 between @value{GDBN} and the stub when subsequent connections are made;
32481 it does not affect the protocol acknowledgment state for any current
32483 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
32484 new connection is established,
32485 there is also no protocol request to re-enable the acknowledgments
32486 for the current connection, once disabled.
32491 Example sequence of a target being re-started. Notice how the restart
32492 does not get any direct output:
32497 @emph{target restarts}
32500 <- @code{T001:1234123412341234}
32504 Example sequence of a target being stepped by a single instruction:
32507 -> @code{G1445@dots{}}
32512 <- @code{T001:1234123412341234}
32516 <- @code{1455@dots{}}
32520 @node File-I/O Remote Protocol Extension
32521 @section File-I/O Remote Protocol Extension
32522 @cindex File-I/O remote protocol extension
32525 * File-I/O Overview::
32526 * Protocol Basics::
32527 * The F Request Packet::
32528 * The F Reply Packet::
32529 * The Ctrl-C Message::
32531 * List of Supported Calls::
32532 * Protocol-specific Representation of Datatypes::
32534 * File-I/O Examples::
32537 @node File-I/O Overview
32538 @subsection File-I/O Overview
32539 @cindex file-i/o overview
32541 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
32542 target to use the host's file system and console I/O to perform various
32543 system calls. System calls on the target system are translated into a
32544 remote protocol packet to the host system, which then performs the needed
32545 actions and returns a response packet to the target system.
32546 This simulates file system operations even on targets that lack file systems.
32548 The protocol is defined to be independent of both the host and target systems.
32549 It uses its own internal representation of datatypes and values. Both
32550 @value{GDBN} and the target's @value{GDBN} stub are responsible for
32551 translating the system-dependent value representations into the internal
32552 protocol representations when data is transmitted.
32554 The communication is synchronous. A system call is possible only when
32555 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
32556 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
32557 the target is stopped to allow deterministic access to the target's
32558 memory. Therefore File-I/O is not interruptible by target signals. On
32559 the other hand, it is possible to interrupt File-I/O by a user interrupt
32560 (@samp{Ctrl-C}) within @value{GDBN}.
32562 The target's request to perform a host system call does not finish
32563 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
32564 after finishing the system call, the target returns to continuing the
32565 previous activity (continue, step). No additional continue or step
32566 request from @value{GDBN} is required.
32569 (@value{GDBP}) continue
32570 <- target requests 'system call X'
32571 target is stopped, @value{GDBN} executes system call
32572 -> @value{GDBN} returns result
32573 ... target continues, @value{GDBN} returns to wait for the target
32574 <- target hits breakpoint and sends a Txx packet
32577 The protocol only supports I/O on the console and to regular files on
32578 the host file system. Character or block special devices, pipes,
32579 named pipes, sockets or any other communication method on the host
32580 system are not supported by this protocol.
32582 File I/O is not supported in non-stop mode.
32584 @node Protocol Basics
32585 @subsection Protocol Basics
32586 @cindex protocol basics, file-i/o
32588 The File-I/O protocol uses the @code{F} packet as the request as well
32589 as reply packet. Since a File-I/O system call can only occur when
32590 @value{GDBN} is waiting for a response from the continuing or stepping target,
32591 the File-I/O request is a reply that @value{GDBN} has to expect as a result
32592 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
32593 This @code{F} packet contains all information needed to allow @value{GDBN}
32594 to call the appropriate host system call:
32598 A unique identifier for the requested system call.
32601 All parameters to the system call. Pointers are given as addresses
32602 in the target memory address space. Pointers to strings are given as
32603 pointer/length pair. Numerical values are given as they are.
32604 Numerical control flags are given in a protocol-specific representation.
32608 At this point, @value{GDBN} has to perform the following actions.
32612 If the parameters include pointer values to data needed as input to a
32613 system call, @value{GDBN} requests this data from the target with a
32614 standard @code{m} packet request. This additional communication has to be
32615 expected by the target implementation and is handled as any other @code{m}
32619 @value{GDBN} translates all value from protocol representation to host
32620 representation as needed. Datatypes are coerced into the host types.
32623 @value{GDBN} calls the system call.
32626 It then coerces datatypes back to protocol representation.
32629 If the system call is expected to return data in buffer space specified
32630 by pointer parameters to the call, the data is transmitted to the
32631 target using a @code{M} or @code{X} packet. This packet has to be expected
32632 by the target implementation and is handled as any other @code{M} or @code{X}
32637 Eventually @value{GDBN} replies with another @code{F} packet which contains all
32638 necessary information for the target to continue. This at least contains
32645 @code{errno}, if has been changed by the system call.
32652 After having done the needed type and value coercion, the target continues
32653 the latest continue or step action.
32655 @node The F Request Packet
32656 @subsection The @code{F} Request Packet
32657 @cindex file-i/o request packet
32658 @cindex @code{F} request packet
32660 The @code{F} request packet has the following format:
32663 @item F@var{call-id},@var{parameter@dots{}}
32665 @var{call-id} is the identifier to indicate the host system call to be called.
32666 This is just the name of the function.
32668 @var{parameter@dots{}} are the parameters to the system call.
32669 Parameters are hexadecimal integer values, either the actual values in case
32670 of scalar datatypes, pointers to target buffer space in case of compound
32671 datatypes and unspecified memory areas, or pointer/length pairs in case
32672 of string parameters. These are appended to the @var{call-id} as a
32673 comma-delimited list. All values are transmitted in ASCII
32674 string representation, pointer/length pairs separated by a slash.
32680 @node The F Reply Packet
32681 @subsection The @code{F} Reply Packet
32682 @cindex file-i/o reply packet
32683 @cindex @code{F} reply packet
32685 The @code{F} reply packet has the following format:
32689 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
32691 @var{retcode} is the return code of the system call as hexadecimal value.
32693 @var{errno} is the @code{errno} set by the call, in protocol-specific
32695 This parameter can be omitted if the call was successful.
32697 @var{Ctrl-C flag} is only sent if the user requested a break. In this
32698 case, @var{errno} must be sent as well, even if the call was successful.
32699 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
32706 or, if the call was interrupted before the host call has been performed:
32713 assuming 4 is the protocol-specific representation of @code{EINTR}.
32718 @node The Ctrl-C Message
32719 @subsection The @samp{Ctrl-C} Message
32720 @cindex ctrl-c message, in file-i/o protocol
32722 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
32723 reply packet (@pxref{The F Reply Packet}),
32724 the target should behave as if it had
32725 gotten a break message. The meaning for the target is ``system call
32726 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
32727 (as with a break message) and return to @value{GDBN} with a @code{T02}
32730 It's important for the target to know in which
32731 state the system call was interrupted. There are two possible cases:
32735 The system call hasn't been performed on the host yet.
32738 The system call on the host has been finished.
32742 These two states can be distinguished by the target by the value of the
32743 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
32744 call hasn't been performed. This is equivalent to the @code{EINTR} handling
32745 on POSIX systems. In any other case, the target may presume that the
32746 system call has been finished --- successfully or not --- and should behave
32747 as if the break message arrived right after the system call.
32749 @value{GDBN} must behave reliably. If the system call has not been called
32750 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
32751 @code{errno} in the packet. If the system call on the host has been finished
32752 before the user requests a break, the full action must be finished by
32753 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
32754 The @code{F} packet may only be sent when either nothing has happened
32755 or the full action has been completed.
32758 @subsection Console I/O
32759 @cindex console i/o as part of file-i/o
32761 By default and if not explicitly closed by the target system, the file
32762 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
32763 on the @value{GDBN} console is handled as any other file output operation
32764 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
32765 by @value{GDBN} so that after the target read request from file descriptor
32766 0 all following typing is buffered until either one of the following
32771 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
32773 system call is treated as finished.
32776 The user presses @key{RET}. This is treated as end of input with a trailing
32780 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
32781 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
32785 If the user has typed more characters than fit in the buffer given to
32786 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
32787 either another @code{read(0, @dots{})} is requested by the target, or debugging
32788 is stopped at the user's request.
32791 @node List of Supported Calls
32792 @subsection List of Supported Calls
32793 @cindex list of supported file-i/o calls
32810 @unnumberedsubsubsec open
32811 @cindex open, file-i/o system call
32816 int open(const char *pathname, int flags);
32817 int open(const char *pathname, int flags, mode_t mode);
32821 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
32824 @var{flags} is the bitwise @code{OR} of the following values:
32828 If the file does not exist it will be created. The host
32829 rules apply as far as file ownership and time stamps
32833 When used with @code{O_CREAT}, if the file already exists it is
32834 an error and open() fails.
32837 If the file already exists and the open mode allows
32838 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
32839 truncated to zero length.
32842 The file is opened in append mode.
32845 The file is opened for reading only.
32848 The file is opened for writing only.
32851 The file is opened for reading and writing.
32855 Other bits are silently ignored.
32859 @var{mode} is the bitwise @code{OR} of the following values:
32863 User has read permission.
32866 User has write permission.
32869 Group has read permission.
32872 Group has write permission.
32875 Others have read permission.
32878 Others have write permission.
32882 Other bits are silently ignored.
32885 @item Return value:
32886 @code{open} returns the new file descriptor or -1 if an error
32893 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
32896 @var{pathname} refers to a directory.
32899 The requested access is not allowed.
32902 @var{pathname} was too long.
32905 A directory component in @var{pathname} does not exist.
32908 @var{pathname} refers to a device, pipe, named pipe or socket.
32911 @var{pathname} refers to a file on a read-only filesystem and
32912 write access was requested.
32915 @var{pathname} is an invalid pointer value.
32918 No space on device to create the file.
32921 The process already has the maximum number of files open.
32924 The limit on the total number of files open on the system
32928 The call was interrupted by the user.
32934 @unnumberedsubsubsec close
32935 @cindex close, file-i/o system call
32944 @samp{Fclose,@var{fd}}
32946 @item Return value:
32947 @code{close} returns zero on success, or -1 if an error occurred.
32953 @var{fd} isn't a valid open file descriptor.
32956 The call was interrupted by the user.
32962 @unnumberedsubsubsec read
32963 @cindex read, file-i/o system call
32968 int read(int fd, void *buf, unsigned int count);
32972 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
32974 @item Return value:
32975 On success, the number of bytes read is returned.
32976 Zero indicates end of file. If count is zero, read
32977 returns zero as well. On error, -1 is returned.
32983 @var{fd} is not a valid file descriptor or is not open for
32987 @var{bufptr} is an invalid pointer value.
32990 The call was interrupted by the user.
32996 @unnumberedsubsubsec write
32997 @cindex write, file-i/o system call
33002 int write(int fd, const void *buf, unsigned int count);
33006 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
33008 @item Return value:
33009 On success, the number of bytes written are returned.
33010 Zero indicates nothing was written. On error, -1
33017 @var{fd} is not a valid file descriptor or is not open for
33021 @var{bufptr} is an invalid pointer value.
33024 An attempt was made to write a file that exceeds the
33025 host-specific maximum file size allowed.
33028 No space on device to write the data.
33031 The call was interrupted by the user.
33037 @unnumberedsubsubsec lseek
33038 @cindex lseek, file-i/o system call
33043 long lseek (int fd, long offset, int flag);
33047 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
33049 @var{flag} is one of:
33053 The offset is set to @var{offset} bytes.
33056 The offset is set to its current location plus @var{offset}
33060 The offset is set to the size of the file plus @var{offset}
33064 @item Return value:
33065 On success, the resulting unsigned offset in bytes from
33066 the beginning of the file is returned. Otherwise, a
33067 value of -1 is returned.
33073 @var{fd} is not a valid open file descriptor.
33076 @var{fd} is associated with the @value{GDBN} console.
33079 @var{flag} is not a proper value.
33082 The call was interrupted by the user.
33088 @unnumberedsubsubsec rename
33089 @cindex rename, file-i/o system call
33094 int rename(const char *oldpath, const char *newpath);
33098 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
33100 @item Return value:
33101 On success, zero is returned. On error, -1 is returned.
33107 @var{newpath} is an existing directory, but @var{oldpath} is not a
33111 @var{newpath} is a non-empty directory.
33114 @var{oldpath} or @var{newpath} is a directory that is in use by some
33118 An attempt was made to make a directory a subdirectory
33122 A component used as a directory in @var{oldpath} or new
33123 path is not a directory. Or @var{oldpath} is a directory
33124 and @var{newpath} exists but is not a directory.
33127 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
33130 No access to the file or the path of the file.
33134 @var{oldpath} or @var{newpath} was too long.
33137 A directory component in @var{oldpath} or @var{newpath} does not exist.
33140 The file is on a read-only filesystem.
33143 The device containing the file has no room for the new
33147 The call was interrupted by the user.
33153 @unnumberedsubsubsec unlink
33154 @cindex unlink, file-i/o system call
33159 int unlink(const char *pathname);
33163 @samp{Funlink,@var{pathnameptr}/@var{len}}
33165 @item Return value:
33166 On success, zero is returned. On error, -1 is returned.
33172 No access to the file or the path of the file.
33175 The system does not allow unlinking of directories.
33178 The file @var{pathname} cannot be unlinked because it's
33179 being used by another process.
33182 @var{pathnameptr} is an invalid pointer value.
33185 @var{pathname} was too long.
33188 A directory component in @var{pathname} does not exist.
33191 A component of the path is not a directory.
33194 The file is on a read-only filesystem.
33197 The call was interrupted by the user.
33203 @unnumberedsubsubsec stat/fstat
33204 @cindex fstat, file-i/o system call
33205 @cindex stat, file-i/o system call
33210 int stat(const char *pathname, struct stat *buf);
33211 int fstat(int fd, struct stat *buf);
33215 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
33216 @samp{Ffstat,@var{fd},@var{bufptr}}
33218 @item Return value:
33219 On success, zero is returned. On error, -1 is returned.
33225 @var{fd} is not a valid open file.
33228 A directory component in @var{pathname} does not exist or the
33229 path is an empty string.
33232 A component of the path is not a directory.
33235 @var{pathnameptr} is an invalid pointer value.
33238 No access to the file or the path of the file.
33241 @var{pathname} was too long.
33244 The call was interrupted by the user.
33250 @unnumberedsubsubsec gettimeofday
33251 @cindex gettimeofday, file-i/o system call
33256 int gettimeofday(struct timeval *tv, void *tz);
33260 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
33262 @item Return value:
33263 On success, 0 is returned, -1 otherwise.
33269 @var{tz} is a non-NULL pointer.
33272 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
33278 @unnumberedsubsubsec isatty
33279 @cindex isatty, file-i/o system call
33284 int isatty(int fd);
33288 @samp{Fisatty,@var{fd}}
33290 @item Return value:
33291 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
33297 The call was interrupted by the user.
33302 Note that the @code{isatty} call is treated as a special case: it returns
33303 1 to the target if the file descriptor is attached
33304 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
33305 would require implementing @code{ioctl} and would be more complex than
33310 @unnumberedsubsubsec system
33311 @cindex system, file-i/o system call
33316 int system(const char *command);
33320 @samp{Fsystem,@var{commandptr}/@var{len}}
33322 @item Return value:
33323 If @var{len} is zero, the return value indicates whether a shell is
33324 available. A zero return value indicates a shell is not available.
33325 For non-zero @var{len}, the value returned is -1 on error and the
33326 return status of the command otherwise. Only the exit status of the
33327 command is returned, which is extracted from the host's @code{system}
33328 return value by calling @code{WEXITSTATUS(retval)}. In case
33329 @file{/bin/sh} could not be executed, 127 is returned.
33335 The call was interrupted by the user.
33340 @value{GDBN} takes over the full task of calling the necessary host calls
33341 to perform the @code{system} call. The return value of @code{system} on
33342 the host is simplified before it's returned
33343 to the target. Any termination signal information from the child process
33344 is discarded, and the return value consists
33345 entirely of the exit status of the called command.
33347 Due to security concerns, the @code{system} call is by default refused
33348 by @value{GDBN}. The user has to allow this call explicitly with the
33349 @code{set remote system-call-allowed 1} command.
33352 @item set remote system-call-allowed
33353 @kindex set remote system-call-allowed
33354 Control whether to allow the @code{system} calls in the File I/O
33355 protocol for the remote target. The default is zero (disabled).
33357 @item show remote system-call-allowed
33358 @kindex show remote system-call-allowed
33359 Show whether the @code{system} calls are allowed in the File I/O
33363 @node Protocol-specific Representation of Datatypes
33364 @subsection Protocol-specific Representation of Datatypes
33365 @cindex protocol-specific representation of datatypes, in file-i/o protocol
33368 * Integral Datatypes::
33370 * Memory Transfer::
33375 @node Integral Datatypes
33376 @unnumberedsubsubsec Integral Datatypes
33377 @cindex integral datatypes, in file-i/o protocol
33379 The integral datatypes used in the system calls are @code{int},
33380 @code{unsigned int}, @code{long}, @code{unsigned long},
33381 @code{mode_t}, and @code{time_t}.
33383 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
33384 implemented as 32 bit values in this protocol.
33386 @code{long} and @code{unsigned long} are implemented as 64 bit types.
33388 @xref{Limits}, for corresponding MIN and MAX values (similar to those
33389 in @file{limits.h}) to allow range checking on host and target.
33391 @code{time_t} datatypes are defined as seconds since the Epoch.
33393 All integral datatypes transferred as part of a memory read or write of a
33394 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
33397 @node Pointer Values
33398 @unnumberedsubsubsec Pointer Values
33399 @cindex pointer values, in file-i/o protocol
33401 Pointers to target data are transmitted as they are. An exception
33402 is made for pointers to buffers for which the length isn't
33403 transmitted as part of the function call, namely strings. Strings
33404 are transmitted as a pointer/length pair, both as hex values, e.g.@:
33411 which is a pointer to data of length 18 bytes at position 0x1aaf.
33412 The length is defined as the full string length in bytes, including
33413 the trailing null byte. For example, the string @code{"hello world"}
33414 at address 0x123456 is transmitted as
33420 @node Memory Transfer
33421 @unnumberedsubsubsec Memory Transfer
33422 @cindex memory transfer, in file-i/o protocol
33424 Structured data which is transferred using a memory read or write (for
33425 example, a @code{struct stat}) is expected to be in a protocol-specific format
33426 with all scalar multibyte datatypes being big endian. Translation to
33427 this representation needs to be done both by the target before the @code{F}
33428 packet is sent, and by @value{GDBN} before
33429 it transfers memory to the target. Transferred pointers to structured
33430 data should point to the already-coerced data at any time.
33434 @unnumberedsubsubsec struct stat
33435 @cindex struct stat, in file-i/o protocol
33437 The buffer of type @code{struct stat} used by the target and @value{GDBN}
33438 is defined as follows:
33442 unsigned int st_dev; /* device */
33443 unsigned int st_ino; /* inode */
33444 mode_t st_mode; /* protection */
33445 unsigned int st_nlink; /* number of hard links */
33446 unsigned int st_uid; /* user ID of owner */
33447 unsigned int st_gid; /* group ID of owner */
33448 unsigned int st_rdev; /* device type (if inode device) */
33449 unsigned long st_size; /* total size, in bytes */
33450 unsigned long st_blksize; /* blocksize for filesystem I/O */
33451 unsigned long st_blocks; /* number of blocks allocated */
33452 time_t st_atime; /* time of last access */
33453 time_t st_mtime; /* time of last modification */
33454 time_t st_ctime; /* time of last change */
33458 The integral datatypes conform to the definitions given in the
33459 appropriate section (see @ref{Integral Datatypes}, for details) so this
33460 structure is of size 64 bytes.
33462 The values of several fields have a restricted meaning and/or
33468 A value of 0 represents a file, 1 the console.
33471 No valid meaning for the target. Transmitted unchanged.
33474 Valid mode bits are described in @ref{Constants}. Any other
33475 bits have currently no meaning for the target.
33480 No valid meaning for the target. Transmitted unchanged.
33485 These values have a host and file system dependent
33486 accuracy. Especially on Windows hosts, the file system may not
33487 support exact timing values.
33490 The target gets a @code{struct stat} of the above representation and is
33491 responsible for coercing it to the target representation before
33494 Note that due to size differences between the host, target, and protocol
33495 representations of @code{struct stat} members, these members could eventually
33496 get truncated on the target.
33498 @node struct timeval
33499 @unnumberedsubsubsec struct timeval
33500 @cindex struct timeval, in file-i/o protocol
33502 The buffer of type @code{struct timeval} used by the File-I/O protocol
33503 is defined as follows:
33507 time_t tv_sec; /* second */
33508 long tv_usec; /* microsecond */
33512 The integral datatypes conform to the definitions given in the
33513 appropriate section (see @ref{Integral Datatypes}, for details) so this
33514 structure is of size 8 bytes.
33517 @subsection Constants
33518 @cindex constants, in file-i/o protocol
33520 The following values are used for the constants inside of the
33521 protocol. @value{GDBN} and target are responsible for translating these
33522 values before and after the call as needed.
33533 @unnumberedsubsubsec Open Flags
33534 @cindex open flags, in file-i/o protocol
33536 All values are given in hexadecimal representation.
33548 @node mode_t Values
33549 @unnumberedsubsubsec mode_t Values
33550 @cindex mode_t values, in file-i/o protocol
33552 All values are given in octal representation.
33569 @unnumberedsubsubsec Errno Values
33570 @cindex errno values, in file-i/o protocol
33572 All values are given in decimal representation.
33597 @code{EUNKNOWN} is used as a fallback error value if a host system returns
33598 any error value not in the list of supported error numbers.
33601 @unnumberedsubsubsec Lseek Flags
33602 @cindex lseek flags, in file-i/o protocol
33611 @unnumberedsubsubsec Limits
33612 @cindex limits, in file-i/o protocol
33614 All values are given in decimal representation.
33617 INT_MIN -2147483648
33619 UINT_MAX 4294967295
33620 LONG_MIN -9223372036854775808
33621 LONG_MAX 9223372036854775807
33622 ULONG_MAX 18446744073709551615
33625 @node File-I/O Examples
33626 @subsection File-I/O Examples
33627 @cindex file-i/o examples
33629 Example sequence of a write call, file descriptor 3, buffer is at target
33630 address 0x1234, 6 bytes should be written:
33633 <- @code{Fwrite,3,1234,6}
33634 @emph{request memory read from target}
33637 @emph{return "6 bytes written"}
33641 Example sequence of a read call, file descriptor 3, buffer is at target
33642 address 0x1234, 6 bytes should be read:
33645 <- @code{Fread,3,1234,6}
33646 @emph{request memory write to target}
33647 -> @code{X1234,6:XXXXXX}
33648 @emph{return "6 bytes read"}
33652 Example sequence of a read call, call fails on the host due to invalid
33653 file descriptor (@code{EBADF}):
33656 <- @code{Fread,3,1234,6}
33660 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
33664 <- @code{Fread,3,1234,6}
33669 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
33673 <- @code{Fread,3,1234,6}
33674 -> @code{X1234,6:XXXXXX}
33678 @node Library List Format
33679 @section Library List Format
33680 @cindex library list format, remote protocol
33682 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
33683 same process as your application to manage libraries. In this case,
33684 @value{GDBN} can use the loader's symbol table and normal memory
33685 operations to maintain a list of shared libraries. On other
33686 platforms, the operating system manages loaded libraries.
33687 @value{GDBN} can not retrieve the list of currently loaded libraries
33688 through memory operations, so it uses the @samp{qXfer:libraries:read}
33689 packet (@pxref{qXfer library list read}) instead. The remote stub
33690 queries the target's operating system and reports which libraries
33693 The @samp{qXfer:libraries:read} packet returns an XML document which
33694 lists loaded libraries and their offsets. Each library has an
33695 associated name and one or more segment or section base addresses,
33696 which report where the library was loaded in memory.
33698 For the common case of libraries that are fully linked binaries, the
33699 library should have a list of segments. If the target supports
33700 dynamic linking of a relocatable object file, its library XML element
33701 should instead include a list of allocated sections. The segment or
33702 section bases are start addresses, not relocation offsets; they do not
33703 depend on the library's link-time base addresses.
33705 @value{GDBN} must be linked with the Expat library to support XML
33706 library lists. @xref{Expat}.
33708 A simple memory map, with one loaded library relocated by a single
33709 offset, looks like this:
33713 <library name="/lib/libc.so.6">
33714 <segment address="0x10000000"/>
33719 Another simple memory map, with one loaded library with three
33720 allocated sections (.text, .data, .bss), looks like this:
33724 <library name="sharedlib.o">
33725 <section address="0x10000000"/>
33726 <section address="0x20000000"/>
33727 <section address="0x30000000"/>
33732 The format of a library list is described by this DTD:
33735 <!-- library-list: Root element with versioning -->
33736 <!ELEMENT library-list (library)*>
33737 <!ATTLIST library-list version CDATA #FIXED "1.0">
33738 <!ELEMENT library (segment*, section*)>
33739 <!ATTLIST library name CDATA #REQUIRED>
33740 <!ELEMENT segment EMPTY>
33741 <!ATTLIST segment address CDATA #REQUIRED>
33742 <!ELEMENT section EMPTY>
33743 <!ATTLIST section address CDATA #REQUIRED>
33746 In addition, segments and section descriptors cannot be mixed within a
33747 single library element, and you must supply at least one segment or
33748 section for each library.
33750 @node Memory Map Format
33751 @section Memory Map Format
33752 @cindex memory map format
33754 To be able to write into flash memory, @value{GDBN} needs to obtain a
33755 memory map from the target. This section describes the format of the
33758 The memory map is obtained using the @samp{qXfer:memory-map:read}
33759 (@pxref{qXfer memory map read}) packet and is an XML document that
33760 lists memory regions.
33762 @value{GDBN} must be linked with the Expat library to support XML
33763 memory maps. @xref{Expat}.
33765 The top-level structure of the document is shown below:
33768 <?xml version="1.0"?>
33769 <!DOCTYPE memory-map
33770 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
33771 "http://sourceware.org/gdb/gdb-memory-map.dtd">
33777 Each region can be either:
33782 A region of RAM starting at @var{addr} and extending for @var{length}
33786 <memory type="ram" start="@var{addr}" length="@var{length}"/>
33791 A region of read-only memory:
33794 <memory type="rom" start="@var{addr}" length="@var{length}"/>
33799 A region of flash memory, with erasure blocks @var{blocksize}
33803 <memory type="flash" start="@var{addr}" length="@var{length}">
33804 <property name="blocksize">@var{blocksize}</property>
33810 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
33811 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
33812 packets to write to addresses in such ranges.
33814 The formal DTD for memory map format is given below:
33817 <!-- ................................................... -->
33818 <!-- Memory Map XML DTD ................................ -->
33819 <!-- File: memory-map.dtd .............................. -->
33820 <!-- .................................... .............. -->
33821 <!-- memory-map.dtd -->
33822 <!-- memory-map: Root element with versioning -->
33823 <!ELEMENT memory-map (memory | property)>
33824 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
33825 <!ELEMENT memory (property)>
33826 <!-- memory: Specifies a memory region,
33827 and its type, or device. -->
33828 <!ATTLIST memory type CDATA #REQUIRED
33829 start CDATA #REQUIRED
33830 length CDATA #REQUIRED
33831 device CDATA #IMPLIED>
33832 <!-- property: Generic attribute tag -->
33833 <!ELEMENT property (#PCDATA | property)*>
33834 <!ATTLIST property name CDATA #REQUIRED>
33837 @node Thread List Format
33838 @section Thread List Format
33839 @cindex thread list format
33841 To efficiently update the list of threads and their attributes,
33842 @value{GDBN} issues the @samp{qXfer:threads:read} packet
33843 (@pxref{qXfer threads read}) and obtains the XML document with
33844 the following structure:
33847 <?xml version="1.0"?>
33849 <thread id="id" core="0">
33850 ... description ...
33855 Each @samp{thread} element must have the @samp{id} attribute that
33856 identifies the thread (@pxref{thread-id syntax}). The
33857 @samp{core} attribute, if present, specifies which processor core
33858 the thread was last executing on. The content of the of @samp{thread}
33859 element is interpreted as human-readable auxilliary information.
33861 @include agentexpr.texi
33863 @node Trace File Format
33864 @appendix Trace File Format
33865 @cindex trace file format
33867 The trace file comes in three parts: a header, a textual description
33868 section, and a trace frame section with binary data.
33870 The header has the form @code{\x7fTRACE0\n}. The first byte is
33871 @code{0x7f} so as to indicate that the file contains binary data,
33872 while the @code{0} is a version number that may have different values
33875 The description section consists of multiple lines of @sc{ascii} text
33876 separated by newline characters (@code{0xa}). The lines may include a
33877 variety of optional descriptive or context-setting information, such
33878 as tracepoint definitions or register set size. @value{GDBN} will
33879 ignore any line that it does not recognize. An empty line marks the end
33882 @c FIXME add some specific types of data
33884 The trace frame section consists of a number of consecutive frames.
33885 Each frame begins with a two-byte tracepoint number, followed by a
33886 four-byte size giving the amount of data in the frame. The data in
33887 the frame consists of a number of blocks, each introduced by a
33888 character indicating its type (at least register, memory, and trace
33889 state variable). The data in this section is raw binary, not a
33890 hexadecimal or other encoding; its endianness matches the target's
33893 @c FIXME bi-arch may require endianness/arch info in description section
33896 @item R @var{bytes}
33897 Register block. The number and ordering of bytes matches that of a
33898 @code{g} packet in the remote protocol. Note that these are the
33899 actual bytes, in target order and @value{GDBN} register order, not a
33900 hexadecimal encoding.
33902 @item M @var{address} @var{length} @var{bytes}...
33903 Memory block. This is a contiguous block of memory, at the 8-byte
33904 address @var{address}, with a 2-byte length @var{length}, followed by
33905 @var{length} bytes.
33907 @item V @var{number} @var{value}
33908 Trace state variable block. This records the 8-byte signed value
33909 @var{value} of trace state variable numbered @var{number}.
33913 Future enhancements of the trace file format may include additional types
33916 @node Target Descriptions
33917 @appendix Target Descriptions
33918 @cindex target descriptions
33920 @strong{Warning:} target descriptions are still under active development,
33921 and the contents and format may change between @value{GDBN} releases.
33922 The format is expected to stabilize in the future.
33924 One of the challenges of using @value{GDBN} to debug embedded systems
33925 is that there are so many minor variants of each processor
33926 architecture in use. It is common practice for vendors to start with
33927 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
33928 and then make changes to adapt it to a particular market niche. Some
33929 architectures have hundreds of variants, available from dozens of
33930 vendors. This leads to a number of problems:
33934 With so many different customized processors, it is difficult for
33935 the @value{GDBN} maintainers to keep up with the changes.
33937 Since individual variants may have short lifetimes or limited
33938 audiences, it may not be worthwhile to carry information about every
33939 variant in the @value{GDBN} source tree.
33941 When @value{GDBN} does support the architecture of the embedded system
33942 at hand, the task of finding the correct architecture name to give the
33943 @command{set architecture} command can be error-prone.
33946 To address these problems, the @value{GDBN} remote protocol allows a
33947 target system to not only identify itself to @value{GDBN}, but to
33948 actually describe its own features. This lets @value{GDBN} support
33949 processor variants it has never seen before --- to the extent that the
33950 descriptions are accurate, and that @value{GDBN} understands them.
33952 @value{GDBN} must be linked with the Expat library to support XML
33953 target descriptions. @xref{Expat}.
33956 * Retrieving Descriptions:: How descriptions are fetched from a target.
33957 * Target Description Format:: The contents of a target description.
33958 * Predefined Target Types:: Standard types available for target
33960 * Standard Target Features:: Features @value{GDBN} knows about.
33963 @node Retrieving Descriptions
33964 @section Retrieving Descriptions
33966 Target descriptions can be read from the target automatically, or
33967 specified by the user manually. The default behavior is to read the
33968 description from the target. @value{GDBN} retrieves it via the remote
33969 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
33970 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
33971 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
33972 XML document, of the form described in @ref{Target Description
33975 Alternatively, you can specify a file to read for the target description.
33976 If a file is set, the target will not be queried. The commands to
33977 specify a file are:
33980 @cindex set tdesc filename
33981 @item set tdesc filename @var{path}
33982 Read the target description from @var{path}.
33984 @cindex unset tdesc filename
33985 @item unset tdesc filename
33986 Do not read the XML target description from a file. @value{GDBN}
33987 will use the description supplied by the current target.
33989 @cindex show tdesc filename
33990 @item show tdesc filename
33991 Show the filename to read for a target description, if any.
33995 @node Target Description Format
33996 @section Target Description Format
33997 @cindex target descriptions, XML format
33999 A target description annex is an @uref{http://www.w3.org/XML/, XML}
34000 document which complies with the Document Type Definition provided in
34001 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
34002 means you can use generally available tools like @command{xmllint} to
34003 check that your feature descriptions are well-formed and valid.
34004 However, to help people unfamiliar with XML write descriptions for
34005 their targets, we also describe the grammar here.
34007 Target descriptions can identify the architecture of the remote target
34008 and (for some architectures) provide information about custom register
34009 sets. They can also identify the OS ABI of the remote target.
34010 @value{GDBN} can use this information to autoconfigure for your
34011 target, or to warn you if you connect to an unsupported target.
34013 Here is a simple target description:
34016 <target version="1.0">
34017 <architecture>i386:x86-64</architecture>
34022 This minimal description only says that the target uses
34023 the x86-64 architecture.
34025 A target description has the following overall form, with [ ] marking
34026 optional elements and @dots{} marking repeatable elements. The elements
34027 are explained further below.
34030 <?xml version="1.0"?>
34031 <!DOCTYPE target SYSTEM "gdb-target.dtd">
34032 <target version="1.0">
34033 @r{[}@var{architecture}@r{]}
34034 @r{[}@var{osabi}@r{]}
34035 @r{[}@var{compatible}@r{]}
34036 @r{[}@var{feature}@dots{}@r{]}
34041 The description is generally insensitive to whitespace and line
34042 breaks, under the usual common-sense rules. The XML version
34043 declaration and document type declaration can generally be omitted
34044 (@value{GDBN} does not require them), but specifying them may be
34045 useful for XML validation tools. The @samp{version} attribute for
34046 @samp{<target>} may also be omitted, but we recommend
34047 including it; if future versions of @value{GDBN} use an incompatible
34048 revision of @file{gdb-target.dtd}, they will detect and report
34049 the version mismatch.
34051 @subsection Inclusion
34052 @cindex target descriptions, inclusion
34055 @cindex <xi:include>
34058 It can sometimes be valuable to split a target description up into
34059 several different annexes, either for organizational purposes, or to
34060 share files between different possible target descriptions. You can
34061 divide a description into multiple files by replacing any element of
34062 the target description with an inclusion directive of the form:
34065 <xi:include href="@var{document}"/>
34069 When @value{GDBN} encounters an element of this form, it will retrieve
34070 the named XML @var{document}, and replace the inclusion directive with
34071 the contents of that document. If the current description was read
34072 using @samp{qXfer}, then so will be the included document;
34073 @var{document} will be interpreted as the name of an annex. If the
34074 current description was read from a file, @value{GDBN} will look for
34075 @var{document} as a file in the same directory where it found the
34076 original description.
34078 @subsection Architecture
34079 @cindex <architecture>
34081 An @samp{<architecture>} element has this form:
34084 <architecture>@var{arch}</architecture>
34087 @var{arch} is one of the architectures from the set accepted by
34088 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
34091 @cindex @code{<osabi>}
34093 This optional field was introduced in @value{GDBN} version 7.0.
34094 Previous versions of @value{GDBN} ignore it.
34096 An @samp{<osabi>} element has this form:
34099 <osabi>@var{abi-name}</osabi>
34102 @var{abi-name} is an OS ABI name from the same selection accepted by
34103 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
34105 @subsection Compatible Architecture
34106 @cindex @code{<compatible>}
34108 This optional field was introduced in @value{GDBN} version 7.0.
34109 Previous versions of @value{GDBN} ignore it.
34111 A @samp{<compatible>} element has this form:
34114 <compatible>@var{arch}</compatible>
34117 @var{arch} is one of the architectures from the set accepted by
34118 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
34120 A @samp{<compatible>} element is used to specify that the target
34121 is able to run binaries in some other than the main target architecture
34122 given by the @samp{<architecture>} element. For example, on the
34123 Cell Broadband Engine, the main architecture is @code{powerpc:common}
34124 or @code{powerpc:common64}, but the system is able to run binaries
34125 in the @code{spu} architecture as well. The way to describe this
34126 capability with @samp{<compatible>} is as follows:
34129 <architecture>powerpc:common</architecture>
34130 <compatible>spu</compatible>
34133 @subsection Features
34136 Each @samp{<feature>} describes some logical portion of the target
34137 system. Features are currently used to describe available CPU
34138 registers and the types of their contents. A @samp{<feature>} element
34142 <feature name="@var{name}">
34143 @r{[}@var{type}@dots{}@r{]}
34149 Each feature's name should be unique within the description. The name
34150 of a feature does not matter unless @value{GDBN} has some special
34151 knowledge of the contents of that feature; if it does, the feature
34152 should have its standard name. @xref{Standard Target Features}.
34156 Any register's value is a collection of bits which @value{GDBN} must
34157 interpret. The default interpretation is a two's complement integer,
34158 but other types can be requested by name in the register description.
34159 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
34160 Target Types}), and the description can define additional composite types.
34162 Each type element must have an @samp{id} attribute, which gives
34163 a unique (within the containing @samp{<feature>}) name to the type.
34164 Types must be defined before they are used.
34167 Some targets offer vector registers, which can be treated as arrays
34168 of scalar elements. These types are written as @samp{<vector>} elements,
34169 specifying the array element type, @var{type}, and the number of elements,
34173 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
34177 If a register's value is usefully viewed in multiple ways, define it
34178 with a union type containing the useful representations. The
34179 @samp{<union>} element contains one or more @samp{<field>} elements,
34180 each of which has a @var{name} and a @var{type}:
34183 <union id="@var{id}">
34184 <field name="@var{name}" type="@var{type}"/>
34190 If a register's value is composed from several separate values, define
34191 it with a structure type. There are two forms of the @samp{<struct>}
34192 element; a @samp{<struct>} element must either contain only bitfields
34193 or contain no bitfields. If the structure contains only bitfields,
34194 its total size in bytes must be specified, each bitfield must have an
34195 explicit start and end, and bitfields are automatically assigned an
34196 integer type. The field's @var{start} should be less than or
34197 equal to its @var{end}, and zero represents the least significant bit.
34200 <struct id="@var{id}" size="@var{size}">
34201 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
34206 If the structure contains no bitfields, then each field has an
34207 explicit type, and no implicit padding is added.
34210 <struct id="@var{id}">
34211 <field name="@var{name}" type="@var{type}"/>
34217 If a register's value is a series of single-bit flags, define it with
34218 a flags type. The @samp{<flags>} element has an explicit @var{size}
34219 and contains one or more @samp{<field>} elements. Each field has a
34220 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
34224 <flags id="@var{id}" size="@var{size}">
34225 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
34230 @subsection Registers
34233 Each register is represented as an element with this form:
34236 <reg name="@var{name}"
34237 bitsize="@var{size}"
34238 @r{[}regnum="@var{num}"@r{]}
34239 @r{[}save-restore="@var{save-restore}"@r{]}
34240 @r{[}type="@var{type}"@r{]}
34241 @r{[}group="@var{group}"@r{]}/>
34245 The components are as follows:
34250 The register's name; it must be unique within the target description.
34253 The register's size, in bits.
34256 The register's number. If omitted, a register's number is one greater
34257 than that of the previous register (either in the current feature or in
34258 a preceeding feature); the first register in the target description
34259 defaults to zero. This register number is used to read or write
34260 the register; e.g.@: it is used in the remote @code{p} and @code{P}
34261 packets, and registers appear in the @code{g} and @code{G} packets
34262 in order of increasing register number.
34265 Whether the register should be preserved across inferior function
34266 calls; this must be either @code{yes} or @code{no}. The default is
34267 @code{yes}, which is appropriate for most registers except for
34268 some system control registers; this is not related to the target's
34272 The type of the register. @var{type} may be a predefined type, a type
34273 defined in the current feature, or one of the special types @code{int}
34274 and @code{float}. @code{int} is an integer type of the correct size
34275 for @var{bitsize}, and @code{float} is a floating point type (in the
34276 architecture's normal floating point format) of the correct size for
34277 @var{bitsize}. The default is @code{int}.
34280 The register group to which this register belongs. @var{group} must
34281 be either @code{general}, @code{float}, or @code{vector}. If no
34282 @var{group} is specified, @value{GDBN} will not display the register
34283 in @code{info registers}.
34287 @node Predefined Target Types
34288 @section Predefined Target Types
34289 @cindex target descriptions, predefined types
34291 Type definitions in the self-description can build up composite types
34292 from basic building blocks, but can not define fundamental types. Instead,
34293 standard identifiers are provided by @value{GDBN} for the fundamental
34294 types. The currently supported types are:
34303 Signed integer types holding the specified number of bits.
34310 Unsigned integer types holding the specified number of bits.
34314 Pointers to unspecified code and data. The program counter and
34315 any dedicated return address register may be marked as code
34316 pointers; printing a code pointer converts it into a symbolic
34317 address. The stack pointer and any dedicated address registers
34318 may be marked as data pointers.
34321 Single precision IEEE floating point.
34324 Double precision IEEE floating point.
34327 The 12-byte extended precision format used by ARM FPA registers.
34330 The 10-byte extended precision format used by x87 registers.
34333 32bit @sc{eflags} register used by x86.
34336 32bit @sc{mxcsr} register used by x86.
34340 @node Standard Target Features
34341 @section Standard Target Features
34342 @cindex target descriptions, standard features
34344 A target description must contain either no registers or all the
34345 target's registers. If the description contains no registers, then
34346 @value{GDBN} will assume a default register layout, selected based on
34347 the architecture. If the description contains any registers, the
34348 default layout will not be used; the standard registers must be
34349 described in the target description, in such a way that @value{GDBN}
34350 can recognize them.
34352 This is accomplished by giving specific names to feature elements
34353 which contain standard registers. @value{GDBN} will look for features
34354 with those names and verify that they contain the expected registers;
34355 if any known feature is missing required registers, or if any required
34356 feature is missing, @value{GDBN} will reject the target
34357 description. You can add additional registers to any of the
34358 standard features --- @value{GDBN} will display them just as if
34359 they were added to an unrecognized feature.
34361 This section lists the known features and their expected contents.
34362 Sample XML documents for these features are included in the
34363 @value{GDBN} source tree, in the directory @file{gdb/features}.
34365 Names recognized by @value{GDBN} should include the name of the
34366 company or organization which selected the name, and the overall
34367 architecture to which the feature applies; so e.g.@: the feature
34368 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
34370 The names of registers are not case sensitive for the purpose
34371 of recognizing standard features, but @value{GDBN} will only display
34372 registers using the capitalization used in the description.
34379 * PowerPC Features::
34384 @subsection ARM Features
34385 @cindex target descriptions, ARM features
34387 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
34388 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
34389 @samp{lr}, @samp{pc}, and @samp{cpsr}.
34391 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
34392 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
34394 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
34395 it should contain at least registers @samp{wR0} through @samp{wR15} and
34396 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
34397 @samp{wCSSF}, and @samp{wCASF} registers are optional.
34399 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
34400 should contain at least registers @samp{d0} through @samp{d15}. If
34401 they are present, @samp{d16} through @samp{d31} should also be included.
34402 @value{GDBN} will synthesize the single-precision registers from
34403 halves of the double-precision registers.
34405 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
34406 need to contain registers; it instructs @value{GDBN} to display the
34407 VFP double-precision registers as vectors and to synthesize the
34408 quad-precision registers from pairs of double-precision registers.
34409 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
34410 be present and include 32 double-precision registers.
34412 @node i386 Features
34413 @subsection i386 Features
34414 @cindex target descriptions, i386 features
34416 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
34417 targets. It should describe the following registers:
34421 @samp{eax} through @samp{edi} plus @samp{eip} for i386
34423 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
34425 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
34426 @samp{fs}, @samp{gs}
34428 @samp{st0} through @samp{st7}
34430 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
34431 @samp{foseg}, @samp{fooff} and @samp{fop}
34434 The register sets may be different, depending on the target.
34436 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
34437 describe registers:
34441 @samp{xmm0} through @samp{xmm7} for i386
34443 @samp{xmm0} through @samp{xmm15} for amd64
34448 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
34449 @samp{org.gnu.gdb.i386.sse} feature. It should
34450 describe the upper 128 bits of @sc{ymm} registers:
34454 @samp{ymm0h} through @samp{ymm7h} for i386
34456 @samp{ymm0h} through @samp{ymm15h} for amd64
34460 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
34461 describe a single register, @samp{orig_eax}.
34463 @node MIPS Features
34464 @subsection MIPS Features
34465 @cindex target descriptions, MIPS features
34467 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
34468 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
34469 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
34472 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
34473 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
34474 registers. They may be 32-bit or 64-bit depending on the target.
34476 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
34477 it may be optional in a future version of @value{GDBN}. It should
34478 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
34479 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
34481 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
34482 contain a single register, @samp{restart}, which is used by the
34483 Linux kernel to control restartable syscalls.
34485 @node M68K Features
34486 @subsection M68K Features
34487 @cindex target descriptions, M68K features
34490 @item @samp{org.gnu.gdb.m68k.core}
34491 @itemx @samp{org.gnu.gdb.coldfire.core}
34492 @itemx @samp{org.gnu.gdb.fido.core}
34493 One of those features must be always present.
34494 The feature that is present determines which flavor of m68k is
34495 used. The feature that is present should contain registers
34496 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
34497 @samp{sp}, @samp{ps} and @samp{pc}.
34499 @item @samp{org.gnu.gdb.coldfire.fp}
34500 This feature is optional. If present, it should contain registers
34501 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
34505 @node PowerPC Features
34506 @subsection PowerPC Features
34507 @cindex target descriptions, PowerPC features
34509 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
34510 targets. It should contain registers @samp{r0} through @samp{r31},
34511 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
34512 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
34514 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
34515 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
34517 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
34518 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
34521 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
34522 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
34523 will combine these registers with the floating point registers
34524 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
34525 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
34526 through @samp{vs63}, the set of vector registers for POWER7.
34528 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
34529 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
34530 @samp{spefscr}. SPE targets should provide 32-bit registers in
34531 @samp{org.gnu.gdb.power.core} and provide the upper halves in
34532 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
34533 these to present registers @samp{ev0} through @samp{ev31} to the
34536 @node Operating System Information
34537 @appendix Operating System Information
34538 @cindex operating system information
34544 Users of @value{GDBN} often wish to obtain information about the state of
34545 the operating system running on the target---for example the list of
34546 processes, or the list of open files. This section describes the
34547 mechanism that makes it possible. This mechanism is similar to the
34548 target features mechanism (@pxref{Target Descriptions}), but focuses
34549 on a different aspect of target.
34551 Operating system information is retrived from the target via the
34552 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
34553 read}). The object name in the request should be @samp{osdata}, and
34554 the @var{annex} identifies the data to be fetched.
34557 @appendixsection Process list
34558 @cindex operating system information, process list
34560 When requesting the process list, the @var{annex} field in the
34561 @samp{qXfer} request should be @samp{processes}. The returned data is
34562 an XML document. The formal syntax of this document is defined in
34563 @file{gdb/features/osdata.dtd}.
34565 An example document is:
34568 <?xml version="1.0"?>
34569 <!DOCTYPE target SYSTEM "osdata.dtd">
34570 <osdata type="processes">
34572 <column name="pid">1</column>
34573 <column name="user">root</column>
34574 <column name="command">/sbin/init</column>
34575 <column name="cores">1,2,3</column>
34580 Each item should include a column whose name is @samp{pid}. The value
34581 of that column should identify the process on the target. The
34582 @samp{user} and @samp{command} columns are optional, and will be
34583 displayed by @value{GDBN}. The @samp{cores} column, if present,
34584 should contain a comma-separated list of cores that this process
34585 is running on. Target may provide additional columns,
34586 which @value{GDBN} currently ignores.
34600 % I think something like @colophon should be in texinfo. In the
34602 \long\def\colophon{\hbox to0pt{}\vfill
34603 \centerline{The body of this manual is set in}
34604 \centerline{\fontname\tenrm,}
34605 \centerline{with headings in {\bf\fontname\tenbf}}
34606 \centerline{and examples in {\tt\fontname\tentt}.}
34607 \centerline{{\it\fontname\tenit\/},}
34608 \centerline{{\bf\fontname\tenbf}, and}
34609 \centerline{{\sl\fontname\tensl\/}}
34610 \centerline{are used for emphasis.}\vfill}
34612 % Blame: doc@cygnus.com, 1991.