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 * Error in Breakpoints:: ``Cannot insert breakpoints''
3251 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3255 @subsection Setting Breakpoints
3257 @c FIXME LMB what does GDB do if no code on line of breakpt?
3258 @c consider in particular declaration with/without initialization.
3260 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3263 @kindex b @r{(@code{break})}
3264 @vindex $bpnum@r{, convenience variable}
3265 @cindex latest breakpoint
3266 Breakpoints are set with the @code{break} command (abbreviated
3267 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3268 number of the breakpoint you've set most recently; see @ref{Convenience
3269 Vars,, Convenience Variables}, for a discussion of what you can do with
3270 convenience variables.
3273 @item break @var{location}
3274 Set a breakpoint at the given @var{location}, which can specify a
3275 function name, a line number, or an address of an instruction.
3276 (@xref{Specify Location}, for a list of all the possible ways to
3277 specify a @var{location}.) The breakpoint will stop your program just
3278 before it executes any of the code in the specified @var{location}.
3280 When using source languages that permit overloading of symbols, such as
3281 C@t{++}, a function name may refer to more than one possible place to break.
3282 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3285 It is also possible to insert a breakpoint that will stop the program
3286 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3287 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3290 When called without any arguments, @code{break} sets a breakpoint at
3291 the next instruction to be executed in the selected stack frame
3292 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3293 innermost, this makes your program stop as soon as control
3294 returns to that frame. This is similar to the effect of a
3295 @code{finish} command in the frame inside the selected frame---except
3296 that @code{finish} does not leave an active breakpoint. If you use
3297 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3298 the next time it reaches the current location; this may be useful
3301 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3302 least one instruction has been executed. If it did not do this, you
3303 would be unable to proceed past a breakpoint without first disabling the
3304 breakpoint. This rule applies whether or not the breakpoint already
3305 existed when your program stopped.
3307 @item break @dots{} if @var{cond}
3308 Set a breakpoint with condition @var{cond}; evaluate the expression
3309 @var{cond} each time the breakpoint is reached, and stop only if the
3310 value is nonzero---that is, if @var{cond} evaluates as true.
3311 @samp{@dots{}} stands for one of the possible arguments described
3312 above (or no argument) specifying where to break. @xref{Conditions,
3313 ,Break Conditions}, for more information on breakpoint conditions.
3316 @item tbreak @var{args}
3317 Set a breakpoint enabled only for one stop. @var{args} are the
3318 same as for the @code{break} command, and the breakpoint is set in the same
3319 way, but the breakpoint is automatically deleted after the first time your
3320 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3323 @cindex hardware breakpoints
3324 @item hbreak @var{args}
3325 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3326 @code{break} command and the breakpoint is set in the same way, but the
3327 breakpoint requires hardware support and some target hardware may not
3328 have this support. The main purpose of this is EPROM/ROM code
3329 debugging, so you can set a breakpoint at an instruction without
3330 changing the instruction. This can be used with the new trap-generation
3331 provided by SPARClite DSU and most x86-based targets. These targets
3332 will generate traps when a program accesses some data or instruction
3333 address that is assigned to the debug registers. However the hardware
3334 breakpoint registers can take a limited number of breakpoints. For
3335 example, on the DSU, only two data breakpoints can be set at a time, and
3336 @value{GDBN} will reject this command if more than two are used. Delete
3337 or disable unused hardware breakpoints before setting new ones
3338 (@pxref{Disabling, ,Disabling Breakpoints}).
3339 @xref{Conditions, ,Break Conditions}.
3340 For remote targets, you can restrict the number of hardware
3341 breakpoints @value{GDBN} will use, see @ref{set remote
3342 hardware-breakpoint-limit}.
3345 @item thbreak @var{args}
3346 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3347 are the same as for the @code{hbreak} command and the breakpoint is set in
3348 the same way. However, like the @code{tbreak} command,
3349 the breakpoint is automatically deleted after the
3350 first time your program stops there. Also, like the @code{hbreak}
3351 command, the breakpoint requires hardware support and some target hardware
3352 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3353 See also @ref{Conditions, ,Break Conditions}.
3356 @cindex regular expression
3357 @cindex breakpoints in functions matching a regexp
3358 @cindex set breakpoints in many functions
3359 @item rbreak @var{regex}
3360 Set breakpoints on all functions matching the regular expression
3361 @var{regex}. This command sets an unconditional breakpoint on all
3362 matches, printing a list of all breakpoints it set. Once these
3363 breakpoints are set, they are treated just like the breakpoints set with
3364 the @code{break} command. You can delete them, disable them, or make
3365 them conditional the same way as any other breakpoint.
3367 The syntax of the regular expression is the standard one used with tools
3368 like @file{grep}. Note that this is different from the syntax used by
3369 shells, so for instance @code{foo*} matches all functions that include
3370 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3371 @code{.*} leading and trailing the regular expression you supply, so to
3372 match only functions that begin with @code{foo}, use @code{^foo}.
3374 @cindex non-member C@t{++} functions, set breakpoint in
3375 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3376 breakpoints on overloaded functions that are not members of any special
3379 @cindex set breakpoints on all functions
3380 The @code{rbreak} command can be used to set breakpoints in
3381 @strong{all} the functions in a program, like this:
3384 (@value{GDBP}) rbreak .
3387 @kindex info breakpoints
3388 @cindex @code{$_} and @code{info breakpoints}
3389 @item info breakpoints @r{[}@var{n}@r{]}
3390 @itemx info break @r{[}@var{n}@r{]}
3391 Print a table of all breakpoints, watchpoints, and catchpoints set and
3392 not deleted. Optional argument @var{n} means print information only
3393 about the specified breakpoint (or watchpoint or catchpoint). For
3394 each breakpoint, following columns are printed:
3397 @item Breakpoint Numbers
3399 Breakpoint, watchpoint, or catchpoint.
3401 Whether the breakpoint is marked to be disabled or deleted when hit.
3402 @item Enabled or Disabled
3403 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3404 that are not enabled.
3406 Where the breakpoint is in your program, as a memory address. For a
3407 pending breakpoint whose address is not yet known, this field will
3408 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3409 library that has the symbol or line referred by breakpoint is loaded.
3410 See below for details. A breakpoint with several locations will
3411 have @samp{<MULTIPLE>} in this field---see below for details.
3413 Where the breakpoint is in the source for your program, as a file and
3414 line number. For a pending breakpoint, the original string passed to
3415 the breakpoint command will be listed as it cannot be resolved until
3416 the appropriate shared library is loaded in the future.
3420 If a breakpoint is conditional, @code{info break} shows the condition on
3421 the line following the affected breakpoint; breakpoint commands, if any,
3422 are listed after that. A pending breakpoint is allowed to have a condition
3423 specified for it. The condition is not parsed for validity until a shared
3424 library is loaded that allows the pending breakpoint to resolve to a
3428 @code{info break} with a breakpoint
3429 number @var{n} as argument lists only that breakpoint. The
3430 convenience variable @code{$_} and the default examining-address for
3431 the @code{x} command are set to the address of the last breakpoint
3432 listed (@pxref{Memory, ,Examining Memory}).
3435 @code{info break} displays a count of the number of times the breakpoint
3436 has been hit. This is especially useful in conjunction with the
3437 @code{ignore} command. You can ignore a large number of breakpoint
3438 hits, look at the breakpoint info to see how many times the breakpoint
3439 was hit, and then run again, ignoring one less than that number. This
3440 will get you quickly to the last hit of that breakpoint.
3443 @value{GDBN} allows you to set any number of breakpoints at the same place in
3444 your program. There is nothing silly or meaningless about this. When
3445 the breakpoints are conditional, this is even useful
3446 (@pxref{Conditions, ,Break Conditions}).
3448 @cindex multiple locations, breakpoints
3449 @cindex breakpoints, multiple locations
3450 It is possible that a breakpoint corresponds to several locations
3451 in your program. Examples of this situation are:
3455 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3456 instances of the function body, used in different cases.
3459 For a C@t{++} template function, a given line in the function can
3460 correspond to any number of instantiations.
3463 For an inlined function, a given source line can correspond to
3464 several places where that function is inlined.
3467 In all those cases, @value{GDBN} will insert a breakpoint at all
3468 the relevant locations@footnote{
3469 As of this writing, multiple-location breakpoints work only if there's
3470 line number information for all the locations. This means that they
3471 will generally not work in system libraries, unless you have debug
3472 info with line numbers for them.}.
3474 A breakpoint with multiple locations is displayed in the breakpoint
3475 table using several rows---one header row, followed by one row for
3476 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3477 address column. The rows for individual locations contain the actual
3478 addresses for locations, and show the functions to which those
3479 locations belong. The number column for a location is of the form
3480 @var{breakpoint-number}.@var{location-number}.
3485 Num Type Disp Enb Address What
3486 1 breakpoint keep y <MULTIPLE>
3488 breakpoint already hit 1 time
3489 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3490 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3493 Each location can be individually enabled or disabled by passing
3494 @var{breakpoint-number}.@var{location-number} as argument to the
3495 @code{enable} and @code{disable} commands. Note that you cannot
3496 delete the individual locations from the list, you can only delete the
3497 entire list of locations that belong to their parent breakpoint (with
3498 the @kbd{delete @var{num}} command, where @var{num} is the number of
3499 the parent breakpoint, 1 in the above example). Disabling or enabling
3500 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3501 that belong to that breakpoint.
3503 @cindex pending breakpoints
3504 It's quite common to have a breakpoint inside a shared library.
3505 Shared libraries can be loaded and unloaded explicitly,
3506 and possibly repeatedly, as the program is executed. To support
3507 this use case, @value{GDBN} updates breakpoint locations whenever
3508 any shared library is loaded or unloaded. Typically, you would
3509 set a breakpoint in a shared library at the beginning of your
3510 debugging session, when the library is not loaded, and when the
3511 symbols from the library are not available. When you try to set
3512 breakpoint, @value{GDBN} will ask you if you want to set
3513 a so called @dfn{pending breakpoint}---breakpoint whose address
3514 is not yet resolved.
3516 After the program is run, whenever a new shared library is loaded,
3517 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3518 shared library contains the symbol or line referred to by some
3519 pending breakpoint, that breakpoint is resolved and becomes an
3520 ordinary breakpoint. When a library is unloaded, all breakpoints
3521 that refer to its symbols or source lines become pending again.
3523 This logic works for breakpoints with multiple locations, too. For
3524 example, if you have a breakpoint in a C@t{++} template function, and
3525 a newly loaded shared library has an instantiation of that template,
3526 a new location is added to the list of locations for the breakpoint.
3528 Except for having unresolved address, pending breakpoints do not
3529 differ from regular breakpoints. You can set conditions or commands,
3530 enable and disable them and perform other breakpoint operations.
3532 @value{GDBN} provides some additional commands for controlling what
3533 happens when the @samp{break} command cannot resolve breakpoint
3534 address specification to an address:
3536 @kindex set breakpoint pending
3537 @kindex show breakpoint pending
3539 @item set breakpoint pending auto
3540 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3541 location, it queries you whether a pending breakpoint should be created.
3543 @item set breakpoint pending on
3544 This indicates that an unrecognized breakpoint location should automatically
3545 result in a pending breakpoint being created.
3547 @item set breakpoint pending off
3548 This indicates that pending breakpoints are not to be created. Any
3549 unrecognized breakpoint location results in an error. This setting does
3550 not affect any pending breakpoints previously created.
3552 @item show breakpoint pending
3553 Show the current behavior setting for creating pending breakpoints.
3556 The settings above only affect the @code{break} command and its
3557 variants. Once breakpoint is set, it will be automatically updated
3558 as shared libraries are loaded and unloaded.
3560 @cindex automatic hardware breakpoints
3561 For some targets, @value{GDBN} can automatically decide if hardware or
3562 software breakpoints should be used, depending on whether the
3563 breakpoint address is read-only or read-write. This applies to
3564 breakpoints set with the @code{break} command as well as to internal
3565 breakpoints set by commands like @code{next} and @code{finish}. For
3566 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3569 You can control this automatic behaviour with the following commands::
3571 @kindex set breakpoint auto-hw
3572 @kindex show breakpoint auto-hw
3574 @item set breakpoint auto-hw on
3575 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3576 will try to use the target memory map to decide if software or hardware
3577 breakpoint must be used.
3579 @item set breakpoint auto-hw off
3580 This indicates @value{GDBN} should not automatically select breakpoint
3581 type. If the target provides a memory map, @value{GDBN} will warn when
3582 trying to set software breakpoint at a read-only address.
3585 @value{GDBN} normally implements breakpoints by replacing the program code
3586 at the breakpoint address with a special instruction, which, when
3587 executed, given control to the debugger. By default, the program
3588 code is so modified only when the program is resumed. As soon as
3589 the program stops, @value{GDBN} restores the original instructions. This
3590 behaviour guards against leaving breakpoints inserted in the
3591 target should gdb abrubptly disconnect. However, with slow remote
3592 targets, inserting and removing breakpoint can reduce the performance.
3593 This behavior can be controlled with the following commands::
3595 @kindex set breakpoint always-inserted
3596 @kindex show breakpoint always-inserted
3598 @item set breakpoint always-inserted off
3599 All breakpoints, including newly added by the user, are inserted in
3600 the target only when the target is resumed. All breakpoints are
3601 removed from the target when it stops.
3603 @item set breakpoint always-inserted on
3604 Causes all breakpoints to be inserted in the target at all times. If
3605 the user adds a new breakpoint, or changes an existing breakpoint, the
3606 breakpoints in the target are updated immediately. A breakpoint is
3607 removed from the target only when breakpoint itself is removed.
3609 @cindex non-stop mode, and @code{breakpoint always-inserted}
3610 @item set breakpoint always-inserted auto
3611 This is the default mode. If @value{GDBN} is controlling the inferior
3612 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3613 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3614 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3615 @code{breakpoint always-inserted} mode is off.
3618 @cindex negative breakpoint numbers
3619 @cindex internal @value{GDBN} breakpoints
3620 @value{GDBN} itself sometimes sets breakpoints in your program for
3621 special purposes, such as proper handling of @code{longjmp} (in C
3622 programs). These internal breakpoints are assigned negative numbers,
3623 starting with @code{-1}; @samp{info breakpoints} does not display them.
3624 You can see these breakpoints with the @value{GDBN} maintenance command
3625 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3628 @node Set Watchpoints
3629 @subsection Setting Watchpoints
3631 @cindex setting watchpoints
3632 You can use a watchpoint to stop execution whenever the value of an
3633 expression changes, without having to predict a particular place where
3634 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3635 The expression may be as simple as the value of a single variable, or
3636 as complex as many variables combined by operators. Examples include:
3640 A reference to the value of a single variable.
3643 An address cast to an appropriate data type. For example,
3644 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3645 address (assuming an @code{int} occupies 4 bytes).
3648 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3649 expression can use any operators valid in the program's native
3650 language (@pxref{Languages}).
3653 You can set a watchpoint on an expression even if the expression can
3654 not be evaluated yet. For instance, you can set a watchpoint on
3655 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3656 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3657 the expression produces a valid value. If the expression becomes
3658 valid in some other way than changing a variable (e.g.@: if the memory
3659 pointed to by @samp{*global_ptr} becomes readable as the result of a
3660 @code{malloc} call), @value{GDBN} may not stop until the next time
3661 the expression changes.
3663 @cindex software watchpoints
3664 @cindex hardware watchpoints
3665 Depending on your system, watchpoints may be implemented in software or
3666 hardware. @value{GDBN} does software watchpointing by single-stepping your
3667 program and testing the variable's value each time, which is hundreds of
3668 times slower than normal execution. (But this may still be worth it, to
3669 catch errors where you have no clue what part of your program is the
3672 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3673 x86-based targets, @value{GDBN} includes support for hardware
3674 watchpoints, which do not slow down the running of your program.
3678 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3679 Set a watchpoint for an expression. @value{GDBN} will break when the
3680 expression @var{expr} is written into by the program and its value
3681 changes. The simplest (and the most popular) use of this command is
3682 to watch the value of a single variable:
3685 (@value{GDBP}) watch foo
3688 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3689 clause, @value{GDBN} breaks only when the thread identified by
3690 @var{threadnum} changes the value of @var{expr}. If any other threads
3691 change the value of @var{expr}, @value{GDBN} will not break. Note
3692 that watchpoints restricted to a single thread in this way only work
3693 with Hardware Watchpoints.
3696 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3697 Set a watchpoint that will break when the value of @var{expr} is read
3701 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3702 Set a watchpoint that will break when @var{expr} is either read from
3703 or written into by the program.
3705 @kindex info watchpoints @r{[}@var{n}@r{]}
3706 @item info watchpoints
3707 This command prints a list of watchpoints, using the same format as
3708 @code{info break} (@pxref{Set Breaks}).
3711 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3712 watchpoints execute very quickly, and the debugger reports a change in
3713 value at the exact instruction where the change occurs. If @value{GDBN}
3714 cannot set a hardware watchpoint, it sets a software watchpoint, which
3715 executes more slowly and reports the change in value at the next
3716 @emph{statement}, not the instruction, after the change occurs.
3718 @cindex use only software watchpoints
3719 You can force @value{GDBN} to use only software watchpoints with the
3720 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3721 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3722 the underlying system supports them. (Note that hardware-assisted
3723 watchpoints that were set @emph{before} setting
3724 @code{can-use-hw-watchpoints} to zero will still use the hardware
3725 mechanism of watching expression values.)
3728 @item set can-use-hw-watchpoints
3729 @kindex set can-use-hw-watchpoints
3730 Set whether or not to use hardware watchpoints.
3732 @item show can-use-hw-watchpoints
3733 @kindex show can-use-hw-watchpoints
3734 Show the current mode of using hardware watchpoints.
3737 For remote targets, you can restrict the number of hardware
3738 watchpoints @value{GDBN} will use, see @ref{set remote
3739 hardware-breakpoint-limit}.
3741 When you issue the @code{watch} command, @value{GDBN} reports
3744 Hardware watchpoint @var{num}: @var{expr}
3748 if it was able to set a hardware watchpoint.
3750 Currently, the @code{awatch} and @code{rwatch} commands can only set
3751 hardware watchpoints, because accesses to data that don't change the
3752 value of the watched expression cannot be detected without examining
3753 every instruction as it is being executed, and @value{GDBN} does not do
3754 that currently. If @value{GDBN} finds that it is unable to set a
3755 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3756 will print a message like this:
3759 Expression cannot be implemented with read/access watchpoint.
3762 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3763 data type of the watched expression is wider than what a hardware
3764 watchpoint on the target machine can handle. For example, some systems
3765 can only watch regions that are up to 4 bytes wide; on such systems you
3766 cannot set hardware watchpoints for an expression that yields a
3767 double-precision floating-point number (which is typically 8 bytes
3768 wide). As a work-around, it might be possible to break the large region
3769 into a series of smaller ones and watch them with separate watchpoints.
3771 If you set too many hardware watchpoints, @value{GDBN} might be unable
3772 to insert all of them when you resume the execution of your program.
3773 Since the precise number of active watchpoints is unknown until such
3774 time as the program is about to be resumed, @value{GDBN} might not be
3775 able to warn you about this when you set the watchpoints, and the
3776 warning will be printed only when the program is resumed:
3779 Hardware watchpoint @var{num}: Could not insert watchpoint
3783 If this happens, delete or disable some of the watchpoints.
3785 Watching complex expressions that reference many variables can also
3786 exhaust the resources available for hardware-assisted watchpoints.
3787 That's because @value{GDBN} needs to watch every variable in the
3788 expression with separately allocated resources.
3790 If you call a function interactively using @code{print} or @code{call},
3791 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3792 kind of breakpoint or the call completes.
3794 @value{GDBN} automatically deletes watchpoints that watch local
3795 (automatic) variables, or expressions that involve such variables, when
3796 they go out of scope, that is, when the execution leaves the block in
3797 which these variables were defined. In particular, when the program
3798 being debugged terminates, @emph{all} local variables go out of scope,
3799 and so only watchpoints that watch global variables remain set. If you
3800 rerun the program, you will need to set all such watchpoints again. One
3801 way of doing that would be to set a code breakpoint at the entry to the
3802 @code{main} function and when it breaks, set all the watchpoints.
3804 @cindex watchpoints and threads
3805 @cindex threads and watchpoints
3806 In multi-threaded programs, watchpoints will detect changes to the
3807 watched expression from every thread.
3810 @emph{Warning:} In multi-threaded programs, software watchpoints
3811 have only limited usefulness. If @value{GDBN} creates a software
3812 watchpoint, it can only watch the value of an expression @emph{in a
3813 single thread}. If you are confident that the expression can only
3814 change due to the current thread's activity (and if you are also
3815 confident that no other thread can become current), then you can use
3816 software watchpoints as usual. However, @value{GDBN} may not notice
3817 when a non-current thread's activity changes the expression. (Hardware
3818 watchpoints, in contrast, watch an expression in all threads.)
3821 @xref{set remote hardware-watchpoint-limit}.
3823 @node Set Catchpoints
3824 @subsection Setting Catchpoints
3825 @cindex catchpoints, setting
3826 @cindex exception handlers
3827 @cindex event handling
3829 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3830 kinds of program events, such as C@t{++} exceptions or the loading of a
3831 shared library. Use the @code{catch} command to set a catchpoint.
3835 @item catch @var{event}
3836 Stop when @var{event} occurs. @var{event} can be any of the following:
3839 @cindex stop on C@t{++} exceptions
3840 The throwing of a C@t{++} exception.
3843 The catching of a C@t{++} exception.
3846 @cindex Ada exception catching
3847 @cindex catch Ada exceptions
3848 An Ada exception being raised. If an exception name is specified
3849 at the end of the command (eg @code{catch exception Program_Error}),
3850 the debugger will stop only when this specific exception is raised.
3851 Otherwise, the debugger stops execution when any Ada exception is raised.
3853 When inserting an exception catchpoint on a user-defined exception whose
3854 name is identical to one of the exceptions defined by the language, the
3855 fully qualified name must be used as the exception name. Otherwise,
3856 @value{GDBN} will assume that it should stop on the pre-defined exception
3857 rather than the user-defined one. For instance, assuming an exception
3858 called @code{Constraint_Error} is defined in package @code{Pck}, then
3859 the command to use to catch such exceptions is @kbd{catch exception
3860 Pck.Constraint_Error}.
3862 @item exception unhandled
3863 An exception that was raised but is not handled by the program.
3866 A failed Ada assertion.
3869 @cindex break on fork/exec
3870 A call to @code{exec}. This is currently only available for HP-UX
3874 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3875 @cindex break on a system call.
3876 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3877 syscall is a mechanism for application programs to request a service
3878 from the operating system (OS) or one of the OS system services.
3879 @value{GDBN} can catch some or all of the syscalls issued by the
3880 debuggee, and show the related information for each syscall. If no
3881 argument is specified, calls to and returns from all system calls
3884 @var{name} can be any system call name that is valid for the
3885 underlying OS. Just what syscalls are valid depends on the OS. On
3886 GNU and Unix systems, you can find the full list of valid syscall
3887 names on @file{/usr/include/asm/unistd.h}.
3889 @c For MS-Windows, the syscall names and the corresponding numbers
3890 @c can be found, e.g., on this URL:
3891 @c http://www.metasploit.com/users/opcode/syscalls.html
3892 @c but we don't support Windows syscalls yet.
3894 Normally, @value{GDBN} knows in advance which syscalls are valid for
3895 each OS, so you can use the @value{GDBN} command-line completion
3896 facilities (@pxref{Completion,, command completion}) to list the
3899 You may also specify the system call numerically. A syscall's
3900 number is the value passed to the OS's syscall dispatcher to
3901 identify the requested service. When you specify the syscall by its
3902 name, @value{GDBN} uses its database of syscalls to convert the name
3903 into the corresponding numeric code, but using the number directly
3904 may be useful if @value{GDBN}'s database does not have the complete
3905 list of syscalls on your system (e.g., because @value{GDBN} lags
3906 behind the OS upgrades).
3908 The example below illustrates how this command works if you don't provide
3912 (@value{GDBP}) catch syscall
3913 Catchpoint 1 (syscall)
3915 Starting program: /tmp/catch-syscall
3917 Catchpoint 1 (call to syscall 'close'), \
3918 0xffffe424 in __kernel_vsyscall ()
3922 Catchpoint 1 (returned from syscall 'close'), \
3923 0xffffe424 in __kernel_vsyscall ()
3927 Here is an example of catching a system call by name:
3930 (@value{GDBP}) catch syscall chroot
3931 Catchpoint 1 (syscall 'chroot' [61])
3933 Starting program: /tmp/catch-syscall
3935 Catchpoint 1 (call to syscall 'chroot'), \
3936 0xffffe424 in __kernel_vsyscall ()
3940 Catchpoint 1 (returned from syscall 'chroot'), \
3941 0xffffe424 in __kernel_vsyscall ()
3945 An example of specifying a system call numerically. In the case
3946 below, the syscall number has a corresponding entry in the XML
3947 file, so @value{GDBN} finds its name and prints it:
3950 (@value{GDBP}) catch syscall 252
3951 Catchpoint 1 (syscall(s) 'exit_group')
3953 Starting program: /tmp/catch-syscall
3955 Catchpoint 1 (call to syscall 'exit_group'), \
3956 0xffffe424 in __kernel_vsyscall ()
3960 Program exited normally.
3964 However, there can be situations when there is no corresponding name
3965 in XML file for that syscall number. In this case, @value{GDBN} prints
3966 a warning message saying that it was not able to find the syscall name,
3967 but the catchpoint will be set anyway. See the example below:
3970 (@value{GDBP}) catch syscall 764
3971 warning: The number '764' does not represent a known syscall.
3972 Catchpoint 2 (syscall 764)
3976 If you configure @value{GDBN} using the @samp{--without-expat} option,
3977 it will not be able to display syscall names. Also, if your
3978 architecture does not have an XML file describing its system calls,
3979 you will not be able to see the syscall names. It is important to
3980 notice that these two features are used for accessing the syscall
3981 name database. In either case, you will see a warning like this:
3984 (@value{GDBP}) catch syscall
3985 warning: Could not open "syscalls/i386-linux.xml"
3986 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
3987 GDB will not be able to display syscall names.
3988 Catchpoint 1 (syscall)
3992 Of course, the file name will change depending on your architecture and system.
3994 Still using the example above, you can also try to catch a syscall by its
3995 number. In this case, you would see something like:
3998 (@value{GDBP}) catch syscall 252
3999 Catchpoint 1 (syscall(s) 252)
4002 Again, in this case @value{GDBN} would not be able to display syscall's names.
4005 A call to @code{fork}. This is currently only available for HP-UX
4009 A call to @code{vfork}. This is currently only available for HP-UX
4014 @item tcatch @var{event}
4015 Set a catchpoint that is enabled only for one stop. The catchpoint is
4016 automatically deleted after the first time the event is caught.
4020 Use the @code{info break} command to list the current catchpoints.
4022 There are currently some limitations to C@t{++} exception handling
4023 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4027 If you call a function interactively, @value{GDBN} normally returns
4028 control to you when the function has finished executing. If the call
4029 raises an exception, however, the call may bypass the mechanism that
4030 returns control to you and cause your program either to abort or to
4031 simply continue running until it hits a breakpoint, catches a signal
4032 that @value{GDBN} is listening for, or exits. This is the case even if
4033 you set a catchpoint for the exception; catchpoints on exceptions are
4034 disabled within interactive calls.
4037 You cannot raise an exception interactively.
4040 You cannot install an exception handler interactively.
4043 @cindex raise exceptions
4044 Sometimes @code{catch} is not the best way to debug exception handling:
4045 if you need to know exactly where an exception is raised, it is better to
4046 stop @emph{before} the exception handler is called, since that way you
4047 can see the stack before any unwinding takes place. If you set a
4048 breakpoint in an exception handler instead, it may not be easy to find
4049 out where the exception was raised.
4051 To stop just before an exception handler is called, you need some
4052 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4053 raised by calling a library function named @code{__raise_exception}
4054 which has the following ANSI C interface:
4057 /* @var{addr} is where the exception identifier is stored.
4058 @var{id} is the exception identifier. */
4059 void __raise_exception (void **addr, void *id);
4063 To make the debugger catch all exceptions before any stack
4064 unwinding takes place, set a breakpoint on @code{__raise_exception}
4065 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4067 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4068 that depends on the value of @var{id}, you can stop your program when
4069 a specific exception is raised. You can use multiple conditional
4070 breakpoints to stop your program when any of a number of exceptions are
4075 @subsection Deleting Breakpoints
4077 @cindex clearing breakpoints, watchpoints, catchpoints
4078 @cindex deleting breakpoints, watchpoints, catchpoints
4079 It is often necessary to eliminate a breakpoint, watchpoint, or
4080 catchpoint once it has done its job and you no longer want your program
4081 to stop there. This is called @dfn{deleting} the breakpoint. A
4082 breakpoint that has been deleted no longer exists; it is forgotten.
4084 With the @code{clear} command you can delete breakpoints according to
4085 where they are in your program. With the @code{delete} command you can
4086 delete individual breakpoints, watchpoints, or catchpoints by specifying
4087 their breakpoint numbers.
4089 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4090 automatically ignores breakpoints on the first instruction to be executed
4091 when you continue execution without changing the execution address.
4096 Delete any breakpoints at the next instruction to be executed in the
4097 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4098 the innermost frame is selected, this is a good way to delete a
4099 breakpoint where your program just stopped.
4101 @item clear @var{location}
4102 Delete any breakpoints set at the specified @var{location}.
4103 @xref{Specify Location}, for the various forms of @var{location}; the
4104 most useful ones are listed below:
4107 @item clear @var{function}
4108 @itemx clear @var{filename}:@var{function}
4109 Delete any breakpoints set at entry to the named @var{function}.
4111 @item clear @var{linenum}
4112 @itemx clear @var{filename}:@var{linenum}
4113 Delete any breakpoints set at or within the code of the specified
4114 @var{linenum} of the specified @var{filename}.
4117 @cindex delete breakpoints
4119 @kindex d @r{(@code{delete})}
4120 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4121 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4122 ranges specified as arguments. If no argument is specified, delete all
4123 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4124 confirm off}). You can abbreviate this command as @code{d}.
4128 @subsection Disabling Breakpoints
4130 @cindex enable/disable a breakpoint
4131 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4132 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4133 it had been deleted, but remembers the information on the breakpoint so
4134 that you can @dfn{enable} it again later.
4136 You disable and enable breakpoints, watchpoints, and catchpoints with
4137 the @code{enable} and @code{disable} commands, optionally specifying
4138 one or more breakpoint numbers as arguments. Use @code{info break} to
4139 print a list of all breakpoints, watchpoints, and catchpoints if you
4140 do not know which numbers to use.
4142 Disabling and enabling a breakpoint that has multiple locations
4143 affects all of its locations.
4145 A breakpoint, watchpoint, or catchpoint can have any of four different
4146 states of enablement:
4150 Enabled. The breakpoint stops your program. A breakpoint set
4151 with the @code{break} command starts out in this state.
4153 Disabled. The breakpoint has no effect on your program.
4155 Enabled once. The breakpoint stops your program, but then becomes
4158 Enabled for deletion. The breakpoint stops your program, but
4159 immediately after it does so it is deleted permanently. A breakpoint
4160 set with the @code{tbreak} command starts out in this state.
4163 You can use the following commands to enable or disable breakpoints,
4164 watchpoints, and catchpoints:
4168 @kindex dis @r{(@code{disable})}
4169 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4170 Disable the specified breakpoints---or all breakpoints, if none are
4171 listed. A disabled breakpoint has no effect but is not forgotten. All
4172 options such as ignore-counts, conditions and commands are remembered in
4173 case the breakpoint is enabled again later. You may abbreviate
4174 @code{disable} as @code{dis}.
4177 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4178 Enable the specified breakpoints (or all defined breakpoints). They
4179 become effective once again in stopping your program.
4181 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4182 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4183 of these breakpoints immediately after stopping your program.
4185 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4186 Enable the specified breakpoints to work once, then die. @value{GDBN}
4187 deletes any of these breakpoints as soon as your program stops there.
4188 Breakpoints set by the @code{tbreak} command start out in this state.
4191 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4192 @c confusing: tbreak is also initially enabled.
4193 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4194 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4195 subsequently, they become disabled or enabled only when you use one of
4196 the commands above. (The command @code{until} can set and delete a
4197 breakpoint of its own, but it does not change the state of your other
4198 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4202 @subsection Break Conditions
4203 @cindex conditional breakpoints
4204 @cindex breakpoint conditions
4206 @c FIXME what is scope of break condition expr? Context where wanted?
4207 @c in particular for a watchpoint?
4208 The simplest sort of breakpoint breaks every time your program reaches a
4209 specified place. You can also specify a @dfn{condition} for a
4210 breakpoint. A condition is just a Boolean expression in your
4211 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4212 a condition evaluates the expression each time your program reaches it,
4213 and your program stops only if the condition is @emph{true}.
4215 This is the converse of using assertions for program validation; in that
4216 situation, you want to stop when the assertion is violated---that is,
4217 when the condition is false. In C, if you want to test an assertion expressed
4218 by the condition @var{assert}, you should set the condition
4219 @samp{! @var{assert}} on the appropriate breakpoint.
4221 Conditions are also accepted for watchpoints; you may not need them,
4222 since a watchpoint is inspecting the value of an expression anyhow---but
4223 it might be simpler, say, to just set a watchpoint on a variable name,
4224 and specify a condition that tests whether the new value is an interesting
4227 Break conditions can have side effects, and may even call functions in
4228 your program. This can be useful, for example, to activate functions
4229 that log program progress, or to use your own print functions to
4230 format special data structures. The effects are completely predictable
4231 unless there is another enabled breakpoint at the same address. (In
4232 that case, @value{GDBN} might see the other breakpoint first and stop your
4233 program without checking the condition of this one.) Note that
4234 breakpoint commands are usually more convenient and flexible than break
4236 purpose of performing side effects when a breakpoint is reached
4237 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4239 Break conditions can be specified when a breakpoint is set, by using
4240 @samp{if} in the arguments to the @code{break} command. @xref{Set
4241 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4242 with the @code{condition} command.
4244 You can also use the @code{if} keyword with the @code{watch} command.
4245 The @code{catch} command does not recognize the @code{if} keyword;
4246 @code{condition} is the only way to impose a further condition on a
4251 @item condition @var{bnum} @var{expression}
4252 Specify @var{expression} as the break condition for breakpoint,
4253 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4254 breakpoint @var{bnum} stops your program only if the value of
4255 @var{expression} is true (nonzero, in C). When you use
4256 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4257 syntactic correctness, and to determine whether symbols in it have
4258 referents in the context of your breakpoint. If @var{expression} uses
4259 symbols not referenced in the context of the breakpoint, @value{GDBN}
4260 prints an error message:
4263 No symbol "foo" in current context.
4268 not actually evaluate @var{expression} at the time the @code{condition}
4269 command (or a command that sets a breakpoint with a condition, like
4270 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4272 @item condition @var{bnum}
4273 Remove the condition from breakpoint number @var{bnum}. It becomes
4274 an ordinary unconditional breakpoint.
4277 @cindex ignore count (of breakpoint)
4278 A special case of a breakpoint condition is to stop only when the
4279 breakpoint has been reached a certain number of times. This is so
4280 useful that there is a special way to do it, using the @dfn{ignore
4281 count} of the breakpoint. Every breakpoint has an ignore count, which
4282 is an integer. Most of the time, the ignore count is zero, and
4283 therefore has no effect. But if your program reaches a breakpoint whose
4284 ignore count is positive, then instead of stopping, it just decrements
4285 the ignore count by one and continues. As a result, if the ignore count
4286 value is @var{n}, the breakpoint does not stop the next @var{n} times
4287 your program reaches it.
4291 @item ignore @var{bnum} @var{count}
4292 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4293 The next @var{count} times the breakpoint is reached, your program's
4294 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4297 To make the breakpoint stop the next time it is reached, specify
4300 When you use @code{continue} to resume execution of your program from a
4301 breakpoint, you can specify an ignore count directly as an argument to
4302 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4303 Stepping,,Continuing and Stepping}.
4305 If a breakpoint has a positive ignore count and a condition, the
4306 condition is not checked. Once the ignore count reaches zero,
4307 @value{GDBN} resumes checking the condition.
4309 You could achieve the effect of the ignore count with a condition such
4310 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4311 is decremented each time. @xref{Convenience Vars, ,Convenience
4315 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4318 @node Break Commands
4319 @subsection Breakpoint Command Lists
4321 @cindex breakpoint commands
4322 You can give any breakpoint (or watchpoint or catchpoint) a series of
4323 commands to execute when your program stops due to that breakpoint. For
4324 example, you might want to print the values of certain expressions, or
4325 enable other breakpoints.
4329 @kindex end@r{ (breakpoint commands)}
4330 @item commands @r{[}@var{range}@dots{}@r{]}
4331 @itemx @dots{} @var{command-list} @dots{}
4333 Specify a list of commands for the given breakpoints. The commands
4334 themselves appear on the following lines. Type a line containing just
4335 @code{end} to terminate the commands.
4337 To remove all commands from a breakpoint, type @code{commands} and
4338 follow it immediately with @code{end}; that is, give no commands.
4340 With no argument, @code{commands} refers to the last breakpoint,
4341 watchpoint, or catchpoint set (not to the breakpoint most recently
4342 encountered). If the most recent breakpoints were set with a single
4343 command, then the @code{commands} will apply to all the breakpoints
4344 set by that command. This applies to breakpoints set by
4345 @code{rbreak}, and also applies when a single @code{break} command
4346 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4350 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4351 disabled within a @var{command-list}.
4353 You can use breakpoint commands to start your program up again. Simply
4354 use the @code{continue} command, or @code{step}, or any other command
4355 that resumes execution.
4357 Any other commands in the command list, after a command that resumes
4358 execution, are ignored. This is because any time you resume execution
4359 (even with a simple @code{next} or @code{step}), you may encounter
4360 another breakpoint---which could have its own command list, leading to
4361 ambiguities about which list to execute.
4364 If the first command you specify in a command list is @code{silent}, the
4365 usual message about stopping at a breakpoint is not printed. This may
4366 be desirable for breakpoints that are to print a specific message and
4367 then continue. If none of the remaining commands print anything, you
4368 see no sign that the breakpoint was reached. @code{silent} is
4369 meaningful only at the beginning of a breakpoint command list.
4371 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4372 print precisely controlled output, and are often useful in silent
4373 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4375 For example, here is how you could use breakpoint commands to print the
4376 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4382 printf "x is %d\n",x
4387 One application for breakpoint commands is to compensate for one bug so
4388 you can test for another. Put a breakpoint just after the erroneous line
4389 of code, give it a condition to detect the case in which something
4390 erroneous has been done, and give it commands to assign correct values
4391 to any variables that need them. End with the @code{continue} command
4392 so that your program does not stop, and start with the @code{silent}
4393 command so that no output is produced. Here is an example:
4404 @c @ifclear BARETARGET
4405 @node Error in Breakpoints
4406 @subsection ``Cannot insert breakpoints''
4408 If you request too many active hardware-assisted breakpoints and
4409 watchpoints, you will see this error message:
4411 @c FIXME: the precise wording of this message may change; the relevant
4412 @c source change is not committed yet (Sep 3, 1999).
4414 Stopped; cannot insert breakpoints.
4415 You may have requested too many hardware breakpoints and watchpoints.
4419 This message is printed when you attempt to resume the program, since
4420 only then @value{GDBN} knows exactly how many hardware breakpoints and
4421 watchpoints it needs to insert.
4423 When this message is printed, you need to disable or remove some of the
4424 hardware-assisted breakpoints and watchpoints, and then continue.
4426 @node Breakpoint-related Warnings
4427 @subsection ``Breakpoint address adjusted...''
4428 @cindex breakpoint address adjusted
4430 Some processor architectures place constraints on the addresses at
4431 which breakpoints may be placed. For architectures thus constrained,
4432 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4433 with the constraints dictated by the architecture.
4435 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4436 a VLIW architecture in which a number of RISC-like instructions may be
4437 bundled together for parallel execution. The FR-V architecture
4438 constrains the location of a breakpoint instruction within such a
4439 bundle to the instruction with the lowest address. @value{GDBN}
4440 honors this constraint by adjusting a breakpoint's address to the
4441 first in the bundle.
4443 It is not uncommon for optimized code to have bundles which contain
4444 instructions from different source statements, thus it may happen that
4445 a breakpoint's address will be adjusted from one source statement to
4446 another. Since this adjustment may significantly alter @value{GDBN}'s
4447 breakpoint related behavior from what the user expects, a warning is
4448 printed when the breakpoint is first set and also when the breakpoint
4451 A warning like the one below is printed when setting a breakpoint
4452 that's been subject to address adjustment:
4455 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4458 Such warnings are printed both for user settable and @value{GDBN}'s
4459 internal breakpoints. If you see one of these warnings, you should
4460 verify that a breakpoint set at the adjusted address will have the
4461 desired affect. If not, the breakpoint in question may be removed and
4462 other breakpoints may be set which will have the desired behavior.
4463 E.g., it may be sufficient to place the breakpoint at a later
4464 instruction. A conditional breakpoint may also be useful in some
4465 cases to prevent the breakpoint from triggering too often.
4467 @value{GDBN} will also issue a warning when stopping at one of these
4468 adjusted breakpoints:
4471 warning: Breakpoint 1 address previously adjusted from 0x00010414
4475 When this warning is encountered, it may be too late to take remedial
4476 action except in cases where the breakpoint is hit earlier or more
4477 frequently than expected.
4479 @node Continuing and Stepping
4480 @section Continuing and Stepping
4484 @cindex resuming execution
4485 @dfn{Continuing} means resuming program execution until your program
4486 completes normally. In contrast, @dfn{stepping} means executing just
4487 one more ``step'' of your program, where ``step'' may mean either one
4488 line of source code, or one machine instruction (depending on what
4489 particular command you use). Either when continuing or when stepping,
4490 your program may stop even sooner, due to a breakpoint or a signal. (If
4491 it stops due to a signal, you may want to use @code{handle}, or use
4492 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4496 @kindex c @r{(@code{continue})}
4497 @kindex fg @r{(resume foreground execution)}
4498 @item continue @r{[}@var{ignore-count}@r{]}
4499 @itemx c @r{[}@var{ignore-count}@r{]}
4500 @itemx fg @r{[}@var{ignore-count}@r{]}
4501 Resume program execution, at the address where your program last stopped;
4502 any breakpoints set at that address are bypassed. The optional argument
4503 @var{ignore-count} allows you to specify a further number of times to
4504 ignore a breakpoint at this location; its effect is like that of
4505 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4507 The argument @var{ignore-count} is meaningful only when your program
4508 stopped due to a breakpoint. At other times, the argument to
4509 @code{continue} is ignored.
4511 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4512 debugged program is deemed to be the foreground program) are provided
4513 purely for convenience, and have exactly the same behavior as
4517 To resume execution at a different place, you can use @code{return}
4518 (@pxref{Returning, ,Returning from a Function}) to go back to the
4519 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4520 Different Address}) to go to an arbitrary location in your program.
4522 A typical technique for using stepping is to set a breakpoint
4523 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4524 beginning of the function or the section of your program where a problem
4525 is believed to lie, run your program until it stops at that breakpoint,
4526 and then step through the suspect area, examining the variables that are
4527 interesting, until you see the problem happen.
4531 @kindex s @r{(@code{step})}
4533 Continue running your program until control reaches a different source
4534 line, then stop it and return control to @value{GDBN}. This command is
4535 abbreviated @code{s}.
4538 @c "without debugging information" is imprecise; actually "without line
4539 @c numbers in the debugging information". (gcc -g1 has debugging info but
4540 @c not line numbers). But it seems complex to try to make that
4541 @c distinction here.
4542 @emph{Warning:} If you use the @code{step} command while control is
4543 within a function that was compiled without debugging information,
4544 execution proceeds until control reaches a function that does have
4545 debugging information. Likewise, it will not step into a function which
4546 is compiled without debugging information. To step through functions
4547 without debugging information, use the @code{stepi} command, described
4551 The @code{step} command only stops at the first instruction of a source
4552 line. This prevents the multiple stops that could otherwise occur in
4553 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4554 to stop if a function that has debugging information is called within
4555 the line. In other words, @code{step} @emph{steps inside} any functions
4556 called within the line.
4558 Also, the @code{step} command only enters a function if there is line
4559 number information for the function. Otherwise it acts like the
4560 @code{next} command. This avoids problems when using @code{cc -gl}
4561 on MIPS machines. Previously, @code{step} entered subroutines if there
4562 was any debugging information about the routine.
4564 @item step @var{count}
4565 Continue running as in @code{step}, but do so @var{count} times. If a
4566 breakpoint is reached, or a signal not related to stepping occurs before
4567 @var{count} steps, stepping stops right away.
4570 @kindex n @r{(@code{next})}
4571 @item next @r{[}@var{count}@r{]}
4572 Continue to the next source line in the current (innermost) stack frame.
4573 This is similar to @code{step}, but function calls that appear within
4574 the line of code are executed without stopping. Execution stops when
4575 control reaches a different line of code at the original stack level
4576 that was executing when you gave the @code{next} command. This command
4577 is abbreviated @code{n}.
4579 An argument @var{count} is a repeat count, as for @code{step}.
4582 @c FIX ME!! Do we delete this, or is there a way it fits in with
4583 @c the following paragraph? --- Vctoria
4585 @c @code{next} within a function that lacks debugging information acts like
4586 @c @code{step}, but any function calls appearing within the code of the
4587 @c function are executed without stopping.
4589 The @code{next} command only stops at the first instruction of a
4590 source line. This prevents multiple stops that could otherwise occur in
4591 @code{switch} statements, @code{for} loops, etc.
4593 @kindex set step-mode
4595 @cindex functions without line info, and stepping
4596 @cindex stepping into functions with no line info
4597 @itemx set step-mode on
4598 The @code{set step-mode on} command causes the @code{step} command to
4599 stop at the first instruction of a function which contains no debug line
4600 information rather than stepping over it.
4602 This is useful in cases where you may be interested in inspecting the
4603 machine instructions of a function which has no symbolic info and do not
4604 want @value{GDBN} to automatically skip over this function.
4606 @item set step-mode off
4607 Causes the @code{step} command to step over any functions which contains no
4608 debug information. This is the default.
4610 @item show step-mode
4611 Show whether @value{GDBN} will stop in or step over functions without
4612 source line debug information.
4615 @kindex fin @r{(@code{finish})}
4617 Continue running until just after function in the selected stack frame
4618 returns. Print the returned value (if any). This command can be
4619 abbreviated as @code{fin}.
4621 Contrast this with the @code{return} command (@pxref{Returning,
4622 ,Returning from a Function}).
4625 @kindex u @r{(@code{until})}
4626 @cindex run until specified location
4629 Continue running until a source line past the current line, in the
4630 current stack frame, is reached. This command is used to avoid single
4631 stepping through a loop more than once. It is like the @code{next}
4632 command, except that when @code{until} encounters a jump, it
4633 automatically continues execution until the program counter is greater
4634 than the address of the jump.
4636 This means that when you reach the end of a loop after single stepping
4637 though it, @code{until} makes your program continue execution until it
4638 exits the loop. In contrast, a @code{next} command at the end of a loop
4639 simply steps back to the beginning of the loop, which forces you to step
4640 through the next iteration.
4642 @code{until} always stops your program if it attempts to exit the current
4645 @code{until} may produce somewhat counterintuitive results if the order
4646 of machine code does not match the order of the source lines. For
4647 example, in the following excerpt from a debugging session, the @code{f}
4648 (@code{frame}) command shows that execution is stopped at line
4649 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4653 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4655 (@value{GDBP}) until
4656 195 for ( ; argc > 0; NEXTARG) @{
4659 This happened because, for execution efficiency, the compiler had
4660 generated code for the loop closure test at the end, rather than the
4661 start, of the loop---even though the test in a C @code{for}-loop is
4662 written before the body of the loop. The @code{until} command appeared
4663 to step back to the beginning of the loop when it advanced to this
4664 expression; however, it has not really gone to an earlier
4665 statement---not in terms of the actual machine code.
4667 @code{until} with no argument works by means of single
4668 instruction stepping, and hence is slower than @code{until} with an
4671 @item until @var{location}
4672 @itemx u @var{location}
4673 Continue running your program until either the specified location is
4674 reached, or the current stack frame returns. @var{location} is any of
4675 the forms described in @ref{Specify Location}.
4676 This form of the command uses temporary breakpoints, and
4677 hence is quicker than @code{until} without an argument. The specified
4678 location is actually reached only if it is in the current frame. This
4679 implies that @code{until} can be used to skip over recursive function
4680 invocations. For instance in the code below, if the current location is
4681 line @code{96}, issuing @code{until 99} will execute the program up to
4682 line @code{99} in the same invocation of factorial, i.e., after the inner
4683 invocations have returned.
4686 94 int factorial (int value)
4688 96 if (value > 1) @{
4689 97 value *= factorial (value - 1);
4696 @kindex advance @var{location}
4697 @itemx advance @var{location}
4698 Continue running the program up to the given @var{location}. An argument is
4699 required, which should be of one of the forms described in
4700 @ref{Specify Location}.
4701 Execution will also stop upon exit from the current stack
4702 frame. This command is similar to @code{until}, but @code{advance} will
4703 not skip over recursive function calls, and the target location doesn't
4704 have to be in the same frame as the current one.
4708 @kindex si @r{(@code{stepi})}
4710 @itemx stepi @var{arg}
4712 Execute one machine instruction, then stop and return to the debugger.
4714 It is often useful to do @samp{display/i $pc} when stepping by machine
4715 instructions. This makes @value{GDBN} automatically display the next
4716 instruction to be executed, each time your program stops. @xref{Auto
4717 Display,, Automatic Display}.
4719 An argument is a repeat count, as in @code{step}.
4723 @kindex ni @r{(@code{nexti})}
4725 @itemx nexti @var{arg}
4727 Execute one machine instruction, but if it is a function call,
4728 proceed until the function returns.
4730 An argument is a repeat count, as in @code{next}.
4737 A signal is an asynchronous event that can happen in a program. The
4738 operating system defines the possible kinds of signals, and gives each
4739 kind a name and a number. For example, in Unix @code{SIGINT} is the
4740 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4741 @code{SIGSEGV} is the signal a program gets from referencing a place in
4742 memory far away from all the areas in use; @code{SIGALRM} occurs when
4743 the alarm clock timer goes off (which happens only if your program has
4744 requested an alarm).
4746 @cindex fatal signals
4747 Some signals, including @code{SIGALRM}, are a normal part of the
4748 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4749 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4750 program has not specified in advance some other way to handle the signal.
4751 @code{SIGINT} does not indicate an error in your program, but it is normally
4752 fatal so it can carry out the purpose of the interrupt: to kill the program.
4754 @value{GDBN} has the ability to detect any occurrence of a signal in your
4755 program. You can tell @value{GDBN} in advance what to do for each kind of
4758 @cindex handling signals
4759 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4760 @code{SIGALRM} be silently passed to your program
4761 (so as not to interfere with their role in the program's functioning)
4762 but to stop your program immediately whenever an error signal happens.
4763 You can change these settings with the @code{handle} command.
4766 @kindex info signals
4770 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4771 handle each one. You can use this to see the signal numbers of all
4772 the defined types of signals.
4774 @item info signals @var{sig}
4775 Similar, but print information only about the specified signal number.
4777 @code{info handle} is an alias for @code{info signals}.
4780 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4781 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4782 can be the number of a signal or its name (with or without the
4783 @samp{SIG} at the beginning); a list of signal numbers of the form
4784 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4785 known signals. Optional arguments @var{keywords}, described below,
4786 say what change to make.
4790 The keywords allowed by the @code{handle} command can be abbreviated.
4791 Their full names are:
4795 @value{GDBN} should not stop your program when this signal happens. It may
4796 still print a message telling you that the signal has come in.
4799 @value{GDBN} should stop your program when this signal happens. This implies
4800 the @code{print} keyword as well.
4803 @value{GDBN} should print a message when this signal happens.
4806 @value{GDBN} should not mention the occurrence of the signal at all. This
4807 implies the @code{nostop} keyword as well.
4811 @value{GDBN} should allow your program to see this signal; your program
4812 can handle the signal, or else it may terminate if the signal is fatal
4813 and not handled. @code{pass} and @code{noignore} are synonyms.
4817 @value{GDBN} should not allow your program to see this signal.
4818 @code{nopass} and @code{ignore} are synonyms.
4822 When a signal stops your program, the signal is not visible to the
4824 continue. Your program sees the signal then, if @code{pass} is in
4825 effect for the signal in question @emph{at that time}. In other words,
4826 after @value{GDBN} reports a signal, you can use the @code{handle}
4827 command with @code{pass} or @code{nopass} to control whether your
4828 program sees that signal when you continue.
4830 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4831 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4832 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4835 You can also use the @code{signal} command to prevent your program from
4836 seeing a signal, or cause it to see a signal it normally would not see,
4837 or to give it any signal at any time. For example, if your program stopped
4838 due to some sort of memory reference error, you might store correct
4839 values into the erroneous variables and continue, hoping to see more
4840 execution; but your program would probably terminate immediately as
4841 a result of the fatal signal once it saw the signal. To prevent this,
4842 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4845 @cindex extra signal information
4846 @anchor{extra signal information}
4848 On some targets, @value{GDBN} can inspect extra signal information
4849 associated with the intercepted signal, before it is actually
4850 delivered to the program being debugged. This information is exported
4851 by the convenience variable @code{$_siginfo}, and consists of data
4852 that is passed by the kernel to the signal handler at the time of the
4853 receipt of a signal. The data type of the information itself is
4854 target dependent. You can see the data type using the @code{ptype
4855 $_siginfo} command. On Unix systems, it typically corresponds to the
4856 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4859 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4860 referenced address that raised a segmentation fault.
4864 (@value{GDBP}) continue
4865 Program received signal SIGSEGV, Segmentation fault.
4866 0x0000000000400766 in main ()
4868 (@value{GDBP}) ptype $_siginfo
4875 struct @{...@} _kill;
4876 struct @{...@} _timer;
4878 struct @{...@} _sigchld;
4879 struct @{...@} _sigfault;
4880 struct @{...@} _sigpoll;
4883 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4887 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4888 $1 = (void *) 0x7ffff7ff7000
4892 Depending on target support, @code{$_siginfo} may also be writable.
4895 @section Stopping and Starting Multi-thread Programs
4897 @cindex stopped threads
4898 @cindex threads, stopped
4900 @cindex continuing threads
4901 @cindex threads, continuing
4903 @value{GDBN} supports debugging programs with multiple threads
4904 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4905 are two modes of controlling execution of your program within the
4906 debugger. In the default mode, referred to as @dfn{all-stop mode},
4907 when any thread in your program stops (for example, at a breakpoint
4908 or while being stepped), all other threads in the program are also stopped by
4909 @value{GDBN}. On some targets, @value{GDBN} also supports
4910 @dfn{non-stop mode}, in which other threads can continue to run freely while
4911 you examine the stopped thread in the debugger.
4914 * All-Stop Mode:: All threads stop when GDB takes control
4915 * Non-Stop Mode:: Other threads continue to execute
4916 * Background Execution:: Running your program asynchronously
4917 * Thread-Specific Breakpoints:: Controlling breakpoints
4918 * Interrupted System Calls:: GDB may interfere with system calls
4922 @subsection All-Stop Mode
4924 @cindex all-stop mode
4926 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4927 @emph{all} threads of execution stop, not just the current thread. This
4928 allows you to examine the overall state of the program, including
4929 switching between threads, without worrying that things may change
4932 Conversely, whenever you restart the program, @emph{all} threads start
4933 executing. @emph{This is true even when single-stepping} with commands
4934 like @code{step} or @code{next}.
4936 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4937 Since thread scheduling is up to your debugging target's operating
4938 system (not controlled by @value{GDBN}), other threads may
4939 execute more than one statement while the current thread completes a
4940 single step. Moreover, in general other threads stop in the middle of a
4941 statement, rather than at a clean statement boundary, when the program
4944 You might even find your program stopped in another thread after
4945 continuing or even single-stepping. This happens whenever some other
4946 thread runs into a breakpoint, a signal, or an exception before the
4947 first thread completes whatever you requested.
4949 @cindex automatic thread selection
4950 @cindex switching threads automatically
4951 @cindex threads, automatic switching
4952 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4953 signal, it automatically selects the thread where that breakpoint or
4954 signal happened. @value{GDBN} alerts you to the context switch with a
4955 message such as @samp{[Switching to Thread @var{n}]} to identify the
4958 On some OSes, you can modify @value{GDBN}'s default behavior by
4959 locking the OS scheduler to allow only a single thread to run.
4962 @item set scheduler-locking @var{mode}
4963 @cindex scheduler locking mode
4964 @cindex lock scheduler
4965 Set the scheduler locking mode. If it is @code{off}, then there is no
4966 locking and any thread may run at any time. If @code{on}, then only the
4967 current thread may run when the inferior is resumed. The @code{step}
4968 mode optimizes for single-stepping; it prevents other threads
4969 from preempting the current thread while you are stepping, so that
4970 the focus of debugging does not change unexpectedly.
4971 Other threads only rarely (or never) get a chance to run
4972 when you step. They are more likely to run when you @samp{next} over a
4973 function call, and they are completely free to run when you use commands
4974 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4975 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4976 the current thread away from the thread that you are debugging.
4978 @item show scheduler-locking
4979 Display the current scheduler locking mode.
4982 @cindex resume threads of multiple processes simultaneously
4983 By default, when you issue one of the execution commands such as
4984 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
4985 threads of the current inferior to run. For example, if @value{GDBN}
4986 is attached to two inferiors, each with two threads, the
4987 @code{continue} command resumes only the two threads of the current
4988 inferior. This is useful, for example, when you debug a program that
4989 forks and you want to hold the parent stopped (so that, for instance,
4990 it doesn't run to exit), while you debug the child. In other
4991 situations, you may not be interested in inspecting the current state
4992 of any of the processes @value{GDBN} is attached to, and you may want
4993 to resume them all until some breakpoint is hit. In the latter case,
4994 you can instruct @value{GDBN} to allow all threads of all the
4995 inferiors to run with the @w{@code{set schedule-multiple}} command.
4998 @kindex set schedule-multiple
4999 @item set schedule-multiple
5000 Set the mode for allowing threads of multiple processes to be resumed
5001 when an execution command is issued. When @code{on}, all threads of
5002 all processes are allowed to run. When @code{off}, only the threads
5003 of the current process are resumed. The default is @code{off}. The
5004 @code{scheduler-locking} mode takes precedence when set to @code{on},
5005 or while you are stepping and set to @code{step}.
5007 @item show schedule-multiple
5008 Display the current mode for resuming the execution of threads of
5013 @subsection Non-Stop Mode
5015 @cindex non-stop mode
5017 @c This section is really only a place-holder, and needs to be expanded
5018 @c with more details.
5020 For some multi-threaded targets, @value{GDBN} supports an optional
5021 mode of operation in which you can examine stopped program threads in
5022 the debugger while other threads continue to execute freely. This
5023 minimizes intrusion when debugging live systems, such as programs
5024 where some threads have real-time constraints or must continue to
5025 respond to external events. This is referred to as @dfn{non-stop} mode.
5027 In non-stop mode, when a thread stops to report a debugging event,
5028 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5029 threads as well, in contrast to the all-stop mode behavior. Additionally,
5030 execution commands such as @code{continue} and @code{step} apply by default
5031 only to the current thread in non-stop mode, rather than all threads as
5032 in all-stop mode. This allows you to control threads explicitly in
5033 ways that are not possible in all-stop mode --- for example, stepping
5034 one thread while allowing others to run freely, stepping
5035 one thread while holding all others stopped, or stepping several threads
5036 independently and simultaneously.
5038 To enter non-stop mode, use this sequence of commands before you run
5039 or attach to your program:
5042 # Enable the async interface.
5045 # If using the CLI, pagination breaks non-stop.
5048 # Finally, turn it on!
5052 You can use these commands to manipulate the non-stop mode setting:
5055 @kindex set non-stop
5056 @item set non-stop on
5057 Enable selection of non-stop mode.
5058 @item set non-stop off
5059 Disable selection of non-stop mode.
5060 @kindex show non-stop
5062 Show the current non-stop enablement setting.
5065 Note these commands only reflect whether non-stop mode is enabled,
5066 not whether the currently-executing program is being run in non-stop mode.
5067 In particular, the @code{set non-stop} preference is only consulted when
5068 @value{GDBN} starts or connects to the target program, and it is generally
5069 not possible to switch modes once debugging has started. Furthermore,
5070 since not all targets support non-stop mode, even when you have enabled
5071 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5074 In non-stop mode, all execution commands apply only to the current thread
5075 by default. That is, @code{continue} only continues one thread.
5076 To continue all threads, issue @code{continue -a} or @code{c -a}.
5078 You can use @value{GDBN}'s background execution commands
5079 (@pxref{Background Execution}) to run some threads in the background
5080 while you continue to examine or step others from @value{GDBN}.
5081 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5082 always executed asynchronously in non-stop mode.
5084 Suspending execution is done with the @code{interrupt} command when
5085 running in the background, or @kbd{Ctrl-c} during foreground execution.
5086 In all-stop mode, this stops the whole process;
5087 but in non-stop mode the interrupt applies only to the current thread.
5088 To stop the whole program, use @code{interrupt -a}.
5090 Other execution commands do not currently support the @code{-a} option.
5092 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5093 that thread current, as it does in all-stop mode. This is because the
5094 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5095 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5096 changed to a different thread just as you entered a command to operate on the
5097 previously current thread.
5099 @node Background Execution
5100 @subsection Background Execution
5102 @cindex foreground execution
5103 @cindex background execution
5104 @cindex asynchronous execution
5105 @cindex execution, foreground, background and asynchronous
5107 @value{GDBN}'s execution commands have two variants: the normal
5108 foreground (synchronous) behavior, and a background
5109 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5110 the program to report that some thread has stopped before prompting for
5111 another command. In background execution, @value{GDBN} immediately gives
5112 a command prompt so that you can issue other commands while your program runs.
5114 You need to explicitly enable asynchronous mode before you can use
5115 background execution commands. You can use these commands to
5116 manipulate the asynchronous mode setting:
5119 @kindex set target-async
5120 @item set target-async on
5121 Enable asynchronous mode.
5122 @item set target-async off
5123 Disable asynchronous mode.
5124 @kindex show target-async
5125 @item show target-async
5126 Show the current target-async setting.
5129 If the target doesn't support async mode, @value{GDBN} issues an error
5130 message if you attempt to use the background execution commands.
5132 To specify background execution, add a @code{&} to the command. For example,
5133 the background form of the @code{continue} command is @code{continue&}, or
5134 just @code{c&}. The execution commands that accept background execution
5140 @xref{Starting, , Starting your Program}.
5144 @xref{Attach, , Debugging an Already-running Process}.
5148 @xref{Continuing and Stepping, step}.
5152 @xref{Continuing and Stepping, stepi}.
5156 @xref{Continuing and Stepping, next}.
5160 @xref{Continuing and Stepping, nexti}.
5164 @xref{Continuing and Stepping, continue}.
5168 @xref{Continuing and Stepping, finish}.
5172 @xref{Continuing and Stepping, until}.
5176 Background execution is especially useful in conjunction with non-stop
5177 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5178 However, you can also use these commands in the normal all-stop mode with
5179 the restriction that you cannot issue another execution command until the
5180 previous one finishes. Examples of commands that are valid in all-stop
5181 mode while the program is running include @code{help} and @code{info break}.
5183 You can interrupt your program while it is running in the background by
5184 using the @code{interrupt} command.
5191 Suspend execution of the running program. In all-stop mode,
5192 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5193 only the current thread. To stop the whole program in non-stop mode,
5194 use @code{interrupt -a}.
5197 @node Thread-Specific Breakpoints
5198 @subsection Thread-Specific Breakpoints
5200 When your program has multiple threads (@pxref{Threads,, Debugging
5201 Programs with Multiple Threads}), you can choose whether to set
5202 breakpoints on all threads, or on a particular thread.
5205 @cindex breakpoints and threads
5206 @cindex thread breakpoints
5207 @kindex break @dots{} thread @var{threadno}
5208 @item break @var{linespec} thread @var{threadno}
5209 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5210 @var{linespec} specifies source lines; there are several ways of
5211 writing them (@pxref{Specify Location}), but the effect is always to
5212 specify some source line.
5214 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5215 to specify that you only want @value{GDBN} to stop the program when a
5216 particular thread reaches this breakpoint. @var{threadno} is one of the
5217 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5218 column of the @samp{info threads} display.
5220 If you do not specify @samp{thread @var{threadno}} when you set a
5221 breakpoint, the breakpoint applies to @emph{all} threads of your
5224 You can use the @code{thread} qualifier on conditional breakpoints as
5225 well; in this case, place @samp{thread @var{threadno}} before or
5226 after the breakpoint condition, like this:
5229 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5234 @node Interrupted System Calls
5235 @subsection Interrupted System Calls
5237 @cindex thread breakpoints and system calls
5238 @cindex system calls and thread breakpoints
5239 @cindex premature return from system calls
5240 There is an unfortunate side effect when using @value{GDBN} to debug
5241 multi-threaded programs. If one thread stops for a
5242 breakpoint, or for some other reason, and another thread is blocked in a
5243 system call, then the system call may return prematurely. This is a
5244 consequence of the interaction between multiple threads and the signals
5245 that @value{GDBN} uses to implement breakpoints and other events that
5248 To handle this problem, your program should check the return value of
5249 each system call and react appropriately. This is good programming
5252 For example, do not write code like this:
5258 The call to @code{sleep} will return early if a different thread stops
5259 at a breakpoint or for some other reason.
5261 Instead, write this:
5266 unslept = sleep (unslept);
5269 A system call is allowed to return early, so the system is still
5270 conforming to its specification. But @value{GDBN} does cause your
5271 multi-threaded program to behave differently than it would without
5274 Also, @value{GDBN} uses internal breakpoints in the thread library to
5275 monitor certain events such as thread creation and thread destruction.
5276 When such an event happens, a system call in another thread may return
5277 prematurely, even though your program does not appear to stop.
5280 @node Reverse Execution
5281 @chapter Running programs backward
5282 @cindex reverse execution
5283 @cindex running programs backward
5285 When you are debugging a program, it is not unusual to realize that
5286 you have gone too far, and some event of interest has already happened.
5287 If the target environment supports it, @value{GDBN} can allow you to
5288 ``rewind'' the program by running it backward.
5290 A target environment that supports reverse execution should be able
5291 to ``undo'' the changes in machine state that have taken place as the
5292 program was executing normally. Variables, registers etc.@: should
5293 revert to their previous values. Obviously this requires a great
5294 deal of sophistication on the part of the target environment; not
5295 all target environments can support reverse execution.
5297 When a program is executed in reverse, the instructions that
5298 have most recently been executed are ``un-executed'', in reverse
5299 order. The program counter runs backward, following the previous
5300 thread of execution in reverse. As each instruction is ``un-executed'',
5301 the values of memory and/or registers that were changed by that
5302 instruction are reverted to their previous states. After executing
5303 a piece of source code in reverse, all side effects of that code
5304 should be ``undone'', and all variables should be returned to their
5305 prior values@footnote{
5306 Note that some side effects are easier to undo than others. For instance,
5307 memory and registers are relatively easy, but device I/O is hard. Some
5308 targets may be able undo things like device I/O, and some may not.
5310 The contract between @value{GDBN} and the reverse executing target
5311 requires only that the target do something reasonable when
5312 @value{GDBN} tells it to execute backwards, and then report the
5313 results back to @value{GDBN}. Whatever the target reports back to
5314 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5315 assumes that the memory and registers that the target reports are in a
5316 consistant state, but @value{GDBN} accepts whatever it is given.
5319 If you are debugging in a target environment that supports
5320 reverse execution, @value{GDBN} provides the following commands.
5323 @kindex reverse-continue
5324 @kindex rc @r{(@code{reverse-continue})}
5325 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5326 @itemx rc @r{[}@var{ignore-count}@r{]}
5327 Beginning at the point where your program last stopped, start executing
5328 in reverse. Reverse execution will stop for breakpoints and synchronous
5329 exceptions (signals), just like normal execution. Behavior of
5330 asynchronous signals depends on the target environment.
5332 @kindex reverse-step
5333 @kindex rs @r{(@code{step})}
5334 @item reverse-step @r{[}@var{count}@r{]}
5335 Run the program backward until control reaches the start of a
5336 different source line; then stop it, and return control to @value{GDBN}.
5338 Like the @code{step} command, @code{reverse-step} will only stop
5339 at the beginning of a source line. It ``un-executes'' the previously
5340 executed source line. If the previous source line included calls to
5341 debuggable functions, @code{reverse-step} will step (backward) into
5342 the called function, stopping at the beginning of the @emph{last}
5343 statement in the called function (typically a return statement).
5345 Also, as with the @code{step} command, if non-debuggable functions are
5346 called, @code{reverse-step} will run thru them backward without stopping.
5348 @kindex reverse-stepi
5349 @kindex rsi @r{(@code{reverse-stepi})}
5350 @item reverse-stepi @r{[}@var{count}@r{]}
5351 Reverse-execute one machine instruction. Note that the instruction
5352 to be reverse-executed is @emph{not} the one pointed to by the program
5353 counter, but the instruction executed prior to that one. For instance,
5354 if the last instruction was a jump, @code{reverse-stepi} will take you
5355 back from the destination of the jump to the jump instruction itself.
5357 @kindex reverse-next
5358 @kindex rn @r{(@code{reverse-next})}
5359 @item reverse-next @r{[}@var{count}@r{]}
5360 Run backward to the beginning of the previous line executed in
5361 the current (innermost) stack frame. If the line contains function
5362 calls, they will be ``un-executed'' without stopping. Starting from
5363 the first line of a function, @code{reverse-next} will take you back
5364 to the caller of that function, @emph{before} the function was called,
5365 just as the normal @code{next} command would take you from the last
5366 line of a function back to its return to its caller
5367 @footnote{Unless the code is too heavily optimized.}.
5369 @kindex reverse-nexti
5370 @kindex rni @r{(@code{reverse-nexti})}
5371 @item reverse-nexti @r{[}@var{count}@r{]}
5372 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5373 in reverse, except that called functions are ``un-executed'' atomically.
5374 That is, if the previously executed instruction was a return from
5375 another function, @code{reverse-nexti} will continue to execute
5376 in reverse until the call to that function (from the current stack
5379 @kindex reverse-finish
5380 @item reverse-finish
5381 Just as the @code{finish} command takes you to the point where the
5382 current function returns, @code{reverse-finish} takes you to the point
5383 where it was called. Instead of ending up at the end of the current
5384 function invocation, you end up at the beginning.
5386 @kindex set exec-direction
5387 @item set exec-direction
5388 Set the direction of target execution.
5389 @itemx set exec-direction reverse
5390 @cindex execute forward or backward in time
5391 @value{GDBN} will perform all execution commands in reverse, until the
5392 exec-direction mode is changed to ``forward''. Affected commands include
5393 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5394 command cannot be used in reverse mode.
5395 @item set exec-direction forward
5396 @value{GDBN} will perform all execution commands in the normal fashion.
5397 This is the default.
5401 @node Process Record and Replay
5402 @chapter Recording Inferior's Execution and Replaying It
5403 @cindex process record and replay
5404 @cindex recording inferior's execution and replaying it
5406 On some platforms, @value{GDBN} provides a special @dfn{process record
5407 and replay} target that can record a log of the process execution, and
5408 replay it later with both forward and reverse execution commands.
5411 When this target is in use, if the execution log includes the record
5412 for the next instruction, @value{GDBN} will debug in @dfn{replay
5413 mode}. In the replay mode, the inferior does not really execute code
5414 instructions. Instead, all the events that normally happen during
5415 code execution are taken from the execution log. While code is not
5416 really executed in replay mode, the values of registers (including the
5417 program counter register) and the memory of the inferior are still
5418 changed as they normally would. Their contents are taken from the
5422 If the record for the next instruction is not in the execution log,
5423 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5424 inferior executes normally, and @value{GDBN} records the execution log
5427 The process record and replay target supports reverse execution
5428 (@pxref{Reverse Execution}), even if the platform on which the
5429 inferior runs does not. However, the reverse execution is limited in
5430 this case by the range of the instructions recorded in the execution
5431 log. In other words, reverse execution on platforms that don't
5432 support it directly can only be done in the replay mode.
5434 When debugging in the reverse direction, @value{GDBN} will work in
5435 replay mode as long as the execution log includes the record for the
5436 previous instruction; otherwise, it will work in record mode, if the
5437 platform supports reverse execution, or stop if not.
5439 For architecture environments that support process record and replay,
5440 @value{GDBN} provides the following commands:
5443 @kindex target record
5447 This command starts the process record and replay target. The process
5448 record and replay target can only debug a process that is already
5449 running. Therefore, you need first to start the process with the
5450 @kbd{run} or @kbd{start} commands, and then start the recording with
5451 the @kbd{target record} command.
5453 Both @code{record} and @code{rec} are aliases of @code{target record}.
5455 @cindex displaced stepping, and process record and replay
5456 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5457 will be automatically disabled when process record and replay target
5458 is started. That's because the process record and replay target
5459 doesn't support displaced stepping.
5461 @cindex non-stop mode, and process record and replay
5462 @cindex asynchronous execution, and process record and replay
5463 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5464 the asynchronous execution mode (@pxref{Background Execution}), the
5465 process record and replay target cannot be started because it doesn't
5466 support these two modes.
5471 Stop the process record and replay target. When process record and
5472 replay target stops, the entire execution log will be deleted and the
5473 inferior will either be terminated, or will remain in its final state.
5475 When you stop the process record and replay target in record mode (at
5476 the end of the execution log), the inferior will be stopped at the
5477 next instruction that would have been recorded. In other words, if
5478 you record for a while and then stop recording, the inferior process
5479 will be left in the same state as if the recording never happened.
5481 On the other hand, if the process record and replay target is stopped
5482 while in replay mode (that is, not at the end of the execution log,
5483 but at some earlier point), the inferior process will become ``live''
5484 at that earlier state, and it will then be possible to continue the
5485 usual ``live'' debugging of the process from that state.
5487 When the inferior process exits, or @value{GDBN} detaches from it,
5488 process record and replay target will automatically stop itself.
5490 @kindex set record insn-number-max
5491 @item set record insn-number-max @var{limit}
5492 Set the limit of instructions to be recorded. Default value is 200000.
5494 If @var{limit} is a positive number, then @value{GDBN} will start
5495 deleting instructions from the log once the number of the record
5496 instructions becomes greater than @var{limit}. For every new recorded
5497 instruction, @value{GDBN} will delete the earliest recorded
5498 instruction to keep the number of recorded instructions at the limit.
5499 (Since deleting recorded instructions loses information, @value{GDBN}
5500 lets you control what happens when the limit is reached, by means of
5501 the @code{stop-at-limit} option, described below.)
5503 If @var{limit} is zero, @value{GDBN} will never delete recorded
5504 instructions from the execution log. The number of recorded
5505 instructions is unlimited in this case.
5507 @kindex show record insn-number-max
5508 @item show record insn-number-max
5509 Show the limit of instructions to be recorded.
5511 @kindex set record stop-at-limit
5512 @item set record stop-at-limit
5513 Control the behavior when the number of recorded instructions reaches
5514 the limit. If ON (the default), @value{GDBN} will stop when the limit
5515 is reached for the first time and ask you whether you want to stop the
5516 inferior or continue running it and recording the execution log. If
5517 you decide to continue recording, each new recorded instruction will
5518 cause the oldest one to be deleted.
5520 If this option is OFF, @value{GDBN} will automatically delete the
5521 oldest record to make room for each new one, without asking.
5523 @kindex show record stop-at-limit
5524 @item show record stop-at-limit
5525 Show the current setting of @code{stop-at-limit}.
5529 Show various statistics about the state of process record and its
5530 in-memory execution log buffer, including:
5534 Whether in record mode or replay mode.
5536 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5538 Highest recorded instruction number.
5540 Current instruction about to be replayed (if in replay mode).
5542 Number of instructions contained in the execution log.
5544 Maximum number of instructions that may be contained in the execution log.
5547 @kindex record delete
5550 When record target runs in replay mode (``in the past''), delete the
5551 subsequent execution log and begin to record a new execution log starting
5552 from the current address. This means you will abandon the previously
5553 recorded ``future'' and begin recording a new ``future''.
5558 @chapter Examining the Stack
5560 When your program has stopped, the first thing you need to know is where it
5561 stopped and how it got there.
5564 Each time your program performs a function call, information about the call
5566 That information includes the location of the call in your program,
5567 the arguments of the call,
5568 and the local variables of the function being called.
5569 The information is saved in a block of data called a @dfn{stack frame}.
5570 The stack frames are allocated in a region of memory called the @dfn{call
5573 When your program stops, the @value{GDBN} commands for examining the
5574 stack allow you to see all of this information.
5576 @cindex selected frame
5577 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5578 @value{GDBN} commands refer implicitly to the selected frame. In
5579 particular, whenever you ask @value{GDBN} for the value of a variable in
5580 your program, the value is found in the selected frame. There are
5581 special @value{GDBN} commands to select whichever frame you are
5582 interested in. @xref{Selection, ,Selecting a Frame}.
5584 When your program stops, @value{GDBN} automatically selects the
5585 currently executing frame and describes it briefly, similar to the
5586 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5589 * Frames:: Stack frames
5590 * Backtrace:: Backtraces
5591 * Selection:: Selecting a frame
5592 * Frame Info:: Information on a frame
5597 @section Stack Frames
5599 @cindex frame, definition
5601 The call stack is divided up into contiguous pieces called @dfn{stack
5602 frames}, or @dfn{frames} for short; each frame is the data associated
5603 with one call to one function. The frame contains the arguments given
5604 to the function, the function's local variables, and the address at
5605 which the function is executing.
5607 @cindex initial frame
5608 @cindex outermost frame
5609 @cindex innermost frame
5610 When your program is started, the stack has only one frame, that of the
5611 function @code{main}. This is called the @dfn{initial} frame or the
5612 @dfn{outermost} frame. Each time a function is called, a new frame is
5613 made. Each time a function returns, the frame for that function invocation
5614 is eliminated. If a function is recursive, there can be many frames for
5615 the same function. The frame for the function in which execution is
5616 actually occurring is called the @dfn{innermost} frame. This is the most
5617 recently created of all the stack frames that still exist.
5619 @cindex frame pointer
5620 Inside your program, stack frames are identified by their addresses. A
5621 stack frame consists of many bytes, each of which has its own address; each
5622 kind of computer has a convention for choosing one byte whose
5623 address serves as the address of the frame. Usually this address is kept
5624 in a register called the @dfn{frame pointer register}
5625 (@pxref{Registers, $fp}) while execution is going on in that frame.
5627 @cindex frame number
5628 @value{GDBN} assigns numbers to all existing stack frames, starting with
5629 zero for the innermost frame, one for the frame that called it,
5630 and so on upward. These numbers do not really exist in your program;
5631 they are assigned by @value{GDBN} to give you a way of designating stack
5632 frames in @value{GDBN} commands.
5634 @c The -fomit-frame-pointer below perennially causes hbox overflow
5635 @c underflow problems.
5636 @cindex frameless execution
5637 Some compilers provide a way to compile functions so that they operate
5638 without stack frames. (For example, the @value{NGCC} option
5640 @samp{-fomit-frame-pointer}
5642 generates functions without a frame.)
5643 This is occasionally done with heavily used library functions to save
5644 the frame setup time. @value{GDBN} has limited facilities for dealing
5645 with these function invocations. If the innermost function invocation
5646 has no stack frame, @value{GDBN} nevertheless regards it as though
5647 it had a separate frame, which is numbered zero as usual, allowing
5648 correct tracing of the function call chain. However, @value{GDBN} has
5649 no provision for frameless functions elsewhere in the stack.
5652 @kindex frame@r{, command}
5653 @cindex current stack frame
5654 @item frame @var{args}
5655 The @code{frame} command allows you to move from one stack frame to another,
5656 and to print the stack frame you select. @var{args} may be either the
5657 address of the frame or the stack frame number. Without an argument,
5658 @code{frame} prints the current stack frame.
5660 @kindex select-frame
5661 @cindex selecting frame silently
5663 The @code{select-frame} command allows you to move from one stack frame
5664 to another without printing the frame. This is the silent version of
5672 @cindex call stack traces
5673 A backtrace is a summary of how your program got where it is. It shows one
5674 line per frame, for many frames, starting with the currently executing
5675 frame (frame zero), followed by its caller (frame one), and on up the
5680 @kindex bt @r{(@code{backtrace})}
5683 Print a backtrace of the entire stack: one line per frame for all
5684 frames in the stack.
5686 You can stop the backtrace at any time by typing the system interrupt
5687 character, normally @kbd{Ctrl-c}.
5689 @item backtrace @var{n}
5691 Similar, but print only the innermost @var{n} frames.
5693 @item backtrace -@var{n}
5695 Similar, but print only the outermost @var{n} frames.
5697 @item backtrace full
5699 @itemx bt full @var{n}
5700 @itemx bt full -@var{n}
5701 Print the values of the local variables also. @var{n} specifies the
5702 number of frames to print, as described above.
5707 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5708 are additional aliases for @code{backtrace}.
5710 @cindex multiple threads, backtrace
5711 In a multi-threaded program, @value{GDBN} by default shows the
5712 backtrace only for the current thread. To display the backtrace for
5713 several or all of the threads, use the command @code{thread apply}
5714 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5715 apply all backtrace}, @value{GDBN} will display the backtrace for all
5716 the threads; this is handy when you debug a core dump of a
5717 multi-threaded program.
5719 Each line in the backtrace shows the frame number and the function name.
5720 The program counter value is also shown---unless you use @code{set
5721 print address off}. The backtrace also shows the source file name and
5722 line number, as well as the arguments to the function. The program
5723 counter value is omitted if it is at the beginning of the code for that
5726 Here is an example of a backtrace. It was made with the command
5727 @samp{bt 3}, so it shows the innermost three frames.
5731 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5733 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5734 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5736 (More stack frames follow...)
5741 The display for frame zero does not begin with a program counter
5742 value, indicating that your program has stopped at the beginning of the
5743 code for line @code{993} of @code{builtin.c}.
5746 The value of parameter @code{data} in frame 1 has been replaced by
5747 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5748 only if it is a scalar (integer, pointer, enumeration, etc). See command
5749 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5750 on how to configure the way function parameter values are printed.
5752 @cindex value optimized out, in backtrace
5753 @cindex function call arguments, optimized out
5754 If your program was compiled with optimizations, some compilers will
5755 optimize away arguments passed to functions if those arguments are
5756 never used after the call. Such optimizations generate code that
5757 passes arguments through registers, but doesn't store those arguments
5758 in the stack frame. @value{GDBN} has no way of displaying such
5759 arguments in stack frames other than the innermost one. Here's what
5760 such a backtrace might look like:
5764 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5766 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5767 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5769 (More stack frames follow...)
5774 The values of arguments that were not saved in their stack frames are
5775 shown as @samp{<value optimized out>}.
5777 If you need to display the values of such optimized-out arguments,
5778 either deduce that from other variables whose values depend on the one
5779 you are interested in, or recompile without optimizations.
5781 @cindex backtrace beyond @code{main} function
5782 @cindex program entry point
5783 @cindex startup code, and backtrace
5784 Most programs have a standard user entry point---a place where system
5785 libraries and startup code transition into user code. For C this is
5786 @code{main}@footnote{
5787 Note that embedded programs (the so-called ``free-standing''
5788 environment) are not required to have a @code{main} function as the
5789 entry point. They could even have multiple entry points.}.
5790 When @value{GDBN} finds the entry function in a backtrace
5791 it will terminate the backtrace, to avoid tracing into highly
5792 system-specific (and generally uninteresting) code.
5794 If you need to examine the startup code, or limit the number of levels
5795 in a backtrace, you can change this behavior:
5798 @item set backtrace past-main
5799 @itemx set backtrace past-main on
5800 @kindex set backtrace
5801 Backtraces will continue past the user entry point.
5803 @item set backtrace past-main off
5804 Backtraces will stop when they encounter the user entry point. This is the
5807 @item show backtrace past-main
5808 @kindex show backtrace
5809 Display the current user entry point backtrace policy.
5811 @item set backtrace past-entry
5812 @itemx set backtrace past-entry on
5813 Backtraces will continue past the internal entry point of an application.
5814 This entry point is encoded by the linker when the application is built,
5815 and is likely before the user entry point @code{main} (or equivalent) is called.
5817 @item set backtrace past-entry off
5818 Backtraces will stop when they encounter the internal entry point of an
5819 application. This is the default.
5821 @item show backtrace past-entry
5822 Display the current internal entry point backtrace policy.
5824 @item set backtrace limit @var{n}
5825 @itemx set backtrace limit 0
5826 @cindex backtrace limit
5827 Limit the backtrace to @var{n} levels. A value of zero means
5830 @item show backtrace limit
5831 Display the current limit on backtrace levels.
5835 @section Selecting a Frame
5837 Most commands for examining the stack and other data in your program work on
5838 whichever stack frame is selected at the moment. Here are the commands for
5839 selecting a stack frame; all of them finish by printing a brief description
5840 of the stack frame just selected.
5843 @kindex frame@r{, selecting}
5844 @kindex f @r{(@code{frame})}
5847 Select frame number @var{n}. Recall that frame zero is the innermost
5848 (currently executing) frame, frame one is the frame that called the
5849 innermost one, and so on. The highest-numbered frame is the one for
5852 @item frame @var{addr}
5854 Select the frame at address @var{addr}. This is useful mainly if the
5855 chaining of stack frames has been damaged by a bug, making it
5856 impossible for @value{GDBN} to assign numbers properly to all frames. In
5857 addition, this can be useful when your program has multiple stacks and
5858 switches between them.
5860 On the SPARC architecture, @code{frame} needs two addresses to
5861 select an arbitrary frame: a frame pointer and a stack pointer.
5863 On the MIPS and Alpha architecture, it needs two addresses: a stack
5864 pointer and a program counter.
5866 On the 29k architecture, it needs three addresses: a register stack
5867 pointer, a program counter, and a memory stack pointer.
5871 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5872 advances toward the outermost frame, to higher frame numbers, to frames
5873 that have existed longer. @var{n} defaults to one.
5876 @kindex do @r{(@code{down})}
5878 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5879 advances toward the innermost frame, to lower frame numbers, to frames
5880 that were created more recently. @var{n} defaults to one. You may
5881 abbreviate @code{down} as @code{do}.
5884 All of these commands end by printing two lines of output describing the
5885 frame. The first line shows the frame number, the function name, the
5886 arguments, and the source file and line number of execution in that
5887 frame. The second line shows the text of that source line.
5895 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5897 10 read_input_file (argv[i]);
5901 After such a printout, the @code{list} command with no arguments
5902 prints ten lines centered on the point of execution in the frame.
5903 You can also edit the program at the point of execution with your favorite
5904 editing program by typing @code{edit}.
5905 @xref{List, ,Printing Source Lines},
5909 @kindex down-silently
5911 @item up-silently @var{n}
5912 @itemx down-silently @var{n}
5913 These two commands are variants of @code{up} and @code{down},
5914 respectively; they differ in that they do their work silently, without
5915 causing display of the new frame. They are intended primarily for use
5916 in @value{GDBN} command scripts, where the output might be unnecessary and
5921 @section Information About a Frame
5923 There are several other commands to print information about the selected
5929 When used without any argument, this command does not change which
5930 frame is selected, but prints a brief description of the currently
5931 selected stack frame. It can be abbreviated @code{f}. With an
5932 argument, this command is used to select a stack frame.
5933 @xref{Selection, ,Selecting a Frame}.
5936 @kindex info f @r{(@code{info frame})}
5939 This command prints a verbose description of the selected stack frame,
5944 the address of the frame
5946 the address of the next frame down (called by this frame)
5948 the address of the next frame up (caller of this frame)
5950 the language in which the source code corresponding to this frame is written
5952 the address of the frame's arguments
5954 the address of the frame's local variables
5956 the program counter saved in it (the address of execution in the caller frame)
5958 which registers were saved in the frame
5961 @noindent The verbose description is useful when
5962 something has gone wrong that has made the stack format fail to fit
5963 the usual conventions.
5965 @item info frame @var{addr}
5966 @itemx info f @var{addr}
5967 Print a verbose description of the frame at address @var{addr}, without
5968 selecting that frame. The selected frame remains unchanged by this
5969 command. This requires the same kind of address (more than one for some
5970 architectures) that you specify in the @code{frame} command.
5971 @xref{Selection, ,Selecting a Frame}.
5975 Print the arguments of the selected frame, each on a separate line.
5979 Print the local variables of the selected frame, each on a separate
5980 line. These are all variables (declared either static or automatic)
5981 accessible at the point of execution of the selected frame.
5984 @cindex catch exceptions, list active handlers
5985 @cindex exception handlers, how to list
5987 Print a list of all the exception handlers that are active in the
5988 current stack frame at the current point of execution. To see other
5989 exception handlers, visit the associated frame (using the @code{up},
5990 @code{down}, or @code{frame} commands); then type @code{info catch}.
5991 @xref{Set Catchpoints, , Setting Catchpoints}.
5997 @chapter Examining Source Files
5999 @value{GDBN} can print parts of your program's source, since the debugging
6000 information recorded in the program tells @value{GDBN} what source files were
6001 used to build it. When your program stops, @value{GDBN} spontaneously prints
6002 the line where it stopped. Likewise, when you select a stack frame
6003 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6004 execution in that frame has stopped. You can print other portions of
6005 source files by explicit command.
6007 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6008 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6009 @value{GDBN} under @sc{gnu} Emacs}.
6012 * List:: Printing source lines
6013 * Specify Location:: How to specify code locations
6014 * Edit:: Editing source files
6015 * Search:: Searching source files
6016 * Source Path:: Specifying source directories
6017 * Machine Code:: Source and machine code
6021 @section Printing Source Lines
6024 @kindex l @r{(@code{list})}
6025 To print lines from a source file, use the @code{list} command
6026 (abbreviated @code{l}). By default, ten lines are printed.
6027 There are several ways to specify what part of the file you want to
6028 print; see @ref{Specify Location}, for the full list.
6030 Here are the forms of the @code{list} command most commonly used:
6033 @item list @var{linenum}
6034 Print lines centered around line number @var{linenum} in the
6035 current source file.
6037 @item list @var{function}
6038 Print lines centered around the beginning of function
6042 Print more lines. If the last lines printed were printed with a
6043 @code{list} command, this prints lines following the last lines
6044 printed; however, if the last line printed was a solitary line printed
6045 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6046 Stack}), this prints lines centered around that line.
6049 Print lines just before the lines last printed.
6052 @cindex @code{list}, how many lines to display
6053 By default, @value{GDBN} prints ten source lines with any of these forms of
6054 the @code{list} command. You can change this using @code{set listsize}:
6057 @kindex set listsize
6058 @item set listsize @var{count}
6059 Make the @code{list} command display @var{count} source lines (unless
6060 the @code{list} argument explicitly specifies some other number).
6062 @kindex show listsize
6064 Display the number of lines that @code{list} prints.
6067 Repeating a @code{list} command with @key{RET} discards the argument,
6068 so it is equivalent to typing just @code{list}. This is more useful
6069 than listing the same lines again. An exception is made for an
6070 argument of @samp{-}; that argument is preserved in repetition so that
6071 each repetition moves up in the source file.
6073 In general, the @code{list} command expects you to supply zero, one or two
6074 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6075 of writing them (@pxref{Specify Location}), but the effect is always
6076 to specify some source line.
6078 Here is a complete description of the possible arguments for @code{list}:
6081 @item list @var{linespec}
6082 Print lines centered around the line specified by @var{linespec}.
6084 @item list @var{first},@var{last}
6085 Print lines from @var{first} to @var{last}. Both arguments are
6086 linespecs. When a @code{list} command has two linespecs, and the
6087 source file of the second linespec is omitted, this refers to
6088 the same source file as the first linespec.
6090 @item list ,@var{last}
6091 Print lines ending with @var{last}.
6093 @item list @var{first},
6094 Print lines starting with @var{first}.
6097 Print lines just after the lines last printed.
6100 Print lines just before the lines last printed.
6103 As described in the preceding table.
6106 @node Specify Location
6107 @section Specifying a Location
6108 @cindex specifying location
6111 Several @value{GDBN} commands accept arguments that specify a location
6112 of your program's code. Since @value{GDBN} is a source-level
6113 debugger, a location usually specifies some line in the source code;
6114 for that reason, locations are also known as @dfn{linespecs}.
6116 Here are all the different ways of specifying a code location that
6117 @value{GDBN} understands:
6121 Specifies the line number @var{linenum} of the current source file.
6124 @itemx +@var{offset}
6125 Specifies the line @var{offset} lines before or after the @dfn{current
6126 line}. For the @code{list} command, the current line is the last one
6127 printed; for the breakpoint commands, this is the line at which
6128 execution stopped in the currently selected @dfn{stack frame}
6129 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6130 used as the second of the two linespecs in a @code{list} command,
6131 this specifies the line @var{offset} lines up or down from the first
6134 @item @var{filename}:@var{linenum}
6135 Specifies the line @var{linenum} in the source file @var{filename}.
6137 @item @var{function}
6138 Specifies the line that begins the body of the function @var{function}.
6139 For example, in C, this is the line with the open brace.
6141 @item @var{filename}:@var{function}
6142 Specifies the line that begins the body of the function @var{function}
6143 in the file @var{filename}. You only need the file name with a
6144 function name to avoid ambiguity when there are identically named
6145 functions in different source files.
6147 @item *@var{address}
6148 Specifies the program address @var{address}. For line-oriented
6149 commands, such as @code{list} and @code{edit}, this specifies a source
6150 line that contains @var{address}. For @code{break} and other
6151 breakpoint oriented commands, this can be used to set breakpoints in
6152 parts of your program which do not have debugging information or
6155 Here @var{address} may be any expression valid in the current working
6156 language (@pxref{Languages, working language}) that specifies a code
6157 address. In addition, as a convenience, @value{GDBN} extends the
6158 semantics of expressions used in locations to cover the situations
6159 that frequently happen during debugging. Here are the various forms
6163 @item @var{expression}
6164 Any expression valid in the current working language.
6166 @item @var{funcaddr}
6167 An address of a function or procedure derived from its name. In C,
6168 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6169 simply the function's name @var{function} (and actually a special case
6170 of a valid expression). In Pascal and Modula-2, this is
6171 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6172 (although the Pascal form also works).
6174 This form specifies the address of the function's first instruction,
6175 before the stack frame and arguments have been set up.
6177 @item '@var{filename}'::@var{funcaddr}
6178 Like @var{funcaddr} above, but also specifies the name of the source
6179 file explicitly. This is useful if the name of the function does not
6180 specify the function unambiguously, e.g., if there are several
6181 functions with identical names in different source files.
6188 @section Editing Source Files
6189 @cindex editing source files
6192 @kindex e @r{(@code{edit})}
6193 To edit the lines in a source file, use the @code{edit} command.
6194 The editing program of your choice
6195 is invoked with the current line set to
6196 the active line in the program.
6197 Alternatively, there are several ways to specify what part of the file you
6198 want to print if you want to see other parts of the program:
6201 @item edit @var{location}
6202 Edit the source file specified by @code{location}. Editing starts at
6203 that @var{location}, e.g., at the specified source line of the
6204 specified file. @xref{Specify Location}, for all the possible forms
6205 of the @var{location} argument; here are the forms of the @code{edit}
6206 command most commonly used:
6209 @item edit @var{number}
6210 Edit the current source file with @var{number} as the active line number.
6212 @item edit @var{function}
6213 Edit the file containing @var{function} at the beginning of its definition.
6218 @subsection Choosing your Editor
6219 You can customize @value{GDBN} to use any editor you want
6221 The only restriction is that your editor (say @code{ex}), recognizes the
6222 following command-line syntax:
6224 ex +@var{number} file
6226 The optional numeric value +@var{number} specifies the number of the line in
6227 the file where to start editing.}.
6228 By default, it is @file{@value{EDITOR}}, but you can change this
6229 by setting the environment variable @code{EDITOR} before using
6230 @value{GDBN}. For example, to configure @value{GDBN} to use the
6231 @code{vi} editor, you could use these commands with the @code{sh} shell:
6237 or in the @code{csh} shell,
6239 setenv EDITOR /usr/bin/vi
6244 @section Searching Source Files
6245 @cindex searching source files
6247 There are two commands for searching through the current source file for a
6252 @kindex forward-search
6253 @item forward-search @var{regexp}
6254 @itemx search @var{regexp}
6255 The command @samp{forward-search @var{regexp}} checks each line,
6256 starting with the one following the last line listed, for a match for
6257 @var{regexp}. It lists the line that is found. You can use the
6258 synonym @samp{search @var{regexp}} or abbreviate the command name as
6261 @kindex reverse-search
6262 @item reverse-search @var{regexp}
6263 The command @samp{reverse-search @var{regexp}} checks each line, starting
6264 with the one before the last line listed and going backward, for a match
6265 for @var{regexp}. It lists the line that is found. You can abbreviate
6266 this command as @code{rev}.
6270 @section Specifying Source Directories
6273 @cindex directories for source files
6274 Executable programs sometimes do not record the directories of the source
6275 files from which they were compiled, just the names. Even when they do,
6276 the directories could be moved between the compilation and your debugging
6277 session. @value{GDBN} has a list of directories to search for source files;
6278 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6279 it tries all the directories in the list, in the order they are present
6280 in the list, until it finds a file with the desired name.
6282 For example, suppose an executable references the file
6283 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6284 @file{/mnt/cross}. The file is first looked up literally; if this
6285 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6286 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6287 message is printed. @value{GDBN} does not look up the parts of the
6288 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6289 Likewise, the subdirectories of the source path are not searched: if
6290 the source path is @file{/mnt/cross}, and the binary refers to
6291 @file{foo.c}, @value{GDBN} would not find it under
6292 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6294 Plain file names, relative file names with leading directories, file
6295 names containing dots, etc.@: are all treated as described above; for
6296 instance, if the source path is @file{/mnt/cross}, and the source file
6297 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6298 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6299 that---@file{/mnt/cross/foo.c}.
6301 Note that the executable search path is @emph{not} used to locate the
6304 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6305 any information it has cached about where source files are found and where
6306 each line is in the file.
6310 When you start @value{GDBN}, its source path includes only @samp{cdir}
6311 and @samp{cwd}, in that order.
6312 To add other directories, use the @code{directory} command.
6314 The search path is used to find both program source files and @value{GDBN}
6315 script files (read using the @samp{-command} option and @samp{source} command).
6317 In addition to the source path, @value{GDBN} provides a set of commands
6318 that manage a list of source path substitution rules. A @dfn{substitution
6319 rule} specifies how to rewrite source directories stored in the program's
6320 debug information in case the sources were moved to a different
6321 directory between compilation and debugging. A rule is made of
6322 two strings, the first specifying what needs to be rewritten in
6323 the path, and the second specifying how it should be rewritten.
6324 In @ref{set substitute-path}, we name these two parts @var{from} and
6325 @var{to} respectively. @value{GDBN} does a simple string replacement
6326 of @var{from} with @var{to} at the start of the directory part of the
6327 source file name, and uses that result instead of the original file
6328 name to look up the sources.
6330 Using the previous example, suppose the @file{foo-1.0} tree has been
6331 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6332 @value{GDBN} to replace @file{/usr/src} in all source path names with
6333 @file{/mnt/cross}. The first lookup will then be
6334 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6335 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6336 substitution rule, use the @code{set substitute-path} command
6337 (@pxref{set substitute-path}).
6339 To avoid unexpected substitution results, a rule is applied only if the
6340 @var{from} part of the directory name ends at a directory separator.
6341 For instance, a rule substituting @file{/usr/source} into
6342 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6343 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6344 is applied only at the beginning of the directory name, this rule will
6345 not be applied to @file{/root/usr/source/baz.c} either.
6347 In many cases, you can achieve the same result using the @code{directory}
6348 command. However, @code{set substitute-path} can be more efficient in
6349 the case where the sources are organized in a complex tree with multiple
6350 subdirectories. With the @code{directory} command, you need to add each
6351 subdirectory of your project. If you moved the entire tree while
6352 preserving its internal organization, then @code{set substitute-path}
6353 allows you to direct the debugger to all the sources with one single
6356 @code{set substitute-path} is also more than just a shortcut command.
6357 The source path is only used if the file at the original location no
6358 longer exists. On the other hand, @code{set substitute-path} modifies
6359 the debugger behavior to look at the rewritten location instead. So, if
6360 for any reason a source file that is not relevant to your executable is
6361 located at the original location, a substitution rule is the only
6362 method available to point @value{GDBN} at the new location.
6364 @cindex @samp{--with-relocated-sources}
6365 @cindex default source path substitution
6366 You can configure a default source path substitution rule by
6367 configuring @value{GDBN} with the
6368 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6369 should be the name of a directory under @value{GDBN}'s configured
6370 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6371 directory names in debug information under @var{dir} will be adjusted
6372 automatically if the installed @value{GDBN} is moved to a new
6373 location. This is useful if @value{GDBN}, libraries or executables
6374 with debug information and corresponding source code are being moved
6378 @item directory @var{dirname} @dots{}
6379 @item dir @var{dirname} @dots{}
6380 Add directory @var{dirname} to the front of the source path. Several
6381 directory names may be given to this command, separated by @samp{:}
6382 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6383 part of absolute file names) or
6384 whitespace. You may specify a directory that is already in the source
6385 path; this moves it forward, so @value{GDBN} searches it sooner.
6389 @vindex $cdir@r{, convenience variable}
6390 @vindex $cwd@r{, convenience variable}
6391 @cindex compilation directory
6392 @cindex current directory
6393 @cindex working directory
6394 @cindex directory, current
6395 @cindex directory, compilation
6396 You can use the string @samp{$cdir} to refer to the compilation
6397 directory (if one is recorded), and @samp{$cwd} to refer to the current
6398 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6399 tracks the current working directory as it changes during your @value{GDBN}
6400 session, while the latter is immediately expanded to the current
6401 directory at the time you add an entry to the source path.
6404 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6406 @c RET-repeat for @code{directory} is explicitly disabled, but since
6407 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6409 @item show directories
6410 @kindex show directories
6411 Print the source path: show which directories it contains.
6413 @anchor{set substitute-path}
6414 @item set substitute-path @var{from} @var{to}
6415 @kindex set substitute-path
6416 Define a source path substitution rule, and add it at the end of the
6417 current list of existing substitution rules. If a rule with the same
6418 @var{from} was already defined, then the old rule is also deleted.
6420 For example, if the file @file{/foo/bar/baz.c} was moved to
6421 @file{/mnt/cross/baz.c}, then the command
6424 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6428 will tell @value{GDBN} to replace @samp{/usr/src} with
6429 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6430 @file{baz.c} even though it was moved.
6432 In the case when more than one substitution rule have been defined,
6433 the rules are evaluated one by one in the order where they have been
6434 defined. The first one matching, if any, is selected to perform
6437 For instance, if we had entered the following commands:
6440 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6441 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6445 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6446 @file{/mnt/include/defs.h} by using the first rule. However, it would
6447 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6448 @file{/mnt/src/lib/foo.c}.
6451 @item unset substitute-path [path]
6452 @kindex unset substitute-path
6453 If a path is specified, search the current list of substitution rules
6454 for a rule that would rewrite that path. Delete that rule if found.
6455 A warning is emitted by the debugger if no rule could be found.
6457 If no path is specified, then all substitution rules are deleted.
6459 @item show substitute-path [path]
6460 @kindex show substitute-path
6461 If a path is specified, then print the source path substitution rule
6462 which would rewrite that path, if any.
6464 If no path is specified, then print all existing source path substitution
6469 If your source path is cluttered with directories that are no longer of
6470 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6471 versions of source. You can correct the situation as follows:
6475 Use @code{directory} with no argument to reset the source path to its default value.
6478 Use @code{directory} with suitable arguments to reinstall the
6479 directories you want in the source path. You can add all the
6480 directories in one command.
6484 @section Source and Machine Code
6485 @cindex source line and its code address
6487 You can use the command @code{info line} to map source lines to program
6488 addresses (and vice versa), and the command @code{disassemble} to display
6489 a range of addresses as machine instructions. You can use the command
6490 @code{set disassemble-next-line} to set whether to disassemble next
6491 source line when execution stops. When run under @sc{gnu} Emacs
6492 mode, the @code{info line} command causes the arrow to point to the
6493 line specified. Also, @code{info line} prints addresses in symbolic form as
6498 @item info line @var{linespec}
6499 Print the starting and ending addresses of the compiled code for
6500 source line @var{linespec}. You can specify source lines in any of
6501 the ways documented in @ref{Specify Location}.
6504 For example, we can use @code{info line} to discover the location of
6505 the object code for the first line of function
6506 @code{m4_changequote}:
6508 @c FIXME: I think this example should also show the addresses in
6509 @c symbolic form, as they usually would be displayed.
6511 (@value{GDBP}) info line m4_changequote
6512 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6516 @cindex code address and its source line
6517 We can also inquire (using @code{*@var{addr}} as the form for
6518 @var{linespec}) what source line covers a particular address:
6520 (@value{GDBP}) info line *0x63ff
6521 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6524 @cindex @code{$_} and @code{info line}
6525 @cindex @code{x} command, default address
6526 @kindex x@r{(examine), and} info line
6527 After @code{info line}, the default address for the @code{x} command
6528 is changed to the starting address of the line, so that @samp{x/i} is
6529 sufficient to begin examining the machine code (@pxref{Memory,
6530 ,Examining Memory}). Also, this address is saved as the value of the
6531 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6536 @cindex assembly instructions
6537 @cindex instructions, assembly
6538 @cindex machine instructions
6539 @cindex listing machine instructions
6541 @itemx disassemble /m
6542 @itemx disassemble /r
6543 This specialized command dumps a range of memory as machine
6544 instructions. It can also print mixed source+disassembly by specifying
6545 the @code{/m} modifier and print the raw instructions in hex as well as
6546 in symbolic form by specifying the @code{/r}.
6547 The default memory range is the function surrounding the
6548 program counter of the selected frame. A single argument to this
6549 command is a program counter value; @value{GDBN} dumps the function
6550 surrounding this value. When two arguments are given, they should
6551 be separated by a comma, possibly surrounded by whitespace. The
6552 arguments specify a range of addresses (first inclusive, second exclusive)
6553 to dump. In that case, the name of the function is also printed (since
6554 there could be several functions in the given range).
6556 The argument(s) can be any expression yielding a numeric value, such as
6557 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6559 If the range of memory being disassembled contains current program counter,
6560 the instruction at that location is shown with a @code{=>} marker.
6563 The following example shows the disassembly of a range of addresses of
6564 HP PA-RISC 2.0 code:
6567 (@value{GDBP}) disas 0x32c4, 0x32e4
6568 Dump of assembler code from 0x32c4 to 0x32e4:
6569 0x32c4 <main+204>: addil 0,dp
6570 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6571 0x32cc <main+212>: ldil 0x3000,r31
6572 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6573 0x32d4 <main+220>: ldo 0(r31),rp
6574 0x32d8 <main+224>: addil -0x800,dp
6575 0x32dc <main+228>: ldo 0x588(r1),r26
6576 0x32e0 <main+232>: ldil 0x3000,r31
6577 End of assembler dump.
6580 Here is an example showing mixed source+assembly for Intel x86, when the
6581 program is stopped just after function prologue:
6584 (@value{GDBP}) disas /m main
6585 Dump of assembler code for function main:
6587 0x08048330 <+0>: push %ebp
6588 0x08048331 <+1>: mov %esp,%ebp
6589 0x08048333 <+3>: sub $0x8,%esp
6590 0x08048336 <+6>: and $0xfffffff0,%esp
6591 0x08048339 <+9>: sub $0x10,%esp
6593 6 printf ("Hello.\n");
6594 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6595 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6599 0x08048348 <+24>: mov $0x0,%eax
6600 0x0804834d <+29>: leave
6601 0x0804834e <+30>: ret
6603 End of assembler dump.
6606 Some architectures have more than one commonly-used set of instruction
6607 mnemonics or other syntax.
6609 For programs that were dynamically linked and use shared libraries,
6610 instructions that call functions or branch to locations in the shared
6611 libraries might show a seemingly bogus location---it's actually a
6612 location of the relocation table. On some architectures, @value{GDBN}
6613 might be able to resolve these to actual function names.
6616 @kindex set disassembly-flavor
6617 @cindex Intel disassembly flavor
6618 @cindex AT&T disassembly flavor
6619 @item set disassembly-flavor @var{instruction-set}
6620 Select the instruction set to use when disassembling the
6621 program via the @code{disassemble} or @code{x/i} commands.
6623 Currently this command is only defined for the Intel x86 family. You
6624 can set @var{instruction-set} to either @code{intel} or @code{att}.
6625 The default is @code{att}, the AT&T flavor used by default by Unix
6626 assemblers for x86-based targets.
6628 @kindex show disassembly-flavor
6629 @item show disassembly-flavor
6630 Show the current setting of the disassembly flavor.
6634 @kindex set disassemble-next-line
6635 @kindex show disassemble-next-line
6636 @item set disassemble-next-line
6637 @itemx show disassemble-next-line
6638 Control whether or not @value{GDBN} will disassemble the next source
6639 line or instruction when execution stops. If ON, @value{GDBN} will
6640 display disassembly of the next source line when execution of the
6641 program being debugged stops. This is @emph{in addition} to
6642 displaying the source line itself, which @value{GDBN} always does if
6643 possible. If the next source line cannot be displayed for some reason
6644 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6645 info in the debug info), @value{GDBN} will display disassembly of the
6646 next @emph{instruction} instead of showing the next source line. If
6647 AUTO, @value{GDBN} will display disassembly of next instruction only
6648 if the source line cannot be displayed. This setting causes
6649 @value{GDBN} to display some feedback when you step through a function
6650 with no line info or whose source file is unavailable. The default is
6651 OFF, which means never display the disassembly of the next line or
6657 @chapter Examining Data
6659 @cindex printing data
6660 @cindex examining data
6663 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6664 @c document because it is nonstandard... Under Epoch it displays in a
6665 @c different window or something like that.
6666 The usual way to examine data in your program is with the @code{print}
6667 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6668 evaluates and prints the value of an expression of the language your
6669 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6670 Different Languages}). It may also print the expression using a
6671 Python-based pretty-printer (@pxref{Pretty Printing}).
6674 @item print @var{expr}
6675 @itemx print /@var{f} @var{expr}
6676 @var{expr} is an expression (in the source language). By default the
6677 value of @var{expr} is printed in a format appropriate to its data type;
6678 you can choose a different format by specifying @samp{/@var{f}}, where
6679 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6683 @itemx print /@var{f}
6684 @cindex reprint the last value
6685 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6686 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6687 conveniently inspect the same value in an alternative format.
6690 A more low-level way of examining data is with the @code{x} command.
6691 It examines data in memory at a specified address and prints it in a
6692 specified format. @xref{Memory, ,Examining Memory}.
6694 If you are interested in information about types, or about how the
6695 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6696 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6700 * Expressions:: Expressions
6701 * Ambiguous Expressions:: Ambiguous Expressions
6702 * Variables:: Program variables
6703 * Arrays:: Artificial arrays
6704 * Output Formats:: Output formats
6705 * Memory:: Examining memory
6706 * Auto Display:: Automatic display
6707 * Print Settings:: Print settings
6708 * Value History:: Value history
6709 * Convenience Vars:: Convenience variables
6710 * Registers:: Registers
6711 * Floating Point Hardware:: Floating point hardware
6712 * Vector Unit:: Vector Unit
6713 * OS Information:: Auxiliary data provided by operating system
6714 * Memory Region Attributes:: Memory region attributes
6715 * Dump/Restore Files:: Copy between memory and a file
6716 * Core File Generation:: Cause a program dump its core
6717 * Character Sets:: Debugging programs that use a different
6718 character set than GDB does
6719 * Caching Remote Data:: Data caching for remote targets
6720 * Searching Memory:: Searching memory for a sequence of bytes
6724 @section Expressions
6727 @code{print} and many other @value{GDBN} commands accept an expression and
6728 compute its value. Any kind of constant, variable or operator defined
6729 by the programming language you are using is valid in an expression in
6730 @value{GDBN}. This includes conditional expressions, function calls,
6731 casts, and string constants. It also includes preprocessor macros, if
6732 you compiled your program to include this information; see
6735 @cindex arrays in expressions
6736 @value{GDBN} supports array constants in expressions input by
6737 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6738 you can use the command @code{print @{1, 2, 3@}} to create an array
6739 of three integers. If you pass an array to a function or assign it
6740 to a program variable, @value{GDBN} copies the array to memory that
6741 is @code{malloc}ed in the target program.
6743 Because C is so widespread, most of the expressions shown in examples in
6744 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6745 Languages}, for information on how to use expressions in other
6748 In this section, we discuss operators that you can use in @value{GDBN}
6749 expressions regardless of your programming language.
6751 @cindex casts, in expressions
6752 Casts are supported in all languages, not just in C, because it is so
6753 useful to cast a number into a pointer in order to examine a structure
6754 at that address in memory.
6755 @c FIXME: casts supported---Mod2 true?
6757 @value{GDBN} supports these operators, in addition to those common
6758 to programming languages:
6762 @samp{@@} is a binary operator for treating parts of memory as arrays.
6763 @xref{Arrays, ,Artificial Arrays}, for more information.
6766 @samp{::} allows you to specify a variable in terms of the file or
6767 function where it is defined. @xref{Variables, ,Program Variables}.
6769 @cindex @{@var{type}@}
6770 @cindex type casting memory
6771 @cindex memory, viewing as typed object
6772 @cindex casts, to view memory
6773 @item @{@var{type}@} @var{addr}
6774 Refers to an object of type @var{type} stored at address @var{addr} in
6775 memory. @var{addr} may be any expression whose value is an integer or
6776 pointer (but parentheses are required around binary operators, just as in
6777 a cast). This construct is allowed regardless of what kind of data is
6778 normally supposed to reside at @var{addr}.
6781 @node Ambiguous Expressions
6782 @section Ambiguous Expressions
6783 @cindex ambiguous expressions
6785 Expressions can sometimes contain some ambiguous elements. For instance,
6786 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6787 a single function name to be defined several times, for application in
6788 different contexts. This is called @dfn{overloading}. Another example
6789 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6790 templates and is typically instantiated several times, resulting in
6791 the same function name being defined in different contexts.
6793 In some cases and depending on the language, it is possible to adjust
6794 the expression to remove the ambiguity. For instance in C@t{++}, you
6795 can specify the signature of the function you want to break on, as in
6796 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6797 qualified name of your function often makes the expression unambiguous
6800 When an ambiguity that needs to be resolved is detected, the debugger
6801 has the capability to display a menu of numbered choices for each
6802 possibility, and then waits for the selection with the prompt @samp{>}.
6803 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6804 aborts the current command. If the command in which the expression was
6805 used allows more than one choice to be selected, the next option in the
6806 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6809 For example, the following session excerpt shows an attempt to set a
6810 breakpoint at the overloaded symbol @code{String::after}.
6811 We choose three particular definitions of that function name:
6813 @c FIXME! This is likely to change to show arg type lists, at least
6816 (@value{GDBP}) b String::after
6819 [2] file:String.cc; line number:867
6820 [3] file:String.cc; line number:860
6821 [4] file:String.cc; line number:875
6822 [5] file:String.cc; line number:853
6823 [6] file:String.cc; line number:846
6824 [7] file:String.cc; line number:735
6826 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6827 Breakpoint 2 at 0xb344: file String.cc, line 875.
6828 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6829 Multiple breakpoints were set.
6830 Use the "delete" command to delete unwanted
6837 @kindex set multiple-symbols
6838 @item set multiple-symbols @var{mode}
6839 @cindex multiple-symbols menu
6841 This option allows you to adjust the debugger behavior when an expression
6844 By default, @var{mode} is set to @code{all}. If the command with which
6845 the expression is used allows more than one choice, then @value{GDBN}
6846 automatically selects all possible choices. For instance, inserting
6847 a breakpoint on a function using an ambiguous name results in a breakpoint
6848 inserted on each possible match. However, if a unique choice must be made,
6849 then @value{GDBN} uses the menu to help you disambiguate the expression.
6850 For instance, printing the address of an overloaded function will result
6851 in the use of the menu.
6853 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6854 when an ambiguity is detected.
6856 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6857 an error due to the ambiguity and the command is aborted.
6859 @kindex show multiple-symbols
6860 @item show multiple-symbols
6861 Show the current value of the @code{multiple-symbols} setting.
6865 @section Program Variables
6867 The most common kind of expression to use is the name of a variable
6870 Variables in expressions are understood in the selected stack frame
6871 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6875 global (or file-static)
6882 visible according to the scope rules of the
6883 programming language from the point of execution in that frame
6886 @noindent This means that in the function
6901 you can examine and use the variable @code{a} whenever your program is
6902 executing within the function @code{foo}, but you can only use or
6903 examine the variable @code{b} while your program is executing inside
6904 the block where @code{b} is declared.
6906 @cindex variable name conflict
6907 There is an exception: you can refer to a variable or function whose
6908 scope is a single source file even if the current execution point is not
6909 in this file. But it is possible to have more than one such variable or
6910 function with the same name (in different source files). If that
6911 happens, referring to that name has unpredictable effects. If you wish,
6912 you can specify a static variable in a particular function or file,
6913 using the colon-colon (@code{::}) notation:
6915 @cindex colon-colon, context for variables/functions
6917 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6918 @cindex @code{::}, context for variables/functions
6921 @var{file}::@var{variable}
6922 @var{function}::@var{variable}
6926 Here @var{file} or @var{function} is the name of the context for the
6927 static @var{variable}. In the case of file names, you can use quotes to
6928 make sure @value{GDBN} parses the file name as a single word---for example,
6929 to print a global value of @code{x} defined in @file{f2.c}:
6932 (@value{GDBP}) p 'f2.c'::x
6935 @cindex C@t{++} scope resolution
6936 This use of @samp{::} is very rarely in conflict with the very similar
6937 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6938 scope resolution operator in @value{GDBN} expressions.
6939 @c FIXME: Um, so what happens in one of those rare cases where it's in
6942 @cindex wrong values
6943 @cindex variable values, wrong
6944 @cindex function entry/exit, wrong values of variables
6945 @cindex optimized code, wrong values of variables
6947 @emph{Warning:} Occasionally, a local variable may appear to have the
6948 wrong value at certain points in a function---just after entry to a new
6949 scope, and just before exit.
6951 You may see this problem when you are stepping by machine instructions.
6952 This is because, on most machines, it takes more than one instruction to
6953 set up a stack frame (including local variable definitions); if you are
6954 stepping by machine instructions, variables may appear to have the wrong
6955 values until the stack frame is completely built. On exit, it usually
6956 also takes more than one machine instruction to destroy a stack frame;
6957 after you begin stepping through that group of instructions, local
6958 variable definitions may be gone.
6960 This may also happen when the compiler does significant optimizations.
6961 To be sure of always seeing accurate values, turn off all optimization
6964 @cindex ``No symbol "foo" in current context''
6965 Another possible effect of compiler optimizations is to optimize
6966 unused variables out of existence, or assign variables to registers (as
6967 opposed to memory addresses). Depending on the support for such cases
6968 offered by the debug info format used by the compiler, @value{GDBN}
6969 might not be able to display values for such local variables. If that
6970 happens, @value{GDBN} will print a message like this:
6973 No symbol "foo" in current context.
6976 To solve such problems, either recompile without optimizations, or use a
6977 different debug info format, if the compiler supports several such
6978 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6979 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6980 produces debug info in a format that is superior to formats such as
6981 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6982 an effective form for debug info. @xref{Debugging Options,,Options
6983 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6984 Compiler Collection (GCC)}.
6985 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6986 that are best suited to C@t{++} programs.
6988 If you ask to print an object whose contents are unknown to
6989 @value{GDBN}, e.g., because its data type is not completely specified
6990 by the debug information, @value{GDBN} will say @samp{<incomplete
6991 type>}. @xref{Symbols, incomplete type}, for more about this.
6993 Strings are identified as arrays of @code{char} values without specified
6994 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6995 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6996 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6997 defines literal string type @code{"char"} as @code{char} without a sign.
7002 signed char var1[] = "A";
7005 You get during debugging
7010 $2 = @{65 'A', 0 '\0'@}
7014 @section Artificial Arrays
7016 @cindex artificial array
7018 @kindex @@@r{, referencing memory as an array}
7019 It is often useful to print out several successive objects of the
7020 same type in memory; a section of an array, or an array of
7021 dynamically determined size for which only a pointer exists in the
7024 You can do this by referring to a contiguous span of memory as an
7025 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7026 operand of @samp{@@} should be the first element of the desired array
7027 and be an individual object. The right operand should be the desired length
7028 of the array. The result is an array value whose elements are all of
7029 the type of the left argument. The first element is actually the left
7030 argument; the second element comes from bytes of memory immediately
7031 following those that hold the first element, and so on. Here is an
7032 example. If a program says
7035 int *array = (int *) malloc (len * sizeof (int));
7039 you can print the contents of @code{array} with
7045 The left operand of @samp{@@} must reside in memory. Array values made
7046 with @samp{@@} in this way behave just like other arrays in terms of
7047 subscripting, and are coerced to pointers when used in expressions.
7048 Artificial arrays most often appear in expressions via the value history
7049 (@pxref{Value History, ,Value History}), after printing one out.
7051 Another way to create an artificial array is to use a cast.
7052 This re-interprets a value as if it were an array.
7053 The value need not be in memory:
7055 (@value{GDBP}) p/x (short[2])0x12345678
7056 $1 = @{0x1234, 0x5678@}
7059 As a convenience, if you leave the array length out (as in
7060 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7061 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7063 (@value{GDBP}) p/x (short[])0x12345678
7064 $2 = @{0x1234, 0x5678@}
7067 Sometimes the artificial array mechanism is not quite enough; in
7068 moderately complex data structures, the elements of interest may not
7069 actually be adjacent---for example, if you are interested in the values
7070 of pointers in an array. One useful work-around in this situation is
7071 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7072 Variables}) as a counter in an expression that prints the first
7073 interesting value, and then repeat that expression via @key{RET}. For
7074 instance, suppose you have an array @code{dtab} of pointers to
7075 structures, and you are interested in the values of a field @code{fv}
7076 in each structure. Here is an example of what you might type:
7086 @node Output Formats
7087 @section Output Formats
7089 @cindex formatted output
7090 @cindex output formats
7091 By default, @value{GDBN} prints a value according to its data type. Sometimes
7092 this is not what you want. For example, you might want to print a number
7093 in hex, or a pointer in decimal. Or you might want to view data in memory
7094 at a certain address as a character string or as an instruction. To do
7095 these things, specify an @dfn{output format} when you print a value.
7097 The simplest use of output formats is to say how to print a value
7098 already computed. This is done by starting the arguments of the
7099 @code{print} command with a slash and a format letter. The format
7100 letters supported are:
7104 Regard the bits of the value as an integer, and print the integer in
7108 Print as integer in signed decimal.
7111 Print as integer in unsigned decimal.
7114 Print as integer in octal.
7117 Print as integer in binary. The letter @samp{t} stands for ``two''.
7118 @footnote{@samp{b} cannot be used because these format letters are also
7119 used with the @code{x} command, where @samp{b} stands for ``byte'';
7120 see @ref{Memory,,Examining Memory}.}
7123 @cindex unknown address, locating
7124 @cindex locate address
7125 Print as an address, both absolute in hexadecimal and as an offset from
7126 the nearest preceding symbol. You can use this format used to discover
7127 where (in what function) an unknown address is located:
7130 (@value{GDBP}) p/a 0x54320
7131 $3 = 0x54320 <_initialize_vx+396>
7135 The command @code{info symbol 0x54320} yields similar results.
7136 @xref{Symbols, info symbol}.
7139 Regard as an integer and print it as a character constant. This
7140 prints both the numerical value and its character representation. The
7141 character representation is replaced with the octal escape @samp{\nnn}
7142 for characters outside the 7-bit @sc{ascii} range.
7144 Without this format, @value{GDBN} displays @code{char},
7145 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7146 constants. Single-byte members of vectors are displayed as integer
7150 Regard the bits of the value as a floating point number and print
7151 using typical floating point syntax.
7154 @cindex printing strings
7155 @cindex printing byte arrays
7156 Regard as a string, if possible. With this format, pointers to single-byte
7157 data are displayed as null-terminated strings and arrays of single-byte data
7158 are displayed as fixed-length strings. Other values are displayed in their
7161 Without this format, @value{GDBN} displays pointers to and arrays of
7162 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7163 strings. Single-byte members of a vector are displayed as an integer
7167 @cindex raw printing
7168 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7169 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7170 Printing}). This typically results in a higher-level display of the
7171 value's contents. The @samp{r} format bypasses any Python
7172 pretty-printer which might exist.
7175 For example, to print the program counter in hex (@pxref{Registers}), type
7182 Note that no space is required before the slash; this is because command
7183 names in @value{GDBN} cannot contain a slash.
7185 To reprint the last value in the value history with a different format,
7186 you can use the @code{print} command with just a format and no
7187 expression. For example, @samp{p/x} reprints the last value in hex.
7190 @section Examining Memory
7192 You can use the command @code{x} (for ``examine'') to examine memory in
7193 any of several formats, independently of your program's data types.
7195 @cindex examining memory
7197 @kindex x @r{(examine memory)}
7198 @item x/@var{nfu} @var{addr}
7201 Use the @code{x} command to examine memory.
7204 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7205 much memory to display and how to format it; @var{addr} is an
7206 expression giving the address where you want to start displaying memory.
7207 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7208 Several commands set convenient defaults for @var{addr}.
7211 @item @var{n}, the repeat count
7212 The repeat count is a decimal integer; the default is 1. It specifies
7213 how much memory (counting by units @var{u}) to display.
7214 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7217 @item @var{f}, the display format
7218 The display format is one of the formats used by @code{print}
7219 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7220 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7221 The default is @samp{x} (hexadecimal) initially. The default changes
7222 each time you use either @code{x} or @code{print}.
7224 @item @var{u}, the unit size
7225 The unit size is any of
7231 Halfwords (two bytes).
7233 Words (four bytes). This is the initial default.
7235 Giant words (eight bytes).
7238 Each time you specify a unit size with @code{x}, that size becomes the
7239 default unit the next time you use @code{x}. (For the @samp{s} and
7240 @samp{i} formats, the unit size is ignored and is normally not written.)
7242 @item @var{addr}, starting display address
7243 @var{addr} is the address where you want @value{GDBN} to begin displaying
7244 memory. The expression need not have a pointer value (though it may);
7245 it is always interpreted as an integer address of a byte of memory.
7246 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7247 @var{addr} is usually just after the last address examined---but several
7248 other commands also set the default address: @code{info breakpoints} (to
7249 the address of the last breakpoint listed), @code{info line} (to the
7250 starting address of a line), and @code{print} (if you use it to display
7251 a value from memory).
7254 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7255 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7256 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7257 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7258 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7260 Since the letters indicating unit sizes are all distinct from the
7261 letters specifying output formats, you do not have to remember whether
7262 unit size or format comes first; either order works. The output
7263 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7264 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7266 Even though the unit size @var{u} is ignored for the formats @samp{s}
7267 and @samp{i}, you might still want to use a count @var{n}; for example,
7268 @samp{3i} specifies that you want to see three machine instructions,
7269 including any operands. For convenience, especially when used with
7270 the @code{display} command, the @samp{i} format also prints branch delay
7271 slot instructions, if any, beyond the count specified, which immediately
7272 follow the last instruction that is within the count. The command
7273 @code{disassemble} gives an alternative way of inspecting machine
7274 instructions; see @ref{Machine Code,,Source and Machine Code}.
7276 All the defaults for the arguments to @code{x} are designed to make it
7277 easy to continue scanning memory with minimal specifications each time
7278 you use @code{x}. For example, after you have inspected three machine
7279 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7280 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7281 the repeat count @var{n} is used again; the other arguments default as
7282 for successive uses of @code{x}.
7284 When examining machine instructions, the instruction at current program
7285 counter is shown with a @code{=>} marker. For example:
7288 (@value{GDBP}) x/5i $pc-6
7289 0x804837f <main+11>: mov %esp,%ebp
7290 0x8048381 <main+13>: push %ecx
7291 0x8048382 <main+14>: sub $0x4,%esp
7292 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7293 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7296 @cindex @code{$_}, @code{$__}, and value history
7297 The addresses and contents printed by the @code{x} command are not saved
7298 in the value history because there is often too much of them and they
7299 would get in the way. Instead, @value{GDBN} makes these values available for
7300 subsequent use in expressions as values of the convenience variables
7301 @code{$_} and @code{$__}. After an @code{x} command, the last address
7302 examined is available for use in expressions in the convenience variable
7303 @code{$_}. The contents of that address, as examined, are available in
7304 the convenience variable @code{$__}.
7306 If the @code{x} command has a repeat count, the address and contents saved
7307 are from the last memory unit printed; this is not the same as the last
7308 address printed if several units were printed on the last line of output.
7310 @cindex remote memory comparison
7311 @cindex verify remote memory image
7312 When you are debugging a program running on a remote target machine
7313 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7314 remote machine's memory against the executable file you downloaded to
7315 the target. The @code{compare-sections} command is provided for such
7319 @kindex compare-sections
7320 @item compare-sections @r{[}@var{section-name}@r{]}
7321 Compare the data of a loadable section @var{section-name} in the
7322 executable file of the program being debugged with the same section in
7323 the remote machine's memory, and report any mismatches. With no
7324 arguments, compares all loadable sections. This command's
7325 availability depends on the target's support for the @code{"qCRC"}
7330 @section Automatic Display
7331 @cindex automatic display
7332 @cindex display of expressions
7334 If you find that you want to print the value of an expression frequently
7335 (to see how it changes), you might want to add it to the @dfn{automatic
7336 display list} so that @value{GDBN} prints its value each time your program stops.
7337 Each expression added to the list is given a number to identify it;
7338 to remove an expression from the list, you specify that number.
7339 The automatic display looks like this:
7343 3: bar[5] = (struct hack *) 0x3804
7347 This display shows item numbers, expressions and their current values. As with
7348 displays you request manually using @code{x} or @code{print}, you can
7349 specify the output format you prefer; in fact, @code{display} decides
7350 whether to use @code{print} or @code{x} depending your format
7351 specification---it uses @code{x} if you specify either the @samp{i}
7352 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7356 @item display @var{expr}
7357 Add the expression @var{expr} to the list of expressions to display
7358 each time your program stops. @xref{Expressions, ,Expressions}.
7360 @code{display} does not repeat if you press @key{RET} again after using it.
7362 @item display/@var{fmt} @var{expr}
7363 For @var{fmt} specifying only a display format and not a size or
7364 count, add the expression @var{expr} to the auto-display list but
7365 arrange to display it each time in the specified format @var{fmt}.
7366 @xref{Output Formats,,Output Formats}.
7368 @item display/@var{fmt} @var{addr}
7369 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7370 number of units, add the expression @var{addr} as a memory address to
7371 be examined each time your program stops. Examining means in effect
7372 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7375 For example, @samp{display/i $pc} can be helpful, to see the machine
7376 instruction about to be executed each time execution stops (@samp{$pc}
7377 is a common name for the program counter; @pxref{Registers, ,Registers}).
7380 @kindex delete display
7382 @item undisplay @var{dnums}@dots{}
7383 @itemx delete display @var{dnums}@dots{}
7384 Remove item numbers @var{dnums} from the list of expressions to display.
7386 @code{undisplay} does not repeat if you press @key{RET} after using it.
7387 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7389 @kindex disable display
7390 @item disable display @var{dnums}@dots{}
7391 Disable the display of item numbers @var{dnums}. A disabled display
7392 item is not printed automatically, but is not forgotten. It may be
7393 enabled again later.
7395 @kindex enable display
7396 @item enable display @var{dnums}@dots{}
7397 Enable display of item numbers @var{dnums}. It becomes effective once
7398 again in auto display of its expression, until you specify otherwise.
7401 Display the current values of the expressions on the list, just as is
7402 done when your program stops.
7404 @kindex info display
7406 Print the list of expressions previously set up to display
7407 automatically, each one with its item number, but without showing the
7408 values. This includes disabled expressions, which are marked as such.
7409 It also includes expressions which would not be displayed right now
7410 because they refer to automatic variables not currently available.
7413 @cindex display disabled out of scope
7414 If a display expression refers to local variables, then it does not make
7415 sense outside the lexical context for which it was set up. Such an
7416 expression is disabled when execution enters a context where one of its
7417 variables is not defined. For example, if you give the command
7418 @code{display last_char} while inside a function with an argument
7419 @code{last_char}, @value{GDBN} displays this argument while your program
7420 continues to stop inside that function. When it stops elsewhere---where
7421 there is no variable @code{last_char}---the display is disabled
7422 automatically. The next time your program stops where @code{last_char}
7423 is meaningful, you can enable the display expression once again.
7425 @node Print Settings
7426 @section Print Settings
7428 @cindex format options
7429 @cindex print settings
7430 @value{GDBN} provides the following ways to control how arrays, structures,
7431 and symbols are printed.
7434 These settings are useful for debugging programs in any language:
7438 @item set print address
7439 @itemx set print address on
7440 @cindex print/don't print memory addresses
7441 @value{GDBN} prints memory addresses showing the location of stack
7442 traces, structure values, pointer values, breakpoints, and so forth,
7443 even when it also displays the contents of those addresses. The default
7444 is @code{on}. For example, this is what a stack frame display looks like with
7445 @code{set print address on}:
7450 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7452 530 if (lquote != def_lquote)
7456 @item set print address off
7457 Do not print addresses when displaying their contents. For example,
7458 this is the same stack frame displayed with @code{set print address off}:
7462 (@value{GDBP}) set print addr off
7464 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7465 530 if (lquote != def_lquote)
7469 You can use @samp{set print address off} to eliminate all machine
7470 dependent displays from the @value{GDBN} interface. For example, with
7471 @code{print address off}, you should get the same text for backtraces on
7472 all machines---whether or not they involve pointer arguments.
7475 @item show print address
7476 Show whether or not addresses are to be printed.
7479 When @value{GDBN} prints a symbolic address, it normally prints the
7480 closest earlier symbol plus an offset. If that symbol does not uniquely
7481 identify the address (for example, it is a name whose scope is a single
7482 source file), you may need to clarify. One way to do this is with
7483 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7484 you can set @value{GDBN} to print the source file and line number when
7485 it prints a symbolic address:
7488 @item set print symbol-filename on
7489 @cindex source file and line of a symbol
7490 @cindex symbol, source file and line
7491 Tell @value{GDBN} to print the source file name and line number of a
7492 symbol in the symbolic form of an address.
7494 @item set print symbol-filename off
7495 Do not print source file name and line number of a symbol. This is the
7498 @item show print symbol-filename
7499 Show whether or not @value{GDBN} will print the source file name and
7500 line number of a symbol in the symbolic form of an address.
7503 Another situation where it is helpful to show symbol filenames and line
7504 numbers is when disassembling code; @value{GDBN} shows you the line
7505 number and source file that corresponds to each instruction.
7507 Also, you may wish to see the symbolic form only if the address being
7508 printed is reasonably close to the closest earlier symbol:
7511 @item set print max-symbolic-offset @var{max-offset}
7512 @cindex maximum value for offset of closest symbol
7513 Tell @value{GDBN} to only display the symbolic form of an address if the
7514 offset between the closest earlier symbol and the address is less than
7515 @var{max-offset}. The default is 0, which tells @value{GDBN}
7516 to always print the symbolic form of an address if any symbol precedes it.
7518 @item show print max-symbolic-offset
7519 Ask how large the maximum offset is that @value{GDBN} prints in a
7523 @cindex wild pointer, interpreting
7524 @cindex pointer, finding referent
7525 If you have a pointer and you are not sure where it points, try
7526 @samp{set print symbol-filename on}. Then you can determine the name
7527 and source file location of the variable where it points, using
7528 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7529 For example, here @value{GDBN} shows that a variable @code{ptt} points
7530 at another variable @code{t}, defined in @file{hi2.c}:
7533 (@value{GDBP}) set print symbol-filename on
7534 (@value{GDBP}) p/a ptt
7535 $4 = 0xe008 <t in hi2.c>
7539 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7540 does not show the symbol name and filename of the referent, even with
7541 the appropriate @code{set print} options turned on.
7544 Other settings control how different kinds of objects are printed:
7547 @item set print array
7548 @itemx set print array on
7549 @cindex pretty print arrays
7550 Pretty print arrays. This format is more convenient to read,
7551 but uses more space. The default is off.
7553 @item set print array off
7554 Return to compressed format for arrays.
7556 @item show print array
7557 Show whether compressed or pretty format is selected for displaying
7560 @cindex print array indexes
7561 @item set print array-indexes
7562 @itemx set print array-indexes on
7563 Print the index of each element when displaying arrays. May be more
7564 convenient to locate a given element in the array or quickly find the
7565 index of a given element in that printed array. The default is off.
7567 @item set print array-indexes off
7568 Stop printing element indexes when displaying arrays.
7570 @item show print array-indexes
7571 Show whether the index of each element is printed when displaying
7574 @item set print elements @var{number-of-elements}
7575 @cindex number of array elements to print
7576 @cindex limit on number of printed array elements
7577 Set a limit on how many elements of an array @value{GDBN} will print.
7578 If @value{GDBN} is printing a large array, it stops printing after it has
7579 printed the number of elements set by the @code{set print elements} command.
7580 This limit also applies to the display of strings.
7581 When @value{GDBN} starts, this limit is set to 200.
7582 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7584 @item show print elements
7585 Display the number of elements of a large array that @value{GDBN} will print.
7586 If the number is 0, then the printing is unlimited.
7588 @item set print frame-arguments @var{value}
7589 @kindex set print frame-arguments
7590 @cindex printing frame argument values
7591 @cindex print all frame argument values
7592 @cindex print frame argument values for scalars only
7593 @cindex do not print frame argument values
7594 This command allows to control how the values of arguments are printed
7595 when the debugger prints a frame (@pxref{Frames}). The possible
7600 The values of all arguments are printed.
7603 Print the value of an argument only if it is a scalar. The value of more
7604 complex arguments such as arrays, structures, unions, etc, is replaced
7605 by @code{@dots{}}. This is the default. Here is an example where
7606 only scalar arguments are shown:
7609 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7614 None of the argument values are printed. Instead, the value of each argument
7615 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7618 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7623 By default, only scalar arguments are printed. This command can be used
7624 to configure the debugger to print the value of all arguments, regardless
7625 of their type. However, it is often advantageous to not print the value
7626 of more complex parameters. For instance, it reduces the amount of
7627 information printed in each frame, making the backtrace more readable.
7628 Also, it improves performance when displaying Ada frames, because
7629 the computation of large arguments can sometimes be CPU-intensive,
7630 especially in large applications. Setting @code{print frame-arguments}
7631 to @code{scalars} (the default) or @code{none} avoids this computation,
7632 thus speeding up the display of each Ada frame.
7634 @item show print frame-arguments
7635 Show how the value of arguments should be displayed when printing a frame.
7637 @item set print repeats
7638 @cindex repeated array elements
7639 Set the threshold for suppressing display of repeated array
7640 elements. When the number of consecutive identical elements of an
7641 array exceeds the threshold, @value{GDBN} prints the string
7642 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7643 identical repetitions, instead of displaying the identical elements
7644 themselves. Setting the threshold to zero will cause all elements to
7645 be individually printed. The default threshold is 10.
7647 @item show print repeats
7648 Display the current threshold for printing repeated identical
7651 @item set print null-stop
7652 @cindex @sc{null} elements in arrays
7653 Cause @value{GDBN} to stop printing the characters of an array when the first
7654 @sc{null} is encountered. This is useful when large arrays actually
7655 contain only short strings.
7658 @item show print null-stop
7659 Show whether @value{GDBN} stops printing an array on the first
7660 @sc{null} character.
7662 @item set print pretty on
7663 @cindex print structures in indented form
7664 @cindex indentation in structure display
7665 Cause @value{GDBN} to print structures in an indented format with one member
7666 per line, like this:
7681 @item set print pretty off
7682 Cause @value{GDBN} to print structures in a compact format, like this:
7686 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7687 meat = 0x54 "Pork"@}
7692 This is the default format.
7694 @item show print pretty
7695 Show which format @value{GDBN} is using to print structures.
7697 @item set print sevenbit-strings on
7698 @cindex eight-bit characters in strings
7699 @cindex octal escapes in strings
7700 Print using only seven-bit characters; if this option is set,
7701 @value{GDBN} displays any eight-bit characters (in strings or
7702 character values) using the notation @code{\}@var{nnn}. This setting is
7703 best if you are working in English (@sc{ascii}) and you use the
7704 high-order bit of characters as a marker or ``meta'' bit.
7706 @item set print sevenbit-strings off
7707 Print full eight-bit characters. This allows the use of more
7708 international character sets, and is the default.
7710 @item show print sevenbit-strings
7711 Show whether or not @value{GDBN} is printing only seven-bit characters.
7713 @item set print union on
7714 @cindex unions in structures, printing
7715 Tell @value{GDBN} to print unions which are contained in structures
7716 and other unions. This is the default setting.
7718 @item set print union off
7719 Tell @value{GDBN} not to print unions which are contained in
7720 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7723 @item show print union
7724 Ask @value{GDBN} whether or not it will print unions which are contained in
7725 structures and other unions.
7727 For example, given the declarations
7730 typedef enum @{Tree, Bug@} Species;
7731 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7732 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7743 struct thing foo = @{Tree, @{Acorn@}@};
7747 with @code{set print union on} in effect @samp{p foo} would print
7750 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7754 and with @code{set print union off} in effect it would print
7757 $1 = @{it = Tree, form = @{...@}@}
7761 @code{set print union} affects programs written in C-like languages
7767 These settings are of interest when debugging C@t{++} programs:
7770 @cindex demangling C@t{++} names
7771 @item set print demangle
7772 @itemx set print demangle on
7773 Print C@t{++} names in their source form rather than in the encoded
7774 (``mangled'') form passed to the assembler and linker for type-safe
7775 linkage. The default is on.
7777 @item show print demangle
7778 Show whether C@t{++} names are printed in mangled or demangled form.
7780 @item set print asm-demangle
7781 @itemx set print asm-demangle on
7782 Print C@t{++} names in their source form rather than their mangled form, even
7783 in assembler code printouts such as instruction disassemblies.
7786 @item show print asm-demangle
7787 Show whether C@t{++} names in assembly listings are printed in mangled
7790 @cindex C@t{++} symbol decoding style
7791 @cindex symbol decoding style, C@t{++}
7792 @kindex set demangle-style
7793 @item set demangle-style @var{style}
7794 Choose among several encoding schemes used by different compilers to
7795 represent C@t{++} names. The choices for @var{style} are currently:
7799 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7802 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7803 This is the default.
7806 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7809 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7812 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7813 @strong{Warning:} this setting alone is not sufficient to allow
7814 debugging @code{cfront}-generated executables. @value{GDBN} would
7815 require further enhancement to permit that.
7818 If you omit @var{style}, you will see a list of possible formats.
7820 @item show demangle-style
7821 Display the encoding style currently in use for decoding C@t{++} symbols.
7823 @item set print object
7824 @itemx set print object on
7825 @cindex derived type of an object, printing
7826 @cindex display derived types
7827 When displaying a pointer to an object, identify the @emph{actual}
7828 (derived) type of the object rather than the @emph{declared} type, using
7829 the virtual function table.
7831 @item set print object off
7832 Display only the declared type of objects, without reference to the
7833 virtual function table. This is the default setting.
7835 @item show print object
7836 Show whether actual, or declared, object types are displayed.
7838 @item set print static-members
7839 @itemx set print static-members on
7840 @cindex static members of C@t{++} objects
7841 Print static members when displaying a C@t{++} object. The default is on.
7843 @item set print static-members off
7844 Do not print static members when displaying a C@t{++} object.
7846 @item show print static-members
7847 Show whether C@t{++} static members are printed or not.
7849 @item set print pascal_static-members
7850 @itemx set print pascal_static-members on
7851 @cindex static members of Pascal objects
7852 @cindex Pascal objects, static members display
7853 Print static members when displaying a Pascal object. The default is on.
7855 @item set print pascal_static-members off
7856 Do not print static members when displaying a Pascal object.
7858 @item show print pascal_static-members
7859 Show whether Pascal static members are printed or not.
7861 @c These don't work with HP ANSI C++ yet.
7862 @item set print vtbl
7863 @itemx set print vtbl on
7864 @cindex pretty print C@t{++} virtual function tables
7865 @cindex virtual functions (C@t{++}) display
7866 @cindex VTBL display
7867 Pretty print C@t{++} virtual function tables. The default is off.
7868 (The @code{vtbl} commands do not work on programs compiled with the HP
7869 ANSI C@t{++} compiler (@code{aCC}).)
7871 @item set print vtbl off
7872 Do not pretty print C@t{++} virtual function tables.
7874 @item show print vtbl
7875 Show whether C@t{++} virtual function tables are pretty printed, or not.
7879 @section Value History
7881 @cindex value history
7882 @cindex history of values printed by @value{GDBN}
7883 Values printed by the @code{print} command are saved in the @value{GDBN}
7884 @dfn{value history}. This allows you to refer to them in other expressions.
7885 Values are kept until the symbol table is re-read or discarded
7886 (for example with the @code{file} or @code{symbol-file} commands).
7887 When the symbol table changes, the value history is discarded,
7888 since the values may contain pointers back to the types defined in the
7893 @cindex history number
7894 The values printed are given @dfn{history numbers} by which you can
7895 refer to them. These are successive integers starting with one.
7896 @code{print} shows you the history number assigned to a value by
7897 printing @samp{$@var{num} = } before the value; here @var{num} is the
7900 To refer to any previous value, use @samp{$} followed by the value's
7901 history number. The way @code{print} labels its output is designed to
7902 remind you of this. Just @code{$} refers to the most recent value in
7903 the history, and @code{$$} refers to the value before that.
7904 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7905 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7906 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7908 For example, suppose you have just printed a pointer to a structure and
7909 want to see the contents of the structure. It suffices to type
7915 If you have a chain of structures where the component @code{next} points
7916 to the next one, you can print the contents of the next one with this:
7923 You can print successive links in the chain by repeating this
7924 command---which you can do by just typing @key{RET}.
7926 Note that the history records values, not expressions. If the value of
7927 @code{x} is 4 and you type these commands:
7935 then the value recorded in the value history by the @code{print} command
7936 remains 4 even though the value of @code{x} has changed.
7941 Print the last ten values in the value history, with their item numbers.
7942 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7943 values} does not change the history.
7945 @item show values @var{n}
7946 Print ten history values centered on history item number @var{n}.
7949 Print ten history values just after the values last printed. If no more
7950 values are available, @code{show values +} produces no display.
7953 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7954 same effect as @samp{show values +}.
7956 @node Convenience Vars
7957 @section Convenience Variables
7959 @cindex convenience variables
7960 @cindex user-defined variables
7961 @value{GDBN} provides @dfn{convenience variables} that you can use within
7962 @value{GDBN} to hold on to a value and refer to it later. These variables
7963 exist entirely within @value{GDBN}; they are not part of your program, and
7964 setting a convenience variable has no direct effect on further execution
7965 of your program. That is why you can use them freely.
7967 Convenience variables are prefixed with @samp{$}. Any name preceded by
7968 @samp{$} can be used for a convenience variable, unless it is one of
7969 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7970 (Value history references, in contrast, are @emph{numbers} preceded
7971 by @samp{$}. @xref{Value History, ,Value History}.)
7973 You can save a value in a convenience variable with an assignment
7974 expression, just as you would set a variable in your program.
7978 set $foo = *object_ptr
7982 would save in @code{$foo} the value contained in the object pointed to by
7985 Using a convenience variable for the first time creates it, but its
7986 value is @code{void} until you assign a new value. You can alter the
7987 value with another assignment at any time.
7989 Convenience variables have no fixed types. You can assign a convenience
7990 variable any type of value, including structures and arrays, even if
7991 that variable already has a value of a different type. The convenience
7992 variable, when used as an expression, has the type of its current value.
7995 @kindex show convenience
7996 @cindex show all user variables
7997 @item show convenience
7998 Print a list of convenience variables used so far, and their values.
7999 Abbreviated @code{show conv}.
8001 @kindex init-if-undefined
8002 @cindex convenience variables, initializing
8003 @item init-if-undefined $@var{variable} = @var{expression}
8004 Set a convenience variable if it has not already been set. This is useful
8005 for user-defined commands that keep some state. It is similar, in concept,
8006 to using local static variables with initializers in C (except that
8007 convenience variables are global). It can also be used to allow users to
8008 override default values used in a command script.
8010 If the variable is already defined then the expression is not evaluated so
8011 any side-effects do not occur.
8014 One of the ways to use a convenience variable is as a counter to be
8015 incremented or a pointer to be advanced. For example, to print
8016 a field from successive elements of an array of structures:
8020 print bar[$i++]->contents
8024 Repeat that command by typing @key{RET}.
8026 Some convenience variables are created automatically by @value{GDBN} and given
8027 values likely to be useful.
8030 @vindex $_@r{, convenience variable}
8032 The variable @code{$_} is automatically set by the @code{x} command to
8033 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8034 commands which provide a default address for @code{x} to examine also
8035 set @code{$_} to that address; these commands include @code{info line}
8036 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8037 except when set by the @code{x} command, in which case it is a pointer
8038 to the type of @code{$__}.
8040 @vindex $__@r{, convenience variable}
8042 The variable @code{$__} is automatically set by the @code{x} command
8043 to the value found in the last address examined. Its type is chosen
8044 to match the format in which the data was printed.
8047 @vindex $_exitcode@r{, convenience variable}
8048 The variable @code{$_exitcode} is automatically set to the exit code when
8049 the program being debugged terminates.
8052 @vindex $_siginfo@r{, convenience variable}
8053 The variable @code{$_siginfo} contains extra signal information
8054 (@pxref{extra signal information}). Note that @code{$_siginfo}
8055 could be empty, if the application has not yet received any signals.
8056 For example, it will be empty before you execute the @code{run} command.
8059 On HP-UX systems, if you refer to a function or variable name that
8060 begins with a dollar sign, @value{GDBN} searches for a user or system
8061 name first, before it searches for a convenience variable.
8063 @cindex convenience functions
8064 @value{GDBN} also supplies some @dfn{convenience functions}. These
8065 have a syntax similar to convenience variables. A convenience
8066 function can be used in an expression just like an ordinary function;
8067 however, a convenience function is implemented internally to
8072 @kindex help function
8073 @cindex show all convenience functions
8074 Print a list of all convenience functions.
8081 You can refer to machine register contents, in expressions, as variables
8082 with names starting with @samp{$}. The names of registers are different
8083 for each machine; use @code{info registers} to see the names used on
8087 @kindex info registers
8088 @item info registers
8089 Print the names and values of all registers except floating-point
8090 and vector registers (in the selected stack frame).
8092 @kindex info all-registers
8093 @cindex floating point registers
8094 @item info all-registers
8095 Print the names and values of all registers, including floating-point
8096 and vector registers (in the selected stack frame).
8098 @item info registers @var{regname} @dots{}
8099 Print the @dfn{relativized} value of each specified register @var{regname}.
8100 As discussed in detail below, register values are normally relative to
8101 the selected stack frame. @var{regname} may be any register name valid on
8102 the machine you are using, with or without the initial @samp{$}.
8105 @cindex stack pointer register
8106 @cindex program counter register
8107 @cindex process status register
8108 @cindex frame pointer register
8109 @cindex standard registers
8110 @value{GDBN} has four ``standard'' register names that are available (in
8111 expressions) on most machines---whenever they do not conflict with an
8112 architecture's canonical mnemonics for registers. The register names
8113 @code{$pc} and @code{$sp} are used for the program counter register and
8114 the stack pointer. @code{$fp} is used for a register that contains a
8115 pointer to the current stack frame, and @code{$ps} is used for a
8116 register that contains the processor status. For example,
8117 you could print the program counter in hex with
8124 or print the instruction to be executed next with
8131 or add four to the stack pointer@footnote{This is a way of removing
8132 one word from the stack, on machines where stacks grow downward in
8133 memory (most machines, nowadays). This assumes that the innermost
8134 stack frame is selected; setting @code{$sp} is not allowed when other
8135 stack frames are selected. To pop entire frames off the stack,
8136 regardless of machine architecture, use @code{return};
8137 see @ref{Returning, ,Returning from a Function}.} with
8143 Whenever possible, these four standard register names are available on
8144 your machine even though the machine has different canonical mnemonics,
8145 so long as there is no conflict. The @code{info registers} command
8146 shows the canonical names. For example, on the SPARC, @code{info
8147 registers} displays the processor status register as @code{$psr} but you
8148 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8149 is an alias for the @sc{eflags} register.
8151 @value{GDBN} always considers the contents of an ordinary register as an
8152 integer when the register is examined in this way. Some machines have
8153 special registers which can hold nothing but floating point; these
8154 registers are considered to have floating point values. There is no way
8155 to refer to the contents of an ordinary register as floating point value
8156 (although you can @emph{print} it as a floating point value with
8157 @samp{print/f $@var{regname}}).
8159 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8160 means that the data format in which the register contents are saved by
8161 the operating system is not the same one that your program normally
8162 sees. For example, the registers of the 68881 floating point
8163 coprocessor are always saved in ``extended'' (raw) format, but all C
8164 programs expect to work with ``double'' (virtual) format. In such
8165 cases, @value{GDBN} normally works with the virtual format only (the format
8166 that makes sense for your program), but the @code{info registers} command
8167 prints the data in both formats.
8169 @cindex SSE registers (x86)
8170 @cindex MMX registers (x86)
8171 Some machines have special registers whose contents can be interpreted
8172 in several different ways. For example, modern x86-based machines
8173 have SSE and MMX registers that can hold several values packed
8174 together in several different formats. @value{GDBN} refers to such
8175 registers in @code{struct} notation:
8178 (@value{GDBP}) print $xmm1
8180 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8181 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8182 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8183 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8184 v4_int32 = @{0, 20657912, 11, 13@},
8185 v2_int64 = @{88725056443645952, 55834574859@},
8186 uint128 = 0x0000000d0000000b013b36f800000000
8191 To set values of such registers, you need to tell @value{GDBN} which
8192 view of the register you wish to change, as if you were assigning
8193 value to a @code{struct} member:
8196 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8199 Normally, register values are relative to the selected stack frame
8200 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8201 value that the register would contain if all stack frames farther in
8202 were exited and their saved registers restored. In order to see the
8203 true contents of hardware registers, you must select the innermost
8204 frame (with @samp{frame 0}).
8206 However, @value{GDBN} must deduce where registers are saved, from the machine
8207 code generated by your compiler. If some registers are not saved, or if
8208 @value{GDBN} is unable to locate the saved registers, the selected stack
8209 frame makes no difference.
8211 @node Floating Point Hardware
8212 @section Floating Point Hardware
8213 @cindex floating point
8215 Depending on the configuration, @value{GDBN} may be able to give
8216 you more information about the status of the floating point hardware.
8221 Display hardware-dependent information about the floating
8222 point unit. The exact contents and layout vary depending on the
8223 floating point chip. Currently, @samp{info float} is supported on
8224 the ARM and x86 machines.
8228 @section Vector Unit
8231 Depending on the configuration, @value{GDBN} may be able to give you
8232 more information about the status of the vector unit.
8237 Display information about the vector unit. The exact contents and
8238 layout vary depending on the hardware.
8241 @node OS Information
8242 @section Operating System Auxiliary Information
8243 @cindex OS information
8245 @value{GDBN} provides interfaces to useful OS facilities that can help
8246 you debug your program.
8248 @cindex @code{ptrace} system call
8249 @cindex @code{struct user} contents
8250 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8251 machines), it interfaces with the inferior via the @code{ptrace}
8252 system call. The operating system creates a special sata structure,
8253 called @code{struct user}, for this interface. You can use the
8254 command @code{info udot} to display the contents of this data
8260 Display the contents of the @code{struct user} maintained by the OS
8261 kernel for the program being debugged. @value{GDBN} displays the
8262 contents of @code{struct user} as a list of hex numbers, similar to
8263 the @code{examine} command.
8266 @cindex auxiliary vector
8267 @cindex vector, auxiliary
8268 Some operating systems supply an @dfn{auxiliary vector} to programs at
8269 startup. This is akin to the arguments and environment that you
8270 specify for a program, but contains a system-dependent variety of
8271 binary values that tell system libraries important details about the
8272 hardware, operating system, and process. Each value's purpose is
8273 identified by an integer tag; the meanings are well-known but system-specific.
8274 Depending on the configuration and operating system facilities,
8275 @value{GDBN} may be able to show you this information. For remote
8276 targets, this functionality may further depend on the remote stub's
8277 support of the @samp{qXfer:auxv:read} packet, see
8278 @ref{qXfer auxiliary vector read}.
8283 Display the auxiliary vector of the inferior, which can be either a
8284 live process or a core dump file. @value{GDBN} prints each tag value
8285 numerically, and also shows names and text descriptions for recognized
8286 tags. Some values in the vector are numbers, some bit masks, and some
8287 pointers to strings or other data. @value{GDBN} displays each value in the
8288 most appropriate form for a recognized tag, and in hexadecimal for
8289 an unrecognized tag.
8292 On some targets, @value{GDBN} can access operating-system-specific information
8293 and display it to user, without interpretation. For remote targets,
8294 this functionality depends on the remote stub's support of the
8295 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8298 @kindex info os processes
8299 @item info os processes
8300 Display the list of processes on the target. For each process,
8301 @value{GDBN} prints the process identifier, the name of the user, and
8302 the command corresponding to the process.
8305 @node Memory Region Attributes
8306 @section Memory Region Attributes
8307 @cindex memory region attributes
8309 @dfn{Memory region attributes} allow you to describe special handling
8310 required by regions of your target's memory. @value{GDBN} uses
8311 attributes to determine whether to allow certain types of memory
8312 accesses; whether to use specific width accesses; and whether to cache
8313 target memory. By default the description of memory regions is
8314 fetched from the target (if the current target supports this), but the
8315 user can override the fetched regions.
8317 Defined memory regions can be individually enabled and disabled. When a
8318 memory region is disabled, @value{GDBN} uses the default attributes when
8319 accessing memory in that region. Similarly, if no memory regions have
8320 been defined, @value{GDBN} uses the default attributes when accessing
8323 When a memory region is defined, it is given a number to identify it;
8324 to enable, disable, or remove a memory region, you specify that number.
8328 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8329 Define a memory region bounded by @var{lower} and @var{upper} with
8330 attributes @var{attributes}@dots{}, and add it to the list of regions
8331 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8332 case: it is treated as the target's maximum memory address.
8333 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8336 Discard any user changes to the memory regions and use target-supplied
8337 regions, if available, or no regions if the target does not support.
8340 @item delete mem @var{nums}@dots{}
8341 Remove memory regions @var{nums}@dots{} from the list of regions
8342 monitored by @value{GDBN}.
8345 @item disable mem @var{nums}@dots{}
8346 Disable monitoring of memory regions @var{nums}@dots{}.
8347 A disabled memory region is not forgotten.
8348 It may be enabled again later.
8351 @item enable mem @var{nums}@dots{}
8352 Enable monitoring of memory regions @var{nums}@dots{}.
8356 Print a table of all defined memory regions, with the following columns
8360 @item Memory Region Number
8361 @item Enabled or Disabled.
8362 Enabled memory regions are marked with @samp{y}.
8363 Disabled memory regions are marked with @samp{n}.
8366 The address defining the inclusive lower bound of the memory region.
8369 The address defining the exclusive upper bound of the memory region.
8372 The list of attributes set for this memory region.
8377 @subsection Attributes
8379 @subsubsection Memory Access Mode
8380 The access mode attributes set whether @value{GDBN} may make read or
8381 write accesses to a memory region.
8383 While these attributes prevent @value{GDBN} from performing invalid
8384 memory accesses, they do nothing to prevent the target system, I/O DMA,
8385 etc.@: from accessing memory.
8389 Memory is read only.
8391 Memory is write only.
8393 Memory is read/write. This is the default.
8396 @subsubsection Memory Access Size
8397 The access size attribute tells @value{GDBN} to use specific sized
8398 accesses in the memory region. Often memory mapped device registers
8399 require specific sized accesses. If no access size attribute is
8400 specified, @value{GDBN} may use accesses of any size.
8404 Use 8 bit memory accesses.
8406 Use 16 bit memory accesses.
8408 Use 32 bit memory accesses.
8410 Use 64 bit memory accesses.
8413 @c @subsubsection Hardware/Software Breakpoints
8414 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8415 @c will use hardware or software breakpoints for the internal breakpoints
8416 @c used by the step, next, finish, until, etc. commands.
8420 @c Always use hardware breakpoints
8421 @c @item swbreak (default)
8424 @subsubsection Data Cache
8425 The data cache attributes set whether @value{GDBN} will cache target
8426 memory. While this generally improves performance by reducing debug
8427 protocol overhead, it can lead to incorrect results because @value{GDBN}
8428 does not know about volatile variables or memory mapped device
8433 Enable @value{GDBN} to cache target memory.
8435 Disable @value{GDBN} from caching target memory. This is the default.
8438 @subsection Memory Access Checking
8439 @value{GDBN} can be instructed to refuse accesses to memory that is
8440 not explicitly described. This can be useful if accessing such
8441 regions has undesired effects for a specific target, or to provide
8442 better error checking. The following commands control this behaviour.
8445 @kindex set mem inaccessible-by-default
8446 @item set mem inaccessible-by-default [on|off]
8447 If @code{on} is specified, make @value{GDBN} treat memory not
8448 explicitly described by the memory ranges as non-existent and refuse accesses
8449 to such memory. The checks are only performed if there's at least one
8450 memory range defined. If @code{off} is specified, make @value{GDBN}
8451 treat the memory not explicitly described by the memory ranges as RAM.
8452 The default value is @code{on}.
8453 @kindex show mem inaccessible-by-default
8454 @item show mem inaccessible-by-default
8455 Show the current handling of accesses to unknown memory.
8459 @c @subsubsection Memory Write Verification
8460 @c The memory write verification attributes set whether @value{GDBN}
8461 @c will re-reads data after each write to verify the write was successful.
8465 @c @item noverify (default)
8468 @node Dump/Restore Files
8469 @section Copy Between Memory and a File
8470 @cindex dump/restore files
8471 @cindex append data to a file
8472 @cindex dump data to a file
8473 @cindex restore data from a file
8475 You can use the commands @code{dump}, @code{append}, and
8476 @code{restore} to copy data between target memory and a file. The
8477 @code{dump} and @code{append} commands write data to a file, and the
8478 @code{restore} command reads data from a file back into the inferior's
8479 memory. Files may be in binary, Motorola S-record, Intel hex, or
8480 Tektronix Hex format; however, @value{GDBN} can only append to binary
8486 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8487 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8488 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8489 or the value of @var{expr}, to @var{filename} in the given format.
8491 The @var{format} parameter may be any one of:
8498 Motorola S-record format.
8500 Tektronix Hex format.
8503 @value{GDBN} uses the same definitions of these formats as the
8504 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8505 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8509 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8510 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8511 Append the contents of memory from @var{start_addr} to @var{end_addr},
8512 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8513 (@value{GDBN} can only append data to files in raw binary form.)
8516 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8517 Restore the contents of file @var{filename} into memory. The
8518 @code{restore} command can automatically recognize any known @sc{bfd}
8519 file format, except for raw binary. To restore a raw binary file you
8520 must specify the optional keyword @code{binary} after the filename.
8522 If @var{bias} is non-zero, its value will be added to the addresses
8523 contained in the file. Binary files always start at address zero, so
8524 they will be restored at address @var{bias}. Other bfd files have
8525 a built-in location; they will be restored at offset @var{bias}
8528 If @var{start} and/or @var{end} are non-zero, then only data between
8529 file offset @var{start} and file offset @var{end} will be restored.
8530 These offsets are relative to the addresses in the file, before
8531 the @var{bias} argument is applied.
8535 @node Core File Generation
8536 @section How to Produce a Core File from Your Program
8537 @cindex dump core from inferior
8539 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8540 image of a running process and its process status (register values
8541 etc.). Its primary use is post-mortem debugging of a program that
8542 crashed while it ran outside a debugger. A program that crashes
8543 automatically produces a core file, unless this feature is disabled by
8544 the user. @xref{Files}, for information on invoking @value{GDBN} in
8545 the post-mortem debugging mode.
8547 Occasionally, you may wish to produce a core file of the program you
8548 are debugging in order to preserve a snapshot of its state.
8549 @value{GDBN} has a special command for that.
8553 @kindex generate-core-file
8554 @item generate-core-file [@var{file}]
8555 @itemx gcore [@var{file}]
8556 Produce a core dump of the inferior process. The optional argument
8557 @var{file} specifies the file name where to put the core dump. If not
8558 specified, the file name defaults to @file{core.@var{pid}}, where
8559 @var{pid} is the inferior process ID.
8561 Note that this command is implemented only for some systems (as of
8562 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8565 @node Character Sets
8566 @section Character Sets
8567 @cindex character sets
8569 @cindex translating between character sets
8570 @cindex host character set
8571 @cindex target character set
8573 If the program you are debugging uses a different character set to
8574 represent characters and strings than the one @value{GDBN} uses itself,
8575 @value{GDBN} can automatically translate between the character sets for
8576 you. The character set @value{GDBN} uses we call the @dfn{host
8577 character set}; the one the inferior program uses we call the
8578 @dfn{target character set}.
8580 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8581 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8582 remote protocol (@pxref{Remote Debugging}) to debug a program
8583 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8584 then the host character set is Latin-1, and the target character set is
8585 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8586 target-charset EBCDIC-US}, then @value{GDBN} translates between
8587 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8588 character and string literals in expressions.
8590 @value{GDBN} has no way to automatically recognize which character set
8591 the inferior program uses; you must tell it, using the @code{set
8592 target-charset} command, described below.
8594 Here are the commands for controlling @value{GDBN}'s character set
8598 @item set target-charset @var{charset}
8599 @kindex set target-charset
8600 Set the current target character set to @var{charset}. To display the
8601 list of supported target character sets, type
8602 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8604 @item set host-charset @var{charset}
8605 @kindex set host-charset
8606 Set the current host character set to @var{charset}.
8608 By default, @value{GDBN} uses a host character set appropriate to the
8609 system it is running on; you can override that default using the
8610 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8611 automatically determine the appropriate host character set. In this
8612 case, @value{GDBN} uses @samp{UTF-8}.
8614 @value{GDBN} can only use certain character sets as its host character
8615 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8616 @value{GDBN} will list the host character sets it supports.
8618 @item set charset @var{charset}
8620 Set the current host and target character sets to @var{charset}. As
8621 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8622 @value{GDBN} will list the names of the character sets that can be used
8623 for both host and target.
8626 @kindex show charset
8627 Show the names of the current host and target character sets.
8629 @item show host-charset
8630 @kindex show host-charset
8631 Show the name of the current host character set.
8633 @item show target-charset
8634 @kindex show target-charset
8635 Show the name of the current target character set.
8637 @item set target-wide-charset @var{charset}
8638 @kindex set target-wide-charset
8639 Set the current target's wide character set to @var{charset}. This is
8640 the character set used by the target's @code{wchar_t} type. To
8641 display the list of supported wide character sets, type
8642 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8644 @item show target-wide-charset
8645 @kindex show target-wide-charset
8646 Show the name of the current target's wide character set.
8649 Here is an example of @value{GDBN}'s character set support in action.
8650 Assume that the following source code has been placed in the file
8651 @file{charset-test.c}:
8657 = @{72, 101, 108, 108, 111, 44, 32, 119,
8658 111, 114, 108, 100, 33, 10, 0@};
8659 char ibm1047_hello[]
8660 = @{200, 133, 147, 147, 150, 107, 64, 166,
8661 150, 153, 147, 132, 90, 37, 0@};
8665 printf ("Hello, world!\n");
8669 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8670 containing the string @samp{Hello, world!} followed by a newline,
8671 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8673 We compile the program, and invoke the debugger on it:
8676 $ gcc -g charset-test.c -o charset-test
8677 $ gdb -nw charset-test
8678 GNU gdb 2001-12-19-cvs
8679 Copyright 2001 Free Software Foundation, Inc.
8684 We can use the @code{show charset} command to see what character sets
8685 @value{GDBN} is currently using to interpret and display characters and
8689 (@value{GDBP}) show charset
8690 The current host and target character set is `ISO-8859-1'.
8694 For the sake of printing this manual, let's use @sc{ascii} as our
8695 initial character set:
8697 (@value{GDBP}) set charset ASCII
8698 (@value{GDBP}) show charset
8699 The current host and target character set is `ASCII'.
8703 Let's assume that @sc{ascii} is indeed the correct character set for our
8704 host system --- in other words, let's assume that if @value{GDBN} prints
8705 characters using the @sc{ascii} character set, our terminal will display
8706 them properly. Since our current target character set is also
8707 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8710 (@value{GDBP}) print ascii_hello
8711 $1 = 0x401698 "Hello, world!\n"
8712 (@value{GDBP}) print ascii_hello[0]
8717 @value{GDBN} uses the target character set for character and string
8718 literals you use in expressions:
8721 (@value{GDBP}) print '+'
8726 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8729 @value{GDBN} relies on the user to tell it which character set the
8730 target program uses. If we print @code{ibm1047_hello} while our target
8731 character set is still @sc{ascii}, we get jibberish:
8734 (@value{GDBP}) print ibm1047_hello
8735 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8736 (@value{GDBP}) print ibm1047_hello[0]
8741 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8742 @value{GDBN} tells us the character sets it supports:
8745 (@value{GDBP}) set target-charset
8746 ASCII EBCDIC-US IBM1047 ISO-8859-1
8747 (@value{GDBP}) set target-charset
8750 We can select @sc{ibm1047} as our target character set, and examine the
8751 program's strings again. Now the @sc{ascii} string is wrong, but
8752 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8753 target character set, @sc{ibm1047}, to the host character set,
8754 @sc{ascii}, and they display correctly:
8757 (@value{GDBP}) set target-charset IBM1047
8758 (@value{GDBP}) show charset
8759 The current host character set is `ASCII'.
8760 The current target character set is `IBM1047'.
8761 (@value{GDBP}) print ascii_hello
8762 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8763 (@value{GDBP}) print ascii_hello[0]
8765 (@value{GDBP}) print ibm1047_hello
8766 $8 = 0x4016a8 "Hello, world!\n"
8767 (@value{GDBP}) print ibm1047_hello[0]
8772 As above, @value{GDBN} uses the target character set for character and
8773 string literals you use in expressions:
8776 (@value{GDBP}) print '+'
8781 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8784 @node Caching Remote Data
8785 @section Caching Data of Remote Targets
8786 @cindex caching data of remote targets
8788 @value{GDBN} caches data exchanged between the debugger and a
8789 remote target (@pxref{Remote Debugging}). Such caching generally improves
8790 performance, because it reduces the overhead of the remote protocol by
8791 bundling memory reads and writes into large chunks. Unfortunately, simply
8792 caching everything would lead to incorrect results, since @value{GDBN}
8793 does not necessarily know anything about volatile values, memory-mapped I/O
8794 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
8795 memory can be changed @emph{while} a gdb command is executing.
8796 Therefore, by default, @value{GDBN} only caches data
8797 known to be on the stack@footnote{In non-stop mode, it is moderately
8798 rare for a running thread to modify the stack of a stopped thread
8799 in a way that would interfere with a backtrace, and caching of
8800 stack reads provides a significant speed up of remote backtraces.}.
8801 Other regions of memory can be explicitly marked as
8802 cacheable; see @pxref{Memory Region Attributes}.
8805 @kindex set remotecache
8806 @item set remotecache on
8807 @itemx set remotecache off
8808 This option no longer does anything; it exists for compatibility
8811 @kindex show remotecache
8812 @item show remotecache
8813 Show the current state of the obsolete remotecache flag.
8815 @kindex set stack-cache
8816 @item set stack-cache on
8817 @itemx set stack-cache off
8818 Enable or disable caching of stack accesses. When @code{ON}, use
8819 caching. By default, this option is @code{ON}.
8821 @kindex show stack-cache
8822 @item show stack-cache
8823 Show the current state of data caching for memory accesses.
8826 @item info dcache @r{[}line@r{]}
8827 Print the information about the data cache performance. The
8828 information displayed includes the dcache width and depth, and for
8829 each cache line, its number, address, and how many times it was
8830 referenced. This command is useful for debugging the data cache
8833 If a line number is specified, the contents of that line will be
8837 @node Searching Memory
8838 @section Search Memory
8839 @cindex searching memory
8841 Memory can be searched for a particular sequence of bytes with the
8842 @code{find} command.
8846 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8847 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8848 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8849 etc. The search begins at address @var{start_addr} and continues for either
8850 @var{len} bytes or through to @var{end_addr} inclusive.
8853 @var{s} and @var{n} are optional parameters.
8854 They may be specified in either order, apart or together.
8857 @item @var{s}, search query size
8858 The size of each search query value.
8864 halfwords (two bytes)
8868 giant words (eight bytes)
8871 All values are interpreted in the current language.
8872 This means, for example, that if the current source language is C/C@t{++}
8873 then searching for the string ``hello'' includes the trailing '\0'.
8875 If the value size is not specified, it is taken from the
8876 value's type in the current language.
8877 This is useful when one wants to specify the search
8878 pattern as a mixture of types.
8879 Note that this means, for example, that in the case of C-like languages
8880 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8881 which is typically four bytes.
8883 @item @var{n}, maximum number of finds
8884 The maximum number of matches to print. The default is to print all finds.
8887 You can use strings as search values. Quote them with double-quotes
8889 The string value is copied into the search pattern byte by byte,
8890 regardless of the endianness of the target and the size specification.
8892 The address of each match found is printed as well as a count of the
8893 number of matches found.
8895 The address of the last value found is stored in convenience variable
8897 A count of the number of matches is stored in @samp{$numfound}.
8899 For example, if stopped at the @code{printf} in this function:
8905 static char hello[] = "hello-hello";
8906 static struct @{ char c; short s; int i; @}
8907 __attribute__ ((packed)) mixed
8908 = @{ 'c', 0x1234, 0x87654321 @};
8909 printf ("%s\n", hello);
8914 you get during debugging:
8917 (gdb) find &hello[0], +sizeof(hello), "hello"
8918 0x804956d <hello.1620+6>
8920 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8921 0x8049567 <hello.1620>
8922 0x804956d <hello.1620+6>
8924 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8925 0x8049567 <hello.1620>
8927 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8928 0x8049560 <mixed.1625>
8930 (gdb) print $numfound
8933 $2 = (void *) 0x8049560
8936 @node Optimized Code
8937 @chapter Debugging Optimized Code
8938 @cindex optimized code, debugging
8939 @cindex debugging optimized code
8941 Almost all compilers support optimization. With optimization
8942 disabled, the compiler generates assembly code that corresponds
8943 directly to your source code, in a simplistic way. As the compiler
8944 applies more powerful optimizations, the generated assembly code
8945 diverges from your original source code. With help from debugging
8946 information generated by the compiler, @value{GDBN} can map from
8947 the running program back to constructs from your original source.
8949 @value{GDBN} is more accurate with optimization disabled. If you
8950 can recompile without optimization, it is easier to follow the
8951 progress of your program during debugging. But, there are many cases
8952 where you may need to debug an optimized version.
8954 When you debug a program compiled with @samp{-g -O}, remember that the
8955 optimizer has rearranged your code; the debugger shows you what is
8956 really there. Do not be too surprised when the execution path does not
8957 exactly match your source file! An extreme example: if you define a
8958 variable, but never use it, @value{GDBN} never sees that
8959 variable---because the compiler optimizes it out of existence.
8961 Some things do not work as well with @samp{-g -O} as with just
8962 @samp{-g}, particularly on machines with instruction scheduling. If in
8963 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
8964 please report it to us as a bug (including a test case!).
8965 @xref{Variables}, for more information about debugging optimized code.
8968 * Inline Functions:: How @value{GDBN} presents inlining
8971 @node Inline Functions
8972 @section Inline Functions
8973 @cindex inline functions, debugging
8975 @dfn{Inlining} is an optimization that inserts a copy of the function
8976 body directly at each call site, instead of jumping to a shared
8977 routine. @value{GDBN} displays inlined functions just like
8978 non-inlined functions. They appear in backtraces. You can view their
8979 arguments and local variables, step into them with @code{step}, skip
8980 them with @code{next}, and escape from them with @code{finish}.
8981 You can check whether a function was inlined by using the
8982 @code{info frame} command.
8984 For @value{GDBN} to support inlined functions, the compiler must
8985 record information about inlining in the debug information ---
8986 @value{NGCC} using the @sc{dwarf 2} format does this, and several
8987 other compilers do also. @value{GDBN} only supports inlined functions
8988 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
8989 do not emit two required attributes (@samp{DW_AT_call_file} and
8990 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
8991 function calls with earlier versions of @value{NGCC}. It instead
8992 displays the arguments and local variables of inlined functions as
8993 local variables in the caller.
8995 The body of an inlined function is directly included at its call site;
8996 unlike a non-inlined function, there are no instructions devoted to
8997 the call. @value{GDBN} still pretends that the call site and the
8998 start of the inlined function are different instructions. Stepping to
8999 the call site shows the call site, and then stepping again shows
9000 the first line of the inlined function, even though no additional
9001 instructions are executed.
9003 This makes source-level debugging much clearer; you can see both the
9004 context of the call and then the effect of the call. Only stepping by
9005 a single instruction using @code{stepi} or @code{nexti} does not do
9006 this; single instruction steps always show the inlined body.
9008 There are some ways that @value{GDBN} does not pretend that inlined
9009 function calls are the same as normal calls:
9013 You cannot set breakpoints on inlined functions. @value{GDBN}
9014 either reports that there is no symbol with that name, or else sets the
9015 breakpoint only on non-inlined copies of the function. This limitation
9016 will be removed in a future version of @value{GDBN}; until then,
9017 set a breakpoint by line number on the first line of the inlined
9021 Setting breakpoints at the call site of an inlined function may not
9022 work, because the call site does not contain any code. @value{GDBN}
9023 may incorrectly move the breakpoint to the next line of the enclosing
9024 function, after the call. This limitation will be removed in a future
9025 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9026 or inside the inlined function instead.
9029 @value{GDBN} cannot locate the return value of inlined calls after
9030 using the @code{finish} command. This is a limitation of compiler-generated
9031 debugging information; after @code{finish}, you can step to the next line
9032 and print a variable where your program stored the return value.
9038 @chapter C Preprocessor Macros
9040 Some languages, such as C and C@t{++}, provide a way to define and invoke
9041 ``preprocessor macros'' which expand into strings of tokens.
9042 @value{GDBN} can evaluate expressions containing macro invocations, show
9043 the result of macro expansion, and show a macro's definition, including
9044 where it was defined.
9046 You may need to compile your program specially to provide @value{GDBN}
9047 with information about preprocessor macros. Most compilers do not
9048 include macros in their debugging information, even when you compile
9049 with the @option{-g} flag. @xref{Compilation}.
9051 A program may define a macro at one point, remove that definition later,
9052 and then provide a different definition after that. Thus, at different
9053 points in the program, a macro may have different definitions, or have
9054 no definition at all. If there is a current stack frame, @value{GDBN}
9055 uses the macros in scope at that frame's source code line. Otherwise,
9056 @value{GDBN} uses the macros in scope at the current listing location;
9059 Whenever @value{GDBN} evaluates an expression, it always expands any
9060 macro invocations present in the expression. @value{GDBN} also provides
9061 the following commands for working with macros explicitly.
9065 @kindex macro expand
9066 @cindex macro expansion, showing the results of preprocessor
9067 @cindex preprocessor macro expansion, showing the results of
9068 @cindex expanding preprocessor macros
9069 @item macro expand @var{expression}
9070 @itemx macro exp @var{expression}
9071 Show the results of expanding all preprocessor macro invocations in
9072 @var{expression}. Since @value{GDBN} simply expands macros, but does
9073 not parse the result, @var{expression} need not be a valid expression;
9074 it can be any string of tokens.
9077 @item macro expand-once @var{expression}
9078 @itemx macro exp1 @var{expression}
9079 @cindex expand macro once
9080 @i{(This command is not yet implemented.)} Show the results of
9081 expanding those preprocessor macro invocations that appear explicitly in
9082 @var{expression}. Macro invocations appearing in that expansion are
9083 left unchanged. This command allows you to see the effect of a
9084 particular macro more clearly, without being confused by further
9085 expansions. Since @value{GDBN} simply expands macros, but does not
9086 parse the result, @var{expression} need not be a valid expression; it
9087 can be any string of tokens.
9090 @cindex macro definition, showing
9091 @cindex definition, showing a macro's
9092 @item info macro @var{macro}
9093 Show the definition of the macro named @var{macro}, and describe the
9094 source location or compiler command-line where that definition was established.
9096 @kindex macro define
9097 @cindex user-defined macros
9098 @cindex defining macros interactively
9099 @cindex macros, user-defined
9100 @item macro define @var{macro} @var{replacement-list}
9101 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9102 Introduce a definition for a preprocessor macro named @var{macro},
9103 invocations of which are replaced by the tokens given in
9104 @var{replacement-list}. The first form of this command defines an
9105 ``object-like'' macro, which takes no arguments; the second form
9106 defines a ``function-like'' macro, which takes the arguments given in
9109 A definition introduced by this command is in scope in every
9110 expression evaluated in @value{GDBN}, until it is removed with the
9111 @code{macro undef} command, described below. The definition overrides
9112 all definitions for @var{macro} present in the program being debugged,
9113 as well as any previous user-supplied definition.
9116 @item macro undef @var{macro}
9117 Remove any user-supplied definition for the macro named @var{macro}.
9118 This command only affects definitions provided with the @code{macro
9119 define} command, described above; it cannot remove definitions present
9120 in the program being debugged.
9124 List all the macros defined using the @code{macro define} command.
9127 @cindex macros, example of debugging with
9128 Here is a transcript showing the above commands in action. First, we
9129 show our source files:
9137 #define ADD(x) (M + x)
9142 printf ("Hello, world!\n");
9144 printf ("We're so creative.\n");
9146 printf ("Goodbye, world!\n");
9153 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9154 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9155 compiler includes information about preprocessor macros in the debugging
9159 $ gcc -gdwarf-2 -g3 sample.c -o sample
9163 Now, we start @value{GDBN} on our sample program:
9167 GNU gdb 2002-05-06-cvs
9168 Copyright 2002 Free Software Foundation, Inc.
9169 GDB is free software, @dots{}
9173 We can expand macros and examine their definitions, even when the
9174 program is not running. @value{GDBN} uses the current listing position
9175 to decide which macro definitions are in scope:
9178 (@value{GDBP}) list main
9181 5 #define ADD(x) (M + x)
9186 10 printf ("Hello, world!\n");
9188 12 printf ("We're so creative.\n");
9189 (@value{GDBP}) info macro ADD
9190 Defined at /home/jimb/gdb/macros/play/sample.c:5
9191 #define ADD(x) (M + x)
9192 (@value{GDBP}) info macro Q
9193 Defined at /home/jimb/gdb/macros/play/sample.h:1
9194 included at /home/jimb/gdb/macros/play/sample.c:2
9196 (@value{GDBP}) macro expand ADD(1)
9197 expands to: (42 + 1)
9198 (@value{GDBP}) macro expand-once ADD(1)
9199 expands to: once (M + 1)
9203 In the example above, note that @code{macro expand-once} expands only
9204 the macro invocation explicit in the original text --- the invocation of
9205 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9206 which was introduced by @code{ADD}.
9208 Once the program is running, @value{GDBN} uses the macro definitions in
9209 force at the source line of the current stack frame:
9212 (@value{GDBP}) break main
9213 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9215 Starting program: /home/jimb/gdb/macros/play/sample
9217 Breakpoint 1, main () at sample.c:10
9218 10 printf ("Hello, world!\n");
9222 At line 10, the definition of the macro @code{N} at line 9 is in force:
9225 (@value{GDBP}) info macro N
9226 Defined at /home/jimb/gdb/macros/play/sample.c:9
9228 (@value{GDBP}) macro expand N Q M
9230 (@value{GDBP}) print N Q M
9235 As we step over directives that remove @code{N}'s definition, and then
9236 give it a new definition, @value{GDBN} finds the definition (or lack
9237 thereof) in force at each point:
9242 12 printf ("We're so creative.\n");
9243 (@value{GDBP}) info macro N
9244 The symbol `N' has no definition as a C/C++ preprocessor macro
9245 at /home/jimb/gdb/macros/play/sample.c:12
9248 14 printf ("Goodbye, world!\n");
9249 (@value{GDBP}) info macro N
9250 Defined at /home/jimb/gdb/macros/play/sample.c:13
9252 (@value{GDBP}) macro expand N Q M
9253 expands to: 1729 < 42
9254 (@value{GDBP}) print N Q M
9259 In addition to source files, macros can be defined on the compilation command
9260 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9261 such a way, @value{GDBN} displays the location of their definition as line zero
9262 of the source file submitted to the compiler.
9265 (@value{GDBP}) info macro __STDC__
9266 Defined at /home/jimb/gdb/macros/play/sample.c:0
9273 @chapter Tracepoints
9274 @c This chapter is based on the documentation written by Michael
9275 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9278 In some applications, it is not feasible for the debugger to interrupt
9279 the program's execution long enough for the developer to learn
9280 anything helpful about its behavior. If the program's correctness
9281 depends on its real-time behavior, delays introduced by a debugger
9282 might cause the program to change its behavior drastically, or perhaps
9283 fail, even when the code itself is correct. It is useful to be able
9284 to observe the program's behavior without interrupting it.
9286 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9287 specify locations in the program, called @dfn{tracepoints}, and
9288 arbitrary expressions to evaluate when those tracepoints are reached.
9289 Later, using the @code{tfind} command, you can examine the values
9290 those expressions had when the program hit the tracepoints. The
9291 expressions may also denote objects in memory---structures or arrays,
9292 for example---whose values @value{GDBN} should record; while visiting
9293 a particular tracepoint, you may inspect those objects as if they were
9294 in memory at that moment. However, because @value{GDBN} records these
9295 values without interacting with you, it can do so quickly and
9296 unobtrusively, hopefully not disturbing the program's behavior.
9298 The tracepoint facility is currently available only for remote
9299 targets. @xref{Targets}. In addition, your remote target must know
9300 how to collect trace data. This functionality is implemented in the
9301 remote stub; however, none of the stubs distributed with @value{GDBN}
9302 support tracepoints as of this writing. The format of the remote
9303 packets used to implement tracepoints are described in @ref{Tracepoint
9306 It is also possible to get trace data from a file, in a manner reminiscent
9307 of corefiles; you specify the filename, and use @code{tfind} to search
9308 through the file. @xref{Trace Files}, for more details.
9310 This chapter describes the tracepoint commands and features.
9314 * Analyze Collected Data::
9315 * Tracepoint Variables::
9319 @node Set Tracepoints
9320 @section Commands to Set Tracepoints
9322 Before running such a @dfn{trace experiment}, an arbitrary number of
9323 tracepoints can be set. A tracepoint is actually a special type of
9324 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9325 standard breakpoint commands. For instance, as with breakpoints,
9326 tracepoint numbers are successive integers starting from one, and many
9327 of the commands associated with tracepoints take the tracepoint number
9328 as their argument, to identify which tracepoint to work on.
9330 For each tracepoint, you can specify, in advance, some arbitrary set
9331 of data that you want the target to collect in the trace buffer when
9332 it hits that tracepoint. The collected data can include registers,
9333 local variables, or global data. Later, you can use @value{GDBN}
9334 commands to examine the values these data had at the time the
9337 Tracepoints do not support every breakpoint feature. Ignore counts on
9338 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9339 commands when they are hit. Tracepoints may not be thread-specific
9342 @cindex fast tracepoints
9343 Some targets may support @dfn{fast tracepoints}, which are inserted in
9344 a different way (such as with a jump instead of a trap), that is
9345 faster but possibly restricted in where they may be installed.
9347 This section describes commands to set tracepoints and associated
9348 conditions and actions.
9351 * Create and Delete Tracepoints::
9352 * Enable and Disable Tracepoints::
9353 * Tracepoint Passcounts::
9354 * Tracepoint Conditions::
9355 * Trace State Variables::
9356 * Tracepoint Actions::
9357 * Listing Tracepoints::
9358 * Starting and Stopping Trace Experiments::
9359 * Tracepoint Restrictions::
9362 @node Create and Delete Tracepoints
9363 @subsection Create and Delete Tracepoints
9366 @cindex set tracepoint
9368 @item trace @var{location}
9369 The @code{trace} command is very similar to the @code{break} command.
9370 Its argument @var{location} can be a source line, a function name, or
9371 an address in the target program. @xref{Specify Location}. The
9372 @code{trace} command defines a tracepoint, which is a point in the
9373 target program where the debugger will briefly stop, collect some
9374 data, and then allow the program to continue. Setting a tracepoint or
9375 changing its actions doesn't take effect until the next @code{tstart}
9376 command, and once a trace experiment is running, further changes will
9377 not have any effect until the next trace experiment starts.
9379 Here are some examples of using the @code{trace} command:
9382 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9384 (@value{GDBP}) @b{trace +2} // 2 lines forward
9386 (@value{GDBP}) @b{trace my_function} // first source line of function
9388 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9390 (@value{GDBP}) @b{trace *0x2117c4} // an address
9394 You can abbreviate @code{trace} as @code{tr}.
9396 @item trace @var{location} if @var{cond}
9397 Set a tracepoint with condition @var{cond}; evaluate the expression
9398 @var{cond} each time the tracepoint is reached, and collect data only
9399 if the value is nonzero---that is, if @var{cond} evaluates as true.
9400 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9401 information on tracepoint conditions.
9403 @item ftrace @var{location} [ if @var{cond} ]
9404 @cindex set fast tracepoint
9406 The @code{ftrace} command sets a fast tracepoint. For targets that
9407 support them, fast tracepoints will use a more efficient but possibly
9408 less general technique to trigger data collection, such as a jump
9409 instruction instead of a trap, or some sort of hardware support. It
9410 may not be possible to create a fast tracepoint at the desired
9411 location, in which case the command will exit with an explanatory
9414 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9418 @cindex last tracepoint number
9419 @cindex recent tracepoint number
9420 @cindex tracepoint number
9421 The convenience variable @code{$tpnum} records the tracepoint number
9422 of the most recently set tracepoint.
9424 @kindex delete tracepoint
9425 @cindex tracepoint deletion
9426 @item delete tracepoint @r{[}@var{num}@r{]}
9427 Permanently delete one or more tracepoints. With no argument, the
9428 default is to delete all tracepoints. Note that the regular
9429 @code{delete} command can remove tracepoints also.
9434 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9436 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9440 You can abbreviate this command as @code{del tr}.
9443 @node Enable and Disable Tracepoints
9444 @subsection Enable and Disable Tracepoints
9446 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9449 @kindex disable tracepoint
9450 @item disable tracepoint @r{[}@var{num}@r{]}
9451 Disable tracepoint @var{num}, or all tracepoints if no argument
9452 @var{num} is given. A disabled tracepoint will have no effect during
9453 the next trace experiment, but it is not forgotten. You can re-enable
9454 a disabled tracepoint using the @code{enable tracepoint} command.
9456 @kindex enable tracepoint
9457 @item enable tracepoint @r{[}@var{num}@r{]}
9458 Enable tracepoint @var{num}, or all tracepoints. The enabled
9459 tracepoints will become effective the next time a trace experiment is
9463 @node Tracepoint Passcounts
9464 @subsection Tracepoint Passcounts
9468 @cindex tracepoint pass count
9469 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9470 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9471 automatically stop a trace experiment. If a tracepoint's passcount is
9472 @var{n}, then the trace experiment will be automatically stopped on
9473 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9474 @var{num} is not specified, the @code{passcount} command sets the
9475 passcount of the most recently defined tracepoint. If no passcount is
9476 given, the trace experiment will run until stopped explicitly by the
9482 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9483 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9485 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9486 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9487 (@value{GDBP}) @b{trace foo}
9488 (@value{GDBP}) @b{pass 3}
9489 (@value{GDBP}) @b{trace bar}
9490 (@value{GDBP}) @b{pass 2}
9491 (@value{GDBP}) @b{trace baz}
9492 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9493 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9494 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9495 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9499 @node Tracepoint Conditions
9500 @subsection Tracepoint Conditions
9501 @cindex conditional tracepoints
9502 @cindex tracepoint conditions
9504 The simplest sort of tracepoint collects data every time your program
9505 reaches a specified place. You can also specify a @dfn{condition} for
9506 a tracepoint. A condition is just a Boolean expression in your
9507 programming language (@pxref{Expressions, ,Expressions}). A
9508 tracepoint with a condition evaluates the expression each time your
9509 program reaches it, and data collection happens only if the condition
9512 Tracepoint conditions can be specified when a tracepoint is set, by
9513 using @samp{if} in the arguments to the @code{trace} command.
9514 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9515 also be set or changed at any time with the @code{condition} command,
9516 just as with breakpoints.
9518 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9519 the conditional expression itself. Instead, @value{GDBN} encodes the
9520 expression into an agent expression (@pxref{Agent Expressions}
9521 suitable for execution on the target, independently of @value{GDBN}.
9522 Global variables become raw memory locations, locals become stack
9523 accesses, and so forth.
9525 For instance, suppose you have a function that is usually called
9526 frequently, but should not be called after an error has occurred. You
9527 could use the following tracepoint command to collect data about calls
9528 of that function that happen while the error code is propagating
9529 through the program; an unconditional tracepoint could end up
9530 collecting thousands of useless trace frames that you would have to
9534 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9537 @node Trace State Variables
9538 @subsection Trace State Variables
9539 @cindex trace state variables
9541 A @dfn{trace state variable} is a special type of variable that is
9542 created and managed by target-side code. The syntax is the same as
9543 that for GDB's convenience variables (a string prefixed with ``$''),
9544 but they are stored on the target. They must be created explicitly,
9545 using a @code{tvariable} command. They are always 64-bit signed
9548 Trace state variables are remembered by @value{GDBN}, and downloaded
9549 to the target along with tracepoint information when the trace
9550 experiment starts. There are no intrinsic limits on the number of
9551 trace state variables, beyond memory limitations of the target.
9553 @cindex convenience variables, and trace state variables
9554 Although trace state variables are managed by the target, you can use
9555 them in print commands and expressions as if they were convenience
9556 variables; @value{GDBN} will get the current value from the target
9557 while the trace experiment is running. Trace state variables share
9558 the same namespace as other ``$'' variables, which means that you
9559 cannot have trace state variables with names like @code{$23} or
9560 @code{$pc}, nor can you have a trace state variable and a convenience
9561 variable with the same name.
9565 @item tvariable $@var{name} [ = @var{expression} ]
9567 The @code{tvariable} command creates a new trace state variable named
9568 @code{$@var{name}}, and optionally gives it an initial value of
9569 @var{expression}. @var{expression} is evaluated when this command is
9570 entered; the result will be converted to an integer if possible,
9571 otherwise @value{GDBN} will report an error. A subsequent
9572 @code{tvariable} command specifying the same name does not create a
9573 variable, but instead assigns the supplied initial value to the
9574 existing variable of that name, overwriting any previous initial
9575 value. The default initial value is 0.
9577 @item info tvariables
9578 @kindex info tvariables
9579 List all the trace state variables along with their initial values.
9580 Their current values may also be displayed, if the trace experiment is
9583 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
9584 @kindex delete tvariable
9585 Delete the given trace state variables, or all of them if no arguments
9590 @node Tracepoint Actions
9591 @subsection Tracepoint Action Lists
9595 @cindex tracepoint actions
9596 @item actions @r{[}@var{num}@r{]}
9597 This command will prompt for a list of actions to be taken when the
9598 tracepoint is hit. If the tracepoint number @var{num} is not
9599 specified, this command sets the actions for the one that was most
9600 recently defined (so that you can define a tracepoint and then say
9601 @code{actions} without bothering about its number). You specify the
9602 actions themselves on the following lines, one action at a time, and
9603 terminate the actions list with a line containing just @code{end}. So
9604 far, the only defined actions are @code{collect}, @code{teval}, and
9605 @code{while-stepping}.
9607 @cindex remove actions from a tracepoint
9608 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9609 and follow it immediately with @samp{end}.
9612 (@value{GDBP}) @b{collect @var{data}} // collect some data
9614 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9616 (@value{GDBP}) @b{end} // signals the end of actions.
9619 In the following example, the action list begins with @code{collect}
9620 commands indicating the things to be collected when the tracepoint is
9621 hit. Then, in order to single-step and collect additional data
9622 following the tracepoint, a @code{while-stepping} command is used,
9623 followed by the list of things to be collected after each step in a
9624 sequence of single steps. The @code{while-stepping} command is
9625 terminated by its own separate @code{end} command. Lastly, the action
9626 list is terminated by an @code{end} command.
9629 (@value{GDBP}) @b{trace foo}
9630 (@value{GDBP}) @b{actions}
9631 Enter actions for tracepoint 1, one per line:
9640 @kindex collect @r{(tracepoints)}
9641 @item collect @var{expr1}, @var{expr2}, @dots{}
9642 Collect values of the given expressions when the tracepoint is hit.
9643 This command accepts a comma-separated list of any valid expressions.
9644 In addition to global, static, or local variables, the following
9645 special arguments are supported:
9649 collect all registers
9652 collect all function arguments
9655 collect all local variables.
9658 You can give several consecutive @code{collect} commands, each one
9659 with a single argument, or one @code{collect} command with several
9660 arguments separated by commas: the effect is the same.
9662 The command @code{info scope} (@pxref{Symbols, info scope}) is
9663 particularly useful for figuring out what data to collect.
9665 @kindex teval @r{(tracepoints)}
9666 @item teval @var{expr1}, @var{expr2}, @dots{}
9667 Evaluate the given expressions when the tracepoint is hit. This
9668 command accepts a comma-separated list of expressions. The results
9669 are discarded, so this is mainly useful for assigning values to trace
9670 state variables (@pxref{Trace State Variables}) without adding those
9671 values to the trace buffer, as would be the case if the @code{collect}
9674 @kindex while-stepping @r{(tracepoints)}
9675 @item while-stepping @var{n}
9676 Perform @var{n} single-step instruction traces after the tracepoint,
9677 collecting new data after each step. The @code{while-stepping}
9678 command is followed by the list of what to collect while stepping
9679 (followed by its own @code{end} command):
9683 > collect $regs, myglobal
9689 Note that @code{$pc} is not automatically collected by
9690 @code{while-stepping}; you need to explicitly collect that register if
9691 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
9694 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
9695 @kindex set default-collect
9696 @cindex default collection action
9697 This variable is a list of expressions to collect at each tracepoint
9698 hit. It is effectively an additional @code{collect} action prepended
9699 to every tracepoint action list. The expressions are parsed
9700 individually for each tracepoint, so for instance a variable named
9701 @code{xyz} may be interpreted as a global for one tracepoint, and a
9702 local for another, as appropriate to the tracepoint's location.
9704 @item show default-collect
9705 @kindex show default-collect
9706 Show the list of expressions that are collected by default at each
9711 @node Listing Tracepoints
9712 @subsection Listing Tracepoints
9715 @kindex info tracepoints
9717 @cindex information about tracepoints
9718 @item info tracepoints @r{[}@var{num}@r{]}
9719 Display information about the tracepoint @var{num}. If you don't
9720 specify a tracepoint number, displays information about all the
9721 tracepoints defined so far. The format is similar to that used for
9722 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
9723 command, simply restricting itself to tracepoints.
9725 A tracepoint's listing may include additional information specific to
9730 its passcount as given by the @code{passcount @var{n}} command
9732 its step count as given by the @code{while-stepping @var{n}} command
9734 its action list as given by the @code{actions} command. The actions
9735 are prefixed with an @samp{A} so as to distinguish them from commands.
9739 (@value{GDBP}) @b{info trace}
9740 Num Type Disp Enb Address What
9741 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
9745 A collect globfoo, $regs
9753 This command can be abbreviated @code{info tp}.
9756 @node Starting and Stopping Trace Experiments
9757 @subsection Starting and Stopping Trace Experiments
9761 @cindex start a new trace experiment
9762 @cindex collected data discarded
9764 This command takes no arguments. It starts the trace experiment, and
9765 begins collecting data. This has the side effect of discarding all
9766 the data collected in the trace buffer during the previous trace
9770 @cindex stop a running trace experiment
9772 This command takes no arguments. It ends the trace experiment, and
9773 stops collecting data.
9775 @strong{Note}: a trace experiment and data collection may stop
9776 automatically if any tracepoint's passcount is reached
9777 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
9780 @cindex status of trace data collection
9781 @cindex trace experiment, status of
9783 This command displays the status of the current trace data
9787 Here is an example of the commands we described so far:
9790 (@value{GDBP}) @b{trace gdb_c_test}
9791 (@value{GDBP}) @b{actions}
9792 Enter actions for tracepoint #1, one per line.
9793 > collect $regs,$locals,$args
9798 (@value{GDBP}) @b{tstart}
9799 [time passes @dots{}]
9800 (@value{GDBP}) @b{tstop}
9803 @cindex disconnected tracing
9804 You can choose to continue running the trace experiment even if
9805 @value{GDBN} disconnects from the target, voluntarily or
9806 involuntarily. For commands such as @code{detach}, the debugger will
9807 ask what you want to do with the trace. But for unexpected
9808 terminations (@value{GDBN} crash, network outage), it would be
9809 unfortunate to lose hard-won trace data, so the variable
9810 @code{disconnected-tracing} lets you decide whether the trace should
9811 continue running without @value{GDBN}.
9814 @item set disconnected-tracing on
9815 @itemx set disconnected-tracing off
9816 @kindex set disconnected-tracing
9817 Choose whether a tracing run should continue to run if @value{GDBN}
9818 has disconnected from the target. Note that @code{detach} or
9819 @code{quit} will ask you directly what to do about a running trace no
9820 matter what this variable's setting, so the variable is mainly useful
9821 for handling unexpected situations, such as loss of the network.
9823 @item show disconnected-tracing
9824 @kindex show disconnected-tracing
9825 Show the current choice for disconnected tracing.
9829 When you reconnect to the target, the trace experiment may or may not
9830 still be running; it might have filled the trace buffer in the
9831 meantime, or stopped for one of the other reasons. If it is running,
9832 it will continue after reconnection.
9834 Upon reconnection, the target will upload information about the
9835 tracepoints in effect. @value{GDBN} will then compare that
9836 information to the set of tracepoints currently defined, and attempt
9837 to match them up, allowing for the possibility that the numbers may
9838 have changed due to creation and deletion in the meantime. If one of
9839 the target's tracepoints does not match any in @value{GDBN}, the
9840 debugger will create a new tracepoint, so that you have a number with
9841 which to specify that tracepoint. This matching-up process is
9842 necessarily heuristic, and it may result in useless tracepoints being
9843 created; you may simply delete them if they are of no use.
9845 @cindex circular trace buffer
9846 If your target agent supports a @dfn{circular trace buffer}, then you
9847 can run a trace experiment indefinitely without filling the trace
9848 buffer; when space runs out, the agent deletes already-collected trace
9849 frames, oldest first, until there is enough room to continue
9850 collecting. This is especially useful if your tracepoints are being
9851 hit too often, and your trace gets terminated prematurely because the
9852 buffer is full. To ask for a circular trace buffer, simply set
9853 @samp{circular_trace_buffer} to on. You can set this at any time,
9854 including during tracing; if the agent can do it, it will change
9855 buffer handling on the fly, otherwise it will not take effect until
9859 @item set circular-trace-buffer on
9860 @itemx set circular-trace-buffer off
9861 @kindex set circular-trace-buffer
9862 Choose whether a tracing run should use a linear or circular buffer
9863 for trace data. A linear buffer will not lose any trace data, but may
9864 fill up prematurely, while a circular buffer will discard old trace
9865 data, but it will have always room for the latest tracepoint hits.
9867 @item show circular-trace-buffer
9868 @kindex show circular-trace-buffer
9869 Show the current choice for the trace buffer. Note that this may not
9870 match the agent's current buffer handling, nor is it guaranteed to
9871 match the setting that might have been in effect during a past run,
9872 for instance if you are looking at frames from a trace file.
9876 @node Tracepoint Restrictions
9877 @subsection Tracepoint Restrictions
9879 @cindex tracepoint restrictions
9880 There are a number of restrictions on the use of tracepoints. As
9881 described above, tracepoint data gathering occurs on the target
9882 without interaction from @value{GDBN}. Thus the full capabilities of
9883 the debugger are not available during data gathering, and then at data
9884 examination time, you will be limited by only having what was
9885 collected. The following items describe some common problems, but it
9886 is not exhaustive, and you may run into additional difficulties not
9892 Tracepoint expressions are intended to gather objects (lvalues). Thus
9893 the full flexibility of GDB's expression evaluator is not available.
9894 You cannot call functions, cast objects to aggregate types, access
9895 convenience variables or modify values (except by assignment to trace
9896 state variables). Some language features may implicitly call
9897 functions (for instance Objective-C fields with accessors), and therefore
9898 cannot be collected either.
9901 Collection of local variables, either individually or in bulk with
9902 @code{$locals} or @code{$args}, during @code{while-stepping} may
9903 behave erratically. The stepping action may enter a new scope (for
9904 instance by stepping into a function), or the location of the variable
9905 may change (for instance it is loaded into a register). The
9906 tracepoint data recorded uses the location information for the
9907 variables that is correct for the tracepoint location. When the
9908 tracepoint is created, it is not possible, in general, to determine
9909 where the steps of a @code{while-stepping} sequence will advance the
9910 program---particularly if a conditional branch is stepped.
9913 Collection of an incompletely-initialized or partially-destroyed object
9914 may result in something that @value{GDBN} cannot display, or displays
9915 in a misleading way.
9918 When @value{GDBN} displays a pointer to character it automatically
9919 dereferences the pointer to also display characters of the string
9920 being pointed to. However, collecting the pointer during tracing does
9921 not automatically collect the string. You need to explicitly
9922 dereference the pointer and provide size information if you want to
9923 collect not only the pointer, but the memory pointed to. For example,
9924 @code{*ptr@@50} can be used to collect the 50 element array pointed to
9928 It is not possible to collect a complete stack backtrace at a
9929 tracepoint. Instead, you may collect the registers and a few hundred
9930 bytes from the stack pointer with something like @code{*$esp@@300}
9931 (adjust to use the name of the actual stack pointer register on your
9932 target architecture, and the amount of stack you wish to capture).
9933 Then the @code{backtrace} command will show a partial backtrace when
9934 using a trace frame. The number of stack frames that can be examined
9935 depends on the sizes of the frames in the collected stack. Note that
9936 if you ask for a block so large that it goes past the bottom of the
9937 stack, the target agent may report an error trying to read from an
9941 If you do not collect registers at a tracepoint, @value{GDBN} can
9942 infer that the value of @code{$pc} must be the same as the address of
9943 the tracepoint and use that when you are looking at a trace frame
9944 for that tracepoint. However, this cannot work if the tracepoint has
9945 multiple locations (for instance if it was set in a function that was
9946 inlined), or if it has a @code{while-stepping} loop. In those cases
9947 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
9952 @node Analyze Collected Data
9953 @section Using the Collected Data
9955 After the tracepoint experiment ends, you use @value{GDBN} commands
9956 for examining the trace data. The basic idea is that each tracepoint
9957 collects a trace @dfn{snapshot} every time it is hit and another
9958 snapshot every time it single-steps. All these snapshots are
9959 consecutively numbered from zero and go into a buffer, and you can
9960 examine them later. The way you examine them is to @dfn{focus} on a
9961 specific trace snapshot. When the remote stub is focused on a trace
9962 snapshot, it will respond to all @value{GDBN} requests for memory and
9963 registers by reading from the buffer which belongs to that snapshot,
9964 rather than from @emph{real} memory or registers of the program being
9965 debugged. This means that @strong{all} @value{GDBN} commands
9966 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
9967 behave as if we were currently debugging the program state as it was
9968 when the tracepoint occurred. Any requests for data that are not in
9969 the buffer will fail.
9972 * tfind:: How to select a trace snapshot
9973 * tdump:: How to display all data for a snapshot
9974 * save-tracepoints:: How to save tracepoints for a future run
9978 @subsection @code{tfind @var{n}}
9981 @cindex select trace snapshot
9982 @cindex find trace snapshot
9983 The basic command for selecting a trace snapshot from the buffer is
9984 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
9985 counting from zero. If no argument @var{n} is given, the next
9986 snapshot is selected.
9988 Here are the various forms of using the @code{tfind} command.
9992 Find the first snapshot in the buffer. This is a synonym for
9993 @code{tfind 0} (since 0 is the number of the first snapshot).
9996 Stop debugging trace snapshots, resume @emph{live} debugging.
9999 Same as @samp{tfind none}.
10002 No argument means find the next trace snapshot.
10005 Find the previous trace snapshot before the current one. This permits
10006 retracing earlier steps.
10008 @item tfind tracepoint @var{num}
10009 Find the next snapshot associated with tracepoint @var{num}. Search
10010 proceeds forward from the last examined trace snapshot. If no
10011 argument @var{num} is given, it means find the next snapshot collected
10012 for the same tracepoint as the current snapshot.
10014 @item tfind pc @var{addr}
10015 Find the next snapshot associated with the value @var{addr} of the
10016 program counter. Search proceeds forward from the last examined trace
10017 snapshot. If no argument @var{addr} is given, it means find the next
10018 snapshot with the same value of PC as the current snapshot.
10020 @item tfind outside @var{addr1}, @var{addr2}
10021 Find the next snapshot whose PC is outside the given range of
10022 addresses (exclusive).
10024 @item tfind range @var{addr1}, @var{addr2}
10025 Find the next snapshot whose PC is between @var{addr1} and
10026 @var{addr2} (inclusive).
10028 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10029 Find the next snapshot associated with the source line @var{n}. If
10030 the optional argument @var{file} is given, refer to line @var{n} in
10031 that source file. Search proceeds forward from the last examined
10032 trace snapshot. If no argument @var{n} is given, it means find the
10033 next line other than the one currently being examined; thus saying
10034 @code{tfind line} repeatedly can appear to have the same effect as
10035 stepping from line to line in a @emph{live} debugging session.
10038 The default arguments for the @code{tfind} commands are specifically
10039 designed to make it easy to scan through the trace buffer. For
10040 instance, @code{tfind} with no argument selects the next trace
10041 snapshot, and @code{tfind -} with no argument selects the previous
10042 trace snapshot. So, by giving one @code{tfind} command, and then
10043 simply hitting @key{RET} repeatedly you can examine all the trace
10044 snapshots in order. Or, by saying @code{tfind -} and then hitting
10045 @key{RET} repeatedly you can examine the snapshots in reverse order.
10046 The @code{tfind line} command with no argument selects the snapshot
10047 for the next source line executed. The @code{tfind pc} command with
10048 no argument selects the next snapshot with the same program counter
10049 (PC) as the current frame. The @code{tfind tracepoint} command with
10050 no argument selects the next trace snapshot collected by the same
10051 tracepoint as the current one.
10053 In addition to letting you scan through the trace buffer manually,
10054 these commands make it easy to construct @value{GDBN} scripts that
10055 scan through the trace buffer and print out whatever collected data
10056 you are interested in. Thus, if we want to examine the PC, FP, and SP
10057 registers from each trace frame in the buffer, we can say this:
10060 (@value{GDBP}) @b{tfind start}
10061 (@value{GDBP}) @b{while ($trace_frame != -1)}
10062 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10063 $trace_frame, $pc, $sp, $fp
10067 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10068 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10069 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10070 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10071 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10072 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10073 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10074 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10075 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10076 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10077 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10080 Or, if we want to examine the variable @code{X} at each source line in
10084 (@value{GDBP}) @b{tfind start}
10085 (@value{GDBP}) @b{while ($trace_frame != -1)}
10086 > printf "Frame %d, X == %d\n", $trace_frame, X
10096 @subsection @code{tdump}
10098 @cindex dump all data collected at tracepoint
10099 @cindex tracepoint data, display
10101 This command takes no arguments. It prints all the data collected at
10102 the current trace snapshot.
10105 (@value{GDBP}) @b{trace 444}
10106 (@value{GDBP}) @b{actions}
10107 Enter actions for tracepoint #2, one per line:
10108 > collect $regs, $locals, $args, gdb_long_test
10111 (@value{GDBP}) @b{tstart}
10113 (@value{GDBP}) @b{tfind line 444}
10114 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10116 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10118 (@value{GDBP}) @b{tdump}
10119 Data collected at tracepoint 2, trace frame 1:
10120 d0 0xc4aa0085 -995491707
10124 d4 0x71aea3d 119204413
10127 d7 0x380035 3670069
10128 a0 0x19e24a 1696330
10129 a1 0x3000668 50333288
10131 a3 0x322000 3284992
10132 a4 0x3000698 50333336
10133 a5 0x1ad3cc 1758156
10134 fp 0x30bf3c 0x30bf3c
10135 sp 0x30bf34 0x30bf34
10137 pc 0x20b2c8 0x20b2c8
10141 p = 0x20e5b4 "gdb-test"
10148 gdb_long_test = 17 '\021'
10153 @code{tdump} works by scanning the tracepoint's current collection
10154 actions and printing the value of each expression listed. So
10155 @code{tdump} can fail, if after a run, you change the tracepoint's
10156 actions to mention variables that were not collected during the run.
10158 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10159 uses the collected value of @code{$pc} to distinguish between trace
10160 frames that were collected at the tracepoint hit, and frames that were
10161 collected while stepping. This allows it to correctly choose whether
10162 to display the basic list of collections, or the collections from the
10163 body of the while-stepping loop. However, if @code{$pc} was not collected,
10164 then @code{tdump} will always attempt to dump using the basic collection
10165 list, and may fail if a while-stepping frame does not include all the
10166 same data that is collected at the tracepoint hit.
10167 @c This is getting pretty arcane, example would be good.
10169 @node save-tracepoints
10170 @subsection @code{save-tracepoints @var{filename}}
10171 @kindex save-tracepoints
10172 @cindex save tracepoints for future sessions
10174 This command saves all current tracepoint definitions together with
10175 their actions and passcounts, into a file @file{@var{filename}}
10176 suitable for use in a later debugging session. To read the saved
10177 tracepoint definitions, use the @code{source} command (@pxref{Command
10180 @node Tracepoint Variables
10181 @section Convenience Variables for Tracepoints
10182 @cindex tracepoint variables
10183 @cindex convenience variables for tracepoints
10186 @vindex $trace_frame
10187 @item (int) $trace_frame
10188 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10189 snapshot is selected.
10191 @vindex $tracepoint
10192 @item (int) $tracepoint
10193 The tracepoint for the current trace snapshot.
10195 @vindex $trace_line
10196 @item (int) $trace_line
10197 The line number for the current trace snapshot.
10199 @vindex $trace_file
10200 @item (char []) $trace_file
10201 The source file for the current trace snapshot.
10203 @vindex $trace_func
10204 @item (char []) $trace_func
10205 The name of the function containing @code{$tracepoint}.
10208 Note: @code{$trace_file} is not suitable for use in @code{printf},
10209 use @code{output} instead.
10211 Here's a simple example of using these convenience variables for
10212 stepping through all the trace snapshots and printing some of their
10213 data. Note that these are not the same as trace state variables,
10214 which are managed by the target.
10217 (@value{GDBP}) @b{tfind start}
10219 (@value{GDBP}) @b{while $trace_frame != -1}
10220 > output $trace_file
10221 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10227 @section Using Trace Files
10228 @cindex trace files
10230 In some situations, the target running a trace experiment may no
10231 longer be available; perhaps it crashed, or the hardware was needed
10232 for a different activity. To handle these cases, you can arrange to
10233 dump the trace data into a file, and later use that file as a source
10234 of trace data, via the @code{target tfile} command.
10239 @item tsave [ -r ] @var{filename}
10240 Save the trace data to @var{filename}. By default, this command
10241 assumes that @var{filename} refers to the host filesystem, so if
10242 necessary @value{GDBN} will copy raw trace data up from the target and
10243 then save it. If the target supports it, you can also supply the
10244 optional argument @code{-r} (``remote'') to direct the target to save
10245 the data directly into @var{filename} in its own filesystem, which may be
10246 more efficient if the trace buffer is very large. (Note, however, that
10247 @code{target tfile} can only read from files accessible to the host.)
10249 @kindex target tfile
10251 @item target tfile @var{filename}
10252 Use the file named @var{filename} as a source of trace data. Commands
10253 that examine data work as they do with a live target, but it is not
10254 possible to run any new trace experiments. @code{tstatus} will report
10255 the state of the trace run at the moment the data was saved, as well
10256 as the current trace frame you are examining. @var{filename} must be
10257 on a filesystem accessible to the host.
10262 @chapter Debugging Programs That Use Overlays
10265 If your program is too large to fit completely in your target system's
10266 memory, you can sometimes use @dfn{overlays} to work around this
10267 problem. @value{GDBN} provides some support for debugging programs that
10271 * How Overlays Work:: A general explanation of overlays.
10272 * Overlay Commands:: Managing overlays in @value{GDBN}.
10273 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10274 mapped by asking the inferior.
10275 * Overlay Sample Program:: A sample program using overlays.
10278 @node How Overlays Work
10279 @section How Overlays Work
10280 @cindex mapped overlays
10281 @cindex unmapped overlays
10282 @cindex load address, overlay's
10283 @cindex mapped address
10284 @cindex overlay area
10286 Suppose you have a computer whose instruction address space is only 64
10287 kilobytes long, but which has much more memory which can be accessed by
10288 other means: special instructions, segment registers, or memory
10289 management hardware, for example. Suppose further that you want to
10290 adapt a program which is larger than 64 kilobytes to run on this system.
10292 One solution is to identify modules of your program which are relatively
10293 independent, and need not call each other directly; call these modules
10294 @dfn{overlays}. Separate the overlays from the main program, and place
10295 their machine code in the larger memory. Place your main program in
10296 instruction memory, but leave at least enough space there to hold the
10297 largest overlay as well.
10299 Now, to call a function located in an overlay, you must first copy that
10300 overlay's machine code from the large memory into the space set aside
10301 for it in the instruction memory, and then jump to its entry point
10304 @c NB: In the below the mapped area's size is greater or equal to the
10305 @c size of all overlays. This is intentional to remind the developer
10306 @c that overlays don't necessarily need to be the same size.
10310 Data Instruction Larger
10311 Address Space Address Space Address Space
10312 +-----------+ +-----------+ +-----------+
10314 +-----------+ +-----------+ +-----------+<-- overlay 1
10315 | program | | main | .----| overlay 1 | load address
10316 | variables | | program | | +-----------+
10317 | and heap | | | | | |
10318 +-----------+ | | | +-----------+<-- overlay 2
10319 | | +-----------+ | | | load address
10320 +-----------+ | | | .-| overlay 2 |
10322 mapped --->+-----------+ | | +-----------+
10323 address | | | | | |
10324 | overlay | <-' | | |
10325 | area | <---' +-----------+<-- overlay 3
10326 | | <---. | | load address
10327 +-----------+ `--| overlay 3 |
10334 @anchor{A code overlay}A code overlay
10338 The diagram (@pxref{A code overlay}) shows a system with separate data
10339 and instruction address spaces. To map an overlay, the program copies
10340 its code from the larger address space to the instruction address space.
10341 Since the overlays shown here all use the same mapped address, only one
10342 may be mapped at a time. For a system with a single address space for
10343 data and instructions, the diagram would be similar, except that the
10344 program variables and heap would share an address space with the main
10345 program and the overlay area.
10347 An overlay loaded into instruction memory and ready for use is called a
10348 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10349 instruction memory. An overlay not present (or only partially present)
10350 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10351 is its address in the larger memory. The mapped address is also called
10352 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10353 called the @dfn{load memory address}, or @dfn{LMA}.
10355 Unfortunately, overlays are not a completely transparent way to adapt a
10356 program to limited instruction memory. They introduce a new set of
10357 global constraints you must keep in mind as you design your program:
10362 Before calling or returning to a function in an overlay, your program
10363 must make sure that overlay is actually mapped. Otherwise, the call or
10364 return will transfer control to the right address, but in the wrong
10365 overlay, and your program will probably crash.
10368 If the process of mapping an overlay is expensive on your system, you
10369 will need to choose your overlays carefully to minimize their effect on
10370 your program's performance.
10373 The executable file you load onto your system must contain each
10374 overlay's instructions, appearing at the overlay's load address, not its
10375 mapped address. However, each overlay's instructions must be relocated
10376 and its symbols defined as if the overlay were at its mapped address.
10377 You can use GNU linker scripts to specify different load and relocation
10378 addresses for pieces of your program; see @ref{Overlay Description,,,
10379 ld.info, Using ld: the GNU linker}.
10382 The procedure for loading executable files onto your system must be able
10383 to load their contents into the larger address space as well as the
10384 instruction and data spaces.
10388 The overlay system described above is rather simple, and could be
10389 improved in many ways:
10394 If your system has suitable bank switch registers or memory management
10395 hardware, you could use those facilities to make an overlay's load area
10396 contents simply appear at their mapped address in instruction space.
10397 This would probably be faster than copying the overlay to its mapped
10398 area in the usual way.
10401 If your overlays are small enough, you could set aside more than one
10402 overlay area, and have more than one overlay mapped at a time.
10405 You can use overlays to manage data, as well as instructions. In
10406 general, data overlays are even less transparent to your design than
10407 code overlays: whereas code overlays only require care when you call or
10408 return to functions, data overlays require care every time you access
10409 the data. Also, if you change the contents of a data overlay, you
10410 must copy its contents back out to its load address before you can copy a
10411 different data overlay into the same mapped area.
10416 @node Overlay Commands
10417 @section Overlay Commands
10419 To use @value{GDBN}'s overlay support, each overlay in your program must
10420 correspond to a separate section of the executable file. The section's
10421 virtual memory address and load memory address must be the overlay's
10422 mapped and load addresses. Identifying overlays with sections allows
10423 @value{GDBN} to determine the appropriate address of a function or
10424 variable, depending on whether the overlay is mapped or not.
10426 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10427 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10432 Disable @value{GDBN}'s overlay support. When overlay support is
10433 disabled, @value{GDBN} assumes that all functions and variables are
10434 always present at their mapped addresses. By default, @value{GDBN}'s
10435 overlay support is disabled.
10437 @item overlay manual
10438 @cindex manual overlay debugging
10439 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10440 relies on you to tell it which overlays are mapped, and which are not,
10441 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10442 commands described below.
10444 @item overlay map-overlay @var{overlay}
10445 @itemx overlay map @var{overlay}
10446 @cindex map an overlay
10447 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10448 be the name of the object file section containing the overlay. When an
10449 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10450 functions and variables at their mapped addresses. @value{GDBN} assumes
10451 that any other overlays whose mapped ranges overlap that of
10452 @var{overlay} are now unmapped.
10454 @item overlay unmap-overlay @var{overlay}
10455 @itemx overlay unmap @var{overlay}
10456 @cindex unmap an overlay
10457 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10458 must be the name of the object file section containing the overlay.
10459 When an overlay is unmapped, @value{GDBN} assumes it can find the
10460 overlay's functions and variables at their load addresses.
10463 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10464 consults a data structure the overlay manager maintains in the inferior
10465 to see which overlays are mapped. For details, see @ref{Automatic
10466 Overlay Debugging}.
10468 @item overlay load-target
10469 @itemx overlay load
10470 @cindex reloading the overlay table
10471 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10472 re-reads the table @value{GDBN} automatically each time the inferior
10473 stops, so this command should only be necessary if you have changed the
10474 overlay mapping yourself using @value{GDBN}. This command is only
10475 useful when using automatic overlay debugging.
10477 @item overlay list-overlays
10478 @itemx overlay list
10479 @cindex listing mapped overlays
10480 Display a list of the overlays currently mapped, along with their mapped
10481 addresses, load addresses, and sizes.
10485 Normally, when @value{GDBN} prints a code address, it includes the name
10486 of the function the address falls in:
10489 (@value{GDBP}) print main
10490 $3 = @{int ()@} 0x11a0 <main>
10493 When overlay debugging is enabled, @value{GDBN} recognizes code in
10494 unmapped overlays, and prints the names of unmapped functions with
10495 asterisks around them. For example, if @code{foo} is a function in an
10496 unmapped overlay, @value{GDBN} prints it this way:
10499 (@value{GDBP}) overlay list
10500 No sections are mapped.
10501 (@value{GDBP}) print foo
10502 $5 = @{int (int)@} 0x100000 <*foo*>
10505 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10509 (@value{GDBP}) overlay list
10510 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10511 mapped at 0x1016 - 0x104a
10512 (@value{GDBP}) print foo
10513 $6 = @{int (int)@} 0x1016 <foo>
10516 When overlay debugging is enabled, @value{GDBN} can find the correct
10517 address for functions and variables in an overlay, whether or not the
10518 overlay is mapped. This allows most @value{GDBN} commands, like
10519 @code{break} and @code{disassemble}, to work normally, even on unmapped
10520 code. However, @value{GDBN}'s breakpoint support has some limitations:
10524 @cindex breakpoints in overlays
10525 @cindex overlays, setting breakpoints in
10526 You can set breakpoints in functions in unmapped overlays, as long as
10527 @value{GDBN} can write to the overlay at its load address.
10529 @value{GDBN} can not set hardware or simulator-based breakpoints in
10530 unmapped overlays. However, if you set a breakpoint at the end of your
10531 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10532 you are using manual overlay management), @value{GDBN} will re-set its
10533 breakpoints properly.
10537 @node Automatic Overlay Debugging
10538 @section Automatic Overlay Debugging
10539 @cindex automatic overlay debugging
10541 @value{GDBN} can automatically track which overlays are mapped and which
10542 are not, given some simple co-operation from the overlay manager in the
10543 inferior. If you enable automatic overlay debugging with the
10544 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
10545 looks in the inferior's memory for certain variables describing the
10546 current state of the overlays.
10548 Here are the variables your overlay manager must define to support
10549 @value{GDBN}'s automatic overlay debugging:
10553 @item @code{_ovly_table}:
10554 This variable must be an array of the following structures:
10559 /* The overlay's mapped address. */
10562 /* The size of the overlay, in bytes. */
10563 unsigned long size;
10565 /* The overlay's load address. */
10568 /* Non-zero if the overlay is currently mapped;
10570 unsigned long mapped;
10574 @item @code{_novlys}:
10575 This variable must be a four-byte signed integer, holding the total
10576 number of elements in @code{_ovly_table}.
10580 To decide whether a particular overlay is mapped or not, @value{GDBN}
10581 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
10582 @code{lma} members equal the VMA and LMA of the overlay's section in the
10583 executable file. When @value{GDBN} finds a matching entry, it consults
10584 the entry's @code{mapped} member to determine whether the overlay is
10587 In addition, your overlay manager may define a function called
10588 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
10589 will silently set a breakpoint there. If the overlay manager then
10590 calls this function whenever it has changed the overlay table, this
10591 will enable @value{GDBN} to accurately keep track of which overlays
10592 are in program memory, and update any breakpoints that may be set
10593 in overlays. This will allow breakpoints to work even if the
10594 overlays are kept in ROM or other non-writable memory while they
10595 are not being executed.
10597 @node Overlay Sample Program
10598 @section Overlay Sample Program
10599 @cindex overlay example program
10601 When linking a program which uses overlays, you must place the overlays
10602 at their load addresses, while relocating them to run at their mapped
10603 addresses. To do this, you must write a linker script (@pxref{Overlay
10604 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
10605 since linker scripts are specific to a particular host system, target
10606 architecture, and target memory layout, this manual cannot provide
10607 portable sample code demonstrating @value{GDBN}'s overlay support.
10609 However, the @value{GDBN} source distribution does contain an overlaid
10610 program, with linker scripts for a few systems, as part of its test
10611 suite. The program consists of the following files from
10612 @file{gdb/testsuite/gdb.base}:
10616 The main program file.
10618 A simple overlay manager, used by @file{overlays.c}.
10623 Overlay modules, loaded and used by @file{overlays.c}.
10626 Linker scripts for linking the test program on the @code{d10v-elf}
10627 and @code{m32r-elf} targets.
10630 You can build the test program using the @code{d10v-elf} GCC
10631 cross-compiler like this:
10634 $ d10v-elf-gcc -g -c overlays.c
10635 $ d10v-elf-gcc -g -c ovlymgr.c
10636 $ d10v-elf-gcc -g -c foo.c
10637 $ d10v-elf-gcc -g -c bar.c
10638 $ d10v-elf-gcc -g -c baz.c
10639 $ d10v-elf-gcc -g -c grbx.c
10640 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
10641 baz.o grbx.o -Wl,-Td10v.ld -o overlays
10644 The build process is identical for any other architecture, except that
10645 you must substitute the appropriate compiler and linker script for the
10646 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
10650 @chapter Using @value{GDBN} with Different Languages
10653 Although programming languages generally have common aspects, they are
10654 rarely expressed in the same manner. For instance, in ANSI C,
10655 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
10656 Modula-2, it is accomplished by @code{p^}. Values can also be
10657 represented (and displayed) differently. Hex numbers in C appear as
10658 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
10660 @cindex working language
10661 Language-specific information is built into @value{GDBN} for some languages,
10662 allowing you to express operations like the above in your program's
10663 native language, and allowing @value{GDBN} to output values in a manner
10664 consistent with the syntax of your program's native language. The
10665 language you use to build expressions is called the @dfn{working
10669 * Setting:: Switching between source languages
10670 * Show:: Displaying the language
10671 * Checks:: Type and range checks
10672 * Supported Languages:: Supported languages
10673 * Unsupported Languages:: Unsupported languages
10677 @section Switching Between Source Languages
10679 There are two ways to control the working language---either have @value{GDBN}
10680 set it automatically, or select it manually yourself. You can use the
10681 @code{set language} command for either purpose. On startup, @value{GDBN}
10682 defaults to setting the language automatically. The working language is
10683 used to determine how expressions you type are interpreted, how values
10686 In addition to the working language, every source file that
10687 @value{GDBN} knows about has its own working language. For some object
10688 file formats, the compiler might indicate which language a particular
10689 source file is in. However, most of the time @value{GDBN} infers the
10690 language from the name of the file. The language of a source file
10691 controls whether C@t{++} names are demangled---this way @code{backtrace} can
10692 show each frame appropriately for its own language. There is no way to
10693 set the language of a source file from within @value{GDBN}, but you can
10694 set the language associated with a filename extension. @xref{Show, ,
10695 Displaying the Language}.
10697 This is most commonly a problem when you use a program, such
10698 as @code{cfront} or @code{f2c}, that generates C but is written in
10699 another language. In that case, make the
10700 program use @code{#line} directives in its C output; that way
10701 @value{GDBN} will know the correct language of the source code of the original
10702 program, and will display that source code, not the generated C code.
10705 * Filenames:: Filename extensions and languages.
10706 * Manually:: Setting the working language manually
10707 * Automatically:: Having @value{GDBN} infer the source language
10711 @subsection List of Filename Extensions and Languages
10713 If a source file name ends in one of the following extensions, then
10714 @value{GDBN} infers that its language is the one indicated.
10732 C@t{++} source file
10735 Objective-C source file
10739 Fortran source file
10742 Modula-2 source file
10746 Assembler source file. This actually behaves almost like C, but
10747 @value{GDBN} does not skip over function prologues when stepping.
10750 In addition, you may set the language associated with a filename
10751 extension. @xref{Show, , Displaying the Language}.
10754 @subsection Setting the Working Language
10756 If you allow @value{GDBN} to set the language automatically,
10757 expressions are interpreted the same way in your debugging session and
10760 @kindex set language
10761 If you wish, you may set the language manually. To do this, issue the
10762 command @samp{set language @var{lang}}, where @var{lang} is the name of
10763 a language, such as
10764 @code{c} or @code{modula-2}.
10765 For a list of the supported languages, type @samp{set language}.
10767 Setting the language manually prevents @value{GDBN} from updating the working
10768 language automatically. This can lead to confusion if you try
10769 to debug a program when the working language is not the same as the
10770 source language, when an expression is acceptable to both
10771 languages---but means different things. For instance, if the current
10772 source file were written in C, and @value{GDBN} was parsing Modula-2, a
10780 might not have the effect you intended. In C, this means to add
10781 @code{b} and @code{c} and place the result in @code{a}. The result
10782 printed would be the value of @code{a}. In Modula-2, this means to compare
10783 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
10785 @node Automatically
10786 @subsection Having @value{GDBN} Infer the Source Language
10788 To have @value{GDBN} set the working language automatically, use
10789 @samp{set language local} or @samp{set language auto}. @value{GDBN}
10790 then infers the working language. That is, when your program stops in a
10791 frame (usually by encountering a breakpoint), @value{GDBN} sets the
10792 working language to the language recorded for the function in that
10793 frame. If the language for a frame is unknown (that is, if the function
10794 or block corresponding to the frame was defined in a source file that
10795 does not have a recognized extension), the current working language is
10796 not changed, and @value{GDBN} issues a warning.
10798 This may not seem necessary for most programs, which are written
10799 entirely in one source language. However, program modules and libraries
10800 written in one source language can be used by a main program written in
10801 a different source language. Using @samp{set language auto} in this
10802 case frees you from having to set the working language manually.
10805 @section Displaying the Language
10807 The following commands help you find out which language is the
10808 working language, and also what language source files were written in.
10811 @item show language
10812 @kindex show language
10813 Display the current working language. This is the
10814 language you can use with commands such as @code{print} to
10815 build and compute expressions that may involve variables in your program.
10818 @kindex info frame@r{, show the source language}
10819 Display the source language for this frame. This language becomes the
10820 working language if you use an identifier from this frame.
10821 @xref{Frame Info, ,Information about a Frame}, to identify the other
10822 information listed here.
10825 @kindex info source@r{, show the source language}
10826 Display the source language of this source file.
10827 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
10828 information listed here.
10831 In unusual circumstances, you may have source files with extensions
10832 not in the standard list. You can then set the extension associated
10833 with a language explicitly:
10836 @item set extension-language @var{ext} @var{language}
10837 @kindex set extension-language
10838 Tell @value{GDBN} that source files with extension @var{ext} are to be
10839 assumed as written in the source language @var{language}.
10841 @item info extensions
10842 @kindex info extensions
10843 List all the filename extensions and the associated languages.
10847 @section Type and Range Checking
10850 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
10851 checking are included, but they do not yet have any effect. This
10852 section documents the intended facilities.
10854 @c FIXME remove warning when type/range code added
10856 Some languages are designed to guard you against making seemingly common
10857 errors through a series of compile- and run-time checks. These include
10858 checking the type of arguments to functions and operators, and making
10859 sure mathematical overflows are caught at run time. Checks such as
10860 these help to ensure a program's correctness once it has been compiled
10861 by eliminating type mismatches, and providing active checks for range
10862 errors when your program is running.
10864 @value{GDBN} can check for conditions like the above if you wish.
10865 Although @value{GDBN} does not check the statements in your program,
10866 it can check expressions entered directly into @value{GDBN} for
10867 evaluation via the @code{print} command, for example. As with the
10868 working language, @value{GDBN} can also decide whether or not to check
10869 automatically based on your program's source language.
10870 @xref{Supported Languages, ,Supported Languages}, for the default
10871 settings of supported languages.
10874 * Type Checking:: An overview of type checking
10875 * Range Checking:: An overview of range checking
10878 @cindex type checking
10879 @cindex checks, type
10880 @node Type Checking
10881 @subsection An Overview of Type Checking
10883 Some languages, such as Modula-2, are strongly typed, meaning that the
10884 arguments to operators and functions have to be of the correct type,
10885 otherwise an error occurs. These checks prevent type mismatch
10886 errors from ever causing any run-time problems. For example,
10894 The second example fails because the @code{CARDINAL} 1 is not
10895 type-compatible with the @code{REAL} 2.3.
10897 For the expressions you use in @value{GDBN} commands, you can tell the
10898 @value{GDBN} type checker to skip checking;
10899 to treat any mismatches as errors and abandon the expression;
10900 or to only issue warnings when type mismatches occur,
10901 but evaluate the expression anyway. When you choose the last of
10902 these, @value{GDBN} evaluates expressions like the second example above, but
10903 also issues a warning.
10905 Even if you turn type checking off, there may be other reasons
10906 related to type that prevent @value{GDBN} from evaluating an expression.
10907 For instance, @value{GDBN} does not know how to add an @code{int} and
10908 a @code{struct foo}. These particular type errors have nothing to do
10909 with the language in use, and usually arise from expressions, such as
10910 the one described above, which make little sense to evaluate anyway.
10912 Each language defines to what degree it is strict about type. For
10913 instance, both Modula-2 and C require the arguments to arithmetical
10914 operators to be numbers. In C, enumerated types and pointers can be
10915 represented as numbers, so that they are valid arguments to mathematical
10916 operators. @xref{Supported Languages, ,Supported Languages}, for further
10917 details on specific languages.
10919 @value{GDBN} provides some additional commands for controlling the type checker:
10921 @kindex set check type
10922 @kindex show check type
10924 @item set check type auto
10925 Set type checking on or off based on the current working language.
10926 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10929 @item set check type on
10930 @itemx set check type off
10931 Set type checking on or off, overriding the default setting for the
10932 current working language. Issue a warning if the setting does not
10933 match the language default. If any type mismatches occur in
10934 evaluating an expression while type checking is on, @value{GDBN} prints a
10935 message and aborts evaluation of the expression.
10937 @item set check type warn
10938 Cause the type checker to issue warnings, but to always attempt to
10939 evaluate the expression. Evaluating the expression may still
10940 be impossible for other reasons. For example, @value{GDBN} cannot add
10941 numbers and structures.
10944 Show the current setting of the type checker, and whether or not @value{GDBN}
10945 is setting it automatically.
10948 @cindex range checking
10949 @cindex checks, range
10950 @node Range Checking
10951 @subsection An Overview of Range Checking
10953 In some languages (such as Modula-2), it is an error to exceed the
10954 bounds of a type; this is enforced with run-time checks. Such range
10955 checking is meant to ensure program correctness by making sure
10956 computations do not overflow, or indices on an array element access do
10957 not exceed the bounds of the array.
10959 For expressions you use in @value{GDBN} commands, you can tell
10960 @value{GDBN} to treat range errors in one of three ways: ignore them,
10961 always treat them as errors and abandon the expression, or issue
10962 warnings but evaluate the expression anyway.
10964 A range error can result from numerical overflow, from exceeding an
10965 array index bound, or when you type a constant that is not a member
10966 of any type. Some languages, however, do not treat overflows as an
10967 error. In many implementations of C, mathematical overflow causes the
10968 result to ``wrap around'' to lower values---for example, if @var{m} is
10969 the largest integer value, and @var{s} is the smallest, then
10972 @var{m} + 1 @result{} @var{s}
10975 This, too, is specific to individual languages, and in some cases
10976 specific to individual compilers or machines. @xref{Supported Languages, ,
10977 Supported Languages}, for further details on specific languages.
10979 @value{GDBN} provides some additional commands for controlling the range checker:
10981 @kindex set check range
10982 @kindex show check range
10984 @item set check range auto
10985 Set range checking on or off based on the current working language.
10986 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10989 @item set check range on
10990 @itemx set check range off
10991 Set range checking on or off, overriding the default setting for the
10992 current working language. A warning is issued if the setting does not
10993 match the language default. If a range error occurs and range checking is on,
10994 then a message is printed and evaluation of the expression is aborted.
10996 @item set check range warn
10997 Output messages when the @value{GDBN} range checker detects a range error,
10998 but attempt to evaluate the expression anyway. Evaluating the
10999 expression may still be impossible for other reasons, such as accessing
11000 memory that the process does not own (a typical example from many Unix
11004 Show the current setting of the range checker, and whether or not it is
11005 being set automatically by @value{GDBN}.
11008 @node Supported Languages
11009 @section Supported Languages
11011 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
11012 assembly, Modula-2, and Ada.
11013 @c This is false ...
11014 Some @value{GDBN} features may be used in expressions regardless of the
11015 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11016 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11017 ,Expressions}) can be used with the constructs of any supported
11020 The following sections detail to what degree each source language is
11021 supported by @value{GDBN}. These sections are not meant to be language
11022 tutorials or references, but serve only as a reference guide to what the
11023 @value{GDBN} expression parser accepts, and what input and output
11024 formats should look like for different languages. There are many good
11025 books written on each of these languages; please look to these for a
11026 language reference or tutorial.
11029 * C:: C and C@t{++}
11030 * Objective-C:: Objective-C
11031 * Fortran:: Fortran
11033 * Modula-2:: Modula-2
11038 @subsection C and C@t{++}
11040 @cindex C and C@t{++}
11041 @cindex expressions in C or C@t{++}
11043 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11044 to both languages. Whenever this is the case, we discuss those languages
11048 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11049 @cindex @sc{gnu} C@t{++}
11050 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11051 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11052 effectively, you must compile your C@t{++} programs with a supported
11053 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11054 compiler (@code{aCC}).
11056 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11057 format; if it doesn't work on your system, try the stabs+ debugging
11058 format. You can select those formats explicitly with the @code{g++}
11059 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11060 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11061 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11064 * C Operators:: C and C@t{++} operators
11065 * C Constants:: C and C@t{++} constants
11066 * C Plus Plus Expressions:: C@t{++} expressions
11067 * C Defaults:: Default settings for C and C@t{++}
11068 * C Checks:: C and C@t{++} type and range checks
11069 * Debugging C:: @value{GDBN} and C
11070 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11071 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11075 @subsubsection C and C@t{++} Operators
11077 @cindex C and C@t{++} operators
11079 Operators must be defined on values of specific types. For instance,
11080 @code{+} is defined on numbers, but not on structures. Operators are
11081 often defined on groups of types.
11083 For the purposes of C and C@t{++}, the following definitions hold:
11088 @emph{Integral types} include @code{int} with any of its storage-class
11089 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11092 @emph{Floating-point types} include @code{float}, @code{double}, and
11093 @code{long double} (if supported by the target platform).
11096 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11099 @emph{Scalar types} include all of the above.
11104 The following operators are supported. They are listed here
11105 in order of increasing precedence:
11109 The comma or sequencing operator. Expressions in a comma-separated list
11110 are evaluated from left to right, with the result of the entire
11111 expression being the last expression evaluated.
11114 Assignment. The value of an assignment expression is the value
11115 assigned. Defined on scalar types.
11118 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11119 and translated to @w{@code{@var{a} = @var{a op b}}}.
11120 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11121 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11122 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11125 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11126 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11130 Logical @sc{or}. Defined on integral types.
11133 Logical @sc{and}. Defined on integral types.
11136 Bitwise @sc{or}. Defined on integral types.
11139 Bitwise exclusive-@sc{or}. Defined on integral types.
11142 Bitwise @sc{and}. Defined on integral types.
11145 Equality and inequality. Defined on scalar types. The value of these
11146 expressions is 0 for false and non-zero for true.
11148 @item <@r{, }>@r{, }<=@r{, }>=
11149 Less than, greater than, less than or equal, greater than or equal.
11150 Defined on scalar types. The value of these expressions is 0 for false
11151 and non-zero for true.
11154 left shift, and right shift. Defined on integral types.
11157 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11160 Addition and subtraction. Defined on integral types, floating-point types and
11163 @item *@r{, }/@r{, }%
11164 Multiplication, division, and modulus. Multiplication and division are
11165 defined on integral and floating-point types. Modulus is defined on
11169 Increment and decrement. When appearing before a variable, the
11170 operation is performed before the variable is used in an expression;
11171 when appearing after it, the variable's value is used before the
11172 operation takes place.
11175 Pointer dereferencing. Defined on pointer types. Same precedence as
11179 Address operator. Defined on variables. Same precedence as @code{++}.
11181 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11182 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11183 to examine the address
11184 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11188 Negative. Defined on integral and floating-point types. Same
11189 precedence as @code{++}.
11192 Logical negation. Defined on integral types. Same precedence as
11196 Bitwise complement operator. Defined on integral types. Same precedence as
11201 Structure member, and pointer-to-structure member. For convenience,
11202 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11203 pointer based on the stored type information.
11204 Defined on @code{struct} and @code{union} data.
11207 Dereferences of pointers to members.
11210 Array indexing. @code{@var{a}[@var{i}]} is defined as
11211 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11214 Function parameter list. Same precedence as @code{->}.
11217 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11218 and @code{class} types.
11221 Doubled colons also represent the @value{GDBN} scope operator
11222 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11226 If an operator is redefined in the user code, @value{GDBN} usually
11227 attempts to invoke the redefined version instead of using the operator's
11228 predefined meaning.
11231 @subsubsection C and C@t{++} Constants
11233 @cindex C and C@t{++} constants
11235 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11240 Integer constants are a sequence of digits. Octal constants are
11241 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11242 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11243 @samp{l}, specifying that the constant should be treated as a
11247 Floating point constants are a sequence of digits, followed by a decimal
11248 point, followed by a sequence of digits, and optionally followed by an
11249 exponent. An exponent is of the form:
11250 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11251 sequence of digits. The @samp{+} is optional for positive exponents.
11252 A floating-point constant may also end with a letter @samp{f} or
11253 @samp{F}, specifying that the constant should be treated as being of
11254 the @code{float} (as opposed to the default @code{double}) type; or with
11255 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11259 Enumerated constants consist of enumerated identifiers, or their
11260 integral equivalents.
11263 Character constants are a single character surrounded by single quotes
11264 (@code{'}), or a number---the ordinal value of the corresponding character
11265 (usually its @sc{ascii} value). Within quotes, the single character may
11266 be represented by a letter or by @dfn{escape sequences}, which are of
11267 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11268 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11269 @samp{@var{x}} is a predefined special character---for example,
11270 @samp{\n} for newline.
11273 String constants are a sequence of character constants surrounded by
11274 double quotes (@code{"}). Any valid character constant (as described
11275 above) may appear. Double quotes within the string must be preceded by
11276 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11280 Pointer constants are an integral value. You can also write pointers
11281 to constants using the C operator @samp{&}.
11284 Array constants are comma-separated lists surrounded by braces @samp{@{}
11285 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11286 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11287 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11290 @node C Plus Plus Expressions
11291 @subsubsection C@t{++} Expressions
11293 @cindex expressions in C@t{++}
11294 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11296 @cindex debugging C@t{++} programs
11297 @cindex C@t{++} compilers
11298 @cindex debug formats and C@t{++}
11299 @cindex @value{NGCC} and C@t{++}
11301 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11302 proper compiler and the proper debug format. Currently, @value{GDBN}
11303 works best when debugging C@t{++} code that is compiled with
11304 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11305 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11306 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11307 stabs+ as their default debug format, so you usually don't need to
11308 specify a debug format explicitly. Other compilers and/or debug formats
11309 are likely to work badly or not at all when using @value{GDBN} to debug
11315 @cindex member functions
11317 Member function calls are allowed; you can use expressions like
11320 count = aml->GetOriginal(x, y)
11323 @vindex this@r{, inside C@t{++} member functions}
11324 @cindex namespace in C@t{++}
11326 While a member function is active (in the selected stack frame), your
11327 expressions have the same namespace available as the member function;
11328 that is, @value{GDBN} allows implicit references to the class instance
11329 pointer @code{this} following the same rules as C@t{++}.
11331 @cindex call overloaded functions
11332 @cindex overloaded functions, calling
11333 @cindex type conversions in C@t{++}
11335 You can call overloaded functions; @value{GDBN} resolves the function
11336 call to the right definition, with some restrictions. @value{GDBN} does not
11337 perform overload resolution involving user-defined type conversions,
11338 calls to constructors, or instantiations of templates that do not exist
11339 in the program. It also cannot handle ellipsis argument lists or
11342 It does perform integral conversions and promotions, floating-point
11343 promotions, arithmetic conversions, pointer conversions, conversions of
11344 class objects to base classes, and standard conversions such as those of
11345 functions or arrays to pointers; it requires an exact match on the
11346 number of function arguments.
11348 Overload resolution is always performed, unless you have specified
11349 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11350 ,@value{GDBN} Features for C@t{++}}.
11352 You must specify @code{set overload-resolution off} in order to use an
11353 explicit function signature to call an overloaded function, as in
11355 p 'foo(char,int)'('x', 13)
11358 The @value{GDBN} command-completion facility can simplify this;
11359 see @ref{Completion, ,Command Completion}.
11361 @cindex reference declarations
11363 @value{GDBN} understands variables declared as C@t{++} references; you can use
11364 them in expressions just as you do in C@t{++} source---they are automatically
11367 In the parameter list shown when @value{GDBN} displays a frame, the values of
11368 reference variables are not displayed (unlike other variables); this
11369 avoids clutter, since references are often used for large structures.
11370 The @emph{address} of a reference variable is always shown, unless
11371 you have specified @samp{set print address off}.
11374 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11375 expressions can use it just as expressions in your program do. Since
11376 one scope may be defined in another, you can use @code{::} repeatedly if
11377 necessary, for example in an expression like
11378 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11379 resolving name scope by reference to source files, in both C and C@t{++}
11380 debugging (@pxref{Variables, ,Program Variables}).
11383 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11384 calling virtual functions correctly, printing out virtual bases of
11385 objects, calling functions in a base subobject, casting objects, and
11386 invoking user-defined operators.
11389 @subsubsection C and C@t{++} Defaults
11391 @cindex C and C@t{++} defaults
11393 If you allow @value{GDBN} to set type and range checking automatically, they
11394 both default to @code{off} whenever the working language changes to
11395 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11396 selects the working language.
11398 If you allow @value{GDBN} to set the language automatically, it
11399 recognizes source files whose names end with @file{.c}, @file{.C}, or
11400 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11401 these files, it sets the working language to C or C@t{++}.
11402 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11403 for further details.
11405 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11406 @c unimplemented. If (b) changes, it might make sense to let this node
11407 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11410 @subsubsection C and C@t{++} Type and Range Checks
11412 @cindex C and C@t{++} checks
11414 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11415 is not used. However, if you turn type checking on, @value{GDBN}
11416 considers two variables type equivalent if:
11420 The two variables are structured and have the same structure, union, or
11424 The two variables have the same type name, or types that have been
11425 declared equivalent through @code{typedef}.
11428 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11431 The two @code{struct}, @code{union}, or @code{enum} variables are
11432 declared in the same declaration. (Note: this may not be true for all C
11437 Range checking, if turned on, is done on mathematical operations. Array
11438 indices are not checked, since they are often used to index a pointer
11439 that is not itself an array.
11442 @subsubsection @value{GDBN} and C
11444 The @code{set print union} and @code{show print union} commands apply to
11445 the @code{union} type. When set to @samp{on}, any @code{union} that is
11446 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11447 appears as @samp{@{...@}}.
11449 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11450 with pointers and a memory allocation function. @xref{Expressions,
11453 @node Debugging C Plus Plus
11454 @subsubsection @value{GDBN} Features for C@t{++}
11456 @cindex commands for C@t{++}
11458 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11459 designed specifically for use with C@t{++}. Here is a summary:
11462 @cindex break in overloaded functions
11463 @item @r{breakpoint menus}
11464 When you want a breakpoint in a function whose name is overloaded,
11465 @value{GDBN} has the capability to display a menu of possible breakpoint
11466 locations to help you specify which function definition you want.
11467 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11469 @cindex overloading in C@t{++}
11470 @item rbreak @var{regex}
11471 Setting breakpoints using regular expressions is helpful for setting
11472 breakpoints on overloaded functions that are not members of any special
11474 @xref{Set Breaks, ,Setting Breakpoints}.
11476 @cindex C@t{++} exception handling
11479 Debug C@t{++} exception handling using these commands. @xref{Set
11480 Catchpoints, , Setting Catchpoints}.
11482 @cindex inheritance
11483 @item ptype @var{typename}
11484 Print inheritance relationships as well as other information for type
11486 @xref{Symbols, ,Examining the Symbol Table}.
11488 @cindex C@t{++} symbol display
11489 @item set print demangle
11490 @itemx show print demangle
11491 @itemx set print asm-demangle
11492 @itemx show print asm-demangle
11493 Control whether C@t{++} symbols display in their source form, both when
11494 displaying code as C@t{++} source and when displaying disassemblies.
11495 @xref{Print Settings, ,Print Settings}.
11497 @item set print object
11498 @itemx show print object
11499 Choose whether to print derived (actual) or declared types of objects.
11500 @xref{Print Settings, ,Print Settings}.
11502 @item set print vtbl
11503 @itemx show print vtbl
11504 Control the format for printing virtual function tables.
11505 @xref{Print Settings, ,Print Settings}.
11506 (The @code{vtbl} commands do not work on programs compiled with the HP
11507 ANSI C@t{++} compiler (@code{aCC}).)
11509 @kindex set overload-resolution
11510 @cindex overloaded functions, overload resolution
11511 @item set overload-resolution on
11512 Enable overload resolution for C@t{++} expression evaluation. The default
11513 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11514 and searches for a function whose signature matches the argument types,
11515 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11516 Expressions, ,C@t{++} Expressions}, for details).
11517 If it cannot find a match, it emits a message.
11519 @item set overload-resolution off
11520 Disable overload resolution for C@t{++} expression evaluation. For
11521 overloaded functions that are not class member functions, @value{GDBN}
11522 chooses the first function of the specified name that it finds in the
11523 symbol table, whether or not its arguments are of the correct type. For
11524 overloaded functions that are class member functions, @value{GDBN}
11525 searches for a function whose signature @emph{exactly} matches the
11528 @kindex show overload-resolution
11529 @item show overload-resolution
11530 Show the current setting of overload resolution.
11532 @item @r{Overloaded symbol names}
11533 You can specify a particular definition of an overloaded symbol, using
11534 the same notation that is used to declare such symbols in C@t{++}: type
11535 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
11536 also use the @value{GDBN} command-line word completion facilities to list the
11537 available choices, or to finish the type list for you.
11538 @xref{Completion,, Command Completion}, for details on how to do this.
11541 @node Decimal Floating Point
11542 @subsubsection Decimal Floating Point format
11543 @cindex decimal floating point format
11545 @value{GDBN} can examine, set and perform computations with numbers in
11546 decimal floating point format, which in the C language correspond to the
11547 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
11548 specified by the extension to support decimal floating-point arithmetic.
11550 There are two encodings in use, depending on the architecture: BID (Binary
11551 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
11552 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
11555 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
11556 to manipulate decimal floating point numbers, it is not possible to convert
11557 (using a cast, for example) integers wider than 32-bit to decimal float.
11559 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
11560 point computations, error checking in decimal float operations ignores
11561 underflow, overflow and divide by zero exceptions.
11563 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
11564 to inspect @code{_Decimal128} values stored in floating point registers.
11565 See @ref{PowerPC,,PowerPC} for more details.
11568 @subsection Objective-C
11570 @cindex Objective-C
11571 This section provides information about some commands and command
11572 options that are useful for debugging Objective-C code. See also
11573 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
11574 few more commands specific to Objective-C support.
11577 * Method Names in Commands::
11578 * The Print Command with Objective-C::
11581 @node Method Names in Commands
11582 @subsubsection Method Names in Commands
11584 The following commands have been extended to accept Objective-C method
11585 names as line specifications:
11587 @kindex clear@r{, and Objective-C}
11588 @kindex break@r{, and Objective-C}
11589 @kindex info line@r{, and Objective-C}
11590 @kindex jump@r{, and Objective-C}
11591 @kindex list@r{, and Objective-C}
11595 @item @code{info line}
11600 A fully qualified Objective-C method name is specified as
11603 -[@var{Class} @var{methodName}]
11606 where the minus sign is used to indicate an instance method and a
11607 plus sign (not shown) is used to indicate a class method. The class
11608 name @var{Class} and method name @var{methodName} are enclosed in
11609 brackets, similar to the way messages are specified in Objective-C
11610 source code. For example, to set a breakpoint at the @code{create}
11611 instance method of class @code{Fruit} in the program currently being
11615 break -[Fruit create]
11618 To list ten program lines around the @code{initialize} class method,
11622 list +[NSText initialize]
11625 In the current version of @value{GDBN}, the plus or minus sign is
11626 required. In future versions of @value{GDBN}, the plus or minus
11627 sign will be optional, but you can use it to narrow the search. It
11628 is also possible to specify just a method name:
11634 You must specify the complete method name, including any colons. If
11635 your program's source files contain more than one @code{create} method,
11636 you'll be presented with a numbered list of classes that implement that
11637 method. Indicate your choice by number, or type @samp{0} to exit if
11640 As another example, to clear a breakpoint established at the
11641 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
11644 clear -[NSWindow makeKeyAndOrderFront:]
11647 @node The Print Command with Objective-C
11648 @subsubsection The Print Command With Objective-C
11649 @cindex Objective-C, print objects
11650 @kindex print-object
11651 @kindex po @r{(@code{print-object})}
11653 The print command has also been extended to accept methods. For example:
11656 print -[@var{object} hash]
11659 @cindex print an Objective-C object description
11660 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
11662 will tell @value{GDBN} to send the @code{hash} message to @var{object}
11663 and print the result. Also, an additional command has been added,
11664 @code{print-object} or @code{po} for short, which is meant to print
11665 the description of an object. However, this command may only work
11666 with certain Objective-C libraries that have a particular hook
11667 function, @code{_NSPrintForDebugger}, defined.
11670 @subsection Fortran
11671 @cindex Fortran-specific support in @value{GDBN}
11673 @value{GDBN} can be used to debug programs written in Fortran, but it
11674 currently supports only the features of Fortran 77 language.
11676 @cindex trailing underscore, in Fortran symbols
11677 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
11678 among them) append an underscore to the names of variables and
11679 functions. When you debug programs compiled by those compilers, you
11680 will need to refer to variables and functions with a trailing
11684 * Fortran Operators:: Fortran operators and expressions
11685 * Fortran Defaults:: Default settings for Fortran
11686 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
11689 @node Fortran Operators
11690 @subsubsection Fortran Operators and Expressions
11692 @cindex Fortran operators and expressions
11694 Operators must be defined on values of specific types. For instance,
11695 @code{+} is defined on numbers, but not on characters or other non-
11696 arithmetic types. Operators are often defined on groups of types.
11700 The exponentiation operator. It raises the first operand to the power
11704 The range operator. Normally used in the form of array(low:high) to
11705 represent a section of array.
11708 The access component operator. Normally used to access elements in derived
11709 types. Also suitable for unions. As unions aren't part of regular Fortran,
11710 this can only happen when accessing a register that uses a gdbarch-defined
11714 @node Fortran Defaults
11715 @subsubsection Fortran Defaults
11717 @cindex Fortran Defaults
11719 Fortran symbols are usually case-insensitive, so @value{GDBN} by
11720 default uses case-insensitive matches for Fortran symbols. You can
11721 change that with the @samp{set case-insensitive} command, see
11722 @ref{Symbols}, for the details.
11724 @node Special Fortran Commands
11725 @subsubsection Special Fortran Commands
11727 @cindex Special Fortran commands
11729 @value{GDBN} has some commands to support Fortran-specific features,
11730 such as displaying common blocks.
11733 @cindex @code{COMMON} blocks, Fortran
11734 @kindex info common
11735 @item info common @r{[}@var{common-name}@r{]}
11736 This command prints the values contained in the Fortran @code{COMMON}
11737 block whose name is @var{common-name}. With no argument, the names of
11738 all @code{COMMON} blocks visible at the current program location are
11745 @cindex Pascal support in @value{GDBN}, limitations
11746 Debugging Pascal programs which use sets, subranges, file variables, or
11747 nested functions does not currently work. @value{GDBN} does not support
11748 entering expressions, printing values, or similar features using Pascal
11751 The Pascal-specific command @code{set print pascal_static-members}
11752 controls whether static members of Pascal objects are displayed.
11753 @xref{Print Settings, pascal_static-members}.
11756 @subsection Modula-2
11758 @cindex Modula-2, @value{GDBN} support
11760 The extensions made to @value{GDBN} to support Modula-2 only support
11761 output from the @sc{gnu} Modula-2 compiler (which is currently being
11762 developed). Other Modula-2 compilers are not currently supported, and
11763 attempting to debug executables produced by them is most likely
11764 to give an error as @value{GDBN} reads in the executable's symbol
11767 @cindex expressions in Modula-2
11769 * M2 Operators:: Built-in operators
11770 * Built-In Func/Proc:: Built-in functions and procedures
11771 * M2 Constants:: Modula-2 constants
11772 * M2 Types:: Modula-2 types
11773 * M2 Defaults:: Default settings for Modula-2
11774 * Deviations:: Deviations from standard Modula-2
11775 * M2 Checks:: Modula-2 type and range checks
11776 * M2 Scope:: The scope operators @code{::} and @code{.}
11777 * GDB/M2:: @value{GDBN} and Modula-2
11781 @subsubsection Operators
11782 @cindex Modula-2 operators
11784 Operators must be defined on values of specific types. For instance,
11785 @code{+} is defined on numbers, but not on structures. Operators are
11786 often defined on groups of types. For the purposes of Modula-2, the
11787 following definitions hold:
11792 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
11796 @emph{Character types} consist of @code{CHAR} and its subranges.
11799 @emph{Floating-point types} consist of @code{REAL}.
11802 @emph{Pointer types} consist of anything declared as @code{POINTER TO
11806 @emph{Scalar types} consist of all of the above.
11809 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
11812 @emph{Boolean types} consist of @code{BOOLEAN}.
11816 The following operators are supported, and appear in order of
11817 increasing precedence:
11821 Function argument or array index separator.
11824 Assignment. The value of @var{var} @code{:=} @var{value} is
11828 Less than, greater than on integral, floating-point, or enumerated
11832 Less than or equal to, greater than or equal to
11833 on integral, floating-point and enumerated types, or set inclusion on
11834 set types. Same precedence as @code{<}.
11836 @item =@r{, }<>@r{, }#
11837 Equality and two ways of expressing inequality, valid on scalar types.
11838 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
11839 available for inequality, since @code{#} conflicts with the script
11843 Set membership. Defined on set types and the types of their members.
11844 Same precedence as @code{<}.
11847 Boolean disjunction. Defined on boolean types.
11850 Boolean conjunction. Defined on boolean types.
11853 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11856 Addition and subtraction on integral and floating-point types, or union
11857 and difference on set types.
11860 Multiplication on integral and floating-point types, or set intersection
11864 Division on floating-point types, or symmetric set difference on set
11865 types. Same precedence as @code{*}.
11868 Integer division and remainder. Defined on integral types. Same
11869 precedence as @code{*}.
11872 Negative. Defined on @code{INTEGER} and @code{REAL} data.
11875 Pointer dereferencing. Defined on pointer types.
11878 Boolean negation. Defined on boolean types. Same precedence as
11882 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
11883 precedence as @code{^}.
11886 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
11889 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
11893 @value{GDBN} and Modula-2 scope operators.
11897 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
11898 treats the use of the operator @code{IN}, or the use of operators
11899 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
11900 @code{<=}, and @code{>=} on sets as an error.
11904 @node Built-In Func/Proc
11905 @subsubsection Built-in Functions and Procedures
11906 @cindex Modula-2 built-ins
11908 Modula-2 also makes available several built-in procedures and functions.
11909 In describing these, the following metavariables are used:
11914 represents an @code{ARRAY} variable.
11917 represents a @code{CHAR} constant or variable.
11920 represents a variable or constant of integral type.
11923 represents an identifier that belongs to a set. Generally used in the
11924 same function with the metavariable @var{s}. The type of @var{s} should
11925 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
11928 represents a variable or constant of integral or floating-point type.
11931 represents a variable or constant of floating-point type.
11937 represents a variable.
11940 represents a variable or constant of one of many types. See the
11941 explanation of the function for details.
11944 All Modula-2 built-in procedures also return a result, described below.
11948 Returns the absolute value of @var{n}.
11951 If @var{c} is a lower case letter, it returns its upper case
11952 equivalent, otherwise it returns its argument.
11955 Returns the character whose ordinal value is @var{i}.
11958 Decrements the value in the variable @var{v} by one. Returns the new value.
11960 @item DEC(@var{v},@var{i})
11961 Decrements the value in the variable @var{v} by @var{i}. Returns the
11964 @item EXCL(@var{m},@var{s})
11965 Removes the element @var{m} from the set @var{s}. Returns the new
11968 @item FLOAT(@var{i})
11969 Returns the floating point equivalent of the integer @var{i}.
11971 @item HIGH(@var{a})
11972 Returns the index of the last member of @var{a}.
11975 Increments the value in the variable @var{v} by one. Returns the new value.
11977 @item INC(@var{v},@var{i})
11978 Increments the value in the variable @var{v} by @var{i}. Returns the
11981 @item INCL(@var{m},@var{s})
11982 Adds the element @var{m} to the set @var{s} if it is not already
11983 there. Returns the new set.
11986 Returns the maximum value of the type @var{t}.
11989 Returns the minimum value of the type @var{t}.
11992 Returns boolean TRUE if @var{i} is an odd number.
11995 Returns the ordinal value of its argument. For example, the ordinal
11996 value of a character is its @sc{ascii} value (on machines supporting the
11997 @sc{ascii} character set). @var{x} must be of an ordered type, which include
11998 integral, character and enumerated types.
12000 @item SIZE(@var{x})
12001 Returns the size of its argument. @var{x} can be a variable or a type.
12003 @item TRUNC(@var{r})
12004 Returns the integral part of @var{r}.
12006 @item TSIZE(@var{x})
12007 Returns the size of its argument. @var{x} can be a variable or a type.
12009 @item VAL(@var{t},@var{i})
12010 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12014 @emph{Warning:} Sets and their operations are not yet supported, so
12015 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12019 @cindex Modula-2 constants
12021 @subsubsection Constants
12023 @value{GDBN} allows you to express the constants of Modula-2 in the following
12029 Integer constants are simply a sequence of digits. When used in an
12030 expression, a constant is interpreted to be type-compatible with the
12031 rest of the expression. Hexadecimal integers are specified by a
12032 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12035 Floating point constants appear as a sequence of digits, followed by a
12036 decimal point and another sequence of digits. An optional exponent can
12037 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12038 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12039 digits of the floating point constant must be valid decimal (base 10)
12043 Character constants consist of a single character enclosed by a pair of
12044 like quotes, either single (@code{'}) or double (@code{"}). They may
12045 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12046 followed by a @samp{C}.
12049 String constants consist of a sequence of characters enclosed by a
12050 pair of like quotes, either single (@code{'}) or double (@code{"}).
12051 Escape sequences in the style of C are also allowed. @xref{C
12052 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12056 Enumerated constants consist of an enumerated identifier.
12059 Boolean constants consist of the identifiers @code{TRUE} and
12063 Pointer constants consist of integral values only.
12066 Set constants are not yet supported.
12070 @subsubsection Modula-2 Types
12071 @cindex Modula-2 types
12073 Currently @value{GDBN} can print the following data types in Modula-2
12074 syntax: array types, record types, set types, pointer types, procedure
12075 types, enumerated types, subrange types and base types. You can also
12076 print the contents of variables declared using these type.
12077 This section gives a number of simple source code examples together with
12078 sample @value{GDBN} sessions.
12080 The first example contains the following section of code:
12089 and you can request @value{GDBN} to interrogate the type and value of
12090 @code{r} and @code{s}.
12093 (@value{GDBP}) print s
12095 (@value{GDBP}) ptype s
12097 (@value{GDBP}) print r
12099 (@value{GDBP}) ptype r
12104 Likewise if your source code declares @code{s} as:
12108 s: SET ['A'..'Z'] ;
12112 then you may query the type of @code{s} by:
12115 (@value{GDBP}) ptype s
12116 type = SET ['A'..'Z']
12120 Note that at present you cannot interactively manipulate set
12121 expressions using the debugger.
12123 The following example shows how you might declare an array in Modula-2
12124 and how you can interact with @value{GDBN} to print its type and contents:
12128 s: ARRAY [-10..10] OF CHAR ;
12132 (@value{GDBP}) ptype s
12133 ARRAY [-10..10] OF CHAR
12136 Note that the array handling is not yet complete and although the type
12137 is printed correctly, expression handling still assumes that all
12138 arrays have a lower bound of zero and not @code{-10} as in the example
12141 Here are some more type related Modula-2 examples:
12145 colour = (blue, red, yellow, green) ;
12146 t = [blue..yellow] ;
12154 The @value{GDBN} interaction shows how you can query the data type
12155 and value of a variable.
12158 (@value{GDBP}) print s
12160 (@value{GDBP}) ptype t
12161 type = [blue..yellow]
12165 In this example a Modula-2 array is declared and its contents
12166 displayed. Observe that the contents are written in the same way as
12167 their @code{C} counterparts.
12171 s: ARRAY [1..5] OF CARDINAL ;
12177 (@value{GDBP}) print s
12178 $1 = @{1, 0, 0, 0, 0@}
12179 (@value{GDBP}) ptype s
12180 type = ARRAY [1..5] OF CARDINAL
12183 The Modula-2 language interface to @value{GDBN} also understands
12184 pointer types as shown in this example:
12188 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12195 and you can request that @value{GDBN} describes the type of @code{s}.
12198 (@value{GDBP}) ptype s
12199 type = POINTER TO ARRAY [1..5] OF CARDINAL
12202 @value{GDBN} handles compound types as we can see in this example.
12203 Here we combine array types, record types, pointer types and subrange
12214 myarray = ARRAY myrange OF CARDINAL ;
12215 myrange = [-2..2] ;
12217 s: POINTER TO ARRAY myrange OF foo ;
12221 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12225 (@value{GDBP}) ptype s
12226 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12229 f3 : ARRAY [-2..2] OF CARDINAL;
12234 @subsubsection Modula-2 Defaults
12235 @cindex Modula-2 defaults
12237 If type and range checking are set automatically by @value{GDBN}, they
12238 both default to @code{on} whenever the working language changes to
12239 Modula-2. This happens regardless of whether you or @value{GDBN}
12240 selected the working language.
12242 If you allow @value{GDBN} to set the language automatically, then entering
12243 code compiled from a file whose name ends with @file{.mod} sets the
12244 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12245 Infer the Source Language}, for further details.
12248 @subsubsection Deviations from Standard Modula-2
12249 @cindex Modula-2, deviations from
12251 A few changes have been made to make Modula-2 programs easier to debug.
12252 This is done primarily via loosening its type strictness:
12256 Unlike in standard Modula-2, pointer constants can be formed by
12257 integers. This allows you to modify pointer variables during
12258 debugging. (In standard Modula-2, the actual address contained in a
12259 pointer variable is hidden from you; it can only be modified
12260 through direct assignment to another pointer variable or expression that
12261 returned a pointer.)
12264 C escape sequences can be used in strings and characters to represent
12265 non-printable characters. @value{GDBN} prints out strings with these
12266 escape sequences embedded. Single non-printable characters are
12267 printed using the @samp{CHR(@var{nnn})} format.
12270 The assignment operator (@code{:=}) returns the value of its right-hand
12274 All built-in procedures both modify @emph{and} return their argument.
12278 @subsubsection Modula-2 Type and Range Checks
12279 @cindex Modula-2 checks
12282 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12285 @c FIXME remove warning when type/range checks added
12287 @value{GDBN} considers two Modula-2 variables type equivalent if:
12291 They are of types that have been declared equivalent via a @code{TYPE
12292 @var{t1} = @var{t2}} statement
12295 They have been declared on the same line. (Note: This is true of the
12296 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12299 As long as type checking is enabled, any attempt to combine variables
12300 whose types are not equivalent is an error.
12302 Range checking is done on all mathematical operations, assignment, array
12303 index bounds, and all built-in functions and procedures.
12306 @subsubsection The Scope Operators @code{::} and @code{.}
12308 @cindex @code{.}, Modula-2 scope operator
12309 @cindex colon, doubled as scope operator
12311 @vindex colon-colon@r{, in Modula-2}
12312 @c Info cannot handle :: but TeX can.
12315 @vindex ::@r{, in Modula-2}
12318 There are a few subtle differences between the Modula-2 scope operator
12319 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12324 @var{module} . @var{id}
12325 @var{scope} :: @var{id}
12329 where @var{scope} is the name of a module or a procedure,
12330 @var{module} the name of a module, and @var{id} is any declared
12331 identifier within your program, except another module.
12333 Using the @code{::} operator makes @value{GDBN} search the scope
12334 specified by @var{scope} for the identifier @var{id}. If it is not
12335 found in the specified scope, then @value{GDBN} searches all scopes
12336 enclosing the one specified by @var{scope}.
12338 Using the @code{.} operator makes @value{GDBN} search the current scope for
12339 the identifier specified by @var{id} that was imported from the
12340 definition module specified by @var{module}. With this operator, it is
12341 an error if the identifier @var{id} was not imported from definition
12342 module @var{module}, or if @var{id} is not an identifier in
12346 @subsubsection @value{GDBN} and Modula-2
12348 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12349 Five subcommands of @code{set print} and @code{show print} apply
12350 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12351 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12352 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12353 analogue in Modula-2.
12355 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12356 with any language, is not useful with Modula-2. Its
12357 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12358 created in Modula-2 as they can in C or C@t{++}. However, because an
12359 address can be specified by an integral constant, the construct
12360 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12362 @cindex @code{#} in Modula-2
12363 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12364 interpreted as the beginning of a comment. Use @code{<>} instead.
12370 The extensions made to @value{GDBN} for Ada only support
12371 output from the @sc{gnu} Ada (GNAT) compiler.
12372 Other Ada compilers are not currently supported, and
12373 attempting to debug executables produced by them is most likely
12377 @cindex expressions in Ada
12379 * Ada Mode Intro:: General remarks on the Ada syntax
12380 and semantics supported by Ada mode
12382 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12383 * Additions to Ada:: Extensions of the Ada expression syntax.
12384 * Stopping Before Main Program:: Debugging the program during elaboration.
12385 * Ada Tasks:: Listing and setting breakpoints in tasks.
12386 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12387 * Ada Glitches:: Known peculiarities of Ada mode.
12390 @node Ada Mode Intro
12391 @subsubsection Introduction
12392 @cindex Ada mode, general
12394 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12395 syntax, with some extensions.
12396 The philosophy behind the design of this subset is
12400 That @value{GDBN} should provide basic literals and access to operations for
12401 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12402 leaving more sophisticated computations to subprograms written into the
12403 program (which therefore may be called from @value{GDBN}).
12406 That type safety and strict adherence to Ada language restrictions
12407 are not particularly important to the @value{GDBN} user.
12410 That brevity is important to the @value{GDBN} user.
12413 Thus, for brevity, the debugger acts as if all names declared in
12414 user-written packages are directly visible, even if they are not visible
12415 according to Ada rules, thus making it unnecessary to fully qualify most
12416 names with their packages, regardless of context. Where this causes
12417 ambiguity, @value{GDBN} asks the user's intent.
12419 The debugger will start in Ada mode if it detects an Ada main program.
12420 As for other languages, it will enter Ada mode when stopped in a program that
12421 was translated from an Ada source file.
12423 While in Ada mode, you may use `@t{--}' for comments. This is useful
12424 mostly for documenting command files. The standard @value{GDBN} comment
12425 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12426 middle (to allow based literals).
12428 The debugger supports limited overloading. Given a subprogram call in which
12429 the function symbol has multiple definitions, it will use the number of
12430 actual parameters and some information about their types to attempt to narrow
12431 the set of definitions. It also makes very limited use of context, preferring
12432 procedures to functions in the context of the @code{call} command, and
12433 functions to procedures elsewhere.
12435 @node Omissions from Ada
12436 @subsubsection Omissions from Ada
12437 @cindex Ada, omissions from
12439 Here are the notable omissions from the subset:
12443 Only a subset of the attributes are supported:
12447 @t{'First}, @t{'Last}, and @t{'Length}
12448 on array objects (not on types and subtypes).
12451 @t{'Min} and @t{'Max}.
12454 @t{'Pos} and @t{'Val}.
12460 @t{'Range} on array objects (not subtypes), but only as the right
12461 operand of the membership (@code{in}) operator.
12464 @t{'Access}, @t{'Unchecked_Access}, and
12465 @t{'Unrestricted_Access} (a GNAT extension).
12473 @code{Characters.Latin_1} are not available and
12474 concatenation is not implemented. Thus, escape characters in strings are
12475 not currently available.
12478 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12479 equality of representations. They will generally work correctly
12480 for strings and arrays whose elements have integer or enumeration types.
12481 They may not work correctly for arrays whose element
12482 types have user-defined equality, for arrays of real values
12483 (in particular, IEEE-conformant floating point, because of negative
12484 zeroes and NaNs), and for arrays whose elements contain unused bits with
12485 indeterminate values.
12488 The other component-by-component array operations (@code{and}, @code{or},
12489 @code{xor}, @code{not}, and relational tests other than equality)
12490 are not implemented.
12493 @cindex array aggregates (Ada)
12494 @cindex record aggregates (Ada)
12495 @cindex aggregates (Ada)
12496 There is limited support for array and record aggregates. They are
12497 permitted only on the right sides of assignments, as in these examples:
12500 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12501 (@value{GDBP}) set An_Array := (1, others => 0)
12502 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12503 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12504 (@value{GDBP}) set A_Record := (1, "Peter", True);
12505 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12509 discriminant's value by assigning an aggregate has an
12510 undefined effect if that discriminant is used within the record.
12511 However, you can first modify discriminants by directly assigning to
12512 them (which normally would not be allowed in Ada), and then performing an
12513 aggregate assignment. For example, given a variable @code{A_Rec}
12514 declared to have a type such as:
12517 type Rec (Len : Small_Integer := 0) is record
12519 Vals : IntArray (1 .. Len);
12523 you can assign a value with a different size of @code{Vals} with two
12527 (@value{GDBP}) set A_Rec.Len := 4
12528 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
12531 As this example also illustrates, @value{GDBN} is very loose about the usual
12532 rules concerning aggregates. You may leave out some of the
12533 components of an array or record aggregate (such as the @code{Len}
12534 component in the assignment to @code{A_Rec} above); they will retain their
12535 original values upon assignment. You may freely use dynamic values as
12536 indices in component associations. You may even use overlapping or
12537 redundant component associations, although which component values are
12538 assigned in such cases is not defined.
12541 Calls to dispatching subprograms are not implemented.
12544 The overloading algorithm is much more limited (i.e., less selective)
12545 than that of real Ada. It makes only limited use of the context in
12546 which a subexpression appears to resolve its meaning, and it is much
12547 looser in its rules for allowing type matches. As a result, some
12548 function calls will be ambiguous, and the user will be asked to choose
12549 the proper resolution.
12552 The @code{new} operator is not implemented.
12555 Entry calls are not implemented.
12558 Aside from printing, arithmetic operations on the native VAX floating-point
12559 formats are not supported.
12562 It is not possible to slice a packed array.
12565 The names @code{True} and @code{False}, when not part of a qualified name,
12566 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
12568 Should your program
12569 redefine these names in a package or procedure (at best a dubious practice),
12570 you will have to use fully qualified names to access their new definitions.
12573 @node Additions to Ada
12574 @subsubsection Additions to Ada
12575 @cindex Ada, deviations from
12577 As it does for other languages, @value{GDBN} makes certain generic
12578 extensions to Ada (@pxref{Expressions}):
12582 If the expression @var{E} is a variable residing in memory (typically
12583 a local variable or array element) and @var{N} is a positive integer,
12584 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
12585 @var{N}-1 adjacent variables following it in memory as an array. In
12586 Ada, this operator is generally not necessary, since its prime use is
12587 in displaying parts of an array, and slicing will usually do this in
12588 Ada. However, there are occasional uses when debugging programs in
12589 which certain debugging information has been optimized away.
12592 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
12593 appears in function or file @var{B}.'' When @var{B} is a file name,
12594 you must typically surround it in single quotes.
12597 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
12598 @var{type} that appears at address @var{addr}.''
12601 A name starting with @samp{$} is a convenience variable
12602 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
12605 In addition, @value{GDBN} provides a few other shortcuts and outright
12606 additions specific to Ada:
12610 The assignment statement is allowed as an expression, returning
12611 its right-hand operand as its value. Thus, you may enter
12614 (@value{GDBP}) set x := y + 3
12615 (@value{GDBP}) print A(tmp := y + 1)
12619 The semicolon is allowed as an ``operator,'' returning as its value
12620 the value of its right-hand operand.
12621 This allows, for example,
12622 complex conditional breaks:
12625 (@value{GDBP}) break f
12626 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
12630 Rather than use catenation and symbolic character names to introduce special
12631 characters into strings, one may instead use a special bracket notation,
12632 which is also used to print strings. A sequence of characters of the form
12633 @samp{["@var{XX}"]} within a string or character literal denotes the
12634 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
12635 sequence of characters @samp{["""]} also denotes a single quotation mark
12636 in strings. For example,
12638 "One line.["0a"]Next line.["0a"]"
12641 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
12645 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
12646 @t{'Max} is optional (and is ignored in any case). For example, it is valid
12650 (@value{GDBP}) print 'max(x, y)
12654 When printing arrays, @value{GDBN} uses positional notation when the
12655 array has a lower bound of 1, and uses a modified named notation otherwise.
12656 For example, a one-dimensional array of three integers with a lower bound
12657 of 3 might print as
12664 That is, in contrast to valid Ada, only the first component has a @code{=>}
12668 You may abbreviate attributes in expressions with any unique,
12669 multi-character subsequence of
12670 their names (an exact match gets preference).
12671 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
12672 in place of @t{a'length}.
12675 @cindex quoting Ada internal identifiers
12676 Since Ada is case-insensitive, the debugger normally maps identifiers you type
12677 to lower case. The GNAT compiler uses upper-case characters for
12678 some of its internal identifiers, which are normally of no interest to users.
12679 For the rare occasions when you actually have to look at them,
12680 enclose them in angle brackets to avoid the lower-case mapping.
12683 (@value{GDBP}) print <JMPBUF_SAVE>[0]
12687 Printing an object of class-wide type or dereferencing an
12688 access-to-class-wide value will display all the components of the object's
12689 specific type (as indicated by its run-time tag). Likewise, component
12690 selection on such a value will operate on the specific type of the
12695 @node Stopping Before Main Program
12696 @subsubsection Stopping at the Very Beginning
12698 @cindex breakpointing Ada elaboration code
12699 It is sometimes necessary to debug the program during elaboration, and
12700 before reaching the main procedure.
12701 As defined in the Ada Reference
12702 Manual, the elaboration code is invoked from a procedure called
12703 @code{adainit}. To run your program up to the beginning of
12704 elaboration, simply use the following two commands:
12705 @code{tbreak adainit} and @code{run}.
12708 @subsubsection Extensions for Ada Tasks
12709 @cindex Ada, tasking
12711 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
12712 @value{GDBN} provides the following task-related commands:
12717 This command shows a list of current Ada tasks, as in the following example:
12724 (@value{GDBP}) info tasks
12725 ID TID P-ID Pri State Name
12726 1 8088000 0 15 Child Activation Wait main_task
12727 2 80a4000 1 15 Accept Statement b
12728 3 809a800 1 15 Child Activation Wait a
12729 * 4 80ae800 3 15 Runnable c
12734 In this listing, the asterisk before the last task indicates it to be the
12735 task currently being inspected.
12739 Represents @value{GDBN}'s internal task number.
12745 The parent's task ID (@value{GDBN}'s internal task number).
12748 The base priority of the task.
12751 Current state of the task.
12755 The task has been created but has not been activated. It cannot be
12759 The task is not blocked for any reason known to Ada. (It may be waiting
12760 for a mutex, though.) It is conceptually "executing" in normal mode.
12763 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
12764 that were waiting on terminate alternatives have been awakened and have
12765 terminated themselves.
12767 @item Child Activation Wait
12768 The task is waiting for created tasks to complete activation.
12770 @item Accept Statement
12771 The task is waiting on an accept or selective wait statement.
12773 @item Waiting on entry call
12774 The task is waiting on an entry call.
12776 @item Async Select Wait
12777 The task is waiting to start the abortable part of an asynchronous
12781 The task is waiting on a select statement with only a delay
12784 @item Child Termination Wait
12785 The task is sleeping having completed a master within itself, and is
12786 waiting for the tasks dependent on that master to become terminated or
12787 waiting on a terminate Phase.
12789 @item Wait Child in Term Alt
12790 The task is sleeping waiting for tasks on terminate alternatives to
12791 finish terminating.
12793 @item Accepting RV with @var{taskno}
12794 The task is accepting a rendez-vous with the task @var{taskno}.
12798 Name of the task in the program.
12802 @kindex info task @var{taskno}
12803 @item info task @var{taskno}
12804 This command shows detailled informations on the specified task, as in
12805 the following example:
12810 (@value{GDBP}) info tasks
12811 ID TID P-ID Pri State Name
12812 1 8077880 0 15 Child Activation Wait main_task
12813 * 2 807c468 1 15 Runnable task_1
12814 (@value{GDBP}) info task 2
12815 Ada Task: 0x807c468
12818 Parent: 1 (main_task)
12824 @kindex task@r{ (Ada)}
12825 @cindex current Ada task ID
12826 This command prints the ID of the current task.
12832 (@value{GDBP}) info tasks
12833 ID TID P-ID Pri State Name
12834 1 8077870 0 15 Child Activation Wait main_task
12835 * 2 807c458 1 15 Runnable t
12836 (@value{GDBP}) task
12837 [Current task is 2]
12840 @item task @var{taskno}
12841 @cindex Ada task switching
12842 This command is like the @code{thread @var{threadno}}
12843 command (@pxref{Threads}). It switches the context of debugging
12844 from the current task to the given task.
12850 (@value{GDBP}) info tasks
12851 ID TID P-ID Pri State Name
12852 1 8077870 0 15 Child Activation Wait main_task
12853 * 2 807c458 1 15 Runnable t
12854 (@value{GDBP}) task 1
12855 [Switching to task 1]
12856 #0 0x8067726 in pthread_cond_wait ()
12858 #0 0x8067726 in pthread_cond_wait ()
12859 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
12860 #2 0x805cb63 in system.task_primitives.operations.sleep ()
12861 #3 0x806153e in system.tasking.stages.activate_tasks ()
12862 #4 0x804aacc in un () at un.adb:5
12865 @item break @var{linespec} task @var{taskno}
12866 @itemx break @var{linespec} task @var{taskno} if @dots{}
12867 @cindex breakpoints and tasks, in Ada
12868 @cindex task breakpoints, in Ada
12869 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
12870 These commands are like the @code{break @dots{} thread @dots{}}
12871 command (@pxref{Thread Stops}).
12872 @var{linespec} specifies source lines, as described
12873 in @ref{Specify Location}.
12875 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
12876 to specify that you only want @value{GDBN} to stop the program when a
12877 particular Ada task reaches this breakpoint. @var{taskno} is one of the
12878 numeric task identifiers assigned by @value{GDBN}, shown in the first
12879 column of the @samp{info tasks} display.
12881 If you do not specify @samp{task @var{taskno}} when you set a
12882 breakpoint, the breakpoint applies to @emph{all} tasks of your
12885 You can use the @code{task} qualifier on conditional breakpoints as
12886 well; in this case, place @samp{task @var{taskno}} before the
12887 breakpoint condition (before the @code{if}).
12895 (@value{GDBP}) info tasks
12896 ID TID P-ID Pri State Name
12897 1 140022020 0 15 Child Activation Wait main_task
12898 2 140045060 1 15 Accept/Select Wait t2
12899 3 140044840 1 15 Runnable t1
12900 * 4 140056040 1 15 Runnable t3
12901 (@value{GDBP}) b 15 task 2
12902 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
12903 (@value{GDBP}) cont
12908 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
12910 (@value{GDBP}) info tasks
12911 ID TID P-ID Pri State Name
12912 1 140022020 0 15 Child Activation Wait main_task
12913 * 2 140045060 1 15 Runnable t2
12914 3 140044840 1 15 Runnable t1
12915 4 140056040 1 15 Delay Sleep t3
12919 @node Ada Tasks and Core Files
12920 @subsubsection Tasking Support when Debugging Core Files
12921 @cindex Ada tasking and core file debugging
12923 When inspecting a core file, as opposed to debugging a live program,
12924 tasking support may be limited or even unavailable, depending on
12925 the platform being used.
12926 For instance, on x86-linux, the list of tasks is available, but task
12927 switching is not supported. On Tru64, however, task switching will work
12930 On certain platforms, including Tru64, the debugger needs to perform some
12931 memory writes in order to provide Ada tasking support. When inspecting
12932 a core file, this means that the core file must be opened with read-write
12933 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
12934 Under these circumstances, you should make a backup copy of the core
12935 file before inspecting it with @value{GDBN}.
12938 @subsubsection Known Peculiarities of Ada Mode
12939 @cindex Ada, problems
12941 Besides the omissions listed previously (@pxref{Omissions from Ada}),
12942 we know of several problems with and limitations of Ada mode in
12944 some of which will be fixed with planned future releases of the debugger
12945 and the GNU Ada compiler.
12949 Currently, the debugger
12950 has insufficient information to determine whether certain pointers represent
12951 pointers to objects or the objects themselves.
12952 Thus, the user may have to tack an extra @code{.all} after an expression
12953 to get it printed properly.
12956 Static constants that the compiler chooses not to materialize as objects in
12957 storage are invisible to the debugger.
12960 Named parameter associations in function argument lists are ignored (the
12961 argument lists are treated as positional).
12964 Many useful library packages are currently invisible to the debugger.
12967 Fixed-point arithmetic, conversions, input, and output is carried out using
12968 floating-point arithmetic, and may give results that only approximate those on
12972 The GNAT compiler never generates the prefix @code{Standard} for any of
12973 the standard symbols defined by the Ada language. @value{GDBN} knows about
12974 this: it will strip the prefix from names when you use it, and will never
12975 look for a name you have so qualified among local symbols, nor match against
12976 symbols in other packages or subprograms. If you have
12977 defined entities anywhere in your program other than parameters and
12978 local variables whose simple names match names in @code{Standard},
12979 GNAT's lack of qualification here can cause confusion. When this happens,
12980 you can usually resolve the confusion
12981 by qualifying the problematic names with package
12982 @code{Standard} explicitly.
12985 Older versions of the compiler sometimes generate erroneous debugging
12986 information, resulting in the debugger incorrectly printing the value
12987 of affected entities. In some cases, the debugger is able to work
12988 around an issue automatically. In other cases, the debugger is able
12989 to work around the issue, but the work-around has to be specifically
12992 @kindex set ada trust-PAD-over-XVS
12993 @kindex show ada trust-PAD-over-XVS
12996 @item set ada trust-PAD-over-XVS on
12997 Configure GDB to strictly follow the GNAT encoding when computing the
12998 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
12999 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13000 a complete description of the encoding used by the GNAT compiler).
13001 This is the default.
13003 @item set ada trust-PAD-over-XVS off
13004 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13005 sometimes prints the wrong value for certain entities, changing @code{ada
13006 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13007 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13008 @code{off}, but this incurs a slight performance penalty, so it is
13009 recommended to leave this setting to @code{on} unless necessary.
13013 @node Unsupported Languages
13014 @section Unsupported Languages
13016 @cindex unsupported languages
13017 @cindex minimal language
13018 In addition to the other fully-supported programming languages,
13019 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13020 It does not represent a real programming language, but provides a set
13021 of capabilities close to what the C or assembly languages provide.
13022 This should allow most simple operations to be performed while debugging
13023 an application that uses a language currently not supported by @value{GDBN}.
13025 If the language is set to @code{auto}, @value{GDBN} will automatically
13026 select this language if the current frame corresponds to an unsupported
13030 @chapter Examining the Symbol Table
13032 The commands described in this chapter allow you to inquire about the
13033 symbols (names of variables, functions and types) defined in your
13034 program. This information is inherent in the text of your program and
13035 does not change as your program executes. @value{GDBN} finds it in your
13036 program's symbol table, in the file indicated when you started @value{GDBN}
13037 (@pxref{File Options, ,Choosing Files}), or by one of the
13038 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13040 @cindex symbol names
13041 @cindex names of symbols
13042 @cindex quoting names
13043 Occasionally, you may need to refer to symbols that contain unusual
13044 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13045 most frequent case is in referring to static variables in other
13046 source files (@pxref{Variables,,Program Variables}). File names
13047 are recorded in object files as debugging symbols, but @value{GDBN} would
13048 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13049 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13050 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13057 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13060 @cindex case-insensitive symbol names
13061 @cindex case sensitivity in symbol names
13062 @kindex set case-sensitive
13063 @item set case-sensitive on
13064 @itemx set case-sensitive off
13065 @itemx set case-sensitive auto
13066 Normally, when @value{GDBN} looks up symbols, it matches their names
13067 with case sensitivity determined by the current source language.
13068 Occasionally, you may wish to control that. The command @code{set
13069 case-sensitive} lets you do that by specifying @code{on} for
13070 case-sensitive matches or @code{off} for case-insensitive ones. If
13071 you specify @code{auto}, case sensitivity is reset to the default
13072 suitable for the source language. The default is case-sensitive
13073 matches for all languages except for Fortran, for which the default is
13074 case-insensitive matches.
13076 @kindex show case-sensitive
13077 @item show case-sensitive
13078 This command shows the current setting of case sensitivity for symbols
13081 @kindex info address
13082 @cindex address of a symbol
13083 @item info address @var{symbol}
13084 Describe where the data for @var{symbol} is stored. For a register
13085 variable, this says which register it is kept in. For a non-register
13086 local variable, this prints the stack-frame offset at which the variable
13089 Note the contrast with @samp{print &@var{symbol}}, which does not work
13090 at all for a register variable, and for a stack local variable prints
13091 the exact address of the current instantiation of the variable.
13093 @kindex info symbol
13094 @cindex symbol from address
13095 @cindex closest symbol and offset for an address
13096 @item info symbol @var{addr}
13097 Print the name of a symbol which is stored at the address @var{addr}.
13098 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13099 nearest symbol and an offset from it:
13102 (@value{GDBP}) info symbol 0x54320
13103 _initialize_vx + 396 in section .text
13107 This is the opposite of the @code{info address} command. You can use
13108 it to find out the name of a variable or a function given its address.
13110 For dynamically linked executables, the name of executable or shared
13111 library containing the symbol is also printed:
13114 (@value{GDBP}) info symbol 0x400225
13115 _start + 5 in section .text of /tmp/a.out
13116 (@value{GDBP}) info symbol 0x2aaaac2811cf
13117 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13121 @item whatis [@var{arg}]
13122 Print the data type of @var{arg}, which can be either an expression or
13123 a data type. With no argument, print the data type of @code{$}, the
13124 last value in the value history. If @var{arg} is an expression, it is
13125 not actually evaluated, and any side-effecting operations (such as
13126 assignments or function calls) inside it do not take place. If
13127 @var{arg} is a type name, it may be the name of a type or typedef, or
13128 for C code it may have the form @samp{class @var{class-name}},
13129 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13130 @samp{enum @var{enum-tag}}.
13131 @xref{Expressions, ,Expressions}.
13134 @item ptype [@var{arg}]
13135 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13136 detailed description of the type, instead of just the name of the type.
13137 @xref{Expressions, ,Expressions}.
13139 For example, for this variable declaration:
13142 struct complex @{double real; double imag;@} v;
13146 the two commands give this output:
13150 (@value{GDBP}) whatis v
13151 type = struct complex
13152 (@value{GDBP}) ptype v
13153 type = struct complex @{
13161 As with @code{whatis}, using @code{ptype} without an argument refers to
13162 the type of @code{$}, the last value in the value history.
13164 @cindex incomplete type
13165 Sometimes, programs use opaque data types or incomplete specifications
13166 of complex data structure. If the debug information included in the
13167 program does not allow @value{GDBN} to display a full declaration of
13168 the data type, it will say @samp{<incomplete type>}. For example,
13169 given these declarations:
13173 struct foo *fooptr;
13177 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13180 (@value{GDBP}) ptype foo
13181 $1 = <incomplete type>
13185 ``Incomplete type'' is C terminology for data types that are not
13186 completely specified.
13189 @item info types @var{regexp}
13191 Print a brief description of all types whose names match the regular
13192 expression @var{regexp} (or all types in your program, if you supply
13193 no argument). Each complete typename is matched as though it were a
13194 complete line; thus, @samp{i type value} gives information on all
13195 types in your program whose names include the string @code{value}, but
13196 @samp{i type ^value$} gives information only on types whose complete
13197 name is @code{value}.
13199 This command differs from @code{ptype} in two ways: first, like
13200 @code{whatis}, it does not print a detailed description; second, it
13201 lists all source files where a type is defined.
13204 @cindex local variables
13205 @item info scope @var{location}
13206 List all the variables local to a particular scope. This command
13207 accepts a @var{location} argument---a function name, a source line, or
13208 an address preceded by a @samp{*}, and prints all the variables local
13209 to the scope defined by that location. (@xref{Specify Location}, for
13210 details about supported forms of @var{location}.) For example:
13213 (@value{GDBP}) @b{info scope command_line_handler}
13214 Scope for command_line_handler:
13215 Symbol rl is an argument at stack/frame offset 8, length 4.
13216 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13217 Symbol linelength is in static storage at address 0x150a1c, length 4.
13218 Symbol p is a local variable in register $esi, length 4.
13219 Symbol p1 is a local variable in register $ebx, length 4.
13220 Symbol nline is a local variable in register $edx, length 4.
13221 Symbol repeat is a local variable at frame offset -8, length 4.
13225 This command is especially useful for determining what data to collect
13226 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13229 @kindex info source
13231 Show information about the current source file---that is, the source file for
13232 the function containing the current point of execution:
13235 the name of the source file, and the directory containing it,
13237 the directory it was compiled in,
13239 its length, in lines,
13241 which programming language it is written in,
13243 whether the executable includes debugging information for that file, and
13244 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13246 whether the debugging information includes information about
13247 preprocessor macros.
13251 @kindex info sources
13253 Print the names of all source files in your program for which there is
13254 debugging information, organized into two lists: files whose symbols
13255 have already been read, and files whose symbols will be read when needed.
13257 @kindex info functions
13258 @item info functions
13259 Print the names and data types of all defined functions.
13261 @item info functions @var{regexp}
13262 Print the names and data types of all defined functions
13263 whose names contain a match for regular expression @var{regexp}.
13264 Thus, @samp{info fun step} finds all functions whose names
13265 include @code{step}; @samp{info fun ^step} finds those whose names
13266 start with @code{step}. If a function name contains characters
13267 that conflict with the regular expression language (e.g.@:
13268 @samp{operator*()}), they may be quoted with a backslash.
13270 @kindex info variables
13271 @item info variables
13272 Print the names and data types of all variables that are defined
13273 outside of functions (i.e.@: excluding local variables).
13275 @item info variables @var{regexp}
13276 Print the names and data types of all variables (except for local
13277 variables) whose names contain a match for regular expression
13280 @kindex info classes
13281 @cindex Objective-C, classes and selectors
13283 @itemx info classes @var{regexp}
13284 Display all Objective-C classes in your program, or
13285 (with the @var{regexp} argument) all those matching a particular regular
13288 @kindex info selectors
13289 @item info selectors
13290 @itemx info selectors @var{regexp}
13291 Display all Objective-C selectors in your program, or
13292 (with the @var{regexp} argument) all those matching a particular regular
13296 This was never implemented.
13297 @kindex info methods
13299 @itemx info methods @var{regexp}
13300 The @code{info methods} command permits the user to examine all defined
13301 methods within C@t{++} program, or (with the @var{regexp} argument) a
13302 specific set of methods found in the various C@t{++} classes. Many
13303 C@t{++} classes provide a large number of methods. Thus, the output
13304 from the @code{ptype} command can be overwhelming and hard to use. The
13305 @code{info-methods} command filters the methods, printing only those
13306 which match the regular-expression @var{regexp}.
13309 @cindex reloading symbols
13310 Some systems allow individual object files that make up your program to
13311 be replaced without stopping and restarting your program. For example,
13312 in VxWorks you can simply recompile a defective object file and keep on
13313 running. If you are running on one of these systems, you can allow
13314 @value{GDBN} to reload the symbols for automatically relinked modules:
13317 @kindex set symbol-reloading
13318 @item set symbol-reloading on
13319 Replace symbol definitions for the corresponding source file when an
13320 object file with a particular name is seen again.
13322 @item set symbol-reloading off
13323 Do not replace symbol definitions when encountering object files of the
13324 same name more than once. This is the default state; if you are not
13325 running on a system that permits automatic relinking of modules, you
13326 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
13327 may discard symbols when linking large programs, that may contain
13328 several modules (from different directories or libraries) with the same
13331 @kindex show symbol-reloading
13332 @item show symbol-reloading
13333 Show the current @code{on} or @code{off} setting.
13336 @cindex opaque data types
13337 @kindex set opaque-type-resolution
13338 @item set opaque-type-resolution on
13339 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
13340 declared as a pointer to a @code{struct}, @code{class}, or
13341 @code{union}---for example, @code{struct MyType *}---that is used in one
13342 source file although the full declaration of @code{struct MyType} is in
13343 another source file. The default is on.
13345 A change in the setting of this subcommand will not take effect until
13346 the next time symbols for a file are loaded.
13348 @item set opaque-type-resolution off
13349 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13350 is printed as follows:
13352 @{<no data fields>@}
13355 @kindex show opaque-type-resolution
13356 @item show opaque-type-resolution
13357 Show whether opaque types are resolved or not.
13359 @kindex maint print symbols
13360 @cindex symbol dump
13361 @kindex maint print psymbols
13362 @cindex partial symbol dump
13363 @item maint print symbols @var{filename}
13364 @itemx maint print psymbols @var{filename}
13365 @itemx maint print msymbols @var{filename}
13366 Write a dump of debugging symbol data into the file @var{filename}.
13367 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13368 symbols with debugging data are included. If you use @samp{maint print
13369 symbols}, @value{GDBN} includes all the symbols for which it has already
13370 collected full details: that is, @var{filename} reflects symbols for
13371 only those files whose symbols @value{GDBN} has read. You can use the
13372 command @code{info sources} to find out which files these are. If you
13373 use @samp{maint print psymbols} instead, the dump shows information about
13374 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13375 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13376 @samp{maint print msymbols} dumps just the minimal symbol information
13377 required for each object file from which @value{GDBN} has read some symbols.
13378 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13379 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13381 @kindex maint info symtabs
13382 @kindex maint info psymtabs
13383 @cindex listing @value{GDBN}'s internal symbol tables
13384 @cindex symbol tables, listing @value{GDBN}'s internal
13385 @cindex full symbol tables, listing @value{GDBN}'s internal
13386 @cindex partial symbol tables, listing @value{GDBN}'s internal
13387 @item maint info symtabs @r{[} @var{regexp} @r{]}
13388 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13390 List the @code{struct symtab} or @code{struct partial_symtab}
13391 structures whose names match @var{regexp}. If @var{regexp} is not
13392 given, list them all. The output includes expressions which you can
13393 copy into a @value{GDBN} debugging this one to examine a particular
13394 structure in more detail. For example:
13397 (@value{GDBP}) maint info psymtabs dwarf2read
13398 @{ objfile /home/gnu/build/gdb/gdb
13399 ((struct objfile *) 0x82e69d0)
13400 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13401 ((struct partial_symtab *) 0x8474b10)
13404 text addresses 0x814d3c8 -- 0x8158074
13405 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13406 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13407 dependencies (none)
13410 (@value{GDBP}) maint info symtabs
13414 We see that there is one partial symbol table whose filename contains
13415 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13416 and we see that @value{GDBN} has not read in any symtabs yet at all.
13417 If we set a breakpoint on a function, that will cause @value{GDBN} to
13418 read the symtab for the compilation unit containing that function:
13421 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13422 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13424 (@value{GDBP}) maint info symtabs
13425 @{ objfile /home/gnu/build/gdb/gdb
13426 ((struct objfile *) 0x82e69d0)
13427 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13428 ((struct symtab *) 0x86c1f38)
13431 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13432 linetable ((struct linetable *) 0x8370fa0)
13433 debugformat DWARF 2
13442 @chapter Altering Execution
13444 Once you think you have found an error in your program, you might want to
13445 find out for certain whether correcting the apparent error would lead to
13446 correct results in the rest of the run. You can find the answer by
13447 experiment, using the @value{GDBN} features for altering execution of the
13450 For example, you can store new values into variables or memory
13451 locations, give your program a signal, restart it at a different
13452 address, or even return prematurely from a function.
13455 * Assignment:: Assignment to variables
13456 * Jumping:: Continuing at a different address
13457 * Signaling:: Giving your program a signal
13458 * Returning:: Returning from a function
13459 * Calling:: Calling your program's functions
13460 * Patching:: Patching your program
13464 @section Assignment to Variables
13467 @cindex setting variables
13468 To alter the value of a variable, evaluate an assignment expression.
13469 @xref{Expressions, ,Expressions}. For example,
13476 stores the value 4 into the variable @code{x}, and then prints the
13477 value of the assignment expression (which is 4).
13478 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13479 information on operators in supported languages.
13481 @kindex set variable
13482 @cindex variables, setting
13483 If you are not interested in seeing the value of the assignment, use the
13484 @code{set} command instead of the @code{print} command. @code{set} is
13485 really the same as @code{print} except that the expression's value is
13486 not printed and is not put in the value history (@pxref{Value History,
13487 ,Value History}). The expression is evaluated only for its effects.
13489 If the beginning of the argument string of the @code{set} command
13490 appears identical to a @code{set} subcommand, use the @code{set
13491 variable} command instead of just @code{set}. This command is identical
13492 to @code{set} except for its lack of subcommands. For example, if your
13493 program has a variable @code{width}, you get an error if you try to set
13494 a new value with just @samp{set width=13}, because @value{GDBN} has the
13495 command @code{set width}:
13498 (@value{GDBP}) whatis width
13500 (@value{GDBP}) p width
13502 (@value{GDBP}) set width=47
13503 Invalid syntax in expression.
13507 The invalid expression, of course, is @samp{=47}. In
13508 order to actually set the program's variable @code{width}, use
13511 (@value{GDBP}) set var width=47
13514 Because the @code{set} command has many subcommands that can conflict
13515 with the names of program variables, it is a good idea to use the
13516 @code{set variable} command instead of just @code{set}. For example, if
13517 your program has a variable @code{g}, you run into problems if you try
13518 to set a new value with just @samp{set g=4}, because @value{GDBN} has
13519 the command @code{set gnutarget}, abbreviated @code{set g}:
13523 (@value{GDBP}) whatis g
13527 (@value{GDBP}) set g=4
13531 The program being debugged has been started already.
13532 Start it from the beginning? (y or n) y
13533 Starting program: /home/smith/cc_progs/a.out
13534 "/home/smith/cc_progs/a.out": can't open to read symbols:
13535 Invalid bfd target.
13536 (@value{GDBP}) show g
13537 The current BFD target is "=4".
13542 The program variable @code{g} did not change, and you silently set the
13543 @code{gnutarget} to an invalid value. In order to set the variable
13547 (@value{GDBP}) set var g=4
13550 @value{GDBN} allows more implicit conversions in assignments than C; you can
13551 freely store an integer value into a pointer variable or vice versa,
13552 and you can convert any structure to any other structure that is the
13553 same length or shorter.
13554 @comment FIXME: how do structs align/pad in these conversions?
13555 @comment /doc@cygnus.com 18dec1990
13557 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
13558 construct to generate a value of specified type at a specified address
13559 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
13560 to memory location @code{0x83040} as an integer (which implies a certain size
13561 and representation in memory), and
13564 set @{int@}0x83040 = 4
13568 stores the value 4 into that memory location.
13571 @section Continuing at a Different Address
13573 Ordinarily, when you continue your program, you do so at the place where
13574 it stopped, with the @code{continue} command. You can instead continue at
13575 an address of your own choosing, with the following commands:
13579 @item jump @var{linespec}
13580 @itemx jump @var{location}
13581 Resume execution at line @var{linespec} or at address given by
13582 @var{location}. Execution stops again immediately if there is a
13583 breakpoint there. @xref{Specify Location}, for a description of the
13584 different forms of @var{linespec} and @var{location}. It is common
13585 practice to use the @code{tbreak} command in conjunction with
13586 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
13588 The @code{jump} command does not change the current stack frame, or
13589 the stack pointer, or the contents of any memory location or any
13590 register other than the program counter. If line @var{linespec} is in
13591 a different function from the one currently executing, the results may
13592 be bizarre if the two functions expect different patterns of arguments or
13593 of local variables. For this reason, the @code{jump} command requests
13594 confirmation if the specified line is not in the function currently
13595 executing. However, even bizarre results are predictable if you are
13596 well acquainted with the machine-language code of your program.
13599 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
13600 On many systems, you can get much the same effect as the @code{jump}
13601 command by storing a new value into the register @code{$pc}. The
13602 difference is that this does not start your program running; it only
13603 changes the address of where it @emph{will} run when you continue. For
13611 makes the next @code{continue} command or stepping command execute at
13612 address @code{0x485}, rather than at the address where your program stopped.
13613 @xref{Continuing and Stepping, ,Continuing and Stepping}.
13615 The most common occasion to use the @code{jump} command is to back
13616 up---perhaps with more breakpoints set---over a portion of a program
13617 that has already executed, in order to examine its execution in more
13622 @section Giving your Program a Signal
13623 @cindex deliver a signal to a program
13627 @item signal @var{signal}
13628 Resume execution where your program stopped, but immediately give it the
13629 signal @var{signal}. @var{signal} can be the name or the number of a
13630 signal. For example, on many systems @code{signal 2} and @code{signal
13631 SIGINT} are both ways of sending an interrupt signal.
13633 Alternatively, if @var{signal} is zero, continue execution without
13634 giving a signal. This is useful when your program stopped on account of
13635 a signal and would ordinary see the signal when resumed with the
13636 @code{continue} command; @samp{signal 0} causes it to resume without a
13639 @code{signal} does not repeat when you press @key{RET} a second time
13640 after executing the command.
13644 Invoking the @code{signal} command is not the same as invoking the
13645 @code{kill} utility from the shell. Sending a signal with @code{kill}
13646 causes @value{GDBN} to decide what to do with the signal depending on
13647 the signal handling tables (@pxref{Signals}). The @code{signal} command
13648 passes the signal directly to your program.
13652 @section Returning from a Function
13655 @cindex returning from a function
13658 @itemx return @var{expression}
13659 You can cancel execution of a function call with the @code{return}
13660 command. If you give an
13661 @var{expression} argument, its value is used as the function's return
13665 When you use @code{return}, @value{GDBN} discards the selected stack frame
13666 (and all frames within it). You can think of this as making the
13667 discarded frame return prematurely. If you wish to specify a value to
13668 be returned, give that value as the argument to @code{return}.
13670 This pops the selected stack frame (@pxref{Selection, ,Selecting a
13671 Frame}), and any other frames inside of it, leaving its caller as the
13672 innermost remaining frame. That frame becomes selected. The
13673 specified value is stored in the registers used for returning values
13676 The @code{return} command does not resume execution; it leaves the
13677 program stopped in the state that would exist if the function had just
13678 returned. In contrast, the @code{finish} command (@pxref{Continuing
13679 and Stepping, ,Continuing and Stepping}) resumes execution until the
13680 selected stack frame returns naturally.
13682 @value{GDBN} needs to know how the @var{expression} argument should be set for
13683 the inferior. The concrete registers assignment depends on the OS ABI and the
13684 type being returned by the selected stack frame. For example it is common for
13685 OS ABI to return floating point values in FPU registers while integer values in
13686 CPU registers. Still some ABIs return even floating point values in CPU
13687 registers. Larger integer widths (such as @code{long long int}) also have
13688 specific placement rules. @value{GDBN} already knows the OS ABI from its
13689 current target so it needs to find out also the type being returned to make the
13690 assignment into the right register(s).
13692 Normally, the selected stack frame has debug info. @value{GDBN} will always
13693 use the debug info instead of the implicit type of @var{expression} when the
13694 debug info is available. For example, if you type @kbd{return -1}, and the
13695 function in the current stack frame is declared to return a @code{long long
13696 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
13697 into a @code{long long int}:
13700 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
13702 (@value{GDBP}) return -1
13703 Make func return now? (y or n) y
13704 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
13705 43 printf ("result=%lld\n", func ());
13709 However, if the selected stack frame does not have a debug info, e.g., if the
13710 function was compiled without debug info, @value{GDBN} has to find out the type
13711 to return from user. Specifying a different type by mistake may set the value
13712 in different inferior registers than the caller code expects. For example,
13713 typing @kbd{return -1} with its implicit type @code{int} would set only a part
13714 of a @code{long long int} result for a debug info less function (on 32-bit
13715 architectures). Therefore the user is required to specify the return type by
13716 an appropriate cast explicitly:
13719 Breakpoint 2, 0x0040050b in func ()
13720 (@value{GDBP}) return -1
13721 Return value type not available for selected stack frame.
13722 Please use an explicit cast of the value to return.
13723 (@value{GDBP}) return (long long int) -1
13724 Make selected stack frame return now? (y or n) y
13725 #0 0x00400526 in main ()
13730 @section Calling Program Functions
13733 @cindex calling functions
13734 @cindex inferior functions, calling
13735 @item print @var{expr}
13736 Evaluate the expression @var{expr} and display the resulting value.
13737 @var{expr} may include calls to functions in the program being
13741 @item call @var{expr}
13742 Evaluate the expression @var{expr} without displaying @code{void}
13745 You can use this variant of the @code{print} command if you want to
13746 execute a function from your program that does not return anything
13747 (a.k.a.@: @dfn{a void function}), but without cluttering the output
13748 with @code{void} returned values that @value{GDBN} will otherwise
13749 print. If the result is not void, it is printed and saved in the
13753 It is possible for the function you call via the @code{print} or
13754 @code{call} command to generate a signal (e.g., if there's a bug in
13755 the function, or if you passed it incorrect arguments). What happens
13756 in that case is controlled by the @code{set unwindonsignal} command.
13758 Similarly, with a C@t{++} program it is possible for the function you
13759 call via the @code{print} or @code{call} command to generate an
13760 exception that is not handled due to the constraints of the dummy
13761 frame. In this case, any exception that is raised in the frame, but has
13762 an out-of-frame exception handler will not be found. GDB builds a
13763 dummy-frame for the inferior function call, and the unwinder cannot
13764 seek for exception handlers outside of this dummy-frame. What happens
13765 in that case is controlled by the
13766 @code{set unwind-on-terminating-exception} command.
13769 @item set unwindonsignal
13770 @kindex set unwindonsignal
13771 @cindex unwind stack in called functions
13772 @cindex call dummy stack unwinding
13773 Set unwinding of the stack if a signal is received while in a function
13774 that @value{GDBN} called in the program being debugged. If set to on,
13775 @value{GDBN} unwinds the stack it created for the call and restores
13776 the context to what it was before the call. If set to off (the
13777 default), @value{GDBN} stops in the frame where the signal was
13780 @item show unwindonsignal
13781 @kindex show unwindonsignal
13782 Show the current setting of stack unwinding in the functions called by
13785 @item set unwind-on-terminating-exception
13786 @kindex set unwind-on-terminating-exception
13787 @cindex unwind stack in called functions with unhandled exceptions
13788 @cindex call dummy stack unwinding on unhandled exception.
13789 Set unwinding of the stack if a C@t{++} exception is raised, but left
13790 unhandled while in a function that @value{GDBN} called in the program being
13791 debugged. If set to on (the default), @value{GDBN} unwinds the stack
13792 it created for the call and restores the context to what it was before
13793 the call. If set to off, @value{GDBN} the exception is delivered to
13794 the default C@t{++} exception handler and the inferior terminated.
13796 @item show unwind-on-terminating-exception
13797 @kindex show unwind-on-terminating-exception
13798 Show the current setting of stack unwinding in the functions called by
13803 @cindex weak alias functions
13804 Sometimes, a function you wish to call is actually a @dfn{weak alias}
13805 for another function. In such case, @value{GDBN} might not pick up
13806 the type information, including the types of the function arguments,
13807 which causes @value{GDBN} to call the inferior function incorrectly.
13808 As a result, the called function will function erroneously and may
13809 even crash. A solution to that is to use the name of the aliased
13813 @section Patching Programs
13815 @cindex patching binaries
13816 @cindex writing into executables
13817 @cindex writing into corefiles
13819 By default, @value{GDBN} opens the file containing your program's
13820 executable code (or the corefile) read-only. This prevents accidental
13821 alterations to machine code; but it also prevents you from intentionally
13822 patching your program's binary.
13824 If you'd like to be able to patch the binary, you can specify that
13825 explicitly with the @code{set write} command. For example, you might
13826 want to turn on internal debugging flags, or even to make emergency
13832 @itemx set write off
13833 If you specify @samp{set write on}, @value{GDBN} opens executable and
13834 core files for both reading and writing; if you specify @kbd{set write
13835 off} (the default), @value{GDBN} opens them read-only.
13837 If you have already loaded a file, you must load it again (using the
13838 @code{exec-file} or @code{core-file} command) after changing @code{set
13839 write}, for your new setting to take effect.
13843 Display whether executable files and core files are opened for writing
13844 as well as reading.
13848 @chapter @value{GDBN} Files
13850 @value{GDBN} needs to know the file name of the program to be debugged,
13851 both in order to read its symbol table and in order to start your
13852 program. To debug a core dump of a previous run, you must also tell
13853 @value{GDBN} the name of the core dump file.
13856 * Files:: Commands to specify files
13857 * Separate Debug Files:: Debugging information in separate files
13858 * Symbol Errors:: Errors reading symbol files
13859 * Data Files:: GDB data files
13863 @section Commands to Specify Files
13865 @cindex symbol table
13866 @cindex core dump file
13868 You may want to specify executable and core dump file names. The usual
13869 way to do this is at start-up time, using the arguments to
13870 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
13871 Out of @value{GDBN}}).
13873 Occasionally it is necessary to change to a different file during a
13874 @value{GDBN} session. Or you may run @value{GDBN} and forget to
13875 specify a file you want to use. Or you are debugging a remote target
13876 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
13877 Program}). In these situations the @value{GDBN} commands to specify
13878 new files are useful.
13881 @cindex executable file
13883 @item file @var{filename}
13884 Use @var{filename} as the program to be debugged. It is read for its
13885 symbols and for the contents of pure memory. It is also the program
13886 executed when you use the @code{run} command. If you do not specify a
13887 directory and the file is not found in the @value{GDBN} working directory,
13888 @value{GDBN} uses the environment variable @code{PATH} as a list of
13889 directories to search, just as the shell does when looking for a program
13890 to run. You can change the value of this variable, for both @value{GDBN}
13891 and your program, using the @code{path} command.
13893 @cindex unlinked object files
13894 @cindex patching object files
13895 You can load unlinked object @file{.o} files into @value{GDBN} using
13896 the @code{file} command. You will not be able to ``run'' an object
13897 file, but you can disassemble functions and inspect variables. Also,
13898 if the underlying BFD functionality supports it, you could use
13899 @kbd{gdb -write} to patch object files using this technique. Note
13900 that @value{GDBN} can neither interpret nor modify relocations in this
13901 case, so branches and some initialized variables will appear to go to
13902 the wrong place. But this feature is still handy from time to time.
13905 @code{file} with no argument makes @value{GDBN} discard any information it
13906 has on both executable file and the symbol table.
13909 @item exec-file @r{[} @var{filename} @r{]}
13910 Specify that the program to be run (but not the symbol table) is found
13911 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
13912 if necessary to locate your program. Omitting @var{filename} means to
13913 discard information on the executable file.
13915 @kindex symbol-file
13916 @item symbol-file @r{[} @var{filename} @r{]}
13917 Read symbol table information from file @var{filename}. @code{PATH} is
13918 searched when necessary. Use the @code{file} command to get both symbol
13919 table and program to run from the same file.
13921 @code{symbol-file} with no argument clears out @value{GDBN} information on your
13922 program's symbol table.
13924 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
13925 some breakpoints and auto-display expressions. This is because they may
13926 contain pointers to the internal data recording symbols and data types,
13927 which are part of the old symbol table data being discarded inside
13930 @code{symbol-file} does not repeat if you press @key{RET} again after
13933 When @value{GDBN} is configured for a particular environment, it
13934 understands debugging information in whatever format is the standard
13935 generated for that environment; you may use either a @sc{gnu} compiler, or
13936 other compilers that adhere to the local conventions.
13937 Best results are usually obtained from @sc{gnu} compilers; for example,
13938 using @code{@value{NGCC}} you can generate debugging information for
13941 For most kinds of object files, with the exception of old SVR3 systems
13942 using COFF, the @code{symbol-file} command does not normally read the
13943 symbol table in full right away. Instead, it scans the symbol table
13944 quickly to find which source files and which symbols are present. The
13945 details are read later, one source file at a time, as they are needed.
13947 The purpose of this two-stage reading strategy is to make @value{GDBN}
13948 start up faster. For the most part, it is invisible except for
13949 occasional pauses while the symbol table details for a particular source
13950 file are being read. (The @code{set verbose} command can turn these
13951 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
13952 Warnings and Messages}.)
13954 We have not implemented the two-stage strategy for COFF yet. When the
13955 symbol table is stored in COFF format, @code{symbol-file} reads the
13956 symbol table data in full right away. Note that ``stabs-in-COFF''
13957 still does the two-stage strategy, since the debug info is actually
13961 @cindex reading symbols immediately
13962 @cindex symbols, reading immediately
13963 @item symbol-file @r{[} -readnow @r{]} @var{filename}
13964 @itemx file @r{[} -readnow @r{]} @var{filename}
13965 You can override the @value{GDBN} two-stage strategy for reading symbol
13966 tables by using the @samp{-readnow} option with any of the commands that
13967 load symbol table information, if you want to be sure @value{GDBN} has the
13968 entire symbol table available.
13970 @c FIXME: for now no mention of directories, since this seems to be in
13971 @c flux. 13mar1992 status is that in theory GDB would look either in
13972 @c current dir or in same dir as myprog; but issues like competing
13973 @c GDB's, or clutter in system dirs, mean that in practice right now
13974 @c only current dir is used. FFish says maybe a special GDB hierarchy
13975 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
13979 @item core-file @r{[}@var{filename}@r{]}
13981 Specify the whereabouts of a core dump file to be used as the ``contents
13982 of memory''. Traditionally, core files contain only some parts of the
13983 address space of the process that generated them; @value{GDBN} can access the
13984 executable file itself for other parts.
13986 @code{core-file} with no argument specifies that no core file is
13989 Note that the core file is ignored when your program is actually running
13990 under @value{GDBN}. So, if you have been running your program and you
13991 wish to debug a core file instead, you must kill the subprocess in which
13992 the program is running. To do this, use the @code{kill} command
13993 (@pxref{Kill Process, ,Killing the Child Process}).
13995 @kindex add-symbol-file
13996 @cindex dynamic linking
13997 @item add-symbol-file @var{filename} @var{address}
13998 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
13999 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14000 The @code{add-symbol-file} command reads additional symbol table
14001 information from the file @var{filename}. You would use this command
14002 when @var{filename} has been dynamically loaded (by some other means)
14003 into the program that is running. @var{address} should be the memory
14004 address at which the file has been loaded; @value{GDBN} cannot figure
14005 this out for itself. You can additionally specify an arbitrary number
14006 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14007 section name and base address for that section. You can specify any
14008 @var{address} as an expression.
14010 The symbol table of the file @var{filename} is added to the symbol table
14011 originally read with the @code{symbol-file} command. You can use the
14012 @code{add-symbol-file} command any number of times; the new symbol data
14013 thus read keeps adding to the old. To discard all old symbol data
14014 instead, use the @code{symbol-file} command without any arguments.
14016 @cindex relocatable object files, reading symbols from
14017 @cindex object files, relocatable, reading symbols from
14018 @cindex reading symbols from relocatable object files
14019 @cindex symbols, reading from relocatable object files
14020 @cindex @file{.o} files, reading symbols from
14021 Although @var{filename} is typically a shared library file, an
14022 executable file, or some other object file which has been fully
14023 relocated for loading into a process, you can also load symbolic
14024 information from relocatable @file{.o} files, as long as:
14028 the file's symbolic information refers only to linker symbols defined in
14029 that file, not to symbols defined by other object files,
14031 every section the file's symbolic information refers to has actually
14032 been loaded into the inferior, as it appears in the file, and
14034 you can determine the address at which every section was loaded, and
14035 provide these to the @code{add-symbol-file} command.
14039 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14040 relocatable files into an already running program; such systems
14041 typically make the requirements above easy to meet. However, it's
14042 important to recognize that many native systems use complex link
14043 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14044 assembly, for example) that make the requirements difficult to meet. In
14045 general, one cannot assume that using @code{add-symbol-file} to read a
14046 relocatable object file's symbolic information will have the same effect
14047 as linking the relocatable object file into the program in the normal
14050 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14052 @kindex add-symbol-file-from-memory
14053 @cindex @code{syscall DSO}
14054 @cindex load symbols from memory
14055 @item add-symbol-file-from-memory @var{address}
14056 Load symbols from the given @var{address} in a dynamically loaded
14057 object file whose image is mapped directly into the inferior's memory.
14058 For example, the Linux kernel maps a @code{syscall DSO} into each
14059 process's address space; this DSO provides kernel-specific code for
14060 some system calls. The argument can be any expression whose
14061 evaluation yields the address of the file's shared object file header.
14062 For this command to work, you must have used @code{symbol-file} or
14063 @code{exec-file} commands in advance.
14065 @kindex add-shared-symbol-files
14067 @item add-shared-symbol-files @var{library-file}
14068 @itemx assf @var{library-file}
14069 The @code{add-shared-symbol-files} command can currently be used only
14070 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14071 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14072 @value{GDBN} automatically looks for shared libraries, however if
14073 @value{GDBN} does not find yours, you can invoke
14074 @code{add-shared-symbol-files}. It takes one argument: the shared
14075 library's file name. @code{assf} is a shorthand alias for
14076 @code{add-shared-symbol-files}.
14079 @item section @var{section} @var{addr}
14080 The @code{section} command changes the base address of the named
14081 @var{section} of the exec file to @var{addr}. This can be used if the
14082 exec file does not contain section addresses, (such as in the
14083 @code{a.out} format), or when the addresses specified in the file
14084 itself are wrong. Each section must be changed separately. The
14085 @code{info files} command, described below, lists all the sections and
14089 @kindex info target
14092 @code{info files} and @code{info target} are synonymous; both print the
14093 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14094 including the names of the executable and core dump files currently in
14095 use by @value{GDBN}, and the files from which symbols were loaded. The
14096 command @code{help target} lists all possible targets rather than
14099 @kindex maint info sections
14100 @item maint info sections
14101 Another command that can give you extra information about program sections
14102 is @code{maint info sections}. In addition to the section information
14103 displayed by @code{info files}, this command displays the flags and file
14104 offset of each section in the executable and core dump files. In addition,
14105 @code{maint info sections} provides the following command options (which
14106 may be arbitrarily combined):
14110 Display sections for all loaded object files, including shared libraries.
14111 @item @var{sections}
14112 Display info only for named @var{sections}.
14113 @item @var{section-flags}
14114 Display info only for sections for which @var{section-flags} are true.
14115 The section flags that @value{GDBN} currently knows about are:
14118 Section will have space allocated in the process when loaded.
14119 Set for all sections except those containing debug information.
14121 Section will be loaded from the file into the child process memory.
14122 Set for pre-initialized code and data, clear for @code{.bss} sections.
14124 Section needs to be relocated before loading.
14126 Section cannot be modified by the child process.
14128 Section contains executable code only.
14130 Section contains data only (no executable code).
14132 Section will reside in ROM.
14134 Section contains data for constructor/destructor lists.
14136 Section is not empty.
14138 An instruction to the linker to not output the section.
14139 @item COFF_SHARED_LIBRARY
14140 A notification to the linker that the section contains
14141 COFF shared library information.
14143 Section contains common symbols.
14146 @kindex set trust-readonly-sections
14147 @cindex read-only sections
14148 @item set trust-readonly-sections on
14149 Tell @value{GDBN} that readonly sections in your object file
14150 really are read-only (i.e.@: that their contents will not change).
14151 In that case, @value{GDBN} can fetch values from these sections
14152 out of the object file, rather than from the target program.
14153 For some targets (notably embedded ones), this can be a significant
14154 enhancement to debugging performance.
14156 The default is off.
14158 @item set trust-readonly-sections off
14159 Tell @value{GDBN} not to trust readonly sections. This means that
14160 the contents of the section might change while the program is running,
14161 and must therefore be fetched from the target when needed.
14163 @item show trust-readonly-sections
14164 Show the current setting of trusting readonly sections.
14167 All file-specifying commands allow both absolute and relative file names
14168 as arguments. @value{GDBN} always converts the file name to an absolute file
14169 name and remembers it that way.
14171 @cindex shared libraries
14172 @anchor{Shared Libraries}
14173 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14174 and IBM RS/6000 AIX shared libraries.
14176 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14177 shared libraries. @xref{Expat}.
14179 @value{GDBN} automatically loads symbol definitions from shared libraries
14180 when you use the @code{run} command, or when you examine a core file.
14181 (Before you issue the @code{run} command, @value{GDBN} does not understand
14182 references to a function in a shared library, however---unless you are
14183 debugging a core file).
14185 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14186 automatically loads the symbols at the time of the @code{shl_load} call.
14188 @c FIXME: some @value{GDBN} release may permit some refs to undef
14189 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14190 @c FIXME...lib; check this from time to time when updating manual
14192 There are times, however, when you may wish to not automatically load
14193 symbol definitions from shared libraries, such as when they are
14194 particularly large or there are many of them.
14196 To control the automatic loading of shared library symbols, use the
14200 @kindex set auto-solib-add
14201 @item set auto-solib-add @var{mode}
14202 If @var{mode} is @code{on}, symbols from all shared object libraries
14203 will be loaded automatically when the inferior begins execution, you
14204 attach to an independently started inferior, or when the dynamic linker
14205 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14206 is @code{off}, symbols must be loaded manually, using the
14207 @code{sharedlibrary} command. The default value is @code{on}.
14209 @cindex memory used for symbol tables
14210 If your program uses lots of shared libraries with debug info that
14211 takes large amounts of memory, you can decrease the @value{GDBN}
14212 memory footprint by preventing it from automatically loading the
14213 symbols from shared libraries. To that end, type @kbd{set
14214 auto-solib-add off} before running the inferior, then load each
14215 library whose debug symbols you do need with @kbd{sharedlibrary
14216 @var{regexp}}, where @var{regexp} is a regular expression that matches
14217 the libraries whose symbols you want to be loaded.
14219 @kindex show auto-solib-add
14220 @item show auto-solib-add
14221 Display the current autoloading mode.
14224 @cindex load shared library
14225 To explicitly load shared library symbols, use the @code{sharedlibrary}
14229 @kindex info sharedlibrary
14231 @item info share @var{regex}
14232 @itemx info sharedlibrary @var{regex}
14233 Print the names of the shared libraries which are currently loaded
14234 that match @var{regex}. If @var{regex} is omitted then print
14235 all shared libraries that are loaded.
14237 @kindex sharedlibrary
14239 @item sharedlibrary @var{regex}
14240 @itemx share @var{regex}
14241 Load shared object library symbols for files matching a
14242 Unix regular expression.
14243 As with files loaded automatically, it only loads shared libraries
14244 required by your program for a core file or after typing @code{run}. If
14245 @var{regex} is omitted all shared libraries required by your program are
14248 @item nosharedlibrary
14249 @kindex nosharedlibrary
14250 @cindex unload symbols from shared libraries
14251 Unload all shared object library symbols. This discards all symbols
14252 that have been loaded from all shared libraries. Symbols from shared
14253 libraries that were loaded by explicit user requests are not
14257 Sometimes you may wish that @value{GDBN} stops and gives you control
14258 when any of shared library events happen. Use the @code{set
14259 stop-on-solib-events} command for this:
14262 @item set stop-on-solib-events
14263 @kindex set stop-on-solib-events
14264 This command controls whether @value{GDBN} should give you control
14265 when the dynamic linker notifies it about some shared library event.
14266 The most common event of interest is loading or unloading of a new
14269 @item show stop-on-solib-events
14270 @kindex show stop-on-solib-events
14271 Show whether @value{GDBN} stops and gives you control when shared
14272 library events happen.
14275 Shared libraries are also supported in many cross or remote debugging
14276 configurations. @value{GDBN} needs to have access to the target's libraries;
14277 this can be accomplished either by providing copies of the libraries
14278 on the host system, or by asking @value{GDBN} to automatically retrieve the
14279 libraries from the target. If copies of the target libraries are
14280 provided, they need to be the same as the target libraries, although the
14281 copies on the target can be stripped as long as the copies on the host are
14284 @cindex where to look for shared libraries
14285 For remote debugging, you need to tell @value{GDBN} where the target
14286 libraries are, so that it can load the correct copies---otherwise, it
14287 may try to load the host's libraries. @value{GDBN} has two variables
14288 to specify the search directories for target libraries.
14291 @cindex prefix for shared library file names
14292 @cindex system root, alternate
14293 @kindex set solib-absolute-prefix
14294 @kindex set sysroot
14295 @item set sysroot @var{path}
14296 Use @var{path} as the system root for the program being debugged. Any
14297 absolute shared library paths will be prefixed with @var{path}; many
14298 runtime loaders store the absolute paths to the shared library in the
14299 target program's memory. If you use @code{set sysroot} to find shared
14300 libraries, they need to be laid out in the same way that they are on
14301 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
14304 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
14305 retrieve the target libraries from the remote system. This is only
14306 supported when using a remote target that supports the @code{remote get}
14307 command (@pxref{File Transfer,,Sending files to a remote system}).
14308 The part of @var{path} following the initial @file{remote:}
14309 (if present) is used as system root prefix on the remote file system.
14310 @footnote{If you want to specify a local system root using a directory
14311 that happens to be named @file{remote:}, you need to use some equivalent
14312 variant of the name like @file{./remote:}.}
14314 The @code{set solib-absolute-prefix} command is an alias for @code{set
14317 @cindex default system root
14318 @cindex @samp{--with-sysroot}
14319 You can set the default system root by using the configure-time
14320 @samp{--with-sysroot} option. If the system root is inside
14321 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14322 @samp{--exec-prefix}), then the default system root will be updated
14323 automatically if the installed @value{GDBN} is moved to a new
14326 @kindex show sysroot
14328 Display the current shared library prefix.
14330 @kindex set solib-search-path
14331 @item set solib-search-path @var{path}
14332 If this variable is set, @var{path} is a colon-separated list of
14333 directories to search for shared libraries. @samp{solib-search-path}
14334 is used after @samp{sysroot} fails to locate the library, or if the
14335 path to the library is relative instead of absolute. If you want to
14336 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
14337 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
14338 finding your host's libraries. @samp{sysroot} is preferred; setting
14339 it to a nonexistent directory may interfere with automatic loading
14340 of shared library symbols.
14342 @kindex show solib-search-path
14343 @item show solib-search-path
14344 Display the current shared library search path.
14348 @node Separate Debug Files
14349 @section Debugging Information in Separate Files
14350 @cindex separate debugging information files
14351 @cindex debugging information in separate files
14352 @cindex @file{.debug} subdirectories
14353 @cindex debugging information directory, global
14354 @cindex global debugging information directory
14355 @cindex build ID, and separate debugging files
14356 @cindex @file{.build-id} directory
14358 @value{GDBN} allows you to put a program's debugging information in a
14359 file separate from the executable itself, in a way that allows
14360 @value{GDBN} to find and load the debugging information automatically.
14361 Since debugging information can be very large---sometimes larger
14362 than the executable code itself---some systems distribute debugging
14363 information for their executables in separate files, which users can
14364 install only when they need to debug a problem.
14366 @value{GDBN} supports two ways of specifying the separate debug info
14371 The executable contains a @dfn{debug link} that specifies the name of
14372 the separate debug info file. The separate debug file's name is
14373 usually @file{@var{executable}.debug}, where @var{executable} is the
14374 name of the corresponding executable file without leading directories
14375 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14376 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14377 checksum for the debug file, which @value{GDBN} uses to validate that
14378 the executable and the debug file came from the same build.
14381 The executable contains a @dfn{build ID}, a unique bit string that is
14382 also present in the corresponding debug info file. (This is supported
14383 only on some operating systems, notably those which use the ELF format
14384 for binary files and the @sc{gnu} Binutils.) For more details about
14385 this feature, see the description of the @option{--build-id}
14386 command-line option in @ref{Options, , Command Line Options, ld.info,
14387 The GNU Linker}. The debug info file's name is not specified
14388 explicitly by the build ID, but can be computed from the build ID, see
14392 Depending on the way the debug info file is specified, @value{GDBN}
14393 uses two different methods of looking for the debug file:
14397 For the ``debug link'' method, @value{GDBN} looks up the named file in
14398 the directory of the executable file, then in a subdirectory of that
14399 directory named @file{.debug}, and finally under the global debug
14400 directory, in a subdirectory whose name is identical to the leading
14401 directories of the executable's absolute file name.
14404 For the ``build ID'' method, @value{GDBN} looks in the
14405 @file{.build-id} subdirectory of the global debug directory for a file
14406 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
14407 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
14408 are the rest of the bit string. (Real build ID strings are 32 or more
14409 hex characters, not 10.)
14412 So, for example, suppose you ask @value{GDBN} to debug
14413 @file{/usr/bin/ls}, which has a debug link that specifies the
14414 file @file{ls.debug}, and a build ID whose value in hex is
14415 @code{abcdef1234}. If the global debug directory is
14416 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
14417 debug information files, in the indicated order:
14421 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
14423 @file{/usr/bin/ls.debug}
14425 @file{/usr/bin/.debug/ls.debug}
14427 @file{/usr/lib/debug/usr/bin/ls.debug}.
14430 You can set the global debugging info directory's name, and view the
14431 name @value{GDBN} is currently using.
14435 @kindex set debug-file-directory
14436 @item set debug-file-directory @var{directories}
14437 Set the directories which @value{GDBN} searches for separate debugging
14438 information files to @var{directory}. Multiple directory components can be set
14439 concatenating them by a directory separator.
14441 @kindex show debug-file-directory
14442 @item show debug-file-directory
14443 Show the directories @value{GDBN} searches for separate debugging
14448 @cindex @code{.gnu_debuglink} sections
14449 @cindex debug link sections
14450 A debug link is a special section of the executable file named
14451 @code{.gnu_debuglink}. The section must contain:
14455 A filename, with any leading directory components removed, followed by
14458 zero to three bytes of padding, as needed to reach the next four-byte
14459 boundary within the section, and
14461 a four-byte CRC checksum, stored in the same endianness used for the
14462 executable file itself. The checksum is computed on the debugging
14463 information file's full contents by the function given below, passing
14464 zero as the @var{crc} argument.
14467 Any executable file format can carry a debug link, as long as it can
14468 contain a section named @code{.gnu_debuglink} with the contents
14471 @cindex @code{.note.gnu.build-id} sections
14472 @cindex build ID sections
14473 The build ID is a special section in the executable file (and in other
14474 ELF binary files that @value{GDBN} may consider). This section is
14475 often named @code{.note.gnu.build-id}, but that name is not mandatory.
14476 It contains unique identification for the built files---the ID remains
14477 the same across multiple builds of the same build tree. The default
14478 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
14479 content for the build ID string. The same section with an identical
14480 value is present in the original built binary with symbols, in its
14481 stripped variant, and in the separate debugging information file.
14483 The debugging information file itself should be an ordinary
14484 executable, containing a full set of linker symbols, sections, and
14485 debugging information. The sections of the debugging information file
14486 should have the same names, addresses, and sizes as the original file,
14487 but they need not contain any data---much like a @code{.bss} section
14488 in an ordinary executable.
14490 The @sc{gnu} binary utilities (Binutils) package includes the
14491 @samp{objcopy} utility that can produce
14492 the separated executable / debugging information file pairs using the
14493 following commands:
14496 @kbd{objcopy --only-keep-debug foo foo.debug}
14501 These commands remove the debugging
14502 information from the executable file @file{foo} and place it in the file
14503 @file{foo.debug}. You can use the first, second or both methods to link the
14508 The debug link method needs the following additional command to also leave
14509 behind a debug link in @file{foo}:
14512 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
14515 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
14516 a version of the @code{strip} command such that the command @kbd{strip foo -f
14517 foo.debug} has the same functionality as the two @code{objcopy} commands and
14518 the @code{ln -s} command above, together.
14521 Build ID gets embedded into the main executable using @code{ld --build-id} or
14522 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
14523 compatibility fixes for debug files separation are present in @sc{gnu} binary
14524 utilities (Binutils) package since version 2.18.
14529 @cindex CRC algorithm definition
14530 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
14531 IEEE 802.3 using the polynomial:
14533 @c TexInfo requires naked braces for multi-digit exponents for Tex
14534 @c output, but this causes HTML output to barf. HTML has to be set using
14535 @c raw commands. So we end up having to specify this equation in 2
14540 <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>
14541 + <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
14547 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
14548 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
14552 The function is computed byte at a time, taking the least
14553 significant bit of each byte first. The initial pattern
14554 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
14555 the final result is inverted to ensure trailing zeros also affect the
14558 @emph{Note:} This is the same CRC polynomial as used in handling the
14559 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
14560 , @value{GDBN} Remote Serial Protocol}). However in the
14561 case of the Remote Serial Protocol, the CRC is computed @emph{most}
14562 significant bit first, and the result is not inverted, so trailing
14563 zeros have no effect on the CRC value.
14565 To complete the description, we show below the code of the function
14566 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
14567 initially supplied @code{crc} argument means that an initial call to
14568 this function passing in zero will start computing the CRC using
14571 @kindex gnu_debuglink_crc32
14574 gnu_debuglink_crc32 (unsigned long crc,
14575 unsigned char *buf, size_t len)
14577 static const unsigned long crc32_table[256] =
14579 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
14580 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
14581 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
14582 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
14583 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
14584 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
14585 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
14586 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
14587 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
14588 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
14589 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
14590 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
14591 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
14592 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
14593 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
14594 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
14595 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
14596 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
14597 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
14598 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
14599 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
14600 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
14601 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
14602 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
14603 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
14604 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
14605 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
14606 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
14607 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
14608 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
14609 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
14610 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
14611 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
14612 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
14613 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
14614 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
14615 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
14616 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
14617 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
14618 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
14619 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
14620 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
14621 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
14622 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
14623 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
14624 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
14625 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
14626 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
14627 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
14628 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
14629 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
14632 unsigned char *end;
14634 crc = ~crc & 0xffffffff;
14635 for (end = buf + len; buf < end; ++buf)
14636 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
14637 return ~crc & 0xffffffff;
14642 This computation does not apply to the ``build ID'' method.
14645 @node Symbol Errors
14646 @section Errors Reading Symbol Files
14648 While reading a symbol file, @value{GDBN} occasionally encounters problems,
14649 such as symbol types it does not recognize, or known bugs in compiler
14650 output. By default, @value{GDBN} does not notify you of such problems, since
14651 they are relatively common and primarily of interest to people
14652 debugging compilers. If you are interested in seeing information
14653 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
14654 only one message about each such type of problem, no matter how many
14655 times the problem occurs; or you can ask @value{GDBN} to print more messages,
14656 to see how many times the problems occur, with the @code{set
14657 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
14660 The messages currently printed, and their meanings, include:
14663 @item inner block not inside outer block in @var{symbol}
14665 The symbol information shows where symbol scopes begin and end
14666 (such as at the start of a function or a block of statements). This
14667 error indicates that an inner scope block is not fully contained
14668 in its outer scope blocks.
14670 @value{GDBN} circumvents the problem by treating the inner block as if it had
14671 the same scope as the outer block. In the error message, @var{symbol}
14672 may be shown as ``@code{(don't know)}'' if the outer block is not a
14675 @item block at @var{address} out of order
14677 The symbol information for symbol scope blocks should occur in
14678 order of increasing addresses. This error indicates that it does not
14681 @value{GDBN} does not circumvent this problem, and has trouble
14682 locating symbols in the source file whose symbols it is reading. (You
14683 can often determine what source file is affected by specifying
14684 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
14687 @item bad block start address patched
14689 The symbol information for a symbol scope block has a start address
14690 smaller than the address of the preceding source line. This is known
14691 to occur in the SunOS 4.1.1 (and earlier) C compiler.
14693 @value{GDBN} circumvents the problem by treating the symbol scope block as
14694 starting on the previous source line.
14696 @item bad string table offset in symbol @var{n}
14699 Symbol number @var{n} contains a pointer into the string table which is
14700 larger than the size of the string table.
14702 @value{GDBN} circumvents the problem by considering the symbol to have the
14703 name @code{foo}, which may cause other problems if many symbols end up
14706 @item unknown symbol type @code{0x@var{nn}}
14708 The symbol information contains new data types that @value{GDBN} does
14709 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
14710 uncomprehended information, in hexadecimal.
14712 @value{GDBN} circumvents the error by ignoring this symbol information.
14713 This usually allows you to debug your program, though certain symbols
14714 are not accessible. If you encounter such a problem and feel like
14715 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
14716 on @code{complain}, then go up to the function @code{read_dbx_symtab}
14717 and examine @code{*bufp} to see the symbol.
14719 @item stub type has NULL name
14721 @value{GDBN} could not find the full definition for a struct or class.
14723 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
14724 The symbol information for a C@t{++} member function is missing some
14725 information that recent versions of the compiler should have output for
14728 @item info mismatch between compiler and debugger
14730 @value{GDBN} could not parse a type specification output by the compiler.
14735 @section GDB Data Files
14737 @cindex prefix for data files
14738 @value{GDBN} will sometimes read an auxiliary data file. These files
14739 are kept in a directory known as the @dfn{data directory}.
14741 You can set the data directory's name, and view the name @value{GDBN}
14742 is currently using.
14745 @kindex set data-directory
14746 @item set data-directory @var{directory}
14747 Set the directory which @value{GDBN} searches for auxiliary data files
14748 to @var{directory}.
14750 @kindex show data-directory
14751 @item show data-directory
14752 Show the directory @value{GDBN} searches for auxiliary data files.
14755 @cindex default data directory
14756 @cindex @samp{--with-gdb-datadir}
14757 You can set the default data directory by using the configure-time
14758 @samp{--with-gdb-datadir} option. If the data directory is inside
14759 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14760 @samp{--exec-prefix}), then the default data directory will be updated
14761 automatically if the installed @value{GDBN} is moved to a new
14765 @chapter Specifying a Debugging Target
14767 @cindex debugging target
14768 A @dfn{target} is the execution environment occupied by your program.
14770 Often, @value{GDBN} runs in the same host environment as your program;
14771 in that case, the debugging target is specified as a side effect when
14772 you use the @code{file} or @code{core} commands. When you need more
14773 flexibility---for example, running @value{GDBN} on a physically separate
14774 host, or controlling a standalone system over a serial port or a
14775 realtime system over a TCP/IP connection---you can use the @code{target}
14776 command to specify one of the target types configured for @value{GDBN}
14777 (@pxref{Target Commands, ,Commands for Managing Targets}).
14779 @cindex target architecture
14780 It is possible to build @value{GDBN} for several different @dfn{target
14781 architectures}. When @value{GDBN} is built like that, you can choose
14782 one of the available architectures with the @kbd{set architecture}
14786 @kindex set architecture
14787 @kindex show architecture
14788 @item set architecture @var{arch}
14789 This command sets the current target architecture to @var{arch}. The
14790 value of @var{arch} can be @code{"auto"}, in addition to one of the
14791 supported architectures.
14793 @item show architecture
14794 Show the current target architecture.
14796 @item set processor
14798 @kindex set processor
14799 @kindex show processor
14800 These are alias commands for, respectively, @code{set architecture}
14801 and @code{show architecture}.
14805 * Active Targets:: Active targets
14806 * Target Commands:: Commands for managing targets
14807 * Byte Order:: Choosing target byte order
14810 @node Active Targets
14811 @section Active Targets
14813 @cindex stacking targets
14814 @cindex active targets
14815 @cindex multiple targets
14817 There are three classes of targets: processes, core files, and
14818 executable files. @value{GDBN} can work concurrently on up to three
14819 active targets, one in each class. This allows you to (for example)
14820 start a process and inspect its activity without abandoning your work on
14823 For example, if you execute @samp{gdb a.out}, then the executable file
14824 @code{a.out} is the only active target. If you designate a core file as
14825 well---presumably from a prior run that crashed and coredumped---then
14826 @value{GDBN} has two active targets and uses them in tandem, looking
14827 first in the corefile target, then in the executable file, to satisfy
14828 requests for memory addresses. (Typically, these two classes of target
14829 are complementary, since core files contain only a program's
14830 read-write memory---variables and so on---plus machine status, while
14831 executable files contain only the program text and initialized data.)
14833 When you type @code{run}, your executable file becomes an active process
14834 target as well. When a process target is active, all @value{GDBN}
14835 commands requesting memory addresses refer to that target; addresses in
14836 an active core file or executable file target are obscured while the
14837 process target is active.
14839 Use the @code{core-file} and @code{exec-file} commands to select a new
14840 core file or executable target (@pxref{Files, ,Commands to Specify
14841 Files}). To specify as a target a process that is already running, use
14842 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
14845 @node Target Commands
14846 @section Commands for Managing Targets
14849 @item target @var{type} @var{parameters}
14850 Connects the @value{GDBN} host environment to a target machine or
14851 process. A target is typically a protocol for talking to debugging
14852 facilities. You use the argument @var{type} to specify the type or
14853 protocol of the target machine.
14855 Further @var{parameters} are interpreted by the target protocol, but
14856 typically include things like device names or host names to connect
14857 with, process numbers, and baud rates.
14859 The @code{target} command does not repeat if you press @key{RET} again
14860 after executing the command.
14862 @kindex help target
14864 Displays the names of all targets available. To display targets
14865 currently selected, use either @code{info target} or @code{info files}
14866 (@pxref{Files, ,Commands to Specify Files}).
14868 @item help target @var{name}
14869 Describe a particular target, including any parameters necessary to
14872 @kindex set gnutarget
14873 @item set gnutarget @var{args}
14874 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
14875 knows whether it is reading an @dfn{executable},
14876 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
14877 with the @code{set gnutarget} command. Unlike most @code{target} commands,
14878 with @code{gnutarget} the @code{target} refers to a program, not a machine.
14881 @emph{Warning:} To specify a file format with @code{set gnutarget},
14882 you must know the actual BFD name.
14886 @xref{Files, , Commands to Specify Files}.
14888 @kindex show gnutarget
14889 @item show gnutarget
14890 Use the @code{show gnutarget} command to display what file format
14891 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
14892 @value{GDBN} will determine the file format for each file automatically,
14893 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
14896 @cindex common targets
14897 Here are some common targets (available, or not, depending on the GDB
14902 @item target exec @var{program}
14903 @cindex executable file target
14904 An executable file. @samp{target exec @var{program}} is the same as
14905 @samp{exec-file @var{program}}.
14907 @item target core @var{filename}
14908 @cindex core dump file target
14909 A core dump file. @samp{target core @var{filename}} is the same as
14910 @samp{core-file @var{filename}}.
14912 @item target remote @var{medium}
14913 @cindex remote target
14914 A remote system connected to @value{GDBN} via a serial line or network
14915 connection. This command tells @value{GDBN} to use its own remote
14916 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
14918 For example, if you have a board connected to @file{/dev/ttya} on the
14919 machine running @value{GDBN}, you could say:
14922 target remote /dev/ttya
14925 @code{target remote} supports the @code{load} command. This is only
14926 useful if you have some other way of getting the stub to the target
14927 system, and you can put it somewhere in memory where it won't get
14928 clobbered by the download.
14930 @item target sim @r{[}@var{simargs}@r{]} @dots{}
14931 @cindex built-in simulator target
14932 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
14940 works; however, you cannot assume that a specific memory map, device
14941 drivers, or even basic I/O is available, although some simulators do
14942 provide these. For info about any processor-specific simulator details,
14943 see the appropriate section in @ref{Embedded Processors, ,Embedded
14948 Some configurations may include these targets as well:
14952 @item target nrom @var{dev}
14953 @cindex NetROM ROM emulator target
14954 NetROM ROM emulator. This target only supports downloading.
14958 Different targets are available on different configurations of @value{GDBN};
14959 your configuration may have more or fewer targets.
14961 Many remote targets require you to download the executable's code once
14962 you've successfully established a connection. You may wish to control
14963 various aspects of this process.
14968 @kindex set hash@r{, for remote monitors}
14969 @cindex hash mark while downloading
14970 This command controls whether a hash mark @samp{#} is displayed while
14971 downloading a file to the remote monitor. If on, a hash mark is
14972 displayed after each S-record is successfully downloaded to the
14976 @kindex show hash@r{, for remote monitors}
14977 Show the current status of displaying the hash mark.
14979 @item set debug monitor
14980 @kindex set debug monitor
14981 @cindex display remote monitor communications
14982 Enable or disable display of communications messages between
14983 @value{GDBN} and the remote monitor.
14985 @item show debug monitor
14986 @kindex show debug monitor
14987 Show the current status of displaying communications between
14988 @value{GDBN} and the remote monitor.
14993 @kindex load @var{filename}
14994 @item load @var{filename}
14996 Depending on what remote debugging facilities are configured into
14997 @value{GDBN}, the @code{load} command may be available. Where it exists, it
14998 is meant to make @var{filename} (an executable) available for debugging
14999 on the remote system---by downloading, or dynamic linking, for example.
15000 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15001 the @code{add-symbol-file} command.
15003 If your @value{GDBN} does not have a @code{load} command, attempting to
15004 execute it gets the error message ``@code{You can't do that when your
15005 target is @dots{}}''
15007 The file is loaded at whatever address is specified in the executable.
15008 For some object file formats, you can specify the load address when you
15009 link the program; for other formats, like a.out, the object file format
15010 specifies a fixed address.
15011 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15013 Depending on the remote side capabilities, @value{GDBN} may be able to
15014 load programs into flash memory.
15016 @code{load} does not repeat if you press @key{RET} again after using it.
15020 @section Choosing Target Byte Order
15022 @cindex choosing target byte order
15023 @cindex target byte order
15025 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15026 offer the ability to run either big-endian or little-endian byte
15027 orders. Usually the executable or symbol will include a bit to
15028 designate the endian-ness, and you will not need to worry about
15029 which to use. However, you may still find it useful to adjust
15030 @value{GDBN}'s idea of processor endian-ness manually.
15034 @item set endian big
15035 Instruct @value{GDBN} to assume the target is big-endian.
15037 @item set endian little
15038 Instruct @value{GDBN} to assume the target is little-endian.
15040 @item set endian auto
15041 Instruct @value{GDBN} to use the byte order associated with the
15045 Display @value{GDBN}'s current idea of the target byte order.
15049 Note that these commands merely adjust interpretation of symbolic
15050 data on the host, and that they have absolutely no effect on the
15054 @node Remote Debugging
15055 @chapter Debugging Remote Programs
15056 @cindex remote debugging
15058 If you are trying to debug a program running on a machine that cannot run
15059 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15060 For example, you might use remote debugging on an operating system kernel,
15061 or on a small system which does not have a general purpose operating system
15062 powerful enough to run a full-featured debugger.
15064 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15065 to make this work with particular debugging targets. In addition,
15066 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15067 but not specific to any particular target system) which you can use if you
15068 write the remote stubs---the code that runs on the remote system to
15069 communicate with @value{GDBN}.
15071 Other remote targets may be available in your
15072 configuration of @value{GDBN}; use @code{help target} to list them.
15075 * Connecting:: Connecting to a remote target
15076 * File Transfer:: Sending files to a remote system
15077 * Server:: Using the gdbserver program
15078 * Remote Configuration:: Remote configuration
15079 * Remote Stub:: Implementing a remote stub
15083 @section Connecting to a Remote Target
15085 On the @value{GDBN} host machine, you will need an unstripped copy of
15086 your program, since @value{GDBN} needs symbol and debugging information.
15087 Start up @value{GDBN} as usual, using the name of the local copy of your
15088 program as the first argument.
15090 @cindex @code{target remote}
15091 @value{GDBN} can communicate with the target over a serial line, or
15092 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15093 each case, @value{GDBN} uses the same protocol for debugging your
15094 program; only the medium carrying the debugging packets varies. The
15095 @code{target remote} command establishes a connection to the target.
15096 Its arguments indicate which medium to use:
15100 @item target remote @var{serial-device}
15101 @cindex serial line, @code{target remote}
15102 Use @var{serial-device} to communicate with the target. For example,
15103 to use a serial line connected to the device named @file{/dev/ttyb}:
15106 target remote /dev/ttyb
15109 If you're using a serial line, you may want to give @value{GDBN} the
15110 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15111 (@pxref{Remote Configuration, set remotebaud}) before the
15112 @code{target} command.
15114 @item target remote @code{@var{host}:@var{port}}
15115 @itemx target remote @code{tcp:@var{host}:@var{port}}
15116 @cindex @acronym{TCP} port, @code{target remote}
15117 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15118 The @var{host} may be either a host name or a numeric @acronym{IP}
15119 address; @var{port} must be a decimal number. The @var{host} could be
15120 the target machine itself, if it is directly connected to the net, or
15121 it might be a terminal server which in turn has a serial line to the
15124 For example, to connect to port 2828 on a terminal server named
15128 target remote manyfarms:2828
15131 If your remote target is actually running on the same machine as your
15132 debugger session (e.g.@: a simulator for your target running on the
15133 same host), you can omit the hostname. For example, to connect to
15134 port 1234 on your local machine:
15137 target remote :1234
15141 Note that the colon is still required here.
15143 @item target remote @code{udp:@var{host}:@var{port}}
15144 @cindex @acronym{UDP} port, @code{target remote}
15145 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15146 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15149 target remote udp:manyfarms:2828
15152 When using a @acronym{UDP} connection for remote debugging, you should
15153 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15154 can silently drop packets on busy or unreliable networks, which will
15155 cause havoc with your debugging session.
15157 @item target remote | @var{command}
15158 @cindex pipe, @code{target remote} to
15159 Run @var{command} in the background and communicate with it using a
15160 pipe. The @var{command} is a shell command, to be parsed and expanded
15161 by the system's command shell, @code{/bin/sh}; it should expect remote
15162 protocol packets on its standard input, and send replies on its
15163 standard output. You could use this to run a stand-alone simulator
15164 that speaks the remote debugging protocol, to make net connections
15165 using programs like @code{ssh}, or for other similar tricks.
15167 If @var{command} closes its standard output (perhaps by exiting),
15168 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15169 program has already exited, this will have no effect.)
15173 Once the connection has been established, you can use all the usual
15174 commands to examine and change data. The remote program is already
15175 running; you can use @kbd{step} and @kbd{continue}, and you do not
15176 need to use @kbd{run}.
15178 @cindex interrupting remote programs
15179 @cindex remote programs, interrupting
15180 Whenever @value{GDBN} is waiting for the remote program, if you type the
15181 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
15182 program. This may or may not succeed, depending in part on the hardware
15183 and the serial drivers the remote system uses. If you type the
15184 interrupt character once again, @value{GDBN} displays this prompt:
15187 Interrupted while waiting for the program.
15188 Give up (and stop debugging it)? (y or n)
15191 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
15192 (If you decide you want to try again later, you can use @samp{target
15193 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
15194 goes back to waiting.
15197 @kindex detach (remote)
15199 When you have finished debugging the remote program, you can use the
15200 @code{detach} command to release it from @value{GDBN} control.
15201 Detaching from the target normally resumes its execution, but the results
15202 will depend on your particular remote stub. After the @code{detach}
15203 command, @value{GDBN} is free to connect to another target.
15207 The @code{disconnect} command behaves like @code{detach}, except that
15208 the target is generally not resumed. It will wait for @value{GDBN}
15209 (this instance or another one) to connect and continue debugging. After
15210 the @code{disconnect} command, @value{GDBN} is again free to connect to
15213 @cindex send command to remote monitor
15214 @cindex extend @value{GDBN} for remote targets
15215 @cindex add new commands for external monitor
15217 @item monitor @var{cmd}
15218 This command allows you to send arbitrary commands directly to the
15219 remote monitor. Since @value{GDBN} doesn't care about the commands it
15220 sends like this, this command is the way to extend @value{GDBN}---you
15221 can add new commands that only the external monitor will understand
15225 @node File Transfer
15226 @section Sending files to a remote system
15227 @cindex remote target, file transfer
15228 @cindex file transfer
15229 @cindex sending files to remote systems
15231 Some remote targets offer the ability to transfer files over the same
15232 connection used to communicate with @value{GDBN}. This is convenient
15233 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
15234 running @code{gdbserver} over a network interface. For other targets,
15235 e.g.@: embedded devices with only a single serial port, this may be
15236 the only way to upload or download files.
15238 Not all remote targets support these commands.
15242 @item remote put @var{hostfile} @var{targetfile}
15243 Copy file @var{hostfile} from the host system (the machine running
15244 @value{GDBN}) to @var{targetfile} on the target system.
15247 @item remote get @var{targetfile} @var{hostfile}
15248 Copy file @var{targetfile} from the target system to @var{hostfile}
15249 on the host system.
15251 @kindex remote delete
15252 @item remote delete @var{targetfile}
15253 Delete @var{targetfile} from the target system.
15258 @section Using the @code{gdbserver} Program
15261 @cindex remote connection without stubs
15262 @code{gdbserver} is a control program for Unix-like systems, which
15263 allows you to connect your program with a remote @value{GDBN} via
15264 @code{target remote}---but without linking in the usual debugging stub.
15266 @code{gdbserver} is not a complete replacement for the debugging stubs,
15267 because it requires essentially the same operating-system facilities
15268 that @value{GDBN} itself does. In fact, a system that can run
15269 @code{gdbserver} to connect to a remote @value{GDBN} could also run
15270 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
15271 because it is a much smaller program than @value{GDBN} itself. It is
15272 also easier to port than all of @value{GDBN}, so you may be able to get
15273 started more quickly on a new system by using @code{gdbserver}.
15274 Finally, if you develop code for real-time systems, you may find that
15275 the tradeoffs involved in real-time operation make it more convenient to
15276 do as much development work as possible on another system, for example
15277 by cross-compiling. You can use @code{gdbserver} to make a similar
15278 choice for debugging.
15280 @value{GDBN} and @code{gdbserver} communicate via either a serial line
15281 or a TCP connection, using the standard @value{GDBN} remote serial
15285 @emph{Warning:} @code{gdbserver} does not have any built-in security.
15286 Do not run @code{gdbserver} connected to any public network; a
15287 @value{GDBN} connection to @code{gdbserver} provides access to the
15288 target system with the same privileges as the user running
15292 @subsection Running @code{gdbserver}
15293 @cindex arguments, to @code{gdbserver}
15295 Run @code{gdbserver} on the target system. You need a copy of the
15296 program you want to debug, including any libraries it requires.
15297 @code{gdbserver} does not need your program's symbol table, so you can
15298 strip the program if necessary to save space. @value{GDBN} on the host
15299 system does all the symbol handling.
15301 To use the server, you must tell it how to communicate with @value{GDBN};
15302 the name of your program; and the arguments for your program. The usual
15306 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
15309 @var{comm} is either a device name (to use a serial line) or a TCP
15310 hostname and portnumber. For example, to debug Emacs with the argument
15311 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
15315 target> gdbserver /dev/com1 emacs foo.txt
15318 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
15321 To use a TCP connection instead of a serial line:
15324 target> gdbserver host:2345 emacs foo.txt
15327 The only difference from the previous example is the first argument,
15328 specifying that you are communicating with the host @value{GDBN} via
15329 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
15330 expect a TCP connection from machine @samp{host} to local TCP port 2345.
15331 (Currently, the @samp{host} part is ignored.) You can choose any number
15332 you want for the port number as long as it does not conflict with any
15333 TCP ports already in use on the target system (for example, @code{23} is
15334 reserved for @code{telnet}).@footnote{If you choose a port number that
15335 conflicts with another service, @code{gdbserver} prints an error message
15336 and exits.} You must use the same port number with the host @value{GDBN}
15337 @code{target remote} command.
15339 @subsubsection Attaching to a Running Program
15341 On some targets, @code{gdbserver} can also attach to running programs.
15342 This is accomplished via the @code{--attach} argument. The syntax is:
15345 target> gdbserver --attach @var{comm} @var{pid}
15348 @var{pid} is the process ID of a currently running process. It isn't necessary
15349 to point @code{gdbserver} at a binary for the running process.
15352 @cindex attach to a program by name
15353 You can debug processes by name instead of process ID if your target has the
15354 @code{pidof} utility:
15357 target> gdbserver --attach @var{comm} `pidof @var{program}`
15360 In case more than one copy of @var{program} is running, or @var{program}
15361 has multiple threads, most versions of @code{pidof} support the
15362 @code{-s} option to only return the first process ID.
15364 @subsubsection Multi-Process Mode for @code{gdbserver}
15365 @cindex gdbserver, multiple processes
15366 @cindex multiple processes with gdbserver
15368 When you connect to @code{gdbserver} using @code{target remote},
15369 @code{gdbserver} debugs the specified program only once. When the
15370 program exits, or you detach from it, @value{GDBN} closes the connection
15371 and @code{gdbserver} exits.
15373 If you connect using @kbd{target extended-remote}, @code{gdbserver}
15374 enters multi-process mode. When the debugged program exits, or you
15375 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
15376 though no program is running. The @code{run} and @code{attach}
15377 commands instruct @code{gdbserver} to run or attach to a new program.
15378 The @code{run} command uses @code{set remote exec-file} (@pxref{set
15379 remote exec-file}) to select the program to run. Command line
15380 arguments are supported, except for wildcard expansion and I/O
15381 redirection (@pxref{Arguments}).
15383 To start @code{gdbserver} without supplying an initial command to run
15384 or process ID to attach, use the @option{--multi} command line option.
15385 Then you can connect using @kbd{target extended-remote} and start
15386 the program you want to debug.
15388 @code{gdbserver} does not automatically exit in multi-process mode.
15389 You can terminate it by using @code{monitor exit}
15390 (@pxref{Monitor Commands for gdbserver}).
15392 @subsubsection Other Command-Line Arguments for @code{gdbserver}
15394 The @option{--debug} option tells @code{gdbserver} to display extra
15395 status information about the debugging process. The
15396 @option{--remote-debug} option tells @code{gdbserver} to display
15397 remote protocol debug output. These options are intended for
15398 @code{gdbserver} development and for bug reports to the developers.
15400 The @option{--wrapper} option specifies a wrapper to launch programs
15401 for debugging. The option should be followed by the name of the
15402 wrapper, then any command-line arguments to pass to the wrapper, then
15403 @kbd{--} indicating the end of the wrapper arguments.
15405 @code{gdbserver} runs the specified wrapper program with a combined
15406 command line including the wrapper arguments, then the name of the
15407 program to debug, then any arguments to the program. The wrapper
15408 runs until it executes your program, and then @value{GDBN} gains control.
15410 You can use any program that eventually calls @code{execve} with
15411 its arguments as a wrapper. Several standard Unix utilities do
15412 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
15413 with @code{exec "$@@"} will also work.
15415 For example, you can use @code{env} to pass an environment variable to
15416 the debugged program, without setting the variable in @code{gdbserver}'s
15420 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
15423 @subsection Connecting to @code{gdbserver}
15425 Run @value{GDBN} on the host system.
15427 First make sure you have the necessary symbol files. Load symbols for
15428 your application using the @code{file} command before you connect. Use
15429 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
15430 was compiled with the correct sysroot using @code{--with-sysroot}).
15432 The symbol file and target libraries must exactly match the executable
15433 and libraries on the target, with one exception: the files on the host
15434 system should not be stripped, even if the files on the target system
15435 are. Mismatched or missing files will lead to confusing results
15436 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
15437 files may also prevent @code{gdbserver} from debugging multi-threaded
15440 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
15441 For TCP connections, you must start up @code{gdbserver} prior to using
15442 the @code{target remote} command. Otherwise you may get an error whose
15443 text depends on the host system, but which usually looks something like
15444 @samp{Connection refused}. Don't use the @code{load}
15445 command in @value{GDBN} when using @code{gdbserver}, since the program is
15446 already on the target.
15448 @subsection Monitor Commands for @code{gdbserver}
15449 @cindex monitor commands, for @code{gdbserver}
15450 @anchor{Monitor Commands for gdbserver}
15452 During a @value{GDBN} session using @code{gdbserver}, you can use the
15453 @code{monitor} command to send special requests to @code{gdbserver}.
15454 Here are the available commands.
15458 List the available monitor commands.
15460 @item monitor set debug 0
15461 @itemx monitor set debug 1
15462 Disable or enable general debugging messages.
15464 @item monitor set remote-debug 0
15465 @itemx monitor set remote-debug 1
15466 Disable or enable specific debugging messages associated with the remote
15467 protocol (@pxref{Remote Protocol}).
15469 @item monitor set libthread-db-search-path [PATH]
15470 @cindex gdbserver, search path for @code{libthread_db}
15471 When this command is issued, @var{path} is a colon-separated list of
15472 directories to search for @code{libthread_db} (@pxref{Threads,,set
15473 libthread-db-search-path}). If you omit @var{path},
15474 @samp{libthread-db-search-path} will be reset to an empty list.
15477 Tell gdbserver to exit immediately. This command should be followed by
15478 @code{disconnect} to close the debugging session. @code{gdbserver} will
15479 detach from any attached processes and kill any processes it created.
15480 Use @code{monitor exit} to terminate @code{gdbserver} at the end
15481 of a multi-process mode debug session.
15485 @node Remote Configuration
15486 @section Remote Configuration
15489 @kindex show remote
15490 This section documents the configuration options available when
15491 debugging remote programs. For the options related to the File I/O
15492 extensions of the remote protocol, see @ref{system,
15493 system-call-allowed}.
15496 @item set remoteaddresssize @var{bits}
15497 @cindex address size for remote targets
15498 @cindex bits in remote address
15499 Set the maximum size of address in a memory packet to the specified
15500 number of bits. @value{GDBN} will mask off the address bits above
15501 that number, when it passes addresses to the remote target. The
15502 default value is the number of bits in the target's address.
15504 @item show remoteaddresssize
15505 Show the current value of remote address size in bits.
15507 @item set remotebaud @var{n}
15508 @cindex baud rate for remote targets
15509 Set the baud rate for the remote serial I/O to @var{n} baud. The
15510 value is used to set the speed of the serial port used for debugging
15513 @item show remotebaud
15514 Show the current speed of the remote connection.
15516 @item set remotebreak
15517 @cindex interrupt remote programs
15518 @cindex BREAK signal instead of Ctrl-C
15519 @anchor{set remotebreak}
15520 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
15521 when you type @kbd{Ctrl-c} to interrupt the program running
15522 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
15523 character instead. The default is off, since most remote systems
15524 expect to see @samp{Ctrl-C} as the interrupt signal.
15526 @item show remotebreak
15527 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
15528 interrupt the remote program.
15530 @item set remoteflow on
15531 @itemx set remoteflow off
15532 @kindex set remoteflow
15533 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
15534 on the serial port used to communicate to the remote target.
15536 @item show remoteflow
15537 @kindex show remoteflow
15538 Show the current setting of hardware flow control.
15540 @item set remotelogbase @var{base}
15541 Set the base (a.k.a.@: radix) of logging serial protocol
15542 communications to @var{base}. Supported values of @var{base} are:
15543 @code{ascii}, @code{octal}, and @code{hex}. The default is
15546 @item show remotelogbase
15547 Show the current setting of the radix for logging remote serial
15550 @item set remotelogfile @var{file}
15551 @cindex record serial communications on file
15552 Record remote serial communications on the named @var{file}. The
15553 default is not to record at all.
15555 @item show remotelogfile.
15556 Show the current setting of the file name on which to record the
15557 serial communications.
15559 @item set remotetimeout @var{num}
15560 @cindex timeout for serial communications
15561 @cindex remote timeout
15562 Set the timeout limit to wait for the remote target to respond to
15563 @var{num} seconds. The default is 2 seconds.
15565 @item show remotetimeout
15566 Show the current number of seconds to wait for the remote target
15569 @cindex limit hardware breakpoints and watchpoints
15570 @cindex remote target, limit break- and watchpoints
15571 @anchor{set remote hardware-watchpoint-limit}
15572 @anchor{set remote hardware-breakpoint-limit}
15573 @item set remote hardware-watchpoint-limit @var{limit}
15574 @itemx set remote hardware-breakpoint-limit @var{limit}
15575 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
15576 watchpoints. A limit of -1, the default, is treated as unlimited.
15578 @item set remote exec-file @var{filename}
15579 @itemx show remote exec-file
15580 @anchor{set remote exec-file}
15581 @cindex executable file, for remote target
15582 Select the file used for @code{run} with @code{target
15583 extended-remote}. This should be set to a filename valid on the
15584 target system. If it is not set, the target will use a default
15585 filename (e.g.@: the last program run).
15587 @item set remote interrupt-sequence
15588 @cindex interrupt remote programs
15589 @cindex select Ctrl-C, BREAK or BREAK-g
15590 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
15591 @samp{BREAK-g} as the
15592 sequence to the remote target in order to interrupt the execution.
15593 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
15594 is high level of serial line for some certain time.
15595 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
15596 It is @code{BREAK} signal followed by character @code{g}.
15598 @item show interrupt-sequence
15599 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
15600 is sent by @value{GDBN} to interrupt the remote program.
15601 @code{BREAK-g} is BREAK signal followed by @code{g} and
15602 also known as Magic SysRq g.
15604 @item set remote interrupt-on-connect
15605 @cindex send interrupt-sequence on start
15606 Specify whether interrupt-sequence is sent to remote target when
15607 @value{GDBN} connects to it. This is mostly needed when you debug
15608 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
15609 which is known as Magic SysRq g in order to connect @value{GDBN}.
15611 @item show interrupt-on-connect
15612 Show whether interrupt-sequence is sent
15613 to remote target when @value{GDBN} connects to it.
15617 @item set tcp auto-retry on
15618 @cindex auto-retry, for remote TCP target
15619 Enable auto-retry for remote TCP connections. This is useful if the remote
15620 debugging agent is launched in parallel with @value{GDBN}; there is a race
15621 condition because the agent may not become ready to accept the connection
15622 before @value{GDBN} attempts to connect. When auto-retry is
15623 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
15624 to establish the connection using the timeout specified by
15625 @code{set tcp connect-timeout}.
15627 @item set tcp auto-retry off
15628 Do not auto-retry failed TCP connections.
15630 @item show tcp auto-retry
15631 Show the current auto-retry setting.
15633 @item set tcp connect-timeout @var{seconds}
15634 @cindex connection timeout, for remote TCP target
15635 @cindex timeout, for remote target connection
15636 Set the timeout for establishing a TCP connection to the remote target to
15637 @var{seconds}. The timeout affects both polling to retry failed connections
15638 (enabled by @code{set tcp auto-retry on}) and waiting for connections
15639 that are merely slow to complete, and represents an approximate cumulative
15642 @item show tcp connect-timeout
15643 Show the current connection timeout setting.
15646 @cindex remote packets, enabling and disabling
15647 The @value{GDBN} remote protocol autodetects the packets supported by
15648 your debugging stub. If you need to override the autodetection, you
15649 can use these commands to enable or disable individual packets. Each
15650 packet can be set to @samp{on} (the remote target supports this
15651 packet), @samp{off} (the remote target does not support this packet),
15652 or @samp{auto} (detect remote target support for this packet). They
15653 all default to @samp{auto}. For more information about each packet,
15654 see @ref{Remote Protocol}.
15656 During normal use, you should not have to use any of these commands.
15657 If you do, that may be a bug in your remote debugging stub, or a bug
15658 in @value{GDBN}. You may want to report the problem to the
15659 @value{GDBN} developers.
15661 For each packet @var{name}, the command to enable or disable the
15662 packet is @code{set remote @var{name}-packet}. The available settings
15665 @multitable @columnfractions 0.28 0.32 0.25
15668 @tab Related Features
15670 @item @code{fetch-register}
15672 @tab @code{info registers}
15674 @item @code{set-register}
15678 @item @code{binary-download}
15680 @tab @code{load}, @code{set}
15682 @item @code{read-aux-vector}
15683 @tab @code{qXfer:auxv:read}
15684 @tab @code{info auxv}
15686 @item @code{symbol-lookup}
15687 @tab @code{qSymbol}
15688 @tab Detecting multiple threads
15690 @item @code{attach}
15691 @tab @code{vAttach}
15694 @item @code{verbose-resume}
15696 @tab Stepping or resuming multiple threads
15702 @item @code{software-breakpoint}
15706 @item @code{hardware-breakpoint}
15710 @item @code{write-watchpoint}
15714 @item @code{read-watchpoint}
15718 @item @code{access-watchpoint}
15722 @item @code{target-features}
15723 @tab @code{qXfer:features:read}
15724 @tab @code{set architecture}
15726 @item @code{library-info}
15727 @tab @code{qXfer:libraries:read}
15728 @tab @code{info sharedlibrary}
15730 @item @code{memory-map}
15731 @tab @code{qXfer:memory-map:read}
15732 @tab @code{info mem}
15734 @item @code{read-spu-object}
15735 @tab @code{qXfer:spu:read}
15736 @tab @code{info spu}
15738 @item @code{write-spu-object}
15739 @tab @code{qXfer:spu:write}
15740 @tab @code{info spu}
15742 @item @code{read-siginfo-object}
15743 @tab @code{qXfer:siginfo:read}
15744 @tab @code{print $_siginfo}
15746 @item @code{write-siginfo-object}
15747 @tab @code{qXfer:siginfo:write}
15748 @tab @code{set $_siginfo}
15750 @item @code{threads}
15751 @tab @code{qXfer:threads:read}
15752 @tab @code{info threads}
15754 @item @code{get-thread-local-@*storage-address}
15755 @tab @code{qGetTLSAddr}
15756 @tab Displaying @code{__thread} variables
15758 @item @code{search-memory}
15759 @tab @code{qSearch:memory}
15762 @item @code{supported-packets}
15763 @tab @code{qSupported}
15764 @tab Remote communications parameters
15766 @item @code{pass-signals}
15767 @tab @code{QPassSignals}
15768 @tab @code{handle @var{signal}}
15770 @item @code{hostio-close-packet}
15771 @tab @code{vFile:close}
15772 @tab @code{remote get}, @code{remote put}
15774 @item @code{hostio-open-packet}
15775 @tab @code{vFile:open}
15776 @tab @code{remote get}, @code{remote put}
15778 @item @code{hostio-pread-packet}
15779 @tab @code{vFile:pread}
15780 @tab @code{remote get}, @code{remote put}
15782 @item @code{hostio-pwrite-packet}
15783 @tab @code{vFile:pwrite}
15784 @tab @code{remote get}, @code{remote put}
15786 @item @code{hostio-unlink-packet}
15787 @tab @code{vFile:unlink}
15788 @tab @code{remote delete}
15790 @item @code{noack-packet}
15791 @tab @code{QStartNoAckMode}
15792 @tab Packet acknowledgment
15794 @item @code{osdata}
15795 @tab @code{qXfer:osdata:read}
15796 @tab @code{info os}
15798 @item @code{query-attached}
15799 @tab @code{qAttached}
15800 @tab Querying remote process attach state.
15804 @section Implementing a Remote Stub
15806 @cindex debugging stub, example
15807 @cindex remote stub, example
15808 @cindex stub example, remote debugging
15809 The stub files provided with @value{GDBN} implement the target side of the
15810 communication protocol, and the @value{GDBN} side is implemented in the
15811 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
15812 these subroutines to communicate, and ignore the details. (If you're
15813 implementing your own stub file, you can still ignore the details: start
15814 with one of the existing stub files. @file{sparc-stub.c} is the best
15815 organized, and therefore the easiest to read.)
15817 @cindex remote serial debugging, overview
15818 To debug a program running on another machine (the debugging
15819 @dfn{target} machine), you must first arrange for all the usual
15820 prerequisites for the program to run by itself. For example, for a C
15825 A startup routine to set up the C runtime environment; these usually
15826 have a name like @file{crt0}. The startup routine may be supplied by
15827 your hardware supplier, or you may have to write your own.
15830 A C subroutine library to support your program's
15831 subroutine calls, notably managing input and output.
15834 A way of getting your program to the other machine---for example, a
15835 download program. These are often supplied by the hardware
15836 manufacturer, but you may have to write your own from hardware
15840 The next step is to arrange for your program to use a serial port to
15841 communicate with the machine where @value{GDBN} is running (the @dfn{host}
15842 machine). In general terms, the scheme looks like this:
15846 @value{GDBN} already understands how to use this protocol; when everything
15847 else is set up, you can simply use the @samp{target remote} command
15848 (@pxref{Targets,,Specifying a Debugging Target}).
15850 @item On the target,
15851 you must link with your program a few special-purpose subroutines that
15852 implement the @value{GDBN} remote serial protocol. The file containing these
15853 subroutines is called a @dfn{debugging stub}.
15855 On certain remote targets, you can use an auxiliary program
15856 @code{gdbserver} instead of linking a stub into your program.
15857 @xref{Server,,Using the @code{gdbserver} Program}, for details.
15860 The debugging stub is specific to the architecture of the remote
15861 machine; for example, use @file{sparc-stub.c} to debug programs on
15864 @cindex remote serial stub list
15865 These working remote stubs are distributed with @value{GDBN}:
15870 @cindex @file{i386-stub.c}
15873 For Intel 386 and compatible architectures.
15876 @cindex @file{m68k-stub.c}
15877 @cindex Motorola 680x0
15879 For Motorola 680x0 architectures.
15882 @cindex @file{sh-stub.c}
15885 For Renesas SH architectures.
15888 @cindex @file{sparc-stub.c}
15890 For @sc{sparc} architectures.
15892 @item sparcl-stub.c
15893 @cindex @file{sparcl-stub.c}
15896 For Fujitsu @sc{sparclite} architectures.
15900 The @file{README} file in the @value{GDBN} distribution may list other
15901 recently added stubs.
15904 * Stub Contents:: What the stub can do for you
15905 * Bootstrapping:: What you must do for the stub
15906 * Debug Session:: Putting it all together
15909 @node Stub Contents
15910 @subsection What the Stub Can Do for You
15912 @cindex remote serial stub
15913 The debugging stub for your architecture supplies these three
15917 @item set_debug_traps
15918 @findex set_debug_traps
15919 @cindex remote serial stub, initialization
15920 This routine arranges for @code{handle_exception} to run when your
15921 program stops. You must call this subroutine explicitly near the
15922 beginning of your program.
15924 @item handle_exception
15925 @findex handle_exception
15926 @cindex remote serial stub, main routine
15927 This is the central workhorse, but your program never calls it
15928 explicitly---the setup code arranges for @code{handle_exception} to
15929 run when a trap is triggered.
15931 @code{handle_exception} takes control when your program stops during
15932 execution (for example, on a breakpoint), and mediates communications
15933 with @value{GDBN} on the host machine. This is where the communications
15934 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
15935 representative on the target machine. It begins by sending summary
15936 information on the state of your program, then continues to execute,
15937 retrieving and transmitting any information @value{GDBN} needs, until you
15938 execute a @value{GDBN} command that makes your program resume; at that point,
15939 @code{handle_exception} returns control to your own code on the target
15943 @cindex @code{breakpoint} subroutine, remote
15944 Use this auxiliary subroutine to make your program contain a
15945 breakpoint. Depending on the particular situation, this may be the only
15946 way for @value{GDBN} to get control. For instance, if your target
15947 machine has some sort of interrupt button, you won't need to call this;
15948 pressing the interrupt button transfers control to
15949 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
15950 simply receiving characters on the serial port may also trigger a trap;
15951 again, in that situation, you don't need to call @code{breakpoint} from
15952 your own program---simply running @samp{target remote} from the host
15953 @value{GDBN} session gets control.
15955 Call @code{breakpoint} if none of these is true, or if you simply want
15956 to make certain your program stops at a predetermined point for the
15957 start of your debugging session.
15960 @node Bootstrapping
15961 @subsection What You Must Do for the Stub
15963 @cindex remote stub, support routines
15964 The debugging stubs that come with @value{GDBN} are set up for a particular
15965 chip architecture, but they have no information about the rest of your
15966 debugging target machine.
15968 First of all you need to tell the stub how to communicate with the
15972 @item int getDebugChar()
15973 @findex getDebugChar
15974 Write this subroutine to read a single character from the serial port.
15975 It may be identical to @code{getchar} for your target system; a
15976 different name is used to allow you to distinguish the two if you wish.
15978 @item void putDebugChar(int)
15979 @findex putDebugChar
15980 Write this subroutine to write a single character to the serial port.
15981 It may be identical to @code{putchar} for your target system; a
15982 different name is used to allow you to distinguish the two if you wish.
15985 @cindex control C, and remote debugging
15986 @cindex interrupting remote targets
15987 If you want @value{GDBN} to be able to stop your program while it is
15988 running, you need to use an interrupt-driven serial driver, and arrange
15989 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
15990 character). That is the character which @value{GDBN} uses to tell the
15991 remote system to stop.
15993 Getting the debugging target to return the proper status to @value{GDBN}
15994 probably requires changes to the standard stub; one quick and dirty way
15995 is to just execute a breakpoint instruction (the ``dirty'' part is that
15996 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
15998 Other routines you need to supply are:
16001 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16002 @findex exceptionHandler
16003 Write this function to install @var{exception_address} in the exception
16004 handling tables. You need to do this because the stub does not have any
16005 way of knowing what the exception handling tables on your target system
16006 are like (for example, the processor's table might be in @sc{rom},
16007 containing entries which point to a table in @sc{ram}).
16008 @var{exception_number} is the exception number which should be changed;
16009 its meaning is architecture-dependent (for example, different numbers
16010 might represent divide by zero, misaligned access, etc). When this
16011 exception occurs, control should be transferred directly to
16012 @var{exception_address}, and the processor state (stack, registers,
16013 and so on) should be just as it is when a processor exception occurs. So if
16014 you want to use a jump instruction to reach @var{exception_address}, it
16015 should be a simple jump, not a jump to subroutine.
16017 For the 386, @var{exception_address} should be installed as an interrupt
16018 gate so that interrupts are masked while the handler runs. The gate
16019 should be at privilege level 0 (the most privileged level). The
16020 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16021 help from @code{exceptionHandler}.
16023 @item void flush_i_cache()
16024 @findex flush_i_cache
16025 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16026 instruction cache, if any, on your target machine. If there is no
16027 instruction cache, this subroutine may be a no-op.
16029 On target machines that have instruction caches, @value{GDBN} requires this
16030 function to make certain that the state of your program is stable.
16034 You must also make sure this library routine is available:
16037 @item void *memset(void *, int, int)
16039 This is the standard library function @code{memset} that sets an area of
16040 memory to a known value. If you have one of the free versions of
16041 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16042 either obtain it from your hardware manufacturer, or write your own.
16045 If you do not use the GNU C compiler, you may need other standard
16046 library subroutines as well; this varies from one stub to another,
16047 but in general the stubs are likely to use any of the common library
16048 subroutines which @code{@value{NGCC}} generates as inline code.
16051 @node Debug Session
16052 @subsection Putting it All Together
16054 @cindex remote serial debugging summary
16055 In summary, when your program is ready to debug, you must follow these
16060 Make sure you have defined the supporting low-level routines
16061 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16063 @code{getDebugChar}, @code{putDebugChar},
16064 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16068 Insert these lines near the top of your program:
16076 For the 680x0 stub only, you need to provide a variable called
16077 @code{exceptionHook}. Normally you just use:
16080 void (*exceptionHook)() = 0;
16084 but if before calling @code{set_debug_traps}, you set it to point to a
16085 function in your program, that function is called when
16086 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
16087 error). The function indicated by @code{exceptionHook} is called with
16088 one parameter: an @code{int} which is the exception number.
16091 Compile and link together: your program, the @value{GDBN} debugging stub for
16092 your target architecture, and the supporting subroutines.
16095 Make sure you have a serial connection between your target machine and
16096 the @value{GDBN} host, and identify the serial port on the host.
16099 @c The "remote" target now provides a `load' command, so we should
16100 @c document that. FIXME.
16101 Download your program to your target machine (or get it there by
16102 whatever means the manufacturer provides), and start it.
16105 Start @value{GDBN} on the host, and connect to the target
16106 (@pxref{Connecting,,Connecting to a Remote Target}).
16110 @node Configurations
16111 @chapter Configuration-Specific Information
16113 While nearly all @value{GDBN} commands are available for all native and
16114 cross versions of the debugger, there are some exceptions. This chapter
16115 describes things that are only available in certain configurations.
16117 There are three major categories of configurations: native
16118 configurations, where the host and target are the same, embedded
16119 operating system configurations, which are usually the same for several
16120 different processor architectures, and bare embedded processors, which
16121 are quite different from each other.
16126 * Embedded Processors::
16133 This section describes details specific to particular native
16138 * BSD libkvm Interface:: Debugging BSD kernel memory images
16139 * SVR4 Process Information:: SVR4 process information
16140 * DJGPP Native:: Features specific to the DJGPP port
16141 * Cygwin Native:: Features specific to the Cygwin port
16142 * Hurd Native:: Features specific to @sc{gnu} Hurd
16143 * Neutrino:: Features specific to QNX Neutrino
16144 * Darwin:: Features specific to Darwin
16150 On HP-UX systems, if you refer to a function or variable name that
16151 begins with a dollar sign, @value{GDBN} searches for a user or system
16152 name first, before it searches for a convenience variable.
16155 @node BSD libkvm Interface
16156 @subsection BSD libkvm Interface
16159 @cindex kernel memory image
16160 @cindex kernel crash dump
16162 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
16163 interface that provides a uniform interface for accessing kernel virtual
16164 memory images, including live systems and crash dumps. @value{GDBN}
16165 uses this interface to allow you to debug live kernels and kernel crash
16166 dumps on many native BSD configurations. This is implemented as a
16167 special @code{kvm} debugging target. For debugging a live system, load
16168 the currently running kernel into @value{GDBN} and connect to the
16172 (@value{GDBP}) @b{target kvm}
16175 For debugging crash dumps, provide the file name of the crash dump as an
16179 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
16182 Once connected to the @code{kvm} target, the following commands are
16188 Set current context from the @dfn{Process Control Block} (PCB) address.
16191 Set current context from proc address. This command isn't available on
16192 modern FreeBSD systems.
16195 @node SVR4 Process Information
16196 @subsection SVR4 Process Information
16198 @cindex examine process image
16199 @cindex process info via @file{/proc}
16201 Many versions of SVR4 and compatible systems provide a facility called
16202 @samp{/proc} that can be used to examine the image of a running
16203 process using file-system subroutines. If @value{GDBN} is configured
16204 for an operating system with this facility, the command @code{info
16205 proc} is available to report information about the process running
16206 your program, or about any process running on your system. @code{info
16207 proc} works only on SVR4 systems that include the @code{procfs} code.
16208 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
16209 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
16215 @itemx info proc @var{process-id}
16216 Summarize available information about any running process. If a
16217 process ID is specified by @var{process-id}, display information about
16218 that process; otherwise display information about the program being
16219 debugged. The summary includes the debugged process ID, the command
16220 line used to invoke it, its current working directory, and its
16221 executable file's absolute file name.
16223 On some systems, @var{process-id} can be of the form
16224 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
16225 within a process. If the optional @var{pid} part is missing, it means
16226 a thread from the process being debugged (the leading @samp{/} still
16227 needs to be present, or else @value{GDBN} will interpret the number as
16228 a process ID rather than a thread ID).
16230 @item info proc mappings
16231 @cindex memory address space mappings
16232 Report the memory address space ranges accessible in the program, with
16233 information on whether the process has read, write, or execute access
16234 rights to each range. On @sc{gnu}/Linux systems, each memory range
16235 includes the object file which is mapped to that range, instead of the
16236 memory access rights to that range.
16238 @item info proc stat
16239 @itemx info proc status
16240 @cindex process detailed status information
16241 These subcommands are specific to @sc{gnu}/Linux systems. They show
16242 the process-related information, including the user ID and group ID;
16243 how many threads are there in the process; its virtual memory usage;
16244 the signals that are pending, blocked, and ignored; its TTY; its
16245 consumption of system and user time; its stack size; its @samp{nice}
16246 value; etc. For more information, see the @samp{proc} man page
16247 (type @kbd{man 5 proc} from your shell prompt).
16249 @item info proc all
16250 Show all the information about the process described under all of the
16251 above @code{info proc} subcommands.
16254 @comment These sub-options of 'info proc' were not included when
16255 @comment procfs.c was re-written. Keep their descriptions around
16256 @comment against the day when someone finds the time to put them back in.
16257 @kindex info proc times
16258 @item info proc times
16259 Starting time, user CPU time, and system CPU time for your program and
16262 @kindex info proc id
16264 Report on the process IDs related to your program: its own process ID,
16265 the ID of its parent, the process group ID, and the session ID.
16268 @item set procfs-trace
16269 @kindex set procfs-trace
16270 @cindex @code{procfs} API calls
16271 This command enables and disables tracing of @code{procfs} API calls.
16273 @item show procfs-trace
16274 @kindex show procfs-trace
16275 Show the current state of @code{procfs} API call tracing.
16277 @item set procfs-file @var{file}
16278 @kindex set procfs-file
16279 Tell @value{GDBN} to write @code{procfs} API trace to the named
16280 @var{file}. @value{GDBN} appends the trace info to the previous
16281 contents of the file. The default is to display the trace on the
16284 @item show procfs-file
16285 @kindex show procfs-file
16286 Show the file to which @code{procfs} API trace is written.
16288 @item proc-trace-entry
16289 @itemx proc-trace-exit
16290 @itemx proc-untrace-entry
16291 @itemx proc-untrace-exit
16292 @kindex proc-trace-entry
16293 @kindex proc-trace-exit
16294 @kindex proc-untrace-entry
16295 @kindex proc-untrace-exit
16296 These commands enable and disable tracing of entries into and exits
16297 from the @code{syscall} interface.
16300 @kindex info pidlist
16301 @cindex process list, QNX Neutrino
16302 For QNX Neutrino only, this command displays the list of all the
16303 processes and all the threads within each process.
16306 @kindex info meminfo
16307 @cindex mapinfo list, QNX Neutrino
16308 For QNX Neutrino only, this command displays the list of all mapinfos.
16312 @subsection Features for Debugging @sc{djgpp} Programs
16313 @cindex @sc{djgpp} debugging
16314 @cindex native @sc{djgpp} debugging
16315 @cindex MS-DOS-specific commands
16318 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
16319 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
16320 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
16321 top of real-mode DOS systems and their emulations.
16323 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
16324 defines a few commands specific to the @sc{djgpp} port. This
16325 subsection describes those commands.
16330 This is a prefix of @sc{djgpp}-specific commands which print
16331 information about the target system and important OS structures.
16334 @cindex MS-DOS system info
16335 @cindex free memory information (MS-DOS)
16336 @item info dos sysinfo
16337 This command displays assorted information about the underlying
16338 platform: the CPU type and features, the OS version and flavor, the
16339 DPMI version, and the available conventional and DPMI memory.
16344 @cindex segment descriptor tables
16345 @cindex descriptor tables display
16347 @itemx info dos ldt
16348 @itemx info dos idt
16349 These 3 commands display entries from, respectively, Global, Local,
16350 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
16351 tables are data structures which store a descriptor for each segment
16352 that is currently in use. The segment's selector is an index into a
16353 descriptor table; the table entry for that index holds the
16354 descriptor's base address and limit, and its attributes and access
16357 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
16358 segment (used for both data and the stack), and a DOS segment (which
16359 allows access to DOS/BIOS data structures and absolute addresses in
16360 conventional memory). However, the DPMI host will usually define
16361 additional segments in order to support the DPMI environment.
16363 @cindex garbled pointers
16364 These commands allow to display entries from the descriptor tables.
16365 Without an argument, all entries from the specified table are
16366 displayed. An argument, which should be an integer expression, means
16367 display a single entry whose index is given by the argument. For
16368 example, here's a convenient way to display information about the
16369 debugged program's data segment:
16372 @exdent @code{(@value{GDBP}) info dos ldt $ds}
16373 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
16377 This comes in handy when you want to see whether a pointer is outside
16378 the data segment's limit (i.e.@: @dfn{garbled}).
16380 @cindex page tables display (MS-DOS)
16382 @itemx info dos pte
16383 These two commands display entries from, respectively, the Page
16384 Directory and the Page Tables. Page Directories and Page Tables are
16385 data structures which control how virtual memory addresses are mapped
16386 into physical addresses. A Page Table includes an entry for every
16387 page of memory that is mapped into the program's address space; there
16388 may be several Page Tables, each one holding up to 4096 entries. A
16389 Page Directory has up to 4096 entries, one each for every Page Table
16390 that is currently in use.
16392 Without an argument, @kbd{info dos pde} displays the entire Page
16393 Directory, and @kbd{info dos pte} displays all the entries in all of
16394 the Page Tables. An argument, an integer expression, given to the
16395 @kbd{info dos pde} command means display only that entry from the Page
16396 Directory table. An argument given to the @kbd{info dos pte} command
16397 means display entries from a single Page Table, the one pointed to by
16398 the specified entry in the Page Directory.
16400 @cindex direct memory access (DMA) on MS-DOS
16401 These commands are useful when your program uses @dfn{DMA} (Direct
16402 Memory Access), which needs physical addresses to program the DMA
16405 These commands are supported only with some DPMI servers.
16407 @cindex physical address from linear address
16408 @item info dos address-pte @var{addr}
16409 This command displays the Page Table entry for a specified linear
16410 address. The argument @var{addr} is a linear address which should
16411 already have the appropriate segment's base address added to it,
16412 because this command accepts addresses which may belong to @emph{any}
16413 segment. For example, here's how to display the Page Table entry for
16414 the page where a variable @code{i} is stored:
16417 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
16418 @exdent @code{Page Table entry for address 0x11a00d30:}
16419 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
16423 This says that @code{i} is stored at offset @code{0xd30} from the page
16424 whose physical base address is @code{0x02698000}, and shows all the
16425 attributes of that page.
16427 Note that you must cast the addresses of variables to a @code{char *},
16428 since otherwise the value of @code{__djgpp_base_address}, the base
16429 address of all variables and functions in a @sc{djgpp} program, will
16430 be added using the rules of C pointer arithmetics: if @code{i} is
16431 declared an @code{int}, @value{GDBN} will add 4 times the value of
16432 @code{__djgpp_base_address} to the address of @code{i}.
16434 Here's another example, it displays the Page Table entry for the
16438 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
16439 @exdent @code{Page Table entry for address 0x29110:}
16440 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
16444 (The @code{+ 3} offset is because the transfer buffer's address is the
16445 3rd member of the @code{_go32_info_block} structure.) The output
16446 clearly shows that this DPMI server maps the addresses in conventional
16447 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
16448 linear (@code{0x29110}) addresses are identical.
16450 This command is supported only with some DPMI servers.
16453 @cindex DOS serial data link, remote debugging
16454 In addition to native debugging, the DJGPP port supports remote
16455 debugging via a serial data link. The following commands are specific
16456 to remote serial debugging in the DJGPP port of @value{GDBN}.
16459 @kindex set com1base
16460 @kindex set com1irq
16461 @kindex set com2base
16462 @kindex set com2irq
16463 @kindex set com3base
16464 @kindex set com3irq
16465 @kindex set com4base
16466 @kindex set com4irq
16467 @item set com1base @var{addr}
16468 This command sets the base I/O port address of the @file{COM1} serial
16471 @item set com1irq @var{irq}
16472 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
16473 for the @file{COM1} serial port.
16475 There are similar commands @samp{set com2base}, @samp{set com3irq},
16476 etc.@: for setting the port address and the @code{IRQ} lines for the
16479 @kindex show com1base
16480 @kindex show com1irq
16481 @kindex show com2base
16482 @kindex show com2irq
16483 @kindex show com3base
16484 @kindex show com3irq
16485 @kindex show com4base
16486 @kindex show com4irq
16487 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
16488 display the current settings of the base address and the @code{IRQ}
16489 lines used by the COM ports.
16492 @kindex info serial
16493 @cindex DOS serial port status
16494 This command prints the status of the 4 DOS serial ports. For each
16495 port, it prints whether it's active or not, its I/O base address and
16496 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
16497 counts of various errors encountered so far.
16501 @node Cygwin Native
16502 @subsection Features for Debugging MS Windows PE Executables
16503 @cindex MS Windows debugging
16504 @cindex native Cygwin debugging
16505 @cindex Cygwin-specific commands
16507 @value{GDBN} supports native debugging of MS Windows programs, including
16508 DLLs with and without symbolic debugging information.
16510 @cindex Ctrl-BREAK, MS-Windows
16511 @cindex interrupt debuggee on MS-Windows
16512 MS-Windows programs that call @code{SetConsoleMode} to switch off the
16513 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
16514 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
16515 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
16516 sequence, which can be used to interrupt the debuggee even if it
16519 There are various additional Cygwin-specific commands, described in
16520 this section. Working with DLLs that have no debugging symbols is
16521 described in @ref{Non-debug DLL Symbols}.
16526 This is a prefix of MS Windows-specific commands which print
16527 information about the target system and important OS structures.
16529 @item info w32 selector
16530 This command displays information returned by
16531 the Win32 API @code{GetThreadSelectorEntry} function.
16532 It takes an optional argument that is evaluated to
16533 a long value to give the information about this given selector.
16534 Without argument, this command displays information
16535 about the six segment registers.
16539 This is a Cygwin-specific alias of @code{info shared}.
16541 @kindex dll-symbols
16543 This command loads symbols from a dll similarly to
16544 add-sym command but without the need to specify a base address.
16546 @kindex set cygwin-exceptions
16547 @cindex debugging the Cygwin DLL
16548 @cindex Cygwin DLL, debugging
16549 @item set cygwin-exceptions @var{mode}
16550 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
16551 happen inside the Cygwin DLL. If @var{mode} is @code{off},
16552 @value{GDBN} will delay recognition of exceptions, and may ignore some
16553 exceptions which seem to be caused by internal Cygwin DLL
16554 ``bookkeeping''. This option is meant primarily for debugging the
16555 Cygwin DLL itself; the default value is @code{off} to avoid annoying
16556 @value{GDBN} users with false @code{SIGSEGV} signals.
16558 @kindex show cygwin-exceptions
16559 @item show cygwin-exceptions
16560 Displays whether @value{GDBN} will break on exceptions that happen
16561 inside the Cygwin DLL itself.
16563 @kindex set new-console
16564 @item set new-console @var{mode}
16565 If @var{mode} is @code{on} the debuggee will
16566 be started in a new console on next start.
16567 If @var{mode} is @code{off}, the debuggee will
16568 be started in the same console as the debugger.
16570 @kindex show new-console
16571 @item show new-console
16572 Displays whether a new console is used
16573 when the debuggee is started.
16575 @kindex set new-group
16576 @item set new-group @var{mode}
16577 This boolean value controls whether the debuggee should
16578 start a new group or stay in the same group as the debugger.
16579 This affects the way the Windows OS handles
16582 @kindex show new-group
16583 @item show new-group
16584 Displays current value of new-group boolean.
16586 @kindex set debugevents
16587 @item set debugevents
16588 This boolean value adds debug output concerning kernel events related
16589 to the debuggee seen by the debugger. This includes events that
16590 signal thread and process creation and exit, DLL loading and
16591 unloading, console interrupts, and debugging messages produced by the
16592 Windows @code{OutputDebugString} API call.
16594 @kindex set debugexec
16595 @item set debugexec
16596 This boolean value adds debug output concerning execute events
16597 (such as resume thread) seen by the debugger.
16599 @kindex set debugexceptions
16600 @item set debugexceptions
16601 This boolean value adds debug output concerning exceptions in the
16602 debuggee seen by the debugger.
16604 @kindex set debugmemory
16605 @item set debugmemory
16606 This boolean value adds debug output concerning debuggee memory reads
16607 and writes by the debugger.
16611 This boolean values specifies whether the debuggee is called
16612 via a shell or directly (default value is on).
16616 Displays if the debuggee will be started with a shell.
16621 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
16624 @node Non-debug DLL Symbols
16625 @subsubsection Support for DLLs without Debugging Symbols
16626 @cindex DLLs with no debugging symbols
16627 @cindex Minimal symbols and DLLs
16629 Very often on windows, some of the DLLs that your program relies on do
16630 not include symbolic debugging information (for example,
16631 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
16632 symbols in a DLL, it relies on the minimal amount of symbolic
16633 information contained in the DLL's export table. This section
16634 describes working with such symbols, known internally to @value{GDBN} as
16635 ``minimal symbols''.
16637 Note that before the debugged program has started execution, no DLLs
16638 will have been loaded. The easiest way around this problem is simply to
16639 start the program --- either by setting a breakpoint or letting the
16640 program run once to completion. It is also possible to force
16641 @value{GDBN} to load a particular DLL before starting the executable ---
16642 see the shared library information in @ref{Files}, or the
16643 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
16644 explicitly loading symbols from a DLL with no debugging information will
16645 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
16646 which may adversely affect symbol lookup performance.
16648 @subsubsection DLL Name Prefixes
16650 In keeping with the naming conventions used by the Microsoft debugging
16651 tools, DLL export symbols are made available with a prefix based on the
16652 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
16653 also entered into the symbol table, so @code{CreateFileA} is often
16654 sufficient. In some cases there will be name clashes within a program
16655 (particularly if the executable itself includes full debugging symbols)
16656 necessitating the use of the fully qualified name when referring to the
16657 contents of the DLL. Use single-quotes around the name to avoid the
16658 exclamation mark (``!'') being interpreted as a language operator.
16660 Note that the internal name of the DLL may be all upper-case, even
16661 though the file name of the DLL is lower-case, or vice-versa. Since
16662 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
16663 some confusion. If in doubt, try the @code{info functions} and
16664 @code{info variables} commands or even @code{maint print msymbols}
16665 (@pxref{Symbols}). Here's an example:
16668 (@value{GDBP}) info function CreateFileA
16669 All functions matching regular expression "CreateFileA":
16671 Non-debugging symbols:
16672 0x77e885f4 CreateFileA
16673 0x77e885f4 KERNEL32!CreateFileA
16677 (@value{GDBP}) info function !
16678 All functions matching regular expression "!":
16680 Non-debugging symbols:
16681 0x6100114c cygwin1!__assert
16682 0x61004034 cygwin1!_dll_crt0@@0
16683 0x61004240 cygwin1!dll_crt0(per_process *)
16687 @subsubsection Working with Minimal Symbols
16689 Symbols extracted from a DLL's export table do not contain very much
16690 type information. All that @value{GDBN} can do is guess whether a symbol
16691 refers to a function or variable depending on the linker section that
16692 contains the symbol. Also note that the actual contents of the memory
16693 contained in a DLL are not available unless the program is running. This
16694 means that you cannot examine the contents of a variable or disassemble
16695 a function within a DLL without a running program.
16697 Variables are generally treated as pointers and dereferenced
16698 automatically. For this reason, it is often necessary to prefix a
16699 variable name with the address-of operator (``&'') and provide explicit
16700 type information in the command. Here's an example of the type of
16704 (@value{GDBP}) print 'cygwin1!__argv'
16709 (@value{GDBP}) x 'cygwin1!__argv'
16710 0x10021610: "\230y\""
16713 And two possible solutions:
16716 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
16717 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
16721 (@value{GDBP}) x/2x &'cygwin1!__argv'
16722 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
16723 (@value{GDBP}) x/x 0x10021608
16724 0x10021608: 0x0022fd98
16725 (@value{GDBP}) x/s 0x0022fd98
16726 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
16729 Setting a break point within a DLL is possible even before the program
16730 starts execution. However, under these circumstances, @value{GDBN} can't
16731 examine the initial instructions of the function in order to skip the
16732 function's frame set-up code. You can work around this by using ``*&''
16733 to set the breakpoint at a raw memory address:
16736 (@value{GDBP}) break *&'python22!PyOS_Readline'
16737 Breakpoint 1 at 0x1e04eff0
16740 The author of these extensions is not entirely convinced that setting a
16741 break point within a shared DLL like @file{kernel32.dll} is completely
16745 @subsection Commands Specific to @sc{gnu} Hurd Systems
16746 @cindex @sc{gnu} Hurd debugging
16748 This subsection describes @value{GDBN} commands specific to the
16749 @sc{gnu} Hurd native debugging.
16754 @kindex set signals@r{, Hurd command}
16755 @kindex set sigs@r{, Hurd command}
16756 This command toggles the state of inferior signal interception by
16757 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
16758 affected by this command. @code{sigs} is a shorthand alias for
16763 @kindex show signals@r{, Hurd command}
16764 @kindex show sigs@r{, Hurd command}
16765 Show the current state of intercepting inferior's signals.
16767 @item set signal-thread
16768 @itemx set sigthread
16769 @kindex set signal-thread
16770 @kindex set sigthread
16771 This command tells @value{GDBN} which thread is the @code{libc} signal
16772 thread. That thread is run when a signal is delivered to a running
16773 process. @code{set sigthread} is the shorthand alias of @code{set
16776 @item show signal-thread
16777 @itemx show sigthread
16778 @kindex show signal-thread
16779 @kindex show sigthread
16780 These two commands show which thread will run when the inferior is
16781 delivered a signal.
16784 @kindex set stopped@r{, Hurd command}
16785 This commands tells @value{GDBN} that the inferior process is stopped,
16786 as with the @code{SIGSTOP} signal. The stopped process can be
16787 continued by delivering a signal to it.
16790 @kindex show stopped@r{, Hurd command}
16791 This command shows whether @value{GDBN} thinks the debuggee is
16794 @item set exceptions
16795 @kindex set exceptions@r{, Hurd command}
16796 Use this command to turn off trapping of exceptions in the inferior.
16797 When exception trapping is off, neither breakpoints nor
16798 single-stepping will work. To restore the default, set exception
16801 @item show exceptions
16802 @kindex show exceptions@r{, Hurd command}
16803 Show the current state of trapping exceptions in the inferior.
16805 @item set task pause
16806 @kindex set task@r{, Hurd commands}
16807 @cindex task attributes (@sc{gnu} Hurd)
16808 @cindex pause current task (@sc{gnu} Hurd)
16809 This command toggles task suspension when @value{GDBN} has control.
16810 Setting it to on takes effect immediately, and the task is suspended
16811 whenever @value{GDBN} gets control. Setting it to off will take
16812 effect the next time the inferior is continued. If this option is set
16813 to off, you can use @code{set thread default pause on} or @code{set
16814 thread pause on} (see below) to pause individual threads.
16816 @item show task pause
16817 @kindex show task@r{, Hurd commands}
16818 Show the current state of task suspension.
16820 @item set task detach-suspend-count
16821 @cindex task suspend count
16822 @cindex detach from task, @sc{gnu} Hurd
16823 This command sets the suspend count the task will be left with when
16824 @value{GDBN} detaches from it.
16826 @item show task detach-suspend-count
16827 Show the suspend count the task will be left with when detaching.
16829 @item set task exception-port
16830 @itemx set task excp
16831 @cindex task exception port, @sc{gnu} Hurd
16832 This command sets the task exception port to which @value{GDBN} will
16833 forward exceptions. The argument should be the value of the @dfn{send
16834 rights} of the task. @code{set task excp} is a shorthand alias.
16836 @item set noninvasive
16837 @cindex noninvasive task options
16838 This command switches @value{GDBN} to a mode that is the least
16839 invasive as far as interfering with the inferior is concerned. This
16840 is the same as using @code{set task pause}, @code{set exceptions}, and
16841 @code{set signals} to values opposite to the defaults.
16843 @item info send-rights
16844 @itemx info receive-rights
16845 @itemx info port-rights
16846 @itemx info port-sets
16847 @itemx info dead-names
16850 @cindex send rights, @sc{gnu} Hurd
16851 @cindex receive rights, @sc{gnu} Hurd
16852 @cindex port rights, @sc{gnu} Hurd
16853 @cindex port sets, @sc{gnu} Hurd
16854 @cindex dead names, @sc{gnu} Hurd
16855 These commands display information about, respectively, send rights,
16856 receive rights, port rights, port sets, and dead names of a task.
16857 There are also shorthand aliases: @code{info ports} for @code{info
16858 port-rights} and @code{info psets} for @code{info port-sets}.
16860 @item set thread pause
16861 @kindex set thread@r{, Hurd command}
16862 @cindex thread properties, @sc{gnu} Hurd
16863 @cindex pause current thread (@sc{gnu} Hurd)
16864 This command toggles current thread suspension when @value{GDBN} has
16865 control. Setting it to on takes effect immediately, and the current
16866 thread is suspended whenever @value{GDBN} gets control. Setting it to
16867 off will take effect the next time the inferior is continued.
16868 Normally, this command has no effect, since when @value{GDBN} has
16869 control, the whole task is suspended. However, if you used @code{set
16870 task pause off} (see above), this command comes in handy to suspend
16871 only the current thread.
16873 @item show thread pause
16874 @kindex show thread@r{, Hurd command}
16875 This command shows the state of current thread suspension.
16877 @item set thread run
16878 This command sets whether the current thread is allowed to run.
16880 @item show thread run
16881 Show whether the current thread is allowed to run.
16883 @item set thread detach-suspend-count
16884 @cindex thread suspend count, @sc{gnu} Hurd
16885 @cindex detach from thread, @sc{gnu} Hurd
16886 This command sets the suspend count @value{GDBN} will leave on a
16887 thread when detaching. This number is relative to the suspend count
16888 found by @value{GDBN} when it notices the thread; use @code{set thread
16889 takeover-suspend-count} to force it to an absolute value.
16891 @item show thread detach-suspend-count
16892 Show the suspend count @value{GDBN} will leave on the thread when
16895 @item set thread exception-port
16896 @itemx set thread excp
16897 Set the thread exception port to which to forward exceptions. This
16898 overrides the port set by @code{set task exception-port} (see above).
16899 @code{set thread excp} is the shorthand alias.
16901 @item set thread takeover-suspend-count
16902 Normally, @value{GDBN}'s thread suspend counts are relative to the
16903 value @value{GDBN} finds when it notices each thread. This command
16904 changes the suspend counts to be absolute instead.
16906 @item set thread default
16907 @itemx show thread default
16908 @cindex thread default settings, @sc{gnu} Hurd
16909 Each of the above @code{set thread} commands has a @code{set thread
16910 default} counterpart (e.g., @code{set thread default pause}, @code{set
16911 thread default exception-port}, etc.). The @code{thread default}
16912 variety of commands sets the default thread properties for all
16913 threads; you can then change the properties of individual threads with
16914 the non-default commands.
16919 @subsection QNX Neutrino
16920 @cindex QNX Neutrino
16922 @value{GDBN} provides the following commands specific to the QNX
16926 @item set debug nto-debug
16927 @kindex set debug nto-debug
16928 When set to on, enables debugging messages specific to the QNX
16931 @item show debug nto-debug
16932 @kindex show debug nto-debug
16933 Show the current state of QNX Neutrino messages.
16940 @value{GDBN} provides the following commands specific to the Darwin target:
16943 @item set debug darwin @var{num}
16944 @kindex set debug darwin
16945 When set to a non zero value, enables debugging messages specific to
16946 the Darwin support. Higher values produce more verbose output.
16948 @item show debug darwin
16949 @kindex show debug darwin
16950 Show the current state of Darwin messages.
16952 @item set debug mach-o @var{num}
16953 @kindex set debug mach-o
16954 When set to a non zero value, enables debugging messages while
16955 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
16956 file format used on Darwin for object and executable files.) Higher
16957 values produce more verbose output. This is a command to diagnose
16958 problems internal to @value{GDBN} and should not be needed in normal
16961 @item show debug mach-o
16962 @kindex show debug mach-o
16963 Show the current state of Mach-O file messages.
16965 @item set mach-exceptions on
16966 @itemx set mach-exceptions off
16967 @kindex set mach-exceptions
16968 On Darwin, faults are first reported as a Mach exception and are then
16969 mapped to a Posix signal. Use this command to turn on trapping of
16970 Mach exceptions in the inferior. This might be sometimes useful to
16971 better understand the cause of a fault. The default is off.
16973 @item show mach-exceptions
16974 @kindex show mach-exceptions
16975 Show the current state of exceptions trapping.
16980 @section Embedded Operating Systems
16982 This section describes configurations involving the debugging of
16983 embedded operating systems that are available for several different
16987 * VxWorks:: Using @value{GDBN} with VxWorks
16990 @value{GDBN} includes the ability to debug programs running on
16991 various real-time operating systems.
16994 @subsection Using @value{GDBN} with VxWorks
17000 @kindex target vxworks
17001 @item target vxworks @var{machinename}
17002 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17003 is the target system's machine name or IP address.
17007 On VxWorks, @code{load} links @var{filename} dynamically on the
17008 current target system as well as adding its symbols in @value{GDBN}.
17010 @value{GDBN} enables developers to spawn and debug tasks running on networked
17011 VxWorks targets from a Unix host. Already-running tasks spawned from
17012 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17013 both the Unix host and on the VxWorks target. The program
17014 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17015 installed with the name @code{vxgdb}, to distinguish it from a
17016 @value{GDBN} for debugging programs on the host itself.)
17019 @item VxWorks-timeout @var{args}
17020 @kindex vxworks-timeout
17021 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17022 This option is set by the user, and @var{args} represents the number of
17023 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17024 your VxWorks target is a slow software simulator or is on the far side
17025 of a thin network line.
17028 The following information on connecting to VxWorks was current when
17029 this manual was produced; newer releases of VxWorks may use revised
17032 @findex INCLUDE_RDB
17033 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17034 to include the remote debugging interface routines in the VxWorks
17035 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17036 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17037 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17038 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17039 information on configuring and remaking VxWorks, see the manufacturer's
17041 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17043 Once you have included @file{rdb.a} in your VxWorks system image and set
17044 your Unix execution search path to find @value{GDBN}, you are ready to
17045 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17046 @code{vxgdb}, depending on your installation).
17048 @value{GDBN} comes up showing the prompt:
17055 * VxWorks Connection:: Connecting to VxWorks
17056 * VxWorks Download:: VxWorks download
17057 * VxWorks Attach:: Running tasks
17060 @node VxWorks Connection
17061 @subsubsection Connecting to VxWorks
17063 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17064 network. To connect to a target whose host name is ``@code{tt}'', type:
17067 (vxgdb) target vxworks tt
17071 @value{GDBN} displays messages like these:
17074 Attaching remote machine across net...
17079 @value{GDBN} then attempts to read the symbol tables of any object modules
17080 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
17081 these files by searching the directories listed in the command search
17082 path (@pxref{Environment, ,Your Program's Environment}); if it fails
17083 to find an object file, it displays a message such as:
17086 prog.o: No such file or directory.
17089 When this happens, add the appropriate directory to the search path with
17090 the @value{GDBN} command @code{path}, and execute the @code{target}
17093 @node VxWorks Download
17094 @subsubsection VxWorks Download
17096 @cindex download to VxWorks
17097 If you have connected to the VxWorks target and you want to debug an
17098 object that has not yet been loaded, you can use the @value{GDBN}
17099 @code{load} command to download a file from Unix to VxWorks
17100 incrementally. The object file given as an argument to the @code{load}
17101 command is actually opened twice: first by the VxWorks target in order
17102 to download the code, then by @value{GDBN} in order to read the symbol
17103 table. This can lead to problems if the current working directories on
17104 the two systems differ. If both systems have NFS mounted the same
17105 filesystems, you can avoid these problems by using absolute paths.
17106 Otherwise, it is simplest to set the working directory on both systems
17107 to the directory in which the object file resides, and then to reference
17108 the file by its name, without any path. For instance, a program
17109 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
17110 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
17111 program, type this on VxWorks:
17114 -> cd "@var{vxpath}/vw/demo/rdb"
17118 Then, in @value{GDBN}, type:
17121 (vxgdb) cd @var{hostpath}/vw/demo/rdb
17122 (vxgdb) load prog.o
17125 @value{GDBN} displays a response similar to this:
17128 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
17131 You can also use the @code{load} command to reload an object module
17132 after editing and recompiling the corresponding source file. Note that
17133 this makes @value{GDBN} delete all currently-defined breakpoints,
17134 auto-displays, and convenience variables, and to clear the value
17135 history. (This is necessary in order to preserve the integrity of
17136 debugger's data structures that reference the target system's symbol
17139 @node VxWorks Attach
17140 @subsubsection Running Tasks
17142 @cindex running VxWorks tasks
17143 You can also attach to an existing task using the @code{attach} command as
17147 (vxgdb) attach @var{task}
17151 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
17152 or suspended when you attach to it. Running tasks are suspended at
17153 the time of attachment.
17155 @node Embedded Processors
17156 @section Embedded Processors
17158 This section goes into details specific to particular embedded
17161 @cindex send command to simulator
17162 Whenever a specific embedded processor has a simulator, @value{GDBN}
17163 allows to send an arbitrary command to the simulator.
17166 @item sim @var{command}
17167 @kindex sim@r{, a command}
17168 Send an arbitrary @var{command} string to the simulator. Consult the
17169 documentation for the specific simulator in use for information about
17170 acceptable commands.
17176 * M32R/D:: Renesas M32R/D
17177 * M68K:: Motorola M68K
17178 * MicroBlaze:: Xilinx MicroBlaze
17179 * MIPS Embedded:: MIPS Embedded
17180 * OpenRISC 1000:: OpenRisc 1000
17181 * PA:: HP PA Embedded
17182 * PowerPC Embedded:: PowerPC Embedded
17183 * Sparclet:: Tsqware Sparclet
17184 * Sparclite:: Fujitsu Sparclite
17185 * Z8000:: Zilog Z8000
17188 * Super-H:: Renesas Super-H
17197 @item target rdi @var{dev}
17198 ARM Angel monitor, via RDI library interface to ADP protocol. You may
17199 use this target to communicate with both boards running the Angel
17200 monitor, or with the EmbeddedICE JTAG debug device.
17203 @item target rdp @var{dev}
17208 @value{GDBN} provides the following ARM-specific commands:
17211 @item set arm disassembler
17213 This commands selects from a list of disassembly styles. The
17214 @code{"std"} style is the standard style.
17216 @item show arm disassembler
17218 Show the current disassembly style.
17220 @item set arm apcs32
17221 @cindex ARM 32-bit mode
17222 This command toggles ARM operation mode between 32-bit and 26-bit.
17224 @item show arm apcs32
17225 Display the current usage of the ARM 32-bit mode.
17227 @item set arm fpu @var{fputype}
17228 This command sets the ARM floating-point unit (FPU) type. The
17229 argument @var{fputype} can be one of these:
17233 Determine the FPU type by querying the OS ABI.
17235 Software FPU, with mixed-endian doubles on little-endian ARM
17238 GCC-compiled FPA co-processor.
17240 Software FPU with pure-endian doubles.
17246 Show the current type of the FPU.
17249 This command forces @value{GDBN} to use the specified ABI.
17252 Show the currently used ABI.
17254 @item set arm fallback-mode (arm|thumb|auto)
17255 @value{GDBN} uses the symbol table, when available, to determine
17256 whether instructions are ARM or Thumb. This command controls
17257 @value{GDBN}'s default behavior when the symbol table is not
17258 available. The default is @samp{auto}, which causes @value{GDBN} to
17259 use the current execution mode (from the @code{T} bit in the @code{CPSR}
17262 @item show arm fallback-mode
17263 Show the current fallback instruction mode.
17265 @item set arm force-mode (arm|thumb|auto)
17266 This command overrides use of the symbol table to determine whether
17267 instructions are ARM or Thumb. The default is @samp{auto}, which
17268 causes @value{GDBN} to use the symbol table and then the setting
17269 of @samp{set arm fallback-mode}.
17271 @item show arm force-mode
17272 Show the current forced instruction mode.
17274 @item set debug arm
17275 Toggle whether to display ARM-specific debugging messages from the ARM
17276 target support subsystem.
17278 @item show debug arm
17279 Show whether ARM-specific debugging messages are enabled.
17282 The following commands are available when an ARM target is debugged
17283 using the RDI interface:
17286 @item rdilogfile @r{[}@var{file}@r{]}
17288 @cindex ADP (Angel Debugger Protocol) logging
17289 Set the filename for the ADP (Angel Debugger Protocol) packet log.
17290 With an argument, sets the log file to the specified @var{file}. With
17291 no argument, show the current log file name. The default log file is
17294 @item rdilogenable @r{[}@var{arg}@r{]}
17295 @kindex rdilogenable
17296 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
17297 enables logging, with an argument 0 or @code{"no"} disables it. With
17298 no arguments displays the current setting. When logging is enabled,
17299 ADP packets exchanged between @value{GDBN} and the RDI target device
17300 are logged to a file.
17302 @item set rdiromatzero
17303 @kindex set rdiromatzero
17304 @cindex ROM at zero address, RDI
17305 Tell @value{GDBN} whether the target has ROM at address 0. If on,
17306 vector catching is disabled, so that zero address can be used. If off
17307 (the default), vector catching is enabled. For this command to take
17308 effect, it needs to be invoked prior to the @code{target rdi} command.
17310 @item show rdiromatzero
17311 @kindex show rdiromatzero
17312 Show the current setting of ROM at zero address.
17314 @item set rdiheartbeat
17315 @kindex set rdiheartbeat
17316 @cindex RDI heartbeat
17317 Enable or disable RDI heartbeat packets. It is not recommended to
17318 turn on this option, since it confuses ARM and EPI JTAG interface, as
17319 well as the Angel monitor.
17321 @item show rdiheartbeat
17322 @kindex show rdiheartbeat
17323 Show the setting of RDI heartbeat packets.
17327 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17328 The @value{GDBN} ARM simulator accepts the following optional arguments.
17331 @item --swi-support=@var{type}
17332 Tell the simulator which SWI interfaces to support.
17333 @var{type} may be a comma separated list of the following values.
17334 The default value is @code{all}.
17347 @subsection Renesas M32R/D and M32R/SDI
17350 @kindex target m32r
17351 @item target m32r @var{dev}
17352 Renesas M32R/D ROM monitor.
17354 @kindex target m32rsdi
17355 @item target m32rsdi @var{dev}
17356 Renesas M32R SDI server, connected via parallel port to the board.
17359 The following @value{GDBN} commands are specific to the M32R monitor:
17362 @item set download-path @var{path}
17363 @kindex set download-path
17364 @cindex find downloadable @sc{srec} files (M32R)
17365 Set the default path for finding downloadable @sc{srec} files.
17367 @item show download-path
17368 @kindex show download-path
17369 Show the default path for downloadable @sc{srec} files.
17371 @item set board-address @var{addr}
17372 @kindex set board-address
17373 @cindex M32-EVA target board address
17374 Set the IP address for the M32R-EVA target board.
17376 @item show board-address
17377 @kindex show board-address
17378 Show the current IP address of the target board.
17380 @item set server-address @var{addr}
17381 @kindex set server-address
17382 @cindex download server address (M32R)
17383 Set the IP address for the download server, which is the @value{GDBN}'s
17386 @item show server-address
17387 @kindex show server-address
17388 Display the IP address of the download server.
17390 @item upload @r{[}@var{file}@r{]}
17391 @kindex upload@r{, M32R}
17392 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
17393 upload capability. If no @var{file} argument is given, the current
17394 executable file is uploaded.
17396 @item tload @r{[}@var{file}@r{]}
17397 @kindex tload@r{, M32R}
17398 Test the @code{upload} command.
17401 The following commands are available for M32R/SDI:
17406 @cindex reset SDI connection, M32R
17407 This command resets the SDI connection.
17411 This command shows the SDI connection status.
17414 @kindex debug_chaos
17415 @cindex M32R/Chaos debugging
17416 Instructs the remote that M32R/Chaos debugging is to be used.
17418 @item use_debug_dma
17419 @kindex use_debug_dma
17420 Instructs the remote to use the DEBUG_DMA method of accessing memory.
17423 @kindex use_mon_code
17424 Instructs the remote to use the MON_CODE method of accessing memory.
17427 @kindex use_ib_break
17428 Instructs the remote to set breakpoints by IB break.
17430 @item use_dbt_break
17431 @kindex use_dbt_break
17432 Instructs the remote to set breakpoints by DBT.
17438 The Motorola m68k configuration includes ColdFire support, and a
17439 target command for the following ROM monitor.
17443 @kindex target dbug
17444 @item target dbug @var{dev}
17445 dBUG ROM monitor for Motorola ColdFire.
17450 @subsection MicroBlaze
17451 @cindex Xilinx MicroBlaze
17452 @cindex XMD, Xilinx Microprocessor Debugger
17454 The MicroBlaze is a soft-core processor supported on various Xilinx
17455 FPGAs, such as Spartan or Virtex series. Boards with these processors
17456 usually have JTAG ports which connect to a host system running the Xilinx
17457 Embedded Development Kit (EDK) or Software Development Kit (SDK).
17458 This host system is used to download the configuration bitstream to
17459 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
17460 communicates with the target board using the JTAG interface and
17461 presents a @code{gdbserver} interface to the board. By default
17462 @code{xmd} uses port @code{1234}. (While it is possible to change
17463 this default port, it requires the use of undocumented @code{xmd}
17464 commands. Contact Xilinx support if you need to do this.)
17466 Use these GDB commands to connect to the MicroBlaze target processor.
17469 @item target remote :1234
17470 Use this command to connect to the target if you are running @value{GDBN}
17471 on the same system as @code{xmd}.
17473 @item target remote @var{xmd-host}:1234
17474 Use this command to connect to the target if it is connected to @code{xmd}
17475 running on a different system named @var{xmd-host}.
17478 Use this command to download a program to the MicroBlaze target.
17480 @item set debug microblaze @var{n}
17481 Enable MicroBlaze-specific debugging messages if non-zero.
17483 @item show debug microblaze @var{n}
17484 Show MicroBlaze-specific debugging level.
17487 @node MIPS Embedded
17488 @subsection MIPS Embedded
17490 @cindex MIPS boards
17491 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
17492 MIPS board attached to a serial line. This is available when
17493 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
17496 Use these @value{GDBN} commands to specify the connection to your target board:
17499 @item target mips @var{port}
17500 @kindex target mips @var{port}
17501 To run a program on the board, start up @code{@value{GDBP}} with the
17502 name of your program as the argument. To connect to the board, use the
17503 command @samp{target mips @var{port}}, where @var{port} is the name of
17504 the serial port connected to the board. If the program has not already
17505 been downloaded to the board, you may use the @code{load} command to
17506 download it. You can then use all the usual @value{GDBN} commands.
17508 For example, this sequence connects to the target board through a serial
17509 port, and loads and runs a program called @var{prog} through the
17513 host$ @value{GDBP} @var{prog}
17514 @value{GDBN} is free software and @dots{}
17515 (@value{GDBP}) target mips /dev/ttyb
17516 (@value{GDBP}) load @var{prog}
17520 @item target mips @var{hostname}:@var{portnumber}
17521 On some @value{GDBN} host configurations, you can specify a TCP
17522 connection (for instance, to a serial line managed by a terminal
17523 concentrator) instead of a serial port, using the syntax
17524 @samp{@var{hostname}:@var{portnumber}}.
17526 @item target pmon @var{port}
17527 @kindex target pmon @var{port}
17530 @item target ddb @var{port}
17531 @kindex target ddb @var{port}
17532 NEC's DDB variant of PMON for Vr4300.
17534 @item target lsi @var{port}
17535 @kindex target lsi @var{port}
17536 LSI variant of PMON.
17538 @kindex target r3900
17539 @item target r3900 @var{dev}
17540 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
17542 @kindex target array
17543 @item target array @var{dev}
17544 Array Tech LSI33K RAID controller board.
17550 @value{GDBN} also supports these special commands for MIPS targets:
17553 @item set mipsfpu double
17554 @itemx set mipsfpu single
17555 @itemx set mipsfpu none
17556 @itemx set mipsfpu auto
17557 @itemx show mipsfpu
17558 @kindex set mipsfpu
17559 @kindex show mipsfpu
17560 @cindex MIPS remote floating point
17561 @cindex floating point, MIPS remote
17562 If your target board does not support the MIPS floating point
17563 coprocessor, you should use the command @samp{set mipsfpu none} (if you
17564 need this, you may wish to put the command in your @value{GDBN} init
17565 file). This tells @value{GDBN} how to find the return value of
17566 functions which return floating point values. It also allows
17567 @value{GDBN} to avoid saving the floating point registers when calling
17568 functions on the board. If you are using a floating point coprocessor
17569 with only single precision floating point support, as on the @sc{r4650}
17570 processor, use the command @samp{set mipsfpu single}. The default
17571 double precision floating point coprocessor may be selected using
17572 @samp{set mipsfpu double}.
17574 In previous versions the only choices were double precision or no
17575 floating point, so @samp{set mipsfpu on} will select double precision
17576 and @samp{set mipsfpu off} will select no floating point.
17578 As usual, you can inquire about the @code{mipsfpu} variable with
17579 @samp{show mipsfpu}.
17581 @item set timeout @var{seconds}
17582 @itemx set retransmit-timeout @var{seconds}
17583 @itemx show timeout
17584 @itemx show retransmit-timeout
17585 @cindex @code{timeout}, MIPS protocol
17586 @cindex @code{retransmit-timeout}, MIPS protocol
17587 @kindex set timeout
17588 @kindex show timeout
17589 @kindex set retransmit-timeout
17590 @kindex show retransmit-timeout
17591 You can control the timeout used while waiting for a packet, in the MIPS
17592 remote protocol, with the @code{set timeout @var{seconds}} command. The
17593 default is 5 seconds. Similarly, you can control the timeout used while
17594 waiting for an acknowledgment of a packet with the @code{set
17595 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
17596 You can inspect both values with @code{show timeout} and @code{show
17597 retransmit-timeout}. (These commands are @emph{only} available when
17598 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
17600 The timeout set by @code{set timeout} does not apply when @value{GDBN}
17601 is waiting for your program to stop. In that case, @value{GDBN} waits
17602 forever because it has no way of knowing how long the program is going
17603 to run before stopping.
17605 @item set syn-garbage-limit @var{num}
17606 @kindex set syn-garbage-limit@r{, MIPS remote}
17607 @cindex synchronize with remote MIPS target
17608 Limit the maximum number of characters @value{GDBN} should ignore when
17609 it tries to synchronize with the remote target. The default is 10
17610 characters. Setting the limit to -1 means there's no limit.
17612 @item show syn-garbage-limit
17613 @kindex show syn-garbage-limit@r{, MIPS remote}
17614 Show the current limit on the number of characters to ignore when
17615 trying to synchronize with the remote system.
17617 @item set monitor-prompt @var{prompt}
17618 @kindex set monitor-prompt@r{, MIPS remote}
17619 @cindex remote monitor prompt
17620 Tell @value{GDBN} to expect the specified @var{prompt} string from the
17621 remote monitor. The default depends on the target:
17631 @item show monitor-prompt
17632 @kindex show monitor-prompt@r{, MIPS remote}
17633 Show the current strings @value{GDBN} expects as the prompt from the
17636 @item set monitor-warnings
17637 @kindex set monitor-warnings@r{, MIPS remote}
17638 Enable or disable monitor warnings about hardware breakpoints. This
17639 has effect only for the @code{lsi} target. When on, @value{GDBN} will
17640 display warning messages whose codes are returned by the @code{lsi}
17641 PMON monitor for breakpoint commands.
17643 @item show monitor-warnings
17644 @kindex show monitor-warnings@r{, MIPS remote}
17645 Show the current setting of printing monitor warnings.
17647 @item pmon @var{command}
17648 @kindex pmon@r{, MIPS remote}
17649 @cindex send PMON command
17650 This command allows sending an arbitrary @var{command} string to the
17651 monitor. The monitor must be in debug mode for this to work.
17654 @node OpenRISC 1000
17655 @subsection OpenRISC 1000
17656 @cindex OpenRISC 1000
17658 @cindex or1k boards
17659 See OR1k Architecture document (@uref{www.opencores.org}) for more information
17660 about platform and commands.
17664 @kindex target jtag
17665 @item target jtag jtag://@var{host}:@var{port}
17667 Connects to remote JTAG server.
17668 JTAG remote server can be either an or1ksim or JTAG server,
17669 connected via parallel port to the board.
17671 Example: @code{target jtag jtag://localhost:9999}
17674 @item or1ksim @var{command}
17675 If connected to @code{or1ksim} OpenRISC 1000 Architectural
17676 Simulator, proprietary commands can be executed.
17678 @kindex info or1k spr
17679 @item info or1k spr
17680 Displays spr groups.
17682 @item info or1k spr @var{group}
17683 @itemx info or1k spr @var{groupno}
17684 Displays register names in selected group.
17686 @item info or1k spr @var{group} @var{register}
17687 @itemx info or1k spr @var{register}
17688 @itemx info or1k spr @var{groupno} @var{registerno}
17689 @itemx info or1k spr @var{registerno}
17690 Shows information about specified spr register.
17693 @item spr @var{group} @var{register} @var{value}
17694 @itemx spr @var{register @var{value}}
17695 @itemx spr @var{groupno} @var{registerno @var{value}}
17696 @itemx spr @var{registerno @var{value}}
17697 Writes @var{value} to specified spr register.
17700 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
17701 It is very similar to @value{GDBN} trace, except it does not interfere with normal
17702 program execution and is thus much faster. Hardware breakpoints/watchpoint
17703 triggers can be set using:
17706 Load effective address/data
17708 Store effective address/data
17710 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
17715 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
17716 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
17718 @code{htrace} commands:
17719 @cindex OpenRISC 1000 htrace
17722 @item hwatch @var{conditional}
17723 Set hardware watchpoint on combination of Load/Store Effective Address(es)
17724 or Data. For example:
17726 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17728 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17732 Display information about current HW trace configuration.
17734 @item htrace trigger @var{conditional}
17735 Set starting criteria for HW trace.
17737 @item htrace qualifier @var{conditional}
17738 Set acquisition qualifier for HW trace.
17740 @item htrace stop @var{conditional}
17741 Set HW trace stopping criteria.
17743 @item htrace record [@var{data}]*
17744 Selects the data to be recorded, when qualifier is met and HW trace was
17747 @item htrace enable
17748 @itemx htrace disable
17749 Enables/disables the HW trace.
17751 @item htrace rewind [@var{filename}]
17752 Clears currently recorded trace data.
17754 If filename is specified, new trace file is made and any newly collected data
17755 will be written there.
17757 @item htrace print [@var{start} [@var{len}]]
17758 Prints trace buffer, using current record configuration.
17760 @item htrace mode continuous
17761 Set continuous trace mode.
17763 @item htrace mode suspend
17764 Set suspend trace mode.
17768 @node PowerPC Embedded
17769 @subsection PowerPC Embedded
17771 @value{GDBN} provides the following PowerPC-specific commands:
17774 @kindex set powerpc
17775 @item set powerpc soft-float
17776 @itemx show powerpc soft-float
17777 Force @value{GDBN} to use (or not use) a software floating point calling
17778 convention. By default, @value{GDBN} selects the calling convention based
17779 on the selected architecture and the provided executable file.
17781 @item set powerpc vector-abi
17782 @itemx show powerpc vector-abi
17783 Force @value{GDBN} to use the specified calling convention for vector
17784 arguments and return values. The valid options are @samp{auto};
17785 @samp{generic}, to avoid vector registers even if they are present;
17786 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
17787 registers. By default, @value{GDBN} selects the calling convention
17788 based on the selected architecture and the provided executable file.
17790 @kindex target dink32
17791 @item target dink32 @var{dev}
17792 DINK32 ROM monitor.
17794 @kindex target ppcbug
17795 @item target ppcbug @var{dev}
17796 @kindex target ppcbug1
17797 @item target ppcbug1 @var{dev}
17798 PPCBUG ROM monitor for PowerPC.
17801 @item target sds @var{dev}
17802 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
17805 @cindex SDS protocol
17806 The following commands specific to the SDS protocol are supported
17810 @item set sdstimeout @var{nsec}
17811 @kindex set sdstimeout
17812 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
17813 default is 2 seconds.
17815 @item show sdstimeout
17816 @kindex show sdstimeout
17817 Show the current value of the SDS timeout.
17819 @item sds @var{command}
17820 @kindex sds@r{, a command}
17821 Send the specified @var{command} string to the SDS monitor.
17826 @subsection HP PA Embedded
17830 @kindex target op50n
17831 @item target op50n @var{dev}
17832 OP50N monitor, running on an OKI HPPA board.
17834 @kindex target w89k
17835 @item target w89k @var{dev}
17836 W89K monitor, running on a Winbond HPPA board.
17841 @subsection Tsqware Sparclet
17845 @value{GDBN} enables developers to debug tasks running on
17846 Sparclet targets from a Unix host.
17847 @value{GDBN} uses code that runs on
17848 both the Unix host and on the Sparclet target. The program
17849 @code{@value{GDBP}} is installed and executed on the Unix host.
17852 @item remotetimeout @var{args}
17853 @kindex remotetimeout
17854 @value{GDBN} supports the option @code{remotetimeout}.
17855 This option is set by the user, and @var{args} represents the number of
17856 seconds @value{GDBN} waits for responses.
17859 @cindex compiling, on Sparclet
17860 When compiling for debugging, include the options @samp{-g} to get debug
17861 information and @samp{-Ttext} to relocate the program to where you wish to
17862 load it on the target. You may also want to add the options @samp{-n} or
17863 @samp{-N} in order to reduce the size of the sections. Example:
17866 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
17869 You can use @code{objdump} to verify that the addresses are what you intended:
17872 sparclet-aout-objdump --headers --syms prog
17875 @cindex running, on Sparclet
17877 your Unix execution search path to find @value{GDBN}, you are ready to
17878 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
17879 (or @code{sparclet-aout-gdb}, depending on your installation).
17881 @value{GDBN} comes up showing the prompt:
17888 * Sparclet File:: Setting the file to debug
17889 * Sparclet Connection:: Connecting to Sparclet
17890 * Sparclet Download:: Sparclet download
17891 * Sparclet Execution:: Running and debugging
17894 @node Sparclet File
17895 @subsubsection Setting File to Debug
17897 The @value{GDBN} command @code{file} lets you choose with program to debug.
17900 (gdbslet) file prog
17904 @value{GDBN} then attempts to read the symbol table of @file{prog}.
17905 @value{GDBN} locates
17906 the file by searching the directories listed in the command search
17908 If the file was compiled with debug information (option @samp{-g}), source
17909 files will be searched as well.
17910 @value{GDBN} locates
17911 the source files by searching the directories listed in the directory search
17912 path (@pxref{Environment, ,Your Program's Environment}).
17914 to find a file, it displays a message such as:
17917 prog: No such file or directory.
17920 When this happens, add the appropriate directories to the search paths with
17921 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
17922 @code{target} command again.
17924 @node Sparclet Connection
17925 @subsubsection Connecting to Sparclet
17927 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
17928 To connect to a target on serial port ``@code{ttya}'', type:
17931 (gdbslet) target sparclet /dev/ttya
17932 Remote target sparclet connected to /dev/ttya
17933 main () at ../prog.c:3
17937 @value{GDBN} displays messages like these:
17943 @node Sparclet Download
17944 @subsubsection Sparclet Download
17946 @cindex download to Sparclet
17947 Once connected to the Sparclet target,
17948 you can use the @value{GDBN}
17949 @code{load} command to download the file from the host to the target.
17950 The file name and load offset should be given as arguments to the @code{load}
17952 Since the file format is aout, the program must be loaded to the starting
17953 address. You can use @code{objdump} to find out what this value is. The load
17954 offset is an offset which is added to the VMA (virtual memory address)
17955 of each of the file's sections.
17956 For instance, if the program
17957 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
17958 and bss at 0x12010170, in @value{GDBN}, type:
17961 (gdbslet) load prog 0x12010000
17962 Loading section .text, size 0xdb0 vma 0x12010000
17965 If the code is loaded at a different address then what the program was linked
17966 to, you may need to use the @code{section} and @code{add-symbol-file} commands
17967 to tell @value{GDBN} where to map the symbol table.
17969 @node Sparclet Execution
17970 @subsubsection Running and Debugging
17972 @cindex running and debugging Sparclet programs
17973 You can now begin debugging the task using @value{GDBN}'s execution control
17974 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
17975 manual for the list of commands.
17979 Breakpoint 1 at 0x12010000: file prog.c, line 3.
17981 Starting program: prog
17982 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
17983 3 char *symarg = 0;
17985 4 char *execarg = "hello!";
17990 @subsection Fujitsu Sparclite
17994 @kindex target sparclite
17995 @item target sparclite @var{dev}
17996 Fujitsu sparclite boards, used only for the purpose of loading.
17997 You must use an additional command to debug the program.
17998 For example: target remote @var{dev} using @value{GDBN} standard
18004 @subsection Zilog Z8000
18007 @cindex simulator, Z8000
18008 @cindex Zilog Z8000 simulator
18010 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
18013 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
18014 unsegmented variant of the Z8000 architecture) or the Z8001 (the
18015 segmented variant). The simulator recognizes which architecture is
18016 appropriate by inspecting the object code.
18019 @item target sim @var{args}
18021 @kindex target sim@r{, with Z8000}
18022 Debug programs on a simulated CPU. If the simulator supports setup
18023 options, specify them via @var{args}.
18027 After specifying this target, you can debug programs for the simulated
18028 CPU in the same style as programs for your host computer; use the
18029 @code{file} command to load a new program image, the @code{run} command
18030 to run your program, and so on.
18032 As well as making available all the usual machine registers
18033 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18034 additional items of information as specially named registers:
18039 Counts clock-ticks in the simulator.
18042 Counts instructions run in the simulator.
18045 Execution time in 60ths of a second.
18049 You can refer to these values in @value{GDBN} expressions with the usual
18050 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18051 conditional breakpoint that suspends only after at least 5000
18052 simulated clock ticks.
18055 @subsection Atmel AVR
18058 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18059 following AVR-specific commands:
18062 @item info io_registers
18063 @kindex info io_registers@r{, AVR}
18064 @cindex I/O registers (Atmel AVR)
18065 This command displays information about the AVR I/O registers. For
18066 each register, @value{GDBN} prints its number and value.
18073 When configured for debugging CRIS, @value{GDBN} provides the
18074 following CRIS-specific commands:
18077 @item set cris-version @var{ver}
18078 @cindex CRIS version
18079 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
18080 The CRIS version affects register names and sizes. This command is useful in
18081 case autodetection of the CRIS version fails.
18083 @item show cris-version
18084 Show the current CRIS version.
18086 @item set cris-dwarf2-cfi
18087 @cindex DWARF-2 CFI and CRIS
18088 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
18089 Change to @samp{off} when using @code{gcc-cris} whose version is below
18092 @item show cris-dwarf2-cfi
18093 Show the current state of using DWARF-2 CFI.
18095 @item set cris-mode @var{mode}
18097 Set the current CRIS mode to @var{mode}. It should only be changed when
18098 debugging in guru mode, in which case it should be set to
18099 @samp{guru} (the default is @samp{normal}).
18101 @item show cris-mode
18102 Show the current CRIS mode.
18106 @subsection Renesas Super-H
18109 For the Renesas Super-H processor, @value{GDBN} provides these
18114 @kindex regs@r{, Super-H}
18115 Show the values of all Super-H registers.
18117 @item set sh calling-convention @var{convention}
18118 @kindex set sh calling-convention
18119 Set the calling-convention used when calling functions from @value{GDBN}.
18120 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
18121 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
18122 convention. If the DWARF-2 information of the called function specifies
18123 that the function follows the Renesas calling convention, the function
18124 is called using the Renesas calling convention. If the calling convention
18125 is set to @samp{renesas}, the Renesas calling convention is always used,
18126 regardless of the DWARF-2 information. This can be used to override the
18127 default of @samp{gcc} if debug information is missing, or the compiler
18128 does not emit the DWARF-2 calling convention entry for a function.
18130 @item show sh calling-convention
18131 @kindex show sh calling-convention
18132 Show the current calling convention setting.
18137 @node Architectures
18138 @section Architectures
18140 This section describes characteristics of architectures that affect
18141 all uses of @value{GDBN} with the architecture, both native and cross.
18148 * HPPA:: HP PA architecture
18149 * SPU:: Cell Broadband Engine SPU architecture
18154 @subsection x86 Architecture-specific Issues
18157 @item set struct-convention @var{mode}
18158 @kindex set struct-convention
18159 @cindex struct return convention
18160 @cindex struct/union returned in registers
18161 Set the convention used by the inferior to return @code{struct}s and
18162 @code{union}s from functions to @var{mode}. Possible values of
18163 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
18164 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
18165 are returned on the stack, while @code{"reg"} means that a
18166 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
18167 be returned in a register.
18169 @item show struct-convention
18170 @kindex show struct-convention
18171 Show the current setting of the convention to return @code{struct}s
18180 @kindex set rstack_high_address
18181 @cindex AMD 29K register stack
18182 @cindex register stack, AMD29K
18183 @item set rstack_high_address @var{address}
18184 On AMD 29000 family processors, registers are saved in a separate
18185 @dfn{register stack}. There is no way for @value{GDBN} to determine the
18186 extent of this stack. Normally, @value{GDBN} just assumes that the
18187 stack is ``large enough''. This may result in @value{GDBN} referencing
18188 memory locations that do not exist. If necessary, you can get around
18189 this problem by specifying the ending address of the register stack with
18190 the @code{set rstack_high_address} command. The argument should be an
18191 address, which you probably want to precede with @samp{0x} to specify in
18194 @kindex show rstack_high_address
18195 @item show rstack_high_address
18196 Display the current limit of the register stack, on AMD 29000 family
18204 See the following section.
18209 @cindex stack on Alpha
18210 @cindex stack on MIPS
18211 @cindex Alpha stack
18213 Alpha- and MIPS-based computers use an unusual stack frame, which
18214 sometimes requires @value{GDBN} to search backward in the object code to
18215 find the beginning of a function.
18217 @cindex response time, MIPS debugging
18218 To improve response time (especially for embedded applications, where
18219 @value{GDBN} may be restricted to a slow serial line for this search)
18220 you may want to limit the size of this search, using one of these
18224 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
18225 @item set heuristic-fence-post @var{limit}
18226 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
18227 search for the beginning of a function. A value of @var{0} (the
18228 default) means there is no limit. However, except for @var{0}, the
18229 larger the limit the more bytes @code{heuristic-fence-post} must search
18230 and therefore the longer it takes to run. You should only need to use
18231 this command when debugging a stripped executable.
18233 @item show heuristic-fence-post
18234 Display the current limit.
18238 These commands are available @emph{only} when @value{GDBN} is configured
18239 for debugging programs on Alpha or MIPS processors.
18241 Several MIPS-specific commands are available when debugging MIPS
18245 @item set mips abi @var{arg}
18246 @kindex set mips abi
18247 @cindex set ABI for MIPS
18248 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
18249 values of @var{arg} are:
18253 The default ABI associated with the current binary (this is the
18264 @item show mips abi
18265 @kindex show mips abi
18266 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
18269 @itemx show mipsfpu
18270 @xref{MIPS Embedded, set mipsfpu}.
18272 @item set mips mask-address @var{arg}
18273 @kindex set mips mask-address
18274 @cindex MIPS addresses, masking
18275 This command determines whether the most-significant 32 bits of 64-bit
18276 MIPS addresses are masked off. The argument @var{arg} can be
18277 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
18278 setting, which lets @value{GDBN} determine the correct value.
18280 @item show mips mask-address
18281 @kindex show mips mask-address
18282 Show whether the upper 32 bits of MIPS addresses are masked off or
18285 @item set remote-mips64-transfers-32bit-regs
18286 @kindex set remote-mips64-transfers-32bit-regs
18287 This command controls compatibility with 64-bit MIPS targets that
18288 transfer data in 32-bit quantities. If you have an old MIPS 64 target
18289 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
18290 and 64 bits for other registers, set this option to @samp{on}.
18292 @item show remote-mips64-transfers-32bit-regs
18293 @kindex show remote-mips64-transfers-32bit-regs
18294 Show the current setting of compatibility with older MIPS 64 targets.
18296 @item set debug mips
18297 @kindex set debug mips
18298 This command turns on and off debugging messages for the MIPS-specific
18299 target code in @value{GDBN}.
18301 @item show debug mips
18302 @kindex show debug mips
18303 Show the current setting of MIPS debugging messages.
18309 @cindex HPPA support
18311 When @value{GDBN} is debugging the HP PA architecture, it provides the
18312 following special commands:
18315 @item set debug hppa
18316 @kindex set debug hppa
18317 This command determines whether HPPA architecture-specific debugging
18318 messages are to be displayed.
18320 @item show debug hppa
18321 Show whether HPPA debugging messages are displayed.
18323 @item maint print unwind @var{address}
18324 @kindex maint print unwind@r{, HPPA}
18325 This command displays the contents of the unwind table entry at the
18326 given @var{address}.
18332 @subsection Cell Broadband Engine SPU architecture
18333 @cindex Cell Broadband Engine
18336 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
18337 it provides the following special commands:
18340 @item info spu event
18342 Display SPU event facility status. Shows current event mask
18343 and pending event status.
18345 @item info spu signal
18346 Display SPU signal notification facility status. Shows pending
18347 signal-control word and signal notification mode of both signal
18348 notification channels.
18350 @item info spu mailbox
18351 Display SPU mailbox facility status. Shows all pending entries,
18352 in order of processing, in each of the SPU Write Outbound,
18353 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
18356 Display MFC DMA status. Shows all pending commands in the MFC
18357 DMA queue. For each entry, opcode, tag, class IDs, effective
18358 and local store addresses and transfer size are shown.
18360 @item info spu proxydma
18361 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
18362 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
18363 and local store addresses and transfer size are shown.
18367 When @value{GDBN} is debugging a combined PowerPC/SPU application
18368 on the Cell Broadband Engine, it provides in addition the following
18372 @item set spu stop-on-load @var{arg}
18374 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
18375 will give control to the user when a new SPE thread enters its @code{main}
18376 function. The default is @code{off}.
18378 @item show spu stop-on-load
18380 Show whether to stop for new SPE threads.
18382 @item set spu auto-flush-cache @var{arg}
18383 Set whether to automatically flush the software-managed cache. When set to
18384 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
18385 cache to be flushed whenever SPE execution stops. This provides a consistent
18386 view of PowerPC memory that is accessed via the cache. If an application
18387 does not use the software-managed cache, this option has no effect.
18389 @item show spu auto-flush-cache
18390 Show whether to automatically flush the software-managed cache.
18395 @subsection PowerPC
18396 @cindex PowerPC architecture
18398 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
18399 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
18400 numbers stored in the floating point registers. These values must be stored
18401 in two consecutive registers, always starting at an even register like
18402 @code{f0} or @code{f2}.
18404 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
18405 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
18406 @code{f2} and @code{f3} for @code{$dl1} and so on.
18408 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
18409 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
18412 @node Controlling GDB
18413 @chapter Controlling @value{GDBN}
18415 You can alter the way @value{GDBN} interacts with you by using the
18416 @code{set} command. For commands controlling how @value{GDBN} displays
18417 data, see @ref{Print Settings, ,Print Settings}. Other settings are
18422 * Editing:: Command editing
18423 * Command History:: Command history
18424 * Screen Size:: Screen size
18425 * Numbers:: Numbers
18426 * ABI:: Configuring the current ABI
18427 * Messages/Warnings:: Optional warnings and messages
18428 * Debugging Output:: Optional messages about internal happenings
18429 * Other Misc Settings:: Other Miscellaneous Settings
18437 @value{GDBN} indicates its readiness to read a command by printing a string
18438 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
18439 can change the prompt string with the @code{set prompt} command. For
18440 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
18441 the prompt in one of the @value{GDBN} sessions so that you can always tell
18442 which one you are talking to.
18444 @emph{Note:} @code{set prompt} does not add a space for you after the
18445 prompt you set. This allows you to set a prompt which ends in a space
18446 or a prompt that does not.
18450 @item set prompt @var{newprompt}
18451 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
18453 @kindex show prompt
18455 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
18459 @section Command Editing
18461 @cindex command line editing
18463 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
18464 @sc{gnu} library provides consistent behavior for programs which provide a
18465 command line interface to the user. Advantages are @sc{gnu} Emacs-style
18466 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
18467 substitution, and a storage and recall of command history across
18468 debugging sessions.
18470 You may control the behavior of command line editing in @value{GDBN} with the
18471 command @code{set}.
18474 @kindex set editing
18477 @itemx set editing on
18478 Enable command line editing (enabled by default).
18480 @item set editing off
18481 Disable command line editing.
18483 @kindex show editing
18485 Show whether command line editing is enabled.
18488 @xref{Command Line Editing}, for more details about the Readline
18489 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
18490 encouraged to read that chapter.
18492 @node Command History
18493 @section Command History
18494 @cindex command history
18496 @value{GDBN} can keep track of the commands you type during your
18497 debugging sessions, so that you can be certain of precisely what
18498 happened. Use these commands to manage the @value{GDBN} command
18501 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
18502 package, to provide the history facility. @xref{Using History
18503 Interactively}, for the detailed description of the History library.
18505 To issue a command to @value{GDBN} without affecting certain aspects of
18506 the state which is seen by users, prefix it with @samp{server }
18507 (@pxref{Server Prefix}). This
18508 means that this command will not affect the command history, nor will it
18509 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18510 pressed on a line by itself.
18512 @cindex @code{server}, command prefix
18513 The server prefix does not affect the recording of values into the value
18514 history; to print a value without recording it into the value history,
18515 use the @code{output} command instead of the @code{print} command.
18517 Here is the description of @value{GDBN} commands related to command
18521 @cindex history substitution
18522 @cindex history file
18523 @kindex set history filename
18524 @cindex @env{GDBHISTFILE}, environment variable
18525 @item set history filename @var{fname}
18526 Set the name of the @value{GDBN} command history file to @var{fname}.
18527 This is the file where @value{GDBN} reads an initial command history
18528 list, and where it writes the command history from this session when it
18529 exits. You can access this list through history expansion or through
18530 the history command editing characters listed below. This file defaults
18531 to the value of the environment variable @code{GDBHISTFILE}, or to
18532 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
18535 @cindex save command history
18536 @kindex set history save
18537 @item set history save
18538 @itemx set history save on
18539 Record command history in a file, whose name may be specified with the
18540 @code{set history filename} command. By default, this option is disabled.
18542 @item set history save off
18543 Stop recording command history in a file.
18545 @cindex history size
18546 @kindex set history size
18547 @cindex @env{HISTSIZE}, environment variable
18548 @item set history size @var{size}
18549 Set the number of commands which @value{GDBN} keeps in its history list.
18550 This defaults to the value of the environment variable
18551 @code{HISTSIZE}, or to 256 if this variable is not set.
18554 History expansion assigns special meaning to the character @kbd{!}.
18555 @xref{Event Designators}, for more details.
18557 @cindex history expansion, turn on/off
18558 Since @kbd{!} is also the logical not operator in C, history expansion
18559 is off by default. If you decide to enable history expansion with the
18560 @code{set history expansion on} command, you may sometimes need to
18561 follow @kbd{!} (when it is used as logical not, in an expression) with
18562 a space or a tab to prevent it from being expanded. The readline
18563 history facilities do not attempt substitution on the strings
18564 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
18566 The commands to control history expansion are:
18569 @item set history expansion on
18570 @itemx set history expansion
18571 @kindex set history expansion
18572 Enable history expansion. History expansion is off by default.
18574 @item set history expansion off
18575 Disable history expansion.
18578 @kindex show history
18580 @itemx show history filename
18581 @itemx show history save
18582 @itemx show history size
18583 @itemx show history expansion
18584 These commands display the state of the @value{GDBN} history parameters.
18585 @code{show history} by itself displays all four states.
18590 @kindex show commands
18591 @cindex show last commands
18592 @cindex display command history
18593 @item show commands
18594 Display the last ten commands in the command history.
18596 @item show commands @var{n}
18597 Print ten commands centered on command number @var{n}.
18599 @item show commands +
18600 Print ten commands just after the commands last printed.
18604 @section Screen Size
18605 @cindex size of screen
18606 @cindex pauses in output
18608 Certain commands to @value{GDBN} may produce large amounts of
18609 information output to the screen. To help you read all of it,
18610 @value{GDBN} pauses and asks you for input at the end of each page of
18611 output. Type @key{RET} when you want to continue the output, or @kbd{q}
18612 to discard the remaining output. Also, the screen width setting
18613 determines when to wrap lines of output. Depending on what is being
18614 printed, @value{GDBN} tries to break the line at a readable place,
18615 rather than simply letting it overflow onto the following line.
18617 Normally @value{GDBN} knows the size of the screen from the terminal
18618 driver software. For example, on Unix @value{GDBN} uses the termcap data base
18619 together with the value of the @code{TERM} environment variable and the
18620 @code{stty rows} and @code{stty cols} settings. If this is not correct,
18621 you can override it with the @code{set height} and @code{set
18628 @kindex show height
18629 @item set height @var{lpp}
18631 @itemx set width @var{cpl}
18633 These @code{set} commands specify a screen height of @var{lpp} lines and
18634 a screen width of @var{cpl} characters. The associated @code{show}
18635 commands display the current settings.
18637 If you specify a height of zero lines, @value{GDBN} does not pause during
18638 output no matter how long the output is. This is useful if output is to a
18639 file or to an editor buffer.
18641 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
18642 from wrapping its output.
18644 @item set pagination on
18645 @itemx set pagination off
18646 @kindex set pagination
18647 Turn the output pagination on or off; the default is on. Turning
18648 pagination off is the alternative to @code{set height 0}. Note that
18649 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
18650 Options, -batch}) also automatically disables pagination.
18652 @item show pagination
18653 @kindex show pagination
18654 Show the current pagination mode.
18659 @cindex number representation
18660 @cindex entering numbers
18662 You can always enter numbers in octal, decimal, or hexadecimal in
18663 @value{GDBN} by the usual conventions: octal numbers begin with
18664 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
18665 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
18666 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
18667 10; likewise, the default display for numbers---when no particular
18668 format is specified---is base 10. You can change the default base for
18669 both input and output with the commands described below.
18672 @kindex set input-radix
18673 @item set input-radix @var{base}
18674 Set the default base for numeric input. Supported choices
18675 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18676 specified either unambiguously or using the current input radix; for
18680 set input-radix 012
18681 set input-radix 10.
18682 set input-radix 0xa
18686 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
18687 leaves the input radix unchanged, no matter what it was, since
18688 @samp{10}, being without any leading or trailing signs of its base, is
18689 interpreted in the current radix. Thus, if the current radix is 16,
18690 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
18693 @kindex set output-radix
18694 @item set output-radix @var{base}
18695 Set the default base for numeric display. Supported choices
18696 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18697 specified either unambiguously or using the current input radix.
18699 @kindex show input-radix
18700 @item show input-radix
18701 Display the current default base for numeric input.
18703 @kindex show output-radix
18704 @item show output-radix
18705 Display the current default base for numeric display.
18707 @item set radix @r{[}@var{base}@r{]}
18711 These commands set and show the default base for both input and output
18712 of numbers. @code{set radix} sets the radix of input and output to
18713 the same base; without an argument, it resets the radix back to its
18714 default value of 10.
18719 @section Configuring the Current ABI
18721 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
18722 application automatically. However, sometimes you need to override its
18723 conclusions. Use these commands to manage @value{GDBN}'s view of the
18730 One @value{GDBN} configuration can debug binaries for multiple operating
18731 system targets, either via remote debugging or native emulation.
18732 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
18733 but you can override its conclusion using the @code{set osabi} command.
18734 One example where this is useful is in debugging of binaries which use
18735 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
18736 not have the same identifying marks that the standard C library for your
18741 Show the OS ABI currently in use.
18744 With no argument, show the list of registered available OS ABI's.
18746 @item set osabi @var{abi}
18747 Set the current OS ABI to @var{abi}.
18750 @cindex float promotion
18752 Generally, the way that an argument of type @code{float} is passed to a
18753 function depends on whether the function is prototyped. For a prototyped
18754 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
18755 according to the architecture's convention for @code{float}. For unprototyped
18756 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
18757 @code{double} and then passed.
18759 Unfortunately, some forms of debug information do not reliably indicate whether
18760 a function is prototyped. If @value{GDBN} calls a function that is not marked
18761 as prototyped, it consults @kbd{set coerce-float-to-double}.
18764 @kindex set coerce-float-to-double
18765 @item set coerce-float-to-double
18766 @itemx set coerce-float-to-double on
18767 Arguments of type @code{float} will be promoted to @code{double} when passed
18768 to an unprototyped function. This is the default setting.
18770 @item set coerce-float-to-double off
18771 Arguments of type @code{float} will be passed directly to unprototyped
18774 @kindex show coerce-float-to-double
18775 @item show coerce-float-to-double
18776 Show the current setting of promoting @code{float} to @code{double}.
18780 @kindex show cp-abi
18781 @value{GDBN} needs to know the ABI used for your program's C@t{++}
18782 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
18783 used to build your application. @value{GDBN} only fully supports
18784 programs with a single C@t{++} ABI; if your program contains code using
18785 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
18786 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
18787 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
18788 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
18789 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
18790 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
18795 Show the C@t{++} ABI currently in use.
18798 With no argument, show the list of supported C@t{++} ABI's.
18800 @item set cp-abi @var{abi}
18801 @itemx set cp-abi auto
18802 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
18805 @node Messages/Warnings
18806 @section Optional Warnings and Messages
18808 @cindex verbose operation
18809 @cindex optional warnings
18810 By default, @value{GDBN} is silent about its inner workings. If you are
18811 running on a slow machine, you may want to use the @code{set verbose}
18812 command. This makes @value{GDBN} tell you when it does a lengthy
18813 internal operation, so you will not think it has crashed.
18815 Currently, the messages controlled by @code{set verbose} are those
18816 which announce that the symbol table for a source file is being read;
18817 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
18820 @kindex set verbose
18821 @item set verbose on
18822 Enables @value{GDBN} output of certain informational messages.
18824 @item set verbose off
18825 Disables @value{GDBN} output of certain informational messages.
18827 @kindex show verbose
18829 Displays whether @code{set verbose} is on or off.
18832 By default, if @value{GDBN} encounters bugs in the symbol table of an
18833 object file, it is silent; but if you are debugging a compiler, you may
18834 find this information useful (@pxref{Symbol Errors, ,Errors Reading
18839 @kindex set complaints
18840 @item set complaints @var{limit}
18841 Permits @value{GDBN} to output @var{limit} complaints about each type of
18842 unusual symbols before becoming silent about the problem. Set
18843 @var{limit} to zero to suppress all complaints; set it to a large number
18844 to prevent complaints from being suppressed.
18846 @kindex show complaints
18847 @item show complaints
18848 Displays how many symbol complaints @value{GDBN} is permitted to produce.
18852 @anchor{confirmation requests}
18853 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
18854 lot of stupid questions to confirm certain commands. For example, if
18855 you try to run a program which is already running:
18859 The program being debugged has been started already.
18860 Start it from the beginning? (y or n)
18863 If you are willing to unflinchingly face the consequences of your own
18864 commands, you can disable this ``feature'':
18868 @kindex set confirm
18870 @cindex confirmation
18871 @cindex stupid questions
18872 @item set confirm off
18873 Disables confirmation requests. Note that running @value{GDBN} with
18874 the @option{--batch} option (@pxref{Mode Options, -batch}) also
18875 automatically disables confirmation requests.
18877 @item set confirm on
18878 Enables confirmation requests (the default).
18880 @kindex show confirm
18882 Displays state of confirmation requests.
18886 @cindex command tracing
18887 If you need to debug user-defined commands or sourced files you may find it
18888 useful to enable @dfn{command tracing}. In this mode each command will be
18889 printed as it is executed, prefixed with one or more @samp{+} symbols, the
18890 quantity denoting the call depth of each command.
18893 @kindex set trace-commands
18894 @cindex command scripts, debugging
18895 @item set trace-commands on
18896 Enable command tracing.
18897 @item set trace-commands off
18898 Disable command tracing.
18899 @item show trace-commands
18900 Display the current state of command tracing.
18903 @node Debugging Output
18904 @section Optional Messages about Internal Happenings
18905 @cindex optional debugging messages
18907 @value{GDBN} has commands that enable optional debugging messages from
18908 various @value{GDBN} subsystems; normally these commands are of
18909 interest to @value{GDBN} maintainers, or when reporting a bug. This
18910 section documents those commands.
18913 @kindex set exec-done-display
18914 @item set exec-done-display
18915 Turns on or off the notification of asynchronous commands'
18916 completion. When on, @value{GDBN} will print a message when an
18917 asynchronous command finishes its execution. The default is off.
18918 @kindex show exec-done-display
18919 @item show exec-done-display
18920 Displays the current setting of asynchronous command completion
18923 @cindex gdbarch debugging info
18924 @cindex architecture debugging info
18925 @item set debug arch
18926 Turns on or off display of gdbarch debugging info. The default is off
18928 @item show debug arch
18929 Displays the current state of displaying gdbarch debugging info.
18930 @item set debug aix-thread
18931 @cindex AIX threads
18932 Display debugging messages about inner workings of the AIX thread
18934 @item show debug aix-thread
18935 Show the current state of AIX thread debugging info display.
18936 @item set debug dwarf2-die
18937 @cindex DWARF2 DIEs
18938 Dump DWARF2 DIEs after they are read in.
18939 The value is the number of nesting levels to print.
18940 A value of zero turns off the display.
18941 @item show debug dwarf2-die
18942 Show the current state of DWARF2 DIE debugging.
18943 @item set debug displaced
18944 @cindex displaced stepping debugging info
18945 Turns on or off display of @value{GDBN} debugging info for the
18946 displaced stepping support. The default is off.
18947 @item show debug displaced
18948 Displays the current state of displaying @value{GDBN} debugging info
18949 related to displaced stepping.
18950 @item set debug event
18951 @cindex event debugging info
18952 Turns on or off display of @value{GDBN} event debugging info. The
18954 @item show debug event
18955 Displays the current state of displaying @value{GDBN} event debugging
18957 @item set debug expression
18958 @cindex expression debugging info
18959 Turns on or off display of debugging info about @value{GDBN}
18960 expression parsing. The default is off.
18961 @item show debug expression
18962 Displays the current state of displaying debugging info about
18963 @value{GDBN} expression parsing.
18964 @item set debug frame
18965 @cindex frame debugging info
18966 Turns on or off display of @value{GDBN} frame debugging info. The
18968 @item show debug frame
18969 Displays the current state of displaying @value{GDBN} frame debugging
18971 @item set debug gnu-nat
18972 @cindex @sc{gnu}/Hurd debug messages
18973 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
18974 @item show debug gnu-nat
18975 Show the current state of @sc{gnu}/Hurd debugging messages.
18976 @item set debug infrun
18977 @cindex inferior debugging info
18978 Turns on or off display of @value{GDBN} debugging info for running the inferior.
18979 The default is off. @file{infrun.c} contains GDB's runtime state machine used
18980 for implementing operations such as single-stepping the inferior.
18981 @item show debug infrun
18982 Displays the current state of @value{GDBN} inferior debugging.
18983 @item set debug lin-lwp
18984 @cindex @sc{gnu}/Linux LWP debug messages
18985 @cindex Linux lightweight processes
18986 Turns on or off debugging messages from the Linux LWP debug support.
18987 @item show debug lin-lwp
18988 Show the current state of Linux LWP debugging messages.
18989 @item set debug lin-lwp-async
18990 @cindex @sc{gnu}/Linux LWP async debug messages
18991 @cindex Linux lightweight processes
18992 Turns on or off debugging messages from the Linux LWP async debug support.
18993 @item show debug lin-lwp-async
18994 Show the current state of Linux LWP async debugging messages.
18995 @item set debug observer
18996 @cindex observer debugging info
18997 Turns on or off display of @value{GDBN} observer debugging. This
18998 includes info such as the notification of observable events.
18999 @item show debug observer
19000 Displays the current state of observer debugging.
19001 @item set debug overload
19002 @cindex C@t{++} overload debugging info
19003 Turns on or off display of @value{GDBN} C@t{++} overload debugging
19004 info. This includes info such as ranking of functions, etc. The default
19006 @item show debug overload
19007 Displays the current state of displaying @value{GDBN} C@t{++} overload
19009 @cindex expression parser, debugging info
19010 @cindex debug expression parser
19011 @item set debug parser
19012 Turns on or off the display of expression parser debugging output.
19013 Internally, this sets the @code{yydebug} variable in the expression
19014 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
19015 details. The default is off.
19016 @item show debug parser
19017 Show the current state of expression parser debugging.
19018 @cindex packets, reporting on stdout
19019 @cindex serial connections, debugging
19020 @cindex debug remote protocol
19021 @cindex remote protocol debugging
19022 @cindex display remote packets
19023 @item set debug remote
19024 Turns on or off display of reports on all packets sent back and forth across
19025 the serial line to the remote machine. The info is printed on the
19026 @value{GDBN} standard output stream. The default is off.
19027 @item show debug remote
19028 Displays the state of display of remote packets.
19029 @item set debug serial
19030 Turns on or off display of @value{GDBN} serial debugging info. The
19032 @item show debug serial
19033 Displays the current state of displaying @value{GDBN} serial debugging
19035 @item set debug solib-frv
19036 @cindex FR-V shared-library debugging
19037 Turns on or off debugging messages for FR-V shared-library code.
19038 @item show debug solib-frv
19039 Display the current state of FR-V shared-library code debugging
19041 @item set debug target
19042 @cindex target debugging info
19043 Turns on or off display of @value{GDBN} target debugging info. This info
19044 includes what is going on at the target level of GDB, as it happens. The
19045 default is 0. Set it to 1 to track events, and to 2 to also track the
19046 value of large memory transfers. Changes to this flag do not take effect
19047 until the next time you connect to a target or use the @code{run} command.
19048 @item show debug target
19049 Displays the current state of displaying @value{GDBN} target debugging
19051 @item set debug timestamp
19052 @cindex timestampping debugging info
19053 Turns on or off display of timestamps with @value{GDBN} debugging info.
19054 When enabled, seconds and microseconds are displayed before each debugging
19056 @item show debug timestamp
19057 Displays the current state of displaying timestamps with @value{GDBN}
19059 @item set debugvarobj
19060 @cindex variable object debugging info
19061 Turns on or off display of @value{GDBN} variable object debugging
19062 info. The default is off.
19063 @item show debugvarobj
19064 Displays the current state of displaying @value{GDBN} variable object
19066 @item set debug xml
19067 @cindex XML parser debugging
19068 Turns on or off debugging messages for built-in XML parsers.
19069 @item show debug xml
19070 Displays the current state of XML debugging messages.
19073 @node Other Misc Settings
19074 @section Other Miscellaneous Settings
19075 @cindex miscellaneous settings
19078 @kindex set interactive-mode
19079 @item set interactive-mode
19080 If @code{on}, forces @value{GDBN} to operate interactively.
19081 If @code{off}, forces @value{GDBN} to operate non-interactively,
19082 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
19083 based on whether the debugger was started in a terminal or not.
19085 In the vast majority of cases, the debugger should be able to guess
19086 correctly which mode should be used. But this setting can be useful
19087 in certain specific cases, such as running a MinGW @value{GDBN}
19088 inside a cygwin window.
19090 @kindex show interactive-mode
19091 @item show interactive-mode
19092 Displays whether the debugger is operating in interactive mode or not.
19095 @node Extending GDB
19096 @chapter Extending @value{GDBN}
19097 @cindex extending GDB
19099 @value{GDBN} provides two mechanisms for extension. The first is based
19100 on composition of @value{GDBN} commands, and the second is based on the
19101 Python scripting language.
19103 To facilitate the use of these extensions, @value{GDBN} is capable
19104 of evaluating the contents of a file. When doing so, @value{GDBN}
19105 can recognize which scripting language is being used by looking at
19106 the filename extension. Files with an unrecognized filename extension
19107 are always treated as a @value{GDBN} Command Files.
19108 @xref{Command Files,, Command files}.
19110 You can control how @value{GDBN} evaluates these files with the following
19114 @kindex set script-extension
19115 @kindex show script-extension
19116 @item set script-extension off
19117 All scripts are always evaluated as @value{GDBN} Command Files.
19119 @item set script-extension soft
19120 The debugger determines the scripting language based on filename
19121 extension. If this scripting language is supported, @value{GDBN}
19122 evaluates the script using that language. Otherwise, it evaluates
19123 the file as a @value{GDBN} Command File.
19125 @item set script-extension strict
19126 The debugger determines the scripting language based on filename
19127 extension, and evaluates the script using that language. If the
19128 language is not supported, then the evaluation fails.
19130 @item show script-extension
19131 Display the current value of the @code{script-extension} option.
19136 * Sequences:: Canned Sequences of Commands
19137 * Python:: Scripting @value{GDBN} using Python
19141 @section Canned Sequences of Commands
19143 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
19144 Command Lists}), @value{GDBN} provides two ways to store sequences of
19145 commands for execution as a unit: user-defined commands and command
19149 * Define:: How to define your own commands
19150 * Hooks:: Hooks for user-defined commands
19151 * Command Files:: How to write scripts of commands to be stored in a file
19152 * Output:: Commands for controlled output
19156 @subsection User-defined Commands
19158 @cindex user-defined command
19159 @cindex arguments, to user-defined commands
19160 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
19161 which you assign a new name as a command. This is done with the
19162 @code{define} command. User commands may accept up to 10 arguments
19163 separated by whitespace. Arguments are accessed within the user command
19164 via @code{$arg0@dots{}$arg9}. A trivial example:
19168 print $arg0 + $arg1 + $arg2
19173 To execute the command use:
19180 This defines the command @code{adder}, which prints the sum of
19181 its three arguments. Note the arguments are text substitutions, so they may
19182 reference variables, use complex expressions, or even perform inferior
19185 @cindex argument count in user-defined commands
19186 @cindex how many arguments (user-defined commands)
19187 In addition, @code{$argc} may be used to find out how many arguments have
19188 been passed. This expands to a number in the range 0@dots{}10.
19193 print $arg0 + $arg1
19196 print $arg0 + $arg1 + $arg2
19204 @item define @var{commandname}
19205 Define a command named @var{commandname}. If there is already a command
19206 by that name, you are asked to confirm that you want to redefine it.
19207 @var{commandname} may be a bare command name consisting of letters,
19208 numbers, dashes, and underscores. It may also start with any predefined
19209 prefix command. For example, @samp{define target my-target} creates
19210 a user-defined @samp{target my-target} command.
19212 The definition of the command is made up of other @value{GDBN} command lines,
19213 which are given following the @code{define} command. The end of these
19214 commands is marked by a line containing @code{end}.
19217 @kindex end@r{ (user-defined commands)}
19218 @item document @var{commandname}
19219 Document the user-defined command @var{commandname}, so that it can be
19220 accessed by @code{help}. The command @var{commandname} must already be
19221 defined. This command reads lines of documentation just as @code{define}
19222 reads the lines of the command definition, ending with @code{end}.
19223 After the @code{document} command is finished, @code{help} on command
19224 @var{commandname} displays the documentation you have written.
19226 You may use the @code{document} command again to change the
19227 documentation of a command. Redefining the command with @code{define}
19228 does not change the documentation.
19230 @kindex dont-repeat
19231 @cindex don't repeat command
19233 Used inside a user-defined command, this tells @value{GDBN} that this
19234 command should not be repeated when the user hits @key{RET}
19235 (@pxref{Command Syntax, repeat last command}).
19237 @kindex help user-defined
19238 @item help user-defined
19239 List all user-defined commands, with the first line of the documentation
19244 @itemx show user @var{commandname}
19245 Display the @value{GDBN} commands used to define @var{commandname} (but
19246 not its documentation). If no @var{commandname} is given, display the
19247 definitions for all user-defined commands.
19249 @cindex infinite recursion in user-defined commands
19250 @kindex show max-user-call-depth
19251 @kindex set max-user-call-depth
19252 @item show max-user-call-depth
19253 @itemx set max-user-call-depth
19254 The value of @code{max-user-call-depth} controls how many recursion
19255 levels are allowed in user-defined commands before @value{GDBN} suspects an
19256 infinite recursion and aborts the command.
19259 In addition to the above commands, user-defined commands frequently
19260 use control flow commands, described in @ref{Command Files}.
19262 When user-defined commands are executed, the
19263 commands of the definition are not printed. An error in any command
19264 stops execution of the user-defined command.
19266 If used interactively, commands that would ask for confirmation proceed
19267 without asking when used inside a user-defined command. Many @value{GDBN}
19268 commands that normally print messages to say what they are doing omit the
19269 messages when used in a user-defined command.
19272 @subsection User-defined Command Hooks
19273 @cindex command hooks
19274 @cindex hooks, for commands
19275 @cindex hooks, pre-command
19278 You may define @dfn{hooks}, which are a special kind of user-defined
19279 command. Whenever you run the command @samp{foo}, if the user-defined
19280 command @samp{hook-foo} exists, it is executed (with no arguments)
19281 before that command.
19283 @cindex hooks, post-command
19285 A hook may also be defined which is run after the command you executed.
19286 Whenever you run the command @samp{foo}, if the user-defined command
19287 @samp{hookpost-foo} exists, it is executed (with no arguments) after
19288 that command. Post-execution hooks may exist simultaneously with
19289 pre-execution hooks, for the same command.
19291 It is valid for a hook to call the command which it hooks. If this
19292 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
19294 @c It would be nice if hookpost could be passed a parameter indicating
19295 @c if the command it hooks executed properly or not. FIXME!
19297 @kindex stop@r{, a pseudo-command}
19298 In addition, a pseudo-command, @samp{stop} exists. Defining
19299 (@samp{hook-stop}) makes the associated commands execute every time
19300 execution stops in your program: before breakpoint commands are run,
19301 displays are printed, or the stack frame is printed.
19303 For example, to ignore @code{SIGALRM} signals while
19304 single-stepping, but treat them normally during normal execution,
19309 handle SIGALRM nopass
19313 handle SIGALRM pass
19316 define hook-continue
19317 handle SIGALRM pass
19321 As a further example, to hook at the beginning and end of the @code{echo}
19322 command, and to add extra text to the beginning and end of the message,
19330 define hookpost-echo
19334 (@value{GDBP}) echo Hello World
19335 <<<---Hello World--->>>
19340 You can define a hook for any single-word command in @value{GDBN}, but
19341 not for command aliases; you should define a hook for the basic command
19342 name, e.g.@: @code{backtrace} rather than @code{bt}.
19343 @c FIXME! So how does Joe User discover whether a command is an alias
19345 You can hook a multi-word command by adding @code{hook-} or
19346 @code{hookpost-} to the last word of the command, e.g.@:
19347 @samp{define target hook-remote} to add a hook to @samp{target remote}.
19349 If an error occurs during the execution of your hook, execution of
19350 @value{GDBN} commands stops and @value{GDBN} issues a prompt
19351 (before the command that you actually typed had a chance to run).
19353 If you try to define a hook which does not match any known command, you
19354 get a warning from the @code{define} command.
19356 @node Command Files
19357 @subsection Command Files
19359 @cindex command files
19360 @cindex scripting commands
19361 A command file for @value{GDBN} is a text file made of lines that are
19362 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
19363 also be included. An empty line in a command file does nothing; it
19364 does not mean to repeat the last command, as it would from the
19367 You can request the execution of a command file with the @code{source}
19368 command. Note that the @code{source} command is also used to evaluate
19369 scripts that are not Command Files. The exact behavior can be configured
19370 using the @code{script-extension} setting.
19371 @xref{Extending GDB,, Extending GDB}.
19375 @cindex execute commands from a file
19376 @item source [@code{-v}] @var{filename}
19377 Execute the command file @var{filename}.
19380 The lines in a command file are generally executed sequentially,
19381 unless the order of execution is changed by one of the
19382 @emph{flow-control commands} described below. The commands are not
19383 printed as they are executed. An error in any command terminates
19384 execution of the command file and control is returned to the console.
19386 @value{GDBN} first searches for @var{filename} in the current directory.
19387 If the file is not found there, and @var{filename} does not specify a
19388 directory, then @value{GDBN} also looks for the file on the source search path
19389 (specified with the @samp{directory} command);
19390 except that @file{$cdir} is not searched because the compilation directory
19391 is not relevant to scripts.
19393 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
19394 each command as it is executed. The option must be given before
19395 @var{filename}, and is interpreted as part of the filename anywhere else.
19397 Commands that would ask for confirmation if used interactively proceed
19398 without asking when used in a command file. Many @value{GDBN} commands that
19399 normally print messages to say what they are doing omit the messages
19400 when called from command files.
19402 @value{GDBN} also accepts command input from standard input. In this
19403 mode, normal output goes to standard output and error output goes to
19404 standard error. Errors in a command file supplied on standard input do
19405 not terminate execution of the command file---execution continues with
19409 gdb < cmds > log 2>&1
19412 (The syntax above will vary depending on the shell used.) This example
19413 will execute commands from the file @file{cmds}. All output and errors
19414 would be directed to @file{log}.
19416 Since commands stored on command files tend to be more general than
19417 commands typed interactively, they frequently need to deal with
19418 complicated situations, such as different or unexpected values of
19419 variables and symbols, changes in how the program being debugged is
19420 built, etc. @value{GDBN} provides a set of flow-control commands to
19421 deal with these complexities. Using these commands, you can write
19422 complex scripts that loop over data structures, execute commands
19423 conditionally, etc.
19430 This command allows to include in your script conditionally executed
19431 commands. The @code{if} command takes a single argument, which is an
19432 expression to evaluate. It is followed by a series of commands that
19433 are executed only if the expression is true (its value is nonzero).
19434 There can then optionally be an @code{else} line, followed by a series
19435 of commands that are only executed if the expression was false. The
19436 end of the list is marked by a line containing @code{end}.
19440 This command allows to write loops. Its syntax is similar to
19441 @code{if}: the command takes a single argument, which is an expression
19442 to evaluate, and must be followed by the commands to execute, one per
19443 line, terminated by an @code{end}. These commands are called the
19444 @dfn{body} of the loop. The commands in the body of @code{while} are
19445 executed repeatedly as long as the expression evaluates to true.
19449 This command exits the @code{while} loop in whose body it is included.
19450 Execution of the script continues after that @code{while}s @code{end}
19453 @kindex loop_continue
19454 @item loop_continue
19455 This command skips the execution of the rest of the body of commands
19456 in the @code{while} loop in whose body it is included. Execution
19457 branches to the beginning of the @code{while} loop, where it evaluates
19458 the controlling expression.
19460 @kindex end@r{ (if/else/while commands)}
19462 Terminate the block of commands that are the body of @code{if},
19463 @code{else}, or @code{while} flow-control commands.
19468 @subsection Commands for Controlled Output
19470 During the execution of a command file or a user-defined command, normal
19471 @value{GDBN} output is suppressed; the only output that appears is what is
19472 explicitly printed by the commands in the definition. This section
19473 describes three commands useful for generating exactly the output you
19478 @item echo @var{text}
19479 @c I do not consider backslash-space a standard C escape sequence
19480 @c because it is not in ANSI.
19481 Print @var{text}. Nonprinting characters can be included in
19482 @var{text} using C escape sequences, such as @samp{\n} to print a
19483 newline. @strong{No newline is printed unless you specify one.}
19484 In addition to the standard C escape sequences, a backslash followed
19485 by a space stands for a space. This is useful for displaying a
19486 string with spaces at the beginning or the end, since leading and
19487 trailing spaces are otherwise trimmed from all arguments.
19488 To print @samp{@w{ }and foo =@w{ }}, use the command
19489 @samp{echo \@w{ }and foo = \@w{ }}.
19491 A backslash at the end of @var{text} can be used, as in C, to continue
19492 the command onto subsequent lines. For example,
19495 echo This is some text\n\
19496 which is continued\n\
19497 onto several lines.\n
19500 produces the same output as
19503 echo This is some text\n
19504 echo which is continued\n
19505 echo onto several lines.\n
19509 @item output @var{expression}
19510 Print the value of @var{expression} and nothing but that value: no
19511 newlines, no @samp{$@var{nn} = }. The value is not entered in the
19512 value history either. @xref{Expressions, ,Expressions}, for more information
19515 @item output/@var{fmt} @var{expression}
19516 Print the value of @var{expression} in format @var{fmt}. You can use
19517 the same formats as for @code{print}. @xref{Output Formats,,Output
19518 Formats}, for more information.
19521 @item printf @var{template}, @var{expressions}@dots{}
19522 Print the values of one or more @var{expressions} under the control of
19523 the string @var{template}. To print several values, make
19524 @var{expressions} be a comma-separated list of individual expressions,
19525 which may be either numbers or pointers. Their values are printed as
19526 specified by @var{template}, exactly as a C program would do by
19527 executing the code below:
19530 printf (@var{template}, @var{expressions}@dots{});
19533 As in @code{C} @code{printf}, ordinary characters in @var{template}
19534 are printed verbatim, while @dfn{conversion specification} introduced
19535 by the @samp{%} character cause subsequent @var{expressions} to be
19536 evaluated, their values converted and formatted according to type and
19537 style information encoded in the conversion specifications, and then
19540 For example, you can print two values in hex like this:
19543 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
19546 @code{printf} supports all the standard @code{C} conversion
19547 specifications, including the flags and modifiers between the @samp{%}
19548 character and the conversion letter, with the following exceptions:
19552 The argument-ordering modifiers, such as @samp{2$}, are not supported.
19555 The modifier @samp{*} is not supported for specifying precision or
19559 The @samp{'} flag (for separation of digits into groups according to
19560 @code{LC_NUMERIC'}) is not supported.
19563 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
19567 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
19570 The conversion letters @samp{a} and @samp{A} are not supported.
19574 Note that the @samp{ll} type modifier is supported only if the
19575 underlying @code{C} implementation used to build @value{GDBN} supports
19576 the @code{long long int} type, and the @samp{L} type modifier is
19577 supported only if @code{long double} type is available.
19579 As in @code{C}, @code{printf} supports simple backslash-escape
19580 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
19581 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
19582 single character. Octal and hexadecimal escape sequences are not
19585 Additionally, @code{printf} supports conversion specifications for DFP
19586 (@dfn{Decimal Floating Point}) types using the following length modifiers
19587 together with a floating point specifier.
19592 @samp{H} for printing @code{Decimal32} types.
19595 @samp{D} for printing @code{Decimal64} types.
19598 @samp{DD} for printing @code{Decimal128} types.
19601 If the underlying @code{C} implementation used to build @value{GDBN} has
19602 support for the three length modifiers for DFP types, other modifiers
19603 such as width and precision will also be available for @value{GDBN} to use.
19605 In case there is no such @code{C} support, no additional modifiers will be
19606 available and the value will be printed in the standard way.
19608 Here's an example of printing DFP types using the above conversion letters:
19610 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
19616 @section Scripting @value{GDBN} using Python
19617 @cindex python scripting
19618 @cindex scripting with python
19620 You can script @value{GDBN} using the @uref{http://www.python.org/,
19621 Python programming language}. This feature is available only if
19622 @value{GDBN} was configured using @option{--with-python}.
19625 * Python Commands:: Accessing Python from @value{GDBN}.
19626 * Python API:: Accessing @value{GDBN} from Python.
19629 @node Python Commands
19630 @subsection Python Commands
19631 @cindex python commands
19632 @cindex commands to access python
19634 @value{GDBN} provides one command for accessing the Python interpreter,
19635 and one related setting:
19639 @item python @r{[}@var{code}@r{]}
19640 The @code{python} command can be used to evaluate Python code.
19642 If given an argument, the @code{python} command will evaluate the
19643 argument as a Python command. For example:
19646 (@value{GDBP}) python print 23
19650 If you do not provide an argument to @code{python}, it will act as a
19651 multi-line command, like @code{define}. In this case, the Python
19652 script is made up of subsequent command lines, given after the
19653 @code{python} command. This command list is terminated using a line
19654 containing @code{end}. For example:
19657 (@value{GDBP}) python
19659 End with a line saying just "end".
19665 @kindex maint set python print-stack
19666 @item maint set python print-stack
19667 By default, @value{GDBN} will print a stack trace when an error occurs
19668 in a Python script. This can be controlled using @code{maint set
19669 python print-stack}: if @code{on}, the default, then Python stack
19670 printing is enabled; if @code{off}, then Python stack printing is
19674 It is also possible to execute a Python script from the @value{GDBN}
19678 @item source @file{script-name}
19679 The script name must end with @samp{.py} and @value{GDBN} must be configured
19680 to recognize the script language based on filename extension using
19681 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
19683 @item python execfile ("script-name")
19684 This method is based on the @code{execfile} Python built-in function,
19685 and thus is always available.
19689 @subsection Python API
19691 @cindex programming in python
19693 @cindex python stdout
19694 @cindex python pagination
19695 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
19696 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
19697 A Python program which outputs to one of these streams may have its
19698 output interrupted by the user (@pxref{Screen Size}). In this
19699 situation, a Python @code{KeyboardInterrupt} exception is thrown.
19702 * Basic Python:: Basic Python Functions.
19703 * Exception Handling::
19704 * Auto-loading:: Automatically loading Python code.
19705 * Values From Inferior::
19706 * Types In Python:: Python representation of types.
19707 * Pretty Printing:: Pretty-printing values.
19708 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
19709 * Commands In Python:: Implementing new commands in Python.
19710 * Functions In Python:: Writing new convenience functions.
19711 * Objfiles In Python:: Object files.
19712 * Frames In Python:: Accessing inferior stack frames from Python.
19713 * Blocks In Python:: Accessing frame blocks from Python.
19714 * Symbols In Python:: Python representation of symbols.
19715 * Symbol Tables In Python:: Python representation of symbol tables.
19716 * Lazy Strings In Python:: Python representation of lazy strings.
19720 @subsubsection Basic Python
19722 @cindex python functions
19723 @cindex python module
19725 @value{GDBN} introduces a new Python module, named @code{gdb}. All
19726 methods and classes added by @value{GDBN} are placed in this module.
19727 @value{GDBN} automatically @code{import}s the @code{gdb} module for
19728 use in all scripts evaluated by the @code{python} command.
19730 @findex gdb.execute
19731 @defun execute command [from_tty]
19732 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
19733 If a GDB exception happens while @var{command} runs, it is
19734 translated as described in @ref{Exception Handling,,Exception Handling}.
19735 If no exceptions occur, this function returns @code{None}.
19737 @var{from_tty} specifies whether @value{GDBN} ought to consider this
19738 command as having originated from the user invoking it interactively.
19739 It must be a boolean value. If omitted, it defaults to @code{False}.
19742 @findex gdb.parameter
19743 @defun parameter parameter
19744 Return the value of a @value{GDBN} parameter. @var{parameter} is a
19745 string naming the parameter to look up; @var{parameter} may contain
19746 spaces if the parameter has a multi-part name. For example,
19747 @samp{print object} is a valid parameter name.
19749 If the named parameter does not exist, this function throws a
19750 @code{RuntimeError}. Otherwise, the parameter's value is converted to
19751 a Python value of the appropriate type, and returned.
19754 @findex gdb.history
19755 @defun history number
19756 Return a value from @value{GDBN}'s value history (@pxref{Value
19757 History}). @var{number} indicates which history element to return.
19758 If @var{number} is negative, then @value{GDBN} will take its absolute value
19759 and count backward from the last element (i.e., the most recent element) to
19760 find the value to return. If @var{number} is zero, then @value{GDBN} will
19761 return the most recent element. If the element specified by @var{number}
19762 doesn't exist in the value history, a @code{RuntimeError} exception will be
19765 If no exception is raised, the return value is always an instance of
19766 @code{gdb.Value} (@pxref{Values From Inferior}).
19769 @findex gdb.parse_and_eval
19770 @defun parse_and_eval expression
19771 Parse @var{expression} as an expression in the current language,
19772 evaluate it, and return the result as a @code{gdb.Value}.
19773 @var{expression} must be a string.
19775 This function can be useful when implementing a new command
19776 (@pxref{Commands In Python}), as it provides a way to parse the
19777 command's argument as an expression. It is also useful simply to
19778 compute values, for example, it is the only way to get the value of a
19779 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
19783 @defun write string
19784 Print a string to @value{GDBN}'s paginated standard output stream.
19785 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
19786 call this function.
19791 Flush @value{GDBN}'s paginated standard output stream. Flushing
19792 @code{sys.stdout} or @code{sys.stderr} will automatically call this
19796 @findex gdb.target_charset
19797 @defun target_charset
19798 Return the name of the current target character set (@pxref{Character
19799 Sets}). This differs from @code{gdb.parameter('target-charset')} in
19800 that @samp{auto} is never returned.
19803 @findex gdb.target_wide_charset
19804 @defun target_wide_charset
19805 Return the name of the current target wide character set
19806 (@pxref{Character Sets}). This differs from
19807 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
19811 @node Exception Handling
19812 @subsubsection Exception Handling
19813 @cindex python exceptions
19814 @cindex exceptions, python
19816 When executing the @code{python} command, Python exceptions
19817 uncaught within the Python code are translated to calls to
19818 @value{GDBN} error-reporting mechanism. If the command that called
19819 @code{python} does not handle the error, @value{GDBN} will
19820 terminate it and print an error message containing the Python
19821 exception name, the associated value, and the Python call stack
19822 backtrace at the point where the exception was raised. Example:
19825 (@value{GDBP}) python print foo
19826 Traceback (most recent call last):
19827 File "<string>", line 1, in <module>
19828 NameError: name 'foo' is not defined
19831 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
19832 code are converted to Python @code{RuntimeError} exceptions. User
19833 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
19834 prompt) is translated to a Python @code{KeyboardInterrupt}
19835 exception. If you catch these exceptions in your Python code, your
19836 exception handler will see @code{RuntimeError} or
19837 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
19838 message as its value, and the Python call stack backtrace at the
19839 Python statement closest to where the @value{GDBN} error occured as the
19843 @subsubsection Auto-loading
19844 @cindex auto-loading, Python
19846 When a new object file is read (for example, due to the @code{file}
19847 command, or because the inferior has loaded a shared library),
19848 @value{GDBN} will look for a file named @file{@var{objfile}-gdb.py},
19849 where @var{objfile} is the object file's real name, formed by ensuring
19850 that the file name is absolute, following all symlinks, and resolving
19851 @code{.} and @code{..} components. If this file exists and is
19852 readable, @value{GDBN} will evaluate it as a Python script.
19854 If this file does not exist, and if the parameter
19855 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
19856 then @value{GDBN} will use for its each separated directory component
19857 @code{component} the file named @file{@code{component}/@var{real-name}}, where
19858 @var{real-name} is the object file's real name, as described above.
19860 Finally, if this file does not exist, then @value{GDBN} will look for
19861 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
19862 @var{data-directory} is @value{GDBN}'s data directory (available via
19863 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
19864 is the object file's real name, as described above.
19866 When reading an auto-loaded file, @value{GDBN} sets the ``current
19867 objfile''. This is available via the @code{gdb.current_objfile}
19868 function (@pxref{Objfiles In Python}). This can be useful for
19869 registering objfile-specific pretty-printers.
19871 The auto-loading feature is useful for supplying application-specific
19872 debugging commands and scripts. You can enable or disable this
19873 feature, and view its current state.
19876 @kindex maint set python auto-load
19877 @item maint set python auto-load [yes|no]
19878 Enable or disable the Python auto-loading feature.
19880 @kindex maint show python auto-load
19881 @item maint show python auto-load
19882 Show whether Python auto-loading is enabled or disabled.
19885 @value{GDBN} does not track which files it has already auto-loaded.
19886 So, your @samp{-gdb.py} file should take care to ensure that it may be
19887 evaluated multiple times without error.
19889 @node Values From Inferior
19890 @subsubsection Values From Inferior
19891 @cindex values from inferior, with Python
19892 @cindex python, working with values from inferior
19894 @cindex @code{gdb.Value}
19895 @value{GDBN} provides values it obtains from the inferior program in
19896 an object of type @code{gdb.Value}. @value{GDBN} uses this object
19897 for its internal bookkeeping of the inferior's values, and for
19898 fetching values when necessary.
19900 Inferior values that are simple scalars can be used directly in
19901 Python expressions that are valid for the value's data type. Here's
19902 an example for an integer or floating-point value @code{some_val}:
19909 As result of this, @code{bar} will also be a @code{gdb.Value} object
19910 whose values are of the same type as those of @code{some_val}.
19912 Inferior values that are structures or instances of some class can
19913 be accessed using the Python @dfn{dictionary syntax}. For example, if
19914 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
19915 can access its @code{foo} element with:
19918 bar = some_val['foo']
19921 Again, @code{bar} will also be a @code{gdb.Value} object.
19923 The following attributes are provided:
19926 @defivar Value address
19927 If this object is addressable, this read-only attribute holds a
19928 @code{gdb.Value} object representing the address. Otherwise,
19929 this attribute holds @code{None}.
19932 @cindex optimized out value in Python
19933 @defivar Value is_optimized_out
19934 This read-only boolean attribute is true if the compiler optimized out
19935 this value, thus it is not available for fetching from the inferior.
19938 @defivar Value type
19939 The type of this @code{gdb.Value}. The value of this attribute is a
19940 @code{gdb.Type} object.
19944 The following methods are provided:
19947 @defmethod Value cast type
19948 Return a new instance of @code{gdb.Value} that is the result of
19949 casting this instance to the type described by @var{type}, which must
19950 be a @code{gdb.Type} object. If the cast cannot be performed for some
19951 reason, this method throws an exception.
19954 @defmethod Value dereference
19955 For pointer data types, this method returns a new @code{gdb.Value} object
19956 whose contents is the object pointed to by the pointer. For example, if
19957 @code{foo} is a C pointer to an @code{int}, declared in your C program as
19964 then you can use the corresponding @code{gdb.Value} to access what
19965 @code{foo} points to like this:
19968 bar = foo.dereference ()
19971 The result @code{bar} will be a @code{gdb.Value} object holding the
19972 value pointed to by @code{foo}.
19975 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
19976 If this @code{gdb.Value} represents a string, then this method
19977 converts the contents to a Python string. Otherwise, this method will
19978 throw an exception.
19980 Strings are recognized in a language-specific way; whether a given
19981 @code{gdb.Value} represents a string is determined by the current
19984 For C-like languages, a value is a string if it is a pointer to or an
19985 array of characters or ints. The string is assumed to be terminated
19986 by a zero of the appropriate width. However if the optional length
19987 argument is given, the string will be converted to that given length,
19988 ignoring any embedded zeros that the string may contain.
19990 If the optional @var{encoding} argument is given, it must be a string
19991 naming the encoding of the string in the @code{gdb.Value}, such as
19992 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
19993 the same encodings as the corresponding argument to Python's
19994 @code{string.decode} method, and the Python codec machinery will be used
19995 to convert the string. If @var{encoding} is not given, or if
19996 @var{encoding} is the empty string, then either the @code{target-charset}
19997 (@pxref{Character Sets}) will be used, or a language-specific encoding
19998 will be used, if the current language is able to supply one.
20000 The optional @var{errors} argument is the same as the corresponding
20001 argument to Python's @code{string.decode} method.
20003 If the optional @var{length} argument is given, the string will be
20004 fetched and converted to the given length.
20007 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
20008 If this @code{gdb.Value} represents a string, then this method
20009 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
20010 In Python}). Otherwise, this method will throw an exception.
20012 If the optional @var{encoding} argument is given, it must be a string
20013 naming the encoding of the @code{gdb.LazyString}. Some examples are:
20014 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
20015 @var{encoding} argument is an encoding that @value{GDBN} does
20016 recognize, @value{GDBN} will raise an error.
20018 When a lazy string is printed, the @value{GDBN} encoding machinery is
20019 used to convert the string during printing. If the optional
20020 @var{encoding} argument is not provided, or is an empty string,
20021 @value{GDBN} will automatically select the encoding most suitable for
20022 the string type. For further information on encoding in @value{GDBN}
20023 please see @ref{Character Sets}.
20025 If the optional @var{length} argument is given, the string will be
20026 fetched and encoded to the length of characters specified. If
20027 the @var{length} argument is not provided, the string will be fetched
20028 and encoded until a null of appropriate width is found.
20032 @node Types In Python
20033 @subsubsection Types In Python
20034 @cindex types in Python
20035 @cindex Python, working with types
20038 @value{GDBN} represents types from the inferior using the class
20041 The following type-related functions are available in the @code{gdb}
20044 @findex gdb.lookup_type
20045 @defun lookup_type name [block]
20046 This function looks up a type by name. @var{name} is the name of the
20047 type to look up. It must be a string.
20049 If @var{block} is given, then @var{name} is looked up in that scope.
20050 Otherwise, it is searched for globally.
20052 Ordinarily, this function will return an instance of @code{gdb.Type}.
20053 If the named type cannot be found, it will throw an exception.
20056 An instance of @code{Type} has the following attributes:
20060 The type code for this type. The type code will be one of the
20061 @code{TYPE_CODE_} constants defined below.
20064 @defivar Type sizeof
20065 The size of this type, in target @code{char} units. Usually, a
20066 target's @code{char} type will be an 8-bit byte. However, on some
20067 unusual platforms, this type may have a different size.
20071 The tag name for this type. The tag name is the name after
20072 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
20073 languages have this concept. If this type has no tag name, then
20074 @code{None} is returned.
20078 The following methods are provided:
20081 @defmethod Type fields
20082 For structure and union types, this method returns the fields. Range
20083 types have two fields, the minimum and maximum values. Enum types
20084 have one field per enum constant. Function and method types have one
20085 field per parameter. The base types of C@t{++} classes are also
20086 represented as fields. If the type has no fields, or does not fit
20087 into one of these categories, an empty sequence will be returned.
20089 Each field is an object, with some pre-defined attributes:
20092 This attribute is not available for @code{static} fields (as in
20093 C@t{++} or Java). For non-@code{static} fields, the value is the bit
20094 position of the field.
20097 The name of the field, or @code{None} for anonymous fields.
20100 This is @code{True} if the field is artificial, usually meaning that
20101 it was provided by the compiler and not the user. This attribute is
20102 always provided, and is @code{False} if the field is not artificial.
20104 @item is_base_class
20105 This is @code{True} if the field represents a base class of a C@t{++}
20106 structure. This attribute is always provided, and is @code{False}
20107 if the field is not a base class of the type that is the argument of
20108 @code{fields}, or if that type was not a C@t{++} class.
20111 If the field is packed, or is a bitfield, then this will have a
20112 non-zero value, which is the size of the field in bits. Otherwise,
20113 this will be zero; in this case the field's size is given by its type.
20116 The type of the field. This is usually an instance of @code{Type},
20117 but it can be @code{None} in some situations.
20121 @defmethod Type const
20122 Return a new @code{gdb.Type} object which represents a
20123 @code{const}-qualified variant of this type.
20126 @defmethod Type volatile
20127 Return a new @code{gdb.Type} object which represents a
20128 @code{volatile}-qualified variant of this type.
20131 @defmethod Type unqualified
20132 Return a new @code{gdb.Type} object which represents an unqualified
20133 variant of this type. That is, the result is neither @code{const} nor
20137 @defmethod Type range
20138 Return a Python @code{Tuple} object that contains two elements: the
20139 low bound of the argument type and the high bound of that type. If
20140 the type does not have a range, @value{GDBN} will raise a
20141 @code{RuntimeError} exception.
20144 @defmethod Type reference
20145 Return a new @code{gdb.Type} object which represents a reference to this
20149 @defmethod Type pointer
20150 Return a new @code{gdb.Type} object which represents a pointer to this
20154 @defmethod Type strip_typedefs
20155 Return a new @code{gdb.Type} that represents the real type,
20156 after removing all layers of typedefs.
20159 @defmethod Type target
20160 Return a new @code{gdb.Type} object which represents the target type
20163 For a pointer type, the target type is the type of the pointed-to
20164 object. For an array type (meaning C-like arrays), the target type is
20165 the type of the elements of the array. For a function or method type,
20166 the target type is the type of the return value. For a complex type,
20167 the target type is the type of the elements. For a typedef, the
20168 target type is the aliased type.
20170 If the type does not have a target, this method will throw an
20174 @defmethod Type template_argument n [block]
20175 If this @code{gdb.Type} is an instantiation of a template, this will
20176 return a new @code{gdb.Type} which represents the type of the
20177 @var{n}th template argument.
20179 If this @code{gdb.Type} is not a template type, this will throw an
20180 exception. Ordinarily, only C@t{++} code will have template types.
20182 If @var{block} is given, then @var{name} is looked up in that scope.
20183 Otherwise, it is searched for globally.
20188 Each type has a code, which indicates what category this type falls
20189 into. The available type categories are represented by constants
20190 defined in the @code{gdb} module:
20193 @findex TYPE_CODE_PTR
20194 @findex gdb.TYPE_CODE_PTR
20195 @item TYPE_CODE_PTR
20196 The type is a pointer.
20198 @findex TYPE_CODE_ARRAY
20199 @findex gdb.TYPE_CODE_ARRAY
20200 @item TYPE_CODE_ARRAY
20201 The type is an array.
20203 @findex TYPE_CODE_STRUCT
20204 @findex gdb.TYPE_CODE_STRUCT
20205 @item TYPE_CODE_STRUCT
20206 The type is a structure.
20208 @findex TYPE_CODE_UNION
20209 @findex gdb.TYPE_CODE_UNION
20210 @item TYPE_CODE_UNION
20211 The type is a union.
20213 @findex TYPE_CODE_ENUM
20214 @findex gdb.TYPE_CODE_ENUM
20215 @item TYPE_CODE_ENUM
20216 The type is an enum.
20218 @findex TYPE_CODE_FLAGS
20219 @findex gdb.TYPE_CODE_FLAGS
20220 @item TYPE_CODE_FLAGS
20221 A bit flags type, used for things such as status registers.
20223 @findex TYPE_CODE_FUNC
20224 @findex gdb.TYPE_CODE_FUNC
20225 @item TYPE_CODE_FUNC
20226 The type is a function.
20228 @findex TYPE_CODE_INT
20229 @findex gdb.TYPE_CODE_INT
20230 @item TYPE_CODE_INT
20231 The type is an integer type.
20233 @findex TYPE_CODE_FLT
20234 @findex gdb.TYPE_CODE_FLT
20235 @item TYPE_CODE_FLT
20236 A floating point type.
20238 @findex TYPE_CODE_VOID
20239 @findex gdb.TYPE_CODE_VOID
20240 @item TYPE_CODE_VOID
20241 The special type @code{void}.
20243 @findex TYPE_CODE_SET
20244 @findex gdb.TYPE_CODE_SET
20245 @item TYPE_CODE_SET
20248 @findex TYPE_CODE_RANGE
20249 @findex gdb.TYPE_CODE_RANGE
20250 @item TYPE_CODE_RANGE
20251 A range type, that is, an integer type with bounds.
20253 @findex TYPE_CODE_STRING
20254 @findex gdb.TYPE_CODE_STRING
20255 @item TYPE_CODE_STRING
20256 A string type. Note that this is only used for certain languages with
20257 language-defined string types; C strings are not represented this way.
20259 @findex TYPE_CODE_BITSTRING
20260 @findex gdb.TYPE_CODE_BITSTRING
20261 @item TYPE_CODE_BITSTRING
20264 @findex TYPE_CODE_ERROR
20265 @findex gdb.TYPE_CODE_ERROR
20266 @item TYPE_CODE_ERROR
20267 An unknown or erroneous type.
20269 @findex TYPE_CODE_METHOD
20270 @findex gdb.TYPE_CODE_METHOD
20271 @item TYPE_CODE_METHOD
20272 A method type, as found in C@t{++} or Java.
20274 @findex TYPE_CODE_METHODPTR
20275 @findex gdb.TYPE_CODE_METHODPTR
20276 @item TYPE_CODE_METHODPTR
20277 A pointer-to-member-function.
20279 @findex TYPE_CODE_MEMBERPTR
20280 @findex gdb.TYPE_CODE_MEMBERPTR
20281 @item TYPE_CODE_MEMBERPTR
20282 A pointer-to-member.
20284 @findex TYPE_CODE_REF
20285 @findex gdb.TYPE_CODE_REF
20286 @item TYPE_CODE_REF
20289 @findex TYPE_CODE_CHAR
20290 @findex gdb.TYPE_CODE_CHAR
20291 @item TYPE_CODE_CHAR
20294 @findex TYPE_CODE_BOOL
20295 @findex gdb.TYPE_CODE_BOOL
20296 @item TYPE_CODE_BOOL
20299 @findex TYPE_CODE_COMPLEX
20300 @findex gdb.TYPE_CODE_COMPLEX
20301 @item TYPE_CODE_COMPLEX
20302 A complex float type.
20304 @findex TYPE_CODE_TYPEDEF
20305 @findex gdb.TYPE_CODE_TYPEDEF
20306 @item TYPE_CODE_TYPEDEF
20307 A typedef to some other type.
20309 @findex TYPE_CODE_NAMESPACE
20310 @findex gdb.TYPE_CODE_NAMESPACE
20311 @item TYPE_CODE_NAMESPACE
20312 A C@t{++} namespace.
20314 @findex TYPE_CODE_DECFLOAT
20315 @findex gdb.TYPE_CODE_DECFLOAT
20316 @item TYPE_CODE_DECFLOAT
20317 A decimal floating point type.
20319 @findex TYPE_CODE_INTERNAL_FUNCTION
20320 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
20321 @item TYPE_CODE_INTERNAL_FUNCTION
20322 A function internal to @value{GDBN}. This is the type used to represent
20323 convenience functions.
20326 @node Pretty Printing
20327 @subsubsection Pretty Printing
20329 @value{GDBN} provides a mechanism to allow pretty-printing of values
20330 using Python code. The pretty-printer API allows application-specific
20331 code to greatly simplify the display of complex objects. This
20332 mechanism works for both MI and the CLI.
20334 For example, here is how a C@t{++} @code{std::string} looks without a
20338 (@value{GDBP}) print s
20340 static npos = 4294967295,
20342 <std::allocator<char>> = @{
20343 <__gnu_cxx::new_allocator<char>> = @{<No data fields>@}, <No data fields>@},
20344 members of std::basic_string<char, std::char_traits<char>, std::allocator<char> >::_Alloc_hider:
20345 _M_p = 0x804a014 "abcd"
20350 After a pretty-printer for @code{std::string} has been installed, only
20351 the contents are printed:
20354 (@value{GDBP}) print s
20358 A pretty-printer is just an object that holds a value and implements a
20359 specific interface, defined here.
20361 @defop Operation {pretty printer} children (self)
20362 @value{GDBN} will call this method on a pretty-printer to compute the
20363 children of the pretty-printer's value.
20365 This method must return an object conforming to the Python iterator
20366 protocol. Each item returned by the iterator must be a tuple holding
20367 two elements. The first element is the ``name'' of the child; the
20368 second element is the child's value. The value can be any Python
20369 object which is convertible to a @value{GDBN} value.
20371 This method is optional. If it does not exist, @value{GDBN} will act
20372 as though the value has no children.
20375 @defop Operation {pretty printer} display_hint (self)
20376 The CLI may call this method and use its result to change the
20377 formatting of a value. The result will also be supplied to an MI
20378 consumer as a @samp{displayhint} attribute of the variable being
20381 This method is optional. If it does exist, this method must return a
20384 Some display hints are predefined by @value{GDBN}:
20388 Indicate that the object being printed is ``array-like''. The CLI
20389 uses this to respect parameters such as @code{set print elements} and
20390 @code{set print array}.
20393 Indicate that the object being printed is ``map-like'', and that the
20394 children of this value can be assumed to alternate between keys and
20398 Indicate that the object being printed is ``string-like''. If the
20399 printer's @code{to_string} method returns a Python string of some
20400 kind, then @value{GDBN} will call its internal language-specific
20401 string-printing function to format the string. For the CLI this means
20402 adding quotation marks, possibly escaping some characters, respecting
20403 @code{set print elements}, and the like.
20407 @defop Operation {pretty printer} to_string (self)
20408 @value{GDBN} will call this method to display the string
20409 representation of the value passed to the object's constructor.
20411 When printing from the CLI, if the @code{to_string} method exists,
20412 then @value{GDBN} will prepend its result to the values returned by
20413 @code{children}. Exactly how this formatting is done is dependent on
20414 the display hint, and may change as more hints are added. Also,
20415 depending on the print settings (@pxref{Print Settings}), the CLI may
20416 print just the result of @code{to_string} in a stack trace, omitting
20417 the result of @code{children}.
20419 If this method returns a string, it is printed verbatim.
20421 Otherwise, if this method returns an instance of @code{gdb.Value},
20422 then @value{GDBN} prints this value. This may result in a call to
20423 another pretty-printer.
20425 If instead the method returns a Python value which is convertible to a
20426 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
20427 the resulting value. Again, this may result in a call to another
20428 pretty-printer. Python scalars (integers, floats, and booleans) and
20429 strings are convertible to @code{gdb.Value}; other types are not.
20431 If the result is not one of these types, an exception is raised.
20434 @node Selecting Pretty-Printers
20435 @subsubsection Selecting Pretty-Printers
20437 The Python list @code{gdb.pretty_printers} contains an array of
20438 functions that have been registered via addition as a pretty-printer.
20439 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
20442 A function on one of these lists is passed a single @code{gdb.Value}
20443 argument and should return a pretty-printer object conforming to the
20444 interface definition above (@pxref{Pretty Printing}). If a function
20445 cannot create a pretty-printer for the value, it should return
20448 @value{GDBN} first checks the @code{pretty_printers} attribute of each
20449 @code{gdb.Objfile} and iteratively calls each function in the list for
20450 that @code{gdb.Objfile} until it receives a pretty-printer object.
20451 After these lists have been exhausted, it tries the global
20452 @code{gdb.pretty-printers} list, again calling each function until an
20453 object is returned.
20455 The order in which the objfiles are searched is not specified. For a
20456 given list, functions are always invoked from the head of the list,
20457 and iterated over sequentially until the end of the list, or a printer
20458 object is returned.
20460 Here is an example showing how a @code{std::string} printer might be
20464 class StdStringPrinter:
20465 "Print a std::string"
20467 def __init__ (self, val):
20470 def to_string (self):
20471 return self.val['_M_dataplus']['_M_p']
20473 def display_hint (self):
20477 And here is an example showing how a lookup function for the printer
20478 example above might be written.
20481 def str_lookup_function (val):
20483 lookup_tag = val.type.tag
20484 regex = re.compile ("^std::basic_string<char,.*>$")
20485 if lookup_tag == None:
20487 if regex.match (lookup_tag):
20488 return StdStringPrinter (val)
20493 The example lookup function extracts the value's type, and attempts to
20494 match it to a type that it can pretty-print. If it is a type the
20495 printer can pretty-print, it will return a printer object. If not, it
20496 returns @code{None}.
20498 We recommend that you put your core pretty-printers into a Python
20499 package. If your pretty-printers are for use with a library, we
20500 further recommend embedding a version number into the package name.
20501 This practice will enable @value{GDBN} to load multiple versions of
20502 your pretty-printers at the same time, because they will have
20505 You should write auto-loaded code (@pxref{Auto-loading}) such that it
20506 can be evaluated multiple times without changing its meaning. An
20507 ideal auto-load file will consist solely of @code{import}s of your
20508 printer modules, followed by a call to a register pretty-printers with
20509 the current objfile.
20511 Taken as a whole, this approach will scale nicely to multiple
20512 inferiors, each potentially using a different library version.
20513 Embedding a version number in the Python package name will ensure that
20514 @value{GDBN} is able to load both sets of printers simultaneously.
20515 Then, because the search for pretty-printers is done by objfile, and
20516 because your auto-loaded code took care to register your library's
20517 printers with a specific objfile, @value{GDBN} will find the correct
20518 printers for the specific version of the library used by each
20521 To continue the @code{std::string} example (@pxref{Pretty Printing}),
20522 this code might appear in @code{gdb.libstdcxx.v6}:
20525 def register_printers (objfile):
20526 objfile.pretty_printers.add (str_lookup_function)
20530 And then the corresponding contents of the auto-load file would be:
20533 import gdb.libstdcxx.v6
20534 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
20537 @node Commands In Python
20538 @subsubsection Commands In Python
20540 @cindex commands in python
20541 @cindex python commands
20542 You can implement new @value{GDBN} CLI commands in Python. A CLI
20543 command is implemented using an instance of the @code{gdb.Command}
20544 class, most commonly using a subclass.
20546 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
20547 The object initializer for @code{Command} registers the new command
20548 with @value{GDBN}. This initializer is normally invoked from the
20549 subclass' own @code{__init__} method.
20551 @var{name} is the name of the command. If @var{name} consists of
20552 multiple words, then the initial words are looked for as prefix
20553 commands. In this case, if one of the prefix commands does not exist,
20554 an exception is raised.
20556 There is no support for multi-line commands.
20558 @var{command_class} should be one of the @samp{COMMAND_} constants
20559 defined below. This argument tells @value{GDBN} how to categorize the
20560 new command in the help system.
20562 @var{completer_class} is an optional argument. If given, it should be
20563 one of the @samp{COMPLETE_} constants defined below. This argument
20564 tells @value{GDBN} how to perform completion for this command. If not
20565 given, @value{GDBN} will attempt to complete using the object's
20566 @code{complete} method (see below); if no such method is found, an
20567 error will occur when completion is attempted.
20569 @var{prefix} is an optional argument. If @code{True}, then the new
20570 command is a prefix command; sub-commands of this command may be
20573 The help text for the new command is taken from the Python
20574 documentation string for the command's class, if there is one. If no
20575 documentation string is provided, the default value ``This command is
20576 not documented.'' is used.
20579 @cindex don't repeat Python command
20580 @defmethod Command dont_repeat
20581 By default, a @value{GDBN} command is repeated when the user enters a
20582 blank line at the command prompt. A command can suppress this
20583 behavior by invoking the @code{dont_repeat} method. This is similar
20584 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
20587 @defmethod Command invoke argument from_tty
20588 This method is called by @value{GDBN} when this command is invoked.
20590 @var{argument} is a string. It is the argument to the command, after
20591 leading and trailing whitespace has been stripped.
20593 @var{from_tty} is a boolean argument. When true, this means that the
20594 command was entered by the user at the terminal; when false it means
20595 that the command came from elsewhere.
20597 If this method throws an exception, it is turned into a @value{GDBN}
20598 @code{error} call. Otherwise, the return value is ignored.
20601 @cindex completion of Python commands
20602 @defmethod Command complete text word
20603 This method is called by @value{GDBN} when the user attempts
20604 completion on this command. All forms of completion are handled by
20605 this method, that is, the @key{TAB} and @key{M-?} key bindings
20606 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
20609 The arguments @var{text} and @var{word} are both strings. @var{text}
20610 holds the complete command line up to the cursor's location.
20611 @var{word} holds the last word of the command line; this is computed
20612 using a word-breaking heuristic.
20614 The @code{complete} method can return several values:
20617 If the return value is a sequence, the contents of the sequence are
20618 used as the completions. It is up to @code{complete} to ensure that the
20619 contents actually do complete the word. A zero-length sequence is
20620 allowed, it means that there were no completions available. Only
20621 string elements of the sequence are used; other elements in the
20622 sequence are ignored.
20625 If the return value is one of the @samp{COMPLETE_} constants defined
20626 below, then the corresponding @value{GDBN}-internal completion
20627 function is invoked, and its result is used.
20630 All other results are treated as though there were no available
20635 When a new command is registered, it must be declared as a member of
20636 some general class of commands. This is used to classify top-level
20637 commands in the on-line help system; note that prefix commands are not
20638 listed under their own category but rather that of their top-level
20639 command. The available classifications are represented by constants
20640 defined in the @code{gdb} module:
20643 @findex COMMAND_NONE
20644 @findex gdb.COMMAND_NONE
20646 The command does not belong to any particular class. A command in
20647 this category will not be displayed in any of the help categories.
20649 @findex COMMAND_RUNNING
20650 @findex gdb.COMMAND_RUNNING
20651 @item COMMAND_RUNNING
20652 The command is related to running the inferior. For example,
20653 @code{start}, @code{step}, and @code{continue} are in this category.
20654 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
20655 commands in this category.
20657 @findex COMMAND_DATA
20658 @findex gdb.COMMAND_DATA
20660 The command is related to data or variables. For example,
20661 @code{call}, @code{find}, and @code{print} are in this category. Type
20662 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
20665 @findex COMMAND_STACK
20666 @findex gdb.COMMAND_STACK
20667 @item COMMAND_STACK
20668 The command has to do with manipulation of the stack. For example,
20669 @code{backtrace}, @code{frame}, and @code{return} are in this
20670 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
20671 list of commands in this category.
20673 @findex COMMAND_FILES
20674 @findex gdb.COMMAND_FILES
20675 @item COMMAND_FILES
20676 This class is used for file-related commands. For example,
20677 @code{file}, @code{list} and @code{section} are in this category.
20678 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
20679 commands in this category.
20681 @findex COMMAND_SUPPORT
20682 @findex gdb.COMMAND_SUPPORT
20683 @item COMMAND_SUPPORT
20684 This should be used for ``support facilities'', generally meaning
20685 things that are useful to the user when interacting with @value{GDBN},
20686 but not related to the state of the inferior. For example,
20687 @code{help}, @code{make}, and @code{shell} are in this category. Type
20688 @kbd{help support} at the @value{GDBN} prompt to see a list of
20689 commands in this category.
20691 @findex COMMAND_STATUS
20692 @findex gdb.COMMAND_STATUS
20693 @item COMMAND_STATUS
20694 The command is an @samp{info}-related command, that is, related to the
20695 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
20696 and @code{show} are in this category. Type @kbd{help status} at the
20697 @value{GDBN} prompt to see a list of commands in this category.
20699 @findex COMMAND_BREAKPOINTS
20700 @findex gdb.COMMAND_BREAKPOINTS
20701 @item COMMAND_BREAKPOINTS
20702 The command has to do with breakpoints. For example, @code{break},
20703 @code{clear}, and @code{delete} are in this category. Type @kbd{help
20704 breakpoints} at the @value{GDBN} prompt to see a list of commands in
20707 @findex COMMAND_TRACEPOINTS
20708 @findex gdb.COMMAND_TRACEPOINTS
20709 @item COMMAND_TRACEPOINTS
20710 The command has to do with tracepoints. For example, @code{trace},
20711 @code{actions}, and @code{tfind} are in this category. Type
20712 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
20713 commands in this category.
20715 @findex COMMAND_OBSCURE
20716 @findex gdb.COMMAND_OBSCURE
20717 @item COMMAND_OBSCURE
20718 The command is only used in unusual circumstances, or is not of
20719 general interest to users. For example, @code{checkpoint},
20720 @code{fork}, and @code{stop} are in this category. Type @kbd{help
20721 obscure} at the @value{GDBN} prompt to see a list of commands in this
20724 @findex COMMAND_MAINTENANCE
20725 @findex gdb.COMMAND_MAINTENANCE
20726 @item COMMAND_MAINTENANCE
20727 The command is only useful to @value{GDBN} maintainers. The
20728 @code{maintenance} and @code{flushregs} commands are in this category.
20729 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
20730 commands in this category.
20733 A new command can use a predefined completion function, either by
20734 specifying it via an argument at initialization, or by returning it
20735 from the @code{complete} method. These predefined completion
20736 constants are all defined in the @code{gdb} module:
20739 @findex COMPLETE_NONE
20740 @findex gdb.COMPLETE_NONE
20741 @item COMPLETE_NONE
20742 This constant means that no completion should be done.
20744 @findex COMPLETE_FILENAME
20745 @findex gdb.COMPLETE_FILENAME
20746 @item COMPLETE_FILENAME
20747 This constant means that filename completion should be performed.
20749 @findex COMPLETE_LOCATION
20750 @findex gdb.COMPLETE_LOCATION
20751 @item COMPLETE_LOCATION
20752 This constant means that location completion should be done.
20753 @xref{Specify Location}.
20755 @findex COMPLETE_COMMAND
20756 @findex gdb.COMPLETE_COMMAND
20757 @item COMPLETE_COMMAND
20758 This constant means that completion should examine @value{GDBN}
20761 @findex COMPLETE_SYMBOL
20762 @findex gdb.COMPLETE_SYMBOL
20763 @item COMPLETE_SYMBOL
20764 This constant means that completion should be done using symbol names
20768 The following code snippet shows how a trivial CLI command can be
20769 implemented in Python:
20772 class HelloWorld (gdb.Command):
20773 """Greet the whole world."""
20775 def __init__ (self):
20776 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20778 def invoke (self, arg, from_tty):
20779 print "Hello, World!"
20784 The last line instantiates the class, and is necessary to trigger the
20785 registration of the command with @value{GDBN}. Depending on how the
20786 Python code is read into @value{GDBN}, you may need to import the
20787 @code{gdb} module explicitly.
20789 @node Functions In Python
20790 @subsubsection Writing new convenience functions
20792 @cindex writing convenience functions
20793 @cindex convenience functions in python
20794 @cindex python convenience functions
20795 @tindex gdb.Function
20797 You can implement new convenience functions (@pxref{Convenience Vars})
20798 in Python. A convenience function is an instance of a subclass of the
20799 class @code{gdb.Function}.
20801 @defmethod Function __init__ name
20802 The initializer for @code{Function} registers the new function with
20803 @value{GDBN}. The argument @var{name} is the name of the function,
20804 a string. The function will be visible to the user as a convenience
20805 variable of type @code{internal function}, whose name is the same as
20806 the given @var{name}.
20808 The documentation for the new function is taken from the documentation
20809 string for the new class.
20812 @defmethod Function invoke @var{*args}
20813 When a convenience function is evaluated, its arguments are converted
20814 to instances of @code{gdb.Value}, and then the function's
20815 @code{invoke} method is called. Note that @value{GDBN} does not
20816 predetermine the arity of convenience functions. Instead, all
20817 available arguments are passed to @code{invoke}, following the
20818 standard Python calling convention. In particular, a convenience
20819 function can have default values for parameters without ill effect.
20821 The return value of this method is used as its value in the enclosing
20822 expression. If an ordinary Python value is returned, it is converted
20823 to a @code{gdb.Value} following the usual rules.
20826 The following code snippet shows how a trivial convenience function can
20827 be implemented in Python:
20830 class Greet (gdb.Function):
20831 """Return string to greet someone.
20832 Takes a name as argument."""
20834 def __init__ (self):
20835 super (Greet, self).__init__ ("greet")
20837 def invoke (self, name):
20838 return "Hello, %s!" % name.string ()
20843 The last line instantiates the class, and is necessary to trigger the
20844 registration of the function with @value{GDBN}. Depending on how the
20845 Python code is read into @value{GDBN}, you may need to import the
20846 @code{gdb} module explicitly.
20848 @node Objfiles In Python
20849 @subsubsection Objfiles In Python
20851 @cindex objfiles in python
20852 @tindex gdb.Objfile
20854 @value{GDBN} loads symbols for an inferior from various
20855 symbol-containing files (@pxref{Files}). These include the primary
20856 executable file, any shared libraries used by the inferior, and any
20857 separate debug info files (@pxref{Separate Debug Files}).
20858 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
20860 The following objfile-related functions are available in the
20863 @findex gdb.current_objfile
20864 @defun current_objfile
20865 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
20866 sets the ``current objfile'' to the corresponding objfile. This
20867 function returns the current objfile. If there is no current objfile,
20868 this function returns @code{None}.
20871 @findex gdb.objfiles
20873 Return a sequence of all the objfiles current known to @value{GDBN}.
20874 @xref{Objfiles In Python}.
20877 Each objfile is represented by an instance of the @code{gdb.Objfile}
20880 @defivar Objfile filename
20881 The file name of the objfile as a string.
20884 @defivar Objfile pretty_printers
20885 The @code{pretty_printers} attribute is a list of functions. It is
20886 used to look up pretty-printers. A @code{Value} is passed to each
20887 function in order; if the function returns @code{None}, then the
20888 search continues. Otherwise, the return value should be an object
20889 which is used to format the value. @xref{Pretty Printing}, for more
20893 @node Frames In Python
20894 @subsubsection Accessing inferior stack frames from Python.
20896 @cindex frames in python
20897 When the debugged program stops, @value{GDBN} is able to analyze its call
20898 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
20899 represents a frame in the stack. A @code{gdb.Frame} object is only valid
20900 while its corresponding frame exists in the inferior's stack. If you try
20901 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
20904 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
20908 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
20912 The following frame-related functions are available in the @code{gdb} module:
20914 @findex gdb.selected_frame
20915 @defun selected_frame
20916 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
20919 @defun frame_stop_reason_string reason
20920 Return a string explaining the reason why @value{GDBN} stopped unwinding
20921 frames, as expressed by the given @var{reason} code (an integer, see the
20922 @code{unwind_stop_reason} method further down in this section).
20925 A @code{gdb.Frame} object has the following methods:
20928 @defmethod Frame is_valid
20929 Returns true if the @code{gdb.Frame} object is valid, false if not.
20930 A frame object can become invalid if the frame it refers to doesn't
20931 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
20932 an exception if it is invalid at the time the method is called.
20935 @defmethod Frame name
20936 Returns the function name of the frame, or @code{None} if it can't be
20940 @defmethod Frame type
20941 Returns the type of the frame. The value can be one of
20942 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
20943 or @code{gdb.SENTINEL_FRAME}.
20946 @defmethod Frame unwind_stop_reason
20947 Return an integer representing the reason why it's not possible to find
20948 more frames toward the outermost frame. Use
20949 @code{gdb.frame_stop_reason_string} to convert the value returned by this
20950 function to a string.
20953 @defmethod Frame pc
20954 Returns the frame's resume address.
20957 @defmethod Frame block
20958 Return the frame's code block. @xref{Blocks In Python}.
20961 @defmethod Frame function
20962 Return the symbol for the function corresponding to this frame.
20963 @xref{Symbols In Python}.
20966 @defmethod Frame older
20967 Return the frame that called this frame.
20970 @defmethod Frame newer
20971 Return the frame called by this frame.
20974 @defmethod Frame find_sal
20975 Return the frame's symtab and line object.
20976 @xref{Symbol Tables In Python}.
20979 @defmethod Frame read_var variable @r{[}block@r{]}
20980 Return the value of @var{variable} in this frame. If the optional
20981 argument @var{block} is provided, search for the variable from that
20982 block; otherwise start at the frame's current block (which is
20983 determined by the frame's current program counter). @var{variable}
20984 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
20985 @code{gdb.Block} object.
20988 @defmethod Frame select
20989 Set this frame to be the selected frame. @xref{Stack, ,Examining the
20994 @node Blocks In Python
20995 @subsubsection Accessing frame blocks from Python.
20997 @cindex blocks in python
21000 Within each frame, @value{GDBN} maintains information on each block
21001 stored in that frame. These blocks are organized hierarchically, and
21002 are represented individually in Python as a @code{gdb.Block}.
21003 Please see @ref{Frames In Python}, for a more in-depth discussion on
21004 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
21005 detailed technical information on @value{GDBN}'s book-keeping of the
21008 The following block-related functions are available in the @code{gdb}
21011 @findex gdb.block_for_pc
21012 @defun block_for_pc pc
21013 Return the @code{gdb.Block} containing the given @var{pc} value. If the
21014 block cannot be found for the @var{pc} value specified, the function
21015 will return @code{None}.
21018 A @code{gdb.Block} object has the following attributes:
21021 @defivar Block start
21022 The start address of the block. This attribute is not writable.
21026 The end address of the block. This attribute is not writable.
21029 @defivar Block function
21030 The name of the block represented as a @code{gdb.Symbol}. If the
21031 block is not named, then this attribute holds @code{None}. This
21032 attribute is not writable.
21035 @defivar Block superblock
21036 The block containing this block. If this parent block does not exist,
21037 this attribute holds @code{None}. This attribute is not writable.
21041 @node Symbols In Python
21042 @subsubsection Python representation of Symbols.
21044 @cindex symbols in python
21047 @value{GDBN} represents every variable, function and type as an
21048 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
21049 Similarly, Python represents these symbols in @value{GDBN} with the
21050 @code{gdb.Symbol} object.
21052 The following symbol-related functions are available in the @code{gdb}
21055 @findex gdb.lookup_symbol
21056 @defun lookup_symbol name [block] [domain]
21057 This function searches for a symbol by name. The search scope can be
21058 restricted to the parameters defined in the optional domain and block
21061 @var{name} is the name of the symbol. It must be a string. The
21062 optional @var{block} argument restricts the search to symbols visible
21063 in that @var{block}. The @var{block} argument must be a
21064 @code{gdb.Block} object. The optional @var{domain} argument restricts
21065 the search to the domain type. The @var{domain} argument must be a
21066 domain constant defined in the @code{gdb} module and described later
21070 A @code{gdb.Symbol} object has the following attributes:
21073 @defivar Symbol symtab
21074 The symbol table in which the symbol appears. This attribute is
21075 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
21076 Python}. This attribute is not writable.
21079 @defivar Symbol name
21080 The name of the symbol as a string. This attribute is not writable.
21083 @defivar Symbol linkage_name
21084 The name of the symbol, as used by the linker (i.e., may be mangled).
21085 This attribute is not writable.
21088 @defivar Symbol print_name
21089 The name of the symbol in a form suitable for output. This is either
21090 @code{name} or @code{linkage_name}, depending on whether the user
21091 asked @value{GDBN} to display demangled or mangled names.
21094 @defivar Symbol addr_class
21095 The address class of the symbol. This classifies how to find the value
21096 of a symbol. Each address class is a constant defined in the
21097 @code{gdb} module and described later in this chapter.
21100 @defivar Symbol is_argument
21101 @code{True} if the symbol is an argument of a function.
21104 @defivar Symbol is_constant
21105 @code{True} if the symbol is a constant.
21108 @defivar Symbol is_function
21109 @code{True} if the symbol is a function or a method.
21112 @defivar Symbol is_variable
21113 @code{True} if the symbol is a variable.
21117 The available domain categories in @code{gdb.Symbol} are represented
21118 as constants in the @code{gdb} module:
21121 @findex SYMBOL_UNDEF_DOMAIN
21122 @findex gdb.SYMBOL_UNDEF_DOMAIN
21123 @item SYMBOL_UNDEF_DOMAIN
21124 This is used when a domain has not been discovered or none of the
21125 following domains apply. This usually indicates an error either
21126 in the symbol information or in @value{GDBN}'s handling of symbols.
21127 @findex SYMBOL_VAR_DOMAIN
21128 @findex gdb.SYMBOL_VAR_DOMAIN
21129 @item SYMBOL_VAR_DOMAIN
21130 This domain contains variables, function names, typedef names and enum
21132 @findex SYMBOL_STRUCT_DOMAIN
21133 @findex gdb.SYMBOL_STRUCT_DOMAIN
21134 @item SYMBOL_STRUCT_DOMAIN
21135 This domain holds struct, union and enum type names.
21136 @findex SYMBOL_LABEL_DOMAIN
21137 @findex gdb.SYMBOL_LABEL_DOMAIN
21138 @item SYMBOL_LABEL_DOMAIN
21139 This domain contains names of labels (for gotos).
21140 @findex SYMBOL_VARIABLES_DOMAIN
21141 @findex gdb.SYMBOL_VARIABLES_DOMAIN
21142 @item SYMBOL_VARIABLES_DOMAIN
21143 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
21144 contains everything minus functions and types.
21145 @findex SYMBOL_FUNCTIONS_DOMAIN
21146 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
21147 @item SYMBOL_FUNCTION_DOMAIN
21148 This domain contains all functions.
21149 @findex SYMBOL_TYPES_DOMAIN
21150 @findex gdb.SYMBOL_TYPES_DOMAIN
21151 @item SYMBOL_TYPES_DOMAIN
21152 This domain contains all types.
21155 The available address class categories in @code{gdb.Symbol} are represented
21156 as constants in the @code{gdb} module:
21159 @findex SYMBOL_LOC_UNDEF
21160 @findex gdb.SYMBOL_LOC_UNDEF
21161 @item SYMBOL_LOC_UNDEF
21162 If this is returned by address class, it indicates an error either in
21163 the symbol information or in @value{GDBN}'s handling of symbols.
21164 @findex SYMBOL_LOC_CONST
21165 @findex gdb.SYMBOL_LOC_CONST
21166 @item SYMBOL_LOC_CONST
21167 Value is constant int.
21168 @findex SYMBOL_LOC_STATIC
21169 @findex gdb.SYMBOL_LOC_STATIC
21170 @item SYMBOL_LOC_STATIC
21171 Value is at a fixed address.
21172 @findex SYMBOL_LOC_REGISTER
21173 @findex gdb.SYMBOL_LOC_REGISTER
21174 @item SYMBOL_LOC_REGISTER
21175 Value is in a register.
21176 @findex SYMBOL_LOC_ARG
21177 @findex gdb.SYMBOL_LOC_ARG
21178 @item SYMBOL_LOC_ARG
21179 Value is an argument. This value is at the offset stored within the
21180 symbol inside the frame's argument list.
21181 @findex SYMBOL_LOC_REF_ARG
21182 @findex gdb.SYMBOL_LOC_REF_ARG
21183 @item SYMBOL_LOC_REF_ARG
21184 Value address is stored in the frame's argument list. Just like
21185 @code{LOC_ARG} except that the value's address is stored at the
21186 offset, not the value itself.
21187 @findex SYMBOL_LOC_REGPARM_ADDR
21188 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
21189 @item SYMBOL_LOC_REGPARM_ADDR
21190 Value is a specified register. Just like @code{LOC_REGISTER} except
21191 the register holds the address of the argument instead of the argument
21193 @findex SYMBOL_LOC_LOCAL
21194 @findex gdb.SYMBOL_LOC_LOCAL
21195 @item SYMBOL_LOC_LOCAL
21196 Value is a local variable.
21197 @findex SYMBOL_LOC_TYPEDEF
21198 @findex gdb.SYMBOL_LOC_TYPEDEF
21199 @item SYMBOL_LOC_TYPEDEF
21200 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
21202 @findex SYMBOL_LOC_BLOCK
21203 @findex gdb.SYMBOL_LOC_BLOCK
21204 @item SYMBOL_LOC_BLOCK
21206 @findex SYMBOL_LOC_CONST_BYTES
21207 @findex gdb.SYMBOL_LOC_CONST_BYTES
21208 @item SYMBOL_LOC_CONST_BYTES
21209 Value is a byte-sequence.
21210 @findex SYMBOL_LOC_UNRESOLVED
21211 @findex gdb.SYMBOL_LOC_UNRESOLVED
21212 @item SYMBOL_LOC_UNRESOLVED
21213 Value is at a fixed address, but the address of the variable has to be
21214 determined from the minimal symbol table whenever the variable is
21216 @findex SYMBOL_LOC_OPTIMIZED_OUT
21217 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
21218 @item SYMBOL_LOC_OPTIMIZED_OUT
21219 The value does not actually exist in the program.
21220 @findex SYMBOL_LOC_COMPUTED
21221 @findex gdb.SYMBOL_LOC_COMPUTED
21222 @item SYMBOL_LOC_COMPUTED
21223 The value's address is a computed location.
21226 @node Symbol Tables In Python
21227 @subsubsection Symbol table representation in Python.
21229 @cindex symbol tables in python
21231 @tindex gdb.Symtab_and_line
21233 Access to symbol table data maintained by @value{GDBN} on the inferior
21234 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
21235 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
21236 from the @code{find_sal} method in @code{gdb.Frame} object.
21237 @xref{Frames In Python}.
21239 For more information on @value{GDBN}'s symbol table management, see
21240 @ref{Symbols, ,Examining the Symbol Table}, for more information.
21242 A @code{gdb.Symtab_and_line} object has the following attributes:
21245 @defivar Symtab_and_line symtab
21246 The symbol table object (@code{gdb.Symtab}) for this frame.
21247 This attribute is not writable.
21250 @defivar Symtab_and_line pc
21251 Indicates the current program counter address. This attribute is not
21255 @defivar Symtab_and_line line
21256 Indicates the current line number for this object. This
21257 attribute is not writable.
21261 A @code{gdb.Symtab} object has the following attributes:
21264 @defivar Symtab filename
21265 The symbol table's source filename. This attribute is not writable.
21268 @defivar Symtab objfile
21269 The symbol table's backing object file. @xref{Objfiles In Python}.
21270 This attribute is not writable.
21274 The following methods are provided:
21277 @defmethod Symtab fullname
21278 Return the symbol table's source absolute file name.
21282 @node Lazy Strings In Python
21283 @subsubsection Python representation of lazy strings.
21285 @cindex lazy strings in python
21286 @tindex gdb.LazyString
21288 A @dfn{lazy string} is a string whose contents is not retrieved or
21289 encoded until it is needed.
21291 A @code{gdb.LazyString} is represented in @value{GDBN} as an
21292 @code{address} that points to a region of memory, an @code{encoding}
21293 that will be used to encode that region of memory, and a @code{length}
21294 to delimit the region of memory that represents the string. The
21295 difference between a @code{gdb.LazyString} and a string wrapped within
21296 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
21297 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
21298 retrieved and encoded during printing, while a @code{gdb.Value}
21299 wrapping a string is immediately retrieved and encoded on creation.
21301 A @code{gdb.LazyString} object has the following functions:
21303 @defmethod LazyString value
21304 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
21305 will point to the string in memory, but will lose all the delayed
21306 retrieval, encoding and handling that @value{GDBN} applies to a
21307 @code{gdb.LazyString}.
21310 @defivar LazyString address
21311 This attribute holds the address of the string. This attribute is not
21315 @defivar LazyString length
21316 This attribute holds the length of the string in characters. If the
21317 length is -1, then the string will be fetched and encoded up to the
21318 first null of appropriate width. This attribute is not writable.
21321 @defivar LazyString encoding
21322 This attribute holds the encoding that will be applied to the string
21323 when the string is printed by @value{GDBN}. If the encoding is not
21324 set, or contains an empty string, then @value{GDBN} will select the
21325 most appropriate encoding when the string is printed. This attribute
21329 @defivar LazyString type
21330 This attribute holds the type that is represented by the lazy string's
21331 type. For a lazy string this will always be a pointer type. To
21332 resolve this to the lazy string's character type, use the type's
21333 @code{target} method. @xref{Types In Python}. This attribute is not
21338 @chapter Command Interpreters
21339 @cindex command interpreters
21341 @value{GDBN} supports multiple command interpreters, and some command
21342 infrastructure to allow users or user interface writers to switch
21343 between interpreters or run commands in other interpreters.
21345 @value{GDBN} currently supports two command interpreters, the console
21346 interpreter (sometimes called the command-line interpreter or @sc{cli})
21347 and the machine interface interpreter (or @sc{gdb/mi}). This manual
21348 describes both of these interfaces in great detail.
21350 By default, @value{GDBN} will start with the console interpreter.
21351 However, the user may choose to start @value{GDBN} with another
21352 interpreter by specifying the @option{-i} or @option{--interpreter}
21353 startup options. Defined interpreters include:
21357 @cindex console interpreter
21358 The traditional console or command-line interpreter. This is the most often
21359 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
21360 @value{GDBN} will use this interpreter.
21363 @cindex mi interpreter
21364 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
21365 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
21366 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
21370 @cindex mi2 interpreter
21371 The current @sc{gdb/mi} interface.
21374 @cindex mi1 interpreter
21375 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
21379 @cindex invoke another interpreter
21380 The interpreter being used by @value{GDBN} may not be dynamically
21381 switched at runtime. Although possible, this could lead to a very
21382 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
21383 enters the command "interpreter-set console" in a console view,
21384 @value{GDBN} would switch to using the console interpreter, rendering
21385 the IDE inoperable!
21387 @kindex interpreter-exec
21388 Although you may only choose a single interpreter at startup, you may execute
21389 commands in any interpreter from the current interpreter using the appropriate
21390 command. If you are running the console interpreter, simply use the
21391 @code{interpreter-exec} command:
21394 interpreter-exec mi "-data-list-register-names"
21397 @sc{gdb/mi} has a similar command, although it is only available in versions of
21398 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
21401 @chapter @value{GDBN} Text User Interface
21403 @cindex Text User Interface
21406 * TUI Overview:: TUI overview
21407 * TUI Keys:: TUI key bindings
21408 * TUI Single Key Mode:: TUI single key mode
21409 * TUI Commands:: TUI-specific commands
21410 * TUI Configuration:: TUI configuration variables
21413 The @value{GDBN} Text User Interface (TUI) is a terminal
21414 interface which uses the @code{curses} library to show the source
21415 file, the assembly output, the program registers and @value{GDBN}
21416 commands in separate text windows. The TUI mode is supported only
21417 on platforms where a suitable version of the @code{curses} library
21420 @pindex @value{GDBTUI}
21421 The TUI mode is enabled by default when you invoke @value{GDBN} as
21422 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
21423 You can also switch in and out of TUI mode while @value{GDBN} runs by
21424 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
21425 @xref{TUI Keys, ,TUI Key Bindings}.
21428 @section TUI Overview
21430 In TUI mode, @value{GDBN} can display several text windows:
21434 This window is the @value{GDBN} command window with the @value{GDBN}
21435 prompt and the @value{GDBN} output. The @value{GDBN} input is still
21436 managed using readline.
21439 The source window shows the source file of the program. The current
21440 line and active breakpoints are displayed in this window.
21443 The assembly window shows the disassembly output of the program.
21446 This window shows the processor registers. Registers are highlighted
21447 when their values change.
21450 The source and assembly windows show the current program position
21451 by highlighting the current line and marking it with a @samp{>} marker.
21452 Breakpoints are indicated with two markers. The first marker
21453 indicates the breakpoint type:
21457 Breakpoint which was hit at least once.
21460 Breakpoint which was never hit.
21463 Hardware breakpoint which was hit at least once.
21466 Hardware breakpoint which was never hit.
21469 The second marker indicates whether the breakpoint is enabled or not:
21473 Breakpoint is enabled.
21476 Breakpoint is disabled.
21479 The source, assembly and register windows are updated when the current
21480 thread changes, when the frame changes, or when the program counter
21483 These windows are not all visible at the same time. The command
21484 window is always visible. The others can be arranged in several
21495 source and assembly,
21498 source and registers, or
21501 assembly and registers.
21504 A status line above the command window shows the following information:
21508 Indicates the current @value{GDBN} target.
21509 (@pxref{Targets, ,Specifying a Debugging Target}).
21512 Gives the current process or thread number.
21513 When no process is being debugged, this field is set to @code{No process}.
21516 Gives the current function name for the selected frame.
21517 The name is demangled if demangling is turned on (@pxref{Print Settings}).
21518 When there is no symbol corresponding to the current program counter,
21519 the string @code{??} is displayed.
21522 Indicates the current line number for the selected frame.
21523 When the current line number is not known, the string @code{??} is displayed.
21526 Indicates the current program counter address.
21530 @section TUI Key Bindings
21531 @cindex TUI key bindings
21533 The TUI installs several key bindings in the readline keymaps
21534 (@pxref{Command Line Editing}). The following key bindings
21535 are installed for both TUI mode and the @value{GDBN} standard mode.
21544 Enter or leave the TUI mode. When leaving the TUI mode,
21545 the curses window management stops and @value{GDBN} operates using
21546 its standard mode, writing on the terminal directly. When reentering
21547 the TUI mode, control is given back to the curses windows.
21548 The screen is then refreshed.
21552 Use a TUI layout with only one window. The layout will
21553 either be @samp{source} or @samp{assembly}. When the TUI mode
21554 is not active, it will switch to the TUI mode.
21556 Think of this key binding as the Emacs @kbd{C-x 1} binding.
21560 Use a TUI layout with at least two windows. When the current
21561 layout already has two windows, the next layout with two windows is used.
21562 When a new layout is chosen, one window will always be common to the
21563 previous layout and the new one.
21565 Think of it as the Emacs @kbd{C-x 2} binding.
21569 Change the active window. The TUI associates several key bindings
21570 (like scrolling and arrow keys) with the active window. This command
21571 gives the focus to the next TUI window.
21573 Think of it as the Emacs @kbd{C-x o} binding.
21577 Switch in and out of the TUI SingleKey mode that binds single
21578 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
21581 The following key bindings only work in the TUI mode:
21586 Scroll the active window one page up.
21590 Scroll the active window one page down.
21594 Scroll the active window one line up.
21598 Scroll the active window one line down.
21602 Scroll the active window one column left.
21606 Scroll the active window one column right.
21610 Refresh the screen.
21613 Because the arrow keys scroll the active window in the TUI mode, they
21614 are not available for their normal use by readline unless the command
21615 window has the focus. When another window is active, you must use
21616 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
21617 and @kbd{C-f} to control the command window.
21619 @node TUI Single Key Mode
21620 @section TUI Single Key Mode
21621 @cindex TUI single key mode
21623 The TUI also provides a @dfn{SingleKey} mode, which binds several
21624 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
21625 switch into this mode, where the following key bindings are used:
21628 @kindex c @r{(SingleKey TUI key)}
21632 @kindex d @r{(SingleKey TUI key)}
21636 @kindex f @r{(SingleKey TUI key)}
21640 @kindex n @r{(SingleKey TUI key)}
21644 @kindex q @r{(SingleKey TUI key)}
21646 exit the SingleKey mode.
21648 @kindex r @r{(SingleKey TUI key)}
21652 @kindex s @r{(SingleKey TUI key)}
21656 @kindex u @r{(SingleKey TUI key)}
21660 @kindex v @r{(SingleKey TUI key)}
21664 @kindex w @r{(SingleKey TUI key)}
21669 Other keys temporarily switch to the @value{GDBN} command prompt.
21670 The key that was pressed is inserted in the editing buffer so that
21671 it is possible to type most @value{GDBN} commands without interaction
21672 with the TUI SingleKey mode. Once the command is entered the TUI
21673 SingleKey mode is restored. The only way to permanently leave
21674 this mode is by typing @kbd{q} or @kbd{C-x s}.
21678 @section TUI-specific Commands
21679 @cindex TUI commands
21681 The TUI has specific commands to control the text windows.
21682 These commands are always available, even when @value{GDBN} is not in
21683 the TUI mode. When @value{GDBN} is in the standard mode, most
21684 of these commands will automatically switch to the TUI mode.
21686 Note that if @value{GDBN}'s @code{stdout} is not connected to a
21687 terminal, or @value{GDBN} has been started with the machine interface
21688 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
21689 these commands will fail with an error, because it would not be
21690 possible or desirable to enable curses window management.
21695 List and give the size of all displayed windows.
21699 Display the next layout.
21702 Display the previous layout.
21705 Display the source window only.
21708 Display the assembly window only.
21711 Display the source and assembly window.
21714 Display the register window together with the source or assembly window.
21718 Make the next window active for scrolling.
21721 Make the previous window active for scrolling.
21724 Make the source window active for scrolling.
21727 Make the assembly window active for scrolling.
21730 Make the register window active for scrolling.
21733 Make the command window active for scrolling.
21737 Refresh the screen. This is similar to typing @kbd{C-L}.
21739 @item tui reg float
21741 Show the floating point registers in the register window.
21743 @item tui reg general
21744 Show the general registers in the register window.
21747 Show the next register group. The list of register groups as well as
21748 their order is target specific. The predefined register groups are the
21749 following: @code{general}, @code{float}, @code{system}, @code{vector},
21750 @code{all}, @code{save}, @code{restore}.
21752 @item tui reg system
21753 Show the system registers in the register window.
21757 Update the source window and the current execution point.
21759 @item winheight @var{name} +@var{count}
21760 @itemx winheight @var{name} -@var{count}
21762 Change the height of the window @var{name} by @var{count}
21763 lines. Positive counts increase the height, while negative counts
21766 @item tabset @var{nchars}
21768 Set the width of tab stops to be @var{nchars} characters.
21771 @node TUI Configuration
21772 @section TUI Configuration Variables
21773 @cindex TUI configuration variables
21775 Several configuration variables control the appearance of TUI windows.
21778 @item set tui border-kind @var{kind}
21779 @kindex set tui border-kind
21780 Select the border appearance for the source, assembly and register windows.
21781 The possible values are the following:
21784 Use a space character to draw the border.
21787 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
21790 Use the Alternate Character Set to draw the border. The border is
21791 drawn using character line graphics if the terminal supports them.
21794 @item set tui border-mode @var{mode}
21795 @kindex set tui border-mode
21796 @itemx set tui active-border-mode @var{mode}
21797 @kindex set tui active-border-mode
21798 Select the display attributes for the borders of the inactive windows
21799 or the active window. The @var{mode} can be one of the following:
21802 Use normal attributes to display the border.
21808 Use reverse video mode.
21811 Use half bright mode.
21813 @item half-standout
21814 Use half bright and standout mode.
21817 Use extra bright or bold mode.
21819 @item bold-standout
21820 Use extra bright or bold and standout mode.
21825 @chapter Using @value{GDBN} under @sc{gnu} Emacs
21828 @cindex @sc{gnu} Emacs
21829 A special interface allows you to use @sc{gnu} Emacs to view (and
21830 edit) the source files for the program you are debugging with
21833 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
21834 executable file you want to debug as an argument. This command starts
21835 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
21836 created Emacs buffer.
21837 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
21839 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
21844 All ``terminal'' input and output goes through an Emacs buffer, called
21847 This applies both to @value{GDBN} commands and their output, and to the input
21848 and output done by the program you are debugging.
21850 This is useful because it means that you can copy the text of previous
21851 commands and input them again; you can even use parts of the output
21854 All the facilities of Emacs' Shell mode are available for interacting
21855 with your program. In particular, you can send signals the usual
21856 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
21860 @value{GDBN} displays source code through Emacs.
21862 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
21863 source file for that frame and puts an arrow (@samp{=>}) at the
21864 left margin of the current line. Emacs uses a separate buffer for
21865 source display, and splits the screen to show both your @value{GDBN} session
21868 Explicit @value{GDBN} @code{list} or search commands still produce output as
21869 usual, but you probably have no reason to use them from Emacs.
21872 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
21873 a graphical mode, enabled by default, which provides further buffers
21874 that can control the execution and describe the state of your program.
21875 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
21877 If you specify an absolute file name when prompted for the @kbd{M-x
21878 gdb} argument, then Emacs sets your current working directory to where
21879 your program resides. If you only specify the file name, then Emacs
21880 sets your current working directory to to the directory associated
21881 with the previous buffer. In this case, @value{GDBN} may find your
21882 program by searching your environment's @code{PATH} variable, but on
21883 some operating systems it might not find the source. So, although the
21884 @value{GDBN} input and output session proceeds normally, the auxiliary
21885 buffer does not display the current source and line of execution.
21887 The initial working directory of @value{GDBN} is printed on the top
21888 line of the GUD buffer and this serves as a default for the commands
21889 that specify files for @value{GDBN} to operate on. @xref{Files,
21890 ,Commands to Specify Files}.
21892 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
21893 need to call @value{GDBN} by a different name (for example, if you
21894 keep several configurations around, with different names) you can
21895 customize the Emacs variable @code{gud-gdb-command-name} to run the
21898 In the GUD buffer, you can use these special Emacs commands in
21899 addition to the standard Shell mode commands:
21903 Describe the features of Emacs' GUD Mode.
21906 Execute to another source line, like the @value{GDBN} @code{step} command; also
21907 update the display window to show the current file and location.
21910 Execute to next source line in this function, skipping all function
21911 calls, like the @value{GDBN} @code{next} command. Then update the display window
21912 to show the current file and location.
21915 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
21916 display window accordingly.
21919 Execute until exit from the selected stack frame, like the @value{GDBN}
21920 @code{finish} command.
21923 Continue execution of your program, like the @value{GDBN} @code{continue}
21927 Go up the number of frames indicated by the numeric argument
21928 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
21929 like the @value{GDBN} @code{up} command.
21932 Go down the number of frames indicated by the numeric argument, like the
21933 @value{GDBN} @code{down} command.
21936 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
21937 tells @value{GDBN} to set a breakpoint on the source line point is on.
21939 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
21940 separate frame which shows a backtrace when the GUD buffer is current.
21941 Move point to any frame in the stack and type @key{RET} to make it
21942 become the current frame and display the associated source in the
21943 source buffer. Alternatively, click @kbd{Mouse-2} to make the
21944 selected frame become the current one. In graphical mode, the
21945 speedbar displays watch expressions.
21947 If you accidentally delete the source-display buffer, an easy way to get
21948 it back is to type the command @code{f} in the @value{GDBN} buffer, to
21949 request a frame display; when you run under Emacs, this recreates
21950 the source buffer if necessary to show you the context of the current
21953 The source files displayed in Emacs are in ordinary Emacs buffers
21954 which are visiting the source files in the usual way. You can edit
21955 the files with these buffers if you wish; but keep in mind that @value{GDBN}
21956 communicates with Emacs in terms of line numbers. If you add or
21957 delete lines from the text, the line numbers that @value{GDBN} knows cease
21958 to correspond properly with the code.
21960 A more detailed description of Emacs' interaction with @value{GDBN} is
21961 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
21964 @c The following dropped because Epoch is nonstandard. Reactivate
21965 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
21967 @kindex Emacs Epoch environment
21971 Version 18 of @sc{gnu} Emacs has a built-in window system
21972 called the @code{epoch}
21973 environment. Users of this environment can use a new command,
21974 @code{inspect} which performs identically to @code{print} except that
21975 each value is printed in its own window.
21980 @chapter The @sc{gdb/mi} Interface
21982 @unnumberedsec Function and Purpose
21984 @cindex @sc{gdb/mi}, its purpose
21985 @sc{gdb/mi} is a line based machine oriented text interface to
21986 @value{GDBN} and is activated by specifying using the
21987 @option{--interpreter} command line option (@pxref{Mode Options}). It
21988 is specifically intended to support the development of systems which
21989 use the debugger as just one small component of a larger system.
21991 This chapter is a specification of the @sc{gdb/mi} interface. It is written
21992 in the form of a reference manual.
21994 Note that @sc{gdb/mi} is still under construction, so some of the
21995 features described below are incomplete and subject to change
21996 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
21998 @unnumberedsec Notation and Terminology
22000 @cindex notational conventions, for @sc{gdb/mi}
22001 This chapter uses the following notation:
22005 @code{|} separates two alternatives.
22008 @code{[ @var{something} ]} indicates that @var{something} is optional:
22009 it may or may not be given.
22012 @code{( @var{group} )*} means that @var{group} inside the parentheses
22013 may repeat zero or more times.
22016 @code{( @var{group} )+} means that @var{group} inside the parentheses
22017 may repeat one or more times.
22020 @code{"@var{string}"} means a literal @var{string}.
22024 @heading Dependencies
22028 * GDB/MI General Design::
22029 * GDB/MI Command Syntax::
22030 * GDB/MI Compatibility with CLI::
22031 * GDB/MI Development and Front Ends::
22032 * GDB/MI Output Records::
22033 * GDB/MI Simple Examples::
22034 * GDB/MI Command Description Format::
22035 * GDB/MI Breakpoint Commands::
22036 * GDB/MI Program Context::
22037 * GDB/MI Thread Commands::
22038 * GDB/MI Program Execution::
22039 * GDB/MI Stack Manipulation::
22040 * GDB/MI Variable Objects::
22041 * GDB/MI Data Manipulation::
22042 * GDB/MI Tracepoint Commands::
22043 * GDB/MI Symbol Query::
22044 * GDB/MI File Commands::
22046 * GDB/MI Kod Commands::
22047 * GDB/MI Memory Overlay Commands::
22048 * GDB/MI Signal Handling Commands::
22050 * GDB/MI Target Manipulation::
22051 * GDB/MI File Transfer Commands::
22052 * GDB/MI Miscellaneous Commands::
22055 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22056 @node GDB/MI General Design
22057 @section @sc{gdb/mi} General Design
22058 @cindex GDB/MI General Design
22060 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
22061 parts---commands sent to @value{GDBN}, responses to those commands
22062 and notifications. Each command results in exactly one response,
22063 indicating either successful completion of the command, or an error.
22064 For the commands that do not resume the target, the response contains the
22065 requested information. For the commands that resume the target, the
22066 response only indicates whether the target was successfully resumed.
22067 Notifications is the mechanism for reporting changes in the state of the
22068 target, or in @value{GDBN} state, that cannot conveniently be associated with
22069 a command and reported as part of that command response.
22071 The important examples of notifications are:
22075 Exec notifications. These are used to report changes in
22076 target state---when a target is resumed, or stopped. It would not
22077 be feasible to include this information in response of resuming
22078 commands, because one resume commands can result in multiple events in
22079 different threads. Also, quite some time may pass before any event
22080 happens in the target, while a frontend needs to know whether the resuming
22081 command itself was successfully executed.
22084 Console output, and status notifications. Console output
22085 notifications are used to report output of CLI commands, as well as
22086 diagnostics for other commands. Status notifications are used to
22087 report the progress of a long-running operation. Naturally, including
22088 this information in command response would mean no output is produced
22089 until the command is finished, which is undesirable.
22092 General notifications. Commands may have various side effects on
22093 the @value{GDBN} or target state beyond their official purpose. For example,
22094 a command may change the selected thread. Although such changes can
22095 be included in command response, using notification allows for more
22096 orthogonal frontend design.
22100 There's no guarantee that whenever an MI command reports an error,
22101 @value{GDBN} or the target are in any specific state, and especially,
22102 the state is not reverted to the state before the MI command was
22103 processed. Therefore, whenever an MI command results in an error,
22104 we recommend that the frontend refreshes all the information shown in
22105 the user interface.
22109 * Context management::
22110 * Asynchronous and non-stop modes::
22114 @node Context management
22115 @subsection Context management
22117 In most cases when @value{GDBN} accesses the target, this access is
22118 done in context of a specific thread and frame (@pxref{Frames}).
22119 Often, even when accessing global data, the target requires that a thread
22120 be specified. The CLI interface maintains the selected thread and frame,
22121 and supplies them to target on each command. This is convenient,
22122 because a command line user would not want to specify that information
22123 explicitly on each command, and because user interacts with
22124 @value{GDBN} via a single terminal, so no confusion is possible as
22125 to what thread and frame are the current ones.
22127 In the case of MI, the concept of selected thread and frame is less
22128 useful. First, a frontend can easily remember this information
22129 itself. Second, a graphical frontend can have more than one window,
22130 each one used for debugging a different thread, and the frontend might
22131 want to access additional threads for internal purposes. This
22132 increases the risk that by relying on implicitly selected thread, the
22133 frontend may be operating on a wrong one. Therefore, each MI command
22134 should explicitly specify which thread and frame to operate on. To
22135 make it possible, each MI command accepts the @samp{--thread} and
22136 @samp{--frame} options, the value to each is @value{GDBN} identifier
22137 for thread and frame to operate on.
22139 Usually, each top-level window in a frontend allows the user to select
22140 a thread and a frame, and remembers the user selection for further
22141 operations. However, in some cases @value{GDBN} may suggest that the
22142 current thread be changed. For example, when stopping on a breakpoint
22143 it is reasonable to switch to the thread where breakpoint is hit. For
22144 another example, if the user issues the CLI @samp{thread} command via
22145 the frontend, it is desirable to change the frontend's selected thread to the
22146 one specified by user. @value{GDBN} communicates the suggestion to
22147 change current thread using the @samp{=thread-selected} notification.
22148 No such notification is available for the selected frame at the moment.
22150 Note that historically, MI shares the selected thread with CLI, so
22151 frontends used the @code{-thread-select} to execute commands in the
22152 right context. However, getting this to work right is cumbersome. The
22153 simplest way is for frontend to emit @code{-thread-select} command
22154 before every command. This doubles the number of commands that need
22155 to be sent. The alternative approach is to suppress @code{-thread-select}
22156 if the selected thread in @value{GDBN} is supposed to be identical to the
22157 thread the frontend wants to operate on. However, getting this
22158 optimization right can be tricky. In particular, if the frontend
22159 sends several commands to @value{GDBN}, and one of the commands changes the
22160 selected thread, then the behaviour of subsequent commands will
22161 change. So, a frontend should either wait for response from such
22162 problematic commands, or explicitly add @code{-thread-select} for
22163 all subsequent commands. No frontend is known to do this exactly
22164 right, so it is suggested to just always pass the @samp{--thread} and
22165 @samp{--frame} options.
22167 @node Asynchronous and non-stop modes
22168 @subsection Asynchronous command execution and non-stop mode
22170 On some targets, @value{GDBN} is capable of processing MI commands
22171 even while the target is running. This is called @dfn{asynchronous
22172 command execution} (@pxref{Background Execution}). The frontend may
22173 specify a preferrence for asynchronous execution using the
22174 @code{-gdb-set target-async 1} command, which should be emitted before
22175 either running the executable or attaching to the target. After the
22176 frontend has started the executable or attached to the target, it can
22177 find if asynchronous execution is enabled using the
22178 @code{-list-target-features} command.
22180 Even if @value{GDBN} can accept a command while target is running,
22181 many commands that access the target do not work when the target is
22182 running. Therefore, asynchronous command execution is most useful
22183 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
22184 it is possible to examine the state of one thread, while other threads
22187 When a given thread is running, MI commands that try to access the
22188 target in the context of that thread may not work, or may work only on
22189 some targets. In particular, commands that try to operate on thread's
22190 stack will not work, on any target. Commands that read memory, or
22191 modify breakpoints, may work or not work, depending on the target. Note
22192 that even commands that operate on global state, such as @code{print},
22193 @code{set}, and breakpoint commands, still access the target in the
22194 context of a specific thread, so frontend should try to find a
22195 stopped thread and perform the operation on that thread (using the
22196 @samp{--thread} option).
22198 Which commands will work in the context of a running thread is
22199 highly target dependent. However, the two commands
22200 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
22201 to find the state of a thread, will always work.
22203 @node Thread groups
22204 @subsection Thread groups
22205 @value{GDBN} may be used to debug several processes at the same time.
22206 On some platfroms, @value{GDBN} may support debugging of several
22207 hardware systems, each one having several cores with several different
22208 processes running on each core. This section describes the MI
22209 mechanism to support such debugging scenarios.
22211 The key observation is that regardless of the structure of the
22212 target, MI can have a global list of threads, because most commands that
22213 accept the @samp{--thread} option do not need to know what process that
22214 thread belongs to. Therefore, it is not necessary to introduce
22215 neither additional @samp{--process} option, nor an notion of the
22216 current process in the MI interface. The only strictly new feature
22217 that is required is the ability to find how the threads are grouped
22220 To allow the user to discover such grouping, and to support arbitrary
22221 hierarchy of machines/cores/processes, MI introduces the concept of a
22222 @dfn{thread group}. Thread group is a collection of threads and other
22223 thread groups. A thread group always has a string identifier, a type,
22224 and may have additional attributes specific to the type. A new
22225 command, @code{-list-thread-groups}, returns the list of top-level
22226 thread groups, which correspond to processes that @value{GDBN} is
22227 debugging at the moment. By passing an identifier of a thread group
22228 to the @code{-list-thread-groups} command, it is possible to obtain
22229 the members of specific thread group.
22231 To allow the user to easily discover processes, and other objects, he
22232 wishes to debug, a concept of @dfn{available thread group} is
22233 introduced. Available thread group is an thread group that
22234 @value{GDBN} is not debugging, but that can be attached to, using the
22235 @code{-target-attach} command. The list of available top-level thread
22236 groups can be obtained using @samp{-list-thread-groups --available}.
22237 In general, the content of a thread group may be only retrieved only
22238 after attaching to that thread group.
22240 Thread groups are related to inferiors (@pxref{Inferiors and
22241 Programs}). Each inferior corresponds to a thread group of a special
22242 type @samp{process}, and some additional operations are permitted on
22243 such thread groups.
22245 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22246 @node GDB/MI Command Syntax
22247 @section @sc{gdb/mi} Command Syntax
22250 * GDB/MI Input Syntax::
22251 * GDB/MI Output Syntax::
22254 @node GDB/MI Input Syntax
22255 @subsection @sc{gdb/mi} Input Syntax
22257 @cindex input syntax for @sc{gdb/mi}
22258 @cindex @sc{gdb/mi}, input syntax
22260 @item @var{command} @expansion{}
22261 @code{@var{cli-command} | @var{mi-command}}
22263 @item @var{cli-command} @expansion{}
22264 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
22265 @var{cli-command} is any existing @value{GDBN} CLI command.
22267 @item @var{mi-command} @expansion{}
22268 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
22269 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
22271 @item @var{token} @expansion{}
22272 "any sequence of digits"
22274 @item @var{option} @expansion{}
22275 @code{"-" @var{parameter} [ " " @var{parameter} ]}
22277 @item @var{parameter} @expansion{}
22278 @code{@var{non-blank-sequence} | @var{c-string}}
22280 @item @var{operation} @expansion{}
22281 @emph{any of the operations described in this chapter}
22283 @item @var{non-blank-sequence} @expansion{}
22284 @emph{anything, provided it doesn't contain special characters such as
22285 "-", @var{nl}, """ and of course " "}
22287 @item @var{c-string} @expansion{}
22288 @code{""" @var{seven-bit-iso-c-string-content} """}
22290 @item @var{nl} @expansion{}
22299 The CLI commands are still handled by the @sc{mi} interpreter; their
22300 output is described below.
22303 The @code{@var{token}}, when present, is passed back when the command
22307 Some @sc{mi} commands accept optional arguments as part of the parameter
22308 list. Each option is identified by a leading @samp{-} (dash) and may be
22309 followed by an optional argument parameter. Options occur first in the
22310 parameter list and can be delimited from normal parameters using
22311 @samp{--} (this is useful when some parameters begin with a dash).
22318 We want easy access to the existing CLI syntax (for debugging).
22321 We want it to be easy to spot a @sc{mi} operation.
22324 @node GDB/MI Output Syntax
22325 @subsection @sc{gdb/mi} Output Syntax
22327 @cindex output syntax of @sc{gdb/mi}
22328 @cindex @sc{gdb/mi}, output syntax
22329 The output from @sc{gdb/mi} consists of zero or more out-of-band records
22330 followed, optionally, by a single result record. This result record
22331 is for the most recent command. The sequence of output records is
22332 terminated by @samp{(gdb)}.
22334 If an input command was prefixed with a @code{@var{token}} then the
22335 corresponding output for that command will also be prefixed by that same
22339 @item @var{output} @expansion{}
22340 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
22342 @item @var{result-record} @expansion{}
22343 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
22345 @item @var{out-of-band-record} @expansion{}
22346 @code{@var{async-record} | @var{stream-record}}
22348 @item @var{async-record} @expansion{}
22349 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
22351 @item @var{exec-async-output} @expansion{}
22352 @code{[ @var{token} ] "*" @var{async-output}}
22354 @item @var{status-async-output} @expansion{}
22355 @code{[ @var{token} ] "+" @var{async-output}}
22357 @item @var{notify-async-output} @expansion{}
22358 @code{[ @var{token} ] "=" @var{async-output}}
22360 @item @var{async-output} @expansion{}
22361 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
22363 @item @var{result-class} @expansion{}
22364 @code{"done" | "running" | "connected" | "error" | "exit"}
22366 @item @var{async-class} @expansion{}
22367 @code{"stopped" | @var{others}} (where @var{others} will be added
22368 depending on the needs---this is still in development).
22370 @item @var{result} @expansion{}
22371 @code{ @var{variable} "=" @var{value}}
22373 @item @var{variable} @expansion{}
22374 @code{ @var{string} }
22376 @item @var{value} @expansion{}
22377 @code{ @var{const} | @var{tuple} | @var{list} }
22379 @item @var{const} @expansion{}
22380 @code{@var{c-string}}
22382 @item @var{tuple} @expansion{}
22383 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
22385 @item @var{list} @expansion{}
22386 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
22387 @var{result} ( "," @var{result} )* "]" }
22389 @item @var{stream-record} @expansion{}
22390 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
22392 @item @var{console-stream-output} @expansion{}
22393 @code{"~" @var{c-string}}
22395 @item @var{target-stream-output} @expansion{}
22396 @code{"@@" @var{c-string}}
22398 @item @var{log-stream-output} @expansion{}
22399 @code{"&" @var{c-string}}
22401 @item @var{nl} @expansion{}
22404 @item @var{token} @expansion{}
22405 @emph{any sequence of digits}.
22413 All output sequences end in a single line containing a period.
22416 The @code{@var{token}} is from the corresponding request. Note that
22417 for all async output, while the token is allowed by the grammar and
22418 may be output by future versions of @value{GDBN} for select async
22419 output messages, it is generally omitted. Frontends should treat
22420 all async output as reporting general changes in the state of the
22421 target and there should be no need to associate async output to any
22425 @cindex status output in @sc{gdb/mi}
22426 @var{status-async-output} contains on-going status information about the
22427 progress of a slow operation. It can be discarded. All status output is
22428 prefixed by @samp{+}.
22431 @cindex async output in @sc{gdb/mi}
22432 @var{exec-async-output} contains asynchronous state change on the target
22433 (stopped, started, disappeared). All async output is prefixed by
22437 @cindex notify output in @sc{gdb/mi}
22438 @var{notify-async-output} contains supplementary information that the
22439 client should handle (e.g., a new breakpoint information). All notify
22440 output is prefixed by @samp{=}.
22443 @cindex console output in @sc{gdb/mi}
22444 @var{console-stream-output} is output that should be displayed as is in the
22445 console. It is the textual response to a CLI command. All the console
22446 output is prefixed by @samp{~}.
22449 @cindex target output in @sc{gdb/mi}
22450 @var{target-stream-output} is the output produced by the target program.
22451 All the target output is prefixed by @samp{@@}.
22454 @cindex log output in @sc{gdb/mi}
22455 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
22456 instance messages that should be displayed as part of an error log. All
22457 the log output is prefixed by @samp{&}.
22460 @cindex list output in @sc{gdb/mi}
22461 New @sc{gdb/mi} commands should only output @var{lists} containing
22467 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
22468 details about the various output records.
22470 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22471 @node GDB/MI Compatibility with CLI
22472 @section @sc{gdb/mi} Compatibility with CLI
22474 @cindex compatibility, @sc{gdb/mi} and CLI
22475 @cindex @sc{gdb/mi}, compatibility with CLI
22477 For the developers convenience CLI commands can be entered directly,
22478 but there may be some unexpected behaviour. For example, commands
22479 that query the user will behave as if the user replied yes, breakpoint
22480 command lists are not executed and some CLI commands, such as
22481 @code{if}, @code{when} and @code{define}, prompt for further input with
22482 @samp{>}, which is not valid MI output.
22484 This feature may be removed at some stage in the future and it is
22485 recommended that front ends use the @code{-interpreter-exec} command
22486 (@pxref{-interpreter-exec}).
22488 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22489 @node GDB/MI Development and Front Ends
22490 @section @sc{gdb/mi} Development and Front Ends
22491 @cindex @sc{gdb/mi} development
22493 The application which takes the MI output and presents the state of the
22494 program being debugged to the user is called a @dfn{front end}.
22496 Although @sc{gdb/mi} is still incomplete, it is currently being used
22497 by a variety of front ends to @value{GDBN}. This makes it difficult
22498 to introduce new functionality without breaking existing usage. This
22499 section tries to minimize the problems by describing how the protocol
22502 Some changes in MI need not break a carefully designed front end, and
22503 for these the MI version will remain unchanged. The following is a
22504 list of changes that may occur within one level, so front ends should
22505 parse MI output in a way that can handle them:
22509 New MI commands may be added.
22512 New fields may be added to the output of any MI command.
22515 The range of values for fields with specified values, e.g.,
22516 @code{in_scope} (@pxref{-var-update}) may be extended.
22518 @c The format of field's content e.g type prefix, may change so parse it
22519 @c at your own risk. Yes, in general?
22521 @c The order of fields may change? Shouldn't really matter but it might
22522 @c resolve inconsistencies.
22525 If the changes are likely to break front ends, the MI version level
22526 will be increased by one. This will allow the front end to parse the
22527 output according to the MI version. Apart from mi0, new versions of
22528 @value{GDBN} will not support old versions of MI and it will be the
22529 responsibility of the front end to work with the new one.
22531 @c Starting with mi3, add a new command -mi-version that prints the MI
22534 The best way to avoid unexpected changes in MI that might break your front
22535 end is to make your project known to @value{GDBN} developers and
22536 follow development on @email{gdb@@sourceware.org} and
22537 @email{gdb-patches@@sourceware.org}.
22538 @cindex mailing lists
22540 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22541 @node GDB/MI Output Records
22542 @section @sc{gdb/mi} Output Records
22545 * GDB/MI Result Records::
22546 * GDB/MI Stream Records::
22547 * GDB/MI Async Records::
22548 * GDB/MI Frame Information::
22549 * GDB/MI Thread Information::
22552 @node GDB/MI Result Records
22553 @subsection @sc{gdb/mi} Result Records
22555 @cindex result records in @sc{gdb/mi}
22556 @cindex @sc{gdb/mi}, result records
22557 In addition to a number of out-of-band notifications, the response to a
22558 @sc{gdb/mi} command includes one of the following result indications:
22562 @item "^done" [ "," @var{results} ]
22563 The synchronous operation was successful, @code{@var{results}} are the return
22568 This result record is equivalent to @samp{^done}. Historically, it
22569 was output instead of @samp{^done} if the command has resumed the
22570 target. This behaviour is maintained for backward compatibility, but
22571 all frontends should treat @samp{^done} and @samp{^running}
22572 identically and rely on the @samp{*running} output record to determine
22573 which threads are resumed.
22577 @value{GDBN} has connected to a remote target.
22579 @item "^error" "," @var{c-string}
22581 The operation failed. The @code{@var{c-string}} contains the corresponding
22586 @value{GDBN} has terminated.
22590 @node GDB/MI Stream Records
22591 @subsection @sc{gdb/mi} Stream Records
22593 @cindex @sc{gdb/mi}, stream records
22594 @cindex stream records in @sc{gdb/mi}
22595 @value{GDBN} internally maintains a number of output streams: the console, the
22596 target, and the log. The output intended for each of these streams is
22597 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
22599 Each stream record begins with a unique @dfn{prefix character} which
22600 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
22601 Syntax}). In addition to the prefix, each stream record contains a
22602 @code{@var{string-output}}. This is either raw text (with an implicit new
22603 line) or a quoted C string (which does not contain an implicit newline).
22606 @item "~" @var{string-output}
22607 The console output stream contains text that should be displayed in the
22608 CLI console window. It contains the textual responses to CLI commands.
22610 @item "@@" @var{string-output}
22611 The target output stream contains any textual output from the running
22612 target. This is only present when GDB's event loop is truly
22613 asynchronous, which is currently only the case for remote targets.
22615 @item "&" @var{string-output}
22616 The log stream contains debugging messages being produced by @value{GDBN}'s
22620 @node GDB/MI Async Records
22621 @subsection @sc{gdb/mi} Async Records
22623 @cindex async records in @sc{gdb/mi}
22624 @cindex @sc{gdb/mi}, async records
22625 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
22626 additional changes that have occurred. Those changes can either be a
22627 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
22628 target activity (e.g., target stopped).
22630 The following is the list of possible async records:
22634 @item *running,thread-id="@var{thread}"
22635 The target is now running. The @var{thread} field tells which
22636 specific thread is now running, and can be @samp{all} if all threads
22637 are running. The frontend should assume that no interaction with a
22638 running thread is possible after this notification is produced.
22639 The frontend should not assume that this notification is output
22640 only once for any command. @value{GDBN} may emit this notification
22641 several times, either for different threads, because it cannot resume
22642 all threads together, or even for a single thread, if the thread must
22643 be stepped though some code before letting it run freely.
22645 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
22646 The target has stopped. The @var{reason} field can have one of the
22650 @item breakpoint-hit
22651 A breakpoint was reached.
22652 @item watchpoint-trigger
22653 A watchpoint was triggered.
22654 @item read-watchpoint-trigger
22655 A read watchpoint was triggered.
22656 @item access-watchpoint-trigger
22657 An access watchpoint was triggered.
22658 @item function-finished
22659 An -exec-finish or similar CLI command was accomplished.
22660 @item location-reached
22661 An -exec-until or similar CLI command was accomplished.
22662 @item watchpoint-scope
22663 A watchpoint has gone out of scope.
22664 @item end-stepping-range
22665 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
22666 similar CLI command was accomplished.
22667 @item exited-signalled
22668 The inferior exited because of a signal.
22670 The inferior exited.
22671 @item exited-normally
22672 The inferior exited normally.
22673 @item signal-received
22674 A signal was received by the inferior.
22677 The @var{id} field identifies the thread that directly caused the stop
22678 -- for example by hitting a breakpoint. Depending on whether all-stop
22679 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
22680 stop all threads, or only the thread that directly triggered the stop.
22681 If all threads are stopped, the @var{stopped} field will have the
22682 value of @code{"all"}. Otherwise, the value of the @var{stopped}
22683 field will be a list of thread identifiers. Presently, this list will
22684 always include a single thread, but frontend should be prepared to see
22685 several threads in the list. The @var{core} field reports the
22686 processor core on which the stop event has happened. This field may be absent
22687 if such information is not available.
22689 @item =thread-group-added,id="@var{id}"
22690 @itemx =thread-group-removed,id="@var{id}"
22691 A thread group was either added or removed. The @var{id} field
22692 contains the @value{GDBN} identifier of the thread group. When a thread
22693 group is added, it generally might not be associated with a running
22694 process. When a thread group is removed, its id becomes invalid and
22695 cannot be used in any way.
22697 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
22698 A thread group became associated with a running program,
22699 either because the program was just started or the thread group
22700 was attached to a program. The @var{id} field contains the
22701 @value{GDBN} identifier of the thread group. The @var{pid} field
22702 contains process identifier, specific to the operating system.
22704 @itemx =thread-group-exited,id="@var{id}"
22705 A thread group is no longer associated with a running program,
22706 either because the program has exited, or because it was detached
22707 from. The @var{id} field contains the @value{GDBN} identifier of the
22710 @item =thread-created,id="@var{id}",group-id="@var{gid}"
22711 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
22712 A thread either was created, or has exited. The @var{id} field
22713 contains the @value{GDBN} identifier of the thread. The @var{gid}
22714 field identifies the thread group this thread belongs to.
22716 @item =thread-selected,id="@var{id}"
22717 Informs that the selected thread was changed as result of the last
22718 command. This notification is not emitted as result of @code{-thread-select}
22719 command but is emitted whenever an MI command that is not documented
22720 to change the selected thread actually changes it. In particular,
22721 invoking, directly or indirectly (via user-defined command), the CLI
22722 @code{thread} command, will generate this notification.
22724 We suggest that in response to this notification, front ends
22725 highlight the selected thread and cause subsequent commands to apply to
22728 @item =library-loaded,...
22729 Reports that a new library file was loaded by the program. This
22730 notification has 4 fields---@var{id}, @var{target-name},
22731 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
22732 opaque identifier of the library. For remote debugging case,
22733 @var{target-name} and @var{host-name} fields give the name of the
22734 library file on the target, and on the host respectively. For native
22735 debugging, both those fields have the same value. The
22736 @var{symbols-loaded} field reports if the debug symbols for this
22737 library are loaded. The @var{thread-group} field, if present,
22738 specifies the id of the thread group in whose context the library was loaded.
22739 If the field is absent, it means the library was loaded in the context
22740 of all present thread groups.
22742 @item =library-unloaded,...
22743 Reports that a library was unloaded by the program. This notification
22744 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
22745 the same meaning as for the @code{=library-loaded} notification.
22746 The @var{thread-group} field, if present, specifies the id of the
22747 thread group in whose context the library was unloaded. If the field is
22748 absent, it means the library was unloaded in the context of all present
22753 @node GDB/MI Frame Information
22754 @subsection @sc{gdb/mi} Frame Information
22756 Response from many MI commands includes an information about stack
22757 frame. This information is a tuple that may have the following
22762 The level of the stack frame. The innermost frame has the level of
22763 zero. This field is always present.
22766 The name of the function corresponding to the frame. This field may
22767 be absent if @value{GDBN} is unable to determine the function name.
22770 The code address for the frame. This field is always present.
22773 The name of the source files that correspond to the frame's code
22774 address. This field may be absent.
22777 The source line corresponding to the frames' code address. This field
22781 The name of the binary file (either executable or shared library) the
22782 corresponds to the frame's code address. This field may be absent.
22786 @node GDB/MI Thread Information
22787 @subsection @sc{gdb/mi} Thread Information
22789 Whenever @value{GDBN} has to report an information about a thread, it
22790 uses a tuple with the following fields:
22794 The numeric id assigned to the thread by @value{GDBN}. This field is
22798 Target-specific string identifying the thread. This field is always present.
22801 Additional information about the thread provided by the target.
22802 It is supposed to be human-readable and not interpreted by the
22803 frontend. This field is optional.
22806 Either @samp{stopped} or @samp{running}, depending on whether the
22807 thread is presently running. This field is always present.
22810 The value of this field is an integer number of the processor core the
22811 thread was last seen on. This field is optional.
22815 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22816 @node GDB/MI Simple Examples
22817 @section Simple Examples of @sc{gdb/mi} Interaction
22818 @cindex @sc{gdb/mi}, simple examples
22820 This subsection presents several simple examples of interaction using
22821 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
22822 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
22823 the output received from @sc{gdb/mi}.
22825 Note the line breaks shown in the examples are here only for
22826 readability, they don't appear in the real output.
22828 @subheading Setting a Breakpoint
22830 Setting a breakpoint generates synchronous output which contains detailed
22831 information of the breakpoint.
22834 -> -break-insert main
22835 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
22836 enabled="y",addr="0x08048564",func="main",file="myprog.c",
22837 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
22841 @subheading Program Execution
22843 Program execution generates asynchronous records and MI gives the
22844 reason that execution stopped.
22850 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
22851 frame=@{addr="0x08048564",func="main",
22852 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
22853 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
22858 <- *stopped,reason="exited-normally"
22862 @subheading Quitting @value{GDBN}
22864 Quitting @value{GDBN} just prints the result class @samp{^exit}.
22872 Please note that @samp{^exit} is printed immediately, but it might
22873 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
22874 performs necessary cleanups, including killing programs being debugged
22875 or disconnecting from debug hardware, so the frontend should wait till
22876 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
22877 fails to exit in reasonable time.
22879 @subheading A Bad Command
22881 Here's what happens if you pass a non-existent command:
22885 <- ^error,msg="Undefined MI command: rubbish"
22890 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22891 @node GDB/MI Command Description Format
22892 @section @sc{gdb/mi} Command Description Format
22894 The remaining sections describe blocks of commands. Each block of
22895 commands is laid out in a fashion similar to this section.
22897 @subheading Motivation
22899 The motivation for this collection of commands.
22901 @subheading Introduction
22903 A brief introduction to this collection of commands as a whole.
22905 @subheading Commands
22907 For each command in the block, the following is described:
22909 @subsubheading Synopsis
22912 -command @var{args}@dots{}
22915 @subsubheading Result
22917 @subsubheading @value{GDBN} Command
22919 The corresponding @value{GDBN} CLI command(s), if any.
22921 @subsubheading Example
22923 Example(s) formatted for readability. Some of the described commands have
22924 not been implemented yet and these are labeled N.A.@: (not available).
22927 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22928 @node GDB/MI Breakpoint Commands
22929 @section @sc{gdb/mi} Breakpoint Commands
22931 @cindex breakpoint commands for @sc{gdb/mi}
22932 @cindex @sc{gdb/mi}, breakpoint commands
22933 This section documents @sc{gdb/mi} commands for manipulating
22936 @subheading The @code{-break-after} Command
22937 @findex -break-after
22939 @subsubheading Synopsis
22942 -break-after @var{number} @var{count}
22945 The breakpoint number @var{number} is not in effect until it has been
22946 hit @var{count} times. To see how this is reflected in the output of
22947 the @samp{-break-list} command, see the description of the
22948 @samp{-break-list} command below.
22950 @subsubheading @value{GDBN} Command
22952 The corresponding @value{GDBN} command is @samp{ignore}.
22954 @subsubheading Example
22959 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
22960 enabled="y",addr="0x000100d0",func="main",file="hello.c",
22961 fullname="/home/foo/hello.c",line="5",times="0"@}
22968 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
22969 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22970 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22971 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22972 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22973 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22974 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22975 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22976 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
22977 line="5",times="0",ignore="3"@}]@}
22982 @subheading The @code{-break-catch} Command
22983 @findex -break-catch
22986 @subheading The @code{-break-commands} Command
22987 @findex -break-commands
22989 @subsubheading Synopsis
22992 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
22995 Specifies the CLI commands that should be executed when breakpoint
22996 @var{number} is hit. The parameters @var{command1} to @var{commandN}
22997 are the commands. If no command is specified, any previously-set
22998 commands are cleared. @xref{Break Commands}. Typical use of this
22999 functionality is tracing a program, that is, printing of values of
23000 some variables whenever breakpoint is hit and then continuing.
23002 @subsubheading @value{GDBN} Command
23004 The corresponding @value{GDBN} command is @samp{commands}.
23006 @subsubheading Example
23011 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
23012 enabled="y",addr="0x000100d0",func="main",file="hello.c",
23013 fullname="/home/foo/hello.c",line="5",times="0"@}
23015 -break-commands 1 "print v" "continue"
23020 @subheading The @code{-break-condition} Command
23021 @findex -break-condition
23023 @subsubheading Synopsis
23026 -break-condition @var{number} @var{expr}
23029 Breakpoint @var{number} will stop the program only if the condition in
23030 @var{expr} is true. The condition becomes part of the
23031 @samp{-break-list} output (see the description of the @samp{-break-list}
23034 @subsubheading @value{GDBN} Command
23036 The corresponding @value{GDBN} command is @samp{condition}.
23038 @subsubheading Example
23042 -break-condition 1 1
23046 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23047 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23048 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23049 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23050 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23051 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23052 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23053 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23054 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23055 line="5",cond="1",times="0",ignore="3"@}]@}
23059 @subheading The @code{-break-delete} Command
23060 @findex -break-delete
23062 @subsubheading Synopsis
23065 -break-delete ( @var{breakpoint} )+
23068 Delete the breakpoint(s) whose number(s) are specified in the argument
23069 list. This is obviously reflected in the breakpoint list.
23071 @subsubheading @value{GDBN} Command
23073 The corresponding @value{GDBN} command is @samp{delete}.
23075 @subsubheading Example
23083 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
23084 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23085 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23086 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23087 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23088 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23089 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23094 @subheading The @code{-break-disable} Command
23095 @findex -break-disable
23097 @subsubheading Synopsis
23100 -break-disable ( @var{breakpoint} )+
23103 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
23104 break list is now set to @samp{n} for the named @var{breakpoint}(s).
23106 @subsubheading @value{GDBN} Command
23108 The corresponding @value{GDBN} command is @samp{disable}.
23110 @subsubheading Example
23118 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23119 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23120 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23121 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23122 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23123 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23124 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23125 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
23126 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23127 line="5",times="0"@}]@}
23131 @subheading The @code{-break-enable} Command
23132 @findex -break-enable
23134 @subsubheading Synopsis
23137 -break-enable ( @var{breakpoint} )+
23140 Enable (previously disabled) @var{breakpoint}(s).
23142 @subsubheading @value{GDBN} Command
23144 The corresponding @value{GDBN} command is @samp{enable}.
23146 @subsubheading Example
23154 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23155 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23156 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23157 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23158 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23159 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23160 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23161 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
23162 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23163 line="5",times="0"@}]@}
23167 @subheading The @code{-break-info} Command
23168 @findex -break-info
23170 @subsubheading Synopsis
23173 -break-info @var{breakpoint}
23177 Get information about a single breakpoint.
23179 @subsubheading @value{GDBN} Command
23181 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
23183 @subsubheading Example
23186 @subheading The @code{-break-insert} Command
23187 @findex -break-insert
23189 @subsubheading Synopsis
23192 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
23193 [ -c @var{condition} ] [ -i @var{ignore-count} ]
23194 [ -p @var{thread} ] [ @var{location} ]
23198 If specified, @var{location}, can be one of:
23205 @item filename:linenum
23206 @item filename:function
23210 The possible optional parameters of this command are:
23214 Insert a temporary breakpoint.
23216 Insert a hardware breakpoint.
23217 @item -c @var{condition}
23218 Make the breakpoint conditional on @var{condition}.
23219 @item -i @var{ignore-count}
23220 Initialize the @var{ignore-count}.
23222 If @var{location} cannot be parsed (for example if it
23223 refers to unknown files or functions), create a pending
23224 breakpoint. Without this flag, @value{GDBN} will report
23225 an error, and won't create a breakpoint, if @var{location}
23228 Create a disabled breakpoint.
23230 Create a tracepoint. @xref{Tracepoints}. When this parameter
23231 is used together with @samp{-h}, a fast tracepoint is created.
23234 @subsubheading Result
23236 The result is in the form:
23239 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
23240 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
23241 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
23242 times="@var{times}"@}
23246 where @var{number} is the @value{GDBN} number for this breakpoint,
23247 @var{funcname} is the name of the function where the breakpoint was
23248 inserted, @var{filename} is the name of the source file which contains
23249 this function, @var{lineno} is the source line number within that file
23250 and @var{times} the number of times that the breakpoint has been hit
23251 (always 0 for -break-insert but may be greater for -break-info or -break-list
23252 which use the same output).
23254 Note: this format is open to change.
23255 @c An out-of-band breakpoint instead of part of the result?
23257 @subsubheading @value{GDBN} Command
23259 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
23260 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
23262 @subsubheading Example
23267 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
23268 fullname="/home/foo/recursive2.c,line="4",times="0"@}
23270 -break-insert -t foo
23271 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
23272 fullname="/home/foo/recursive2.c,line="11",times="0"@}
23275 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23276 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23277 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23278 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23279 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23280 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23281 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23282 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23283 addr="0x0001072c", func="main",file="recursive2.c",
23284 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
23285 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
23286 addr="0x00010774",func="foo",file="recursive2.c",
23287 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
23289 -break-insert -r foo.*
23290 ~int foo(int, int);
23291 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
23292 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
23296 @subheading The @code{-break-list} Command
23297 @findex -break-list
23299 @subsubheading Synopsis
23305 Displays the list of inserted breakpoints, showing the following fields:
23309 number of the breakpoint
23311 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
23313 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
23316 is the breakpoint enabled or no: @samp{y} or @samp{n}
23318 memory location at which the breakpoint is set
23320 logical location of the breakpoint, expressed by function name, file
23323 number of times the breakpoint has been hit
23326 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
23327 @code{body} field is an empty list.
23329 @subsubheading @value{GDBN} Command
23331 The corresponding @value{GDBN} command is @samp{info break}.
23333 @subsubheading Example
23338 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23339 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23340 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23341 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23342 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23343 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23344 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23345 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23346 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
23347 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
23348 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
23349 line="13",times="0"@}]@}
23353 Here's an example of the result when there are no breakpoints:
23358 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
23359 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23360 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23361 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23362 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23363 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23364 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23369 @subheading The @code{-break-passcount} Command
23370 @findex -break-passcount
23372 @subsubheading Synopsis
23375 -break-passcount @var{tracepoint-number} @var{passcount}
23378 Set the passcount for tracepoint @var{tracepoint-number} to
23379 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
23380 is not a tracepoint, error is emitted. This corresponds to CLI
23381 command @samp{passcount}.
23383 @subheading The @code{-break-watch} Command
23384 @findex -break-watch
23386 @subsubheading Synopsis
23389 -break-watch [ -a | -r ]
23392 Create a watchpoint. With the @samp{-a} option it will create an
23393 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
23394 read from or on a write to the memory location. With the @samp{-r}
23395 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
23396 trigger only when the memory location is accessed for reading. Without
23397 either of the options, the watchpoint created is a regular watchpoint,
23398 i.e., it will trigger when the memory location is accessed for writing.
23399 @xref{Set Watchpoints, , Setting Watchpoints}.
23401 Note that @samp{-break-list} will report a single list of watchpoints and
23402 breakpoints inserted.
23404 @subsubheading @value{GDBN} Command
23406 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
23409 @subsubheading Example
23411 Setting a watchpoint on a variable in the @code{main} function:
23416 ^done,wpt=@{number="2",exp="x"@}
23421 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
23422 value=@{old="-268439212",new="55"@},
23423 frame=@{func="main",args=[],file="recursive2.c",
23424 fullname="/home/foo/bar/recursive2.c",line="5"@}
23428 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
23429 the program execution twice: first for the variable changing value, then
23430 for the watchpoint going out of scope.
23435 ^done,wpt=@{number="5",exp="C"@}
23440 *stopped,reason="watchpoint-trigger",
23441 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
23442 frame=@{func="callee4",args=[],
23443 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23444 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
23449 *stopped,reason="watchpoint-scope",wpnum="5",
23450 frame=@{func="callee3",args=[@{name="strarg",
23451 value="0x11940 \"A string argument.\""@}],
23452 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23453 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
23457 Listing breakpoints and watchpoints, at different points in the program
23458 execution. Note that once the watchpoint goes out of scope, it is
23464 ^done,wpt=@{number="2",exp="C"@}
23467 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23468 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23469 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23470 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23471 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23472 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23473 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23474 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23475 addr="0x00010734",func="callee4",
23476 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23477 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
23478 bkpt=@{number="2",type="watchpoint",disp="keep",
23479 enabled="y",addr="",what="C",times="0"@}]@}
23484 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
23485 value=@{old="-276895068",new="3"@},
23486 frame=@{func="callee4",args=[],
23487 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23488 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
23491 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23492 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23493 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23494 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23495 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23496 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23497 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23498 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23499 addr="0x00010734",func="callee4",
23500 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23501 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
23502 bkpt=@{number="2",type="watchpoint",disp="keep",
23503 enabled="y",addr="",what="C",times="-5"@}]@}
23507 ^done,reason="watchpoint-scope",wpnum="2",
23508 frame=@{func="callee3",args=[@{name="strarg",
23509 value="0x11940 \"A string argument.\""@}],
23510 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23511 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
23514 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23515 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23516 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23517 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23518 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23519 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23520 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23521 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23522 addr="0x00010734",func="callee4",
23523 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23524 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
23529 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23530 @node GDB/MI Program Context
23531 @section @sc{gdb/mi} Program Context
23533 @subheading The @code{-exec-arguments} Command
23534 @findex -exec-arguments
23537 @subsubheading Synopsis
23540 -exec-arguments @var{args}
23543 Set the inferior program arguments, to be used in the next
23546 @subsubheading @value{GDBN} Command
23548 The corresponding @value{GDBN} command is @samp{set args}.
23550 @subsubheading Example
23554 -exec-arguments -v word
23561 @subheading The @code{-exec-show-arguments} Command
23562 @findex -exec-show-arguments
23564 @subsubheading Synopsis
23567 -exec-show-arguments
23570 Print the arguments of the program.
23572 @subsubheading @value{GDBN} Command
23574 The corresponding @value{GDBN} command is @samp{show args}.
23576 @subsubheading Example
23581 @subheading The @code{-environment-cd} Command
23582 @findex -environment-cd
23584 @subsubheading Synopsis
23587 -environment-cd @var{pathdir}
23590 Set @value{GDBN}'s working directory.
23592 @subsubheading @value{GDBN} Command
23594 The corresponding @value{GDBN} command is @samp{cd}.
23596 @subsubheading Example
23600 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
23606 @subheading The @code{-environment-directory} Command
23607 @findex -environment-directory
23609 @subsubheading Synopsis
23612 -environment-directory [ -r ] [ @var{pathdir} ]+
23615 Add directories @var{pathdir} to beginning of search path for source files.
23616 If the @samp{-r} option is used, the search path is reset to the default
23617 search path. If directories @var{pathdir} are supplied in addition to the
23618 @samp{-r} option, the search path is first reset and then addition
23620 Multiple directories may be specified, separated by blanks. Specifying
23621 multiple directories in a single command
23622 results in the directories added to the beginning of the
23623 search path in the same order they were presented in the command.
23624 If blanks are needed as
23625 part of a directory name, double-quotes should be used around
23626 the name. In the command output, the path will show up separated
23627 by the system directory-separator character. The directory-separator
23628 character must not be used
23629 in any directory name.
23630 If no directories are specified, the current search path is displayed.
23632 @subsubheading @value{GDBN} Command
23634 The corresponding @value{GDBN} command is @samp{dir}.
23636 @subsubheading Example
23640 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
23641 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
23643 -environment-directory ""
23644 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
23646 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
23647 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
23649 -environment-directory -r
23650 ^done,source-path="$cdir:$cwd"
23655 @subheading The @code{-environment-path} Command
23656 @findex -environment-path
23658 @subsubheading Synopsis
23661 -environment-path [ -r ] [ @var{pathdir} ]+
23664 Add directories @var{pathdir} to beginning of search path for object files.
23665 If the @samp{-r} option is used, the search path is reset to the original
23666 search path that existed at gdb start-up. If directories @var{pathdir} are
23667 supplied in addition to the
23668 @samp{-r} option, the search path is first reset and then addition
23670 Multiple directories may be specified, separated by blanks. Specifying
23671 multiple directories in a single command
23672 results in the directories added to the beginning of the
23673 search path in the same order they were presented in the command.
23674 If blanks are needed as
23675 part of a directory name, double-quotes should be used around
23676 the name. In the command output, the path will show up separated
23677 by the system directory-separator character. The directory-separator
23678 character must not be used
23679 in any directory name.
23680 If no directories are specified, the current path is displayed.
23683 @subsubheading @value{GDBN} Command
23685 The corresponding @value{GDBN} command is @samp{path}.
23687 @subsubheading Example
23692 ^done,path="/usr/bin"
23694 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
23695 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
23697 -environment-path -r /usr/local/bin
23698 ^done,path="/usr/local/bin:/usr/bin"
23703 @subheading The @code{-environment-pwd} Command
23704 @findex -environment-pwd
23706 @subsubheading Synopsis
23712 Show the current working directory.
23714 @subsubheading @value{GDBN} Command
23716 The corresponding @value{GDBN} command is @samp{pwd}.
23718 @subsubheading Example
23723 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
23727 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23728 @node GDB/MI Thread Commands
23729 @section @sc{gdb/mi} Thread Commands
23732 @subheading The @code{-thread-info} Command
23733 @findex -thread-info
23735 @subsubheading Synopsis
23738 -thread-info [ @var{thread-id} ]
23741 Reports information about either a specific thread, if
23742 the @var{thread-id} parameter is present, or about all
23743 threads. When printing information about all threads,
23744 also reports the current thread.
23746 @subsubheading @value{GDBN} Command
23748 The @samp{info thread} command prints the same information
23751 @subsubheading Example
23756 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
23757 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
23758 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
23759 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
23760 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
23761 current-thread-id="1"
23765 The @samp{state} field may have the following values:
23769 The thread is stopped. Frame information is available for stopped
23773 The thread is running. There's no frame information for running
23778 @subheading The @code{-thread-list-ids} Command
23779 @findex -thread-list-ids
23781 @subsubheading Synopsis
23787 Produces a list of the currently known @value{GDBN} thread ids. At the
23788 end of the list it also prints the total number of such threads.
23790 This command is retained for historical reasons, the
23791 @code{-thread-info} command should be used instead.
23793 @subsubheading @value{GDBN} Command
23795 Part of @samp{info threads} supplies the same information.
23797 @subsubheading Example
23802 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
23803 current-thread-id="1",number-of-threads="3"
23808 @subheading The @code{-thread-select} Command
23809 @findex -thread-select
23811 @subsubheading Synopsis
23814 -thread-select @var{threadnum}
23817 Make @var{threadnum} the current thread. It prints the number of the new
23818 current thread, and the topmost frame for that thread.
23820 This command is deprecated in favor of explicitly using the
23821 @samp{--thread} option to each command.
23823 @subsubheading @value{GDBN} Command
23825 The corresponding @value{GDBN} command is @samp{thread}.
23827 @subsubheading Example
23834 *stopped,reason="end-stepping-range",thread-id="2",line="187",
23835 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
23839 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
23840 number-of-threads="3"
23843 ^done,new-thread-id="3",
23844 frame=@{level="0",func="vprintf",
23845 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
23846 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
23850 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23851 @node GDB/MI Program Execution
23852 @section @sc{gdb/mi} Program Execution
23854 These are the asynchronous commands which generate the out-of-band
23855 record @samp{*stopped}. Currently @value{GDBN} only really executes
23856 asynchronously with remote targets and this interaction is mimicked in
23859 @subheading The @code{-exec-continue} Command
23860 @findex -exec-continue
23862 @subsubheading Synopsis
23865 -exec-continue [--reverse] [--all|--thread-group N]
23868 Resumes the execution of the inferior program, which will continue
23869 to execute until it reaches a debugger stop event. If the
23870 @samp{--reverse} option is specified, execution resumes in reverse until
23871 it reaches a stop event. Stop events may include
23874 breakpoints or watchpoints
23876 signals or exceptions
23878 the end of the process (or its beginning under @samp{--reverse})
23880 the end or beginning of a replay log if one is being used.
23882 In all-stop mode (@pxref{All-Stop
23883 Mode}), may resume only one thread, or all threads, depending on the
23884 value of the @samp{scheduler-locking} variable. If @samp{--all} is
23885 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
23886 ignored in all-stop mode. If the @samp{--thread-group} options is
23887 specified, then all threads in that thread group are resumed.
23889 @subsubheading @value{GDBN} Command
23891 The corresponding @value{GDBN} corresponding is @samp{continue}.
23893 @subsubheading Example
23900 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
23901 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
23907 @subheading The @code{-exec-finish} Command
23908 @findex -exec-finish
23910 @subsubheading Synopsis
23913 -exec-finish [--reverse]
23916 Resumes the execution of the inferior program until the current
23917 function is exited. Displays the results returned by the function.
23918 If the @samp{--reverse} option is specified, resumes the reverse
23919 execution of the inferior program until the point where current
23920 function was called.
23922 @subsubheading @value{GDBN} Command
23924 The corresponding @value{GDBN} command is @samp{finish}.
23926 @subsubheading Example
23928 Function returning @code{void}.
23935 *stopped,reason="function-finished",frame=@{func="main",args=[],
23936 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
23940 Function returning other than @code{void}. The name of the internal
23941 @value{GDBN} variable storing the result is printed, together with the
23948 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
23949 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
23950 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23951 gdb-result-var="$1",return-value="0"
23956 @subheading The @code{-exec-interrupt} Command
23957 @findex -exec-interrupt
23959 @subsubheading Synopsis
23962 -exec-interrupt [--all|--thread-group N]
23965 Interrupts the background execution of the target. Note how the token
23966 associated with the stop message is the one for the execution command
23967 that has been interrupted. The token for the interrupt itself only
23968 appears in the @samp{^done} output. If the user is trying to
23969 interrupt a non-running program, an error message will be printed.
23971 Note that when asynchronous execution is enabled, this command is
23972 asynchronous just like other execution commands. That is, first the
23973 @samp{^done} response will be printed, and the target stop will be
23974 reported after that using the @samp{*stopped} notification.
23976 In non-stop mode, only the context thread is interrupted by default.
23977 All threads (in all inferiors) will be interrupted if the
23978 @samp{--all} option is specified. If the @samp{--thread-group}
23979 option is specified, all threads in that group will be interrupted.
23981 @subsubheading @value{GDBN} Command
23983 The corresponding @value{GDBN} command is @samp{interrupt}.
23985 @subsubheading Example
23996 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
23997 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
23998 fullname="/home/foo/bar/try.c",line="13"@}
24003 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
24007 @subheading The @code{-exec-jump} Command
24010 @subsubheading Synopsis
24013 -exec-jump @var{location}
24016 Resumes execution of the inferior program at the location specified by
24017 parameter. @xref{Specify Location}, for a description of the
24018 different forms of @var{location}.
24020 @subsubheading @value{GDBN} Command
24022 The corresponding @value{GDBN} command is @samp{jump}.
24024 @subsubheading Example
24027 -exec-jump foo.c:10
24028 *running,thread-id="all"
24033 @subheading The @code{-exec-next} Command
24036 @subsubheading Synopsis
24039 -exec-next [--reverse]
24042 Resumes execution of the inferior program, stopping when the beginning
24043 of the next source line is reached.
24045 If the @samp{--reverse} option is specified, resumes reverse execution
24046 of the inferior program, stopping at the beginning of the previous
24047 source line. If you issue this command on the first line of a
24048 function, it will take you back to the caller of that function, to the
24049 source line where the function was called.
24052 @subsubheading @value{GDBN} Command
24054 The corresponding @value{GDBN} command is @samp{next}.
24056 @subsubheading Example
24062 *stopped,reason="end-stepping-range",line="8",file="hello.c"
24067 @subheading The @code{-exec-next-instruction} Command
24068 @findex -exec-next-instruction
24070 @subsubheading Synopsis
24073 -exec-next-instruction [--reverse]
24076 Executes one machine instruction. If the instruction is a function
24077 call, continues until the function returns. If the program stops at an
24078 instruction in the middle of a source line, the address will be
24081 If the @samp{--reverse} option is specified, resumes reverse execution
24082 of the inferior program, stopping at the previous instruction. If the
24083 previously executed instruction was a return from another function,
24084 it will continue to execute in reverse until the call to that function
24085 (from the current stack frame) is reached.
24087 @subsubheading @value{GDBN} Command
24089 The corresponding @value{GDBN} command is @samp{nexti}.
24091 @subsubheading Example
24095 -exec-next-instruction
24099 *stopped,reason="end-stepping-range",
24100 addr="0x000100d4",line="5",file="hello.c"
24105 @subheading The @code{-exec-return} Command
24106 @findex -exec-return
24108 @subsubheading Synopsis
24114 Makes current function return immediately. Doesn't execute the inferior.
24115 Displays the new current frame.
24117 @subsubheading @value{GDBN} Command
24119 The corresponding @value{GDBN} command is @samp{return}.
24121 @subsubheading Example
24125 200-break-insert callee4
24126 200^done,bkpt=@{number="1",addr="0x00010734",
24127 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
24132 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
24133 frame=@{func="callee4",args=[],
24134 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24135 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
24141 111^done,frame=@{level="0",func="callee3",
24142 args=[@{name="strarg",
24143 value="0x11940 \"A string argument.\""@}],
24144 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24145 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24150 @subheading The @code{-exec-run} Command
24153 @subsubheading Synopsis
24156 -exec-run [--all | --thread-group N]
24159 Starts execution of the inferior from the beginning. The inferior
24160 executes until either a breakpoint is encountered or the program
24161 exits. In the latter case the output will include an exit code, if
24162 the program has exited exceptionally.
24164 When no option is specified, the current inferior is started. If the
24165 @samp{--thread-group} option is specified, it should refer to a thread
24166 group of type @samp{process}, and that thread group will be started.
24167 If the @samp{--all} option is specified, then all inferiors will be started.
24169 @subsubheading @value{GDBN} Command
24171 The corresponding @value{GDBN} command is @samp{run}.
24173 @subsubheading Examples
24178 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
24183 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
24184 frame=@{func="main",args=[],file="recursive2.c",
24185 fullname="/home/foo/bar/recursive2.c",line="4"@}
24190 Program exited normally:
24198 *stopped,reason="exited-normally"
24203 Program exited exceptionally:
24211 *stopped,reason="exited",exit-code="01"
24215 Another way the program can terminate is if it receives a signal such as
24216 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
24220 *stopped,reason="exited-signalled",signal-name="SIGINT",
24221 signal-meaning="Interrupt"
24225 @c @subheading -exec-signal
24228 @subheading The @code{-exec-step} Command
24231 @subsubheading Synopsis
24234 -exec-step [--reverse]
24237 Resumes execution of the inferior program, stopping when the beginning
24238 of the next source line is reached, if the next source line is not a
24239 function call. If it is, stop at the first instruction of the called
24240 function. If the @samp{--reverse} option is specified, resumes reverse
24241 execution of the inferior program, stopping at the beginning of the
24242 previously executed source line.
24244 @subsubheading @value{GDBN} Command
24246 The corresponding @value{GDBN} command is @samp{step}.
24248 @subsubheading Example
24250 Stepping into a function:
24256 *stopped,reason="end-stepping-range",
24257 frame=@{func="foo",args=[@{name="a",value="10"@},
24258 @{name="b",value="0"@}],file="recursive2.c",
24259 fullname="/home/foo/bar/recursive2.c",line="11"@}
24269 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
24274 @subheading The @code{-exec-step-instruction} Command
24275 @findex -exec-step-instruction
24277 @subsubheading Synopsis
24280 -exec-step-instruction [--reverse]
24283 Resumes the inferior which executes one machine instruction. If the
24284 @samp{--reverse} option is specified, resumes reverse execution of the
24285 inferior program, stopping at the previously executed instruction.
24286 The output, once @value{GDBN} has stopped, will vary depending on
24287 whether we have stopped in the middle of a source line or not. In the
24288 former case, the address at which the program stopped will be printed
24291 @subsubheading @value{GDBN} Command
24293 The corresponding @value{GDBN} command is @samp{stepi}.
24295 @subsubheading Example
24299 -exec-step-instruction
24303 *stopped,reason="end-stepping-range",
24304 frame=@{func="foo",args=[],file="try.c",
24305 fullname="/home/foo/bar/try.c",line="10"@}
24307 -exec-step-instruction
24311 *stopped,reason="end-stepping-range",
24312 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
24313 fullname="/home/foo/bar/try.c",line="10"@}
24318 @subheading The @code{-exec-until} Command
24319 @findex -exec-until
24321 @subsubheading Synopsis
24324 -exec-until [ @var{location} ]
24327 Executes the inferior until the @var{location} specified in the
24328 argument is reached. If there is no argument, the inferior executes
24329 until a source line greater than the current one is reached. The
24330 reason for stopping in this case will be @samp{location-reached}.
24332 @subsubheading @value{GDBN} Command
24334 The corresponding @value{GDBN} command is @samp{until}.
24336 @subsubheading Example
24340 -exec-until recursive2.c:6
24344 *stopped,reason="location-reached",frame=@{func="main",args=[],
24345 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
24350 @subheading -file-clear
24351 Is this going away????
24354 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24355 @node GDB/MI Stack Manipulation
24356 @section @sc{gdb/mi} Stack Manipulation Commands
24359 @subheading The @code{-stack-info-frame} Command
24360 @findex -stack-info-frame
24362 @subsubheading Synopsis
24368 Get info on the selected frame.
24370 @subsubheading @value{GDBN} Command
24372 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
24373 (without arguments).
24375 @subsubheading Example
24380 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
24381 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24382 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
24386 @subheading The @code{-stack-info-depth} Command
24387 @findex -stack-info-depth
24389 @subsubheading Synopsis
24392 -stack-info-depth [ @var{max-depth} ]
24395 Return the depth of the stack. If the integer argument @var{max-depth}
24396 is specified, do not count beyond @var{max-depth} frames.
24398 @subsubheading @value{GDBN} Command
24400 There's no equivalent @value{GDBN} command.
24402 @subsubheading Example
24404 For a stack with frame levels 0 through 11:
24411 -stack-info-depth 4
24414 -stack-info-depth 12
24417 -stack-info-depth 11
24420 -stack-info-depth 13
24425 @subheading The @code{-stack-list-arguments} Command
24426 @findex -stack-list-arguments
24428 @subsubheading Synopsis
24431 -stack-list-arguments @var{print-values}
24432 [ @var{low-frame} @var{high-frame} ]
24435 Display a list of the arguments for the frames between @var{low-frame}
24436 and @var{high-frame} (inclusive). If @var{low-frame} and
24437 @var{high-frame} are not provided, list the arguments for the whole
24438 call stack. If the two arguments are equal, show the single frame
24439 at the corresponding level. It is an error if @var{low-frame} is
24440 larger than the actual number of frames. On the other hand,
24441 @var{high-frame} may be larger than the actual number of frames, in
24442 which case only existing frames will be returned.
24444 If @var{print-values} is 0 or @code{--no-values}, print only the names of
24445 the variables; if it is 1 or @code{--all-values}, print also their
24446 values; and if it is 2 or @code{--simple-values}, print the name,
24447 type and value for simple data types, and the name and type for arrays,
24448 structures and unions.
24450 Use of this command to obtain arguments in a single frame is
24451 deprecated in favor of the @samp{-stack-list-variables} command.
24453 @subsubheading @value{GDBN} Command
24455 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
24456 @samp{gdb_get_args} command which partially overlaps with the
24457 functionality of @samp{-stack-list-arguments}.
24459 @subsubheading Example
24466 frame=@{level="0",addr="0x00010734",func="callee4",
24467 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24468 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
24469 frame=@{level="1",addr="0x0001076c",func="callee3",
24470 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24471 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
24472 frame=@{level="2",addr="0x0001078c",func="callee2",
24473 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24474 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
24475 frame=@{level="3",addr="0x000107b4",func="callee1",
24476 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24477 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
24478 frame=@{level="4",addr="0x000107e0",func="main",
24479 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24480 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
24482 -stack-list-arguments 0
24485 frame=@{level="0",args=[]@},
24486 frame=@{level="1",args=[name="strarg"]@},
24487 frame=@{level="2",args=[name="intarg",name="strarg"]@},
24488 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
24489 frame=@{level="4",args=[]@}]
24491 -stack-list-arguments 1
24494 frame=@{level="0",args=[]@},
24496 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
24497 frame=@{level="2",args=[
24498 @{name="intarg",value="2"@},
24499 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
24500 @{frame=@{level="3",args=[
24501 @{name="intarg",value="2"@},
24502 @{name="strarg",value="0x11940 \"A string argument.\""@},
24503 @{name="fltarg",value="3.5"@}]@},
24504 frame=@{level="4",args=[]@}]
24506 -stack-list-arguments 0 2 2
24507 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
24509 -stack-list-arguments 1 2 2
24510 ^done,stack-args=[frame=@{level="2",
24511 args=[@{name="intarg",value="2"@},
24512 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
24516 @c @subheading -stack-list-exception-handlers
24519 @subheading The @code{-stack-list-frames} Command
24520 @findex -stack-list-frames
24522 @subsubheading Synopsis
24525 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
24528 List the frames currently on the stack. For each frame it displays the
24533 The frame number, 0 being the topmost frame, i.e., the innermost function.
24535 The @code{$pc} value for that frame.
24539 File name of the source file where the function lives.
24541 Line number corresponding to the @code{$pc}.
24544 If invoked without arguments, this command prints a backtrace for the
24545 whole stack. If given two integer arguments, it shows the frames whose
24546 levels are between the two arguments (inclusive). If the two arguments
24547 are equal, it shows the single frame at the corresponding level. It is
24548 an error if @var{low-frame} is larger than the actual number of
24549 frames. On the other hand, @var{high-frame} may be larger than the
24550 actual number of frames, in which case only existing frames will be returned.
24552 @subsubheading @value{GDBN} Command
24554 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
24556 @subsubheading Example
24558 Full stack backtrace:
24564 [frame=@{level="0",addr="0x0001076c",func="foo",
24565 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
24566 frame=@{level="1",addr="0x000107a4",func="foo",
24567 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24568 frame=@{level="2",addr="0x000107a4",func="foo",
24569 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24570 frame=@{level="3",addr="0x000107a4",func="foo",
24571 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24572 frame=@{level="4",addr="0x000107a4",func="foo",
24573 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24574 frame=@{level="5",addr="0x000107a4",func="foo",
24575 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24576 frame=@{level="6",addr="0x000107a4",func="foo",
24577 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24578 frame=@{level="7",addr="0x000107a4",func="foo",
24579 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24580 frame=@{level="8",addr="0x000107a4",func="foo",
24581 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24582 frame=@{level="9",addr="0x000107a4",func="foo",
24583 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24584 frame=@{level="10",addr="0x000107a4",func="foo",
24585 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24586 frame=@{level="11",addr="0x00010738",func="main",
24587 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
24591 Show frames between @var{low_frame} and @var{high_frame}:
24595 -stack-list-frames 3 5
24597 [frame=@{level="3",addr="0x000107a4",func="foo",
24598 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24599 frame=@{level="4",addr="0x000107a4",func="foo",
24600 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24601 frame=@{level="5",addr="0x000107a4",func="foo",
24602 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
24606 Show a single frame:
24610 -stack-list-frames 3 3
24612 [frame=@{level="3",addr="0x000107a4",func="foo",
24613 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
24618 @subheading The @code{-stack-list-locals} Command
24619 @findex -stack-list-locals
24621 @subsubheading Synopsis
24624 -stack-list-locals @var{print-values}
24627 Display the local variable names for the selected frame. If
24628 @var{print-values} is 0 or @code{--no-values}, print only the names of
24629 the variables; if it is 1 or @code{--all-values}, print also their
24630 values; and if it is 2 or @code{--simple-values}, print the name,
24631 type and value for simple data types, and the name and type for arrays,
24632 structures and unions. In this last case, a frontend can immediately
24633 display the value of simple data types and create variable objects for
24634 other data types when the user wishes to explore their values in
24637 This command is deprecated in favor of the
24638 @samp{-stack-list-variables} command.
24640 @subsubheading @value{GDBN} Command
24642 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
24644 @subsubheading Example
24648 -stack-list-locals 0
24649 ^done,locals=[name="A",name="B",name="C"]
24651 -stack-list-locals --all-values
24652 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
24653 @{name="C",value="@{1, 2, 3@}"@}]
24654 -stack-list-locals --simple-values
24655 ^done,locals=[@{name="A",type="int",value="1"@},
24656 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
24660 @subheading The @code{-stack-list-variables} Command
24661 @findex -stack-list-variables
24663 @subsubheading Synopsis
24666 -stack-list-variables @var{print-values}
24669 Display the names of local variables and function arguments for the selected frame. If
24670 @var{print-values} is 0 or @code{--no-values}, print only the names of
24671 the variables; if it is 1 or @code{--all-values}, print also their
24672 values; and if it is 2 or @code{--simple-values}, print the name,
24673 type and value for simple data types, and the name and type for arrays,
24674 structures and unions.
24676 @subsubheading Example
24680 -stack-list-variables --thread 1 --frame 0 --all-values
24681 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
24686 @subheading The @code{-stack-select-frame} Command
24687 @findex -stack-select-frame
24689 @subsubheading Synopsis
24692 -stack-select-frame @var{framenum}
24695 Change the selected frame. Select a different frame @var{framenum} on
24698 This command in deprecated in favor of passing the @samp{--frame}
24699 option to every command.
24701 @subsubheading @value{GDBN} Command
24703 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
24704 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
24706 @subsubheading Example
24710 -stack-select-frame 2
24715 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24716 @node GDB/MI Variable Objects
24717 @section @sc{gdb/mi} Variable Objects
24721 @subheading Motivation for Variable Objects in @sc{gdb/mi}
24723 For the implementation of a variable debugger window (locals, watched
24724 expressions, etc.), we are proposing the adaptation of the existing code
24725 used by @code{Insight}.
24727 The two main reasons for that are:
24731 It has been proven in practice (it is already on its second generation).
24734 It will shorten development time (needless to say how important it is
24738 The original interface was designed to be used by Tcl code, so it was
24739 slightly changed so it could be used through @sc{gdb/mi}. This section
24740 describes the @sc{gdb/mi} operations that will be available and gives some
24741 hints about their use.
24743 @emph{Note}: In addition to the set of operations described here, we
24744 expect the @sc{gui} implementation of a variable window to require, at
24745 least, the following operations:
24748 @item @code{-gdb-show} @code{output-radix}
24749 @item @code{-stack-list-arguments}
24750 @item @code{-stack-list-locals}
24751 @item @code{-stack-select-frame}
24756 @subheading Introduction to Variable Objects
24758 @cindex variable objects in @sc{gdb/mi}
24760 Variable objects are "object-oriented" MI interface for examining and
24761 changing values of expressions. Unlike some other MI interfaces that
24762 work with expressions, variable objects are specifically designed for
24763 simple and efficient presentation in the frontend. A variable object
24764 is identified by string name. When a variable object is created, the
24765 frontend specifies the expression for that variable object. The
24766 expression can be a simple variable, or it can be an arbitrary complex
24767 expression, and can even involve CPU registers. After creating a
24768 variable object, the frontend can invoke other variable object
24769 operations---for example to obtain or change the value of a variable
24770 object, or to change display format.
24772 Variable objects have hierarchical tree structure. Any variable object
24773 that corresponds to a composite type, such as structure in C, has
24774 a number of child variable objects, for example corresponding to each
24775 element of a structure. A child variable object can itself have
24776 children, recursively. Recursion ends when we reach
24777 leaf variable objects, which always have built-in types. Child variable
24778 objects are created only by explicit request, so if a frontend
24779 is not interested in the children of a particular variable object, no
24780 child will be created.
24782 For a leaf variable object it is possible to obtain its value as a
24783 string, or set the value from a string. String value can be also
24784 obtained for a non-leaf variable object, but it's generally a string
24785 that only indicates the type of the object, and does not list its
24786 contents. Assignment to a non-leaf variable object is not allowed.
24788 A frontend does not need to read the values of all variable objects each time
24789 the program stops. Instead, MI provides an update command that lists all
24790 variable objects whose values has changed since the last update
24791 operation. This considerably reduces the amount of data that must
24792 be transferred to the frontend. As noted above, children variable
24793 objects are created on demand, and only leaf variable objects have a
24794 real value. As result, gdb will read target memory only for leaf
24795 variables that frontend has created.
24797 The automatic update is not always desirable. For example, a frontend
24798 might want to keep a value of some expression for future reference,
24799 and never update it. For another example, fetching memory is
24800 relatively slow for embedded targets, so a frontend might want
24801 to disable automatic update for the variables that are either not
24802 visible on the screen, or ``closed''. This is possible using so
24803 called ``frozen variable objects''. Such variable objects are never
24804 implicitly updated.
24806 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
24807 fixed variable object, the expression is parsed when the variable
24808 object is created, including associating identifiers to specific
24809 variables. The meaning of expression never changes. For a floating
24810 variable object the values of variables whose names appear in the
24811 expressions are re-evaluated every time in the context of the current
24812 frame. Consider this example:
24817 struct work_state state;
24824 If a fixed variable object for the @code{state} variable is created in
24825 this function, and we enter the recursive call, the the variable
24826 object will report the value of @code{state} in the top-level
24827 @code{do_work} invocation. On the other hand, a floating variable
24828 object will report the value of @code{state} in the current frame.
24830 If an expression specified when creating a fixed variable object
24831 refers to a local variable, the variable object becomes bound to the
24832 thread and frame in which the variable object is created. When such
24833 variable object is updated, @value{GDBN} makes sure that the
24834 thread/frame combination the variable object is bound to still exists,
24835 and re-evaluates the variable object in context of that thread/frame.
24837 The following is the complete set of @sc{gdb/mi} operations defined to
24838 access this functionality:
24840 @multitable @columnfractions .4 .6
24841 @item @strong{Operation}
24842 @tab @strong{Description}
24844 @item @code{-enable-pretty-printing}
24845 @tab enable Python-based pretty-printing
24846 @item @code{-var-create}
24847 @tab create a variable object
24848 @item @code{-var-delete}
24849 @tab delete the variable object and/or its children
24850 @item @code{-var-set-format}
24851 @tab set the display format of this variable
24852 @item @code{-var-show-format}
24853 @tab show the display format of this variable
24854 @item @code{-var-info-num-children}
24855 @tab tells how many children this object has
24856 @item @code{-var-list-children}
24857 @tab return a list of the object's children
24858 @item @code{-var-info-type}
24859 @tab show the type of this variable object
24860 @item @code{-var-info-expression}
24861 @tab print parent-relative expression that this variable object represents
24862 @item @code{-var-info-path-expression}
24863 @tab print full expression that this variable object represents
24864 @item @code{-var-show-attributes}
24865 @tab is this variable editable? does it exist here?
24866 @item @code{-var-evaluate-expression}
24867 @tab get the value of this variable
24868 @item @code{-var-assign}
24869 @tab set the value of this variable
24870 @item @code{-var-update}
24871 @tab update the variable and its children
24872 @item @code{-var-set-frozen}
24873 @tab set frozeness attribute
24874 @item @code{-var-set-update-range}
24875 @tab set range of children to display on update
24878 In the next subsection we describe each operation in detail and suggest
24879 how it can be used.
24881 @subheading Description And Use of Operations on Variable Objects
24883 @subheading The @code{-enable-pretty-printing} Command
24884 @findex -enable-pretty-printing
24887 -enable-pretty-printing
24890 @value{GDBN} allows Python-based visualizers to affect the output of the
24891 MI variable object commands. However, because there was no way to
24892 implement this in a fully backward-compatible way, a front end must
24893 request that this functionality be enabled.
24895 Once enabled, this feature cannot be disabled.
24897 Note that if Python support has not been compiled into @value{GDBN},
24898 this command will still succeed (and do nothing).
24900 This feature is currently (as of @value{GDBN} 7.0) experimental, and
24901 may work differently in future versions of @value{GDBN}.
24903 @subheading The @code{-var-create} Command
24904 @findex -var-create
24906 @subsubheading Synopsis
24909 -var-create @{@var{name} | "-"@}
24910 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
24913 This operation creates a variable object, which allows the monitoring of
24914 a variable, the result of an expression, a memory cell or a CPU
24917 The @var{name} parameter is the string by which the object can be
24918 referenced. It must be unique. If @samp{-} is specified, the varobj
24919 system will generate a string ``varNNNNNN'' automatically. It will be
24920 unique provided that one does not specify @var{name} of that format.
24921 The command fails if a duplicate name is found.
24923 The frame under which the expression should be evaluated can be
24924 specified by @var{frame-addr}. A @samp{*} indicates that the current
24925 frame should be used. A @samp{@@} indicates that a floating variable
24926 object must be created.
24928 @var{expression} is any expression valid on the current language set (must not
24929 begin with a @samp{*}), or one of the following:
24933 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
24936 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
24939 @samp{$@var{regname}} --- a CPU register name
24942 @cindex dynamic varobj
24943 A varobj's contents may be provided by a Python-based pretty-printer. In this
24944 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
24945 have slightly different semantics in some cases. If the
24946 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
24947 will never create a dynamic varobj. This ensures backward
24948 compatibility for existing clients.
24950 @subsubheading Result
24952 This operation returns attributes of the newly-created varobj. These
24957 The name of the varobj.
24960 The number of children of the varobj. This number is not necessarily
24961 reliable for a dynamic varobj. Instead, you must examine the
24962 @samp{has_more} attribute.
24965 The varobj's scalar value. For a varobj whose type is some sort of
24966 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
24967 will not be interesting.
24970 The varobj's type. This is a string representation of the type, as
24971 would be printed by the @value{GDBN} CLI.
24974 If a variable object is bound to a specific thread, then this is the
24975 thread's identifier.
24978 For a dynamic varobj, this indicates whether there appear to be any
24979 children available. For a non-dynamic varobj, this will be 0.
24982 This attribute will be present and have the value @samp{1} if the
24983 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
24984 then this attribute will not be present.
24987 A dynamic varobj can supply a display hint to the front end. The
24988 value comes directly from the Python pretty-printer object's
24989 @code{display_hint} method. @xref{Pretty Printing}.
24992 Typical output will look like this:
24995 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
24996 has_more="@var{has_more}"
25000 @subheading The @code{-var-delete} Command
25001 @findex -var-delete
25003 @subsubheading Synopsis
25006 -var-delete [ -c ] @var{name}
25009 Deletes a previously created variable object and all of its children.
25010 With the @samp{-c} option, just deletes the children.
25012 Returns an error if the object @var{name} is not found.
25015 @subheading The @code{-var-set-format} Command
25016 @findex -var-set-format
25018 @subsubheading Synopsis
25021 -var-set-format @var{name} @var{format-spec}
25024 Sets the output format for the value of the object @var{name} to be
25027 @anchor{-var-set-format}
25028 The syntax for the @var{format-spec} is as follows:
25031 @var{format-spec} @expansion{}
25032 @{binary | decimal | hexadecimal | octal | natural@}
25035 The natural format is the default format choosen automatically
25036 based on the variable type (like decimal for an @code{int}, hex
25037 for pointers, etc.).
25039 For a variable with children, the format is set only on the
25040 variable itself, and the children are not affected.
25042 @subheading The @code{-var-show-format} Command
25043 @findex -var-show-format
25045 @subsubheading Synopsis
25048 -var-show-format @var{name}
25051 Returns the format used to display the value of the object @var{name}.
25054 @var{format} @expansion{}
25059 @subheading The @code{-var-info-num-children} Command
25060 @findex -var-info-num-children
25062 @subsubheading Synopsis
25065 -var-info-num-children @var{name}
25068 Returns the number of children of a variable object @var{name}:
25074 Note that this number is not completely reliable for a dynamic varobj.
25075 It will return the current number of children, but more children may
25079 @subheading The @code{-var-list-children} Command
25080 @findex -var-list-children
25082 @subsubheading Synopsis
25085 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
25087 @anchor{-var-list-children}
25089 Return a list of the children of the specified variable object and
25090 create variable objects for them, if they do not already exist. With
25091 a single argument or if @var{print-values} has a value for of 0 or
25092 @code{--no-values}, print only the names of the variables; if
25093 @var{print-values} is 1 or @code{--all-values}, also print their
25094 values; and if it is 2 or @code{--simple-values} print the name and
25095 value for simple data types and just the name for arrays, structures
25098 @var{from} and @var{to}, if specified, indicate the range of children
25099 to report. If @var{from} or @var{to} is less than zero, the range is
25100 reset and all children will be reported. Otherwise, children starting
25101 at @var{from} (zero-based) and up to and excluding @var{to} will be
25104 If a child range is requested, it will only affect the current call to
25105 @code{-var-list-children}, but not future calls to @code{-var-update}.
25106 For this, you must instead use @code{-var-set-update-range}. The
25107 intent of this approach is to enable a front end to implement any
25108 update approach it likes; for example, scrolling a view may cause the
25109 front end to request more children with @code{-var-list-children}, and
25110 then the front end could call @code{-var-set-update-range} with a
25111 different range to ensure that future updates are restricted to just
25114 For each child the following results are returned:
25119 Name of the variable object created for this child.
25122 The expression to be shown to the user by the front end to designate this child.
25123 For example this may be the name of a structure member.
25125 For a dynamic varobj, this value cannot be used to form an
25126 expression. There is no way to do this at all with a dynamic varobj.
25128 For C/C@t{++} structures there are several pseudo children returned to
25129 designate access qualifiers. For these pseudo children @var{exp} is
25130 @samp{public}, @samp{private}, or @samp{protected}. In this case the
25131 type and value are not present.
25133 A dynamic varobj will not report the access qualifying
25134 pseudo-children, regardless of the language. This information is not
25135 available at all with a dynamic varobj.
25138 Number of children this child has. For a dynamic varobj, this will be
25142 The type of the child.
25145 If values were requested, this is the value.
25148 If this variable object is associated with a thread, this is the thread id.
25149 Otherwise this result is not present.
25152 If the variable object is frozen, this variable will be present with a value of 1.
25155 The result may have its own attributes:
25159 A dynamic varobj can supply a display hint to the front end. The
25160 value comes directly from the Python pretty-printer object's
25161 @code{display_hint} method. @xref{Pretty Printing}.
25164 This is an integer attribute which is nonzero if there are children
25165 remaining after the end of the selected range.
25168 @subsubheading Example
25172 -var-list-children n
25173 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
25174 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
25176 -var-list-children --all-values n
25177 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
25178 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
25182 @subheading The @code{-var-info-type} Command
25183 @findex -var-info-type
25185 @subsubheading Synopsis
25188 -var-info-type @var{name}
25191 Returns the type of the specified variable @var{name}. The type is
25192 returned as a string in the same format as it is output by the
25196 type=@var{typename}
25200 @subheading The @code{-var-info-expression} Command
25201 @findex -var-info-expression
25203 @subsubheading Synopsis
25206 -var-info-expression @var{name}
25209 Returns a string that is suitable for presenting this
25210 variable object in user interface. The string is generally
25211 not valid expression in the current language, and cannot be evaluated.
25213 For example, if @code{a} is an array, and variable object
25214 @code{A} was created for @code{a}, then we'll get this output:
25217 (gdb) -var-info-expression A.1
25218 ^done,lang="C",exp="1"
25222 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
25224 Note that the output of the @code{-var-list-children} command also
25225 includes those expressions, so the @code{-var-info-expression} command
25228 @subheading The @code{-var-info-path-expression} Command
25229 @findex -var-info-path-expression
25231 @subsubheading Synopsis
25234 -var-info-path-expression @var{name}
25237 Returns an expression that can be evaluated in the current
25238 context and will yield the same value that a variable object has.
25239 Compare this with the @code{-var-info-expression} command, which
25240 result can be used only for UI presentation. Typical use of
25241 the @code{-var-info-path-expression} command is creating a
25242 watchpoint from a variable object.
25244 This command is currently not valid for children of a dynamic varobj,
25245 and will give an error when invoked on one.
25247 For example, suppose @code{C} is a C@t{++} class, derived from class
25248 @code{Base}, and that the @code{Base} class has a member called
25249 @code{m_size}. Assume a variable @code{c} is has the type of
25250 @code{C} and a variable object @code{C} was created for variable
25251 @code{c}. Then, we'll get this output:
25253 (gdb) -var-info-path-expression C.Base.public.m_size
25254 ^done,path_expr=((Base)c).m_size)
25257 @subheading The @code{-var-show-attributes} Command
25258 @findex -var-show-attributes
25260 @subsubheading Synopsis
25263 -var-show-attributes @var{name}
25266 List attributes of the specified variable object @var{name}:
25269 status=@var{attr} [ ( ,@var{attr} )* ]
25273 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
25275 @subheading The @code{-var-evaluate-expression} Command
25276 @findex -var-evaluate-expression
25278 @subsubheading Synopsis
25281 -var-evaluate-expression [-f @var{format-spec}] @var{name}
25284 Evaluates the expression that is represented by the specified variable
25285 object and returns its value as a string. The format of the string
25286 can be specified with the @samp{-f} option. The possible values of
25287 this option are the same as for @code{-var-set-format}
25288 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
25289 the current display format will be used. The current display format
25290 can be changed using the @code{-var-set-format} command.
25296 Note that one must invoke @code{-var-list-children} for a variable
25297 before the value of a child variable can be evaluated.
25299 @subheading The @code{-var-assign} Command
25300 @findex -var-assign
25302 @subsubheading Synopsis
25305 -var-assign @var{name} @var{expression}
25308 Assigns the value of @var{expression} to the variable object specified
25309 by @var{name}. The object must be @samp{editable}. If the variable's
25310 value is altered by the assign, the variable will show up in any
25311 subsequent @code{-var-update} list.
25313 @subsubheading Example
25321 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
25325 @subheading The @code{-var-update} Command
25326 @findex -var-update
25328 @subsubheading Synopsis
25331 -var-update [@var{print-values}] @{@var{name} | "*"@}
25334 Reevaluate the expressions corresponding to the variable object
25335 @var{name} and all its direct and indirect children, and return the
25336 list of variable objects whose values have changed; @var{name} must
25337 be a root variable object. Here, ``changed'' means that the result of
25338 @code{-var-evaluate-expression} before and after the
25339 @code{-var-update} is different. If @samp{*} is used as the variable
25340 object names, all existing variable objects are updated, except
25341 for frozen ones (@pxref{-var-set-frozen}). The option
25342 @var{print-values} determines whether both names and values, or just
25343 names are printed. The possible values of this option are the same
25344 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
25345 recommended to use the @samp{--all-values} option, to reduce the
25346 number of MI commands needed on each program stop.
25348 With the @samp{*} parameter, if a variable object is bound to a
25349 currently running thread, it will not be updated, without any
25352 If @code{-var-set-update-range} was previously used on a varobj, then
25353 only the selected range of children will be reported.
25355 @code{-var-update} reports all the changed varobjs in a tuple named
25358 Each item in the change list is itself a tuple holding:
25362 The name of the varobj.
25365 If values were requested for this update, then this field will be
25366 present and will hold the value of the varobj.
25369 @anchor{-var-update}
25370 This field is a string which may take one of three values:
25374 The variable object's current value is valid.
25377 The variable object does not currently hold a valid value but it may
25378 hold one in the future if its associated expression comes back into
25382 The variable object no longer holds a valid value.
25383 This can occur when the executable file being debugged has changed,
25384 either through recompilation or by using the @value{GDBN} @code{file}
25385 command. The front end should normally choose to delete these variable
25389 In the future new values may be added to this list so the front should
25390 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
25393 This is only present if the varobj is still valid. If the type
25394 changed, then this will be the string @samp{true}; otherwise it will
25398 If the varobj's type changed, then this field will be present and will
25401 @item new_num_children
25402 For a dynamic varobj, if the number of children changed, or if the
25403 type changed, this will be the new number of children.
25405 The @samp{numchild} field in other varobj responses is generally not
25406 valid for a dynamic varobj -- it will show the number of children that
25407 @value{GDBN} knows about, but because dynamic varobjs lazily
25408 instantiate their children, this will not reflect the number of
25409 children which may be available.
25411 The @samp{new_num_children} attribute only reports changes to the
25412 number of children known by @value{GDBN}. This is the only way to
25413 detect whether an update has removed children (which necessarily can
25414 only happen at the end of the update range).
25417 The display hint, if any.
25420 This is an integer value, which will be 1 if there are more children
25421 available outside the varobj's update range.
25424 This attribute will be present and have the value @samp{1} if the
25425 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
25426 then this attribute will not be present.
25429 If new children were added to a dynamic varobj within the selected
25430 update range (as set by @code{-var-set-update-range}), then they will
25431 be listed in this attribute.
25434 @subsubheading Example
25441 -var-update --all-values var1
25442 ^done,changelist=[@{name="var1",value="3",in_scope="true",
25443 type_changed="false"@}]
25447 @subheading The @code{-var-set-frozen} Command
25448 @findex -var-set-frozen
25449 @anchor{-var-set-frozen}
25451 @subsubheading Synopsis
25454 -var-set-frozen @var{name} @var{flag}
25457 Set the frozenness flag on the variable object @var{name}. The
25458 @var{flag} parameter should be either @samp{1} to make the variable
25459 frozen or @samp{0} to make it unfrozen. If a variable object is
25460 frozen, then neither itself, nor any of its children, are
25461 implicitly updated by @code{-var-update} of
25462 a parent variable or by @code{-var-update *}. Only
25463 @code{-var-update} of the variable itself will update its value and
25464 values of its children. After a variable object is unfrozen, it is
25465 implicitly updated by all subsequent @code{-var-update} operations.
25466 Unfreezing a variable does not update it, only subsequent
25467 @code{-var-update} does.
25469 @subsubheading Example
25473 -var-set-frozen V 1
25478 @subheading The @code{-var-set-update-range} command
25479 @findex -var-set-update-range
25480 @anchor{-var-set-update-range}
25482 @subsubheading Synopsis
25485 -var-set-update-range @var{name} @var{from} @var{to}
25488 Set the range of children to be returned by future invocations of
25489 @code{-var-update}.
25491 @var{from} and @var{to} indicate the range of children to report. If
25492 @var{from} or @var{to} is less than zero, the range is reset and all
25493 children will be reported. Otherwise, children starting at @var{from}
25494 (zero-based) and up to and excluding @var{to} will be reported.
25496 @subsubheading Example
25500 -var-set-update-range V 1 2
25504 @subheading The @code{-var-set-visualizer} command
25505 @findex -var-set-visualizer
25506 @anchor{-var-set-visualizer}
25508 @subsubheading Synopsis
25511 -var-set-visualizer @var{name} @var{visualizer}
25514 Set a visualizer for the variable object @var{name}.
25516 @var{visualizer} is the visualizer to use. The special value
25517 @samp{None} means to disable any visualizer in use.
25519 If not @samp{None}, @var{visualizer} must be a Python expression.
25520 This expression must evaluate to a callable object which accepts a
25521 single argument. @value{GDBN} will call this object with the value of
25522 the varobj @var{name} as an argument (this is done so that the same
25523 Python pretty-printing code can be used for both the CLI and MI).
25524 When called, this object must return an object which conforms to the
25525 pretty-printing interface (@pxref{Pretty Printing}).
25527 The pre-defined function @code{gdb.default_visualizer} may be used to
25528 select a visualizer by following the built-in process
25529 (@pxref{Selecting Pretty-Printers}). This is done automatically when
25530 a varobj is created, and so ordinarily is not needed.
25532 This feature is only available if Python support is enabled. The MI
25533 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
25534 can be used to check this.
25536 @subsubheading Example
25538 Resetting the visualizer:
25542 -var-set-visualizer V None
25546 Reselecting the default (type-based) visualizer:
25550 -var-set-visualizer V gdb.default_visualizer
25554 Suppose @code{SomeClass} is a visualizer class. A lambda expression
25555 can be used to instantiate this class for a varobj:
25559 -var-set-visualizer V "lambda val: SomeClass()"
25563 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25564 @node GDB/MI Data Manipulation
25565 @section @sc{gdb/mi} Data Manipulation
25567 @cindex data manipulation, in @sc{gdb/mi}
25568 @cindex @sc{gdb/mi}, data manipulation
25569 This section describes the @sc{gdb/mi} commands that manipulate data:
25570 examine memory and registers, evaluate expressions, etc.
25572 @c REMOVED FROM THE INTERFACE.
25573 @c @subheading -data-assign
25574 @c Change the value of a program variable. Plenty of side effects.
25575 @c @subsubheading GDB Command
25577 @c @subsubheading Example
25580 @subheading The @code{-data-disassemble} Command
25581 @findex -data-disassemble
25583 @subsubheading Synopsis
25587 [ -s @var{start-addr} -e @var{end-addr} ]
25588 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
25596 @item @var{start-addr}
25597 is the beginning address (or @code{$pc})
25598 @item @var{end-addr}
25600 @item @var{filename}
25601 is the name of the file to disassemble
25602 @item @var{linenum}
25603 is the line number to disassemble around
25605 is the number of disassembly lines to be produced. If it is -1,
25606 the whole function will be disassembled, in case no @var{end-addr} is
25607 specified. If @var{end-addr} is specified as a non-zero value, and
25608 @var{lines} is lower than the number of disassembly lines between
25609 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
25610 displayed; if @var{lines} is higher than the number of lines between
25611 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
25614 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
25618 @subsubheading Result
25620 The output for each instruction is composed of four fields:
25629 Note that whatever included in the instruction field, is not manipulated
25630 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
25632 @subsubheading @value{GDBN} Command
25634 There's no direct mapping from this command to the CLI.
25636 @subsubheading Example
25638 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
25642 -data-disassemble -s $pc -e "$pc + 20" -- 0
25645 @{address="0x000107c0",func-name="main",offset="4",
25646 inst="mov 2, %o0"@},
25647 @{address="0x000107c4",func-name="main",offset="8",
25648 inst="sethi %hi(0x11800), %o2"@},
25649 @{address="0x000107c8",func-name="main",offset="12",
25650 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
25651 @{address="0x000107cc",func-name="main",offset="16",
25652 inst="sethi %hi(0x11800), %o2"@},
25653 @{address="0x000107d0",func-name="main",offset="20",
25654 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
25658 Disassemble the whole @code{main} function. Line 32 is part of
25662 -data-disassemble -f basics.c -l 32 -- 0
25664 @{address="0x000107bc",func-name="main",offset="0",
25665 inst="save %sp, -112, %sp"@},
25666 @{address="0x000107c0",func-name="main",offset="4",
25667 inst="mov 2, %o0"@},
25668 @{address="0x000107c4",func-name="main",offset="8",
25669 inst="sethi %hi(0x11800), %o2"@},
25671 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
25672 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
25676 Disassemble 3 instructions from the start of @code{main}:
25680 -data-disassemble -f basics.c -l 32 -n 3 -- 0
25682 @{address="0x000107bc",func-name="main",offset="0",
25683 inst="save %sp, -112, %sp"@},
25684 @{address="0x000107c0",func-name="main",offset="4",
25685 inst="mov 2, %o0"@},
25686 @{address="0x000107c4",func-name="main",offset="8",
25687 inst="sethi %hi(0x11800), %o2"@}]
25691 Disassemble 3 instructions from the start of @code{main} in mixed mode:
25695 -data-disassemble -f basics.c -l 32 -n 3 -- 1
25697 src_and_asm_line=@{line="31",
25698 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
25699 testsuite/gdb.mi/basics.c",line_asm_insn=[
25700 @{address="0x000107bc",func-name="main",offset="0",
25701 inst="save %sp, -112, %sp"@}]@},
25702 src_and_asm_line=@{line="32",
25703 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
25704 testsuite/gdb.mi/basics.c",line_asm_insn=[
25705 @{address="0x000107c0",func-name="main",offset="4",
25706 inst="mov 2, %o0"@},
25707 @{address="0x000107c4",func-name="main",offset="8",
25708 inst="sethi %hi(0x11800), %o2"@}]@}]
25713 @subheading The @code{-data-evaluate-expression} Command
25714 @findex -data-evaluate-expression
25716 @subsubheading Synopsis
25719 -data-evaluate-expression @var{expr}
25722 Evaluate @var{expr} as an expression. The expression could contain an
25723 inferior function call. The function call will execute synchronously.
25724 If the expression contains spaces, it must be enclosed in double quotes.
25726 @subsubheading @value{GDBN} Command
25728 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
25729 @samp{call}. In @code{gdbtk} only, there's a corresponding
25730 @samp{gdb_eval} command.
25732 @subsubheading Example
25734 In the following example, the numbers that precede the commands are the
25735 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
25736 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
25740 211-data-evaluate-expression A
25743 311-data-evaluate-expression &A
25744 311^done,value="0xefffeb7c"
25746 411-data-evaluate-expression A+3
25749 511-data-evaluate-expression "A + 3"
25755 @subheading The @code{-data-list-changed-registers} Command
25756 @findex -data-list-changed-registers
25758 @subsubheading Synopsis
25761 -data-list-changed-registers
25764 Display a list of the registers that have changed.
25766 @subsubheading @value{GDBN} Command
25768 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
25769 has the corresponding command @samp{gdb_changed_register_list}.
25771 @subsubheading Example
25773 On a PPC MBX board:
25781 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
25782 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
25785 -data-list-changed-registers
25786 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
25787 "10","11","13","14","15","16","17","18","19","20","21","22","23",
25788 "24","25","26","27","28","30","31","64","65","66","67","69"]
25793 @subheading The @code{-data-list-register-names} Command
25794 @findex -data-list-register-names
25796 @subsubheading Synopsis
25799 -data-list-register-names [ ( @var{regno} )+ ]
25802 Show a list of register names for the current target. If no arguments
25803 are given, it shows a list of the names of all the registers. If
25804 integer numbers are given as arguments, it will print a list of the
25805 names of the registers corresponding to the arguments. To ensure
25806 consistency between a register name and its number, the output list may
25807 include empty register names.
25809 @subsubheading @value{GDBN} Command
25811 @value{GDBN} does not have a command which corresponds to
25812 @samp{-data-list-register-names}. In @code{gdbtk} there is a
25813 corresponding command @samp{gdb_regnames}.
25815 @subsubheading Example
25817 For the PPC MBX board:
25820 -data-list-register-names
25821 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
25822 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
25823 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
25824 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
25825 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
25826 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
25827 "", "pc","ps","cr","lr","ctr","xer"]
25829 -data-list-register-names 1 2 3
25830 ^done,register-names=["r1","r2","r3"]
25834 @subheading The @code{-data-list-register-values} Command
25835 @findex -data-list-register-values
25837 @subsubheading Synopsis
25840 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
25843 Display the registers' contents. @var{fmt} is the format according to
25844 which the registers' contents are to be returned, followed by an optional
25845 list of numbers specifying the registers to display. A missing list of
25846 numbers indicates that the contents of all the registers must be returned.
25848 Allowed formats for @var{fmt} are:
25865 @subsubheading @value{GDBN} Command
25867 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
25868 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
25870 @subsubheading Example
25872 For a PPC MBX board (note: line breaks are for readability only, they
25873 don't appear in the actual output):
25877 -data-list-register-values r 64 65
25878 ^done,register-values=[@{number="64",value="0xfe00a300"@},
25879 @{number="65",value="0x00029002"@}]
25881 -data-list-register-values x
25882 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
25883 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
25884 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
25885 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
25886 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
25887 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
25888 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
25889 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
25890 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
25891 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
25892 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
25893 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
25894 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
25895 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
25896 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
25897 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
25898 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
25899 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
25900 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
25901 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
25902 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
25903 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
25904 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
25905 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
25906 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
25907 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
25908 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
25909 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
25910 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
25911 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
25912 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
25913 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
25914 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
25915 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
25916 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
25917 @{number="69",value="0x20002b03"@}]
25922 @subheading The @code{-data-read-memory} Command
25923 @findex -data-read-memory
25925 @subsubheading Synopsis
25928 -data-read-memory [ -o @var{byte-offset} ]
25929 @var{address} @var{word-format} @var{word-size}
25930 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
25937 @item @var{address}
25938 An expression specifying the address of the first memory word to be
25939 read. Complex expressions containing embedded white space should be
25940 quoted using the C convention.
25942 @item @var{word-format}
25943 The format to be used to print the memory words. The notation is the
25944 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
25947 @item @var{word-size}
25948 The size of each memory word in bytes.
25950 @item @var{nr-rows}
25951 The number of rows in the output table.
25953 @item @var{nr-cols}
25954 The number of columns in the output table.
25957 If present, indicates that each row should include an @sc{ascii} dump. The
25958 value of @var{aschar} is used as a padding character when a byte is not a
25959 member of the printable @sc{ascii} character set (printable @sc{ascii}
25960 characters are those whose code is between 32 and 126, inclusively).
25962 @item @var{byte-offset}
25963 An offset to add to the @var{address} before fetching memory.
25966 This command displays memory contents as a table of @var{nr-rows} by
25967 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
25968 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
25969 (returned as @samp{total-bytes}). Should less than the requested number
25970 of bytes be returned by the target, the missing words are identified
25971 using @samp{N/A}. The number of bytes read from the target is returned
25972 in @samp{nr-bytes} and the starting address used to read memory in
25975 The address of the next/previous row or page is available in
25976 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
25979 @subsubheading @value{GDBN} Command
25981 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
25982 @samp{gdb_get_mem} memory read command.
25984 @subsubheading Example
25986 Read six bytes of memory starting at @code{bytes+6} but then offset by
25987 @code{-6} bytes. Format as three rows of two columns. One byte per
25988 word. Display each word in hex.
25992 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
25993 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
25994 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
25995 prev-page="0x0000138a",memory=[
25996 @{addr="0x00001390",data=["0x00","0x01"]@},
25997 @{addr="0x00001392",data=["0x02","0x03"]@},
25998 @{addr="0x00001394",data=["0x04","0x05"]@}]
26002 Read two bytes of memory starting at address @code{shorts + 64} and
26003 display as a single word formatted in decimal.
26007 5-data-read-memory shorts+64 d 2 1 1
26008 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
26009 next-row="0x00001512",prev-row="0x0000150e",
26010 next-page="0x00001512",prev-page="0x0000150e",memory=[
26011 @{addr="0x00001510",data=["128"]@}]
26015 Read thirty two bytes of memory starting at @code{bytes+16} and format
26016 as eight rows of four columns. Include a string encoding with @samp{x}
26017 used as the non-printable character.
26021 4-data-read-memory bytes+16 x 1 8 4 x
26022 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
26023 next-row="0x000013c0",prev-row="0x0000139c",
26024 next-page="0x000013c0",prev-page="0x00001380",memory=[
26025 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
26026 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
26027 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
26028 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
26029 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
26030 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
26031 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
26032 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
26036 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26037 @node GDB/MI Tracepoint Commands
26038 @section @sc{gdb/mi} Tracepoint Commands
26040 The commands defined in this section implement MI support for
26041 tracepoints. For detailed introduction, see @ref{Tracepoints}.
26043 @subheading The @code{-trace-find} Command
26044 @findex -trace-find
26046 @subsubheading Synopsis
26049 -trace-find @var{mode} [@var{parameters}@dots{}]
26052 Find a trace frame using criteria defined by @var{mode} and
26053 @var{parameters}. The following table lists permissible
26054 modes and their parameters. For details of operation, see @ref{tfind}.
26059 No parameters are required. Stops examining trace frames.
26062 An integer is required as parameter. Selects tracepoint frame with
26065 @item tracepoint-number
26066 An integer is required as parameter. Finds next
26067 trace frame that corresponds to tracepoint with the specified number.
26070 An address is required as parameter. Finds
26071 next trace frame that corresponds to any tracepoint at the specified
26074 @item pc-inside-range
26075 Two addresses are required as parameters. Finds next trace
26076 frame that corresponds to a tracepoint at an address inside the
26077 specified range. Both bounds are considered to be inside the range.
26079 @item pc-outside-range
26080 Two addresses are required as parameters. Finds
26081 next trace frame that corresponds to a tracepoint at an address outside
26082 the specified range. Both bounds are considered to be inside the range.
26085 Line specification is required as parameter. @xref{Specify Location}.
26086 Finds next trace frame that corresponds to a tracepoint at
26087 the specified location.
26091 If @samp{none} was passed as @var{mode}, the response does not
26092 have fields. Otherwise, the response may have the following fields:
26096 This field has either @samp{0} or @samp{1} as the value, depending
26097 on whether a matching tracepoint was found.
26100 The index of the found traceframe. This field is present iff
26101 the @samp{found} field has value of @samp{1}.
26104 The index of the found tracepoint. This field is present iff
26105 the @samp{found} field has value of @samp{1}.
26108 The information about the frame corresponding to the found trace
26109 frame. This field is present only if a trace frame was found.
26110 @xref{GDB/MI Frame Information}, for description of this field.
26114 @subsubheading @value{GDBN} Command
26116 The corresponding @value{GDBN} command is @samp{tfind}.
26118 @subheading -trace-define-variable
26119 @findex -trace-define-variable
26121 @subsubheading Synopsis
26124 -trace-define-variable @var{name} [ @var{value} ]
26127 Create trace variable @var{name} if it does not exist. If
26128 @var{value} is specified, sets the initial value of the specified
26129 trace variable to that value. Note that the @var{name} should start
26130 with the @samp{$} character.
26132 @subsubheading @value{GDBN} Command
26134 The corresponding @value{GDBN} command is @samp{tvariable}.
26136 @subheading -trace-list-variables
26137 @findex -trace-list-variables
26139 @subsubheading Synopsis
26142 -trace-list-variables
26145 Return a table of all defined trace variables. Each element of the
26146 table has the following fields:
26150 The name of the trace variable. This field is always present.
26153 The initial value. This is a 64-bit signed integer. This
26154 field is always present.
26157 The value the trace variable has at the moment. This is a 64-bit
26158 signed integer. This field is absent iff current value is
26159 not defined, for example if the trace was never run, or is
26164 @subsubheading @value{GDBN} Command
26166 The corresponding @value{GDBN} command is @samp{tvariables}.
26168 @subsubheading Example
26172 -trace-list-variables
26173 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
26174 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
26175 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
26176 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
26177 body=[variable=@{name="$trace_timestamp",initial="0"@}
26178 variable=@{name="$foo",initial="10",current="15"@}]@}
26182 @subheading -trace-save
26183 @findex -trace-save
26185 @subsubheading Synopsis
26188 -trace-save [-r ] @var{filename}
26191 Saves the collected trace data to @var{filename}. Without the
26192 @samp{-r} option, the data is downloaded from the target and saved
26193 in a local file. With the @samp{-r} option the target is asked
26194 to perform the save.
26196 @subsubheading @value{GDBN} Command
26198 The corresponding @value{GDBN} command is @samp{tsave}.
26201 @subheading -trace-start
26202 @findex -trace-start
26204 @subsubheading Synopsis
26210 Starts a tracing experiments. The result of this command does not
26213 @subsubheading @value{GDBN} Command
26215 The corresponding @value{GDBN} command is @samp{tstart}.
26217 @subheading -trace-status
26218 @findex -trace-status
26220 @subsubheading Synopsis
26226 Obtains the status of a tracing experiement. The result may include
26227 the following fields:
26232 May have a value of either @samp{0}, when no tracing operations are
26233 supported, @samp{1}, when all tracing operations are supported, or
26234 @samp{file} when examining trace file. In the latter case, examining
26235 of trace frame is possible but new tracing experiement cannot be
26236 started. This field is always present.
26239 May have a value of either @samp{0} or @samp{1} depending on whether
26240 tracing experiement is in progress on target. This field is present
26241 if @samp{supported} field is not @samp{0}.
26244 Report the reason why the tracing was stopped last time. This field
26245 may be absent iff tracing was never stopped on target yet. The
26246 value of @samp{request} means the tracing was stopped as result of
26247 the @code{-trace-stop} command. The value of @samp{overflow} means
26248 the tracing buffer is full. The value of @samp{disconnection} means
26249 tracing was automatically stopped when @value{GDBN} has disconnected.
26250 The value of @samp{passcount} means tracing was stopped when a
26251 tracepoint was passed a maximal number of times for that tracepoint.
26252 This field is present if @samp{supported} field is not @samp{0}.
26254 @item stopping-tracepoint
26255 The number of tracepoint whose passcount as exceeded. This field is
26256 present iff the @samp{stop-reason} field has the value of
26260 This field is an integer number of currently collected frames. This
26265 These fields tell the current size of the tracing buffer and the
26266 remaining space. These field is optional.
26270 @subsubheading @value{GDBN} Command
26272 The corresponding @value{GDBN} command is @samp{tstatus}.
26274 @subheading -trace-stop
26275 @findex -trace-stop
26277 @subsubheading Synopsis
26283 Stops a tracing experiment. The result of this command has the same
26284 fields as @code{-trace-status}, except that the @samp{supported} and
26285 @samp{running} fields are not output.
26287 @subsubheading @value{GDBN} Command
26289 The corresponding @value{GDBN} command is @samp{tstop}.
26292 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26293 @node GDB/MI Symbol Query
26294 @section @sc{gdb/mi} Symbol Query Commands
26298 @subheading The @code{-symbol-info-address} Command
26299 @findex -symbol-info-address
26301 @subsubheading Synopsis
26304 -symbol-info-address @var{symbol}
26307 Describe where @var{symbol} is stored.
26309 @subsubheading @value{GDBN} Command
26311 The corresponding @value{GDBN} command is @samp{info address}.
26313 @subsubheading Example
26317 @subheading The @code{-symbol-info-file} Command
26318 @findex -symbol-info-file
26320 @subsubheading Synopsis
26326 Show the file for the symbol.
26328 @subsubheading @value{GDBN} Command
26330 There's no equivalent @value{GDBN} command. @code{gdbtk} has
26331 @samp{gdb_find_file}.
26333 @subsubheading Example
26337 @subheading The @code{-symbol-info-function} Command
26338 @findex -symbol-info-function
26340 @subsubheading Synopsis
26343 -symbol-info-function
26346 Show which function the symbol lives in.
26348 @subsubheading @value{GDBN} Command
26350 @samp{gdb_get_function} in @code{gdbtk}.
26352 @subsubheading Example
26356 @subheading The @code{-symbol-info-line} Command
26357 @findex -symbol-info-line
26359 @subsubheading Synopsis
26365 Show the core addresses of the code for a source line.
26367 @subsubheading @value{GDBN} Command
26369 The corresponding @value{GDBN} command is @samp{info line}.
26370 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
26372 @subsubheading Example
26376 @subheading The @code{-symbol-info-symbol} Command
26377 @findex -symbol-info-symbol
26379 @subsubheading Synopsis
26382 -symbol-info-symbol @var{addr}
26385 Describe what symbol is at location @var{addr}.
26387 @subsubheading @value{GDBN} Command
26389 The corresponding @value{GDBN} command is @samp{info symbol}.
26391 @subsubheading Example
26395 @subheading The @code{-symbol-list-functions} Command
26396 @findex -symbol-list-functions
26398 @subsubheading Synopsis
26401 -symbol-list-functions
26404 List the functions in the executable.
26406 @subsubheading @value{GDBN} Command
26408 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
26409 @samp{gdb_search} in @code{gdbtk}.
26411 @subsubheading Example
26416 @subheading The @code{-symbol-list-lines} Command
26417 @findex -symbol-list-lines
26419 @subsubheading Synopsis
26422 -symbol-list-lines @var{filename}
26425 Print the list of lines that contain code and their associated program
26426 addresses for the given source filename. The entries are sorted in
26427 ascending PC order.
26429 @subsubheading @value{GDBN} Command
26431 There is no corresponding @value{GDBN} command.
26433 @subsubheading Example
26436 -symbol-list-lines basics.c
26437 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
26443 @subheading The @code{-symbol-list-types} Command
26444 @findex -symbol-list-types
26446 @subsubheading Synopsis
26452 List all the type names.
26454 @subsubheading @value{GDBN} Command
26456 The corresponding commands are @samp{info types} in @value{GDBN},
26457 @samp{gdb_search} in @code{gdbtk}.
26459 @subsubheading Example
26463 @subheading The @code{-symbol-list-variables} Command
26464 @findex -symbol-list-variables
26466 @subsubheading Synopsis
26469 -symbol-list-variables
26472 List all the global and static variable names.
26474 @subsubheading @value{GDBN} Command
26476 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
26478 @subsubheading Example
26482 @subheading The @code{-symbol-locate} Command
26483 @findex -symbol-locate
26485 @subsubheading Synopsis
26491 @subsubheading @value{GDBN} Command
26493 @samp{gdb_loc} in @code{gdbtk}.
26495 @subsubheading Example
26499 @subheading The @code{-symbol-type} Command
26500 @findex -symbol-type
26502 @subsubheading Synopsis
26505 -symbol-type @var{variable}
26508 Show type of @var{variable}.
26510 @subsubheading @value{GDBN} Command
26512 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
26513 @samp{gdb_obj_variable}.
26515 @subsubheading Example
26520 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26521 @node GDB/MI File Commands
26522 @section @sc{gdb/mi} File Commands
26524 This section describes the GDB/MI commands to specify executable file names
26525 and to read in and obtain symbol table information.
26527 @subheading The @code{-file-exec-and-symbols} Command
26528 @findex -file-exec-and-symbols
26530 @subsubheading Synopsis
26533 -file-exec-and-symbols @var{file}
26536 Specify the executable file to be debugged. This file is the one from
26537 which the symbol table is also read. If no file is specified, the
26538 command clears the executable and symbol information. If breakpoints
26539 are set when using this command with no arguments, @value{GDBN} will produce
26540 error messages. Otherwise, no output is produced, except a completion
26543 @subsubheading @value{GDBN} Command
26545 The corresponding @value{GDBN} command is @samp{file}.
26547 @subsubheading Example
26551 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
26557 @subheading The @code{-file-exec-file} Command
26558 @findex -file-exec-file
26560 @subsubheading Synopsis
26563 -file-exec-file @var{file}
26566 Specify the executable file to be debugged. Unlike
26567 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
26568 from this file. If used without argument, @value{GDBN} clears the information
26569 about the executable file. No output is produced, except a completion
26572 @subsubheading @value{GDBN} Command
26574 The corresponding @value{GDBN} command is @samp{exec-file}.
26576 @subsubheading Example
26580 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
26587 @subheading The @code{-file-list-exec-sections} Command
26588 @findex -file-list-exec-sections
26590 @subsubheading Synopsis
26593 -file-list-exec-sections
26596 List the sections of the current executable file.
26598 @subsubheading @value{GDBN} Command
26600 The @value{GDBN} command @samp{info file} shows, among the rest, the same
26601 information as this command. @code{gdbtk} has a corresponding command
26602 @samp{gdb_load_info}.
26604 @subsubheading Example
26609 @subheading The @code{-file-list-exec-source-file} Command
26610 @findex -file-list-exec-source-file
26612 @subsubheading Synopsis
26615 -file-list-exec-source-file
26618 List the line number, the current source file, and the absolute path
26619 to the current source file for the current executable. The macro
26620 information field has a value of @samp{1} or @samp{0} depending on
26621 whether or not the file includes preprocessor macro information.
26623 @subsubheading @value{GDBN} Command
26625 The @value{GDBN} equivalent is @samp{info source}
26627 @subsubheading Example
26631 123-file-list-exec-source-file
26632 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
26637 @subheading The @code{-file-list-exec-source-files} Command
26638 @findex -file-list-exec-source-files
26640 @subsubheading Synopsis
26643 -file-list-exec-source-files
26646 List the source files for the current executable.
26648 It will always output the filename, but only when @value{GDBN} can find
26649 the absolute file name of a source file, will it output the fullname.
26651 @subsubheading @value{GDBN} Command
26653 The @value{GDBN} equivalent is @samp{info sources}.
26654 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
26656 @subsubheading Example
26659 -file-list-exec-source-files
26661 @{file=foo.c,fullname=/home/foo.c@},
26662 @{file=/home/bar.c,fullname=/home/bar.c@},
26663 @{file=gdb_could_not_find_fullpath.c@}]
26668 @subheading The @code{-file-list-shared-libraries} Command
26669 @findex -file-list-shared-libraries
26671 @subsubheading Synopsis
26674 -file-list-shared-libraries
26677 List the shared libraries in the program.
26679 @subsubheading @value{GDBN} Command
26681 The corresponding @value{GDBN} command is @samp{info shared}.
26683 @subsubheading Example
26687 @subheading The @code{-file-list-symbol-files} Command
26688 @findex -file-list-symbol-files
26690 @subsubheading Synopsis
26693 -file-list-symbol-files
26698 @subsubheading @value{GDBN} Command
26700 The corresponding @value{GDBN} command is @samp{info file} (part of it).
26702 @subsubheading Example
26707 @subheading The @code{-file-symbol-file} Command
26708 @findex -file-symbol-file
26710 @subsubheading Synopsis
26713 -file-symbol-file @var{file}
26716 Read symbol table info from the specified @var{file} argument. When
26717 used without arguments, clears @value{GDBN}'s symbol table info. No output is
26718 produced, except for a completion notification.
26720 @subsubheading @value{GDBN} Command
26722 The corresponding @value{GDBN} command is @samp{symbol-file}.
26724 @subsubheading Example
26728 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
26734 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26735 @node GDB/MI Memory Overlay Commands
26736 @section @sc{gdb/mi} Memory Overlay Commands
26738 The memory overlay commands are not implemented.
26740 @c @subheading -overlay-auto
26742 @c @subheading -overlay-list-mapping-state
26744 @c @subheading -overlay-list-overlays
26746 @c @subheading -overlay-map
26748 @c @subheading -overlay-off
26750 @c @subheading -overlay-on
26752 @c @subheading -overlay-unmap
26754 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26755 @node GDB/MI Signal Handling Commands
26756 @section @sc{gdb/mi} Signal Handling Commands
26758 Signal handling commands are not implemented.
26760 @c @subheading -signal-handle
26762 @c @subheading -signal-list-handle-actions
26764 @c @subheading -signal-list-signal-types
26768 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26769 @node GDB/MI Target Manipulation
26770 @section @sc{gdb/mi} Target Manipulation Commands
26773 @subheading The @code{-target-attach} Command
26774 @findex -target-attach
26776 @subsubheading Synopsis
26779 -target-attach @var{pid} | @var{gid} | @var{file}
26782 Attach to a process @var{pid} or a file @var{file} outside of
26783 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
26784 group, the id previously returned by
26785 @samp{-list-thread-groups --available} must be used.
26787 @subsubheading @value{GDBN} Command
26789 The corresponding @value{GDBN} command is @samp{attach}.
26791 @subsubheading Example
26795 =thread-created,id="1"
26796 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
26802 @subheading The @code{-target-compare-sections} Command
26803 @findex -target-compare-sections
26805 @subsubheading Synopsis
26808 -target-compare-sections [ @var{section} ]
26811 Compare data of section @var{section} on target to the exec file.
26812 Without the argument, all sections are compared.
26814 @subsubheading @value{GDBN} Command
26816 The @value{GDBN} equivalent is @samp{compare-sections}.
26818 @subsubheading Example
26823 @subheading The @code{-target-detach} Command
26824 @findex -target-detach
26826 @subsubheading Synopsis
26829 -target-detach [ @var{pid} | @var{gid} ]
26832 Detach from the remote target which normally resumes its execution.
26833 If either @var{pid} or @var{gid} is specified, detaches from either
26834 the specified process, or specified thread group. There's no output.
26836 @subsubheading @value{GDBN} Command
26838 The corresponding @value{GDBN} command is @samp{detach}.
26840 @subsubheading Example
26850 @subheading The @code{-target-disconnect} Command
26851 @findex -target-disconnect
26853 @subsubheading Synopsis
26859 Disconnect from the remote target. There's no output and the target is
26860 generally not resumed.
26862 @subsubheading @value{GDBN} Command
26864 The corresponding @value{GDBN} command is @samp{disconnect}.
26866 @subsubheading Example
26876 @subheading The @code{-target-download} Command
26877 @findex -target-download
26879 @subsubheading Synopsis
26885 Loads the executable onto the remote target.
26886 It prints out an update message every half second, which includes the fields:
26890 The name of the section.
26892 The size of what has been sent so far for that section.
26894 The size of the section.
26896 The total size of what was sent so far (the current and the previous sections).
26898 The size of the overall executable to download.
26902 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
26903 @sc{gdb/mi} Output Syntax}).
26905 In addition, it prints the name and size of the sections, as they are
26906 downloaded. These messages include the following fields:
26910 The name of the section.
26912 The size of the section.
26914 The size of the overall executable to download.
26918 At the end, a summary is printed.
26920 @subsubheading @value{GDBN} Command
26922 The corresponding @value{GDBN} command is @samp{load}.
26924 @subsubheading Example
26926 Note: each status message appears on a single line. Here the messages
26927 have been broken down so that they can fit onto a page.
26932 +download,@{section=".text",section-size="6668",total-size="9880"@}
26933 +download,@{section=".text",section-sent="512",section-size="6668",
26934 total-sent="512",total-size="9880"@}
26935 +download,@{section=".text",section-sent="1024",section-size="6668",
26936 total-sent="1024",total-size="9880"@}
26937 +download,@{section=".text",section-sent="1536",section-size="6668",
26938 total-sent="1536",total-size="9880"@}
26939 +download,@{section=".text",section-sent="2048",section-size="6668",
26940 total-sent="2048",total-size="9880"@}
26941 +download,@{section=".text",section-sent="2560",section-size="6668",
26942 total-sent="2560",total-size="9880"@}
26943 +download,@{section=".text",section-sent="3072",section-size="6668",
26944 total-sent="3072",total-size="9880"@}
26945 +download,@{section=".text",section-sent="3584",section-size="6668",
26946 total-sent="3584",total-size="9880"@}
26947 +download,@{section=".text",section-sent="4096",section-size="6668",
26948 total-sent="4096",total-size="9880"@}
26949 +download,@{section=".text",section-sent="4608",section-size="6668",
26950 total-sent="4608",total-size="9880"@}
26951 +download,@{section=".text",section-sent="5120",section-size="6668",
26952 total-sent="5120",total-size="9880"@}
26953 +download,@{section=".text",section-sent="5632",section-size="6668",
26954 total-sent="5632",total-size="9880"@}
26955 +download,@{section=".text",section-sent="6144",section-size="6668",
26956 total-sent="6144",total-size="9880"@}
26957 +download,@{section=".text",section-sent="6656",section-size="6668",
26958 total-sent="6656",total-size="9880"@}
26959 +download,@{section=".init",section-size="28",total-size="9880"@}
26960 +download,@{section=".fini",section-size="28",total-size="9880"@}
26961 +download,@{section=".data",section-size="3156",total-size="9880"@}
26962 +download,@{section=".data",section-sent="512",section-size="3156",
26963 total-sent="7236",total-size="9880"@}
26964 +download,@{section=".data",section-sent="1024",section-size="3156",
26965 total-sent="7748",total-size="9880"@}
26966 +download,@{section=".data",section-sent="1536",section-size="3156",
26967 total-sent="8260",total-size="9880"@}
26968 +download,@{section=".data",section-sent="2048",section-size="3156",
26969 total-sent="8772",total-size="9880"@}
26970 +download,@{section=".data",section-sent="2560",section-size="3156",
26971 total-sent="9284",total-size="9880"@}
26972 +download,@{section=".data",section-sent="3072",section-size="3156",
26973 total-sent="9796",total-size="9880"@}
26974 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
26981 @subheading The @code{-target-exec-status} Command
26982 @findex -target-exec-status
26984 @subsubheading Synopsis
26987 -target-exec-status
26990 Provide information on the state of the target (whether it is running or
26991 not, for instance).
26993 @subsubheading @value{GDBN} Command
26995 There's no equivalent @value{GDBN} command.
26997 @subsubheading Example
27001 @subheading The @code{-target-list-available-targets} Command
27002 @findex -target-list-available-targets
27004 @subsubheading Synopsis
27007 -target-list-available-targets
27010 List the possible targets to connect to.
27012 @subsubheading @value{GDBN} Command
27014 The corresponding @value{GDBN} command is @samp{help target}.
27016 @subsubheading Example
27020 @subheading The @code{-target-list-current-targets} Command
27021 @findex -target-list-current-targets
27023 @subsubheading Synopsis
27026 -target-list-current-targets
27029 Describe the current target.
27031 @subsubheading @value{GDBN} Command
27033 The corresponding information is printed by @samp{info file} (among
27036 @subsubheading Example
27040 @subheading The @code{-target-list-parameters} Command
27041 @findex -target-list-parameters
27043 @subsubheading Synopsis
27046 -target-list-parameters
27052 @subsubheading @value{GDBN} Command
27056 @subsubheading Example
27060 @subheading The @code{-target-select} Command
27061 @findex -target-select
27063 @subsubheading Synopsis
27066 -target-select @var{type} @var{parameters @dots{}}
27069 Connect @value{GDBN} to the remote target. This command takes two args:
27073 The type of target, for instance @samp{remote}, etc.
27074 @item @var{parameters}
27075 Device names, host names and the like. @xref{Target Commands, ,
27076 Commands for Managing Targets}, for more details.
27079 The output is a connection notification, followed by the address at
27080 which the target program is, in the following form:
27083 ^connected,addr="@var{address}",func="@var{function name}",
27084 args=[@var{arg list}]
27087 @subsubheading @value{GDBN} Command
27089 The corresponding @value{GDBN} command is @samp{target}.
27091 @subsubheading Example
27095 -target-select remote /dev/ttya
27096 ^connected,addr="0xfe00a300",func="??",args=[]
27100 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27101 @node GDB/MI File Transfer Commands
27102 @section @sc{gdb/mi} File Transfer Commands
27105 @subheading The @code{-target-file-put} Command
27106 @findex -target-file-put
27108 @subsubheading Synopsis
27111 -target-file-put @var{hostfile} @var{targetfile}
27114 Copy file @var{hostfile} from the host system (the machine running
27115 @value{GDBN}) to @var{targetfile} on the target system.
27117 @subsubheading @value{GDBN} Command
27119 The corresponding @value{GDBN} command is @samp{remote put}.
27121 @subsubheading Example
27125 -target-file-put localfile remotefile
27131 @subheading The @code{-target-file-get} Command
27132 @findex -target-file-get
27134 @subsubheading Synopsis
27137 -target-file-get @var{targetfile} @var{hostfile}
27140 Copy file @var{targetfile} from the target system to @var{hostfile}
27141 on the host system.
27143 @subsubheading @value{GDBN} Command
27145 The corresponding @value{GDBN} command is @samp{remote get}.
27147 @subsubheading Example
27151 -target-file-get remotefile localfile
27157 @subheading The @code{-target-file-delete} Command
27158 @findex -target-file-delete
27160 @subsubheading Synopsis
27163 -target-file-delete @var{targetfile}
27166 Delete @var{targetfile} from the target system.
27168 @subsubheading @value{GDBN} Command
27170 The corresponding @value{GDBN} command is @samp{remote delete}.
27172 @subsubheading Example
27176 -target-file-delete remotefile
27182 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27183 @node GDB/MI Miscellaneous Commands
27184 @section Miscellaneous @sc{gdb/mi} Commands
27186 @c @subheading -gdb-complete
27188 @subheading The @code{-gdb-exit} Command
27191 @subsubheading Synopsis
27197 Exit @value{GDBN} immediately.
27199 @subsubheading @value{GDBN} Command
27201 Approximately corresponds to @samp{quit}.
27203 @subsubheading Example
27213 @subheading The @code{-exec-abort} Command
27214 @findex -exec-abort
27216 @subsubheading Synopsis
27222 Kill the inferior running program.
27224 @subsubheading @value{GDBN} Command
27226 The corresponding @value{GDBN} command is @samp{kill}.
27228 @subsubheading Example
27233 @subheading The @code{-gdb-set} Command
27236 @subsubheading Synopsis
27242 Set an internal @value{GDBN} variable.
27243 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
27245 @subsubheading @value{GDBN} Command
27247 The corresponding @value{GDBN} command is @samp{set}.
27249 @subsubheading Example
27259 @subheading The @code{-gdb-show} Command
27262 @subsubheading Synopsis
27268 Show the current value of a @value{GDBN} variable.
27270 @subsubheading @value{GDBN} Command
27272 The corresponding @value{GDBN} command is @samp{show}.
27274 @subsubheading Example
27283 @c @subheading -gdb-source
27286 @subheading The @code{-gdb-version} Command
27287 @findex -gdb-version
27289 @subsubheading Synopsis
27295 Show version information for @value{GDBN}. Used mostly in testing.
27297 @subsubheading @value{GDBN} Command
27299 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
27300 default shows this information when you start an interactive session.
27302 @subsubheading Example
27304 @c This example modifies the actual output from GDB to avoid overfull
27310 ~Copyright 2000 Free Software Foundation, Inc.
27311 ~GDB is free software, covered by the GNU General Public License, and
27312 ~you are welcome to change it and/or distribute copies of it under
27313 ~ certain conditions.
27314 ~Type "show copying" to see the conditions.
27315 ~There is absolutely no warranty for GDB. Type "show warranty" for
27317 ~This GDB was configured as
27318 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
27323 @subheading The @code{-list-features} Command
27324 @findex -list-features
27326 Returns a list of particular features of the MI protocol that
27327 this version of gdb implements. A feature can be a command,
27328 or a new field in an output of some command, or even an
27329 important bugfix. While a frontend can sometimes detect presence
27330 of a feature at runtime, it is easier to perform detection at debugger
27333 The command returns a list of strings, with each string naming an
27334 available feature. Each returned string is just a name, it does not
27335 have any internal structure. The list of possible feature names
27341 (gdb) -list-features
27342 ^done,result=["feature1","feature2"]
27345 The current list of features is:
27348 @item frozen-varobjs
27349 Indicates presence of the @code{-var-set-frozen} command, as well
27350 as possible presense of the @code{frozen} field in the output
27351 of @code{-varobj-create}.
27352 @item pending-breakpoints
27353 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
27355 Indicates presence of Python scripting support, Python-based
27356 pretty-printing commands, and possible presence of the
27357 @samp{display_hint} field in the output of @code{-var-list-children}
27359 Indicates presence of the @code{-thread-info} command.
27363 @subheading The @code{-list-target-features} Command
27364 @findex -list-target-features
27366 Returns a list of particular features that are supported by the
27367 target. Those features affect the permitted MI commands, but
27368 unlike the features reported by the @code{-list-features} command, the
27369 features depend on which target GDB is using at the moment. Whenever
27370 a target can change, due to commands such as @code{-target-select},
27371 @code{-target-attach} or @code{-exec-run}, the list of target features
27372 may change, and the frontend should obtain it again.
27376 (gdb) -list-features
27377 ^done,result=["async"]
27380 The current list of features is:
27384 Indicates that the target is capable of asynchronous command
27385 execution, which means that @value{GDBN} will accept further commands
27386 while the target is running.
27390 @subheading The @code{-list-thread-groups} Command
27391 @findex -list-thread-groups
27393 @subheading Synopsis
27396 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
27399 Lists thread groups (@pxref{Thread groups}). When a single thread
27400 group is passed as the argument, lists the children of that group.
27401 When several thread group are passed, lists information about those
27402 thread groups. Without any parameters, lists information about all
27403 top-level thread groups.
27405 Normally, thread groups that are being debugged are reported.
27406 With the @samp{--available} option, @value{GDBN} reports thread groups
27407 available on the target.
27409 The output of this command may have either a @samp{threads} result or
27410 a @samp{groups} result. The @samp{thread} result has a list of tuples
27411 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
27412 Information}). The @samp{groups} result has a list of tuples as value,
27413 each tuple describing a thread group. If top-level groups are
27414 requested (that is, no parameter is passed), or when several groups
27415 are passed, the output always has a @samp{groups} result. The format
27416 of the @samp{group} result is described below.
27418 To reduce the number of roundtrips it's possible to list thread groups
27419 together with their children, by passing the @samp{--recurse} option
27420 and the recursion depth. Presently, only recursion depth of 1 is
27421 permitted. If this option is present, then every reported thread group
27422 will also include its children, either as @samp{group} or
27423 @samp{threads} field.
27425 In general, any combination of option and parameters is permitted, with
27426 the following caveats:
27430 When a single thread group is passed, the output will typically
27431 be the @samp{threads} result. Because threads may not contain
27432 anything, the @samp{recurse} option will be ignored.
27435 When the @samp{--available} option is passed, limited information may
27436 be available. In particular, the list of threads of a process might
27437 be inaccessible. Further, specifying specific thread groups might
27438 not give any performance advantage over listing all thread groups.
27439 The frontend should assume that @samp{-list-thread-groups --available}
27440 is always an expensive operation and cache the results.
27444 The @samp{groups} result is a list of tuples, where each tuple may
27445 have the following fields:
27449 Identifier of the thread group. This field is always present.
27450 The identifier is an opaque string; frontends should not try to
27451 convert it to an integer, even though it might look like one.
27454 The type of the thread group. At present, only @samp{process} is a
27458 The target-specific process identifier. This field is only present
27459 for thread groups of type @samp{process} and only if the process exists.
27462 The number of children this thread group has. This field may be
27463 absent for an available thread group.
27466 This field has a list of tuples as value, each tuple describing a
27467 thread. It may be present if the @samp{--recurse} option is
27468 specified, and it's actually possible to obtain the threads.
27471 This field is a list of integers, each identifying a core that one
27472 thread of the group is running on. This field may be absent if
27473 such information is not available.
27476 The name of the executable file that corresponds to this thread group.
27477 The field is only present for thread groups of type @samp{process},
27478 and only if there is a corresponding executable file.
27482 @subheading Example
27486 -list-thread-groups
27487 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
27488 -list-thread-groups 17
27489 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27490 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
27491 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27492 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
27493 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
27494 -list-thread-groups --available
27495 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
27496 -list-thread-groups --available --recurse 1
27497 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
27498 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
27499 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
27500 -list-thread-groups --available --recurse 1 17 18
27501 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
27502 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
27503 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
27507 @subheading The @code{-add-inferior} Command
27508 @findex -add-inferior
27510 @subheading Synopsis
27516 Creates a new inferior (@pxref{Inferiors and Programs}). The created
27517 inferior is not associated with any executable. Such association may
27518 be established with the @samp{-file-exec-and-symbols} command
27519 (@pxref{GDB/MI File Commands}). The command response has a single
27520 field, @samp{thread-group}, whose value is the identifier of the
27521 thread group corresponding to the new inferior.
27523 @subheading Example
27528 ^done,thread-group="i3"
27531 @subheading The @code{-interpreter-exec} Command
27532 @findex -interpreter-exec
27534 @subheading Synopsis
27537 -interpreter-exec @var{interpreter} @var{command}
27539 @anchor{-interpreter-exec}
27541 Execute the specified @var{command} in the given @var{interpreter}.
27543 @subheading @value{GDBN} Command
27545 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
27547 @subheading Example
27551 -interpreter-exec console "break main"
27552 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
27553 &"During symbol reading, bad structure-type format.\n"
27554 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
27559 @subheading The @code{-inferior-tty-set} Command
27560 @findex -inferior-tty-set
27562 @subheading Synopsis
27565 -inferior-tty-set /dev/pts/1
27568 Set terminal for future runs of the program being debugged.
27570 @subheading @value{GDBN} Command
27572 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
27574 @subheading Example
27578 -inferior-tty-set /dev/pts/1
27583 @subheading The @code{-inferior-tty-show} Command
27584 @findex -inferior-tty-show
27586 @subheading Synopsis
27592 Show terminal for future runs of program being debugged.
27594 @subheading @value{GDBN} Command
27596 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
27598 @subheading Example
27602 -inferior-tty-set /dev/pts/1
27606 ^done,inferior_tty_terminal="/dev/pts/1"
27610 @subheading The @code{-enable-timings} Command
27611 @findex -enable-timings
27613 @subheading Synopsis
27616 -enable-timings [yes | no]
27619 Toggle the printing of the wallclock, user and system times for an MI
27620 command as a field in its output. This command is to help frontend
27621 developers optimize the performance of their code. No argument is
27622 equivalent to @samp{yes}.
27624 @subheading @value{GDBN} Command
27628 @subheading Example
27636 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27637 addr="0x080484ed",func="main",file="myprog.c",
27638 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
27639 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
27647 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27648 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
27649 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
27650 fullname="/home/nickrob/myprog.c",line="73"@}
27655 @chapter @value{GDBN} Annotations
27657 This chapter describes annotations in @value{GDBN}. Annotations were
27658 designed to interface @value{GDBN} to graphical user interfaces or other
27659 similar programs which want to interact with @value{GDBN} at a
27660 relatively high level.
27662 The annotation mechanism has largely been superseded by @sc{gdb/mi}
27666 This is Edition @value{EDITION}, @value{DATE}.
27670 * Annotations Overview:: What annotations are; the general syntax.
27671 * Server Prefix:: Issuing a command without affecting user state.
27672 * Prompting:: Annotations marking @value{GDBN}'s need for input.
27673 * Errors:: Annotations for error messages.
27674 * Invalidation:: Some annotations describe things now invalid.
27675 * Annotations for Running::
27676 Whether the program is running, how it stopped, etc.
27677 * Source Annotations:: Annotations describing source code.
27680 @node Annotations Overview
27681 @section What is an Annotation?
27682 @cindex annotations
27684 Annotations start with a newline character, two @samp{control-z}
27685 characters, and the name of the annotation. If there is no additional
27686 information associated with this annotation, the name of the annotation
27687 is followed immediately by a newline. If there is additional
27688 information, the name of the annotation is followed by a space, the
27689 additional information, and a newline. The additional information
27690 cannot contain newline characters.
27692 Any output not beginning with a newline and two @samp{control-z}
27693 characters denotes literal output from @value{GDBN}. Currently there is
27694 no need for @value{GDBN} to output a newline followed by two
27695 @samp{control-z} characters, but if there was such a need, the
27696 annotations could be extended with an @samp{escape} annotation which
27697 means those three characters as output.
27699 The annotation @var{level}, which is specified using the
27700 @option{--annotate} command line option (@pxref{Mode Options}), controls
27701 how much information @value{GDBN} prints together with its prompt,
27702 values of expressions, source lines, and other types of output. Level 0
27703 is for no annotations, level 1 is for use when @value{GDBN} is run as a
27704 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
27705 for programs that control @value{GDBN}, and level 2 annotations have
27706 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
27707 Interface, annotate, GDB's Obsolete Annotations}).
27710 @kindex set annotate
27711 @item set annotate @var{level}
27712 The @value{GDBN} command @code{set annotate} sets the level of
27713 annotations to the specified @var{level}.
27715 @item show annotate
27716 @kindex show annotate
27717 Show the current annotation level.
27720 This chapter describes level 3 annotations.
27722 A simple example of starting up @value{GDBN} with annotations is:
27725 $ @kbd{gdb --annotate=3}
27727 Copyright 2003 Free Software Foundation, Inc.
27728 GDB is free software, covered by the GNU General Public License,
27729 and you are welcome to change it and/or distribute copies of it
27730 under certain conditions.
27731 Type "show copying" to see the conditions.
27732 There is absolutely no warranty for GDB. Type "show warranty"
27734 This GDB was configured as "i386-pc-linux-gnu"
27745 Here @samp{quit} is input to @value{GDBN}; the rest is output from
27746 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
27747 denotes a @samp{control-z} character) are annotations; the rest is
27748 output from @value{GDBN}.
27750 @node Server Prefix
27751 @section The Server Prefix
27752 @cindex server prefix
27754 If you prefix a command with @samp{server } then it will not affect
27755 the command history, nor will it affect @value{GDBN}'s notion of which
27756 command to repeat if @key{RET} is pressed on a line by itself. This
27757 means that commands can be run behind a user's back by a front-end in
27758 a transparent manner.
27760 The @code{server } prefix does not affect the recording of values into
27761 the value history; to print a value without recording it into the
27762 value history, use the @code{output} command instead of the
27763 @code{print} command.
27765 Using this prefix also disables confirmation requests
27766 (@pxref{confirmation requests}).
27769 @section Annotation for @value{GDBN} Input
27771 @cindex annotations for prompts
27772 When @value{GDBN} prompts for input, it annotates this fact so it is possible
27773 to know when to send output, when the output from a given command is
27776 Different kinds of input each have a different @dfn{input type}. Each
27777 input type has three annotations: a @code{pre-} annotation, which
27778 denotes the beginning of any prompt which is being output, a plain
27779 annotation, which denotes the end of the prompt, and then a @code{post-}
27780 annotation which denotes the end of any echo which may (or may not) be
27781 associated with the input. For example, the @code{prompt} input type
27782 features the following annotations:
27790 The input types are
27793 @findex pre-prompt annotation
27794 @findex prompt annotation
27795 @findex post-prompt annotation
27797 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
27799 @findex pre-commands annotation
27800 @findex commands annotation
27801 @findex post-commands annotation
27803 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
27804 command. The annotations are repeated for each command which is input.
27806 @findex pre-overload-choice annotation
27807 @findex overload-choice annotation
27808 @findex post-overload-choice annotation
27809 @item overload-choice
27810 When @value{GDBN} wants the user to select between various overloaded functions.
27812 @findex pre-query annotation
27813 @findex query annotation
27814 @findex post-query annotation
27816 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
27818 @findex pre-prompt-for-continue annotation
27819 @findex prompt-for-continue annotation
27820 @findex post-prompt-for-continue annotation
27821 @item prompt-for-continue
27822 When @value{GDBN} is asking the user to press return to continue. Note: Don't
27823 expect this to work well; instead use @code{set height 0} to disable
27824 prompting. This is because the counting of lines is buggy in the
27825 presence of annotations.
27830 @cindex annotations for errors, warnings and interrupts
27832 @findex quit annotation
27837 This annotation occurs right before @value{GDBN} responds to an interrupt.
27839 @findex error annotation
27844 This annotation occurs right before @value{GDBN} responds to an error.
27846 Quit and error annotations indicate that any annotations which @value{GDBN} was
27847 in the middle of may end abruptly. For example, if a
27848 @code{value-history-begin} annotation is followed by a @code{error}, one
27849 cannot expect to receive the matching @code{value-history-end}. One
27850 cannot expect not to receive it either, however; an error annotation
27851 does not necessarily mean that @value{GDBN} is immediately returning all the way
27854 @findex error-begin annotation
27855 A quit or error annotation may be preceded by
27861 Any output between that and the quit or error annotation is the error
27864 Warning messages are not yet annotated.
27865 @c If we want to change that, need to fix warning(), type_error(),
27866 @c range_error(), and possibly other places.
27869 @section Invalidation Notices
27871 @cindex annotations for invalidation messages
27872 The following annotations say that certain pieces of state may have
27876 @findex frames-invalid annotation
27877 @item ^Z^Zframes-invalid
27879 The frames (for example, output from the @code{backtrace} command) may
27882 @findex breakpoints-invalid annotation
27883 @item ^Z^Zbreakpoints-invalid
27885 The breakpoints may have changed. For example, the user just added or
27886 deleted a breakpoint.
27889 @node Annotations for Running
27890 @section Running the Program
27891 @cindex annotations for running programs
27893 @findex starting annotation
27894 @findex stopping annotation
27895 When the program starts executing due to a @value{GDBN} command such as
27896 @code{step} or @code{continue},
27902 is output. When the program stops,
27908 is output. Before the @code{stopped} annotation, a variety of
27909 annotations describe how the program stopped.
27912 @findex exited annotation
27913 @item ^Z^Zexited @var{exit-status}
27914 The program exited, and @var{exit-status} is the exit status (zero for
27915 successful exit, otherwise nonzero).
27917 @findex signalled annotation
27918 @findex signal-name annotation
27919 @findex signal-name-end annotation
27920 @findex signal-string annotation
27921 @findex signal-string-end annotation
27922 @item ^Z^Zsignalled
27923 The program exited with a signal. After the @code{^Z^Zsignalled}, the
27924 annotation continues:
27930 ^Z^Zsignal-name-end
27934 ^Z^Zsignal-string-end
27939 where @var{name} is the name of the signal, such as @code{SIGILL} or
27940 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
27941 as @code{Illegal Instruction} or @code{Segmentation fault}.
27942 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
27943 user's benefit and have no particular format.
27945 @findex signal annotation
27947 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
27948 just saying that the program received the signal, not that it was
27949 terminated with it.
27951 @findex breakpoint annotation
27952 @item ^Z^Zbreakpoint @var{number}
27953 The program hit breakpoint number @var{number}.
27955 @findex watchpoint annotation
27956 @item ^Z^Zwatchpoint @var{number}
27957 The program hit watchpoint number @var{number}.
27960 @node Source Annotations
27961 @section Displaying Source
27962 @cindex annotations for source display
27964 @findex source annotation
27965 The following annotation is used instead of displaying source code:
27968 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
27971 where @var{filename} is an absolute file name indicating which source
27972 file, @var{line} is the line number within that file (where 1 is the
27973 first line in the file), @var{character} is the character position
27974 within the file (where 0 is the first character in the file) (for most
27975 debug formats this will necessarily point to the beginning of a line),
27976 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
27977 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
27978 @var{addr} is the address in the target program associated with the
27979 source which is being displayed. @var{addr} is in the form @samp{0x}
27980 followed by one or more lowercase hex digits (note that this does not
27981 depend on the language).
27983 @node JIT Interface
27984 @chapter JIT Compilation Interface
27985 @cindex just-in-time compilation
27986 @cindex JIT compilation interface
27988 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
27989 interface. A JIT compiler is a program or library that generates native
27990 executable code at runtime and executes it, usually in order to achieve good
27991 performance while maintaining platform independence.
27993 Programs that use JIT compilation are normally difficult to debug because
27994 portions of their code are generated at runtime, instead of being loaded from
27995 object files, which is where @value{GDBN} normally finds the program's symbols
27996 and debug information. In order to debug programs that use JIT compilation,
27997 @value{GDBN} has an interface that allows the program to register in-memory
27998 symbol files with @value{GDBN} at runtime.
28000 If you are using @value{GDBN} to debug a program that uses this interface, then
28001 it should work transparently so long as you have not stripped the binary. If
28002 you are developing a JIT compiler, then the interface is documented in the rest
28003 of this chapter. At this time, the only known client of this interface is the
28006 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
28007 JIT compiler communicates with @value{GDBN} by writing data into a global
28008 variable and calling a fuction at a well-known symbol. When @value{GDBN}
28009 attaches, it reads a linked list of symbol files from the global variable to
28010 find existing code, and puts a breakpoint in the function so that it can find
28011 out about additional code.
28014 * Declarations:: Relevant C struct declarations
28015 * Registering Code:: Steps to register code
28016 * Unregistering Code:: Steps to unregister code
28020 @section JIT Declarations
28022 These are the relevant struct declarations that a C program should include to
28023 implement the interface:
28033 struct jit_code_entry
28035 struct jit_code_entry *next_entry;
28036 struct jit_code_entry *prev_entry;
28037 const char *symfile_addr;
28038 uint64_t symfile_size;
28041 struct jit_descriptor
28044 /* This type should be jit_actions_t, but we use uint32_t
28045 to be explicit about the bitwidth. */
28046 uint32_t action_flag;
28047 struct jit_code_entry *relevant_entry;
28048 struct jit_code_entry *first_entry;
28051 /* GDB puts a breakpoint in this function. */
28052 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
28054 /* Make sure to specify the version statically, because the
28055 debugger may check the version before we can set it. */
28056 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
28059 If the JIT is multi-threaded, then it is important that the JIT synchronize any
28060 modifications to this global data properly, which can easily be done by putting
28061 a global mutex around modifications to these structures.
28063 @node Registering Code
28064 @section Registering Code
28066 To register code with @value{GDBN}, the JIT should follow this protocol:
28070 Generate an object file in memory with symbols and other desired debug
28071 information. The file must include the virtual addresses of the sections.
28074 Create a code entry for the file, which gives the start and size of the symbol
28078 Add it to the linked list in the JIT descriptor.
28081 Point the relevant_entry field of the descriptor at the entry.
28084 Set @code{action_flag} to @code{JIT_REGISTER} and call
28085 @code{__jit_debug_register_code}.
28088 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
28089 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
28090 new code. However, the linked list must still be maintained in order to allow
28091 @value{GDBN} to attach to a running process and still find the symbol files.
28093 @node Unregistering Code
28094 @section Unregistering Code
28096 If code is freed, then the JIT should use the following protocol:
28100 Remove the code entry corresponding to the code from the linked list.
28103 Point the @code{relevant_entry} field of the descriptor at the code entry.
28106 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
28107 @code{__jit_debug_register_code}.
28110 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
28111 and the JIT will leak the memory used for the associated symbol files.
28114 @chapter Reporting Bugs in @value{GDBN}
28115 @cindex bugs in @value{GDBN}
28116 @cindex reporting bugs in @value{GDBN}
28118 Your bug reports play an essential role in making @value{GDBN} reliable.
28120 Reporting a bug may help you by bringing a solution to your problem, or it
28121 may not. But in any case the principal function of a bug report is to help
28122 the entire community by making the next version of @value{GDBN} work better. Bug
28123 reports are your contribution to the maintenance of @value{GDBN}.
28125 In order for a bug report to serve its purpose, you must include the
28126 information that enables us to fix the bug.
28129 * Bug Criteria:: Have you found a bug?
28130 * Bug Reporting:: How to report bugs
28134 @section Have You Found a Bug?
28135 @cindex bug criteria
28137 If you are not sure whether you have found a bug, here are some guidelines:
28140 @cindex fatal signal
28141 @cindex debugger crash
28142 @cindex crash of debugger
28144 If the debugger gets a fatal signal, for any input whatever, that is a
28145 @value{GDBN} bug. Reliable debuggers never crash.
28147 @cindex error on valid input
28149 If @value{GDBN} produces an error message for valid input, that is a
28150 bug. (Note that if you're cross debugging, the problem may also be
28151 somewhere in the connection to the target.)
28153 @cindex invalid input
28155 If @value{GDBN} does not produce an error message for invalid input,
28156 that is a bug. However, you should note that your idea of
28157 ``invalid input'' might be our idea of ``an extension'' or ``support
28158 for traditional practice''.
28161 If you are an experienced user of debugging tools, your suggestions
28162 for improvement of @value{GDBN} are welcome in any case.
28165 @node Bug Reporting
28166 @section How to Report Bugs
28167 @cindex bug reports
28168 @cindex @value{GDBN} bugs, reporting
28170 A number of companies and individuals offer support for @sc{gnu} products.
28171 If you obtained @value{GDBN} from a support organization, we recommend you
28172 contact that organization first.
28174 You can find contact information for many support companies and
28175 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
28177 @c should add a web page ref...
28180 @ifset BUGURL_DEFAULT
28181 In any event, we also recommend that you submit bug reports for
28182 @value{GDBN}. The preferred method is to submit them directly using
28183 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
28184 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
28187 @strong{Do not send bug reports to @samp{info-gdb}, or to
28188 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
28189 not want to receive bug reports. Those that do have arranged to receive
28192 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
28193 serves as a repeater. The mailing list and the newsgroup carry exactly
28194 the same messages. Often people think of posting bug reports to the
28195 newsgroup instead of mailing them. This appears to work, but it has one
28196 problem which can be crucial: a newsgroup posting often lacks a mail
28197 path back to the sender. Thus, if we need to ask for more information,
28198 we may be unable to reach you. For this reason, it is better to send
28199 bug reports to the mailing list.
28201 @ifclear BUGURL_DEFAULT
28202 In any event, we also recommend that you submit bug reports for
28203 @value{GDBN} to @value{BUGURL}.
28207 The fundamental principle of reporting bugs usefully is this:
28208 @strong{report all the facts}. If you are not sure whether to state a
28209 fact or leave it out, state it!
28211 Often people omit facts because they think they know what causes the
28212 problem and assume that some details do not matter. Thus, you might
28213 assume that the name of the variable you use in an example does not matter.
28214 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
28215 stray memory reference which happens to fetch from the location where that
28216 name is stored in memory; perhaps, if the name were different, the contents
28217 of that location would fool the debugger into doing the right thing despite
28218 the bug. Play it safe and give a specific, complete example. That is the
28219 easiest thing for you to do, and the most helpful.
28221 Keep in mind that the purpose of a bug report is to enable us to fix the
28222 bug. It may be that the bug has been reported previously, but neither
28223 you nor we can know that unless your bug report is complete and
28226 Sometimes people give a few sketchy facts and ask, ``Does this ring a
28227 bell?'' Those bug reports are useless, and we urge everyone to
28228 @emph{refuse to respond to them} except to chide the sender to report
28231 To enable us to fix the bug, you should include all these things:
28235 The version of @value{GDBN}. @value{GDBN} announces it if you start
28236 with no arguments; you can also print it at any time using @code{show
28239 Without this, we will not know whether there is any point in looking for
28240 the bug in the current version of @value{GDBN}.
28243 The type of machine you are using, and the operating system name and
28247 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
28248 ``@value{GCC}--2.8.1''.
28251 What compiler (and its version) was used to compile the program you are
28252 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
28253 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
28254 to get this information; for other compilers, see the documentation for
28258 The command arguments you gave the compiler to compile your example and
28259 observe the bug. For example, did you use @samp{-O}? To guarantee
28260 you will not omit something important, list them all. A copy of the
28261 Makefile (or the output from make) is sufficient.
28263 If we were to try to guess the arguments, we would probably guess wrong
28264 and then we might not encounter the bug.
28267 A complete input script, and all necessary source files, that will
28271 A description of what behavior you observe that you believe is
28272 incorrect. For example, ``It gets a fatal signal.''
28274 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
28275 will certainly notice it. But if the bug is incorrect output, we might
28276 not notice unless it is glaringly wrong. You might as well not give us
28277 a chance to make a mistake.
28279 Even if the problem you experience is a fatal signal, you should still
28280 say so explicitly. Suppose something strange is going on, such as, your
28281 copy of @value{GDBN} is out of synch, or you have encountered a bug in
28282 the C library on your system. (This has happened!) Your copy might
28283 crash and ours would not. If you told us to expect a crash, then when
28284 ours fails to crash, we would know that the bug was not happening for
28285 us. If you had not told us to expect a crash, then we would not be able
28286 to draw any conclusion from our observations.
28289 @cindex recording a session script
28290 To collect all this information, you can use a session recording program
28291 such as @command{script}, which is available on many Unix systems.
28292 Just run your @value{GDBN} session inside @command{script} and then
28293 include the @file{typescript} file with your bug report.
28295 Another way to record a @value{GDBN} session is to run @value{GDBN}
28296 inside Emacs and then save the entire buffer to a file.
28299 If you wish to suggest changes to the @value{GDBN} source, send us context
28300 diffs. If you even discuss something in the @value{GDBN} source, refer to
28301 it by context, not by line number.
28303 The line numbers in our development sources will not match those in your
28304 sources. Your line numbers would convey no useful information to us.
28308 Here are some things that are not necessary:
28312 A description of the envelope of the bug.
28314 Often people who encounter a bug spend a lot of time investigating
28315 which changes to the input file will make the bug go away and which
28316 changes will not affect it.
28318 This is often time consuming and not very useful, because the way we
28319 will find the bug is by running a single example under the debugger
28320 with breakpoints, not by pure deduction from a series of examples.
28321 We recommend that you save your time for something else.
28323 Of course, if you can find a simpler example to report @emph{instead}
28324 of the original one, that is a convenience for us. Errors in the
28325 output will be easier to spot, running under the debugger will take
28326 less time, and so on.
28328 However, simplification is not vital; if you do not want to do this,
28329 report the bug anyway and send us the entire test case you used.
28332 A patch for the bug.
28334 A patch for the bug does help us if it is a good one. But do not omit
28335 the necessary information, such as the test case, on the assumption that
28336 a patch is all we need. We might see problems with your patch and decide
28337 to fix the problem another way, or we might not understand it at all.
28339 Sometimes with a program as complicated as @value{GDBN} it is very hard to
28340 construct an example that will make the program follow a certain path
28341 through the code. If you do not send us the example, we will not be able
28342 to construct one, so we will not be able to verify that the bug is fixed.
28344 And if we cannot understand what bug you are trying to fix, or why your
28345 patch should be an improvement, we will not install it. A test case will
28346 help us to understand.
28349 A guess about what the bug is or what it depends on.
28351 Such guesses are usually wrong. Even we cannot guess right about such
28352 things without first using the debugger to find the facts.
28355 @c The readline documentation is distributed with the readline code
28356 @c and consists of the two following files:
28358 @c inc-hist.texinfo
28359 @c Use -I with makeinfo to point to the appropriate directory,
28360 @c environment var TEXINPUTS with TeX.
28361 @include rluser.texi
28362 @include inc-hist.texinfo
28365 @node Formatting Documentation
28366 @appendix Formatting Documentation
28368 @cindex @value{GDBN} reference card
28369 @cindex reference card
28370 The @value{GDBN} 4 release includes an already-formatted reference card, ready
28371 for printing with PostScript or Ghostscript, in the @file{gdb}
28372 subdirectory of the main source directory@footnote{In
28373 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
28374 release.}. If you can use PostScript or Ghostscript with your printer,
28375 you can print the reference card immediately with @file{refcard.ps}.
28377 The release also includes the source for the reference card. You
28378 can format it, using @TeX{}, by typing:
28384 The @value{GDBN} reference card is designed to print in @dfn{landscape}
28385 mode on US ``letter'' size paper;
28386 that is, on a sheet 11 inches wide by 8.5 inches
28387 high. You will need to specify this form of printing as an option to
28388 your @sc{dvi} output program.
28390 @cindex documentation
28392 All the documentation for @value{GDBN} comes as part of the machine-readable
28393 distribution. The documentation is written in Texinfo format, which is
28394 a documentation system that uses a single source file to produce both
28395 on-line information and a printed manual. You can use one of the Info
28396 formatting commands to create the on-line version of the documentation
28397 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
28399 @value{GDBN} includes an already formatted copy of the on-line Info
28400 version of this manual in the @file{gdb} subdirectory. The main Info
28401 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
28402 subordinate files matching @samp{gdb.info*} in the same directory. If
28403 necessary, you can print out these files, or read them with any editor;
28404 but they are easier to read using the @code{info} subsystem in @sc{gnu}
28405 Emacs or the standalone @code{info} program, available as part of the
28406 @sc{gnu} Texinfo distribution.
28408 If you want to format these Info files yourself, you need one of the
28409 Info formatting programs, such as @code{texinfo-format-buffer} or
28412 If you have @code{makeinfo} installed, and are in the top level
28413 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
28414 version @value{GDBVN}), you can make the Info file by typing:
28421 If you want to typeset and print copies of this manual, you need @TeX{},
28422 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
28423 Texinfo definitions file.
28425 @TeX{} is a typesetting program; it does not print files directly, but
28426 produces output files called @sc{dvi} files. To print a typeset
28427 document, you need a program to print @sc{dvi} files. If your system
28428 has @TeX{} installed, chances are it has such a program. The precise
28429 command to use depends on your system; @kbd{lpr -d} is common; another
28430 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
28431 require a file name without any extension or a @samp{.dvi} extension.
28433 @TeX{} also requires a macro definitions file called
28434 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
28435 written in Texinfo format. On its own, @TeX{} cannot either read or
28436 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
28437 and is located in the @file{gdb-@var{version-number}/texinfo}
28440 If you have @TeX{} and a @sc{dvi} printer program installed, you can
28441 typeset and print this manual. First switch to the @file{gdb}
28442 subdirectory of the main source directory (for example, to
28443 @file{gdb-@value{GDBVN}/gdb}) and type:
28449 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
28451 @node Installing GDB
28452 @appendix Installing @value{GDBN}
28453 @cindex installation
28456 * Requirements:: Requirements for building @value{GDBN}
28457 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
28458 * Separate Objdir:: Compiling @value{GDBN} in another directory
28459 * Config Names:: Specifying names for hosts and targets
28460 * Configure Options:: Summary of options for configure
28461 * System-wide configuration:: Having a system-wide init file
28465 @section Requirements for Building @value{GDBN}
28466 @cindex building @value{GDBN}, requirements for
28468 Building @value{GDBN} requires various tools and packages to be available.
28469 Other packages will be used only if they are found.
28471 @heading Tools/Packages Necessary for Building @value{GDBN}
28473 @item ISO C90 compiler
28474 @value{GDBN} is written in ISO C90. It should be buildable with any
28475 working C90 compiler, e.g.@: GCC.
28479 @heading Tools/Packages Optional for Building @value{GDBN}
28483 @value{GDBN} can use the Expat XML parsing library. This library may be
28484 included with your operating system distribution; if it is not, you
28485 can get the latest version from @url{http://expat.sourceforge.net}.
28486 The @file{configure} script will search for this library in several
28487 standard locations; if it is installed in an unusual path, you can
28488 use the @option{--with-libexpat-prefix} option to specify its location.
28494 Remote protocol memory maps (@pxref{Memory Map Format})
28496 Target descriptions (@pxref{Target Descriptions})
28498 Remote shared library lists (@pxref{Library List Format})
28500 MS-Windows shared libraries (@pxref{Shared Libraries})
28504 @cindex compressed debug sections
28505 @value{GDBN} will use the @samp{zlib} library, if available, to read
28506 compressed debug sections. Some linkers, such as GNU gold, are capable
28507 of producing binaries with compressed debug sections. If @value{GDBN}
28508 is compiled with @samp{zlib}, it will be able to read the debug
28509 information in such binaries.
28511 The @samp{zlib} library is likely included with your operating system
28512 distribution; if it is not, you can get the latest version from
28513 @url{http://zlib.net}.
28516 @value{GDBN}'s features related to character sets (@pxref{Character
28517 Sets}) require a functioning @code{iconv} implementation. If you are
28518 on a GNU system, then this is provided by the GNU C Library. Some
28519 other systems also provide a working @code{iconv}.
28521 On systems with @code{iconv}, you can install GNU Libiconv. If you
28522 have previously installed Libiconv, you can use the
28523 @option{--with-libiconv-prefix} option to configure.
28525 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
28526 arrange to build Libiconv if a directory named @file{libiconv} appears
28527 in the top-most source directory. If Libiconv is built this way, and
28528 if the operating system does not provide a suitable @code{iconv}
28529 implementation, then the just-built library will automatically be used
28530 by @value{GDBN}. One easy way to set this up is to download GNU
28531 Libiconv, unpack it, and then rename the directory holding the
28532 Libiconv source code to @samp{libiconv}.
28535 @node Running Configure
28536 @section Invoking the @value{GDBN} @file{configure} Script
28537 @cindex configuring @value{GDBN}
28538 @value{GDBN} comes with a @file{configure} script that automates the process
28539 of preparing @value{GDBN} for installation; you can then use @code{make} to
28540 build the @code{gdb} program.
28542 @c irrelevant in info file; it's as current as the code it lives with.
28543 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
28544 look at the @file{README} file in the sources; we may have improved the
28545 installation procedures since publishing this manual.}
28548 The @value{GDBN} distribution includes all the source code you need for
28549 @value{GDBN} in a single directory, whose name is usually composed by
28550 appending the version number to @samp{gdb}.
28552 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
28553 @file{gdb-@value{GDBVN}} directory. That directory contains:
28556 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
28557 script for configuring @value{GDBN} and all its supporting libraries
28559 @item gdb-@value{GDBVN}/gdb
28560 the source specific to @value{GDBN} itself
28562 @item gdb-@value{GDBVN}/bfd
28563 source for the Binary File Descriptor library
28565 @item gdb-@value{GDBVN}/include
28566 @sc{gnu} include files
28568 @item gdb-@value{GDBVN}/libiberty
28569 source for the @samp{-liberty} free software library
28571 @item gdb-@value{GDBVN}/opcodes
28572 source for the library of opcode tables and disassemblers
28574 @item gdb-@value{GDBVN}/readline
28575 source for the @sc{gnu} command-line interface
28577 @item gdb-@value{GDBVN}/glob
28578 source for the @sc{gnu} filename pattern-matching subroutine
28580 @item gdb-@value{GDBVN}/mmalloc
28581 source for the @sc{gnu} memory-mapped malloc package
28584 The simplest way to configure and build @value{GDBN} is to run @file{configure}
28585 from the @file{gdb-@var{version-number}} source directory, which in
28586 this example is the @file{gdb-@value{GDBVN}} directory.
28588 First switch to the @file{gdb-@var{version-number}} source directory
28589 if you are not already in it; then run @file{configure}. Pass the
28590 identifier for the platform on which @value{GDBN} will run as an
28596 cd gdb-@value{GDBVN}
28597 ./configure @var{host}
28602 where @var{host} is an identifier such as @samp{sun4} or
28603 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
28604 (You can often leave off @var{host}; @file{configure} tries to guess the
28605 correct value by examining your system.)
28607 Running @samp{configure @var{host}} and then running @code{make} builds the
28608 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
28609 libraries, then @code{gdb} itself. The configured source files, and the
28610 binaries, are left in the corresponding source directories.
28613 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
28614 system does not recognize this automatically when you run a different
28615 shell, you may need to run @code{sh} on it explicitly:
28618 sh configure @var{host}
28621 If you run @file{configure} from a directory that contains source
28622 directories for multiple libraries or programs, such as the
28623 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
28625 creates configuration files for every directory level underneath (unless
28626 you tell it not to, with the @samp{--norecursion} option).
28628 You should run the @file{configure} script from the top directory in the
28629 source tree, the @file{gdb-@var{version-number}} directory. If you run
28630 @file{configure} from one of the subdirectories, you will configure only
28631 that subdirectory. That is usually not what you want. In particular,
28632 if you run the first @file{configure} from the @file{gdb} subdirectory
28633 of the @file{gdb-@var{version-number}} directory, you will omit the
28634 configuration of @file{bfd}, @file{readline}, and other sibling
28635 directories of the @file{gdb} subdirectory. This leads to build errors
28636 about missing include files such as @file{bfd/bfd.h}.
28638 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
28639 However, you should make sure that the shell on your path (named by
28640 the @samp{SHELL} environment variable) is publicly readable. Remember
28641 that @value{GDBN} uses the shell to start your program---some systems refuse to
28642 let @value{GDBN} debug child processes whose programs are not readable.
28644 @node Separate Objdir
28645 @section Compiling @value{GDBN} in Another Directory
28647 If you want to run @value{GDBN} versions for several host or target machines,
28648 you need a different @code{gdb} compiled for each combination of
28649 host and target. @file{configure} is designed to make this easy by
28650 allowing you to generate each configuration in a separate subdirectory,
28651 rather than in the source directory. If your @code{make} program
28652 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
28653 @code{make} in each of these directories builds the @code{gdb}
28654 program specified there.
28656 To build @code{gdb} in a separate directory, run @file{configure}
28657 with the @samp{--srcdir} option to specify where to find the source.
28658 (You also need to specify a path to find @file{configure}
28659 itself from your working directory. If the path to @file{configure}
28660 would be the same as the argument to @samp{--srcdir}, you can leave out
28661 the @samp{--srcdir} option; it is assumed.)
28663 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
28664 separate directory for a Sun 4 like this:
28668 cd gdb-@value{GDBVN}
28671 ../gdb-@value{GDBVN}/configure sun4
28676 When @file{configure} builds a configuration using a remote source
28677 directory, it creates a tree for the binaries with the same structure
28678 (and using the same names) as the tree under the source directory. In
28679 the example, you'd find the Sun 4 library @file{libiberty.a} in the
28680 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
28681 @file{gdb-sun4/gdb}.
28683 Make sure that your path to the @file{configure} script has just one
28684 instance of @file{gdb} in it. If your path to @file{configure} looks
28685 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
28686 one subdirectory of @value{GDBN}, not the whole package. This leads to
28687 build errors about missing include files such as @file{bfd/bfd.h}.
28689 One popular reason to build several @value{GDBN} configurations in separate
28690 directories is to configure @value{GDBN} for cross-compiling (where
28691 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
28692 programs that run on another machine---the @dfn{target}).
28693 You specify a cross-debugging target by
28694 giving the @samp{--target=@var{target}} option to @file{configure}.
28696 When you run @code{make} to build a program or library, you must run
28697 it in a configured directory---whatever directory you were in when you
28698 called @file{configure} (or one of its subdirectories).
28700 The @code{Makefile} that @file{configure} generates in each source
28701 directory also runs recursively. If you type @code{make} in a source
28702 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
28703 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
28704 will build all the required libraries, and then build GDB.
28706 When you have multiple hosts or targets configured in separate
28707 directories, you can run @code{make} on them in parallel (for example,
28708 if they are NFS-mounted on each of the hosts); they will not interfere
28712 @section Specifying Names for Hosts and Targets
28714 The specifications used for hosts and targets in the @file{configure}
28715 script are based on a three-part naming scheme, but some short predefined
28716 aliases are also supported. The full naming scheme encodes three pieces
28717 of information in the following pattern:
28720 @var{architecture}-@var{vendor}-@var{os}
28723 For example, you can use the alias @code{sun4} as a @var{host} argument,
28724 or as the value for @var{target} in a @code{--target=@var{target}}
28725 option. The equivalent full name is @samp{sparc-sun-sunos4}.
28727 The @file{configure} script accompanying @value{GDBN} does not provide
28728 any query facility to list all supported host and target names or
28729 aliases. @file{configure} calls the Bourne shell script
28730 @code{config.sub} to map abbreviations to full names; you can read the
28731 script, if you wish, or you can use it to test your guesses on
28732 abbreviations---for example:
28735 % sh config.sub i386-linux
28737 % sh config.sub alpha-linux
28738 alpha-unknown-linux-gnu
28739 % sh config.sub hp9k700
28741 % sh config.sub sun4
28742 sparc-sun-sunos4.1.1
28743 % sh config.sub sun3
28744 m68k-sun-sunos4.1.1
28745 % sh config.sub i986v
28746 Invalid configuration `i986v': machine `i986v' not recognized
28750 @code{config.sub} is also distributed in the @value{GDBN} source
28751 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
28753 @node Configure Options
28754 @section @file{configure} Options
28756 Here is a summary of the @file{configure} options and arguments that
28757 are most often useful for building @value{GDBN}. @file{configure} also has
28758 several other options not listed here. @inforef{What Configure
28759 Does,,configure.info}, for a full explanation of @file{configure}.
28762 configure @r{[}--help@r{]}
28763 @r{[}--prefix=@var{dir}@r{]}
28764 @r{[}--exec-prefix=@var{dir}@r{]}
28765 @r{[}--srcdir=@var{dirname}@r{]}
28766 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
28767 @r{[}--target=@var{target}@r{]}
28772 You may introduce options with a single @samp{-} rather than
28773 @samp{--} if you prefer; but you may abbreviate option names if you use
28778 Display a quick summary of how to invoke @file{configure}.
28780 @item --prefix=@var{dir}
28781 Configure the source to install programs and files under directory
28784 @item --exec-prefix=@var{dir}
28785 Configure the source to install programs under directory
28788 @c avoid splitting the warning from the explanation:
28790 @item --srcdir=@var{dirname}
28791 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
28792 @code{make} that implements the @code{VPATH} feature.}@*
28793 Use this option to make configurations in directories separate from the
28794 @value{GDBN} source directories. Among other things, you can use this to
28795 build (or maintain) several configurations simultaneously, in separate
28796 directories. @file{configure} writes configuration-specific files in
28797 the current directory, but arranges for them to use the source in the
28798 directory @var{dirname}. @file{configure} creates directories under
28799 the working directory in parallel to the source directories below
28802 @item --norecursion
28803 Configure only the directory level where @file{configure} is executed; do not
28804 propagate configuration to subdirectories.
28806 @item --target=@var{target}
28807 Configure @value{GDBN} for cross-debugging programs running on the specified
28808 @var{target}. Without this option, @value{GDBN} is configured to debug
28809 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
28811 There is no convenient way to generate a list of all available targets.
28813 @item @var{host} @dots{}
28814 Configure @value{GDBN} to run on the specified @var{host}.
28816 There is no convenient way to generate a list of all available hosts.
28819 There are many other options available as well, but they are generally
28820 needed for special purposes only.
28822 @node System-wide configuration
28823 @section System-wide configuration and settings
28824 @cindex system-wide init file
28826 @value{GDBN} can be configured to have a system-wide init file;
28827 this file will be read and executed at startup (@pxref{Startup, , What
28828 @value{GDBN} does during startup}).
28830 Here is the corresponding configure option:
28833 @item --with-system-gdbinit=@var{file}
28834 Specify that the default location of the system-wide init file is
28838 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
28839 it may be subject to relocation. Two possible cases:
28843 If the default location of this init file contains @file{$prefix},
28844 it will be subject to relocation. Suppose that the configure options
28845 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
28846 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
28847 init file is looked for as @file{$install/etc/gdbinit} instead of
28848 @file{$prefix/etc/gdbinit}.
28851 By contrast, if the default location does not contain the prefix,
28852 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
28853 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
28854 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
28855 wherever @value{GDBN} is installed.
28858 @node Maintenance Commands
28859 @appendix Maintenance Commands
28860 @cindex maintenance commands
28861 @cindex internal commands
28863 In addition to commands intended for @value{GDBN} users, @value{GDBN}
28864 includes a number of commands intended for @value{GDBN} developers,
28865 that are not documented elsewhere in this manual. These commands are
28866 provided here for reference. (For commands that turn on debugging
28867 messages, see @ref{Debugging Output}.)
28870 @kindex maint agent
28871 @kindex maint agent-eval
28872 @item maint agent @var{expression}
28873 @itemx maint agent-eval @var{expression}
28874 Translate the given @var{expression} into remote agent bytecodes.
28875 This command is useful for debugging the Agent Expression mechanism
28876 (@pxref{Agent Expressions}). The @samp{agent} version produces an
28877 expression useful for data collection, such as by tracepoints, while
28878 @samp{maint agent-eval} produces an expression that evaluates directly
28879 to a result. For instance, a collection expression for @code{globa +
28880 globb} will include bytecodes to record four bytes of memory at each
28881 of the addresses of @code{globa} and @code{globb}, while discarding
28882 the result of the addition, while an evaluation expression will do the
28883 addition and return the sum.
28885 @kindex maint info breakpoints
28886 @item @anchor{maint info breakpoints}maint info breakpoints
28887 Using the same format as @samp{info breakpoints}, display both the
28888 breakpoints you've set explicitly, and those @value{GDBN} is using for
28889 internal purposes. Internal breakpoints are shown with negative
28890 breakpoint numbers. The type column identifies what kind of breakpoint
28895 Normal, explicitly set breakpoint.
28898 Normal, explicitly set watchpoint.
28901 Internal breakpoint, used to handle correctly stepping through
28902 @code{longjmp} calls.
28904 @item longjmp resume
28905 Internal breakpoint at the target of a @code{longjmp}.
28908 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
28911 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
28914 Shared library events.
28918 @kindex set displaced-stepping
28919 @kindex show displaced-stepping
28920 @cindex displaced stepping support
28921 @cindex out-of-line single-stepping
28922 @item set displaced-stepping
28923 @itemx show displaced-stepping
28924 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
28925 if the target supports it. Displaced stepping is a way to single-step
28926 over breakpoints without removing them from the inferior, by executing
28927 an out-of-line copy of the instruction that was originally at the
28928 breakpoint location. It is also known as out-of-line single-stepping.
28931 @item set displaced-stepping on
28932 If the target architecture supports it, @value{GDBN} will use
28933 displaced stepping to step over breakpoints.
28935 @item set displaced-stepping off
28936 @value{GDBN} will not use displaced stepping to step over breakpoints,
28937 even if such is supported by the target architecture.
28939 @cindex non-stop mode, and @samp{set displaced-stepping}
28940 @item set displaced-stepping auto
28941 This is the default mode. @value{GDBN} will use displaced stepping
28942 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
28943 architecture supports displaced stepping.
28946 @kindex maint check-symtabs
28947 @item maint check-symtabs
28948 Check the consistency of psymtabs and symtabs.
28950 @kindex maint cplus first_component
28951 @item maint cplus first_component @var{name}
28952 Print the first C@t{++} class/namespace component of @var{name}.
28954 @kindex maint cplus namespace
28955 @item maint cplus namespace
28956 Print the list of possible C@t{++} namespaces.
28958 @kindex maint demangle
28959 @item maint demangle @var{name}
28960 Demangle a C@t{++} or Objective-C mangled @var{name}.
28962 @kindex maint deprecate
28963 @kindex maint undeprecate
28964 @cindex deprecated commands
28965 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
28966 @itemx maint undeprecate @var{command}
28967 Deprecate or undeprecate the named @var{command}. Deprecated commands
28968 cause @value{GDBN} to issue a warning when you use them. The optional
28969 argument @var{replacement} says which newer command should be used in
28970 favor of the deprecated one; if it is given, @value{GDBN} will mention
28971 the replacement as part of the warning.
28973 @kindex maint dump-me
28974 @item maint dump-me
28975 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
28976 Cause a fatal signal in the debugger and force it to dump its core.
28977 This is supported only on systems which support aborting a program
28978 with the @code{SIGQUIT} signal.
28980 @kindex maint internal-error
28981 @kindex maint internal-warning
28982 @item maint internal-error @r{[}@var{message-text}@r{]}
28983 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
28984 Cause @value{GDBN} to call the internal function @code{internal_error}
28985 or @code{internal_warning} and hence behave as though an internal error
28986 or internal warning has been detected. In addition to reporting the
28987 internal problem, these functions give the user the opportunity to
28988 either quit @value{GDBN} or create a core file of the current
28989 @value{GDBN} session.
28991 These commands take an optional parameter @var{message-text} that is
28992 used as the text of the error or warning message.
28994 Here's an example of using @code{internal-error}:
28997 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
28998 @dots{}/maint.c:121: internal-error: testing, 1, 2
28999 A problem internal to GDB has been detected. Further
29000 debugging may prove unreliable.
29001 Quit this debugging session? (y or n) @kbd{n}
29002 Create a core file? (y or n) @kbd{n}
29006 @cindex @value{GDBN} internal error
29007 @cindex internal errors, control of @value{GDBN} behavior
29009 @kindex maint set internal-error
29010 @kindex maint show internal-error
29011 @kindex maint set internal-warning
29012 @kindex maint show internal-warning
29013 @item maint set internal-error @var{action} [ask|yes|no]
29014 @itemx maint show internal-error @var{action}
29015 @itemx maint set internal-warning @var{action} [ask|yes|no]
29016 @itemx maint show internal-warning @var{action}
29017 When @value{GDBN} reports an internal problem (error or warning) it
29018 gives the user the opportunity to both quit @value{GDBN} and create a
29019 core file of the current @value{GDBN} session. These commands let you
29020 override the default behaviour for each particular @var{action},
29021 described in the table below.
29025 You can specify that @value{GDBN} should always (yes) or never (no)
29026 quit. The default is to ask the user what to do.
29029 You can specify that @value{GDBN} should always (yes) or never (no)
29030 create a core file. The default is to ask the user what to do.
29033 @kindex maint packet
29034 @item maint packet @var{text}
29035 If @value{GDBN} is talking to an inferior via the serial protocol,
29036 then this command sends the string @var{text} to the inferior, and
29037 displays the response packet. @value{GDBN} supplies the initial
29038 @samp{$} character, the terminating @samp{#} character, and the
29041 @kindex maint print architecture
29042 @item maint print architecture @r{[}@var{file}@r{]}
29043 Print the entire architecture configuration. The optional argument
29044 @var{file} names the file where the output goes.
29046 @kindex maint print c-tdesc
29047 @item maint print c-tdesc
29048 Print the current target description (@pxref{Target Descriptions}) as
29049 a C source file. The created source file can be used in @value{GDBN}
29050 when an XML parser is not available to parse the description.
29052 @kindex maint print dummy-frames
29053 @item maint print dummy-frames
29054 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
29057 (@value{GDBP}) @kbd{b add}
29059 (@value{GDBP}) @kbd{print add(2,3)}
29060 Breakpoint 2, add (a=2, b=3) at @dots{}
29062 The program being debugged stopped while in a function called from GDB.
29064 (@value{GDBP}) @kbd{maint print dummy-frames}
29065 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
29066 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
29067 call_lo=0x01014000 call_hi=0x01014001
29071 Takes an optional file parameter.
29073 @kindex maint print registers
29074 @kindex maint print raw-registers
29075 @kindex maint print cooked-registers
29076 @kindex maint print register-groups
29077 @item maint print registers @r{[}@var{file}@r{]}
29078 @itemx maint print raw-registers @r{[}@var{file}@r{]}
29079 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
29080 @itemx maint print register-groups @r{[}@var{file}@r{]}
29081 Print @value{GDBN}'s internal register data structures.
29083 The command @code{maint print raw-registers} includes the contents of
29084 the raw register cache; the command @code{maint print cooked-registers}
29085 includes the (cooked) value of all registers; and the command
29086 @code{maint print register-groups} includes the groups that each
29087 register is a member of. @xref{Registers,, Registers, gdbint,
29088 @value{GDBN} Internals}.
29090 These commands take an optional parameter, a file name to which to
29091 write the information.
29093 @kindex maint print reggroups
29094 @item maint print reggroups @r{[}@var{file}@r{]}
29095 Print @value{GDBN}'s internal register group data structures. The
29096 optional argument @var{file} tells to what file to write the
29099 The register groups info looks like this:
29102 (@value{GDBP}) @kbd{maint print reggroups}
29115 This command forces @value{GDBN} to flush its internal register cache.
29117 @kindex maint print objfiles
29118 @cindex info for known object files
29119 @item maint print objfiles
29120 Print a dump of all known object files. For each object file, this
29121 command prints its name, address in memory, and all of its psymtabs
29124 @kindex maint print statistics
29125 @cindex bcache statistics
29126 @item maint print statistics
29127 This command prints, for each object file in the program, various data
29128 about that object file followed by the byte cache (@dfn{bcache})
29129 statistics for the object file. The objfile data includes the number
29130 of minimal, partial, full, and stabs symbols, the number of types
29131 defined by the objfile, the number of as yet unexpanded psym tables,
29132 the number of line tables and string tables, and the amount of memory
29133 used by the various tables. The bcache statistics include the counts,
29134 sizes, and counts of duplicates of all and unique objects, max,
29135 average, and median entry size, total memory used and its overhead and
29136 savings, and various measures of the hash table size and chain
29139 @kindex maint print target-stack
29140 @cindex target stack description
29141 @item maint print target-stack
29142 A @dfn{target} is an interface between the debugger and a particular
29143 kind of file or process. Targets can be stacked in @dfn{strata},
29144 so that more than one target can potentially respond to a request.
29145 In particular, memory accesses will walk down the stack of targets
29146 until they find a target that is interested in handling that particular
29149 This command prints a short description of each layer that was pushed on
29150 the @dfn{target stack}, starting from the top layer down to the bottom one.
29152 @kindex maint print type
29153 @cindex type chain of a data type
29154 @item maint print type @var{expr}
29155 Print the type chain for a type specified by @var{expr}. The argument
29156 can be either a type name or a symbol. If it is a symbol, the type of
29157 that symbol is described. The type chain produced by this command is
29158 a recursive definition of the data type as stored in @value{GDBN}'s
29159 data structures, including its flags and contained types.
29161 @kindex maint set dwarf2 max-cache-age
29162 @kindex maint show dwarf2 max-cache-age
29163 @item maint set dwarf2 max-cache-age
29164 @itemx maint show dwarf2 max-cache-age
29165 Control the DWARF 2 compilation unit cache.
29167 @cindex DWARF 2 compilation units cache
29168 In object files with inter-compilation-unit references, such as those
29169 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
29170 reader needs to frequently refer to previously read compilation units.
29171 This setting controls how long a compilation unit will remain in the
29172 cache if it is not referenced. A higher limit means that cached
29173 compilation units will be stored in memory longer, and more total
29174 memory will be used. Setting it to zero disables caching, which will
29175 slow down @value{GDBN} startup, but reduce memory consumption.
29177 @kindex maint set profile
29178 @kindex maint show profile
29179 @cindex profiling GDB
29180 @item maint set profile
29181 @itemx maint show profile
29182 Control profiling of @value{GDBN}.
29184 Profiling will be disabled until you use the @samp{maint set profile}
29185 command to enable it. When you enable profiling, the system will begin
29186 collecting timing and execution count data; when you disable profiling or
29187 exit @value{GDBN}, the results will be written to a log file. Remember that
29188 if you use profiling, @value{GDBN} will overwrite the profiling log file
29189 (often called @file{gmon.out}). If you have a record of important profiling
29190 data in a @file{gmon.out} file, be sure to move it to a safe location.
29192 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
29193 compiled with the @samp{-pg} compiler option.
29195 @kindex maint set show-debug-regs
29196 @kindex maint show show-debug-regs
29197 @cindex hardware debug registers
29198 @item maint set show-debug-regs
29199 @itemx maint show show-debug-regs
29200 Control whether to show variables that mirror the hardware debug
29201 registers. Use @code{ON} to enable, @code{OFF} to disable. If
29202 enabled, the debug registers values are shown when @value{GDBN} inserts or
29203 removes a hardware breakpoint or watchpoint, and when the inferior
29204 triggers a hardware-assisted breakpoint or watchpoint.
29206 @kindex maint space
29207 @cindex memory used by commands
29209 Control whether to display memory usage for each command. If set to a
29210 nonzero value, @value{GDBN} will display how much memory each command
29211 took, following the command's own output. This can also be requested
29212 by invoking @value{GDBN} with the @option{--statistics} command-line
29213 switch (@pxref{Mode Options}).
29216 @cindex time of command execution
29218 Control whether to display the execution time for each command. If
29219 set to a nonzero value, @value{GDBN} will display how much time it
29220 took to execute each command, following the command's own output.
29221 The time is not printed for the commands that run the target, since
29222 there's no mechanism currently to compute how much time was spend
29223 by @value{GDBN} and how much time was spend by the program been debugged.
29224 it's not possibly currently
29225 This can also be requested by invoking @value{GDBN} with the
29226 @option{--statistics} command-line switch (@pxref{Mode Options}).
29228 @kindex maint translate-address
29229 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
29230 Find the symbol stored at the location specified by the address
29231 @var{addr} and an optional section name @var{section}. If found,
29232 @value{GDBN} prints the name of the closest symbol and an offset from
29233 the symbol's location to the specified address. This is similar to
29234 the @code{info address} command (@pxref{Symbols}), except that this
29235 command also allows to find symbols in other sections.
29237 If section was not specified, the section in which the symbol was found
29238 is also printed. For dynamically linked executables, the name of
29239 executable or shared library containing the symbol is printed as well.
29243 The following command is useful for non-interactive invocations of
29244 @value{GDBN}, such as in the test suite.
29247 @item set watchdog @var{nsec}
29248 @kindex set watchdog
29249 @cindex watchdog timer
29250 @cindex timeout for commands
29251 Set the maximum number of seconds @value{GDBN} will wait for the
29252 target operation to finish. If this time expires, @value{GDBN}
29253 reports and error and the command is aborted.
29255 @item show watchdog
29256 Show the current setting of the target wait timeout.
29259 @node Remote Protocol
29260 @appendix @value{GDBN} Remote Serial Protocol
29265 * Stop Reply Packets::
29266 * General Query Packets::
29267 * Architecture-Specific Protocol Details::
29268 * Tracepoint Packets::
29269 * Host I/O Packets::
29271 * Notification Packets::
29272 * Remote Non-Stop::
29273 * Packet Acknowledgment::
29275 * File-I/O Remote Protocol Extension::
29276 * Library List Format::
29277 * Memory Map Format::
29278 * Thread List Format::
29284 There may be occasions when you need to know something about the
29285 protocol---for example, if there is only one serial port to your target
29286 machine, you might want your program to do something special if it
29287 recognizes a packet meant for @value{GDBN}.
29289 In the examples below, @samp{->} and @samp{<-} are used to indicate
29290 transmitted and received data, respectively.
29292 @cindex protocol, @value{GDBN} remote serial
29293 @cindex serial protocol, @value{GDBN} remote
29294 @cindex remote serial protocol
29295 All @value{GDBN} commands and responses (other than acknowledgments
29296 and notifications, see @ref{Notification Packets}) are sent as a
29297 @var{packet}. A @var{packet} is introduced with the character
29298 @samp{$}, the actual @var{packet-data}, and the terminating character
29299 @samp{#} followed by a two-digit @var{checksum}:
29302 @code{$}@var{packet-data}@code{#}@var{checksum}
29306 @cindex checksum, for @value{GDBN} remote
29308 The two-digit @var{checksum} is computed as the modulo 256 sum of all
29309 characters between the leading @samp{$} and the trailing @samp{#} (an
29310 eight bit unsigned checksum).
29312 Implementors should note that prior to @value{GDBN} 5.0 the protocol
29313 specification also included an optional two-digit @var{sequence-id}:
29316 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
29319 @cindex sequence-id, for @value{GDBN} remote
29321 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
29322 has never output @var{sequence-id}s. Stubs that handle packets added
29323 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
29325 When either the host or the target machine receives a packet, the first
29326 response expected is an acknowledgment: either @samp{+} (to indicate
29327 the package was received correctly) or @samp{-} (to request
29331 -> @code{$}@var{packet-data}@code{#}@var{checksum}
29336 The @samp{+}/@samp{-} acknowledgments can be disabled
29337 once a connection is established.
29338 @xref{Packet Acknowledgment}, for details.
29340 The host (@value{GDBN}) sends @var{command}s, and the target (the
29341 debugging stub incorporated in your program) sends a @var{response}. In
29342 the case of step and continue @var{command}s, the response is only sent
29343 when the operation has completed, and the target has again stopped all
29344 threads in all attached processes. This is the default all-stop mode
29345 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
29346 execution mode; see @ref{Remote Non-Stop}, for details.
29348 @var{packet-data} consists of a sequence of characters with the
29349 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
29352 @cindex remote protocol, field separator
29353 Fields within the packet should be separated using @samp{,} @samp{;} or
29354 @samp{:}. Except where otherwise noted all numbers are represented in
29355 @sc{hex} with leading zeros suppressed.
29357 Implementors should note that prior to @value{GDBN} 5.0, the character
29358 @samp{:} could not appear as the third character in a packet (as it
29359 would potentially conflict with the @var{sequence-id}).
29361 @cindex remote protocol, binary data
29362 @anchor{Binary Data}
29363 Binary data in most packets is encoded either as two hexadecimal
29364 digits per byte of binary data. This allowed the traditional remote
29365 protocol to work over connections which were only seven-bit clean.
29366 Some packets designed more recently assume an eight-bit clean
29367 connection, and use a more efficient encoding to send and receive
29370 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
29371 as an escape character. Any escaped byte is transmitted as the escape
29372 character followed by the original character XORed with @code{0x20}.
29373 For example, the byte @code{0x7d} would be transmitted as the two
29374 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
29375 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
29376 @samp{@}}) must always be escaped. Responses sent by the stub
29377 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
29378 is not interpreted as the start of a run-length encoded sequence
29381 Response @var{data} can be run-length encoded to save space.
29382 Run-length encoding replaces runs of identical characters with one
29383 instance of the repeated character, followed by a @samp{*} and a
29384 repeat count. The repeat count is itself sent encoded, to avoid
29385 binary characters in @var{data}: a value of @var{n} is sent as
29386 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
29387 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
29388 code 32) for a repeat count of 3. (This is because run-length
29389 encoding starts to win for counts 3 or more.) Thus, for example,
29390 @samp{0* } is a run-length encoding of ``0000'': the space character
29391 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
29394 The printable characters @samp{#} and @samp{$} or with a numeric value
29395 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
29396 seven repeats (@samp{$}) can be expanded using a repeat count of only
29397 five (@samp{"}). For example, @samp{00000000} can be encoded as
29400 The error response returned for some packets includes a two character
29401 error number. That number is not well defined.
29403 @cindex empty response, for unsupported packets
29404 For any @var{command} not supported by the stub, an empty response
29405 (@samp{$#00}) should be returned. That way it is possible to extend the
29406 protocol. A newer @value{GDBN} can tell if a packet is supported based
29409 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
29410 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
29416 The following table provides a complete list of all currently defined
29417 @var{command}s and their corresponding response @var{data}.
29418 @xref{File-I/O Remote Protocol Extension}, for details about the File
29419 I/O extension of the remote protocol.
29421 Each packet's description has a template showing the packet's overall
29422 syntax, followed by an explanation of the packet's meaning. We
29423 include spaces in some of the templates for clarity; these are not
29424 part of the packet's syntax. No @value{GDBN} packet uses spaces to
29425 separate its components. For example, a template like @samp{foo
29426 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
29427 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
29428 @var{baz}. @value{GDBN} does not transmit a space character between the
29429 @samp{foo} and the @var{bar}, or between the @var{bar} and the
29432 @cindex @var{thread-id}, in remote protocol
29433 @anchor{thread-id syntax}
29434 Several packets and replies include a @var{thread-id} field to identify
29435 a thread. Normally these are positive numbers with a target-specific
29436 interpretation, formatted as big-endian hex strings. A @var{thread-id}
29437 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
29440 In addition, the remote protocol supports a multiprocess feature in
29441 which the @var{thread-id} syntax is extended to optionally include both
29442 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
29443 The @var{pid} (process) and @var{tid} (thread) components each have the
29444 format described above: a positive number with target-specific
29445 interpretation formatted as a big-endian hex string, literal @samp{-1}
29446 to indicate all processes or threads (respectively), or @samp{0} to
29447 indicate an arbitrary process or thread. Specifying just a process, as
29448 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
29449 error to specify all processes but a specific thread, such as
29450 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
29451 for those packets and replies explicitly documented to include a process
29452 ID, rather than a @var{thread-id}.
29454 The multiprocess @var{thread-id} syntax extensions are only used if both
29455 @value{GDBN} and the stub report support for the @samp{multiprocess}
29456 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
29459 Note that all packet forms beginning with an upper- or lower-case
29460 letter, other than those described here, are reserved for future use.
29462 Here are the packet descriptions.
29467 @cindex @samp{!} packet
29468 @anchor{extended mode}
29469 Enable extended mode. In extended mode, the remote server is made
29470 persistent. The @samp{R} packet is used to restart the program being
29476 The remote target both supports and has enabled extended mode.
29480 @cindex @samp{?} packet
29481 Indicate the reason the target halted. The reply is the same as for
29482 step and continue. This packet has a special interpretation when the
29483 target is in non-stop mode; see @ref{Remote Non-Stop}.
29486 @xref{Stop Reply Packets}, for the reply specifications.
29488 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
29489 @cindex @samp{A} packet
29490 Initialized @code{argv[]} array passed into program. @var{arglen}
29491 specifies the number of bytes in the hex encoded byte stream
29492 @var{arg}. See @code{gdbserver} for more details.
29497 The arguments were set.
29503 @cindex @samp{b} packet
29504 (Don't use this packet; its behavior is not well-defined.)
29505 Change the serial line speed to @var{baud}.
29507 JTC: @emph{When does the transport layer state change? When it's
29508 received, or after the ACK is transmitted. In either case, there are
29509 problems if the command or the acknowledgment packet is dropped.}
29511 Stan: @emph{If people really wanted to add something like this, and get
29512 it working for the first time, they ought to modify ser-unix.c to send
29513 some kind of out-of-band message to a specially-setup stub and have the
29514 switch happen "in between" packets, so that from remote protocol's point
29515 of view, nothing actually happened.}
29517 @item B @var{addr},@var{mode}
29518 @cindex @samp{B} packet
29519 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
29520 breakpoint at @var{addr}.
29522 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
29523 (@pxref{insert breakpoint or watchpoint packet}).
29525 @cindex @samp{bc} packet
29528 Backward continue. Execute the target system in reverse. No parameter.
29529 @xref{Reverse Execution}, for more information.
29532 @xref{Stop Reply Packets}, for the reply specifications.
29534 @cindex @samp{bs} packet
29537 Backward single step. Execute one instruction in reverse. No parameter.
29538 @xref{Reverse Execution}, for more information.
29541 @xref{Stop Reply Packets}, for the reply specifications.
29543 @item c @r{[}@var{addr}@r{]}
29544 @cindex @samp{c} packet
29545 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
29546 resume at current address.
29549 @xref{Stop Reply Packets}, for the reply specifications.
29551 @item C @var{sig}@r{[};@var{addr}@r{]}
29552 @cindex @samp{C} packet
29553 Continue with signal @var{sig} (hex signal number). If
29554 @samp{;@var{addr}} is omitted, resume at same address.
29557 @xref{Stop Reply Packets}, for the reply specifications.
29560 @cindex @samp{d} packet
29563 Don't use this packet; instead, define a general set packet
29564 (@pxref{General Query Packets}).
29568 @cindex @samp{D} packet
29569 The first form of the packet is used to detach @value{GDBN} from the
29570 remote system. It is sent to the remote target
29571 before @value{GDBN} disconnects via the @code{detach} command.
29573 The second form, including a process ID, is used when multiprocess
29574 protocol extensions are enabled (@pxref{multiprocess extensions}), to
29575 detach only a specific process. The @var{pid} is specified as a
29576 big-endian hex string.
29586 @item F @var{RC},@var{EE},@var{CF};@var{XX}
29587 @cindex @samp{F} packet
29588 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
29589 This is part of the File-I/O protocol extension. @xref{File-I/O
29590 Remote Protocol Extension}, for the specification.
29593 @anchor{read registers packet}
29594 @cindex @samp{g} packet
29595 Read general registers.
29599 @item @var{XX@dots{}}
29600 Each byte of register data is described by two hex digits. The bytes
29601 with the register are transmitted in target byte order. The size of
29602 each register and their position within the @samp{g} packet are
29603 determined by the @value{GDBN} internal gdbarch functions
29604 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
29605 specification of several standard @samp{g} packets is specified below.
29610 @item G @var{XX@dots{}}
29611 @cindex @samp{G} packet
29612 Write general registers. @xref{read registers packet}, for a
29613 description of the @var{XX@dots{}} data.
29623 @item H @var{c} @var{thread-id}
29624 @cindex @samp{H} packet
29625 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
29626 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
29627 should be @samp{c} for step and continue operations, @samp{g} for other
29628 operations. The thread designator @var{thread-id} has the format and
29629 interpretation described in @ref{thread-id syntax}.
29640 @c 'H': How restrictive (or permissive) is the thread model. If a
29641 @c thread is selected and stopped, are other threads allowed
29642 @c to continue to execute? As I mentioned above, I think the
29643 @c semantics of each command when a thread is selected must be
29644 @c described. For example:
29646 @c 'g': If the stub supports threads and a specific thread is
29647 @c selected, returns the register block from that thread;
29648 @c otherwise returns current registers.
29650 @c 'G' If the stub supports threads and a specific thread is
29651 @c selected, sets the registers of the register block of
29652 @c that thread; otherwise sets current registers.
29654 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
29655 @anchor{cycle step packet}
29656 @cindex @samp{i} packet
29657 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
29658 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
29659 step starting at that address.
29662 @cindex @samp{I} packet
29663 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
29667 @cindex @samp{k} packet
29670 FIXME: @emph{There is no description of how to operate when a specific
29671 thread context has been selected (i.e.@: does 'k' kill only that
29674 @item m @var{addr},@var{length}
29675 @cindex @samp{m} packet
29676 Read @var{length} bytes of memory starting at address @var{addr}.
29677 Note that @var{addr} may not be aligned to any particular boundary.
29679 The stub need not use any particular size or alignment when gathering
29680 data from memory for the response; even if @var{addr} is word-aligned
29681 and @var{length} is a multiple of the word size, the stub is free to
29682 use byte accesses, or not. For this reason, this packet may not be
29683 suitable for accessing memory-mapped I/O devices.
29684 @cindex alignment of remote memory accesses
29685 @cindex size of remote memory accesses
29686 @cindex memory, alignment and size of remote accesses
29690 @item @var{XX@dots{}}
29691 Memory contents; each byte is transmitted as a two-digit hexadecimal
29692 number. The reply may contain fewer bytes than requested if the
29693 server was able to read only part of the region of memory.
29698 @item M @var{addr},@var{length}:@var{XX@dots{}}
29699 @cindex @samp{M} packet
29700 Write @var{length} bytes of memory starting at address @var{addr}.
29701 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
29702 hexadecimal number.
29709 for an error (this includes the case where only part of the data was
29714 @cindex @samp{p} packet
29715 Read the value of register @var{n}; @var{n} is in hex.
29716 @xref{read registers packet}, for a description of how the returned
29717 register value is encoded.
29721 @item @var{XX@dots{}}
29722 the register's value
29726 Indicating an unrecognized @var{query}.
29729 @item P @var{n@dots{}}=@var{r@dots{}}
29730 @anchor{write register packet}
29731 @cindex @samp{P} packet
29732 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
29733 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
29734 digits for each byte in the register (target byte order).
29744 @item q @var{name} @var{params}@dots{}
29745 @itemx Q @var{name} @var{params}@dots{}
29746 @cindex @samp{q} packet
29747 @cindex @samp{Q} packet
29748 General query (@samp{q}) and set (@samp{Q}). These packets are
29749 described fully in @ref{General Query Packets}.
29752 @cindex @samp{r} packet
29753 Reset the entire system.
29755 Don't use this packet; use the @samp{R} packet instead.
29758 @cindex @samp{R} packet
29759 Restart the program being debugged. @var{XX}, while needed, is ignored.
29760 This packet is only available in extended mode (@pxref{extended mode}).
29762 The @samp{R} packet has no reply.
29764 @item s @r{[}@var{addr}@r{]}
29765 @cindex @samp{s} packet
29766 Single step. @var{addr} is the address at which to resume. If
29767 @var{addr} is omitted, resume at same address.
29770 @xref{Stop Reply Packets}, for the reply specifications.
29772 @item S @var{sig}@r{[};@var{addr}@r{]}
29773 @anchor{step with signal packet}
29774 @cindex @samp{S} packet
29775 Step with signal. This is analogous to the @samp{C} packet, but
29776 requests a single-step, rather than a normal resumption of execution.
29779 @xref{Stop Reply Packets}, for the reply specifications.
29781 @item t @var{addr}:@var{PP},@var{MM}
29782 @cindex @samp{t} packet
29783 Search backwards starting at address @var{addr} for a match with pattern
29784 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
29785 @var{addr} must be at least 3 digits.
29787 @item T @var{thread-id}
29788 @cindex @samp{T} packet
29789 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
29794 thread is still alive
29800 Packets starting with @samp{v} are identified by a multi-letter name,
29801 up to the first @samp{;} or @samp{?} (or the end of the packet).
29803 @item vAttach;@var{pid}
29804 @cindex @samp{vAttach} packet
29805 Attach to a new process with the specified process ID @var{pid}.
29806 The process ID is a
29807 hexadecimal integer identifying the process. In all-stop mode, all
29808 threads in the attached process are stopped; in non-stop mode, it may be
29809 attached without being stopped if that is supported by the target.
29811 @c In non-stop mode, on a successful vAttach, the stub should set the
29812 @c current thread to a thread of the newly-attached process. After
29813 @c attaching, GDB queries for the attached process's thread ID with qC.
29814 @c Also note that, from a user perspective, whether or not the
29815 @c target is stopped on attach in non-stop mode depends on whether you
29816 @c use the foreground or background version of the attach command, not
29817 @c on what vAttach does; GDB does the right thing with respect to either
29818 @c stopping or restarting threads.
29820 This packet is only available in extended mode (@pxref{extended mode}).
29826 @item @r{Any stop packet}
29827 for success in all-stop mode (@pxref{Stop Reply Packets})
29829 for success in non-stop mode (@pxref{Remote Non-Stop})
29832 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
29833 @cindex @samp{vCont} packet
29834 Resume the inferior, specifying different actions for each thread.
29835 If an action is specified with no @var{thread-id}, then it is applied to any
29836 threads that don't have a specific action specified; if no default action is
29837 specified then other threads should remain stopped in all-stop mode and
29838 in their current state in non-stop mode.
29839 Specifying multiple
29840 default actions is an error; specifying no actions is also an error.
29841 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
29843 Currently supported actions are:
29849 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
29853 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
29858 The optional argument @var{addr} normally associated with the
29859 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
29860 not supported in @samp{vCont}.
29862 The @samp{t} action is only relevant in non-stop mode
29863 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
29864 A stop reply should be generated for any affected thread not already stopped.
29865 When a thread is stopped by means of a @samp{t} action,
29866 the corresponding stop reply should indicate that the thread has stopped with
29867 signal @samp{0}, regardless of whether the target uses some other signal
29868 as an implementation detail.
29871 @xref{Stop Reply Packets}, for the reply specifications.
29874 @cindex @samp{vCont?} packet
29875 Request a list of actions supported by the @samp{vCont} packet.
29879 @item vCont@r{[};@var{action}@dots{}@r{]}
29880 The @samp{vCont} packet is supported. Each @var{action} is a supported
29881 command in the @samp{vCont} packet.
29883 The @samp{vCont} packet is not supported.
29886 @item vFile:@var{operation}:@var{parameter}@dots{}
29887 @cindex @samp{vFile} packet
29888 Perform a file operation on the target system. For details,
29889 see @ref{Host I/O Packets}.
29891 @item vFlashErase:@var{addr},@var{length}
29892 @cindex @samp{vFlashErase} packet
29893 Direct the stub to erase @var{length} bytes of flash starting at
29894 @var{addr}. The region may enclose any number of flash blocks, but
29895 its start and end must fall on block boundaries, as indicated by the
29896 flash block size appearing in the memory map (@pxref{Memory Map
29897 Format}). @value{GDBN} groups flash memory programming operations
29898 together, and sends a @samp{vFlashDone} request after each group; the
29899 stub is allowed to delay erase operation until the @samp{vFlashDone}
29900 packet is received.
29902 The stub must support @samp{vCont} if it reports support for
29903 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
29904 this case @samp{vCont} actions can be specified to apply to all threads
29905 in a process by using the @samp{p@var{pid}.-1} form of the
29916 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
29917 @cindex @samp{vFlashWrite} packet
29918 Direct the stub to write data to flash address @var{addr}. The data
29919 is passed in binary form using the same encoding as for the @samp{X}
29920 packet (@pxref{Binary Data}). The memory ranges specified by
29921 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
29922 not overlap, and must appear in order of increasing addresses
29923 (although @samp{vFlashErase} packets for higher addresses may already
29924 have been received; the ordering is guaranteed only between
29925 @samp{vFlashWrite} packets). If a packet writes to an address that was
29926 neither erased by a preceding @samp{vFlashErase} packet nor by some other
29927 target-specific method, the results are unpredictable.
29935 for vFlashWrite addressing non-flash memory
29941 @cindex @samp{vFlashDone} packet
29942 Indicate to the stub that flash programming operation is finished.
29943 The stub is permitted to delay or batch the effects of a group of
29944 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
29945 @samp{vFlashDone} packet is received. The contents of the affected
29946 regions of flash memory are unpredictable until the @samp{vFlashDone}
29947 request is completed.
29949 @item vKill;@var{pid}
29950 @cindex @samp{vKill} packet
29951 Kill the process with the specified process ID. @var{pid} is a
29952 hexadecimal integer identifying the process. This packet is used in
29953 preference to @samp{k} when multiprocess protocol extensions are
29954 supported; see @ref{multiprocess extensions}.
29964 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
29965 @cindex @samp{vRun} packet
29966 Run the program @var{filename}, passing it each @var{argument} on its
29967 command line. The file and arguments are hex-encoded strings. If
29968 @var{filename} is an empty string, the stub may use a default program
29969 (e.g.@: the last program run). The program is created in the stopped
29972 @c FIXME: What about non-stop mode?
29974 This packet is only available in extended mode (@pxref{extended mode}).
29980 @item @r{Any stop packet}
29981 for success (@pxref{Stop Reply Packets})
29985 @anchor{vStopped packet}
29986 @cindex @samp{vStopped} packet
29988 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
29989 reply and prompt for the stub to report another one.
29993 @item @r{Any stop packet}
29994 if there is another unreported stop event (@pxref{Stop Reply Packets})
29996 if there are no unreported stop events
29999 @item X @var{addr},@var{length}:@var{XX@dots{}}
30001 @cindex @samp{X} packet
30002 Write data to memory, where the data is transmitted in binary.
30003 @var{addr} is address, @var{length} is number of bytes,
30004 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
30014 @item z @var{type},@var{addr},@var{kind}
30015 @itemx Z @var{type},@var{addr},@var{kind}
30016 @anchor{insert breakpoint or watchpoint packet}
30017 @cindex @samp{z} packet
30018 @cindex @samp{Z} packets
30019 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
30020 watchpoint starting at address @var{address} of kind @var{kind}.
30022 Each breakpoint and watchpoint packet @var{type} is documented
30025 @emph{Implementation notes: A remote target shall return an empty string
30026 for an unrecognized breakpoint or watchpoint packet @var{type}. A
30027 remote target shall support either both or neither of a given
30028 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
30029 avoid potential problems with duplicate packets, the operations should
30030 be implemented in an idempotent way.}
30032 @item z0,@var{addr},@var{kind}
30033 @itemx Z0,@var{addr},@var{kind}
30034 @cindex @samp{z0} packet
30035 @cindex @samp{Z0} packet
30036 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
30037 @var{addr} of type @var{kind}.
30039 A memory breakpoint is implemented by replacing the instruction at
30040 @var{addr} with a software breakpoint or trap instruction. The
30041 @var{kind} is target-specific and typically indicates the size of
30042 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
30043 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
30044 architectures have additional meanings for @var{kind};
30045 see @ref{Architecture-Specific Protocol Details}.
30047 @emph{Implementation note: It is possible for a target to copy or move
30048 code that contains memory breakpoints (e.g., when implementing
30049 overlays). The behavior of this packet, in the presence of such a
30050 target, is not defined.}
30062 @item z1,@var{addr},@var{kind}
30063 @itemx Z1,@var{addr},@var{kind}
30064 @cindex @samp{z1} packet
30065 @cindex @samp{Z1} packet
30066 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
30067 address @var{addr}.
30069 A hardware breakpoint is implemented using a mechanism that is not
30070 dependant on being able to modify the target's memory. @var{kind}
30071 has the same meaning as in @samp{Z0} packets.
30073 @emph{Implementation note: A hardware breakpoint is not affected by code
30086 @item z2,@var{addr},@var{kind}
30087 @itemx Z2,@var{addr},@var{kind}
30088 @cindex @samp{z2} packet
30089 @cindex @samp{Z2} packet
30090 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
30091 @var{kind} is interpreted as the number of bytes to watch.
30103 @item z3,@var{addr},@var{kind}
30104 @itemx Z3,@var{addr},@var{kind}
30105 @cindex @samp{z3} packet
30106 @cindex @samp{Z3} packet
30107 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
30108 @var{kind} is interpreted as the number of bytes to watch.
30120 @item z4,@var{addr},@var{kind}
30121 @itemx Z4,@var{addr},@var{kind}
30122 @cindex @samp{z4} packet
30123 @cindex @samp{Z4} packet
30124 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
30125 @var{kind} is interpreted as the number of bytes to watch.
30139 @node Stop Reply Packets
30140 @section Stop Reply Packets
30141 @cindex stop reply packets
30143 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
30144 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
30145 receive any of the below as a reply. Except for @samp{?}
30146 and @samp{vStopped}, that reply is only returned
30147 when the target halts. In the below the exact meaning of @dfn{signal
30148 number} is defined by the header @file{include/gdb/signals.h} in the
30149 @value{GDBN} source code.
30151 As in the description of request packets, we include spaces in the
30152 reply templates for clarity; these are not part of the reply packet's
30153 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
30159 The program received signal number @var{AA} (a two-digit hexadecimal
30160 number). This is equivalent to a @samp{T} response with no
30161 @var{n}:@var{r} pairs.
30163 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
30164 @cindex @samp{T} packet reply
30165 The program received signal number @var{AA} (a two-digit hexadecimal
30166 number). This is equivalent to an @samp{S} response, except that the
30167 @samp{@var{n}:@var{r}} pairs can carry values of important registers
30168 and other information directly in the stop reply packet, reducing
30169 round-trip latency. Single-step and breakpoint traps are reported
30170 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
30174 If @var{n} is a hexadecimal number, it is a register number, and the
30175 corresponding @var{r} gives that register's value. @var{r} is a
30176 series of bytes in target byte order, with each byte given by a
30177 two-digit hex number.
30180 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
30181 the stopped thread, as specified in @ref{thread-id syntax}.
30184 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
30185 the core on which the stop event was detected.
30188 If @var{n} is a recognized @dfn{stop reason}, it describes a more
30189 specific event that stopped the target. The currently defined stop
30190 reasons are listed below. @var{aa} should be @samp{05}, the trap
30191 signal. At most one stop reason should be present.
30194 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
30195 and go on to the next; this allows us to extend the protocol in the
30199 The currently defined stop reasons are:
30205 The packet indicates a watchpoint hit, and @var{r} is the data address, in
30208 @cindex shared library events, remote reply
30210 The packet indicates that the loaded libraries have changed.
30211 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
30212 list of loaded libraries. @var{r} is ignored.
30214 @cindex replay log events, remote reply
30216 The packet indicates that the target cannot continue replaying
30217 logged execution events, because it has reached the end (or the
30218 beginning when executing backward) of the log. The value of @var{r}
30219 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
30220 for more information.
30224 @itemx W @var{AA} ; process:@var{pid}
30225 The process exited, and @var{AA} is the exit status. This is only
30226 applicable to certain targets.
30228 The second form of the response, including the process ID of the exited
30229 process, can be used only when @value{GDBN} has reported support for
30230 multiprocess protocol extensions; see @ref{multiprocess extensions}.
30231 The @var{pid} is formatted as a big-endian hex string.
30234 @itemx X @var{AA} ; process:@var{pid}
30235 The process terminated with signal @var{AA}.
30237 The second form of the response, including the process ID of the
30238 terminated process, can be used only when @value{GDBN} has reported
30239 support for multiprocess protocol extensions; see @ref{multiprocess
30240 extensions}. The @var{pid} is formatted as a big-endian hex string.
30242 @item O @var{XX}@dots{}
30243 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
30244 written as the program's console output. This can happen at any time
30245 while the program is running and the debugger should continue to wait
30246 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
30248 @item F @var{call-id},@var{parameter}@dots{}
30249 @var{call-id} is the identifier which says which host system call should
30250 be called. This is just the name of the function. Translation into the
30251 correct system call is only applicable as it's defined in @value{GDBN}.
30252 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
30255 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
30256 this very system call.
30258 The target replies with this packet when it expects @value{GDBN} to
30259 call a host system call on behalf of the target. @value{GDBN} replies
30260 with an appropriate @samp{F} packet and keeps up waiting for the next
30261 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
30262 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
30263 Protocol Extension}, for more details.
30267 @node General Query Packets
30268 @section General Query Packets
30269 @cindex remote query requests
30271 Packets starting with @samp{q} are @dfn{general query packets};
30272 packets starting with @samp{Q} are @dfn{general set packets}. General
30273 query and set packets are a semi-unified form for retrieving and
30274 sending information to and from the stub.
30276 The initial letter of a query or set packet is followed by a name
30277 indicating what sort of thing the packet applies to. For example,
30278 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
30279 definitions with the stub. These packet names follow some
30284 The name must not contain commas, colons or semicolons.
30286 Most @value{GDBN} query and set packets have a leading upper case
30289 The names of custom vendor packets should use a company prefix, in
30290 lower case, followed by a period. For example, packets designed at
30291 the Acme Corporation might begin with @samp{qacme.foo} (for querying
30292 foos) or @samp{Qacme.bar} (for setting bars).
30295 The name of a query or set packet should be separated from any
30296 parameters by a @samp{:}; the parameters themselves should be
30297 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
30298 full packet name, and check for a separator or the end of the packet,
30299 in case two packet names share a common prefix. New packets should not begin
30300 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
30301 packets predate these conventions, and have arguments without any terminator
30302 for the packet name; we suspect they are in widespread use in places that
30303 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
30304 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
30307 Like the descriptions of the other packets, each description here
30308 has a template showing the packet's overall syntax, followed by an
30309 explanation of the packet's meaning. We include spaces in some of the
30310 templates for clarity; these are not part of the packet's syntax. No
30311 @value{GDBN} packet uses spaces to separate its components.
30313 Here are the currently defined query and set packets:
30318 @cindex current thread, remote request
30319 @cindex @samp{qC} packet
30320 Return the current thread ID.
30324 @item QC @var{thread-id}
30325 Where @var{thread-id} is a thread ID as documented in
30326 @ref{thread-id syntax}.
30327 @item @r{(anything else)}
30328 Any other reply implies the old thread ID.
30331 @item qCRC:@var{addr},@var{length}
30332 @cindex CRC of memory block, remote request
30333 @cindex @samp{qCRC} packet
30334 Compute the CRC checksum of a block of memory using CRC-32 defined in
30335 IEEE 802.3. The CRC is computed byte at a time, taking the most
30336 significant bit of each byte first. The initial pattern code
30337 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
30339 @emph{Note:} This is the same CRC used in validating separate debug
30340 files (@pxref{Separate Debug Files, , Debugging Information in Separate
30341 Files}). However the algorithm is slightly different. When validating
30342 separate debug files, the CRC is computed taking the @emph{least}
30343 significant bit of each byte first, and the final result is inverted to
30344 detect trailing zeros.
30349 An error (such as memory fault)
30350 @item C @var{crc32}
30351 The specified memory region's checksum is @var{crc32}.
30355 @itemx qsThreadInfo
30356 @cindex list active threads, remote request
30357 @cindex @samp{qfThreadInfo} packet
30358 @cindex @samp{qsThreadInfo} packet
30359 Obtain a list of all active thread IDs from the target (OS). Since there
30360 may be too many active threads to fit into one reply packet, this query
30361 works iteratively: it may require more than one query/reply sequence to
30362 obtain the entire list of threads. The first query of the sequence will
30363 be the @samp{qfThreadInfo} query; subsequent queries in the
30364 sequence will be the @samp{qsThreadInfo} query.
30366 NOTE: This packet replaces the @samp{qL} query (see below).
30370 @item m @var{thread-id}
30372 @item m @var{thread-id},@var{thread-id}@dots{}
30373 a comma-separated list of thread IDs
30375 (lower case letter @samp{L}) denotes end of list.
30378 In response to each query, the target will reply with a list of one or
30379 more thread IDs, separated by commas.
30380 @value{GDBN} will respond to each reply with a request for more thread
30381 ids (using the @samp{qs} form of the query), until the target responds
30382 with @samp{l} (lower-case el, for @dfn{last}).
30383 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
30386 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
30387 @cindex get thread-local storage address, remote request
30388 @cindex @samp{qGetTLSAddr} packet
30389 Fetch the address associated with thread local storage specified
30390 by @var{thread-id}, @var{offset}, and @var{lm}.
30392 @var{thread-id} is the thread ID associated with the
30393 thread for which to fetch the TLS address. @xref{thread-id syntax}.
30395 @var{offset} is the (big endian, hex encoded) offset associated with the
30396 thread local variable. (This offset is obtained from the debug
30397 information associated with the variable.)
30399 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
30400 the load module associated with the thread local storage. For example,
30401 a @sc{gnu}/Linux system will pass the link map address of the shared
30402 object associated with the thread local storage under consideration.
30403 Other operating environments may choose to represent the load module
30404 differently, so the precise meaning of this parameter will vary.
30408 @item @var{XX}@dots{}
30409 Hex encoded (big endian) bytes representing the address of the thread
30410 local storage requested.
30413 An error occurred. @var{nn} are hex digits.
30416 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
30419 @item qL @var{startflag} @var{threadcount} @var{nextthread}
30420 Obtain thread information from RTOS. Where: @var{startflag} (one hex
30421 digit) is one to indicate the first query and zero to indicate a
30422 subsequent query; @var{threadcount} (two hex digits) is the maximum
30423 number of threads the response packet can contain; and @var{nextthread}
30424 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
30425 returned in the response as @var{argthread}.
30427 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
30431 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
30432 Where: @var{count} (two hex digits) is the number of threads being
30433 returned; @var{done} (one hex digit) is zero to indicate more threads
30434 and one indicates no further threads; @var{argthreadid} (eight hex
30435 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
30436 is a sequence of thread IDs from the target. @var{threadid} (eight hex
30437 digits). See @code{remote.c:parse_threadlist_response()}.
30441 @cindex section offsets, remote request
30442 @cindex @samp{qOffsets} packet
30443 Get section offsets that the target used when relocating the downloaded
30448 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
30449 Relocate the @code{Text} section by @var{xxx} from its original address.
30450 Relocate the @code{Data} section by @var{yyy} from its original address.
30451 If the object file format provides segment information (e.g.@: @sc{elf}
30452 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
30453 segments by the supplied offsets.
30455 @emph{Note: while a @code{Bss} offset may be included in the response,
30456 @value{GDBN} ignores this and instead applies the @code{Data} offset
30457 to the @code{Bss} section.}
30459 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
30460 Relocate the first segment of the object file, which conventionally
30461 contains program code, to a starting address of @var{xxx}. If
30462 @samp{DataSeg} is specified, relocate the second segment, which
30463 conventionally contains modifiable data, to a starting address of
30464 @var{yyy}. @value{GDBN} will report an error if the object file
30465 does not contain segment information, or does not contain at least
30466 as many segments as mentioned in the reply. Extra segments are
30467 kept at fixed offsets relative to the last relocated segment.
30470 @item qP @var{mode} @var{thread-id}
30471 @cindex thread information, remote request
30472 @cindex @samp{qP} packet
30473 Returns information on @var{thread-id}. Where: @var{mode} is a hex
30474 encoded 32 bit mode; @var{thread-id} is a thread ID
30475 (@pxref{thread-id syntax}).
30477 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
30480 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
30484 @cindex non-stop mode, remote request
30485 @cindex @samp{QNonStop} packet
30487 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
30488 @xref{Remote Non-Stop}, for more information.
30493 The request succeeded.
30496 An error occurred. @var{nn} are hex digits.
30499 An empty reply indicates that @samp{QNonStop} is not supported by
30503 This packet is not probed by default; the remote stub must request it,
30504 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30505 Use of this packet is controlled by the @code{set non-stop} command;
30506 @pxref{Non-Stop Mode}.
30508 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
30509 @cindex pass signals to inferior, remote request
30510 @cindex @samp{QPassSignals} packet
30511 @anchor{QPassSignals}
30512 Each listed @var{signal} should be passed directly to the inferior process.
30513 Signals are numbered identically to continue packets and stop replies
30514 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
30515 strictly greater than the previous item. These signals do not need to stop
30516 the inferior, or be reported to @value{GDBN}. All other signals should be
30517 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
30518 combine; any earlier @samp{QPassSignals} list is completely replaced by the
30519 new list. This packet improves performance when using @samp{handle
30520 @var{signal} nostop noprint pass}.
30525 The request succeeded.
30528 An error occurred. @var{nn} are hex digits.
30531 An empty reply indicates that @samp{QPassSignals} is not supported by
30535 Use of this packet is controlled by the @code{set remote pass-signals}
30536 command (@pxref{Remote Configuration, set remote pass-signals}).
30537 This packet is not probed by default; the remote stub must request it,
30538 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30540 @item qRcmd,@var{command}
30541 @cindex execute remote command, remote request
30542 @cindex @samp{qRcmd} packet
30543 @var{command} (hex encoded) is passed to the local interpreter for
30544 execution. Invalid commands should be reported using the output
30545 string. Before the final result packet, the target may also respond
30546 with a number of intermediate @samp{O@var{output}} console output
30547 packets. @emph{Implementors should note that providing access to a
30548 stubs's interpreter may have security implications}.
30553 A command response with no output.
30555 A command response with the hex encoded output string @var{OUTPUT}.
30557 Indicate a badly formed request.
30559 An empty reply indicates that @samp{qRcmd} is not recognized.
30562 (Note that the @code{qRcmd} packet's name is separated from the
30563 command by a @samp{,}, not a @samp{:}, contrary to the naming
30564 conventions above. Please don't use this packet as a model for new
30567 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
30568 @cindex searching memory, in remote debugging
30569 @cindex @samp{qSearch:memory} packet
30570 @anchor{qSearch memory}
30571 Search @var{length} bytes at @var{address} for @var{search-pattern}.
30572 @var{address} and @var{length} are encoded in hex.
30573 @var{search-pattern} is a sequence of bytes, hex encoded.
30578 The pattern was not found.
30580 The pattern was found at @var{address}.
30582 A badly formed request or an error was encountered while searching memory.
30584 An empty reply indicates that @samp{qSearch:memory} is not recognized.
30587 @item QStartNoAckMode
30588 @cindex @samp{QStartNoAckMode} packet
30589 @anchor{QStartNoAckMode}
30590 Request that the remote stub disable the normal @samp{+}/@samp{-}
30591 protocol acknowledgments (@pxref{Packet Acknowledgment}).
30596 The stub has switched to no-acknowledgment mode.
30597 @value{GDBN} acknowledges this reponse,
30598 but neither the stub nor @value{GDBN} shall send or expect further
30599 @samp{+}/@samp{-} acknowledgments in the current connection.
30601 An empty reply indicates that the stub does not support no-acknowledgment mode.
30604 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
30605 @cindex supported packets, remote query
30606 @cindex features of the remote protocol
30607 @cindex @samp{qSupported} packet
30608 @anchor{qSupported}
30609 Tell the remote stub about features supported by @value{GDBN}, and
30610 query the stub for features it supports. This packet allows
30611 @value{GDBN} and the remote stub to take advantage of each others'
30612 features. @samp{qSupported} also consolidates multiple feature probes
30613 at startup, to improve @value{GDBN} performance---a single larger
30614 packet performs better than multiple smaller probe packets on
30615 high-latency links. Some features may enable behavior which must not
30616 be on by default, e.g.@: because it would confuse older clients or
30617 stubs. Other features may describe packets which could be
30618 automatically probed for, but are not. These features must be
30619 reported before @value{GDBN} will use them. This ``default
30620 unsupported'' behavior is not appropriate for all packets, but it
30621 helps to keep the initial connection time under control with new
30622 versions of @value{GDBN} which support increasing numbers of packets.
30626 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
30627 The stub supports or does not support each returned @var{stubfeature},
30628 depending on the form of each @var{stubfeature} (see below for the
30631 An empty reply indicates that @samp{qSupported} is not recognized,
30632 or that no features needed to be reported to @value{GDBN}.
30635 The allowed forms for each feature (either a @var{gdbfeature} in the
30636 @samp{qSupported} packet, or a @var{stubfeature} in the response)
30640 @item @var{name}=@var{value}
30641 The remote protocol feature @var{name} is supported, and associated
30642 with the specified @var{value}. The format of @var{value} depends
30643 on the feature, but it must not include a semicolon.
30645 The remote protocol feature @var{name} is supported, and does not
30646 need an associated value.
30648 The remote protocol feature @var{name} is not supported.
30650 The remote protocol feature @var{name} may be supported, and
30651 @value{GDBN} should auto-detect support in some other way when it is
30652 needed. This form will not be used for @var{gdbfeature} notifications,
30653 but may be used for @var{stubfeature} responses.
30656 Whenever the stub receives a @samp{qSupported} request, the
30657 supplied set of @value{GDBN} features should override any previous
30658 request. This allows @value{GDBN} to put the stub in a known
30659 state, even if the stub had previously been communicating with
30660 a different version of @value{GDBN}.
30662 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
30667 This feature indicates whether @value{GDBN} supports multiprocess
30668 extensions to the remote protocol. @value{GDBN} does not use such
30669 extensions unless the stub also reports that it supports them by
30670 including @samp{multiprocess+} in its @samp{qSupported} reply.
30671 @xref{multiprocess extensions}, for details.
30674 This feature indicates that @value{GDBN} supports the XML target
30675 description. If the stub sees @samp{xmlRegisters=} with target
30676 specific strings separated by a comma, it will report register
30680 Stubs should ignore any unknown values for
30681 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
30682 packet supports receiving packets of unlimited length (earlier
30683 versions of @value{GDBN} may reject overly long responses). Additional values
30684 for @var{gdbfeature} may be defined in the future to let the stub take
30685 advantage of new features in @value{GDBN}, e.g.@: incompatible
30686 improvements in the remote protocol---the @samp{multiprocess} feature is
30687 an example of such a feature. The stub's reply should be independent
30688 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
30689 describes all the features it supports, and then the stub replies with
30690 all the features it supports.
30692 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
30693 responses, as long as each response uses one of the standard forms.
30695 Some features are flags. A stub which supports a flag feature
30696 should respond with a @samp{+} form response. Other features
30697 require values, and the stub should respond with an @samp{=}
30700 Each feature has a default value, which @value{GDBN} will use if
30701 @samp{qSupported} is not available or if the feature is not mentioned
30702 in the @samp{qSupported} response. The default values are fixed; a
30703 stub is free to omit any feature responses that match the defaults.
30705 Not all features can be probed, but for those which can, the probing
30706 mechanism is useful: in some cases, a stub's internal
30707 architecture may not allow the protocol layer to know some information
30708 about the underlying target in advance. This is especially common in
30709 stubs which may be configured for multiple targets.
30711 These are the currently defined stub features and their properties:
30713 @multitable @columnfractions 0.35 0.2 0.12 0.2
30714 @c NOTE: The first row should be @headitem, but we do not yet require
30715 @c a new enough version of Texinfo (4.7) to use @headitem.
30717 @tab Value Required
30721 @item @samp{PacketSize}
30726 @item @samp{qXfer:auxv:read}
30731 @item @samp{qXfer:features:read}
30736 @item @samp{qXfer:libraries:read}
30741 @item @samp{qXfer:memory-map:read}
30746 @item @samp{qXfer:spu:read}
30751 @item @samp{qXfer:spu:write}
30756 @item @samp{qXfer:siginfo:read}
30761 @item @samp{qXfer:siginfo:write}
30766 @item @samp{qXfer:threads:read}
30772 @item @samp{QNonStop}
30777 @item @samp{QPassSignals}
30782 @item @samp{QStartNoAckMode}
30787 @item @samp{multiprocess}
30792 @item @samp{ConditionalTracepoints}
30797 @item @samp{ReverseContinue}
30802 @item @samp{ReverseStep}
30807 @item @samp{TracepointSource}
30814 These are the currently defined stub features, in more detail:
30817 @cindex packet size, remote protocol
30818 @item PacketSize=@var{bytes}
30819 The remote stub can accept packets up to at least @var{bytes} in
30820 length. @value{GDBN} will send packets up to this size for bulk
30821 transfers, and will never send larger packets. This is a limit on the
30822 data characters in the packet, including the frame and checksum.
30823 There is no trailing NUL byte in a remote protocol packet; if the stub
30824 stores packets in a NUL-terminated format, it should allow an extra
30825 byte in its buffer for the NUL. If this stub feature is not supported,
30826 @value{GDBN} guesses based on the size of the @samp{g} packet response.
30828 @item qXfer:auxv:read
30829 The remote stub understands the @samp{qXfer:auxv:read} packet
30830 (@pxref{qXfer auxiliary vector read}).
30832 @item qXfer:features:read
30833 The remote stub understands the @samp{qXfer:features:read} packet
30834 (@pxref{qXfer target description read}).
30836 @item qXfer:libraries:read
30837 The remote stub understands the @samp{qXfer:libraries:read} packet
30838 (@pxref{qXfer library list read}).
30840 @item qXfer:memory-map:read
30841 The remote stub understands the @samp{qXfer:memory-map:read} packet
30842 (@pxref{qXfer memory map read}).
30844 @item qXfer:spu:read
30845 The remote stub understands the @samp{qXfer:spu:read} packet
30846 (@pxref{qXfer spu read}).
30848 @item qXfer:spu:write
30849 The remote stub understands the @samp{qXfer:spu:write} packet
30850 (@pxref{qXfer spu write}).
30852 @item qXfer:siginfo:read
30853 The remote stub understands the @samp{qXfer:siginfo:read} packet
30854 (@pxref{qXfer siginfo read}).
30856 @item qXfer:siginfo:write
30857 The remote stub understands the @samp{qXfer:siginfo:write} packet
30858 (@pxref{qXfer siginfo write}).
30860 @item qXfer:threads:read
30861 The remote stub understands the @samp{qXfer:threads:read} packet
30862 (@pxref{qXfer threads read}).
30865 The remote stub understands the @samp{QNonStop} packet
30866 (@pxref{QNonStop}).
30869 The remote stub understands the @samp{QPassSignals} packet
30870 (@pxref{QPassSignals}).
30872 @item QStartNoAckMode
30873 The remote stub understands the @samp{QStartNoAckMode} packet and
30874 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
30877 @anchor{multiprocess extensions}
30878 @cindex multiprocess extensions, in remote protocol
30879 The remote stub understands the multiprocess extensions to the remote
30880 protocol syntax. The multiprocess extensions affect the syntax of
30881 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
30882 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
30883 replies. Note that reporting this feature indicates support for the
30884 syntactic extensions only, not that the stub necessarily supports
30885 debugging of more than one process at a time. The stub must not use
30886 multiprocess extensions in packet replies unless @value{GDBN} has also
30887 indicated it supports them in its @samp{qSupported} request.
30889 @item qXfer:osdata:read
30890 The remote stub understands the @samp{qXfer:osdata:read} packet
30891 ((@pxref{qXfer osdata read}).
30893 @item ConditionalTracepoints
30894 The remote stub accepts and implements conditional expressions defined
30895 for tracepoints (@pxref{Tracepoint Conditions}).
30897 @item ReverseContinue
30898 The remote stub accepts and implements the reverse continue packet
30902 The remote stub accepts and implements the reverse step packet
30905 @item TracepointSource
30906 The remote stub understands the @samp{QTDPsrc} packet that supplies
30907 the source form of tracepoint definitions.
30912 @cindex symbol lookup, remote request
30913 @cindex @samp{qSymbol} packet
30914 Notify the target that @value{GDBN} is prepared to serve symbol lookup
30915 requests. Accept requests from the target for the values of symbols.
30920 The target does not need to look up any (more) symbols.
30921 @item qSymbol:@var{sym_name}
30922 The target requests the value of symbol @var{sym_name} (hex encoded).
30923 @value{GDBN} may provide the value by using the
30924 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
30928 @item qSymbol:@var{sym_value}:@var{sym_name}
30929 Set the value of @var{sym_name} to @var{sym_value}.
30931 @var{sym_name} (hex encoded) is the name of a symbol whose value the
30932 target has previously requested.
30934 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
30935 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
30941 The target does not need to look up any (more) symbols.
30942 @item qSymbol:@var{sym_name}
30943 The target requests the value of a new symbol @var{sym_name} (hex
30944 encoded). @value{GDBN} will continue to supply the values of symbols
30945 (if available), until the target ceases to request them.
30950 @item QTDisconnected
30957 @xref{Tracepoint Packets}.
30959 @item qThreadExtraInfo,@var{thread-id}
30960 @cindex thread attributes info, remote request
30961 @cindex @samp{qThreadExtraInfo} packet
30962 Obtain a printable string description of a thread's attributes from
30963 the target OS. @var{thread-id} is a thread ID;
30964 see @ref{thread-id syntax}. This
30965 string may contain anything that the target OS thinks is interesting
30966 for @value{GDBN} to tell the user about the thread. The string is
30967 displayed in @value{GDBN}'s @code{info threads} display. Some
30968 examples of possible thread extra info strings are @samp{Runnable}, or
30969 @samp{Blocked on Mutex}.
30973 @item @var{XX}@dots{}
30974 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
30975 comprising the printable string containing the extra information about
30976 the thread's attributes.
30979 (Note that the @code{qThreadExtraInfo} packet's name is separated from
30980 the command by a @samp{,}, not a @samp{:}, contrary to the naming
30981 conventions above. Please don't use this packet as a model for new
30993 @xref{Tracepoint Packets}.
30995 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
30996 @cindex read special object, remote request
30997 @cindex @samp{qXfer} packet
30998 @anchor{qXfer read}
30999 Read uninterpreted bytes from the target's special data area
31000 identified by the keyword @var{object}. Request @var{length} bytes
31001 starting at @var{offset} bytes into the data. The content and
31002 encoding of @var{annex} is specific to @var{object}; it can supply
31003 additional details about what data to access.
31005 Here are the specific requests of this form defined so far. All
31006 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
31007 formats, listed below.
31010 @item qXfer:auxv:read::@var{offset},@var{length}
31011 @anchor{qXfer auxiliary vector read}
31012 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
31013 auxiliary vector}. Note @var{annex} must be empty.
31015 This packet is not probed by default; the remote stub must request it,
31016 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31018 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
31019 @anchor{qXfer target description read}
31020 Access the @dfn{target description}. @xref{Target Descriptions}. The
31021 annex specifies which XML document to access. The main description is
31022 always loaded from the @samp{target.xml} annex.
31024 This packet is not probed by default; the remote stub must request it,
31025 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31027 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
31028 @anchor{qXfer library list read}
31029 Access the target's list of loaded libraries. @xref{Library List Format}.
31030 The annex part of the generic @samp{qXfer} packet must be empty
31031 (@pxref{qXfer read}).
31033 Targets which maintain a list of libraries in the program's memory do
31034 not need to implement this packet; it is designed for platforms where
31035 the operating system manages the list of loaded libraries.
31037 This packet is not probed by default; the remote stub must request it,
31038 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31040 @item qXfer:memory-map:read::@var{offset},@var{length}
31041 @anchor{qXfer memory map read}
31042 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
31043 annex part of the generic @samp{qXfer} packet must be empty
31044 (@pxref{qXfer read}).
31046 This packet is not probed by default; the remote stub must request it,
31047 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31049 @item qXfer:siginfo:read::@var{offset},@var{length}
31050 @anchor{qXfer siginfo read}
31051 Read contents of the extra signal information on the target
31052 system. The annex part of the generic @samp{qXfer} packet must be
31053 empty (@pxref{qXfer read}).
31055 This packet is not probed by default; the remote stub must request it,
31056 by supplying an appropriate @samp{qSupported} response
31057 (@pxref{qSupported}).
31059 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
31060 @anchor{qXfer spu read}
31061 Read contents of an @code{spufs} file on the target system. The
31062 annex specifies which file to read; it must be of the form
31063 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
31064 in the target process, and @var{name} identifes the @code{spufs} file
31065 in that context to be accessed.
31067 This packet is not probed by default; the remote stub must request it,
31068 by supplying an appropriate @samp{qSupported} response
31069 (@pxref{qSupported}).
31071 @item qXfer:threads:read::@var{offset},@var{length}
31072 @anchor{qXfer threads read}
31073 Access the list of threads on target. @xref{Thread List Format}. The
31074 annex part of the generic @samp{qXfer} packet must be empty
31075 (@pxref{qXfer read}).
31077 This packet is not probed by default; the remote stub must request it,
31078 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31080 @item qXfer:osdata:read::@var{offset},@var{length}
31081 @anchor{qXfer osdata read}
31082 Access the target's @dfn{operating system information}.
31083 @xref{Operating System Information}.
31090 Data @var{data} (@pxref{Binary Data}) has been read from the
31091 target. There may be more data at a higher address (although
31092 it is permitted to return @samp{m} even for the last valid
31093 block of data, as long as at least one byte of data was read).
31094 @var{data} may have fewer bytes than the @var{length} in the
31098 Data @var{data} (@pxref{Binary Data}) has been read from the target.
31099 There is no more data to be read. @var{data} may have fewer bytes
31100 than the @var{length} in the request.
31103 The @var{offset} in the request is at the end of the data.
31104 There is no more data to be read.
31107 The request was malformed, or @var{annex} was invalid.
31110 The offset was invalid, or there was an error encountered reading the data.
31111 @var{nn} is a hex-encoded @code{errno} value.
31114 An empty reply indicates the @var{object} string was not recognized by
31115 the stub, or that the object does not support reading.
31118 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
31119 @cindex write data into object, remote request
31120 @anchor{qXfer write}
31121 Write uninterpreted bytes into the target's special data area
31122 identified by the keyword @var{object}, starting at @var{offset} bytes
31123 into the data. @var{data}@dots{} is the binary-encoded data
31124 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
31125 is specific to @var{object}; it can supply additional details about what data
31128 Here are the specific requests of this form defined so far. All
31129 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
31130 formats, listed below.
31133 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
31134 @anchor{qXfer siginfo write}
31135 Write @var{data} to the extra signal information on the target system.
31136 The annex part of the generic @samp{qXfer} packet must be
31137 empty (@pxref{qXfer write}).
31139 This packet is not probed by default; the remote stub must request it,
31140 by supplying an appropriate @samp{qSupported} response
31141 (@pxref{qSupported}).
31143 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
31144 @anchor{qXfer spu write}
31145 Write @var{data} to an @code{spufs} file on the target system. The
31146 annex specifies which file to write; it must be of the form
31147 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
31148 in the target process, and @var{name} identifes the @code{spufs} file
31149 in that context to be accessed.
31151 This packet is not probed by default; the remote stub must request it,
31152 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31158 @var{nn} (hex encoded) is the number of bytes written.
31159 This may be fewer bytes than supplied in the request.
31162 The request was malformed, or @var{annex} was invalid.
31165 The offset was invalid, or there was an error encountered writing the data.
31166 @var{nn} is a hex-encoded @code{errno} value.
31169 An empty reply indicates the @var{object} string was not
31170 recognized by the stub, or that the object does not support writing.
31173 @item qXfer:@var{object}:@var{operation}:@dots{}
31174 Requests of this form may be added in the future. When a stub does
31175 not recognize the @var{object} keyword, or its support for
31176 @var{object} does not recognize the @var{operation} keyword, the stub
31177 must respond with an empty packet.
31179 @item qAttached:@var{pid}
31180 @cindex query attached, remote request
31181 @cindex @samp{qAttached} packet
31182 Return an indication of whether the remote server attached to an
31183 existing process or created a new process. When the multiprocess
31184 protocol extensions are supported (@pxref{multiprocess extensions}),
31185 @var{pid} is an integer in hexadecimal format identifying the target
31186 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
31187 the query packet will be simplified as @samp{qAttached}.
31189 This query is used, for example, to know whether the remote process
31190 should be detached or killed when a @value{GDBN} session is ended with
31191 the @code{quit} command.
31196 The remote server attached to an existing process.
31198 The remote server created a new process.
31200 A badly formed request or an error was encountered.
31205 @node Architecture-Specific Protocol Details
31206 @section Architecture-Specific Protocol Details
31208 This section describes how the remote protocol is applied to specific
31209 target architectures. Also see @ref{Standard Target Features}, for
31210 details of XML target descriptions for each architecture.
31214 @subsubsection Breakpoint Kinds
31216 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
31221 16-bit Thumb mode breakpoint.
31224 32-bit Thumb mode (Thumb-2) breakpoint.
31227 32-bit ARM mode breakpoint.
31233 @subsubsection Register Packet Format
31235 The following @code{g}/@code{G} packets have previously been defined.
31236 In the below, some thirty-two bit registers are transferred as
31237 sixty-four bits. Those registers should be zero/sign extended (which?)
31238 to fill the space allocated. Register bytes are transferred in target
31239 byte order. The two nibbles within a register byte are transferred
31240 most-significant - least-significant.
31246 All registers are transferred as thirty-two bit quantities in the order:
31247 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
31248 registers; fsr; fir; fp.
31252 All registers are transferred as sixty-four bit quantities (including
31253 thirty-two bit registers such as @code{sr}). The ordering is the same
31258 @node Tracepoint Packets
31259 @section Tracepoint Packets
31260 @cindex tracepoint packets
31261 @cindex packets, tracepoint
31263 Here we describe the packets @value{GDBN} uses to implement
31264 tracepoints (@pxref{Tracepoints}).
31268 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
31269 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
31270 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
31271 the tracepoint is disabled. @var{step} is the tracepoint's step
31272 count, and @var{pass} is its pass count. If an @samp{F} is present,
31273 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
31274 the number of bytes that the target should copy elsewhere to make room
31275 for the tracepoint. If an @samp{X} is present, it introduces a
31276 tracepoint condition, which consists of a hexadecimal length, followed
31277 by a comma and hex-encoded bytes, in a manner similar to action
31278 encodings as described below. If the trailing @samp{-} is present,
31279 further @samp{QTDP} packets will follow to specify this tracepoint's
31285 The packet was understood and carried out.
31287 The packet was not recognized.
31290 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
31291 Define actions to be taken when a tracepoint is hit. @var{n} and
31292 @var{addr} must be the same as in the initial @samp{QTDP} packet for
31293 this tracepoint. This packet may only be sent immediately after
31294 another @samp{QTDP} packet that ended with a @samp{-}. If the
31295 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
31296 specifying more actions for this tracepoint.
31298 In the series of action packets for a given tracepoint, at most one
31299 can have an @samp{S} before its first @var{action}. If such a packet
31300 is sent, it and the following packets define ``while-stepping''
31301 actions. Any prior packets define ordinary actions --- that is, those
31302 taken when the tracepoint is first hit. If no action packet has an
31303 @samp{S}, then all the packets in the series specify ordinary
31304 tracepoint actions.
31306 The @samp{@var{action}@dots{}} portion of the packet is a series of
31307 actions, concatenated without separators. Each action has one of the
31313 Collect the registers whose bits are set in @var{mask}. @var{mask} is
31314 a hexadecimal number whose @var{i}'th bit is set if register number
31315 @var{i} should be collected. (The least significant bit is numbered
31316 zero.) Note that @var{mask} may be any number of digits long; it may
31317 not fit in a 32-bit word.
31319 @item M @var{basereg},@var{offset},@var{len}
31320 Collect @var{len} bytes of memory starting at the address in register
31321 number @var{basereg}, plus @var{offset}. If @var{basereg} is
31322 @samp{-1}, then the range has a fixed address: @var{offset} is the
31323 address of the lowest byte to collect. The @var{basereg},
31324 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
31325 values (the @samp{-1} value for @var{basereg} is a special case).
31327 @item X @var{len},@var{expr}
31328 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
31329 it directs. @var{expr} is an agent expression, as described in
31330 @ref{Agent Expressions}. Each byte of the expression is encoded as a
31331 two-digit hex number in the packet; @var{len} is the number of bytes
31332 in the expression (and thus one-half the number of hex digits in the
31337 Any number of actions may be packed together in a single @samp{QTDP}
31338 packet, as long as the packet does not exceed the maximum packet
31339 length (400 bytes, for many stubs). There may be only one @samp{R}
31340 action per tracepoint, and it must precede any @samp{M} or @samp{X}
31341 actions. Any registers referred to by @samp{M} and @samp{X} actions
31342 must be collected by a preceding @samp{R} action. (The
31343 ``while-stepping'' actions are treated as if they were attached to a
31344 separate tracepoint, as far as these restrictions are concerned.)
31349 The packet was understood and carried out.
31351 The packet was not recognized.
31354 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
31355 @cindex @samp{QTDPsrc} packet
31356 Specify a source string of tracepoint @var{n} at address @var{addr}.
31357 This is useful to get accurate reproduction of the tracepoints
31358 originally downloaded at the beginning of the trace run. @var{type}
31359 is the name of the tracepoint part, such as @samp{cond} for the
31360 tracepoint's conditional expression (see below for a list of types), while
31361 @var{bytes} is the string, encoded in hexadecimal.
31363 @var{start} is the offset of the @var{bytes} within the overall source
31364 string, while @var{slen} is the total length of the source string.
31365 This is intended for handling source strings that are longer than will
31366 fit in a single packet.
31367 @c Add detailed example when this info is moved into a dedicated
31368 @c tracepoint descriptions section.
31370 The available string types are @samp{at} for the location,
31371 @samp{cond} for the conditional, and @samp{cmd} for an action command.
31372 @value{GDBN} sends a separate packet for each command in the action
31373 list, in the same order in which the commands are stored in the list.
31375 The target does not need to do anything with source strings except
31376 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
31379 Although this packet is optional, and @value{GDBN} will only send it
31380 if the target replies with @samp{TracepointSource} @xref{General
31381 Query Packets}, it makes both disconnected tracing and trace files
31382 much easier to use. Otherwise the user must be careful that the
31383 tracepoints in effect while looking at trace frames are identical to
31384 the ones in effect during the trace run; even a small discrepancy
31385 could cause @samp{tdump} not to work, or a particular trace frame not
31388 @item QTDV:@var{n}:@var{value}
31389 @cindex define trace state variable, remote request
31390 @cindex @samp{QTDV} packet
31391 Create a new trace state variable, number @var{n}, with an initial
31392 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
31393 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
31394 the option of not using this packet for initial values of zero; the
31395 target should simply create the trace state variables as they are
31396 mentioned in expressions.
31398 @item QTFrame:@var{n}
31399 Select the @var{n}'th tracepoint frame from the buffer, and use the
31400 register and memory contents recorded there to answer subsequent
31401 request packets from @value{GDBN}.
31403 A successful reply from the stub indicates that the stub has found the
31404 requested frame. The response is a series of parts, concatenated
31405 without separators, describing the frame we selected. Each part has
31406 one of the following forms:
31410 The selected frame is number @var{n} in the trace frame buffer;
31411 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
31412 was no frame matching the criteria in the request packet.
31415 The selected trace frame records a hit of tracepoint number @var{t};
31416 @var{t} is a hexadecimal number.
31420 @item QTFrame:pc:@var{addr}
31421 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
31422 currently selected frame whose PC is @var{addr};
31423 @var{addr} is a hexadecimal number.
31425 @item QTFrame:tdp:@var{t}
31426 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
31427 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
31428 is a hexadecimal number.
31430 @item QTFrame:range:@var{start}:@var{end}
31431 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
31432 currently selected frame whose PC is between @var{start} (inclusive)
31433 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
31436 @item QTFrame:outside:@var{start}:@var{end}
31437 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
31438 frame @emph{outside} the given range of addresses (exclusive).
31441 Begin the tracepoint experiment. Begin collecting data from tracepoint
31442 hits in the trace frame buffer.
31445 End the tracepoint experiment. Stop collecting trace frames.
31448 Clear the table of tracepoints, and empty the trace frame buffer.
31450 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
31451 Establish the given ranges of memory as ``transparent''. The stub
31452 will answer requests for these ranges from memory's current contents,
31453 if they were not collected as part of the tracepoint hit.
31455 @value{GDBN} uses this to mark read-only regions of memory, like those
31456 containing program code. Since these areas never change, they should
31457 still have the same contents they did when the tracepoint was hit, so
31458 there's no reason for the stub to refuse to provide their contents.
31460 @item QTDisconnected:@var{value}
31461 Set the choice to what to do with the tracing run when @value{GDBN}
31462 disconnects from the target. A @var{value} of 1 directs the target to
31463 continue the tracing run, while 0 tells the target to stop tracing if
31464 @value{GDBN} is no longer in the picture.
31467 Ask the stub if there is a trace experiment running right now.
31469 The reply has the form:
31473 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
31474 @var{running} is a single digit @code{1} if the trace is presently
31475 running, or @code{0} if not. It is followed by semicolon-separated
31476 optional fields that an agent may use to report additional status.
31480 If the trace is not running, the agent may report any of several
31481 explanations as one of the optional fields:
31486 No trace has been run yet.
31489 The trace was stopped by a user-originated stop command.
31492 The trace stopped because the trace buffer filled up.
31494 @item tdisconnected:0
31495 The trace stopped because @value{GDBN} disconnected from the target.
31497 @item tpasscount:@var{tpnum}
31498 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
31500 @item terror:@var{text}:@var{tpnum}
31501 The trace stopped because tracepoint @var{tpnum} had an error. The
31502 string @var{text} is available to describe the nature of the error
31503 (for instance, a divide by zero in the condition expression).
31504 @var{text} is hex encoded.
31507 The trace stopped for some other reason.
31511 Additional optional fields supply statistical and other information.
31512 Although not required, they are extremely useful for users monitoring
31513 the progress of a trace run. If a trace has stopped, and these
31514 numbers are reported, they must reflect the state of the just-stopped
31519 @item tframes:@var{n}
31520 The number of trace frames in the buffer.
31522 @item tcreated:@var{n}
31523 The total number of trace frames created during the run. This may
31524 be larger than the trace frame count, if the buffer is circular.
31526 @item tsize:@var{n}
31527 The total size of the trace buffer, in bytes.
31529 @item tfree:@var{n}
31530 The number of bytes still unused in the buffer.
31532 @item circular:@var{n}
31533 The value of the circular trace buffer flag. @code{1} means that the
31534 trace buffer is circular and old trace frames will be discarded if
31535 necessary to make room, @code{0} means that the trace buffer is linear
31538 @item disconn:@var{n}
31539 The value of the disconnected tracing flag. @code{1} means that
31540 tracing will continue after @value{GDBN} disconnects, @code{0} means
31541 that the trace run will stop.
31545 @item qTV:@var{var}
31546 @cindex trace state variable value, remote request
31547 @cindex @samp{qTV} packet
31548 Ask the stub for the value of the trace state variable number @var{var}.
31553 The value of the variable is @var{value}. This will be the current
31554 value of the variable if the user is examining a running target, or a
31555 saved value if the variable was collected in the trace frame that the
31556 user is looking at. Note that multiple requests may result in
31557 different reply values, such as when requesting values while the
31558 program is running.
31561 The value of the variable is unknown. This would occur, for example,
31562 if the user is examining a trace frame in which the requested variable
31568 These packets request data about tracepoints that are being used by
31569 the target. @value{GDBN} sends @code{qTfP} to get the first piece
31570 of data, and multiple @code{qTsP} to get additional pieces. Replies
31571 to these packets generally take the form of the @code{QTDP} packets
31572 that define tracepoints. (FIXME add detailed syntax)
31576 These packets request data about trace state variables that are on the
31577 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
31578 and multiple @code{qTsV} to get additional variables. Replies to
31579 these packets follow the syntax of the @code{QTDV} packets that define
31580 trace state variables.
31582 @item QTSave:@var{filename}
31583 This packet directs the target to save trace data to the file name
31584 @var{filename} in the target's filesystem. @var{filename} is encoded
31585 as a hex string; the interpretation of the file name (relative vs
31586 absolute, wild cards, etc) is up to the target.
31588 @item qTBuffer:@var{offset},@var{len}
31589 Return up to @var{len} bytes of the current contents of trace buffer,
31590 starting at @var{offset}. The trace buffer is treated as if it were
31591 a contiguous collection of traceframes, as per the trace file format.
31592 The reply consists as many hex-encoded bytes as the target can deliver
31593 in a packet; it is not an error to return fewer than were asked for.
31594 A reply consisting of just @code{l} indicates that no bytes are
31597 @item QTBuffer:circular:@var{value}
31598 This packet directs the target to use a circular trace buffer if
31599 @var{value} is 1, or a linear buffer if the value is 0.
31603 @node Host I/O Packets
31604 @section Host I/O Packets
31605 @cindex Host I/O, remote protocol
31606 @cindex file transfer, remote protocol
31608 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
31609 operations on the far side of a remote link. For example, Host I/O is
31610 used to upload and download files to a remote target with its own
31611 filesystem. Host I/O uses the same constant values and data structure
31612 layout as the target-initiated File-I/O protocol. However, the
31613 Host I/O packets are structured differently. The target-initiated
31614 protocol relies on target memory to store parameters and buffers.
31615 Host I/O requests are initiated by @value{GDBN}, and the
31616 target's memory is not involved. @xref{File-I/O Remote Protocol
31617 Extension}, for more details on the target-initiated protocol.
31619 The Host I/O request packets all encode a single operation along with
31620 its arguments. They have this format:
31624 @item vFile:@var{operation}: @var{parameter}@dots{}
31625 @var{operation} is the name of the particular request; the target
31626 should compare the entire packet name up to the second colon when checking
31627 for a supported operation. The format of @var{parameter} depends on
31628 the operation. Numbers are always passed in hexadecimal. Negative
31629 numbers have an explicit minus sign (i.e.@: two's complement is not
31630 used). Strings (e.g.@: filenames) are encoded as a series of
31631 hexadecimal bytes. The last argument to a system call may be a
31632 buffer of escaped binary data (@pxref{Binary Data}).
31636 The valid responses to Host I/O packets are:
31640 @item F @var{result} [, @var{errno}] [; @var{attachment}]
31641 @var{result} is the integer value returned by this operation, usually
31642 non-negative for success and -1 for errors. If an error has occured,
31643 @var{errno} will be included in the result. @var{errno} will have a
31644 value defined by the File-I/O protocol (@pxref{Errno Values}). For
31645 operations which return data, @var{attachment} supplies the data as a
31646 binary buffer. Binary buffers in response packets are escaped in the
31647 normal way (@pxref{Binary Data}). See the individual packet
31648 documentation for the interpretation of @var{result} and
31652 An empty response indicates that this operation is not recognized.
31656 These are the supported Host I/O operations:
31659 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
31660 Open a file at @var{pathname} and return a file descriptor for it, or
31661 return -1 if an error occurs. @var{pathname} is a string,
31662 @var{flags} is an integer indicating a mask of open flags
31663 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
31664 of mode bits to use if the file is created (@pxref{mode_t Values}).
31665 @xref{open}, for details of the open flags and mode values.
31667 @item vFile:close: @var{fd}
31668 Close the open file corresponding to @var{fd} and return 0, or
31669 -1 if an error occurs.
31671 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
31672 Read data from the open file corresponding to @var{fd}. Up to
31673 @var{count} bytes will be read from the file, starting at @var{offset}
31674 relative to the start of the file. The target may read fewer bytes;
31675 common reasons include packet size limits and an end-of-file
31676 condition. The number of bytes read is returned. Zero should only be
31677 returned for a successful read at the end of the file, or if
31678 @var{count} was zero.
31680 The data read should be returned as a binary attachment on success.
31681 If zero bytes were read, the response should include an empty binary
31682 attachment (i.e.@: a trailing semicolon). The return value is the
31683 number of target bytes read; the binary attachment may be longer if
31684 some characters were escaped.
31686 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
31687 Write @var{data} (a binary buffer) to the open file corresponding
31688 to @var{fd}. Start the write at @var{offset} from the start of the
31689 file. Unlike many @code{write} system calls, there is no
31690 separate @var{count} argument; the length of @var{data} in the
31691 packet is used. @samp{vFile:write} returns the number of bytes written,
31692 which may be shorter than the length of @var{data}, or -1 if an
31695 @item vFile:unlink: @var{pathname}
31696 Delete the file at @var{pathname} on the target. Return 0,
31697 or -1 if an error occurs. @var{pathname} is a string.
31702 @section Interrupts
31703 @cindex interrupts (remote protocol)
31705 When a program on the remote target is running, @value{GDBN} may
31706 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
31707 a @code{BREAK} followed by @code{g},
31708 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
31710 The precise meaning of @code{BREAK} is defined by the transport
31711 mechanism and may, in fact, be undefined. @value{GDBN} does not
31712 currently define a @code{BREAK} mechanism for any of the network
31713 interfaces except for TCP, in which case @value{GDBN} sends the
31714 @code{telnet} BREAK sequence.
31716 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
31717 transport mechanisms. It is represented by sending the single byte
31718 @code{0x03} without any of the usual packet overhead described in
31719 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
31720 transmitted as part of a packet, it is considered to be packet data
31721 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
31722 (@pxref{X packet}), used for binary downloads, may include an unescaped
31723 @code{0x03} as part of its packet.
31725 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
31726 When Linux kernel receives this sequence from serial port,
31727 it stops execution and connects to gdb.
31729 Stubs are not required to recognize these interrupt mechanisms and the
31730 precise meaning associated with receipt of the interrupt is
31731 implementation defined. If the target supports debugging of multiple
31732 threads and/or processes, it should attempt to interrupt all
31733 currently-executing threads and processes.
31734 If the stub is successful at interrupting the
31735 running program, it should send one of the stop
31736 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
31737 of successfully stopping the program in all-stop mode, and a stop reply
31738 for each stopped thread in non-stop mode.
31739 Interrupts received while the
31740 program is stopped are discarded.
31742 @node Notification Packets
31743 @section Notification Packets
31744 @cindex notification packets
31745 @cindex packets, notification
31747 The @value{GDBN} remote serial protocol includes @dfn{notifications},
31748 packets that require no acknowledgment. Both the GDB and the stub
31749 may send notifications (although the only notifications defined at
31750 present are sent by the stub). Notifications carry information
31751 without incurring the round-trip latency of an acknowledgment, and so
31752 are useful for low-impact communications where occasional packet loss
31755 A notification packet has the form @samp{% @var{data} #
31756 @var{checksum}}, where @var{data} is the content of the notification,
31757 and @var{checksum} is a checksum of @var{data}, computed and formatted
31758 as for ordinary @value{GDBN} packets. A notification's @var{data}
31759 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
31760 receiving a notification, the recipient sends no @samp{+} or @samp{-}
31761 to acknowledge the notification's receipt or to report its corruption.
31763 Every notification's @var{data} begins with a name, which contains no
31764 colon characters, followed by a colon character.
31766 Recipients should silently ignore corrupted notifications and
31767 notifications they do not understand. Recipients should restart
31768 timeout periods on receipt of a well-formed notification, whether or
31769 not they understand it.
31771 Senders should only send the notifications described here when this
31772 protocol description specifies that they are permitted. In the
31773 future, we may extend the protocol to permit existing notifications in
31774 new contexts; this rule helps older senders avoid confusing newer
31777 (Older versions of @value{GDBN} ignore bytes received until they see
31778 the @samp{$} byte that begins an ordinary packet, so new stubs may
31779 transmit notifications without fear of confusing older clients. There
31780 are no notifications defined for @value{GDBN} to send at the moment, but we
31781 assume that most older stubs would ignore them, as well.)
31783 The following notification packets from the stub to @value{GDBN} are
31787 @item Stop: @var{reply}
31788 Report an asynchronous stop event in non-stop mode.
31789 The @var{reply} has the form of a stop reply, as
31790 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
31791 for information on how these notifications are acknowledged by
31795 @node Remote Non-Stop
31796 @section Remote Protocol Support for Non-Stop Mode
31798 @value{GDBN}'s remote protocol supports non-stop debugging of
31799 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
31800 supports non-stop mode, it should report that to @value{GDBN} by including
31801 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
31803 @value{GDBN} typically sends a @samp{QNonStop} packet only when
31804 establishing a new connection with the stub. Entering non-stop mode
31805 does not alter the state of any currently-running threads, but targets
31806 must stop all threads in any already-attached processes when entering
31807 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
31808 probe the target state after a mode change.
31810 In non-stop mode, when an attached process encounters an event that
31811 would otherwise be reported with a stop reply, it uses the
31812 asynchronous notification mechanism (@pxref{Notification Packets}) to
31813 inform @value{GDBN}. In contrast to all-stop mode, where all threads
31814 in all processes are stopped when a stop reply is sent, in non-stop
31815 mode only the thread reporting the stop event is stopped. That is,
31816 when reporting a @samp{S} or @samp{T} response to indicate completion
31817 of a step operation, hitting a breakpoint, or a fault, only the
31818 affected thread is stopped; any other still-running threads continue
31819 to run. When reporting a @samp{W} or @samp{X} response, all running
31820 threads belonging to other attached processes continue to run.
31822 Only one stop reply notification at a time may be pending; if
31823 additional stop events occur before @value{GDBN} has acknowledged the
31824 previous notification, they must be queued by the stub for later
31825 synchronous transmission in response to @samp{vStopped} packets from
31826 @value{GDBN}. Because the notification mechanism is unreliable,
31827 the stub is permitted to resend a stop reply notification
31828 if it believes @value{GDBN} may not have received it. @value{GDBN}
31829 ignores additional stop reply notifications received before it has
31830 finished processing a previous notification and the stub has completed
31831 sending any queued stop events.
31833 Otherwise, @value{GDBN} must be prepared to receive a stop reply
31834 notification at any time. Specifically, they may appear when
31835 @value{GDBN} is not otherwise reading input from the stub, or when
31836 @value{GDBN} is expecting to read a normal synchronous response or a
31837 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
31838 Notification packets are distinct from any other communication from
31839 the stub so there is no ambiguity.
31841 After receiving a stop reply notification, @value{GDBN} shall
31842 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
31843 as a regular, synchronous request to the stub. Such acknowledgment
31844 is not required to happen immediately, as @value{GDBN} is permitted to
31845 send other, unrelated packets to the stub first, which the stub should
31848 Upon receiving a @samp{vStopped} packet, if the stub has other queued
31849 stop events to report to @value{GDBN}, it shall respond by sending a
31850 normal stop reply response. @value{GDBN} shall then send another
31851 @samp{vStopped} packet to solicit further responses; again, it is
31852 permitted to send other, unrelated packets as well which the stub
31853 should process normally.
31855 If the stub receives a @samp{vStopped} packet and there are no
31856 additional stop events to report, the stub shall return an @samp{OK}
31857 response. At this point, if further stop events occur, the stub shall
31858 send a new stop reply notification, @value{GDBN} shall accept the
31859 notification, and the process shall be repeated.
31861 In non-stop mode, the target shall respond to the @samp{?} packet as
31862 follows. First, any incomplete stop reply notification/@samp{vStopped}
31863 sequence in progress is abandoned. The target must begin a new
31864 sequence reporting stop events for all stopped threads, whether or not
31865 it has previously reported those events to @value{GDBN}. The first
31866 stop reply is sent as a synchronous reply to the @samp{?} packet, and
31867 subsequent stop replies are sent as responses to @samp{vStopped} packets
31868 using the mechanism described above. The target must not send
31869 asynchronous stop reply notifications until the sequence is complete.
31870 If all threads are running when the target receives the @samp{?} packet,
31871 or if the target is not attached to any process, it shall respond
31874 @node Packet Acknowledgment
31875 @section Packet Acknowledgment
31877 @cindex acknowledgment, for @value{GDBN} remote
31878 @cindex packet acknowledgment, for @value{GDBN} remote
31879 By default, when either the host or the target machine receives a packet,
31880 the first response expected is an acknowledgment: either @samp{+} (to indicate
31881 the package was received correctly) or @samp{-} (to request retransmission).
31882 This mechanism allows the @value{GDBN} remote protocol to operate over
31883 unreliable transport mechanisms, such as a serial line.
31885 In cases where the transport mechanism is itself reliable (such as a pipe or
31886 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
31887 It may be desirable to disable them in that case to reduce communication
31888 overhead, or for other reasons. This can be accomplished by means of the
31889 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
31891 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
31892 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
31893 and response format still includes the normal checksum, as described in
31894 @ref{Overview}, but the checksum may be ignored by the receiver.
31896 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
31897 no-acknowledgment mode, it should report that to @value{GDBN}
31898 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
31899 @pxref{qSupported}.
31900 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
31901 disabled via the @code{set remote noack-packet off} command
31902 (@pxref{Remote Configuration}),
31903 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
31904 Only then may the stub actually turn off packet acknowledgments.
31905 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
31906 response, which can be safely ignored by the stub.
31908 Note that @code{set remote noack-packet} command only affects negotiation
31909 between @value{GDBN} and the stub when subsequent connections are made;
31910 it does not affect the protocol acknowledgment state for any current
31912 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
31913 new connection is established,
31914 there is also no protocol request to re-enable the acknowledgments
31915 for the current connection, once disabled.
31920 Example sequence of a target being re-started. Notice how the restart
31921 does not get any direct output:
31926 @emph{target restarts}
31929 <- @code{T001:1234123412341234}
31933 Example sequence of a target being stepped by a single instruction:
31936 -> @code{G1445@dots{}}
31941 <- @code{T001:1234123412341234}
31945 <- @code{1455@dots{}}
31949 @node File-I/O Remote Protocol Extension
31950 @section File-I/O Remote Protocol Extension
31951 @cindex File-I/O remote protocol extension
31954 * File-I/O Overview::
31955 * Protocol Basics::
31956 * The F Request Packet::
31957 * The F Reply Packet::
31958 * The Ctrl-C Message::
31960 * List of Supported Calls::
31961 * Protocol-specific Representation of Datatypes::
31963 * File-I/O Examples::
31966 @node File-I/O Overview
31967 @subsection File-I/O Overview
31968 @cindex file-i/o overview
31970 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
31971 target to use the host's file system and console I/O to perform various
31972 system calls. System calls on the target system are translated into a
31973 remote protocol packet to the host system, which then performs the needed
31974 actions and returns a response packet to the target system.
31975 This simulates file system operations even on targets that lack file systems.
31977 The protocol is defined to be independent of both the host and target systems.
31978 It uses its own internal representation of datatypes and values. Both
31979 @value{GDBN} and the target's @value{GDBN} stub are responsible for
31980 translating the system-dependent value representations into the internal
31981 protocol representations when data is transmitted.
31983 The communication is synchronous. A system call is possible only when
31984 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
31985 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
31986 the target is stopped to allow deterministic access to the target's
31987 memory. Therefore File-I/O is not interruptible by target signals. On
31988 the other hand, it is possible to interrupt File-I/O by a user interrupt
31989 (@samp{Ctrl-C}) within @value{GDBN}.
31991 The target's request to perform a host system call does not finish
31992 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
31993 after finishing the system call, the target returns to continuing the
31994 previous activity (continue, step). No additional continue or step
31995 request from @value{GDBN} is required.
31998 (@value{GDBP}) continue
31999 <- target requests 'system call X'
32000 target is stopped, @value{GDBN} executes system call
32001 -> @value{GDBN} returns result
32002 ... target continues, @value{GDBN} returns to wait for the target
32003 <- target hits breakpoint and sends a Txx packet
32006 The protocol only supports I/O on the console and to regular files on
32007 the host file system. Character or block special devices, pipes,
32008 named pipes, sockets or any other communication method on the host
32009 system are not supported by this protocol.
32011 File I/O is not supported in non-stop mode.
32013 @node Protocol Basics
32014 @subsection Protocol Basics
32015 @cindex protocol basics, file-i/o
32017 The File-I/O protocol uses the @code{F} packet as the request as well
32018 as reply packet. Since a File-I/O system call can only occur when
32019 @value{GDBN} is waiting for a response from the continuing or stepping target,
32020 the File-I/O request is a reply that @value{GDBN} has to expect as a result
32021 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
32022 This @code{F} packet contains all information needed to allow @value{GDBN}
32023 to call the appropriate host system call:
32027 A unique identifier for the requested system call.
32030 All parameters to the system call. Pointers are given as addresses
32031 in the target memory address space. Pointers to strings are given as
32032 pointer/length pair. Numerical values are given as they are.
32033 Numerical control flags are given in a protocol-specific representation.
32037 At this point, @value{GDBN} has to perform the following actions.
32041 If the parameters include pointer values to data needed as input to a
32042 system call, @value{GDBN} requests this data from the target with a
32043 standard @code{m} packet request. This additional communication has to be
32044 expected by the target implementation and is handled as any other @code{m}
32048 @value{GDBN} translates all value from protocol representation to host
32049 representation as needed. Datatypes are coerced into the host types.
32052 @value{GDBN} calls the system call.
32055 It then coerces datatypes back to protocol representation.
32058 If the system call is expected to return data in buffer space specified
32059 by pointer parameters to the call, the data is transmitted to the
32060 target using a @code{M} or @code{X} packet. This packet has to be expected
32061 by the target implementation and is handled as any other @code{M} or @code{X}
32066 Eventually @value{GDBN} replies with another @code{F} packet which contains all
32067 necessary information for the target to continue. This at least contains
32074 @code{errno}, if has been changed by the system call.
32081 After having done the needed type and value coercion, the target continues
32082 the latest continue or step action.
32084 @node The F Request Packet
32085 @subsection The @code{F} Request Packet
32086 @cindex file-i/o request packet
32087 @cindex @code{F} request packet
32089 The @code{F} request packet has the following format:
32092 @item F@var{call-id},@var{parameter@dots{}}
32094 @var{call-id} is the identifier to indicate the host system call to be called.
32095 This is just the name of the function.
32097 @var{parameter@dots{}} are the parameters to the system call.
32098 Parameters are hexadecimal integer values, either the actual values in case
32099 of scalar datatypes, pointers to target buffer space in case of compound
32100 datatypes and unspecified memory areas, or pointer/length pairs in case
32101 of string parameters. These are appended to the @var{call-id} as a
32102 comma-delimited list. All values are transmitted in ASCII
32103 string representation, pointer/length pairs separated by a slash.
32109 @node The F Reply Packet
32110 @subsection The @code{F} Reply Packet
32111 @cindex file-i/o reply packet
32112 @cindex @code{F} reply packet
32114 The @code{F} reply packet has the following format:
32118 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
32120 @var{retcode} is the return code of the system call as hexadecimal value.
32122 @var{errno} is the @code{errno} set by the call, in protocol-specific
32124 This parameter can be omitted if the call was successful.
32126 @var{Ctrl-C flag} is only sent if the user requested a break. In this
32127 case, @var{errno} must be sent as well, even if the call was successful.
32128 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
32135 or, if the call was interrupted before the host call has been performed:
32142 assuming 4 is the protocol-specific representation of @code{EINTR}.
32147 @node The Ctrl-C Message
32148 @subsection The @samp{Ctrl-C} Message
32149 @cindex ctrl-c message, in file-i/o protocol
32151 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
32152 reply packet (@pxref{The F Reply Packet}),
32153 the target should behave as if it had
32154 gotten a break message. The meaning for the target is ``system call
32155 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
32156 (as with a break message) and return to @value{GDBN} with a @code{T02}
32159 It's important for the target to know in which
32160 state the system call was interrupted. There are two possible cases:
32164 The system call hasn't been performed on the host yet.
32167 The system call on the host has been finished.
32171 These two states can be distinguished by the target by the value of the
32172 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
32173 call hasn't been performed. This is equivalent to the @code{EINTR} handling
32174 on POSIX systems. In any other case, the target may presume that the
32175 system call has been finished --- successfully or not --- and should behave
32176 as if the break message arrived right after the system call.
32178 @value{GDBN} must behave reliably. If the system call has not been called
32179 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
32180 @code{errno} in the packet. If the system call on the host has been finished
32181 before the user requests a break, the full action must be finished by
32182 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
32183 The @code{F} packet may only be sent when either nothing has happened
32184 or the full action has been completed.
32187 @subsection Console I/O
32188 @cindex console i/o as part of file-i/o
32190 By default and if not explicitly closed by the target system, the file
32191 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
32192 on the @value{GDBN} console is handled as any other file output operation
32193 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
32194 by @value{GDBN} so that after the target read request from file descriptor
32195 0 all following typing is buffered until either one of the following
32200 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
32202 system call is treated as finished.
32205 The user presses @key{RET}. This is treated as end of input with a trailing
32209 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
32210 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
32214 If the user has typed more characters than fit in the buffer given to
32215 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
32216 either another @code{read(0, @dots{})} is requested by the target, or debugging
32217 is stopped at the user's request.
32220 @node List of Supported Calls
32221 @subsection List of Supported Calls
32222 @cindex list of supported file-i/o calls
32239 @unnumberedsubsubsec open
32240 @cindex open, file-i/o system call
32245 int open(const char *pathname, int flags);
32246 int open(const char *pathname, int flags, mode_t mode);
32250 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
32253 @var{flags} is the bitwise @code{OR} of the following values:
32257 If the file does not exist it will be created. The host
32258 rules apply as far as file ownership and time stamps
32262 When used with @code{O_CREAT}, if the file already exists it is
32263 an error and open() fails.
32266 If the file already exists and the open mode allows
32267 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
32268 truncated to zero length.
32271 The file is opened in append mode.
32274 The file is opened for reading only.
32277 The file is opened for writing only.
32280 The file is opened for reading and writing.
32284 Other bits are silently ignored.
32288 @var{mode} is the bitwise @code{OR} of the following values:
32292 User has read permission.
32295 User has write permission.
32298 Group has read permission.
32301 Group has write permission.
32304 Others have read permission.
32307 Others have write permission.
32311 Other bits are silently ignored.
32314 @item Return value:
32315 @code{open} returns the new file descriptor or -1 if an error
32322 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
32325 @var{pathname} refers to a directory.
32328 The requested access is not allowed.
32331 @var{pathname} was too long.
32334 A directory component in @var{pathname} does not exist.
32337 @var{pathname} refers to a device, pipe, named pipe or socket.
32340 @var{pathname} refers to a file on a read-only filesystem and
32341 write access was requested.
32344 @var{pathname} is an invalid pointer value.
32347 No space on device to create the file.
32350 The process already has the maximum number of files open.
32353 The limit on the total number of files open on the system
32357 The call was interrupted by the user.
32363 @unnumberedsubsubsec close
32364 @cindex close, file-i/o system call
32373 @samp{Fclose,@var{fd}}
32375 @item Return value:
32376 @code{close} returns zero on success, or -1 if an error occurred.
32382 @var{fd} isn't a valid open file descriptor.
32385 The call was interrupted by the user.
32391 @unnumberedsubsubsec read
32392 @cindex read, file-i/o system call
32397 int read(int fd, void *buf, unsigned int count);
32401 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
32403 @item Return value:
32404 On success, the number of bytes read is returned.
32405 Zero indicates end of file. If count is zero, read
32406 returns zero as well. On error, -1 is returned.
32412 @var{fd} is not a valid file descriptor or is not open for
32416 @var{bufptr} is an invalid pointer value.
32419 The call was interrupted by the user.
32425 @unnumberedsubsubsec write
32426 @cindex write, file-i/o system call
32431 int write(int fd, const void *buf, unsigned int count);
32435 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
32437 @item Return value:
32438 On success, the number of bytes written are returned.
32439 Zero indicates nothing was written. On error, -1
32446 @var{fd} is not a valid file descriptor or is not open for
32450 @var{bufptr} is an invalid pointer value.
32453 An attempt was made to write a file that exceeds the
32454 host-specific maximum file size allowed.
32457 No space on device to write the data.
32460 The call was interrupted by the user.
32466 @unnumberedsubsubsec lseek
32467 @cindex lseek, file-i/o system call
32472 long lseek (int fd, long offset, int flag);
32476 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
32478 @var{flag} is one of:
32482 The offset is set to @var{offset} bytes.
32485 The offset is set to its current location plus @var{offset}
32489 The offset is set to the size of the file plus @var{offset}
32493 @item Return value:
32494 On success, the resulting unsigned offset in bytes from
32495 the beginning of the file is returned. Otherwise, a
32496 value of -1 is returned.
32502 @var{fd} is not a valid open file descriptor.
32505 @var{fd} is associated with the @value{GDBN} console.
32508 @var{flag} is not a proper value.
32511 The call was interrupted by the user.
32517 @unnumberedsubsubsec rename
32518 @cindex rename, file-i/o system call
32523 int rename(const char *oldpath, const char *newpath);
32527 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
32529 @item Return value:
32530 On success, zero is returned. On error, -1 is returned.
32536 @var{newpath} is an existing directory, but @var{oldpath} is not a
32540 @var{newpath} is a non-empty directory.
32543 @var{oldpath} or @var{newpath} is a directory that is in use by some
32547 An attempt was made to make a directory a subdirectory
32551 A component used as a directory in @var{oldpath} or new
32552 path is not a directory. Or @var{oldpath} is a directory
32553 and @var{newpath} exists but is not a directory.
32556 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
32559 No access to the file or the path of the file.
32563 @var{oldpath} or @var{newpath} was too long.
32566 A directory component in @var{oldpath} or @var{newpath} does not exist.
32569 The file is on a read-only filesystem.
32572 The device containing the file has no room for the new
32576 The call was interrupted by the user.
32582 @unnumberedsubsubsec unlink
32583 @cindex unlink, file-i/o system call
32588 int unlink(const char *pathname);
32592 @samp{Funlink,@var{pathnameptr}/@var{len}}
32594 @item Return value:
32595 On success, zero is returned. On error, -1 is returned.
32601 No access to the file or the path of the file.
32604 The system does not allow unlinking of directories.
32607 The file @var{pathname} cannot be unlinked because it's
32608 being used by another process.
32611 @var{pathnameptr} is an invalid pointer value.
32614 @var{pathname} was too long.
32617 A directory component in @var{pathname} does not exist.
32620 A component of the path is not a directory.
32623 The file is on a read-only filesystem.
32626 The call was interrupted by the user.
32632 @unnumberedsubsubsec stat/fstat
32633 @cindex fstat, file-i/o system call
32634 @cindex stat, file-i/o system call
32639 int stat(const char *pathname, struct stat *buf);
32640 int fstat(int fd, struct stat *buf);
32644 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
32645 @samp{Ffstat,@var{fd},@var{bufptr}}
32647 @item Return value:
32648 On success, zero is returned. On error, -1 is returned.
32654 @var{fd} is not a valid open file.
32657 A directory component in @var{pathname} does not exist or the
32658 path is an empty string.
32661 A component of the path is not a directory.
32664 @var{pathnameptr} is an invalid pointer value.
32667 No access to the file or the path of the file.
32670 @var{pathname} was too long.
32673 The call was interrupted by the user.
32679 @unnumberedsubsubsec gettimeofday
32680 @cindex gettimeofday, file-i/o system call
32685 int gettimeofday(struct timeval *tv, void *tz);
32689 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
32691 @item Return value:
32692 On success, 0 is returned, -1 otherwise.
32698 @var{tz} is a non-NULL pointer.
32701 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
32707 @unnumberedsubsubsec isatty
32708 @cindex isatty, file-i/o system call
32713 int isatty(int fd);
32717 @samp{Fisatty,@var{fd}}
32719 @item Return value:
32720 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
32726 The call was interrupted by the user.
32731 Note that the @code{isatty} call is treated as a special case: it returns
32732 1 to the target if the file descriptor is attached
32733 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
32734 would require implementing @code{ioctl} and would be more complex than
32739 @unnumberedsubsubsec system
32740 @cindex system, file-i/o system call
32745 int system(const char *command);
32749 @samp{Fsystem,@var{commandptr}/@var{len}}
32751 @item Return value:
32752 If @var{len} is zero, the return value indicates whether a shell is
32753 available. A zero return value indicates a shell is not available.
32754 For non-zero @var{len}, the value returned is -1 on error and the
32755 return status of the command otherwise. Only the exit status of the
32756 command is returned, which is extracted from the host's @code{system}
32757 return value by calling @code{WEXITSTATUS(retval)}. In case
32758 @file{/bin/sh} could not be executed, 127 is returned.
32764 The call was interrupted by the user.
32769 @value{GDBN} takes over the full task of calling the necessary host calls
32770 to perform the @code{system} call. The return value of @code{system} on
32771 the host is simplified before it's returned
32772 to the target. Any termination signal information from the child process
32773 is discarded, and the return value consists
32774 entirely of the exit status of the called command.
32776 Due to security concerns, the @code{system} call is by default refused
32777 by @value{GDBN}. The user has to allow this call explicitly with the
32778 @code{set remote system-call-allowed 1} command.
32781 @item set remote system-call-allowed
32782 @kindex set remote system-call-allowed
32783 Control whether to allow the @code{system} calls in the File I/O
32784 protocol for the remote target. The default is zero (disabled).
32786 @item show remote system-call-allowed
32787 @kindex show remote system-call-allowed
32788 Show whether the @code{system} calls are allowed in the File I/O
32792 @node Protocol-specific Representation of Datatypes
32793 @subsection Protocol-specific Representation of Datatypes
32794 @cindex protocol-specific representation of datatypes, in file-i/o protocol
32797 * Integral Datatypes::
32799 * Memory Transfer::
32804 @node Integral Datatypes
32805 @unnumberedsubsubsec Integral Datatypes
32806 @cindex integral datatypes, in file-i/o protocol
32808 The integral datatypes used in the system calls are @code{int},
32809 @code{unsigned int}, @code{long}, @code{unsigned long},
32810 @code{mode_t}, and @code{time_t}.
32812 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
32813 implemented as 32 bit values in this protocol.
32815 @code{long} and @code{unsigned long} are implemented as 64 bit types.
32817 @xref{Limits}, for corresponding MIN and MAX values (similar to those
32818 in @file{limits.h}) to allow range checking on host and target.
32820 @code{time_t} datatypes are defined as seconds since the Epoch.
32822 All integral datatypes transferred as part of a memory read or write of a
32823 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
32826 @node Pointer Values
32827 @unnumberedsubsubsec Pointer Values
32828 @cindex pointer values, in file-i/o protocol
32830 Pointers to target data are transmitted as they are. An exception
32831 is made for pointers to buffers for which the length isn't
32832 transmitted as part of the function call, namely strings. Strings
32833 are transmitted as a pointer/length pair, both as hex values, e.g.@:
32840 which is a pointer to data of length 18 bytes at position 0x1aaf.
32841 The length is defined as the full string length in bytes, including
32842 the trailing null byte. For example, the string @code{"hello world"}
32843 at address 0x123456 is transmitted as
32849 @node Memory Transfer
32850 @unnumberedsubsubsec Memory Transfer
32851 @cindex memory transfer, in file-i/o protocol
32853 Structured data which is transferred using a memory read or write (for
32854 example, a @code{struct stat}) is expected to be in a protocol-specific format
32855 with all scalar multibyte datatypes being big endian. Translation to
32856 this representation needs to be done both by the target before the @code{F}
32857 packet is sent, and by @value{GDBN} before
32858 it transfers memory to the target. Transferred pointers to structured
32859 data should point to the already-coerced data at any time.
32863 @unnumberedsubsubsec struct stat
32864 @cindex struct stat, in file-i/o protocol
32866 The buffer of type @code{struct stat} used by the target and @value{GDBN}
32867 is defined as follows:
32871 unsigned int st_dev; /* device */
32872 unsigned int st_ino; /* inode */
32873 mode_t st_mode; /* protection */
32874 unsigned int st_nlink; /* number of hard links */
32875 unsigned int st_uid; /* user ID of owner */
32876 unsigned int st_gid; /* group ID of owner */
32877 unsigned int st_rdev; /* device type (if inode device) */
32878 unsigned long st_size; /* total size, in bytes */
32879 unsigned long st_blksize; /* blocksize for filesystem I/O */
32880 unsigned long st_blocks; /* number of blocks allocated */
32881 time_t st_atime; /* time of last access */
32882 time_t st_mtime; /* time of last modification */
32883 time_t st_ctime; /* time of last change */
32887 The integral datatypes conform to the definitions given in the
32888 appropriate section (see @ref{Integral Datatypes}, for details) so this
32889 structure is of size 64 bytes.
32891 The values of several fields have a restricted meaning and/or
32897 A value of 0 represents a file, 1 the console.
32900 No valid meaning for the target. Transmitted unchanged.
32903 Valid mode bits are described in @ref{Constants}. Any other
32904 bits have currently no meaning for the target.
32909 No valid meaning for the target. Transmitted unchanged.
32914 These values have a host and file system dependent
32915 accuracy. Especially on Windows hosts, the file system may not
32916 support exact timing values.
32919 The target gets a @code{struct stat} of the above representation and is
32920 responsible for coercing it to the target representation before
32923 Note that due to size differences between the host, target, and protocol
32924 representations of @code{struct stat} members, these members could eventually
32925 get truncated on the target.
32927 @node struct timeval
32928 @unnumberedsubsubsec struct timeval
32929 @cindex struct timeval, in file-i/o protocol
32931 The buffer of type @code{struct timeval} used by the File-I/O protocol
32932 is defined as follows:
32936 time_t tv_sec; /* second */
32937 long tv_usec; /* microsecond */
32941 The integral datatypes conform to the definitions given in the
32942 appropriate section (see @ref{Integral Datatypes}, for details) so this
32943 structure is of size 8 bytes.
32946 @subsection Constants
32947 @cindex constants, in file-i/o protocol
32949 The following values are used for the constants inside of the
32950 protocol. @value{GDBN} and target are responsible for translating these
32951 values before and after the call as needed.
32962 @unnumberedsubsubsec Open Flags
32963 @cindex open flags, in file-i/o protocol
32965 All values are given in hexadecimal representation.
32977 @node mode_t Values
32978 @unnumberedsubsubsec mode_t Values
32979 @cindex mode_t values, in file-i/o protocol
32981 All values are given in octal representation.
32998 @unnumberedsubsubsec Errno Values
32999 @cindex errno values, in file-i/o protocol
33001 All values are given in decimal representation.
33026 @code{EUNKNOWN} is used as a fallback error value if a host system returns
33027 any error value not in the list of supported error numbers.
33030 @unnumberedsubsubsec Lseek Flags
33031 @cindex lseek flags, in file-i/o protocol
33040 @unnumberedsubsubsec Limits
33041 @cindex limits, in file-i/o protocol
33043 All values are given in decimal representation.
33046 INT_MIN -2147483648
33048 UINT_MAX 4294967295
33049 LONG_MIN -9223372036854775808
33050 LONG_MAX 9223372036854775807
33051 ULONG_MAX 18446744073709551615
33054 @node File-I/O Examples
33055 @subsection File-I/O Examples
33056 @cindex file-i/o examples
33058 Example sequence of a write call, file descriptor 3, buffer is at target
33059 address 0x1234, 6 bytes should be written:
33062 <- @code{Fwrite,3,1234,6}
33063 @emph{request memory read from target}
33066 @emph{return "6 bytes written"}
33070 Example sequence of a read call, file descriptor 3, buffer is at target
33071 address 0x1234, 6 bytes should be read:
33074 <- @code{Fread,3,1234,6}
33075 @emph{request memory write to target}
33076 -> @code{X1234,6:XXXXXX}
33077 @emph{return "6 bytes read"}
33081 Example sequence of a read call, call fails on the host due to invalid
33082 file descriptor (@code{EBADF}):
33085 <- @code{Fread,3,1234,6}
33089 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
33093 <- @code{Fread,3,1234,6}
33098 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
33102 <- @code{Fread,3,1234,6}
33103 -> @code{X1234,6:XXXXXX}
33107 @node Library List Format
33108 @section Library List Format
33109 @cindex library list format, remote protocol
33111 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
33112 same process as your application to manage libraries. In this case,
33113 @value{GDBN} can use the loader's symbol table and normal memory
33114 operations to maintain a list of shared libraries. On other
33115 platforms, the operating system manages loaded libraries.
33116 @value{GDBN} can not retrieve the list of currently loaded libraries
33117 through memory operations, so it uses the @samp{qXfer:libraries:read}
33118 packet (@pxref{qXfer library list read}) instead. The remote stub
33119 queries the target's operating system and reports which libraries
33122 The @samp{qXfer:libraries:read} packet returns an XML document which
33123 lists loaded libraries and their offsets. Each library has an
33124 associated name and one or more segment or section base addresses,
33125 which report where the library was loaded in memory.
33127 For the common case of libraries that are fully linked binaries, the
33128 library should have a list of segments. If the target supports
33129 dynamic linking of a relocatable object file, its library XML element
33130 should instead include a list of allocated sections. The segment or
33131 section bases are start addresses, not relocation offsets; they do not
33132 depend on the library's link-time base addresses.
33134 @value{GDBN} must be linked with the Expat library to support XML
33135 library lists. @xref{Expat}.
33137 A simple memory map, with one loaded library relocated by a single
33138 offset, looks like this:
33142 <library name="/lib/libc.so.6">
33143 <segment address="0x10000000"/>
33148 Another simple memory map, with one loaded library with three
33149 allocated sections (.text, .data, .bss), looks like this:
33153 <library name="sharedlib.o">
33154 <section address="0x10000000"/>
33155 <section address="0x20000000"/>
33156 <section address="0x30000000"/>
33161 The format of a library list is described by this DTD:
33164 <!-- library-list: Root element with versioning -->
33165 <!ELEMENT library-list (library)*>
33166 <!ATTLIST library-list version CDATA #FIXED "1.0">
33167 <!ELEMENT library (segment*, section*)>
33168 <!ATTLIST library name CDATA #REQUIRED>
33169 <!ELEMENT segment EMPTY>
33170 <!ATTLIST segment address CDATA #REQUIRED>
33171 <!ELEMENT section EMPTY>
33172 <!ATTLIST section address CDATA #REQUIRED>
33175 In addition, segments and section descriptors cannot be mixed within a
33176 single library element, and you must supply at least one segment or
33177 section for each library.
33179 @node Memory Map Format
33180 @section Memory Map Format
33181 @cindex memory map format
33183 To be able to write into flash memory, @value{GDBN} needs to obtain a
33184 memory map from the target. This section describes the format of the
33187 The memory map is obtained using the @samp{qXfer:memory-map:read}
33188 (@pxref{qXfer memory map read}) packet and is an XML document that
33189 lists memory regions.
33191 @value{GDBN} must be linked with the Expat library to support XML
33192 memory maps. @xref{Expat}.
33194 The top-level structure of the document is shown below:
33197 <?xml version="1.0"?>
33198 <!DOCTYPE memory-map
33199 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
33200 "http://sourceware.org/gdb/gdb-memory-map.dtd">
33206 Each region can be either:
33211 A region of RAM starting at @var{addr} and extending for @var{length}
33215 <memory type="ram" start="@var{addr}" length="@var{length}"/>
33220 A region of read-only memory:
33223 <memory type="rom" start="@var{addr}" length="@var{length}"/>
33228 A region of flash memory, with erasure blocks @var{blocksize}
33232 <memory type="flash" start="@var{addr}" length="@var{length}">
33233 <property name="blocksize">@var{blocksize}</property>
33239 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
33240 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
33241 packets to write to addresses in such ranges.
33243 The formal DTD for memory map format is given below:
33246 <!-- ................................................... -->
33247 <!-- Memory Map XML DTD ................................ -->
33248 <!-- File: memory-map.dtd .............................. -->
33249 <!-- .................................... .............. -->
33250 <!-- memory-map.dtd -->
33251 <!-- memory-map: Root element with versioning -->
33252 <!ELEMENT memory-map (memory | property)>
33253 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
33254 <!ELEMENT memory (property)>
33255 <!-- memory: Specifies a memory region,
33256 and its type, or device. -->
33257 <!ATTLIST memory type CDATA #REQUIRED
33258 start CDATA #REQUIRED
33259 length CDATA #REQUIRED
33260 device CDATA #IMPLIED>
33261 <!-- property: Generic attribute tag -->
33262 <!ELEMENT property (#PCDATA | property)*>
33263 <!ATTLIST property name CDATA #REQUIRED>
33266 @node Thread List Format
33267 @section Thread List Format
33268 @cindex thread list format
33270 To efficiently update the list of threads and their attributes,
33271 @value{GDBN} issues the @samp{qXfer:threads:read} packet
33272 (@pxref{qXfer threads read}) and obtains the XML document with
33273 the following structure:
33276 <?xml version="1.0"?>
33278 <thread id="id" core="0">
33279 ... description ...
33284 Each @samp{thread} element must have the @samp{id} attribute that
33285 identifies the thread (@pxref{thread-id syntax}). The
33286 @samp{core} attribute, if present, specifies which processor core
33287 the thread was last executing on. The content of the of @samp{thread}
33288 element is interpreted as human-readable auxilliary information.
33290 @include agentexpr.texi
33292 @node Trace File Format
33293 @appendix Trace File Format
33294 @cindex trace file format
33296 The trace file comes in three parts: a header, a textual description
33297 section, and a trace frame section with binary data.
33299 The header has the form @code{\x7fTRACE0\n}. The first byte is
33300 @code{0x7f} so as to indicate that the file contains binary data,
33301 while the @code{0} is a version number that may have different values
33304 The description section consists of multiple lines of @sc{ascii} text
33305 separated by newline characters (@code{0xa}). The lines may include a
33306 variety of optional descriptive or context-setting information, such
33307 as tracepoint definitions or register set size. @value{GDBN} will
33308 ignore any line that it does not recognize. An empty line marks the end
33311 @c FIXME add some specific types of data
33313 The trace frame section consists of a number of consecutive frames.
33314 Each frame begins with a two-byte tracepoint number, followed by a
33315 four-byte size giving the amount of data in the frame. The data in
33316 the frame consists of a number of blocks, each introduced by a
33317 character indicating its type (at least register, memory, and trace
33318 state variable). The data in this section is raw binary, not a
33319 hexadecimal or other encoding; its endianness matches the target's
33322 @c FIXME bi-arch may require endianness/arch info in description section
33325 @item R @var{bytes}
33326 Register block. The number and ordering of bytes matches that of a
33327 @code{g} packet in the remote protocol. Note that these are the
33328 actual bytes, in target order and @value{GDBN} register order, not a
33329 hexadecimal encoding.
33331 @item M @var{address} @var{length} @var{bytes}...
33332 Memory block. This is a contiguous block of memory, at the 8-byte
33333 address @var{address}, with a 2-byte length @var{length}, followed by
33334 @var{length} bytes.
33336 @item V @var{number} @var{value}
33337 Trace state variable block. This records the 8-byte signed value
33338 @var{value} of trace state variable numbered @var{number}.
33342 Future enhancements of the trace file format may include additional types
33345 @node Target Descriptions
33346 @appendix Target Descriptions
33347 @cindex target descriptions
33349 @strong{Warning:} target descriptions are still under active development,
33350 and the contents and format may change between @value{GDBN} releases.
33351 The format is expected to stabilize in the future.
33353 One of the challenges of using @value{GDBN} to debug embedded systems
33354 is that there are so many minor variants of each processor
33355 architecture in use. It is common practice for vendors to start with
33356 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
33357 and then make changes to adapt it to a particular market niche. Some
33358 architectures have hundreds of variants, available from dozens of
33359 vendors. This leads to a number of problems:
33363 With so many different customized processors, it is difficult for
33364 the @value{GDBN} maintainers to keep up with the changes.
33366 Since individual variants may have short lifetimes or limited
33367 audiences, it may not be worthwhile to carry information about every
33368 variant in the @value{GDBN} source tree.
33370 When @value{GDBN} does support the architecture of the embedded system
33371 at hand, the task of finding the correct architecture name to give the
33372 @command{set architecture} command can be error-prone.
33375 To address these problems, the @value{GDBN} remote protocol allows a
33376 target system to not only identify itself to @value{GDBN}, but to
33377 actually describe its own features. This lets @value{GDBN} support
33378 processor variants it has never seen before --- to the extent that the
33379 descriptions are accurate, and that @value{GDBN} understands them.
33381 @value{GDBN} must be linked with the Expat library to support XML
33382 target descriptions. @xref{Expat}.
33385 * Retrieving Descriptions:: How descriptions are fetched from a target.
33386 * Target Description Format:: The contents of a target description.
33387 * Predefined Target Types:: Standard types available for target
33389 * Standard Target Features:: Features @value{GDBN} knows about.
33392 @node Retrieving Descriptions
33393 @section Retrieving Descriptions
33395 Target descriptions can be read from the target automatically, or
33396 specified by the user manually. The default behavior is to read the
33397 description from the target. @value{GDBN} retrieves it via the remote
33398 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
33399 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
33400 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
33401 XML document, of the form described in @ref{Target Description
33404 Alternatively, you can specify a file to read for the target description.
33405 If a file is set, the target will not be queried. The commands to
33406 specify a file are:
33409 @cindex set tdesc filename
33410 @item set tdesc filename @var{path}
33411 Read the target description from @var{path}.
33413 @cindex unset tdesc filename
33414 @item unset tdesc filename
33415 Do not read the XML target description from a file. @value{GDBN}
33416 will use the description supplied by the current target.
33418 @cindex show tdesc filename
33419 @item show tdesc filename
33420 Show the filename to read for a target description, if any.
33424 @node Target Description Format
33425 @section Target Description Format
33426 @cindex target descriptions, XML format
33428 A target description annex is an @uref{http://www.w3.org/XML/, XML}
33429 document which complies with the Document Type Definition provided in
33430 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
33431 means you can use generally available tools like @command{xmllint} to
33432 check that your feature descriptions are well-formed and valid.
33433 However, to help people unfamiliar with XML write descriptions for
33434 their targets, we also describe the grammar here.
33436 Target descriptions can identify the architecture of the remote target
33437 and (for some architectures) provide information about custom register
33438 sets. They can also identify the OS ABI of the remote target.
33439 @value{GDBN} can use this information to autoconfigure for your
33440 target, or to warn you if you connect to an unsupported target.
33442 Here is a simple target description:
33445 <target version="1.0">
33446 <architecture>i386:x86-64</architecture>
33451 This minimal description only says that the target uses
33452 the x86-64 architecture.
33454 A target description has the following overall form, with [ ] marking
33455 optional elements and @dots{} marking repeatable elements. The elements
33456 are explained further below.
33459 <?xml version="1.0"?>
33460 <!DOCTYPE target SYSTEM "gdb-target.dtd">
33461 <target version="1.0">
33462 @r{[}@var{architecture}@r{]}
33463 @r{[}@var{osabi}@r{]}
33464 @r{[}@var{compatible}@r{]}
33465 @r{[}@var{feature}@dots{}@r{]}
33470 The description is generally insensitive to whitespace and line
33471 breaks, under the usual common-sense rules. The XML version
33472 declaration and document type declaration can generally be omitted
33473 (@value{GDBN} does not require them), but specifying them may be
33474 useful for XML validation tools. The @samp{version} attribute for
33475 @samp{<target>} may also be omitted, but we recommend
33476 including it; if future versions of @value{GDBN} use an incompatible
33477 revision of @file{gdb-target.dtd}, they will detect and report
33478 the version mismatch.
33480 @subsection Inclusion
33481 @cindex target descriptions, inclusion
33484 @cindex <xi:include>
33487 It can sometimes be valuable to split a target description up into
33488 several different annexes, either for organizational purposes, or to
33489 share files between different possible target descriptions. You can
33490 divide a description into multiple files by replacing any element of
33491 the target description with an inclusion directive of the form:
33494 <xi:include href="@var{document}"/>
33498 When @value{GDBN} encounters an element of this form, it will retrieve
33499 the named XML @var{document}, and replace the inclusion directive with
33500 the contents of that document. If the current description was read
33501 using @samp{qXfer}, then so will be the included document;
33502 @var{document} will be interpreted as the name of an annex. If the
33503 current description was read from a file, @value{GDBN} will look for
33504 @var{document} as a file in the same directory where it found the
33505 original description.
33507 @subsection Architecture
33508 @cindex <architecture>
33510 An @samp{<architecture>} element has this form:
33513 <architecture>@var{arch}</architecture>
33516 @var{arch} is one of the architectures from the set accepted by
33517 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
33520 @cindex @code{<osabi>}
33522 This optional field was introduced in @value{GDBN} version 7.0.
33523 Previous versions of @value{GDBN} ignore it.
33525 An @samp{<osabi>} element has this form:
33528 <osabi>@var{abi-name}</osabi>
33531 @var{abi-name} is an OS ABI name from the same selection accepted by
33532 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
33534 @subsection Compatible Architecture
33535 @cindex @code{<compatible>}
33537 This optional field was introduced in @value{GDBN} version 7.0.
33538 Previous versions of @value{GDBN} ignore it.
33540 A @samp{<compatible>} element has this form:
33543 <compatible>@var{arch}</compatible>
33546 @var{arch} is one of the architectures from the set accepted by
33547 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
33549 A @samp{<compatible>} element is used to specify that the target
33550 is able to run binaries in some other than the main target architecture
33551 given by the @samp{<architecture>} element. For example, on the
33552 Cell Broadband Engine, the main architecture is @code{powerpc:common}
33553 or @code{powerpc:common64}, but the system is able to run binaries
33554 in the @code{spu} architecture as well. The way to describe this
33555 capability with @samp{<compatible>} is as follows:
33558 <architecture>powerpc:common</architecture>
33559 <compatible>spu</compatible>
33562 @subsection Features
33565 Each @samp{<feature>} describes some logical portion of the target
33566 system. Features are currently used to describe available CPU
33567 registers and the types of their contents. A @samp{<feature>} element
33571 <feature name="@var{name}">
33572 @r{[}@var{type}@dots{}@r{]}
33578 Each feature's name should be unique within the description. The name
33579 of a feature does not matter unless @value{GDBN} has some special
33580 knowledge of the contents of that feature; if it does, the feature
33581 should have its standard name. @xref{Standard Target Features}.
33585 Any register's value is a collection of bits which @value{GDBN} must
33586 interpret. The default interpretation is a two's complement integer,
33587 but other types can be requested by name in the register description.
33588 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
33589 Target Types}), and the description can define additional composite types.
33591 Each type element must have an @samp{id} attribute, which gives
33592 a unique (within the containing @samp{<feature>}) name to the type.
33593 Types must be defined before they are used.
33596 Some targets offer vector registers, which can be treated as arrays
33597 of scalar elements. These types are written as @samp{<vector>} elements,
33598 specifying the array element type, @var{type}, and the number of elements,
33602 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
33606 If a register's value is usefully viewed in multiple ways, define it
33607 with a union type containing the useful representations. The
33608 @samp{<union>} element contains one or more @samp{<field>} elements,
33609 each of which has a @var{name} and a @var{type}:
33612 <union id="@var{id}">
33613 <field name="@var{name}" type="@var{type}"/>
33619 If a register's value is composed from several separate values, define
33620 it with a structure type. There are two forms of the @samp{<struct>}
33621 element; a @samp{<struct>} element must either contain only bitfields
33622 or contain no bitfields. If the structure contains only bitfields,
33623 its total size in bytes must be specified, each bitfield must have an
33624 explicit start and end, and bitfields are automatically assigned an
33625 integer type. The field's @var{start} should be less than or
33626 equal to its @var{end}, and zero represents the least significant bit.
33629 <struct id="@var{id}" size="@var{size}">
33630 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
33635 If the structure contains no bitfields, then each field has an
33636 explicit type, and no implicit padding is added.
33639 <struct id="@var{id}">
33640 <field name="@var{name}" type="@var{type}"/>
33646 If a register's value is a series of single-bit flags, define it with
33647 a flags type. The @samp{<flags>} element has an explicit @var{size}
33648 and contains one or more @samp{<field>} elements. Each field has a
33649 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
33653 <flags id="@var{id}" size="@var{size}">
33654 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
33659 @subsection Registers
33662 Each register is represented as an element with this form:
33665 <reg name="@var{name}"
33666 bitsize="@var{size}"
33667 @r{[}regnum="@var{num}"@r{]}
33668 @r{[}save-restore="@var{save-restore}"@r{]}
33669 @r{[}type="@var{type}"@r{]}
33670 @r{[}group="@var{group}"@r{]}/>
33674 The components are as follows:
33679 The register's name; it must be unique within the target description.
33682 The register's size, in bits.
33685 The register's number. If omitted, a register's number is one greater
33686 than that of the previous register (either in the current feature or in
33687 a preceeding feature); the first register in the target description
33688 defaults to zero. This register number is used to read or write
33689 the register; e.g.@: it is used in the remote @code{p} and @code{P}
33690 packets, and registers appear in the @code{g} and @code{G} packets
33691 in order of increasing register number.
33694 Whether the register should be preserved across inferior function
33695 calls; this must be either @code{yes} or @code{no}. The default is
33696 @code{yes}, which is appropriate for most registers except for
33697 some system control registers; this is not related to the target's
33701 The type of the register. @var{type} may be a predefined type, a type
33702 defined in the current feature, or one of the special types @code{int}
33703 and @code{float}. @code{int} is an integer type of the correct size
33704 for @var{bitsize}, and @code{float} is a floating point type (in the
33705 architecture's normal floating point format) of the correct size for
33706 @var{bitsize}. The default is @code{int}.
33709 The register group to which this register belongs. @var{group} must
33710 be either @code{general}, @code{float}, or @code{vector}. If no
33711 @var{group} is specified, @value{GDBN} will not display the register
33712 in @code{info registers}.
33716 @node Predefined Target Types
33717 @section Predefined Target Types
33718 @cindex target descriptions, predefined types
33720 Type definitions in the self-description can build up composite types
33721 from basic building blocks, but can not define fundamental types. Instead,
33722 standard identifiers are provided by @value{GDBN} for the fundamental
33723 types. The currently supported types are:
33732 Signed integer types holding the specified number of bits.
33739 Unsigned integer types holding the specified number of bits.
33743 Pointers to unspecified code and data. The program counter and
33744 any dedicated return address register may be marked as code
33745 pointers; printing a code pointer converts it into a symbolic
33746 address. The stack pointer and any dedicated address registers
33747 may be marked as data pointers.
33750 Single precision IEEE floating point.
33753 Double precision IEEE floating point.
33756 The 12-byte extended precision format used by ARM FPA registers.
33759 The 10-byte extended precision format used by x87 registers.
33762 32bit @sc{eflags} register used by x86.
33765 32bit @sc{mxcsr} register used by x86.
33769 @node Standard Target Features
33770 @section Standard Target Features
33771 @cindex target descriptions, standard features
33773 A target description must contain either no registers or all the
33774 target's registers. If the description contains no registers, then
33775 @value{GDBN} will assume a default register layout, selected based on
33776 the architecture. If the description contains any registers, the
33777 default layout will not be used; the standard registers must be
33778 described in the target description, in such a way that @value{GDBN}
33779 can recognize them.
33781 This is accomplished by giving specific names to feature elements
33782 which contain standard registers. @value{GDBN} will look for features
33783 with those names and verify that they contain the expected registers;
33784 if any known feature is missing required registers, or if any required
33785 feature is missing, @value{GDBN} will reject the target
33786 description. You can add additional registers to any of the
33787 standard features --- @value{GDBN} will display them just as if
33788 they were added to an unrecognized feature.
33790 This section lists the known features and their expected contents.
33791 Sample XML documents for these features are included in the
33792 @value{GDBN} source tree, in the directory @file{gdb/features}.
33794 Names recognized by @value{GDBN} should include the name of the
33795 company or organization which selected the name, and the overall
33796 architecture to which the feature applies; so e.g.@: the feature
33797 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
33799 The names of registers are not case sensitive for the purpose
33800 of recognizing standard features, but @value{GDBN} will only display
33801 registers using the capitalization used in the description.
33808 * PowerPC Features::
33813 @subsection ARM Features
33814 @cindex target descriptions, ARM features
33816 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
33817 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
33818 @samp{lr}, @samp{pc}, and @samp{cpsr}.
33820 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
33821 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
33823 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
33824 it should contain at least registers @samp{wR0} through @samp{wR15} and
33825 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
33826 @samp{wCSSF}, and @samp{wCASF} registers are optional.
33828 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
33829 should contain at least registers @samp{d0} through @samp{d15}. If
33830 they are present, @samp{d16} through @samp{d31} should also be included.
33831 @value{GDBN} will synthesize the single-precision registers from
33832 halves of the double-precision registers.
33834 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
33835 need to contain registers; it instructs @value{GDBN} to display the
33836 VFP double-precision registers as vectors and to synthesize the
33837 quad-precision registers from pairs of double-precision registers.
33838 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
33839 be present and include 32 double-precision registers.
33841 @node i386 Features
33842 @subsection i386 Features
33843 @cindex target descriptions, i386 features
33845 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
33846 targets. It should describe the following registers:
33850 @samp{eax} through @samp{edi} plus @samp{eip} for i386
33852 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
33854 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
33855 @samp{fs}, @samp{gs}
33857 @samp{st0} through @samp{st7}
33859 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
33860 @samp{foseg}, @samp{fooff} and @samp{fop}
33863 The register sets may be different, depending on the target.
33865 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
33866 describe registers:
33870 @samp{xmm0} through @samp{xmm7} for i386
33872 @samp{xmm0} through @samp{xmm15} for amd64
33877 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
33878 @samp{org.gnu.gdb.i386.sse} feature. It should
33879 describe the upper 128 bits of @sc{ymm} registers:
33883 @samp{ymm0h} through @samp{ymm7h} for i386
33885 @samp{ymm0h} through @samp{ymm15h} for amd64
33889 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
33890 describe a single register, @samp{orig_eax}.
33892 @node MIPS Features
33893 @subsection MIPS Features
33894 @cindex target descriptions, MIPS features
33896 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
33897 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
33898 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
33901 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
33902 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
33903 registers. They may be 32-bit or 64-bit depending on the target.
33905 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
33906 it may be optional in a future version of @value{GDBN}. It should
33907 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
33908 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
33910 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
33911 contain a single register, @samp{restart}, which is used by the
33912 Linux kernel to control restartable syscalls.
33914 @node M68K Features
33915 @subsection M68K Features
33916 @cindex target descriptions, M68K features
33919 @item @samp{org.gnu.gdb.m68k.core}
33920 @itemx @samp{org.gnu.gdb.coldfire.core}
33921 @itemx @samp{org.gnu.gdb.fido.core}
33922 One of those features must be always present.
33923 The feature that is present determines which flavor of m68k is
33924 used. The feature that is present should contain registers
33925 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
33926 @samp{sp}, @samp{ps} and @samp{pc}.
33928 @item @samp{org.gnu.gdb.coldfire.fp}
33929 This feature is optional. If present, it should contain registers
33930 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
33934 @node PowerPC Features
33935 @subsection PowerPC Features
33936 @cindex target descriptions, PowerPC features
33938 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
33939 targets. It should contain registers @samp{r0} through @samp{r31},
33940 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
33941 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
33943 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
33944 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
33946 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
33947 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
33950 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
33951 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
33952 will combine these registers with the floating point registers
33953 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
33954 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
33955 through @samp{vs63}, the set of vector registers for POWER7.
33957 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
33958 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
33959 @samp{spefscr}. SPE targets should provide 32-bit registers in
33960 @samp{org.gnu.gdb.power.core} and provide the upper halves in
33961 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
33962 these to present registers @samp{ev0} through @samp{ev31} to the
33965 @node Operating System Information
33966 @appendix Operating System Information
33967 @cindex operating system information
33973 Users of @value{GDBN} often wish to obtain information about the state of
33974 the operating system running on the target---for example the list of
33975 processes, or the list of open files. This section describes the
33976 mechanism that makes it possible. This mechanism is similar to the
33977 target features mechanism (@pxref{Target Descriptions}), but focuses
33978 on a different aspect of target.
33980 Operating system information is retrived from the target via the
33981 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
33982 read}). The object name in the request should be @samp{osdata}, and
33983 the @var{annex} identifies the data to be fetched.
33986 @appendixsection Process list
33987 @cindex operating system information, process list
33989 When requesting the process list, the @var{annex} field in the
33990 @samp{qXfer} request should be @samp{processes}. The returned data is
33991 an XML document. The formal syntax of this document is defined in
33992 @file{gdb/features/osdata.dtd}.
33994 An example document is:
33997 <?xml version="1.0"?>
33998 <!DOCTYPE target SYSTEM "osdata.dtd">
33999 <osdata type="processes">
34001 <column name="pid">1</column>
34002 <column name="user">root</column>
34003 <column name="command">/sbin/init</column>
34004 <column name="cores">1,2,3</column>
34009 Each item should include a column whose name is @samp{pid}. The value
34010 of that column should identify the process on the target. The
34011 @samp{user} and @samp{command} columns are optional, and will be
34012 displayed by @value{GDBN}. The @samp{cores} column, if present,
34013 should contain a comma-separated list of cores that this process
34014 is running on. Target may provide additional columns,
34015 which @value{GDBN} currently ignores.
34029 % I think something like @colophon should be in texinfo. In the
34031 \long\def\colophon{\hbox to0pt{}\vfill
34032 \centerline{The body of this manual is set in}
34033 \centerline{\fontname\tenrm,}
34034 \centerline{with headings in {\bf\fontname\tenbf}}
34035 \centerline{and examples in {\tt\fontname\tentt}.}
34036 \centerline{{\it\fontname\tenit\/},}
34037 \centerline{{\bf\fontname\tenbf}, and}
34038 \centerline{{\sl\fontname\tensl\/}}
34039 \centerline{are used for emphasis.}\vfill}
34041 % Blame: doc@cygnus.com, 1991.